NBSIR 78-1542

State-of-the-Art Study of Heat

Exchangers Used With Solar

Assisted Domestic Hot Water

Systems

(Potential Contamination of

Stable Water Supply)

F. Eugene Metz

Mary Jane Orloski

Building Economics and Regulatory Technology Division

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D C. 20234

July 1978

Prepared for Office of the Assistant Secretary

Conservation and Solar Applications

Department of Energy

Washington, D.C. 20545

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NBSIR 78-1542

t STATE-OF-THE-ART STUDY OF HEAT

EXCHANGERS USED WITH SOLAR

ASSISTED DOMESTIC HOT WATER

SYSTEiViS

(POTENTIAL CONTAMINATION OF

POTABLE WATER SUPPLY)

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F. Eugene Metz

Mary Jane Orloski

Building Economics and Regulatory Technology Division

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D.C. 20234

July 1978

Prepared for Office of the Assistant Secretary

Conservation and Solar Applications

Department of Energy

Washington, D.C. 20545

U.S. DEPARTMENT ©F COMMERCE. JysReta M. Kreps, Secretary

Dr. NsrmiR, Undm §@@misirf

Jordan J. iaryelii, Smir&ianf Ssimca aetd Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
PREFACE

In discussing the state of the art of solar system heat exchangers, certain

commercial and proposed products are identified and judgments inferred in order

to provide a descriptive characterization of their features. Inclusion of a given product in no case implies a recommendation or endorsement by the National

Bureau of Standards, and the presentation should not be construed as a certification that any product would provide the indicated performance. Similarly, the

omission of a product does not imply that its capabilities are less than those

of the included products. Many diverse heat transfer processes and safety

standards are discussed but there is no intent to advocate or censure these

practices.
ACKNOWLEDGMENTS

The authors wish to express appreciation to the following individuals for

their help, advice and encouragement in the preparation of this publication

Carl W. Conner, U.S. Department of Energy

Robert D. Dikkers, National Bureau of Standards

William Freeborne, U.S. Department of Housing and Urban Development

Robert Sparkes, Dubin-Bloome Associates

David Waksman, National Bureau of Standards

Michael E. McCabe, National Bureau of Standards

James H. Pielert, National Bureau of Standards

State-of-the-Art Study of Heat Exchangers

Used With Solar Assisted Domestic Hot Water Systems

(Potential Contamination of Potable Water Supply)

PAGE

1.0 INTRODUCTION 1

1.1 Criteria for Solar Demonstration Programs 1 1.2 Potential Hazards 1 1.3 Double Failure Concept 5

2.0 HEAT TRANSFER FLUIDS 6

2.1 Characteristics of Fluids used in the Demonstration Programs 6

2.2 Toxicity of Heat Transfer Fluids 11

2.3 Contamination Hazards 15

2.4 Selection of Heat Transfer Fluids 17

3.0 HEAT EXCHANGERS 17

3.1 Causes of Failure 17

3.2 Discussion of Generic Heat Exchanger Types 19

3.3 Availability of Heat Exchangers for Solar 27

3.4 Heat Exchanger Selection 28

4.0 RELATED APPLICATIONS 29

4.1 Heat Exchangers Used in Food Processing 29

4.2 Heat Exchangers Used in Food and Beverage Dispensing 30

5.0 EXISTING CODES AND STANDARDS 32

5.1 Codes and Standards for Solar Hot Water Systems 32

5.2 Related Codes and Standards...,. 34

5.3 Current Activity and Research 38

5.4 Need for Safety Guidelines 40

6.0 SUMMARY AND RECOMMENDATIONS 40

REFERENCES 44

APPENDIX A - Illustrations of Heat Exchanger Types A-1

APPENDIX B - Toxicity Studies of Heat Transfer Fluids and

Common Additives B-1

APPENDIX C - Refrigerating Systems Classification by Types C-1
ABSTRACT

This report presents the results of a non quantitative state-of-the-art study

of heat exchangers used with solar assisted domestic hot water systems where

a heat exchange Interface exists between the potable water supply and a heat

transfer fluid. Emphasis is placed on the potential for contaminating the potable

water supply if failures should occur. The study considers (1) characteristics

of various heat exchanger types and their relative safety; (2) characteristics

of heat exchanger fluids (toxicity, corrosivity, thermal properties, etc.);

(3) regulatory considerations; and (4) designs of similar systems with potential

for contamination.

Key Words: contamination; corrosion; heat exchanger; heat transfer fluids;

potable water; solar energy; standards; toxicity.

ii
1. INTRODUCTION

1.1 CRITERIA FOR SOLAR DEMONSTRATION PROGRAMS

The Solar Heating and Cooling Demonstration Act of 1974 (PL 93-409), provides

for a "demonstration within a three-year period of the practical use of solar

heating technology, and for the development and demonstration within a five-year

period of the practical use of combined heating and cooling technology." The

Act called for the development of performance criteria to assure safe, reliable

and efficient solar equipment to further public acceptance of solar heating and

cooling systems.

The development of "interim performance criteria" within 120 days after enactment

was called for by PL 93-409. These criteria were developed by the National

Bureau of Standards (NBS) and published for residential application by the Department of Housing and Urban Development (HUD) under the title "Interim Performance

Criteria for Solar Heating and Combined Heating and Cooling Systems for Dwellings",

January 1975

[1]*

*.

Subsequent publications include: "Interim Performance Criteria for Solar Heating

and Cooling Systems in Commercial Buildings" (IPC)[2] prepared for the Energy

Research and Development Administration (ERDA)^ by NBS, and "Intermediate Minimum

Property Standards Supplement - Solar Heating and Domestic Hot Water Systems"

(S/MPS)[3] prepared for HUD by NBS.

"The overall philosophy of the S/MPS and IPC documents with regard to

safety is to prevent the creation of a hazard due to the presence

of solar equipment, which is greater than that which would be found in

a non-solar building" [4]

1.2 POTENTIAL HAZARDS

There are potential safety problems involved in the transfer of heat energy

from solar collectors to potable hot water supplies used for bathing, washing

and food preparation. These potential problems are both chemical and mechanical in nature and apply primarily to liquid transfer and storage systems where

a heat exchange interface exists with the potable water supply. Both the

chemical composition of heat transfer fluids (e.g., their pH, toxicity and

chemical durability) and the mechanical reliability of various system components, i.e., heat exchangers and back flow devices, are of concern.

Except in most unusual cases, it is appropriate to consider the energy transport fluid as non-potable and having the potential for contaminating potable

water during the heat transfer process. Even potable or "non-toxic" fluids,

in closed systems, are likely to become non-potable due to contamination from

metal tubes, solder joints, packing, etc., or by inadvertent installation of

a toxic fluid at a later date. The growth of bacteria and fungi within the

solid storage of air systems also represents a potential hazard.

^ Now Department of Energy

* Numbers in brackets represent references given on page 44.

1
The extent of non-po table characteristics or the degree of toxicity of the

transport medium may range from unknown or slight to extreme. The reader is

referred to the following publications for detailed information relative to

toxicity, [5, 6, 7, 8]

Some of the common sources of contamination within the transfer medium are as follows

o antifreeze additives such as ethylene glycol

o chemical inhibiters to retard corrosion, scaling, etc,

o chemical additives to neutralize decomposition products formed in the

fluid over time (e.g., by thermal degradation)

o impurities from the tubes, containers, joints and fabrication compounds,

or even outgasslng products from various components

o the possibility of dust, bacteria, fungi etc,, as may be the case in

air storage systems

o decomposition products formed in the transfer medium

Heat transfer to potable water requires an interface with the collector heat

transfer fluids. During this process contaminants may enter the potable water

supply, because of certain failures within the components. These failures may

be individual or in combination and may be brought about by the following:

o faulty fabrication resulting in such flaws as open seams

o faulty Installation or damage

o thermal shock (including expansion and contraction)

o mechanical stresses such as overpressure and water hammer

o erosion and/or corrosion (especially pitting)

o significant drop in pressure of water supply where such pressure is

intended as a primary means of protection against contamination

In order to prejsent a hazard, such failures must occur of course within a context leading to a mixing of the contaminant with the potable water. This

occurrence may be Immediate, i.e., if there is a leak in a single wall heat

exchanger which is immersed within the potable water, or gradual, i.e., a leak into an intermediate fluid or from an external jacket. Increasing the

thickness of a single wall tube may be of little advantage in preventing leaks

when pitting occurs, but rather only delays the results.

Similarly in double wall devices in which the walls are in intimate contact,

corrosion of one may continue in a straight line path and corrode through the

adjacent wall. This is based on the strong chance that a corrosive pit in

one wall will be self sustaining beyond the elimination of the Initial impurity, Oxygen depletion within the pit results in favorable conditions for the

development of a galvanic cell between the pit and the heat transfer fluid

thereby sustaining a corrosive action which will continue through an adjacent

wall in direct contact or until a source of oxygen is contacted.

The high potential of this occurrence requires that the double walls be separated in order to interrupt this continuous action. This separation may be

accomplished by an air space or by an intervening material which will act to

stop the corrosion. It is desirable that the separation also aid in the

2
detection of the leaks by providing a path or other means of exposing the

leaking fluid to routine observation.

Some of the materials that may be used as intermediate layers are:

o solder or brazing

o a "noble" metal

o a potable fluid

o conducting fins, etc.

o conductive adhesive

The layer, to be effective, should stop corrosion due to pitting.

In double wall heat exchangers, failures must occur in two components which

are adjacent or into an intermediate medium and then into the potable water as

a result of a second failure. Again, contamination of the potable water may

be dependent upon a leak as well as pressure differential resulting in flow

from the transfer medium to the potable water.

The techniques employed in safeguarding against the contamination of potable

water in the heat exchanger process tend to follow this general sequence:

o avoidance of non-potable heat transfer media

o creating increasing degrees of physical separation between the heat

transfer medium and the potable water supply

o visual detection of leaks or contamination

o electronic sensing of leaks

o safety switching, activated by pressure sensors (or contamination

sensors)

The S/MPS and IPC documents do not present standards to determine the degree

of toxicity presented by various liquids. They are primarily concerned with

the provision of adequate protection when potentially hazardous substances

are used.

The following provision taken from the S/MPS (similar to 4.6.2 of the IPC)

addresses the issue of the protection of potable water and provides this criterion for the heat exchange interface that may exist between a non-potable

liquid and potable water.

(S-515-9 . 1

)

When non-potable liquid is used in a solar energy system

to transfer heat to domestic (potable) hot water, the design of the

heat exchanger shall be such that either a minimum of two walls or interfaces are maintained between the non-potable liquid and the potable

water supply or protection is provided in such a manner that equivalent

safety is provided.

Commentary: Double wall heat exchanger designs are one way of meeting

the intent of this criterion. When double wall heat exchanger designs

consisting of two single wall heat exchangers in combination with an intermediary potable heat transfer liquid are used, leakage through

one of the walls would result in a single wall configuration. Although

3
this design is considered to meet the Intent of this criterion, there

are several other designs that avoid this problem.

The use of single wall configurations which solely rely upon potable

water pressure to prevent contamination is not considered to be an

acceptable solution. Similarly, extra thick single walls are not

considered to meet the intent of this criterion. For approval of other

than double wall designs, the procedures described in S-101 should be

utilized.

Application of this criterion has caused confusion and concern among various

segments of the solar industry, building code officials, and evaluators of

solar demonstration systems. These concerns include:

A. Definition of non-potable liquids

B. Definition of equivalent safety

C. Interpretation of criteria to require "double wall" heat exchangers

which are allegedly more costly and less thermally efficient than

equivalent "single wall" heat exchangers

D. Relationship of heat transfer fluid characteristics (chemical characteristics, thermal properties, stability, hydraulic properties, etc.)

to safety of solar systems and service life expectancy of the systems

E. Inadvertent use of toxic transfer liquids in systems not designed to

provide an adequate level of protection

The preceeding provision is concerned with the safety of the building occupants

due to a failure of a heat exchanger leading to contamination of their domestic

hot water (DHW) system in addition to protection of the system supplying water

to the building. A complementary provision extends this concern to the potable

water supply itself and to the safety of those beyond the immediate occupants.

Pollution of the potable water supply can occur by way of backflow^ caused by

back pressure and/or back-siphonage within a cross connection^ between the

potable fluid in the system. Back pressure may occur with elevated tanks or pumps and back-siphonage can occur when the potable water supply system is under vacuum such as might occur with a broken street water main.

Provision S-61 5-1 0.1,3 of the S/MPS supplement provides for backflow prevention.

Backflow of nonpotable heat transfer fluids into the

potable water system shall be prevented in a manner

approved by the local administrative code authority.

^ BACKFLOW . The flow of water or other liquids, mixtures, or substances into the

distributing pipes of a potable supply of water from any source other than its

intended source, Back-siphonage is one type of backflow. [9]

O CROSS CONNECTION . A cross connection is any physical connection or arrangement

between two otherwise separate piping systems, one of which contains potable water

and the other of unknown or questionable safety, whereby water may flow from one system to the other, the direction of flow depending on the pressure differential

between the two systems. [9]

4
Commentary: The use of air gaps and/or mechanical backflow preventers are two possible solutions to this problem.

The following are some recognized standards that may be

acceptable to the local administrative code authority:

Air Gaps -ANSI-Al 12. 1.

Backflow preventers -FCCCHR Chapter 10

lAPMO PS 31-74

AWWA C506-69

A.S.S.E. 1011

A.S.S.E. 1012

A.S.S.E. 1013

A.S.S.E. 1015

A.S.S.E. 1020

ANSI-All 2. 1.1

With the passage of the Safe Drinking Water Act of 1974 [10] and subsequent

Environmental Protection Agency (EPA) promulgations establishing maximum con- taminant level in the National Interim Primary Drinking Water Regulations [11,

12], new emphasis has been placed on controlling possible cross-connections

that might result in contamination of the potable water supply. If a failure

should occur along the common wall of a single-wall heat exchanger, there is

then a cross-connection between the potable water and the non-potable heat

transfer fluid.

The environmental impact of disposing of large quantities of non-potable heat

transfer fluids while outside the scope of this report must be recognized as

a long-range problem accompanying the increasing shift to solar heating and

cooling (SHAC) systems.

This report is concerned primarily with the potential hazards of heat exchanger

failure

1.3 DOUBLE FAILURE CONCEPT

Growing out of the S/MPS provision. . .a minimum of two walls or Interfaces are maintained between the non-potable liquid and the potable water... or equivalent

safety is provided, is the concept of "double failure" or "double protection."

The rationale is that failure of a single component should not result in contamination. With the use of hazardous liquids this implies the use of heat

exchanger designs necessitating the independent failure of two components before

the potable water is contaminated. The chance of an independent failure of a second component so compounds the risk probabilities that contamination is seen

as remote. This raises the issue of detection of the initial failure or leak.

The "double failure" concept suggests that means other than physical separation

might be utilized to provide equal reliability. This provides for flexibility

and increased alternatives for reducing the risk without sacrificing thermal

efficiency that often occurs with double wall separation.

Double wall heat exchangers are one way of meeting the intent of the criterion

and efforts are being made to develop Innovative and cost effective designs.

Many of these designs are discussed in Section 3.2, Analysis of Generic Heat

5
Exchanger Types. Efforts are also being made to provide leak and/or contamination detection.

Trade-offs between thermal efficiency, cost effectiveness, and risk for both

heat exchangers and heat transfer fluids may be necessary to provide acceptable

safety. It is the combination of fluid toxicity and heat exchanger reliability

that determines the level of hazard,

2.0 HEAT TRANSFER FLUIDS

2.1 CHARACTERISTICS OF FLUIDS USED IN THE DEMONSTRATION PROGRAMS

The cause of concern for heat exchangers ultimately involves the non-potable

characteristics of the heat transfer fluids used in many solar energy systems

and an appraisal of the contamination risk to the domestic hot water supply

if a leak should occur. The degree of contamination and severity of the danger

would be determined by the volume flow of fluid leakage and volume of potable

water as well as the toxicity of the fluid composition.

It was mentioned in the introduction that protection against damage by freezing

and corrosion results in the use of non-potable heat transfer fluids in many

solar heating and cooling systems. Water is the most thermally efficient heat

transfer fluid (HTF) but freeze protectants such as the glycols are added to

the water (or used to replace it) in many freeze prone areas and corrosion

inhibitors such as phosphates and nitrates are commonly used. This is similar

to use of coolants in automotive engines.

It is generally thought that the glycols account for about 70% of the antifreeze

fluids currently used in solar energy systems, with glycerin and silicone oils

about 10%, and manufacturers* brands of unknown or proprietary mixtures the

remaining 20%, There is some confirmation of this by the HUD Residential Demonstration Project description data made available to NBS to date. This data further

reveals that there is roughly equal use of ethylene glycol and propylene glycol.

Although the information is limited, there is evidence that about half of the

demonstration projects using liquid type collectors use water without additives

and a small percentage use water with additives such as corrosion inhibitors.

This suggests that more than half of the liquid systems are drain down or drain

back and therefore do not use antifreeze solutions.

The toxicity of a limited number of pertinent heat transfer fluids and additives are discussed here. A more complete analysis can be found in the Appendix

and in referenced documents. Tables 1, 2, 3 and 4 give characteristics, properties and general comparisons of some commonly used heat transfer fluids.

