NATIONAL BUREAU OF STANDARDS REPORT

1471*0

Progress Report

Heat Absorbing Capacity of an Underground

Reservoir used as a Heat Sink

by

Bo Ao Peavy

Ro So Dill

Report to

Office of the Chief of Engineers

Department of the Army

<QJBp>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DKPARTMENT OF C()MMP:KCF

Sinclair Vt eeks, Secretary

^A'J'I()^AL Ul'REAL OF STANDARDS

A. \. As(in, Director THE NATIONAL BUREAU OF STANDARDS

The scope of aeti\ities of the National Rureau of Stanrianls at its headquarters in \\ asliington, n. C.. ami its major field laboratories in Boulder. Colorado, is suggested in the following listing of

the di\ isions and sections engaged in technical work. In general, each section carries out specialized

research, development, and engineering in the field indicated h\ its title. A brief description of

the actisities. and of the resultant reports and publications, appears on the inside back cover of

this re|>ort.

W ASHINGTON. I). C.

Electricity and Electronics. Resistance and Reaetance. Electron Tubes. Idectrical Instru- ments. Magnetic Measurements. Process Tecbnology. Engineering Electronics. Electronic

Instrumentation. Electrocbemistr \

Optics and Metrology. Photometr\ and Colorimetr>. Optical Instruments. Photographic

'FechnologN. la'iigth. linginta'ring Metrology.

Heat anrl Power. reinperatiire M(*asurements. IhermodN namics. Cr\ogenic Ph\si<'s.

I'ingines and Eubrication. I Engine Euels. .Atomic ami Ha<liation Physics. Spectroscop^ . Radiom<‘tr\ . Mass S[)(“ctrometr\ . Solid

Slate Plnsies. I'Jectron Plnsics. \tomic Phvsics. Nuclear Pb\sies. Radioacti\ it\ . \-ra\s.

Betalrcui. Nucle<»nic Instrumentation. Radiological l,(plipment. AEC Radiation Instruments. Ghemistry. ( irganic (Joatings. Surface Cheniistr\ . Organi<’ ClunnistrA . Analytical (ihemistry . Inorganic (Jb(‘inisir\ . Ideclrodeposiiion. Gas (^heinisir\. Pin sical Chemistry. riiermoch<“inisir\. Speeirochemislry . Pure Substances.

Mcchanif's. Sound. Mechanical I nsiruimmls. Fluid .Mechanics, laigineering Mechanics.

Mass and .Scale. (iapaci|\. Densiix. and Fluid Mc'lers. Combustion Controls.

Organic and Fibrous Materials. Rubber. Textiles. Paj)cr. Eeatlu'r. Testing and Specifications. Pol\ Tiler Structure. Organic Plastics. Dental Research.

Metallurgy. riitirnal Melallurg\ . (ihcmical Metalhirg\. Mechanical Metallurgx. (Corrosion.

Mineral PrTjduels. (Ceramic I .ngincering. I’orcclain and Polterv. (ilass. Ridractories.

|•.nameled Metals, (ioncreling Mat<>rials. Constitution and Microstructure.

Building recdinology . .Structural Engineering. Fire Protection. Heating and Vir (iondilioning. h loor. Bool, ami Wall (Coverings. (]od<‘s and .Specifications.

A|)plii‘<l Mathematics. Numerical \nal\sis. Computation. Statistical |.ngineering. Mathematical Phxsics.

Data ProcT'ssing Sysl<-ms. (iompommts and d'cchniipu's. Digital Circuitry. Digital Sysl»‘ms.

\nalogue .Systems. Applications l,ngincering. • Office ol Basic Instrumentation • ( ffliee of W eights and Measuri's

BOl EDER. COLORADO

( .ry ()g<‘ii ii‘ I'.ngim'ering. (ir\ogeuic l'.(piipmcnt. (ir\og<'nic Processes. Properties ol Materials,

(/as Eitpielact ion. Radio Propagation Physics. I pper \tmosph('re Research. lonospht'ric Research. Regidar

Propaga t ion .Scr\ icc's. Rml io Propagation I'ingi n<‘<‘ri ng. I'rccpiencx I tili/ation Resi'arch. ’Eropospheric Propagation

Research.

Raditt Slamlards. High