6
TABLE 1 CHARACTERISTICS OF HEAT TRANSFER FLUID (Relative to Water)

FLUID CHARACTERISTICS POTENTIAL EFFECT ON SOLAR SYSTEM

1. Toxici ty Potential health hazard

2. Higher viscosity May require greater pumping power and

larger pipes to circulate a given volume

of a thicker fluid

3. Low Specific Heat Necessary to circulate more fluid (volume)

to transfer a given amount of heat

4. Flash point may be reached

under worst case "no-flow"

(stagnation) collector con- dition

Possible fire hazard

5. Relatively Shorter fluid life

(before degrading or decomposing)

System owner must monitor, replace, or dispose of fluid periodically or risk

system damage

6. Cost and Availability Owner may replace heat transfer fluid with

one that is not compatible with the system

7. Poorer oxidative stability Oxidized (degrades) at low temperatures;

may be accelerated by presence of certain

metals

8. Poorer thermal stability Decomposes at higher temperatures into

a fluid that accelerates corrosion and

may also be more toxic

9. Inhibitor-selection not

optimal

May cause premature scaling or corrosion

7
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TABLE 3 - GENERAL COMPARISON OF TYPICAL

HEAT EXCHANGER FLUIDS*

Fluid Advantages Disadvantages

Water, untreated 1 . nontoxic 1 . freezes at 32°F

2 . environmentally safe 2 . supports galvanic corrosion

• 3. inexpensive 3. bolls at 212°F

4. high thermal efficiency 4. promotes scale formation

5. may change composition in closed

system

Water/glycol

mixtures

1 , will not freeze down to 1 . -35°F

2 , inhibitor technology

for ethylene glycol 2 , well-suited to offering

protection in a multi- 3 , metal system

3, boils at temperatures 4 , higher than water 5 ,

fluid must be replaced frequently or maintained properly

(by monitoring ph)

problem of disposal of large

amounts

decomposes around 280-300°F

forming sludge and organic acids

toxic (ethylene glycol)

can degrade building material

(roofs)

Hydrocarbons 1. low cost 1. poor oxidation stability

2. nonvolatile 2. poor thermal stability at

3. less toxic than

ethylene glycol

high temperatures resulting

in sludge and acid formation

3, high viscosity at low temperatures

4, environmental effects similar to

motor oil

5, typical closed-cup flashpoints run 300-320“F, fluids with

higher flashpoints have a higher viscosity

6 , damage to building from leakage

may be irreparable due to odor

and low volatility

7, low heat conductivity

Silicones 1 . do not freeze l,

2 . do not boil 2 , 3. do not corrode 3 , common metals 4 , 4. long life 5 , 5. high flashpoint 6 . 6 . low toxicity, if any 7 ,

low heat capacity

high viscosity

expensive

not biodegradable

difficult to seal

strong tendency to leak

may require more expensive

pump (may also be true for hydrocarbons)

*Based on mfr, claims

Not an NBS endorsement

9
Some commonly used heat transfer fluids are better known by their trade names

than for their principal chemical ingredients. The following table lists some

of these fluids and their principle ingredients.

TABLE 4 - SOLAR HEAT TRANSFER FLUIDS

Trade Name

*UCAR-17

*DOWTHERM SR-1

UCON-500

*UCON-30

*DOWFROST

*UCAR-35

MOBILTHERM 603

MOBILTHERM LIGHT

SUNTEMP 1

CALORIA HT-43

THERMIA 33

PROCESS OIL-3029

*D0W CORNING 200

SF 96

*THERMIN0L 66

*D0WTHERM A

SOLARGARD G

Manufacturer

Union Carbide

Dow Chemical

Union Carbide

Union Carbide

Dow Chemical

Union Carbide

Mobil Oil

Mobil Oil

Resource Technology Corp.

Exxon

Shell

Exxon

Dow Corning

General Electric

Monsanto

Dow Corning

Daystar

Composition^

Ethylene glycol

Ethylene glycol inhibitor < 5%

and red dye < 1%

Polyglycols - may contain

phenyl g naphthyl amine < 10%

Ethylene oxide

Propylene glycol - contains

inhibitor

Propylene glycol

Paraffinic, neutral oil

Paraffinic, high aromatic oil

Paraffinic, low aromatic oil

contains red dye (< 1%)

Paraffinic, low (14%)

aromatic oil

Paraffinic oil - aromatic

content 20-25%

Naphthenic mineral oil

aromatic content < 10%

Silicone oil

Po 1yd ime thyl s il oxan

Terphenyl mixture

Diphenyl and diphenyl oxide

mixture

Glycerol (USP) 60%/water 40%

^Data provided by Sandia report [13] or manufacturers; materials obtained from Sandia

Laboratories

*Toxicity information on these products are included in Appendix B (Gosselin et al)[6]

10
2.2 TOXICITY OF HEAT TRANSFER MEDIA

Much of the following information is taken from "Clinical Toxicology of

Commercial Products" [6] and from draft reports of work presently underway

at Sandia Laboratories [13] and Energy and Environmental Analysis, Inc, [14],

As an aid to the understanding of this material the following definitions

and explanations are offered:

o Toxic dose defines the amount of a chemical required to produce some harm in an animal, and is usually given in units of mg /kg [milligrams

(mg) of the substance administered per kilogram (kg) of subject's

body weight]

o LD^q - a statistically obtained virtual value which represents the

best estimation of the dose required to produce death in 50 percent

of a statistically defined (significant) population of test animals

o - the lowest lethal dose (given over any period of time) reported

For the toxicity ratings of Gosselin et al, [6] Table 1 and Appendix B, the

following explanations are noted.

(1) The rating is based on mortality, not morbidity, i.e,, it is really

a lethality rating. In general a clinically significant illness

may be expected after doses of about one-tenth the probable lethal.

(2) Unless otherwise noted, each rating is based on the acute toxicity

of a single dose when taken by mouth or gavage.

(3) The toxicity rating reflects an estimate of the probable or mean

lethal dose, not the minimal fatal dose, (Suggested in Gosselin

et al, that minimal lethal doses recorded in the clinical literature

are usually lower than those implied by current ratings.)

(4) Implicit in the use of data based on laboratory animals is the

conventional assumption that the mean lethal dose in man lies

in the same class as does the LDcq for test animals. (Suggested

in Gosselin et al, that the glycols may be even more hazardous to

man than to test animals).

(5) For patients who are heavier or lighter, (than the reference 150

lbs adult) probable lethal doses are proportionally larger or smaller and can be readily estimated from the values of mg/kg

recorded in the table,

(6) Information in Gosselin et al includes toxicity ratings for

complete commercial products as marketed, as well as for single

substances (usually technical grade).

Glycols applicable to solar use include ethylene glycol, propylene glycol and

perhaps dipropylene glycol. Aqueous solutions of 50 percent (by weight) and

greater of both ethylene and propylene glycol are commonly used. "When using

11
glycols in these situations, simultaneous use of oxidative corrosion inhibitors

should be avoided, as these latter substances will degrade glycol to glycolic

acid —a contributing agent to metal corrosion." [14] (dipotassium phosphate

is frequently used as a corrosion inhibitor with glycol antifreeze).

The following quote from unpublished minutes of the recently-held Semi-Annual

Program Review Meeting for Environmental-Related Projects in Solar Heating and

Cooling of Buildings and Agricultural and Industrial Process Heat, Washington,

D.C., February 1978, sponsored by the Department of Energy addressed the

problem of the formation of glycolic acids.

"A significant finding of the discussions at the meeting dealt with the

potential toxicity of the glycols. Glycols may form glycolic acids under

conditions present in solar systems. These glycolic acids can then form

glycolate salts which are highly toxic compounds."

Another source also indicates the problem of the formation of organic acids

under some operating conditions but suggests that these would be in small

quantities [ 15]

Generally under ordinary conditions of industrial use, the most commonly used

glycol, ethylene glycol is considered to be only moderately toxic. However, severe and even fatal poisoning has occurred following its ingestion.

The following information taken from. Draft Environmental Impact Statement of

the National Solar Heating and Cooling Program, [14] discusses the toxicity

characteristics of the glycols as well as most of the common freeze protectants used in solar heating and cooling systems. For a more complete

coverage including corrosion inhibitors, miscellaneous heat-transfer media,

bactericides, insulation and sealing materials, see Appendix B. An attempt is

made to include the lowest lethal dose repoi;ted (LDj^q) and the equivalent

lethal dose for a child.

Toxicity of Glycols

o "Ethylene Glycol — Ingestion may produce injury of sufficient severity

as to threaten life following acute ingestion of large doses. Ingestion

of small doses over time can cause moderately toxic systemic effects(2)^.

The LD^ (oral) for humans of ethylene glycol has been reported at

1500 mg/kg (3). More than 50 human fatatities from the ingestion of

^ References 2, 3, 4, of the report cited above correspond to references [17,

8, 6] of this report.

^ Another source cites, "Up to 60 deaths in a single year have been reported

from ethylene glycol or diethylene glycol," Poisoning; Diagnosis and Treatment , Driesback, Robert H., Lange Medical publications, 1974.

12
o ethylene glycol have been reported and the mean lethal dose (LDcq)

appears to be about 100 milliliters (ml) in adults (4). For a child

to ingest the equivalent of the LDj^q( 1500 mg/kg), approximately

30 ml of ethylene glycol or 0,15 liters or 0.04 gallons (5.1 oz.)

of a 20 percent solution would have to be consumed"

o "Propylene Glycol - Propylene glycol has low toxicity. Industrially,

its uses include serving as a general food additive. Orally adminstered

doses of propylene glycol to rats have resulted in an LD^q of 21 g/kg

(2). This would correspond to a child consuming approximately 2 liters

or 0,55 gallons (70 oz.) of a 20 percent propylene glycol solution.

However, at this dose, a theoretical could be surpassed"

o "Dipropylene Glycol — Similar to propylene glycol (i.e., having a low

toxicity). Oral doses to rats have given an LD^q of 15 g/kg (3). The

human oral lethal dose is probably between 100 and 300 ml of pure solution for adult, or between 100 and 300 ml of pure solution for a child

(4), For a child, the probable oral lethal dose is between 0.5 and 1.5

liters (17,5 to 53 oz.) of a 20 percent solution."

" Siloxanes (Silicon Fluids) - Siloxanes, are of the general formula - R2Si0 - in which R is usually an alkyl group. The toxicity of these compounds generally

is low; many studied do not have toxic properties at all and most have little

or no irritant effect (2),"

"Dow Corning 200 has been fed to rats in oral doses as high as 20 g/kg with no discernable effects. Transitory conjunctive irritation may be caused by introducing Dow Corning 200 to the eye, but no permanent effects have been observed.

No evidence that silicone fluids are absorbed through the skin exists (5),"

" Paraffins (Alkanes) - Effects of Paraffin hydrocarbons vary with volatility.

For solar system fluid use, high molecular weight hydrocarbons would be used.

These high molecular weight (and less volatile) compounds exhibit anesthetic

effects and, at the same time, an increasing irritant action as molecular

weight accrues. The semi -ref ined, fully-refined, and crude paraffins are recognized carcinogens; implanted paraffins in mice produced tumors in doses as low as 600 mg/kg (3), Such effects from acute oral ingestion are unlikely,

however, (oral data were not available),"

" Aromatic and Other Synthetic Hydrocarbons - This family of synthetic fluids

primarily encompasses organic compounds containing modified (polychlorinated)

triphenyls (the Therminol Fluids), The polychlorinated triphenyls are a series

of technical mixtures containing products that vary in composition and degree

of chlorination, Therminol 66 (modified triphenyl by Monsanto) has an oral

LD^q of 10,2 g/kg to rats and a dermal LD^q of approximately 6.8 g/kg to albino

rabbits, Therminol 55 (synthetic hydrocarbons from Monsanto) has an oral LD^q

of 15.8 g/kg to rats and a dermal LD^q of 7.9 g/kg to albino rabbits (6).

To equal the 1-D^q dose level of Therminol 66 (10.2 g/kg), a child would have to

ingest approximately 200 ml (6.8 ounces) of the solution. It should be noted

that, at this dose level, a theoretical LDj^^ could be surpassed."

13
The results of two comprehensive toxicity studies [5, 6] of heat transfer fluids

and common additives were compared in a recent draft report on Hazardous

Properties and Environmental Effects of Materials Used in Solar Heating and

Cooling (SHAG) Technologies [13]. Excerpts from these studies are included

in Appendix B 1 through B 7 and relate to (1) heat transfer fluids; (2) fluid

treatment chemicals; (3) outgassing products; (4) thermal degradation products;

(5) thermal storage media; (6) solids, outgassing products; and (7) combustion

products.

The following examples give some insight into the scope of the hazard created

by some commonly used chemicals.

On a scale of 1 to 6, one of the studies Gosselin, et al [6] rates the following

materials:

Transfer fluids

propylene glycol class 1 practically non-toxic

ethylene glycol class 2 slightly toxic

Fluid treatment chemicals

sodium nitrate class 4 very toxic

*potassium dichromate . . .class 5 extremely toxic

Other studies have given similar ratings for these transfer fluids and

inhibitors [5].

The above ratings are defined and given some relevance in table 5. The

ratings are based on the acute toxicity of a single dose taken orally. The

ratings presented in table 5 are based on LD^q's in mg/kg obtained in laboratory

animals

*Chromate salts are also recognized carcinogens of the lungs, nasal cavity

and paranasal sinus; and suspected carcinogens of the stomach and larynx.

14
TABLE 5 (From Gosselin, et al.)

Toxicity Rating Probable Oral LETHAL Dose (Human)

or class

Dose For 70 kg person (150 lb)

6 Super toxic less than 5 mg /kg A taste (less than 7 drops)

5 Extremely toxic 5-50 mg /kg Between 7 drops and 1 tsp.

4 Very toxic 50-500 mg /kg Between 1 tsp. and 1 ounce

3 Moderately toxic 0.5-5 gm/kg Between 1 oz. and 1 pint

(or 1 lb.)

2 Slightly toxic 5-15 gm/kg Between 1 pt. and 1 qt.

1 Practically

nontoxic

Above 15 gm/kg More than 1 quart (2.2 lb.)

2 . 3 CONTAMINATION HAZARD

The fact that the heat transfer fluids used in solar energy systems are a com- bination of several treatment fluids is of concern and does not appear to be

adequately addressed in the available literature. In some instances, corrosion inhibitors and other additives are more toxic than the antifreeze solutions

themselves. Although these are usually used in small concentration, it is

important to know their effect on the toxicity of the fluid as a whole.

In considering the hazard to man from the use of any compound, there are several

factors which must be considered. In reality, almost any material can have

toxic properties under certain circumstances. The toxicity of a material is

determined by its potential to produce a deleterious response upon contacting

or entering the body. The hazard is determined not only on the basis of its

toxicity but also on the basis of probability that a person will be exposed

to the material under various conditions of use.

The following scenario suggests the level of hazard that might exist in

a somewhat realistic context,

A penetration in the common wall of a single-wall heat exchanger would

permit mixing of the heat transfer fluid and the potable water with

a dilution factor. For example, suppose the heat transfer loop to

the collector contained 6 gallons of 50% ethylene glycol and water,

and the hot water tank had a 120 gallon capacity. Total loss of the

heat transfer fluid into the potable water would result in a mixture

of concentration: ' 3 gallons _ ^ 120 gallons

* °

15
This assumes no additional water is Introduced into the tank.

Table 6 indicates the number of quarts of fluid a person, by body weight would

have to drink of a certain concentration of ethylene glycol solution to obtain

a lethal dose. The quantities to be consumed for children are relatively small

considering that the concentration of the resulting mixture could be on the order

of 2.5%. This represents the "acute toxicity level" as defined in reference [17],

i.e., single dose size. It is not known how the "chronic toxicity level" which

is the ingestion over time is related to the "acute toxicity level."

TABLE 6 - LETHAL DOSE OF ETHYLENE GLYCOL SOLUTION^

Person's

Body Weight

Number of Quarts

by

to be Consumed for

2 Concentration

a Lethal Dose

1% 2% 2.5% 3%

25 lb. 1.7 qt. 0,8 qt. (25.6 oz) 0.7 (22.4 oz) 0.6 qt. (18.1 oz.)

50 lb. 3.4 qt. 1.7 qt. 1.3 1.1 qt.

75 lb. 5.0 qt. 2.5 qt. 2.0 1.7 qt.

100 lb. 6.7 qt. 3.4 qt. 2.7 2.2 qt.

200 lb. 13.4 qt. 6.7 qt. 5.4 4.5 qt.

The preceding table is developed from the following calculations.

The lethal dose of ethylene glycol by body weight [15] is;

1,4 ml (volume of ethylene glycol)

1 kg (body weight of person)

Converting this to pounds:

1.4 ml

Converting to quarts/lb;

U

1 gal

3785 ml

IL

2.205 lb

= 0.6349 ^

lb

X

gal

X 0.6349 ^

lb

= 0.000671 ^

lb

Therefore, a lethal dose is 0,000671

lb

For example, a 100 lb person would ingest a lethal dose from:

0.000671 X 100 = .0671 qt (2.15)

(This is equivalent to 1 quart (32 oz.) of 6,7% concentration of ethylene glycol

or 6,7 quarts of a 1% concentration).

This represents the "acute toxicity level" as defined in reference [16],

i.e,, single dose size. It is not known how the "chronic toxicity level"

which is the ingestion over time is related to the "acute toxicity level.

16
It is to be noted that these examples do not assume the presence of inhibitors

or stabilizers in the heat transfer solution and the corresponding effect they

might have on the toxicity of the solution. It is also noted that this scenario

does not account for additional water supply coming into the tank to replace

that which is drawn off. If this factor is taken into account the resulting

concentration may be reduced by as much as 50%.

2.4 SELECTION OF HEAT TRANSFER FLUIDS

There is growing awareness of the importance of the selection of the heat

transfer fluid to the performance and reliability of the solar energy systems.

Many factors are to be considerd in this choice. Basic considerations include

thermal performance, cost effectiveness, reliability and safety. Consideration

must also be given to system type, size and materials, operating conditions,

climate, and level of maintenance and monitoring capability. Similar consideration should be given to the selection of additives such as Inhibitors and detectants as well as liquid concentration.

The following fluid characteristics summarize some of the most important selection considerations.

(a) Stability, both thermal and oxidative, for the operating temperatures

including stagnation, liquid range (freezing to boiling temperatures),

decomposition temperature and vapor pressure.

(b) Thermal properties i.e. specific heat and thermal conductivity.

(c) Flash point and fire point.

(d) Hydraulic or transport properties such as specific gravity and viscosity

at operating temperatures.

(e) Metal comptability , dielectric and corrosive characteristics.

(f) Toxicity (including additives and products of decomposition), local

health department approval.

(g) Cost and service life estimates under operating conditions.

Since the heat transfer fluid is "common" to most other components within the

solar loop, it's early selection within the design process will influence other

design decisions with respect to operating temperatures, flow rates, materials

and protection.

The reader is referred back to tables 1,2 and 3 for information on fluid characteristics listed above.

3 . HEAT EXCHANGERS

3.1 CAUSES OF FAILURE

Heat exchangers used in solar assisted domestic hot water systems are subject

to a wide variety of degradation mechanisms some of which are unique to this

particular application. Corrosion is a threat at both the interface with potable

water and the heat exchange fluid. The composition of the heat transfer fluid

can be modified to retard corrosion but of course alteration of the potable

water supply is usually not considered except in the case of water softeners.

In different areas of the country there is a wide difference in the mineral

content and pH characteristics of the water supply. Consideration must also

17
be given to the use of individual well water and the water variations that are introduced because of them. Heat exchangers will be subject to the same conditions that have led to the very rapid deterioration of conventional hot water

heaters in parts of California and New England, Conditions of highly conductive

water (California) and nonconductive water (New England) have greatly reduced

the service life of hot water heaters in some cases (sometimes as short as 2 years) [18]. But in solar hot water systems, the potable water is also exposed

to the threat of contamination by the heat transfer fluid. Special efforts are needed to resolve these kind of problems.

A range of metals may be used for heat exchangers or in the immediately adjacent

plumbing system. These may include steel, galvanized iron, copper, bronze,

brass and aluminum; however, copper and steel are most commonly used in heat

exchangers. Each of these metals, to a greater or lesser degree, adds its own particular corrosion problems to a closed recirculating system even if dielectric isolation of dissimilar metals is provided.

In fresh water supply systems, the corrosion resistance of copper depends on the

presence of a surface oxide film through which oxygen must diffuse in order for

corrosion to continue. The film is easily disturbed by high velocity water or

is dissolved by either carbonic acid or the organic acids which are found in

some fresh waters or soils, leading to an appreciably higher corrosion rate.

The following discussion is taken from Corrosion and Corrosion Controls [19],

"For example, in hot water in Michigan, zeolite softened with resultant

high concentration of H

2CO2

, was found to perforate copper water pipe

within 6 to 30 months. The same water unsoftened, on the other hand,

was not nearly as corrosive because a protective film of CaCO^ containing

some silicate was deposited on the metal surface."

Heat transfer fluids are most often pumped through heat exchanger components

at a wide range of temperatures and in various systems at a range of pressures

and flow rates. It is generally recognized that flow rates should be maintained

below 4 to 6 fps to prevent erosion corrosion. These factors have significant

affect on corrosion rate as well as mechanical stresses within heat exchanger

coils. Very high temperatures (350 to 400 °F) which may occur under "stagnation"

conditions will cause some heat transfer fluid components (such as the glycols)

to break down and become acidic. Under these conditions the fluid is more corrosive and probably more toxic.

The manner in which the system is fabricated greatly affects its susceptibility

to attack. Crevices, deposits and miscellaneous debris can obstruct access

of dissolved oxygen to the metal surface and thereby set up differential

aeration cells. The latter are detrimental to all of the metals involved,

but especially to aluminum, monel and stainless steels.

Inappropriate combinations of different metals in a single system cause severe galvanic corrosion. Direct couples may develop during operation of the system.

Traces of metals dissolved from upstream portions of the system frequently

deposit on contact with more active components which can lead to serious attack

of the more active metals. Impingement attack of copper is a rather common

source of trouble in some larger installations such as apartment and institutional buildings. According to Hatch [20] the difficulty often stems from

18
an unfortunate choice of materials, because copper is particularly susceptible

to attack of this nature. Impingement attack on copper can also be caused by

the separation of dissolved air from the water due to excessive pressure reduction or excessive flow velocity.

"Copper also may suffer localized attack (i.e,, pitting) which does not involve

excessive flow velocities. It is fortunate that pitting of this type seldom is

encountered because its causes are not fully understood," [20]

The following list elaborates on some of the causes of heat exchanger failures

mentioned earlier in the introduction,

o Corrosion

- Increases with temperature

- increases with excessive velocity or flow rate (corrosion and erosion)

- pH affects both type and velocity of corrosion

- affected by cavitation

- affected by crevices, deposits and miscellaneous debris (deposit

attack)

- affected by amount of dissolved oxygen and presence of trace

impurities (chlorides, heavy metal ions, etc,)

- affected by the composition of the heat transfer fluid

- affected by stress (stress corrosion-cracking)

o Thermal Stress

- expansion and contraction

- thermal shock

- freeze up (expansion)

o Mechanical Stress

- fabrication and installation

- impact

- bending, cracking

- faulty seams

- loss of strength and ductility (Intergranular corrosion)

Current corrosion test methods that are applicable to solar energy components

are listed in Table 7,

See also Section S-515-2.3.2.3 (pp 5-16 to 5-30) of the S/MPS for further

discussion of corrosive conditions,

3.2 DISCUSSION OF GENERIC HEAT EXCHANGER TYPES

Thermal performance is the parallel, if not equal, consideration to safety in

heat exchangers. The thermal performance of the heat exchanger is a key ingredient to the total domestic hot water (DHW) system efficiency. In a basic

sense, safety is increased with an increase in separation (e,g,, the use of

multiple walls) between the potable water and the heat transfer fluid (HTF)

(which may be non-potable) whereas thermal efficiency is often decreased by

such an increase in separation of the two fluids.

19
TABLE 7 - CURRENT CORROSION TEST METHODS [3]^

Title Comment

NACE TM-01-71 Autoclave Corrosion Testing

of Metals in High Temperature

Water

Modify to reflect

conditions present

in solar systems

NACE TM02-74 Dynamic Corrosion Testing of

Metal in High Temperature

Water

Modify to reflect

conditions present

in solar systems

NACE TM-02-70 Conducting Controlled Velocity

Laboratory Corrosion Tests

Modify to reflect

conditions present

in solar systems

NACE TM-01-69 (1972) Laboratory Corrosion Testing

of Metals for the Process

Industries

Describes factors

to consider in

corrosion testing

ASTM DI384-70 (1973) Corrosion Test for Engine

Antifreeze in Glassware

Modify to reflect

conditions present

in solar systems

ASTM D2570-73 Simulated Corrosion Testing

of Engine Coolants

Modify to reflect

conditions present

in solar systems

ASTM D2776-72 Corrosivity of Water in the

Absence of Heat Transfer

^Modification of test procedures developed for purposes other than collector material

testing shall adequately reflect all expected collector conditions including

no-flow conditions.

20
Overall conductance for a heat exchanger is the product of the overall heat

transfer coefficient (which depends on the thermal properties of each fluid,

the fluid mass flow rate and the heat exchanger geometry) and the associated

heat transfer surface area. The extent of separation, as required for safety,

is greatly affected by the heat exchanger geometry. The other variables which

deserve much design considerations are fluid thermal properties, mass flow rate

and transfer surface area.

There are wide variations in the effectiveness of heat exchangers used in and

proposed for solar DHW systems. There is not widespread knowledge of their relative efficiencies or thermal performances in varied applications. Calculation

methods for heat exchanger performance are described in the ASHRAE Handbook of

Fundamentals. [21] A minimum effectiveness value of 0.7 is a typical value that

is used. This value was also used in the correlation studies which provide the

basis for the calculation method used in the S/MPS supplement for solar installations.

The following brief descriptions are taken from the point of view of solar

assisted domestic hot water systems. The description covers a broad range of

pertinent type heat exchangers but does not represent an exhaustive study. The

discussion includes proposed as well as commercially available heat exchangers.

Unless otherwise stated, the comments are made without regard to materials or transfer fluid types. The comments regarding relative performance and cost are

made in a general sense without consideration of transfer fluids, flow rates

and specific manufacturing processes. The comments are based on judgment but are appropriate for the evaluation of heat exchanger types. Transfer fluids are taken as non-potable without regard to degree of toxicity.

The graphic illustrations are intended only to express essential relationships;

more literal illustrations are included in Appendix A. The illustrations in

Appendix A are accompanied by the "key” sketch in the text. These illustrations

are not detailed and are used to provide an understanding of the relationship

between the heat transfer fluid and the potable water and general configuration

of the heat exchangers. The following legend is used with these illustrations:

fe^^heat transfer fluid

IlllllllJ intermediate exchange fluid

^=^potable water

Tube in Shell

Heat exchangers of this type usually consist of a coil (or bundle) of a single

tube, usually containing the transfer fluid, immersed in the potable water. The

outside surface of the tube is sometimes covered with fins to provide greater

surface contact for the heat exchanger process. The tube-ln-shell heat exchanger

is categorized here as relatively high in thermal efficiency. The efficiency

is improved with optimum placement in the water tank and with outer surface configuration to increase heat exchanger contact. This type is categorized here as low in cost as compared to other heat exchangers discussed. See illustrations,

page A-1,

21
The tube-in-shell heat exchanger provides only a low category of safety. A

failure of the tube creates an immediate potential for contamination of the

potable water by the transfer fluid. Corrosion can attack the tube from either

side of the tube wall. Increasing the wall thickness of the tube wall increases

the time to failure due to corrosion but is not likely to stop it. There is

little means of detecting a leak if one occurs and pressure differential cannot

always be considered adequate to prevent contamination. Although the potable

water pressure would normally be higher than that of the heat transfer fluid,

a drop in water pressure would remove the protection.

This is a very common type of heat exchanger and is frequently used especially

in applications not involving potable water. The use of single wall heat

exchangers was permitted by local code officials in demonstration projects

recently sponsored by the New England Electric Company; however, contractors were

required to submit evidence that heat transfer fluids used were not toxic.

Double Tube in Shell

Most of the preceding discussion applies to this type as well. The major distinction is that the tube is double formed in a process in which an inner tube

is swaged or expanded inside an outer tube so that there is intimate mechanical

contact. This increases the cost and lowers, at least slightly, the thermal

efficiency. Although it technically meets the safety criterion of providing

a double wall between the transfer fluid and potable water, it is still vulnerable to the pit corrosion phenomenon which is likely to proceed in a selfsustaining process in a path through both walls. It is questionable as to

whether the extremely tight fit between the two walls aids in the detection of

a leak or helps retard contamination. If the two tubes are swaged together and

form a tight bond they are essentially one tube..

There is increasing use of this type in solar demonstration programs, although

there is continuing controversy as to the margin of safety it provides.

A proposed modification of this type has a spiral formed tube inside another

tube i*n a way that only the ridge of the spiral of the inner tube contacts the

wall of the outer tube. This configuration greatly enhances the safety and provides an inner channel for potential leakage to flow out and aid in detection.

However, the reduced inner surface contact may reduce efficiency. If the inner

channel was filled with an intermediate fluid it would increase the efficiency

but would also eliminate leak detection. See illustrations, page A-1.

Tube on Shell. .. .Separated (or double wall separation)

A common version of this type which is currently in use is the wrap-around or "jacket" type. The jacket may consist of, multiple passages or tubes, or a single void surrounding the potable water tank, for circulation of the heat

transfer liquid. In some installations, a single tube is wrapped around the

perimeter of the potable water tank. Heat transfer efficiency is largely determined by the quality of the contact between tube or jacket and the tank. See

illustrations, page A-3,

22
A separation between the double walls provides an additional element of safety.

This separation may be achieved by a layer of solder or a conductive material

between the adjacent walls. The thermal efficiency of the heat exchangers may be

improved or reduced depending by how the separation is achieved. There are some heat conductive adhesives which the manufacturers claim will greatly increase the

performance of the heat transfer process. The separating material should inhibit

the corrosive tendency to penetrate the two adjacent walls, A similar heat

exchanger, being developed at this time, consists of two coils of tubes (in this case one is copper and one aluminum) attached by a layer of solder as well as encased in solder. The fabrication involves placing the coils in an ultrasonic

vat of molten solder which drives off impurities as well as totally encasing

all tube surfaces. The solder is of high zinc content which acts as an anode

to the aluminum and copper and inhibits corrosion. The solder encasement also

enhances heat transfer between the tubes.

The thermal performance of this particular exchanger is thought to be high.

Others of this type vary from medium to high in performance depending on the

characteristics of the material or separation between the heat exchanger walls.

The cost as well as the level of safety will also vary between medium and high.

The safety level of this type should rank clearly above those of double walls

in intimate contact. It is noted that the double wall with separation provides

the level of protection that NBS currently proposes as appropriate for use in

the solar demonstration programs.

One proposed design of this type enhances the safety by inserting a higher alloy

or more noble metal as an interface between the two tubes. The plausible theory

here is that the noble metal will intercept the corrosion of either tube and

reverse it rather than penetrate the higher alloy interface and the second tube.

This type consists of two tubes, one containing potable water and the other a heat transfer fluid, both immersed in an intermediate exchange fluid. The intermediate fluid adequately separates the potable water from the heat transfer or the

collector loop fluid but is probably somewhat non-potable itself by reason of being

stagnated in a closed system or it may contain additives or it may be contaminated

by the heat transfer fluid by way of a leak. See illustration, page A-2.

If the tube containing the heat transfer fluid fails due to corrosion, the corrosion

pit will contact the intermediate fluid and the electrochemical cell will be disrupted. If the intermediate fluid becomes non-potable because of stagnation or

leak, this heat exchange type may be considered single wall, providing only a one wall separation between the non-potable intermediate fluid and the domestic hot

water. However, dilution by the potable water of any metal ion by the

Intermediate fluid would most likely result in a minimal hazard.

One major advantage of this type exchanger is that a strong potential for leak

detection is possible if a view glass is placed in the intermediate fluid container and if a concentrated dye is added to the heat transfer or solar loop

fluid. This of course does jiot aid detection of a leak of the intermediate fluid

into the potable water.

Shell and Double Tube

23
The performance as well as the cost of this type Is depiendent upon the details

of the design but generally the performance as well as the cost is in the medium

range. The safety aspects have been suggested in the previous paragraph. It

is Important however to not overlook the observation and leak detection potential

within the intermediate fluid.

Double Shell and Tube

This heat exchanger type has many similarities with the Shell and Double Tube,

An intermediate exchange fluid is conveyed by the tube, taking on heat from the

solar loop, transporting it and giving it up to the potable water storage.

There are essentially two heat exchangers in the process; one with the solar

loop and another with the potable storage. The potable water is adequately

separated from the transfer fluid of the solar loop. but it is susceptable to

contamination by the intermediate exchange fluid in much the same way as in

the double shell. The intermediate fluid will act as a barrier to a corrosive

pit continuing and will generally intercept any leakage of the heat transfer

fluid. It is therefore a double wall heat exchanger relative to the heat transfer fluid, though it may be considered only single wall relative to the intermediate fluid. Again there is opportunity for leak detection by providing a view glass in the intermediate tube. There are further similarities in the performance and cost categories both falling into the medium range. See illustration, page A-2.

Tubes and Fins

The "fin coil" heat exchanger was initially developed for the

industry but more recently has been applied to solar assisted domestic hot

water systems. It consists of rows of tubes alternately containing heat exchange

fluid and potable water connected by closely spaced fins of the same materials,

usually copper. The fins conduct heat between alternate rows of tubes and

serve to separate the potable water tubes from the non-potable tubes. The fins

also provide an area for leaking fluid to drain and become observable. See

illustration, page A-4.

Following the claim of the manufacturer and some users as well as engineering

judgment these exchangers will be rated here as high in peformance and medium

in cost. The extent of separation between potable and non-potable and the

potential for leak detection would cause this type to have a very high safety

ranking.

The "tube in a block" exchanger might be considered a variation on the "fin

coil" exchanger. As the title suggests, this heat exchanger is distinguished

by separate tubes containing the heat transfer fluid and the potable water,

which are cast in a solid block of metal. In a way similar to the fins of

the fin coil, the solid block (usually aluminum) conducts the heat from

one tube to the other. The thermal performance and cost of this type would

to a great extent depend upon the metal used as the "block". Generally,

both cost and peformance will probably be in the medium to high range.

24
Triple Tube

This type consists of three separate tubes for (1) the heat exchanger fluid,

(2) potable water, (3) and intermediate "dead” passage. The dead passage is

positioned between the other two tubes and conducts heat between them through

its walls. This provides a four wall separation between the exchanger fluid

and the potable water. The dead passage provides a means of drainage for

potential leaks and detection of leaks if proper "weep" holes are provided.

There are strong similarities between this exchanger and the "fin coil"

previously discussed, with the dead passage functioning in much the same way as the fins in exposing potential leaks but is a more "closed" detail.

See illustration, page A-4.

The heat conductance paths through the dead passage tube walls is somewhat

indirect and may result in some loss in efficiency. • This design is just coming

on the market and its cost would be greatly dependant on the manufacturer's

process. Use of pressure welded metal sheets may simplify fabrication but could

create potential for crevice corrosion.

Because of the extent of physical separation between the exchange fluid and the

potable water, as well as the potential for leak detection, the safety for this

design is assumed as better than adequate,

Shell/Film and Pressure

This heat exchanger type might also be described as a "cascade" design. The

potable water is contained in a conventional tank such as galvanized steel with

a glass lining. The heat exchange fluid flows over the tank in a cascade bathing

the entire surface in a film of exchange fluid. The cascading film is in a non-pressurized chamber so that under normal conditions the potable water is at

a higher pressure than the exchange fluid therefore protecting the potable water

in the event that a leak occurs. If the potable water pressure should drop for

any reason a pressure sensor is actuated and the pump automatically stops the

cascade of transfer fluid which drains to a harmless location beneath the tank.

It is important to note that the transfer fluid reservoir is below the tank and

therefpre the container of the potable water is not in contact with the fluid

when the film flow is stopped. See illustration, page A-3.

Although only a single wall separation is provided between the exchanger fluid

and potable water, the uniqueness of the design stops the pump which stops the

flow of the exchange fluid causing it to "fail safe" or in a mode avoiding a hazard. More than one failure would be required to create a hazard, i.e,, a leak and a flow control failure, and thus essentially double protection is

provided.

The thermal performance of this process is taken to be in the high category

because of the efficiency of the heat transfer film. The cost may be considered

to be moderate since many of the components are conventional water heater element

Heat Pipe

The heat pipe is not currently used within solar energy systems but its potential for such application deems it appropriate for discussion in this context.

25
It is a very effective heat exchanger that has successfully been used in waste

heat recovery processes.

The operating mechanism of the heat pipe is very straightforward. The device

makes use of a working fluid whose latent heat of evaporation is transferred from

a heat source to a heat-utilizing medium by means of an evaporation-condensation

cycle. Condensed liquid is returned to the heat source (the heat pipe evaporator)

usually by gravity or by a self-contained pumping mechanism, i,e,, wicking. The

effectiveness of the process is such that heat pipes have been constructed with

an equivalent thermal conductance more than ten thousand times greater than copper.

Such highly effective heat transfer capability is not, however, the only attribute

of the heat pipe. By suitable design, heat pipes can be constructed to serve such

functions as precision temperature control, one-way transmission of heat (thermal

diode) and heat flux amplification or diminution. The working fluids that can be

used to achieve these effects range from liquid hydrogen for cryogenic temperatures

to silver and copper at very high temperatures. Ammonia, freon or water would be

appropriate working fluids for solar applications. See illustration, page A-4,

The thermal performance potential for heat pipes in both air and liquid solar

energy systems is obviously very high but so is the cost at this time. Research

and development is currently underway for passive solar applications of heat

collection and storage which are strongly indicating cost effectiveness at this

time. The working fluids of the heat pipe vary widely with the specific applications and it is premature to discuss the degree of toxicity at this time. The

physical separations from the potable water would be single or double wall depending

on the design integration with the potable water storage.

Liquid to Liquid (Direct Contact)

Investigation is in progress at Colorado State University [22] with a heat transfer process that eliminates the mechanical heat transfer surfaces in the heat

exchanger. This process would utilize an immiscible heat transfer liquid in

direct contact with the storage water. Although there are no stated intentions

of using the process to heat potable water, extensive toxicological evaluation

is being made of the liquids proposed for use.

The liquid is delivered to the top of the storage tank, is broken up into droplets by a perforated plate and after flowing by gravity through the storage water

(without mixing with it) collects in the bottom of the tank. It would then be

drawn off and recirculated through the solar collector loop. Efficient heat

transfer would occur across the large collective area of the droplets at temperature differences between the droplets and the storage water of only about 1°F or

less, A temperature differential of up to 10 to 15®F is required in some of the more conventional heat exchangers. See illustration, page A-3,

It would be premature to try to evaluate the process as to efficiency, safety

and cost. However, if suitable liquids are discovered, the potential for high

thermal performance is great,

Plate Heat Exchanger

The plate type is a simple heat exchanger, resembling a plate and frame

It is made up of a "package" of gasketed plates, aligned top and bottom on carrying

filter.

26
bars between two covers, and held by bolts. The plates have corner ports and

nozzles with gaskets around these ports which control the flow of the liquids

(HTF and potable water) in alternate spaces between the plates. Configuration

of the gaskets at the port and perimeter provide two separated gasket walls

between the two liquids at the entry port and provides an atmospheric drain

channel to prevent possibility of gasket leakage between liquids. Plates can

be designed so that there are no contact points between adjacent plates or so that there will be metal-to-metal contact between plates. The plates are stamped

or pressed of thin sheets of stainless steel or a variety of other materials.

Although there are two gaskets separating the liquids at the ports, there

is only a single wall (plate) separating them in the process of heat transfer,

therefore as currently used it is a single wall heat exchanger. See illustration,

page A-5.

) The plate heat exchanger has been. -."used extensively by industries having sanitary requirements," [23] e.g., the dairy industry for handling all types of

milk and cream and for other beverages and food industries. As discussed in

Section 4, the emphasis in these applications is on frequent cleaning and close

monitoring of the heat transfer components. The consideration of using this

type heat exchanger for solar DHW application is, as with food processing, based

strongly upon the potential for disassembly and inspection of the components as well as its high thermal performance. The flexibility of this type lends itself

to size and capacity modification, component replacement and cleaning on site.

Although simple in fabrication, the relative cost of this type is likely to

depend on the feasibility of installation at the scale appropriate to DHW.

Thermal performance is very high relative to most of the other types discussed

and safety would be contingent upon the reliability of routine inspection, as mentioned above. This may be difficult to achieve and perhaps Inappropriate

for residential installation with toxic liquids. Consideration might be given

to increased safety by introducing two walls or an intermediate transfer fluid on an alternating basis between the potable water and the heat transfer liquid (solar

loop). The double wall or intermediate fluid would have the same advantages and

be subject to similar conditions as those discussed in earlier examples.

3.3 AVAILABILITY OF HEAT EXCHANGERS FOR SOLAR

There has been a growing concern for the availability of double wall heat

exchangers and general lack of awareness of who makes them. Contractors claim

difficulty in obtaining them and yet a recent publication, "Solar Engineering

Magazine", March 1978, indicates "More manufacturers offer double wall protection

than single wall protection. There are 26 with double wall, 10 with single

wall and 6 offering both features." [24]

Further investigation by the authors indicates that there are a small number of

manufacturers making most of the heat exchangers and domestic hot water tanks

being used. Many others, basically commercial firms, are marketing these and

other components usually as a package solar DHW systems under a wide range of

brand names. There is strong evidence that additional heat exchangers, some manufactured for other processes, are becoming available for solar application.

27
Five of the largest manufacturers accounting for a large majority (greater than

2/3) of solar related DHW components have received the following certification

from the International Association of Plumbing and Mechanical Officials (lAPMO):

MANUFACTURER TYPE OF lAPMO STATUS

American Appliance (Mor-Flo) wrap around jacket type approved

by lAPMO as Double Wall

approved by lAPMO as Double Wall

cascade or film flow type approved

by lAPMO as Single Wall (lAPMO is

currently considering Rheem’s

"Double protection" which is provided

by a pressure switch)

internal "flue" type coil, glass

lined pressure drop warning and

leak detection, approved by lAPMO

as Single Wall

tube in a tube, somewhat controversial

because of tight contact between

the two tubes but has been accepted

in some demonstration programs as double protecting. Ford has requested

lAPMO application.

The W. L. Jackson Manufacturing Co., uses a wrap around, double wall heat exchanger

type made by Energy Converters Inc. and may be considered among the large suppliers.

This is not intended to be an all inclusive list of manufacturers of heat exchangers

for solar application. Others are listed in the above referenced issue of Solar

Engineering Magazine. Still others are achieving double wall protection by using

dual single wall exchangers and an intermediate fluid.

3.4 HEAT EXCHANGER SELECTION

Heat exchangers to a great extent determine the effectiveness at which collected

energy is made available to heat domestic water. It is also the device that

separates and protects the potable water supply from contamination if non potable

heat transfer fluids are used. Similar to the selection of the fluids, basic

considerations for heat exchanger selection include thermal performance, cost

effectiveness, reliability and safety.

The following characteristics are important selection considerations:

(a) Heat exchange effectiveness

(b) Pressure drop-operating power, flow rate

(c) Physical design, configuration, size, materials and location in the

system

(d) Cost(s) and availability

A. 0. Smith

Rheem/Rudd

State Industries

Ford Products

28
(e) Protection of the potable water supply from contamination by the heat

transfer fluids, reliability

(f) Leak detection, inspection, maintainability

(g) Material compatability with other system elements i.e. metals and

fluids

(h) Thermal compatability with system design parameters, i.e. operating

tempertures, flow rate, fluid thermal properties.

Some of these characteristics are discussed in Section 3.2 and illustrations

are given in Appendix A. The interdependence of choice of heat exchangers and

heat transfer fluids is to be noted with respect to safety as well as thermal

performance

4 . RELATED APPLICATIONS

4.1 HEAT EXCHANGERS USED IN FOOD PROCESSING

The uses of heat exchangers in food processing is in many ways an analogous

situation to that of domestic water heating in solar assisted systems. Heat

transfer fluids very similar to those used in some solar energy systems are brought into close proximity to foods or beverages in a variety of processes.

Heat exchangers are used in various phases such as manufacturing, preparation

and temperature retention. The processes Include such widely divergent activities

as scalding poultry and hogs with a mixture of propylene glycol and water, use

of ethylene glycol in heat exchangers to cool milk or to make ice cream and

other heat transfer means to heat or cool beverages in dispensing machines. The

heat transfer process in water fountains and ice making will be covered in a subsequent section.

The major emphasis with food product related exchangers is cleanliness, frequent

inspection and accessibility for cleaning. Stainless steel is most frequently

used with specific attention given to gaskets and fittings. The heat exchangers

most frequently used are single wall , usually of the plate type and frequently

"scraped" or with surface configurations to create turbulent flow. The major

point to be made is that few standards exist to regulate heat exchangers in

food processing and none that determine the types used (such as double wall.)

Occasionally in the processing of milk but more frequently in the freezing of

ice cream an aqueous solution of ethylene glycol is used as a heat transfer

fluid. The stainless steel, plate type, heat exchangers used provide only a single wall separation between the ice cream and the ethylene glycol solution.

According to one authority with the Dairy and Food Industries Supply Association

(DFISA) this is common practice [25].

Some heat transfer fluids used in solar heating and cooling systems such as propylene glycol and glycerin are known to be used in the preparation of and even as additives to foods, pharmaceuticals, and other products. However, the

fluids as used above would most likely be chemically pure, contain no harmful

additives and would not be exposed to temperatures that could result in thermal

decomposition. Fluids used in solar energy systems are frequently degraded and

complicated by some or all of these factors. Furthermore, in most of these food

29
related processes there is a system of control and monitoring of the products

which is not the case with domestic hot water. Frequently there is also a large

amount of product compared to the amount of heat transfer fluid used.

The use of propylene glycol is a common and accepted practice in the scalding

of poultry, tripe and hogs. Its use is permitted at "sufficient" levels if

removed by rinsing. Labeling is required for chemicals used in washing, denuding

or otherwise processing poultry, tripe or hog carcasses including maximum allowable

concentrations of use for the preparation. Polyethylene glycol is used as a boiler water additive for steam preparation of similar foods.

Heat exchangers used in food processing are not generally regulated with regard

to design or extent of separation of heat exchange fluids and food products.

Provisions covering materials used, and accessibility for cleaning dominate the

standards written for food related heat exchangers.

The following excerpts taken from "3-A Sanitary Standard for Tubular Heat Exchangers

for Milk and Milk Products" (serial #1204) [26] are typical and are cited here

for their relevance to issues raised in this report.

Materials

C.l All product contact surfaces shall be of stainless steel of

the American Iron and Steel Institute (AlSl) 300 series of

corresponding Alloy Casting Institute (ACl) types, or equally

corrosion resistant metal that is non-toxic and non-absorbent

except that:

C.1.1 Optional metal alloy may be used formulated by: International

Association of Milk, Food and Environmental Sanitarian, United

States Public Health Service, The Dairy Industry Committee, but

only in applications requiring disassembly and manual cleaning.

(See Appendix, Section G for the composition of an acceptable

optional metal alloy.)*

The standard developed for plate type heat exchangers for milk and milk products

has the following provision under FABRICATION :

D-7

A leak protector groove of sufficient width to be readily cleanable

and open to the atmosphere at both ends shall be provided to allow

leakage past gaskets to drain to waste.

4.2 HEAT EXCHANGERS USED IN FOOD AND BEVERAGE DISPENSING

The following is taken from the National Sanitation Foundation, Standard for

Automatic Ice Making Equipment: [27]

*An Alloy of the composition given above is properly designated "nickel silver",

or according to ASTM Specification #B 149-70, may be entitled, "leaded nickel

bronze." Copper makes up approximately 62% of this alloy.

30
4.30 Refrigeration Components: (4.30.1) Coils and Tubing: Evaporation

coils and refrigerant tubing shall be of such material that it will not

contaminate the product and shall conform to cleaning requirements.

Refrigeration coils, if exposed within the ice storage bin, shall

be finless type and so located that they can be easily cleaned.

Similar wording is used in a provision covering refrigeration components

for Vending Machines for Foods and Beverages (Standard #25) but the following

is added:

If a blower or fin type evaporator is used, it shall be enclosed in a housing to protect against spillage of food or beverage, and such

housing shall provide for drainage of any accumulation of condensate.

Refrigeration coils shall be protected against spillage of foods

or beverages.

According to the National Automatic Merchandising Association (NAMA) , the most common and almost universal method of heat transfer used to cool potable water,

syrup and (in pre-mix units) carbonated soft drinks has been through immersion

of the potable liquid in "pre-cooling" coils or submerged syrup wells in

rigsrated , atmospheric waterbath compartments [28]. For many years, the

immersed water tubing in vending machines was single wall copper in 20-25 foot

coils about 12 inches in diameter. For copper poisoning protection, all venders

now use stainless steel for both the product water and the syrup tubes (which

also are submerged for cooling).

NAMA has never had a report involving accidental contamination of products

as a result of tubing Immersion. This, of course, does not guarantee that

ruptures have not occurred. However, a rupture would result immediately

in overflow of the water bath into the waste pail cut-off control (a Manual

requirement) and failure of the carbonator to function. A service call would

result and probably be reported to the NAMA.

NAMA publishes a Vending Machine Evaluation Manual used in their Machine Certification Program. Last year (1977) their Health-Industry Council approved a proposal to spell out a prohibition of any plumbing connections or fittings

in potable cooling water. This has been an unwritten rule and industry practice

which has not been included in earlier drafts of the Evaluation Manual. While

explaining that waterbath cooling liquids of a toxic nature have not been used,

NAMA expressed reluctance to such a practice unless there were standards for:

(a) tubing materials gauge and ductility

(b) pressure tests after forming

(c) corrosion resistance to the coolant used

(d) freedom from fittings on other connections below the overflow

spill level

(e) if possible, a shut-off in case of pressure loss or vacuum in the

potable water

31
5. EXISTING CODES AND STANDARDS

5.1 CODES AND STANDARDS FOR SOLAR HOT WATER SYSTEMS

Standards and codes for solar energy systems are not yet broadly developed since

this represents a relatively new technology. NBS has recently completed

review of statutes and state legislation related to solar energy

of buildings [29, 30]. With some notable exceptions there is little definitive

work at this time especially on the subject of heat exchangers. There is however,

growing commitment and activity to meet the need for standards at the National

as well as state levels among standard promulgating organizations.

The building codes of most states and local jurisdictions do not deal specifically with the installation of solar hot water systems. However, minimum guidelines for solar systems were recently proposed in the city of Los Angeles and

are undergoing public hearings [31], The guidelines set out the building permit

and operating requirements for installation of solar systems. These guidelines are

the only code document in which double-wall designs are specifically required for

heat exchangers used with solar assisted domestic hot water systems. The pertinent

criterion is:

"Heat Exchangers Containing Potable Water: Double wall separation

is required between any toxic fluids and the potable water supply.

In addition, the heat exchanger must have an exposed area where leaks

in the system can be seen. Only single wall separation is required

if a non-toxic fluid is used. However, the system must be under

manufacturer's control of guarantee that no toxic fluid will be used

in the system. Evidence shall be provided that a quality assurance

program is employed by the manufacturer. If the system is not under

manufacturer's control, the Testing Laboratory will not approve single

wall systems,"

This imposes a severe requirement on the heat exchanger manufacture if a single

wall design is used. Essentially, he must guarantee that toxic fluid will never

be used in the system. There is however a similar provision for the control of

heat transfer fluids in refrigeration systems.

The following is taken from the BOCA (Building Officials and Code Administrators)

Basic Mechanical Code, 1978. [32]

M-812.2 Refrigerant substitution : Substitution of kind of refrigerant

in a system shall not be made without the permission of the administrative

authority, the user, and the makers of the original equipment, and with

due observance of safety requirements including:

1) the effects of the substituted refrigerant of materials in the system;

2) the possibility of overloading the liquid receiver which should not be

more than eighty (80) percent full of liquid;

3) the liability of exceeding motor horsepower, design working pressure or any other element that would violate any of the provisions of this article;

32
4) the proper size of refrigerants controls;

5) the effect of the operation and setting of safety devices;

6) the possible hazards created by mixture of the original and

substituted refrigerant; and

7) effect of the classification of the refrigerant as provided

in this article.

The following provisions from SMACNA (Sheet Metal and Air Conditioning Contractor’s National Association) [33] demonstrate the position of this group.

SMACNA - Heating and Air-Conditioning System Installation Standards For

One and Two Family Dwellings and Multi-Family Housing

Section 25,4 - Domestic Water Preheating Systems

(a) Collectors - Domestic water can be preheated by circulating the potable

water supply through solar collectors.

(b) Preheat Coil in Storage - A suitable sized coil installed in the thermal

storage container of a solar space heating system allows the potable

water supply to pass through the heated container prior to entering the

auxiliary storage tank. Unless the coil and piping has double wall

construction, this method can only be used for liquid type solar systems

employing non-toxic storage media.

(c) Preheat Tank in Storage - The domestic water preheat storage tank is located

within the thermal storage container of a solar space heating system. The

water supply passes through the storage to the preheat tank where it is

heated, stored, and piped to the auxiliary water heater prior to distribution, Double wall construction will be necessary unless a non-toxic storage

media is used.

(d) Preheat Coil or Tank Outside of Storage - Heated liquid from the thermal

storage container of a solar space heating system is pumped to a heat

exchanger - coil or tank - for domestic water preheating. If liquid

from thermal storage is toxic, the required separation is achieved by two

separate heat exchanger colls with a preheat tank or by use of a doublewalled heat exchanger.

The preceeding standards of SMACNA follow very close to the S/MPS (Intermediate

Minimum Property Standard, HUD) provisions in the introduction. However, there

is no recognition of ,. .providing equivalent safety.

The problem is complicated by the lack of definitive standards as to what constitutes acceptable double wall or equivalent protection as well as the lack of concise

definition of non-potable and toxic liquids. Standards for double wall designs

are currently being developed by American Society of Mechanical Engineers (ASME),

The Toxic Substances Control Act (P.L. 94-469; October 12, 1976) [34] authorizes

EPA to protect health and environment from harmful chemicals and mixtures (35).

33
The Act creates new requirements for testing, reporting and recordkeeping.

A preliminary listing of chemicals listed for further consideration (as toxic)

under that Act was published in July 1977 [36],

A summary of provisions directly related to solar energy installations is

included in Table 8. Survey of Recommended Installation Procedures for Heat

Transfer Systems and Heat Exchangers . [37]

Although there is considerable controversy and local exceptions, current enforcement by building authorities is following close to the attitude expressed in

these provisions. The Washington Surburban Sanitary Commission (WSSC) for example

takes a very similar approach to the problem "while awaiting more official

guidelines from the state" [38]. The WSSC plumbing board recently (June 1978)

passed a resolution permitting the use of propylene glycol as a heat transfer

fluid with single wall heat exchangers in solar DHW systems which are closed

loop systems with pressure fill requirements. Similar criteria are used in

approval of systems in which domestic water is heated by more conventional oil

or gas fired furnaces. If a toxic transfer liquid is used, double wall separation is required. If there is exposure only to the combustion gases or if a closed loop of stagnant water is used, double wall heat exchangers are not

mandatory.

An oil fired boiler by the New Yorker Steel Boiler Co. provides as an option a factory-installed tankless copper coil for domestic hot water. It is frequently

used (as are other makes) for outside installations for houses without flues or chimneys. The New Yorker Co. recommends propylene glycol inhibited with dlpotassium phosphate as a "non-toxic" heat transfer liquid in such installations. [39]

5.2 RELATED CODES AND STANDARDS

The following are citations from codes and standards regarding double-wall separation between potable and non-potable fluids in refrigerant systems.

1. ANSI A112.11.1, 1973 (ART Standard 1010-73), "Standard for Drinking

Fountains and Self-Contained, Mechanically Refrigerated Drinking

Water Coolers " [40]:

"4.4.3 - If a precooler is used, it shall provide more than a single thickness of metal between the potable water and the

waste water in the heat exchanger."

2. Military Specification, "Cooler, Drinking Water, Mechanically Refrigerated , Self-Contained, Naval Shipboard " 1965 [41]:

"3.10.1.1 - Refrigerant Coil . The Refrigerant coil shall be

nonferrous, external to the water storage tank and continuously

bonded to it. The use of additional refrigerant to water cooling

by means of tube in tube or tube on tube exchanger will not be

permitted. Sufficient coil surface shall be provided to permit

operation in accordance with the requirements of 3.12."

34
TABLE 8 - SURVEY OF RECOMMENDED INSTALLATION PROCEDURES

FOR HEAT TRANSFER SYSTEMS AND HEAT EXCHANGERS

(Excerpted from Solar Engineering Magazine, August 1977) [37]

HUD SMACNA lAPMO LOS ANGELES

INTERMEDIATE Installation Solar Mayor '

STANDARD Standards Code Committee Code

Piping

S-615: Refers to Pages 3-2: Page 36, Section

local plumbing Outlines basic 402B: Non-potable

code design information; water lines must

no standards or be posted, "Danger

codes given Unsafe Water,"

Pumps

S-515-6 and Pages 3-2,2:

Other pages list

acceptable piping

Page 25, Section

S-615-5: Shall Pump capacity 301: Components

be in compliance must match shall conform with

with the require- required head acceptable codes.

ments of the and gpm rules, regulations.

Hydraulic ordinances

Institute

HEAT TRANSFER FLUIDS

Separation

S-615-10.1.1

Systems must

have minimum

2 walls between

potable and nonpotable water...

( , , .or provision

for equivalent

safety)

None Pages 35-36

Sections 401 and

402: Direct

connections between potable and

non-potable lines

require backflow

prevention devices

Toxic Materials

S-615-8: Any

toxic solution

must carry a strong non-toxic

dye or other means

of leak detection

(and warning)

Page 8-1 : A

double wall heat

exchanger is mandatory with toxic

fluids

None A double wall heat

exchanger is mandatory with toxic

fluids (Manufacturer

must guarantee that

toxic fluids are not

used with single wall)

HEAT STORAGE SYSTEMS

Heat Exchanger

S-515-9 and

S-615-12: Manufactured by TEMA

requirements.

Double-wall between potable and

non-potable liquids

Page 4-2, Must be

manufactured to

comply with TEMA

requirement

Page 37, Section

403E: Copper tube

heat exchanger

bundle shall be

constructed of not

less than Type

L copper tube

Copper tube heat

exchanger bundle

shall be constructed

of not less than

Type L copper tube

35
"3.10.4 - A precooler, where provided, shall be constructed on non-ferrous seamless tubing. Both inlet and drain water passages

shall be fully enclosed with two walls of metal separating

the incoming drinking water from the drain water,

3. Chicago Building Code, 1976 [42]:

"Refrigerant Condensers, 83-44

Refrigerant Condensers. No refrigerant condenser of the water

jacket type with a common wall between the refrigerant gas and

the cooling water shall be directly connected to the city water

supply.

It should be noted that provisions for water cooler applications relate to circumstances in which there is direct and usually complete ingestion of the potentially

affected potable water. Although the level of toxicity of transfer fluids used

in these water coolers may not be as great as some used in solar assisted water

heaters, the probability of dilution is also less.

The regulatory control of refrigerants in various refrigerating systems offers

another comparison that is pertinent to the consideration of transfer fluids

and heat exchangers used with solar assisted domestic hot water systems. The

mechanical codes of the model code organizations [BOCA [32], Sect. M-803-805,

ICBO [43], Sect. 1503-1507, SBCC [44], Sect. 401-404) contain the following

provisions which are outlined here and cited below.

o Refrigerating systems are classified by the method employed for

extracting heat. (Determined by the directness the evaporate

refrigerant is in contact with the material or space refrigerant

is in contact with the material or space refrigerated)

o Refrigerants are classified and grouped by their toxicity or flammability. (ICBO uses two groups, BOCA and SBCC use the same but add a third group)

o The above classifications determine a variety of restrictions and

requirements

The BOCA Basic Mechanical Code, [32] 1978 Sections M-803.0, 804.0, 805.0,

(pp. 170 to 175) are Included in Appendix C.

The following definition of potable water and non-potable water and the provision

taken from Section 10.4 (Protection of Potable Water Supply) are taken from

the National Standard Plumbing Code [45] and are appropriate to state here.

(The same language is included in Section P-1605.0 of the BOCA Basic Plumbing

Code )

Potable water - Water free from impurities present in amounts sufficient to cause disease or harmful physiological effects and conforming in its bacteriological and chemical quality to the requirements of Public Health Service Drinking

Water Standards or the regulations of the public health authority having jurisdiction.

36
Non-potable water ; Water not safe for drinking, personal, or culinary use,

10,4,11 - Refrigerant unit condensers and cooling jacke t s

Excent where potable water provided for a refrigerator condenser

or cooling jacket is entirely outside the piping or tank containing

a toxic or flammable refrigerant as defined in ANSI B9,l, Paragraphs

5,1,2 and 5,1,3 with two (2) separate thickness separating the

refrigerant from the potable water supply, inlet connection

shall be provided with an approved check valve. Also adjacent

to and at the outlet side of the check valve, an approved pressure

relief valve set to relieve at five (5) psi above the maxi mum water pressure at the point of Installation shall be provided

if the refrigeration units contain more than twenty (20) pounds

of refrigerants.

The above definition of potable water is helpful but it does not necessarily

provide a definition of potable substances other than water. This also implies

that there is no standard definition for non-potable substances such as might

be used as heat transfer fluids in solar energy systems.

The precedent established by the classification and grouping of refrigerants

may provide a means of utilizing various heat transfer fluids by groups in

solar assisted domestic hot water systems with adequate safety. The precedent

of classifying refrigerating systems by type may also suggest requirements for

the extent of separation of solar loop fluids and potable water.

The separation of services such as water service piping and building drain

or sewer offers an additional point of view of protection by separation. Most

model codes require a separation by at least 10 feet of compacted earth between

these services.

The following provision related to fixtures and devices, including heat exchangers,

is cited in the proposed (1978) plumbing code by ICBO (International Conference

of Building Officials) [46] under Cross-connection Contro l.

Sec, 1604, (a) General, 1, Measurement, The minimum reauired air san shall be measured vertically from the lowest end of a potable water

outlet to the floor rim or line of the fixture or receptacle into which

it discharges,

2, Size, The minimum required air gap shall be twice the effective

opening of a potable water outlet unless the outlet is a distance

less than three times the effective opening away from a wall or similar vertical surface, in which cases the minimum required air

gap shall be three times the effective opening of the outlet. In

no case shall the minimum required air gap be less than shown in

Table No, 16-A,

(b) Devices, Approved backflow preventers or vacuum breakers shall

be installed with all plumbing fixtures or equipment, the potable

water supply outlet of which may be submerged and not protected by

a minimum air gap.

The potable water supply system shall be protected against backflow from the following fixtures or equipment by one or more backflow-prevention devices as indicated:

37
1. Low inlet to receptacles containins toxic substances

(vats, storage containers, plumbing fixtures);

a. An approved air-gas fitting,

b. Reduced-pressure unit.

c. Pressure vacuum unit,

d. Atmospheric vacuum breaker unit

2 . 3.

4. Coils or jackets used as heat exchangers in compressors,

degreasers and other such equipment involving toxic substances;

A. An approved air-gap fitting

B. Reduced-pressure unit

C. Pressure vacuum breaker unit

In section 1602, Installation-General, these provisions are made for protection

of the potable water supply and for the labeling and warning of non-potable

water lines.

4, Refrigeration Equipment, Except where potable water provided

for a refrigerator condensor or cooling jacket is entirely outside

the piping or tank containing a toxic or inflammable refrigerant

with two separate thickness of metal separating the refrigerant from

the potable water supply, inlet connection shall be provided with

an approved check valve. Also, adjacent to and at the outlet side

of the check valve, an approved pressure-relief valve set to relieve

at 5 psi above the maximum water pressure at the point of installation

shall be provided if the refrigeration units contain more than 20

pounds of refrigerants.

(f) Identification. In all buildings where dual water-distribution

systems are installed, one potable water and other non-potable water,

each system shall be identified either by color marking or metal tags

or other appropriate method such as may be approved by the building

official. Each outlet on the non-potable water line which may be used

for drinking or domestic purposes shall be posted; DANGER-UNSAFE WATER

5.3 CURRENT ACTIVITY AND RESEARCH

Sandia Laboratories is currently revising an interim report which will be titled

"Hazardous Properties and Environmental Effects of Materials Used in Solar

Heating and Cooling (SHAC) Technologies" [13], A draft report has been circulated for comments and contains useful information on toxicity and other characteristics of a large number of chemicals used as heat transfer fluids, fluid

treatment, thermal degradation and outgassing products. Much of this Information

has been taken from work cited earlier in this report (Gosselin et al and Durham),

[5, 6] excerpts of which are included in the appendix.

The objective of the Sandia report is to ultimately provide a handbook of

hazardous properties and environmental effects of potential SHAC materials.

38
The intent is to produce a handbook that layman and professional alike can use

as a guide in selecting materials for the various SHAG techniques.

Research is underway at Lovelace Biomedical and Environmental Research Institute,

Albuquerque, New Mexico on the toxicology of solar heating and cooling materials.

This work, supported by the Department of Energy (DoE) addresses itself to the

need for characterization of toxicity under normal and abnormal conditions such

as combustion and over pressure. The objective is to conduct hazards assessment

as needed to define and quantify health effects associated with the large-scale

utilization of solar heating and cooling.

This research should add significantly to the knowledge of toxicity of fluids

used in solar energy systems and should provide an assessment as to the accuracy

of literature on the effects of ingestion of these materials.

The American Society of Mechanical Engineers (ASME) has established a Solar Energv

Standards Development Committee which in its scope includes:

"the preparation of a standard for design, materials, fabrication,

installation and testing of solar collectors, thermal storage

subsystems, energy transport subsystems, heat exchangers, pumps,

fittings and valves."

The subcommittee (of the Standards Development Committee) concerned with heat

exchangers is active and has taken the direction of seeking classification

of heat transfer fluids into three groups and will attempt to determine heat

exchanger design standards which correspond to the hazard level established

for these vrouos. General discussion has suggested the following groups although

there is apparent difficulty in defining adequate heat exchanger protection

as well as leyels of toxicity.

HTF GROUPS

(A) Potable Fluids

(B) Non-potable, practically

non-toxic fluids

(C) Toxic fluids

HEAT EXCHANGER PROTECTION

(1) Single wall with no (leak) detection

(2) Double wall with no (leak) detection

(3) Single wall with (leak) detection or additional level of protection

(4) Double wall with (leak) detection or additional level of protection

Defining non-toxic as distinguished from non-potable fluids is also difficult.

The Federal Hazardous Substances Act specifies that:

"The term ’toxic’ shall apply to any substance (other than a radioactiye substance) which has capacity to produce personal injury

or illness to man through ingestion, inhalation or absorption through

any body surface,"

Referring to definitions for potable and non-potable water stated earlier in this

report it is difficult to discern any clear difference between the definitions

of "non-potable" and "toxic".

39
5.4 need for safety GUIDELINES

The solar energy industry represents a new and emerging technology. In spite of its

successes, some technical problems still need to be solved. The heat transfer

medium and the heat exchanger are among the more significant components of the

individual systems. If unduely restrictive requirements are placed on these or other major components progress could be restrained. On the other hand, these

components may constitute a real hazard in some systems, A serious breach of

safety would not only be a threat to individual health but to the credibility

of solar technology. This dilemma requires thorough consideration to assure reasonable cost effective solutions with adequate protection of life and health,

"It is very difficult for the system designer to assess the safety of the heat

transfer fluids that are currently on the market. It is also very difficult

for the designer to determine the safeguards that must be taken to ensure safe

system operation. Data are available in the literature that rank various heat

transfer liquids on the basis of their relative toxicity. However, these data

do not indicate the cut-off points at which various degrees of protection must

be taken. For example, a number of the toxicity tables list propylene glycol as slightly toxic, A substance with such a ranking most likely does not fit under

the definition of potable in which case no safety precautions need to be taken,

yet it is not as hazardous as many other substances that are used in heat transfer

fluids. This problem is compounded by factors such as: (1) the use of additives

to modify fluid properties; (2) the possible formation of harmful decomposition

products, e,g,, by thermal degradation; (3) the fact that liquids are generally

available in varying grades of chemical purity; (4) the possibility that the

system will be refilled in the future with a hazardous liquid; and (5) the

possibility that circulation in a closed loop system for prolonged periods of

time will eventually result in the contamination of potable liquids, e,g,, by

metal ion buildup," [4]

Adequate precedents exist in related systems such as refrigeration systems

to establish a concept for safety guideline for these solar energy components.

Many of the same trades and individuals familiar with conventional mechanical

systems will be involved with the solar energy systems. There is a safety

margin to be gained by remaining consistent with established criteria.

Strong consideration should be given to creating an informed and responsible

public. An assessment should be made of probable owner involvement with the

maintenance and operation of the solar energy systems. Creating a foolproof

system may not be necessary or even desirable. With proper instruction,

operating manuals, labeling, tagging, etc., it is not unreasonable to expect

a responsible role for the home owner or occupants in regards to inspection

for leaks, malfunctions, potential hazards and assuring against the use of

improper fluids. Again, there is a margin of safety to be gained developing

owner and public awareness and creating an attitude for responsibility. It

is when people are unaware that they are most vulnerable,

6, SUMMARY AND RECOMMENDATIONS

Findings : The need to utilize a heat exchanger fluid other than water in solar

hot water systems coupled with the lack of service experience of these systems

has raised an important safety issue with regard to the design of the heat

40
exchanger in the collector/storage loop. That is, possible contamination of

the potable water supply if failure of a heat exchanger should occur. The level

of protection might be developed in keeping with the level of the hazard, but

it is important that the complexity of the hazard is not overlooked. These

complexities include; the combined effects of a mixture of toxic fluids, volume

of contaminant leakage, and dilution within the potable water. It seems appropriate that individuals with training in health and medicine be included in

the determination of the hazard level. Risk analyses which include the extent

of the hazard as well as the probabilities of failure of the heat exchanger

components, pressure differentials and leak detection would be in order.

The margin of safety may be increased by use of back-up measures and fall-safe

devices with little increase in cost or effort. These include measures such

as; a concentrated tracer dye, pressure drop safety switch and contamination

detection safety switch. Warning labels or tagging as well as special fit design

of the fluid filler cap will add further to the safety margin.

The objective of this study was to review available information of a technical

and regulatory nature relative to the issue which may provide a basis for evaluating solar heat exchanger designs. Another objective was to identify areas

of needed research.

The findings of this study relative to this issue are as follows:

A. A clear definition of toxicitv which can be uniformly applied is

lacking. Test methods which can evaluate the hazard associated

with the accidental missuse of heat transfer fluids are not available.

B. Currentlv available standard tests for heat transfer fluids to evaluate

both short-term and long-term effects may not be applicable to solar

equipment operating conditions. Tests are needed in the area of cor- rosivity and degradation of the fluids over time.

C. Generally, building codes contain little in regard to the heat

exchanger toxicity question. Those regulations which are available

are inconsistent.

D. An insufficient data base is available for the satisfactory prediction

of the loss of thermal efficiency when using a "double-wall" heat

exchanger as compared to "single-wall" construction in the same

system.

E. The historical development of "double-wall" construction in the

refrigerant system of drinking water coolers demonstrates the

precedent for a conservative approach to the problem of potential

contamination of potable water in a solar hot water system as long

as failure rate of the materials involved and service life of the

system cannot be documented.

F. Even though a solar hot water system is designed to use a "nontoxic" heat exchanger fluid, consideration should be given to the

possibility that a "toxic" fluid could inadvertently be installed

at a later date. .. _ 41
G, There is concern that "non-toxic" fluids will become toxic by the use

of contaminating additives, decomposition products or from impurities

within closed loop systems. There is also concern that the quality or "purity" of some fluids used in solar energy systems may be inferior

to those for which toxicity ratings are given or those used in other

processes such as food production,

H, Data accumulated during the study will not allow a quantification of

"equivalent safety", as specified in Criterion 4,6,2 of the IPC [2],

It is recognized that systems could utilize leak detection techniques

such as color change detection, pressure change detection, contamination detection or other means to determine when a heat exchanger has

failed and perhaps deactivate the system. These should be evaluated

on a case-by-case basis,

I, The selection of a heat transfer fluid requires the consideration of

several variables which have impact on system design. No single heat

transfer fluid is optimal in all the desired characteristics and tradeoffs should be considered. For example, the desirable property of

low toxicity may be offset by high viscosity which may require the

increased cost of a larger pumping capacity and piping system,

J, While the design pressure in the collector/storage loop is usually

lower than that in the hot water storage tank and therefore would tend

to keep the heat transfer fluid in the collector loop from mixing com- pletely with the potable water in the tank in the event of a wall

rupture; this is not sufficient protection because it does not accommodate the emergency situation of a loss of city water pressure,

K, There is no direct data available to determine the cost impact

of "double wall" heat exchangers,

RECOMMENDATIONS : While this state-of-the-art study has identified a large

amount of data relative to solar heat exchangers, considerable data are still

needed before a less conservative approach relative to Criterion 4,6,2 can

be taken. At the present time, approval for the use of liquids other than

potable water (or documented non-toxic fluids) in conjunction with single wall

heat exchangers should be on a case-by-case basis.

Efforts at this time should be placed on the "double failure" concept to provide

equivalent protection, A closer correlation between health risk and protection

level should be sought. Trade-offs between, heat exchanger protection, transfer

fluid toxicity and effectiveness and double failure Innovations should lead to

cost effective designs for solar DHW systems with retention of high safety standards, As results are obtained from the efforts to classify and group heat transfer fluids and to assess their toxicity under actual operating conditions, the

current criterion may be relaxed. Data relative to toxicity, corrosivity, thermal

efficiency, etc,, can be obtained in part by conducting research listed below,

as well as, from documentation of system performance in the DoE and HUD Solar

Demonstration Programs.

Specific research and standards needs are as follows:

42
1. Thermal performance of "double-wall" heat exchangers as compared to

"single-wall" designs in similar systems. Theoretical predictons should

be validated by laboratory testing,

2. Tests methods and standards for evaluating the characteristics of

heating transfer fluids such as toxicity, long-term degradation etc,

should be developed,

3. Long-term effects of heat transfer fluids on the solar system components

(heat exchanger, piping, etc,) should be studied and uniform methods

of evaluation developed.

4. Work should be continued in the development of uniform building regulations

relative to the safety of solar energy systems.

43
REFERENCES

1. "Interim Performance Criteria for Solar Heating and Combined Heating/Cooling

Systems and Dwellings," National Bureau of Standards, Washington, D.C,

January 1, 1975, (Available through Superintendent of Documents, U.S,

Government Printing Office, Washington, D.C. 20402, Stock No. 0324-01043).

2. "Interim Performance Criteria for Solar Heating and Cooling Systems in

Commerical Buildings," National Bureau of Standards Report NBSIR 77-1187,

November 1976 (Available from NTIS, Order No. PB-262-114).

3. "HUD Intermediate Minimum Property Standards Supplement - Solar Heating

and Domestic Hot Water Systems," U.S. Department of Housing and Urban

Development, 1977 Edition.

4. Waksman, David and Holton, John., "Environmental and Safety Considerations

for Solar Heating and Cooling Applications," (publication in preparation)

National Bureau of Standards, Washington, D.C.

5. Durham, W.F., "Toxicology" in Dangerous Properties of Industrial Materials , 1975, (Sd) N. I. Sax, ed. Van Norstrant Reinhold Co., Baltimore, Maryland.

6. Gosselin, Hodge, Smith and Gleason, "Clinical Toxicology of Commercial

Products," 1975, 4th edition, Williams and Welkins Co., Baltimore, Maryland.

7. Registering the Toxic Effects of Chemical Substances , HEW Publication No.

(H 10 SH) 76-191, 1976 Edition.

8. Registry of Toxic Effects on Chemical Substances , Christensen, H.S. and

Fairchild, E.J., National Institute for Occupational Safety and Health,

U.S. Department of Health, Education, and Welfare, Rockville, MD, 1976

Edition.

9. "Evaluation of Backflow Prevention Devices: A State-of-the-Art Report,"

National Bureau of Standards Report NBSIR 76-1070, June 1976.

10. Safe Water Drinking Act, Public Law 93-523, 40 FR 11990.

11. National Interim Primary Drinking Water Regulations, Federal Register,

December 24, 1975.

12. National Secondary Drinking Water Regulations, Federal Register,

March 1977.

13. Searcy, J. Q. , "Hazardous Properties and Environmental Effects of Materials

Used in Solar Heating and Cooling (SHAC) Technologies," rough draft, Sandia

Laboratories Interim Report, SAND 78-0842, June 1978.

14. Energy and Environmental Analysis, Inc., Draft Environmental Impact

Statement of the National Solar Heating and Cooling Program, draft

report for the Department of Energy, December 1977.

44
15 .

16.

17.

18.

19.

20 .

21 .

22 .

23.

24.

25.

26.

27.

28.

29.

30.

Benyon, Eric, Inhibited Ethylene Glycol as thp Mqvho " t .. Corrslon Foru., San FranclsL, Callfo?nl" ^rcfl977

’

'Glycols!'^

Second Edition (1962), Chapter XXXV,

"Dangerous Properties of Industrial Materials Reinhold Publishing Corporation, New York (1957),

*

J.^C. Harms, A.O. Smith Manufacturing Co, private communication, July

Zn®WeSrrLns,°?nc!"‘°" Control, Second Edition,

Hatch, George B., "Inhibitors for Potable Water ” rr»rT-r>c-i ^r. t u • .. National Association of Corrosion EngLe:r!:l';sto:r?eL“,

ASHRAE Handbook of Fundamentals, American Socletv of Hpar-fno o e ^ and Mr-Condltlonlng Engineers

, ’inc. , 345 Kt^1^th^t"re\“:*Ne„^1:Jf:^

Co^ra^rr El-7l%"5^:28^Jrsf°tf:h"r

American

Hargis, Alice M., Beckman, Arthur, Lolscono, John, "The Plate Heat Exrhan,^,-" Society of Mechanical Engineers, 1966.

Exchanger ,

Solar Hot Water Packages, Solar Engineering Magazine, March 1978.

B. H. Williams, Dairy and Food Industries Supply Association, private communicatxon, January 17, 1978.

Se^lfri'im^L^^onf C>«^hangers for Milk and Milk Products

Vor35!^No!ir"'^'^ Technology, ’March 197^

"

NBSIR 76-1082, "A Survey of State Legislation Relating to Solar Energv " Robert M. Eisenhard, National Bureau of Standards, April 1976.

’

NBSIR 77-1279, "State Solar Energy Legislation of 1976; A Review of Statutes

September 1977! "*^’" National Bureau of Standards,

45
31. City of Los Angeles, "Guidelines for Laboratory Approval of Solar

Systems," (proposed rule of general application—public hearings held on July 12, 1977) Department of Building and Safety, 402 City Hall,

Los Angeles, California 90012.

32. Basic Mechanical Code, Building Oficials and Code Administrators, 1978.

33. "Heating and Air-Conditioning Standards for One and Two Family Dwellings

and Multifamily Housing Including Solar," Sheet Metal and Air-Conditioning

Contractors National Association, Inc., 1977,

34. Toxic Substance Control Act, Public Law 94-469, October 11, 1976,

35. Christensen, Herbert E,, and Lugenby D., Thomas T., editors, "The Toxic

Substances List 1974 Edition," U.S, Department of Health Education and

Welfare: Public Health Service, Center for Disease Control, National

Institute for Occupational Safety and Health, June 1974,

36. "Preliminary List of Chemical Substances for Further Evaluation," Toxic

Substances Control Act Interagency Testing Committee, U.S, Environmental

Protection Agency, Office of Toxic Substances, July 1977.

37. Solar Engineering Magazine, August 1977,

38. L. G. Norrington, Washington Suburban Sanitary Commission, private

communication, February 1978.

39. Steve Amicone, New Yorker Steel Boiler Co, , Colman, Pa, private communication,

February 1978.

40. ANSI A112.11.1, 1973 (also ARI Standard 1010-73), "Standard for Drinking

Fountains and Self-Contained, Mechanically Refrigerated Drinking Water

Coolers.

41. Military Specifications, "Cooler, Drinking Water, Mechanically Refrigerated,

Self-Contained," Naval Shipboard, MIL-C024116A (SHIPS).

42. Chicago Building Code, Volume 23, Paragraph 83-44, 308 West Randolph Street,

Chicago, Illinois 60603, February 1976.

43. Uniform mechanical Code, International Conference of Building Officials

(ICBO), 1976.

44. Southern Standard Mechanical Code, Southern Building Code Congress (SBCC),

1976.

45. National Standard Plumbing Code, National Association of Plumbing-HeatingCoollng Contractors, 1978.

46. Plumbing Code, draft of proposal. International Conference of Building

Officials (ICBO), first printing 1978,

46
^jpendix A - Illustrations of Heat Exchanger Types

Wee-t #ImicI

utmirfir barter

toe.KT»*M Di*»6,rAi.h

be^ic. «ualt

hea-t «xc.h«i^frr

Tuec IK ^H€.U_

Dcueue Tuee. m Shcll

^P»R/<LC.O INKIC.R ToBK

-it

A-1
>

Loc.Ak'Moh Di^ crkh

ufoirer lie»+er

AT

au)tilisiri( ujm'ter h«»ter

Loc./k'TIOM

W/////7!^.

.M—'UTW hamtj

Liquid to LiQWto
Tubs.% ^ Fims

C fih ooiO

TR»PUE- Tubgl

A-4


APPENDIX B - TOXICITY STUDIES OF HEAT TRANSFER FLUIDS AND CCMMON ADDITIVES^^

Table E-1

Toxicity of Heat Transfer Fluids

CHEMICAL SUBSTANCE

(GENERIC) PRODUCT

Ammonia

NH,

anhydrous

TOXICITY RATING*-GOSSELIN^^^^i

TOXICITY RATING

TOXIC HAZARD RATING®

DURHAM^^®*

Acute Chronic

Irritant

Inqestion

Inhalation

Skin absorption

Bromides Irritant

Ingestion

Inhalation

1

2 2

2

1 2

2

Chlorodifluoromethane Freon 22

Syn; Freon 22 CIHCF^

Toxicity:

Asphyxlnnt in

high cone.

Dichlorodi f luoroinothane

Syn.: Freon 12 CCljFj

Freon 12 Irritant 0 U Ingestion 0 Inhalation 0 1 Skin absorption 0

U

U 1 U

Dichlorotetra- Freon 114

fluoroe thane

Syn.: Freon 114

F^ClCCClFj

Irritant 1 0 U Ingestion

Inhalation 1 1 Skin absorption

U

UU

U

U

U

Di ethylene Glycol^

Syn.S diglycol

CHjOHCH^OClljCHjOII

Oral-human /an.

LDjq 1000 mgAg' ' 3 Irritant 1 1 U Ingestion 2 Inhalation 2 Skin absorption

UU

U

Dipropylene glycol

Syn.: 2,2’-

dihydrcxyi sopropyl

ether

(CIt3CIIOHCH2)20

Oral-rat

LDjq 15 gm/lg (81)1 Irritant U U Ingestion U 2 Inhalation U Skin absorption U

U 2 U 1 U

F.thyJcne Glycol

Syn.; I » I-cth.nncd j ol: glycol; ethylene

alcchnl; glycol

alcohol

CH^OHClIjOJI

^owtherm

SR-1; UCAR-

’‘thernof luid

17

Oral -human

LDLo 1500 ng/kg

Oral -rat

r,D,. 5840 mg/kg

(81)

(81)

—^Extracted from reference [13], Sandla Laboratories, SAND 78-0842, 1978

Irritant low

Ingestion low 3 Inhalation low

Skin absorption low

1

2

* Commonly used manufacturer's fluids

^Durham: 0-none; 1-sllght; 2-moderate; 3-hlgh; U-unknown. Gosselln “ 1-practlcally nontoxic; 2-sllghtly toxic; 3-moderately toxic; 4-very toxic; 5-extremely toxic; 6-supertoxlc (See Section 13).

'^Suspected carcinogen of bladder (1). '^Experimental carcinogen (1). '^References 7S a.. .9 of the report cited above correspond to references 5 and 6 of this report.

B-1
CHEMICAL SUBSTANCE

(GENERIC) PRODUCT

TOXICITY RATING^-GOSSELIN^^^^

TOXICITY RATING

TOXIC HAZARD RATING^

DURHAM

Acute Chronic

Ethylene Oxide^ * UCON 30 Oral-rat .gj^, Syn . : l.Z-cpoxy*- ^*^50 n>g/Jcg 4 ethane oxirane

(ClI^) 2°

Irritant 3 2 U Ingestion

Inhalation 2 Skin absorption

U

U

U

Fluo rotrlchloro- Freon 11 methane

Syn.: trichlorof luoromethane

FCClj

Irritant 1 Ingestion 1 Inhalation 2 Skin absorption I1

1

2

1

Glycerine Oral -guinea pig

LDjg 77S0 mgAg '

' 2 Irritant

Syn . : 1,2, 3-propanctriol; glycerol

CH

2OJICHOHCH

2OH

Ingestion

Lithium Bromide

LiBr See bromides £ lithium compounds

Lithium Chloride

LiCl -lljO

Oral-rat

LD^q 757 n.g/kg 3 See lithium com- pounds

Lithium Compounds Irritant 2 U Ingestion

Inhalation

Skin absorption

3 U

2 U

U

2

2

Mot hanol

Syn.: metltyl alcohol

enroll

Irritant 1 Innention 3 Inlialation 1 2 Skin absorption 21

1

22

2

rhciiyl other-diphenyl *Dowtherm A Oral-rat

mixture LDLo 4380 mg/kg 3 »’ol to'^t- but mildlv

Irritant

B-2
CHEMICAL SUBSTANCE

(GENERIC) PRODUCT

TOXICITY RATING*-GOSSELIN^^^^

TOXICITY RATING

Polyethylene glycol UCON 50-

Syn.: Antifreeze HB-280-X

E400

E600

E6000

Oral-rat fai\

LDjq 6130 mgAg 222

1

TOXIC HAZARD RATING^

DURHAM^^®'

Acute Chronic

U V H

E e

0-i t) u « tz 0 Vs c 0 >,

tn ^

Propylene Glycol Dowfrost;

Syn. : 1, 2-propanediol;*UCAR Food

1, 2-dihydroxypropane Freeze 35

CHjOIlCHOHCHj

Oral -rat

LDjq 21 gmAg

Oral mouse “so gmAg

(81)

(81)

1 Irritant 1 Allergen 1 Ingestion 1 Inhalation

Slcin absorption

11

1

d

Propylene Oxide OCON L20

Syn . ; 1 , 2-epoxypropane: propene oxide

methyl oxirane

OCH^CHCHj

Oral -rat

LDjq 930 mgAg

Oral-guinea pig

LDjq 690 mgAg

(81)

(81) 3

Irritant 2 1 u Ingestion 2 Inhalation 2 Skin absorption

U

U

u

Silicone Oil

Syn.: Dimethyl

polysiloxane

Dow Corn- No unequivocal toxic

ing 200 effects are recognized

Sodium thiocyanate

Syn. : Sodium Sulfocyanide

NaSCN

Oral -rat

LDjq 764 mgAg

Oral -rabbit

LDLo 750 mgAg

Oral mouse

LDLo 290 mgAg

(81)

(81)

(81)

3

3

4

Irritant U U Ingestion U 3 Inhalation U

Skin absorption U

U 2 U

U

m-Terphenyl ’^herminol 66

Syn.: m-phcnylbiphenyl; benzene- 1,

3-d ipljcnyl

«V'5>2V'4

Irritant U U Ingestion U 2 Inhalation U 2 Skin absorption U

U 2 U

U

Triethylene glycol

Syn: 2 , 2 ' -ethylene

dioxydiethaiic*! ;glycol;

bi s (hydroxycthyl

ether

(CIl20Cll2CH20!l)j

Oral-mouse fail

LDjq 18500 mgAg' ' 1

B-3
CHEMICAL SUaSTANCE

(GENERIC)

Tri fluorot rich loroethane

Syn.< Freon 113

CCl jCF^

PRODUCT

TOXICITY RATIWG*-G0SSEL1N^^^^

TOXICITY RXTmC

Freon 113

TOXIC HAZARD RATING*

OURHAM^^®^

Irritant

Acucc Chrrr.ic

Xngeatlon 0

Inhalation U Skin absorption 0

2 U

0u

uu

u

^Durham: 0-none; l-slight; 2-jt»derate; 3-high; U-unknown. Gosselin 1-practically nontoxicj 2-6lightly toxic; 3-moderatoly toxic; 4-very toxiei 5-e*tre»ely toxic; 6-tupertoxic (See Section 13)

^Suspected carcinogen of bladder (81)

^^Experimental carcinogen (81)

^^Experimental carcinogen (81) .

B-4
Table B-2

Toxicity of Fluid Treatment Chemicals

CHEMICAL SUBSTANCE

(GENERIC) PRODUCT

Arsenic Compounds^

Benzotriazole

Boron Compounds

Chlorinated Phenols

ChroBiiuni Compounds

2-cthy) Jiozanol

Syn.: 7-ethyl

alcohol

Hypochlorites

Lithium Chromate

Li jtrO^. 211^0

TOXICITY RATING* -GOSSELIN*^^^

fcnrrcTTY

Oral-rat jou

LDLo 500 mgAg 3

Oral-rat

LDj^p 3200 mg/kg'"*'

Oral -mouse LDg^ 3200 ng/kg‘"^'

TOXIC HAZARD RATING*

DURHAM^^®^

Acute Chronic

mHc

u0

1-9

Systemic

j

Loca

1

I

u

H

E0P

Cft >1A

Irritant 2 2 Allergen 2 2 Ingestion 3 3 3 Inhalation 3 3

Irritant U 0 Ingestion 2 U 0 2 Inhalation 2 U 0 2 Skin absorption U 0 2

Irritant 3 u Allergen u Ingestion 3 3 U 3 Inhalation 3 3 U 3 Skin absorption 3 U 3

Irritant 3 U 3 U Ingestion 3 U 3 3 Inhalation 3 U 3 3 Skin absorption U

Irritant 2 U U

U u Ingestion 2 U u Inhalation 2 U u Skin absorption U u

sec chromium

compounds

B-5
CHEMICAL SUBSTAKCE

(GENERIC)

TOXICITY RATING* -GOSSELIN^^*'

PRODUCT

TOXIC HAZARD RATING*

DURHAM^^®^

Acute Chronic

u

E

0 c

u 0) c >«

Lithium Com;x>unds Irritant 2 Allergen

Ingestion 3 Inhalation 2 S)cin absorption

Lithium Hydroxide

Syn.: Lithium hydroxide

monohydrate

LiOH

Lithium Nitrate

LiNO^

Mercaptans

Mercury compounds,

organic

Nitrates

Ni trites

Very caustic

« toxic. See

lithium com- pounds i sodium

hydroxide.

see nitrates

Irritant 3 U

Ingestion

Inhalation

Skin absorption

Irritant 3 Allergen 2 Ingestion 3 Inhalation 3 Skin absorption 2

23

3

33

Irritant u u Ingestion

Inhalation

Skin absorption

U 2 U 2 U

Irritant U u Ingestion U

Inhalation U

Skin absorption U

3

3 U 3 U 3 U

B-6

Txacn 1 Systemic
CHEMICAL SUBSTANCE

(GENEniC) PRODUCT

Pal athion

Syn.t 0,0-diethyl 0-Pnl trophcnyl thlophoephate; "Alkron"

TOt->pound 3422? DNTP; DrP; E-605;

genlthion; niran;

paradust; paraflow; > paraspray; parawetj

penphon; phos-kll

thiopt»sj vapophori

and many others

Pentachlorophenol

CL^CgOU

Phenylmercurie

t riothanol

airrioninm lactate

Dowicidc G

TOXICITY RATING*-GOSSEI,IN^’®^

toxieiTV RJrlTj!?

Oral-human

LDLo 240 tng/kg

Oral -rat

(81)

o-Phenyl phenol

Phosphates, organic

Polassiuo Ai senate

Syn; potassium

dihydroqeri arsenate;

P.acquer's salt

KII,AsO.

Potassium di chromate*

Syn.s tolansium bichror.wTie; red

p<«tas:; lum chromate

K^Cr^Oy

I*>^50 2 mgAg (81)

Oral -human

LDLo 29 mgAg'

Oral-rat .... W>50 50 mgAg'"*'

Oral-rat

*'*'50 mgAg**'^

Dowicide 1 Oral -rat

LDjq 2700 mgAg (81)

Oral -human child

LDLO 50 mgAg^®^'

TOXIC HAZARD RATING

,(78) DURHAM’

Acute Chronic

IQ0

0U in

Irritant U Ingestion V

Inhalation U

Slcln absorption V

Irritant

Ingestion

Inhalation

Skin Absorption

See mercury com- pounds, organic

Irritant

Ingestion

see parathion

Arsenic com- pounds

Sec chromium com- pounds .

B-7

Loca

I

Sy

s

tenue
CHEMICAL SUBSTANCE

(GENERIC)

TOXICITY RATINg“-GOSSELIN^’**

PRODUCT TOXiClW" RATlNff

TOXIC HAZARD RATING

DURHAM

Acute Chi;onic

•Q I

Potassiun Hydrogen

Phosphate

Syn.: potassium

phosphate, dibasic

K2«P0^

Sodium Benzoate

Syn. : Benzoate of soda

NaC^HjOj

Sodium Borate

Syn.t Sodium tetra*

borate

Na2B^0.^

Oral -rat

LDjjj 4100 mgA9

Oral-rabbit

LDLo 2000 agAg

(81)

(81)

Sodium Chromate

Na^CrO^

Sodium Hydroxide

Syn.: Caustic soda;

Sodium hydrate: lye:

white caustic.

NaOH

Sodium Hypochlorite

NaClO

Sodium Metasilicate

Sodium Nitrate

Syn.; Soda niter:

nitratinc

NaNO,

Sodium- o- Phosphate

Syn.: trisodium

phosphate

Na^PO^-12 lIjO

Sodi'jm Sulfate

(Sol. Sulfate Salts

of Sodium)

Oral-rabbit

LDLO 500 mgAg (81)

Oral-rat

LDj.q 1280 mgAg (81)

Oral -rat

LDLo 200 mgAg (81)

Atmount of r.ulfate

anion usually absorbed

has no toxifoloejical

significance.

Toxic hazard

rating: U

Irritant

Ingestion

Inhalation

00

Slcin absorption 0

See boron com- pounds

See chromium

compounds

Irritant

Ingestion 3 Inhalation 2 Skin absorption

See hypochlorites

See nitrates

Irritant

Ingestion

Inhalation

S)tin absorption

B-8
CHEMICAL SUBSTANCE

(GENERIC) PRODUCT

TOXICITY RATING*-GOSSELIN^’*^

WxTCItY RAflHir

TOXIC HKZARD RATIVG®"

Acute Chronic

o U

•MB C o « O

c C o cn 0 c 0 >.

¥-^ M y;

Sod i un 2, 4, St r i c h 1 orophenoDovicide B Oral-rat

LDjq 1620 3

.3,4.6-

tr1 ch 1 oropheno

Dowicide 6 Oral-rat

LDjq 140 ingAg (61)

Oral-guinea pig

^'^SO »9Ag (81)

4

See Chloronated phenols

See chlorinated phenols

2.4,5-

trichlorophenol

Dovicide 2 Oral-rat • LOjjj 820 mgAg'®^' 3 See chlorinated phenols

2,4.6-

trichlorophenol g

Dovicide 2S Oral-rat ....

LDjjj 820 »gAg*"*' 3

See chlorinated phenols

*Durhaia: 0-none; l-slighti 2-moderate; 3-hlgh; U-unknovn. Gosaelin “ 1-practically non--toxic;

toxic; 2-slightly toxic; 3-iDoderately toxic; 4-very toxic; S-extremely toxic; 6-supertoxic (Sec Section 13)

^Recognized carcinogen of akin (81)

*So»e chromium salts are recognised carclnogena (81)

^Recognized carcinogen*^

^Recognized carcinogen (81)

^Recognized carcinogen (81)

^Carcinogen (81)

B-9
Table B-3

Toxicity of Outgassing Products from Heat Transfer Liquids

TOXtC ll,'.7.Apn RATlNt;'’'

riUPIIAM (70)

OUTGASSING SUBSTANCE

(GENERIC)

FROM TOXICITY RATING^-GOSELLIN*’®^ Ai'ti 0 Oil «M1 i c PRODUCT TOXlclTY RAfirlS"

u u

e c 0 4) u

0 v> u

0 0

,4 W (/)

Argon SF 96, silicone; Irritant 0 U u A Exxon Caloria Ingestion 0 u u HT 43; UCON Inhalation 0 1 u u 500; Therininol

66; Mobiltherin

£0 3; Mobil therm

Light; Dowtherm

A

S)cin absorption 0 u u

Carbon Dioxide SF 96, silicone; Irritant 0 0 CO, UCON 500; Exxon Ingestion 0 0 Process Oil 3029; Inhalation 0 1 0 1 Exxon Caloria HT43; Dowtherm A; Therminol 66;

Mobiltherm 603;

Mobil therm Light

Skin Absorption 0 0

Carbon Monoxide SF 96, silicone; Irritant 0 0 CO UCON 500; Exxon Ineestion 0 0 Process Oil 3029; Inhalation 0 3 0 1 Exxon Caloria liT- 43; Dowtherm A; Therminol 66;

Mobiltherm 603;

' Mobiltherm Light

Skin absorption 0 0

Ethane SF 96, silicone; Irritant 0 0 Syn.: bimethyl; Exxon Process Oil Ingestion 0 0 me thy Ime thane; 3029; Mobiltherm Inhalation 0 2 0 1 dimethyl; 603; Mobiltherm Skin absorption 0 n ethyl hydride

^2«6

Light

Ethylene SF 96, silicone; Irritant 0 0 0 Syn. : ethene; UCON 500; Exxon Ingestion 0 0 0 elayl; etherin Process Oil 3029; Inhalation 0 2 0 0 CHjCHj Therminol 66; Skin absorption 0 0 0 Mobiltherm 603;

Mobiltherm Light

Hydrogen SF 96, silicone; Irritant 0 0 0 “2 Exxon Process Ingestion 0 0 0 Oil 3029; Exxon Inhalation 0 1 0 0 Caloria HT-43;

Therminol 66;

Mobiltherm 603;

Mobiltherm Light

Skin absorption 0 0 0

B-10
OUTGASSING SUBSTANCE

(GENERIC)

Methane

Syn.i marsh gas;

methyl hydride

FROM

PRODUCT

TOXICITV RATING^-GOSSELIN^^®*

Toxicirt Rating

TOXIC HAZARD R.^TINC^

durha:i ^^^^

Acute Chro'

n

SF 96, silicone;

UCON 500; Exxon

Process Oil 3029;

Exxon Caloria HT43; Dowtherm A; Therminol 66;

Mobiltherro 603;

Mobiltherm Light

Irritant 0 Ingestion 0 Inhalation 0 1 Skin absorption 0

0

00

0

Nitrogen SF 96, silicone;

N, Exxon Process Oil

^ 3029; Exxon

Caloria HT-43;

Dowtherm A; UCON SOO; Therminol

66; Mobiltherm

603; Mobiltherm

Light

Toxicity: None

^Durham: 0-none; 1-slight; 2-moderate; 3-high; U-unknown. Goeselin 1-practically non-toxic;

2-slightly toxic; 3-moderately toxic; 4-very toxic; 5-extremely toxic; 6-super-toxic.

; <

B-11
Table B-4

Toxicity of Thermal Degradation Products

CHOaCAL SUBSTAMCE (ccNrmc)

Aistonia, anhydroua

$yn.

anaonia qaa

rKODUCT

Nylon t,6

TOXICITY »ATmC*-G08»eLIN<’*>

foxIcIT? KatTOC

TOXIC HAIAIU) RATING*

DllRHAW*^** Acuta Chrcnte

Irritant 3 0 Ingeatien 3 U Inhalation 3 0

Skin abaorptlen 0

u

r

•* <1

5

1

>•

<A

VV

u

u

henaane^

Syn.: benzol > phenyl

hydride] coal naphtha

Ceon] Halont Plexiglaas;

Lucitc; PVC] Neoprene t Nylon HT-4

Irritant 2 . Znqeatlon 1 , Inhalation 1 1 Skin abaorption

0

0 3 0 3 0 3

Butadiene-1,3 Neoprene

Uninhibited

Syn.t erythrene

CHjCHCHCHj

Irritant 3 Invention 2 Inhalation 2 2 Skin abaorption1 U

Uu

u

Carbon Dioxide Nylon C,C; Syn.: carbonic acid: Nylon HT-4

carbonic anhydride

Irritant 0 Invaatioo 3 Inhalation 0 1 Skla abaorption 000

00

1

Carbon Tetraf luoride Teflon, Syn.: tetraf luoro- PTFE ethane

0^4

Irritant

Invar tioo Inhalation 2 2 Skin abaorption

U D 0 U

0 U 0 U

Ethylene Novacalk 600) Syn.) ethane) elayl) CPDN rubber

etherin CHjCHj

Irritant 0 Invention 0 Inhalation 0 3 Skin abaorption 0

0 0 0 0 0 0 0 0

Ethyl Mercaptan

Syn.: elhancthiol:

ethyl hydtoaulfidc

ethyl thioalcohol;

ethyl sulf hydrate

Novacalk 600 Irritant 3 Invention 2 Inhalation 3 Skin abaorption

U U

U U 0 U U U

Nc xa f 1 ooropropy lenc Syn.: pcrfluoro- propene

Cr jCDCFj

Teflon, »-EP PTPE Toxic Hazard Ratinv:

O. Toxicity: Animal experiawnta auvvent ni^erate

toxicity.

Hydrochloric Acid

Syn.; Buiriatic Acid cMorohydric acid: hyJroqon chloride

HClHydrocyanic Acid

Syn. : hydrocen

cyanide: prunsic

aetd

HCN

Tedlar; PVC: Neoprene;

C.con; Halon

Nylon 6,6: Nylon MT-4

Irritant 3 Invention 3 Inhalation 3 Skin absorption

UU

U

Irritant 3 Invention 3 Inhalation 3 Skin absorption 3

U U U U U U 0 U

Rydrcifluoric Acid Tedlar

Syn.: hydroven

fluoride: fluoro- hydxlc acid

HP

Irritant 3 Invention 3 Inhalation 3 Skin absorption

*Durham: 0-none: 1-aliqht: 2-modcrate: 3-hivh: U-unknown, Coasclin • 1-practieally non- toxir; 2-slivhtly toxic: 3-n»lcrately toxic: 4-very toxic: S-extremely toxic: 6-supertoxic (See Section 13).

B-12
CHKMICAU SUBSTANCE

(GENERIC)

Hydro9en

H

2

Toxicm rating'-gossrlim*’** PRODUCT TojcTclTY hATl)4'6

EDPM rubber

TOXIC HAZARD RATING*.

DURHAW^^**

Irritent Ingettion Inhalation

Skin abaorptlon

Acute Chronic

Hydrogen Sulfide Novacalk 600

Syn. : sulfucetted hydrogen

Irritant I Ingestion

Inhalation 3 Skin Absorption

U

u

uu3

Isobutanc

Syn.: 2-sicthyl propane; trl- ncthyl methane

Novacalk 420 Irritant 0 Ingestion 0 Inhalation 0 1 Skin absorption 0

0 0

0 U

0 U

0 U

Methane

Syn.; marsh gasi

eiethyl hydride

Dow Corning 7S1; Novacalk 420; EPDM rubber; Nylon HT-4

Irritant 0 Ingestion 0 Inhalation 0 1 Skin absorption 0

0

0

0

0

1

Methyl Methacrylate Plexiglass;

(BonoBor) Lucite CHjC(CHj)COOCHj

Irritant 1 Ingestion 3 Inhalation 1 Skin ab.sorption

U

U 1 U 1 U

Propylene

Syn. ; propene EPOM rubber

Silica

Syn.: silicon

dioxide: silicic

anhydride; cristobalite

Toluene

Syn.; methy Ibcnrene;

phe iiy 1 rac t hanc

toluol

Dov Corning 781

Geon; Ha Ion; PVC; Neoprene

Vinyl Chloride PVC; Ceon;

Syn.: chloroolhylenc; Halon chloroethenc

CH^CIICl

Irritant 0 Inoestion 0 Inhalation 0 2 Skin absorption 0

0 0

0 0

0 0 0 0

Irritant 0 Ingestion 0 Inhalation 3 0 Skin Absorption 0 3 1

Irritant 1 Ingestion 3 Inhalation 3 Skin absorption 1

3

3

2

Irritant

Ingestion Inhalation

Skin absorption

3

3

*Durha*: 0-nonc; 1-sliqht; 2-SK>dcrate 2>slightly toxic: 1-modcrately toxic;

3-highj U-unknown. Cosselin ~ 1-piact ically non-toxic;

4-very toxic; S-extrenely toxic; 6-super-toxic.

B-13
Table B-5

CHEMICAL SUBSTANCE

(GENERIC)

Armnonium Bromide

NH^Br

Barium Compounds

(soluble)

Barium Hydroxide

Syn.: Barium Hydrate

caustic baryta

Ba (OH)2-8H20

Benzamide

Benzoic Acid

Syn.; phenyl formic

acid

C.H^COOH

b o

Biphenyl

Syn.; Diphenyl

Bromides

Calcium Bromide

CaBr,.6H20

Calcium Chloride

CaCl2

Calcium Compounds

Toxicity of Thermal Storage Media

TOXICITY RATING*-GOSSELIN*^^^ PRODUCT TOXICITY RATING'

TOXIC HAZARD BATING^

DURHAM

Acute Chronic

see bromides

Irritant

Ingestion

Inhalation

11 3 1 3

1 2

2

sec barium

compounds

Oral-mouse

LDjq 1160 mgAg 3

Oral-rat

LDsq 3040

Oral-mouse

LDjq 2370

mgAg**^* 3

mgAg<«>

Irritant 1 Ingestion 1 1 Inhalation 1 Skin Absorption

Oral-rat

3280 mgAg'"^'

Oral -rabbit . LDjp 2400 mgAg'^^'

Irritant U

Ingestion U

Inhalation U

Skin Absorption U

2

2

0

U

U

U

2

2

Irritant

Ingestion

Inhalation

1

2 2 2

1 2

2

see 'bromides

Oral-rat

LD^q 1000

Oral-rabbit

LDLq 1384

mgAo^®^^ 3 see calciumcompounds

Irritant

Ingestion ' Inhalation ,, 1 Skin Absorption

U

U

U

U

1 U

U

U

U.

B-14

Local

systemic
CHtrMlCAL SUBSTAKCE-

(GENERIC) PRODUCT

TOXICITY RATING*-GOSSELIN^^®' . TOXICITY RATING'

Caprylic Acid

Syn.: octanoic acid

CH^jCH^) gCOOH

TOXIC HAZARD RATING®-

DURRAM

Acute Chronic

Experimental

data suggest

low toxicity

u

•ac a

o

o

o

(D A

U — O

13 -» O A 0 >»A

Diphenyl oxide

(CBjljO

Oral-rat

LDjq 3370 tng/)cg (81) 3

Glaubers Salt See sol. sulfate salts

of sodium

Laurie Acid ' Syn.: dodecanoic acid

CHj(CH2) j^qCOOH

Myristic Acid Nontoxic by oral

Syn. I tetradecanoic administration

acid

Animal data suggest low toxicity

for lauric acid

esters. Details

unknown.

Naphthalene

Syn.: moth flakes;

white tar; tar

campher.

Oral-rat /«n\ LDjq 1780 itigAg 3 Oral-human child

LDLo 100 mg/kg'

Irritant 2 Ingestion

Inhalation

Skin absorption

2

22

1 2

1

' 2

Nitrates

Paraffin Wax^

Irritant U Ingestion U

Inhalation U Skin absorption U

2

2

Irritant 0 Ingestion 0 Inhalation 0 Skin absorption 0

0

00

0

U

u

uu

22

Polyethylene Glycol 400

iicx:ii,(cn,ocM,) ch,oh

/ A X n /

(i» varies from 8-10)

2 Toxic Hazard

^Rating: U

Polyethylene Glycol 600 2

Polyethvlenc Glycol

6000

Oral-rat

LDLo 50 gmsAg' 1 Toxicity; U

B-15
CHF.MICAL SUBSTANCE

(GENERIC) PRODUCT

TOXICITY RATING*-G05SELIN^*^’*

fojfICIT)? RATlNfi

TOXIC HAZARD RATING^

DURHAM

Acute Chronic

u

u

o

'A>1

lA

Sodium Sulfate

(sol. sulfate salts of

sodium)

Amount of sulfate anion

usually absorbed has no toxicological

significance

Stearic Acid

Syn.; octadecanoic

acid

CH^(CH2) j^^COOH

Toxicity:

Slight

Zinc Nitrate

zn (NOj)

Oral-rat

1190 mgAs' ' 3 nitrates

^Durham; 0-none; 1-sllght; 2-moderate; 3-high; U-unknown. Gosaelin = 1-practically

non-toxic; 2-slightly toxic; 3-moderat»»ly toxic; 4-verty toxic; 5-extremely toxic;

6-super- toxic (See Section 13)

^Recognlxed carcinogens of skin (81)

B-16
Table B-6

Toxicity of Outgassing Products from Solids

TOXIC HAZARD RATING®-

DURHAM^^®^

chemical substance

(GENERIC)

FROM TOXICITY RATING*- GOSSELIK^^*^ Acute Chronic

PRODUCT ToxTcTty RAfTTSc

Local

1

Systemic

1'

c

(jo

•J

Systemic

|

Argon Kovacalk 420, Irritant 0 u u A butyl rubber; Ingestion 0 U u Novacalk 600, Inhalation 0 1 U u polysulfide Skin absorption 0 u u

Carbon Dioxide Novacalk 420, Irritant 0 0 CO butyl rubber; Ingestion 0 0

A Novacalk 600, Inhalation 0 1 0 1 polysulfide; Skin absorption 0 0 polyisocyanurate

foam with a urethane modidier; tan polyurethane

foam; suprathane; pink

fiborglass

insulation with

phenolic binder

Carbon Monoxide Novacalk 420, Irritant 0 0 CO butyl rubber; Ingestion 0 0 Novacalk 600, Inhalation 0 3 0 1 polysulfide Skin absorption 0 0

FI uorot rich lor ome thane Freon 11; poly- Irritant 1 1 Syn.i trichlorof luoro -* phenyl isocyanur- Ingestion 1 1 methane ate foam with a Inlialation 2 2 reel. urethane modifier; Skin absorption 1 1 tan, Dol vurethane

foam; Suprathane

Hydrogen Novacalk €00, Irritant 0 0 0 polysulfide Ingestion 0 0 0

A Inhalation 0 1 0 0 Skin absorption 0 . 0 0

Hydrochloric Acid polyphenyl- Irritant 3 2 u Syn.: muriatic isocyanurate Ingestion 3 u acid, chlorohydric foeim with a Inhalation 3 u acid hydrogen urethane mod- Skin absorption u chloride ifier; tan HCl polyurethane

foam; Suprathane

B-17
CHEMICAL SU3STAKCE

(GENERIC

PROM TOXICITY RATIKG*-.COSSELXM*’*^

PRODUCT roxiclTi^ ' SaTTRg

Methane

Syn.i marsh east methyl hydride

Novaealk 420,

butyl rubber;

Novaealk 600,

polysulfide

Methyl Styrene common white

styrofoam

TOXIC HAZARD RATING*-

DURHAM

Acute

V

Chronic

Irritant 0 Ingestion 0 Inhalation 0 1 Skin absorption 00

0

00

1

Irritant

Ingestion

Inhalation

Skin absorption

U

0

U

U

0

UU

U

Nitrogen

M

2

Novaealk 420,

butyl rubber;

Novaealk 600,

polysulfide

Toxicity; None

Phenylethylene

Syn.i vinylbenxene,

styrene (monomer)

cinnamene

CgHjCHCHj

common white

styrofoam

Irritant

Ingestion

Inhalation

Skin absorption

^Durham; 0-none; 1-sllght; 2-moderate; 3-hlgh; U-unknown. Gosselin «• 1-practically non-toxic;

2-slightly toxic; 3-moderately toxic; 4-very toxic; S-extreswly toxic; 6-super-toxic

B-18

Systemic
Table B-7

Toxicity of Combustion Products

CHEMICAL Sl’BSTANCE (GENERIC) TOXICITY RXTING*-COSSELIN^’** PRODUCT foxIcTIW TWTWr

TOXIC HAZARD RATING - DURHAM^’®’ Acute Chronic

Acetone Nylon RT-4

Syn^: dimethyl ketone; ketone propane; propanone CHjCOCHj

'Acetylene Butyl rubber.

Syn.: ethyne; ethine Kovacalk 420; RCCB

Afliaonia Syn.: ancnonia gas

HH,

lfRf?''*bcn*ol; phenyl

hydride; coal *

naphtha

Butadienc-1 ,

(uninhibited) - Syn. : erythrene

CHjCHCHCHj

Carbon Dioxide

Syn. I carbonic acid; caibonir anhydride

“2

Carbon Monoxide CO

Carbonyl rluorido

Syn.: fluoro(or»yl

fluoride

COfj

Nylon 6,6

Nylon 6,6

Neoprene: PVC; Goon; Kalon

Neoprene

Neoprene; Dow Corning 781; Novacalk 600; PolyEulfide, C9; butyl rubber,

Novacalk 420: Teflon, PTFE: Teflon, PEP; Teflon, PFA; Tcdlar; Lucite;

Plexiglass; PVC; Geon; Ha Ion; Nylon HT-4; Nylon

6,6

Neoprene; Dow Corning 781; polysulfidc,

Novacalk 600; polysulfide, C9; butyl rubber,

Novacalk 420; Teflon, PTFE; Teflon, FEP; Teflon. PFA; Lucite:

Plexiglass;

PVC : Geon

Ha Ion: Nylon HT4; Nylon 6,6

Teflon. PTFE

Irritant

Ingestion

Inhalation

Skin absorption

Inhalation

Irritant

Ingestion

Inhalation

Irritant

Ingestion

Inhalation

Skin absorption

Irritant

Ingestion

Inhalation

Inhalation

Inhalation

Irritant

Inhalation

Durham: 0-none: I'sHght; 2-modoratc; 3-higti; U'unknown. Gosselin: 1-practically nontoxic;

2-sligiitly toxic; 3-moJerately toxic: 4-very toxic: S-extremcly toxic; 6-supertoxic.

^Kecognirod carcinogen of the blood-forming tissues (81).

B-19
TOXIC HX7ARD RATING

DUPHA><’** CHIXICAL SUBSTANCE

(GENERIC) PRODUCT TOXICITY RATING*- GOSSr.UN*^*>

fbxrtlfi IRTIIK Acute Chronic

Ethane

Syn.: bimethyl;

methyl nethane;

dimethyl; ethyl

hydride

C2«6

Ethyl Alcohol

Syn.t ethanol; methyl carbinol;

spirit of wine

CHjCHjOH

Ethylene

Syn.: ethene;

elayli etherin

CHjCHj

Fluorides

Porstaldehyde^

Syn.: Mthanal;

methyl aldehyde;

formalin

HCHO

Formic Acid

Syn.: methanoic acid;

hydrogen carboxylic

acid

HCOOH

Hydrochloric Acid

Syn. I muriatic acid;

chlorohydric acid;

hydrogen chloride

HCl

Hydrocyanic Acid

Syn.: hydrogen

cyanide; prussic

acid

HCN

Hydrofluoric Acid

Syn.: hydrogen

fluoride; fluoro- hydric acid

HP

Hydrogen

a

Neoprene

PVC; Ccon; Ralon

Polysulfide,

Novacal): 600; Polysulfide,

C9

Neoprene;

Nylon 6,6

Dow Coming 7tl

Dow Corning 7B1

Neoprene; PVC; Geon; Ralon

Nylon HT-4; Nylon 6,6

Tedlar

Neoprene;

butyl rubber,

Novacalk 420; Lucite;

Plexiglass

Inhalation

Irritant

Ingestion

Inhalation

Skin absorption

Inhalation 2 0

Irritant

Ingestion

Inhalation

Irritant

Allergen

Ingestion

Inhalation

Irritant

Ingestion

Inhalation

Irritant

Ingestion

Inhalation

Irritant

Ingestion

Inhalation

Skin absorption

Irritant

Ingestion

Inhalation

Inhalation

'Durham: 0-none; 1-slight; 2-moderate; 3-high; 0-unknown. Cosselin; 1-practically nontoxie;

2-slightly toxic; 3-moderately toxic; 4-very toxic; S-extremely toxic; 6-supertexie.

*A suspected carcinogen of the lung.

B-20

Local

Systemic
TOXIC HAZARD RATIMG*-

DORHAM*’®’ CHrMICAL r.URSTAMCE TOXICITY RAT1NG*-G0SSEMM*’*'

(CF.NRRIC) PRODUCT foXICl'fT RATING

0 O

F. c V «> m 4i•

•S (A •J U)

Methane Neoprene; PVC; Inhalation 0 1 0 1 Syn. 1 marsh gas; Ceon: Ha Ion: methyl hydride

CH,

Nylon 6,6

Methyl Chloride PVC ; Ceon

Irritant 1 U Syn.: chloromethane

CHjCl

Ha Ion Inhalation 1 3 u 2

Methyl Methacrylate Lucltc; Irritant 1 u

(nonoiocr) Plexiglass Ingestion 2 u 1 CHjClCHjlCOOCHj Inhalation 1 u 1

Nitromethane Nylon HT-4 Irritant 2 0 V CHjMOj Ingestion 3 u V Inhalation * 3 0 V

Silicon Tetrafluoride Teflon, PTFE; See fluorides

Syn.z tetrafluoro- Teflon, FEP; silane Teflon, PPA

SIP^

Toluene PVC; Ceon; Irritant 1 1 Syn.: molhylbcnzciie; Ha Ion; Neoprene Ingestion 2 2 phenyln« thane; Inhalation 2 2 toluol Skin absorption 1 2 CjHjClli

Vinyl Chloride^ PVC ; Geon

Irritant 3 2 Syn.: cMoroethylene: Halon Inhalation 2 3 chloroethene

CHjCHCl

Vinyl Fluoride

Syn.: f 1 uoroethylcne

CHjzCHF

Tcxllar See fluorides

Xylene Tedlar Irritant 1 1 Inhalation 2 2 Skin absorption 2 2

Duiiiaoi: 0-none; l-sli^ht; 2-modoratc; 3-high; 0-unV.nown. Coasclin: 1-practical ly nontoxic;

2-sliyhtIy toxic; 3-modcrotcly toxic: 4-very toxic; &-extrenely toxic; C-supertoxic.

dA recognized carcinogen of the liver (81).

B-21
it

I i:

* iv.

‘ i"- no ! . ;, . i.r.1.1

f- .

' -• ' 1*?^ 4/ .'f>>*.£ %-itf. . 'i '

''-<'•4

^ .-S,

i' \ <•* ,’• ;»v.!|

' . fs-X-t

' V.' "o >

.ViW

-

'.J-

'

' a

r

; *M S?vt3f»ut r>*«wrt

I r-'i. 'X- ; IJM.

,.'0i

* , J r> if ,--l

A,.

C A .

--i-j ;

• .X , i

f' / i»4 .' V < c*

ia*nr , "V ' tic “i (If ft.^;1; lb* « ft'

is-'

' s

'

, S

' - - .. 'i •'-

Irtv

m'--:

I i,

•' 1 tolc

'• •-

5'-'S A

^ ^ • )

' /iVi? “ ^

’ '^ ji *1 -' —t-

•j - |r,

’ M

TaifetSf"/

_ -siuuwrt

^.‘ jjjL.y »< f * . , •( I i ’»

. A‘^

*' » *

y

'

'if-

,, -•w» , -' .• ‘

, 1V

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' S'.

•>,''' 'If}'.'- |,,'ij»i ) r.'. • t“.l:!p:«^».-'.ji...-<«-*>» tVSi •' > i • ,-. 'TC3 7

.' .Hv I, t «rt;

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53
m

BOCA

BASIC

MfCHANiCAL

COD^

i?** '’

Anpc

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NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 78-1542

2. Gov’t Accession

No.

4. TITLE AND SUBTITLE

State- of- the -Art Study of Heat Exchangers Used with Solar

Assisted Domestic Hot Water Systems (Potential Contamination

of Potable Water Supply)

3. Recipient’s Accession No.

5. Publication Date October 1978

6. Performing Organization Co(Je

7. AUTHOR(S)

F. Eugene Metz and Mary Jane Orloski

8, Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 7446505

11. Contract /Grant No.

lAA EA- 77 -A- 01- 6010

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Division of Solar Energy

Department of Energy

20 Nfessachusetts Avenue, MW

Washington. D.C. 20545

13. Type of Report & Period

Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

This report presents the results of a non quantitative state-of-the-art study of

heat exchangers used with solar assisted domestic hot water systems vtiere a heat

exchanger interface exists between the potable water supply and a heat transfer

fluid. Emphasis is placed on the potential for contaminating the potable water

supply if failures should occur. The study considers (1) characteristics of

various heat exchanger types and their relative safety; (2) characteristics of

heat exchanger fluids (toxicity, corrosivity, thermal properties, etc.); (3)

regulatory considerations; and (4) designs of similar systems with potential

for contamination.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Contamination; corrosion; heat exchanger; heat transfer fluids; potable water;

solar energy; standards; toxicity.

18. AVAILABILITY [X] Unlimited

[3^ For Official Distribution. Do Not Release to NTIS

C J Order F rom Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402, SD Cat. No. C13

[X Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

81

22. Price

$6.00

USCOMM-DC 29042-P74

1I<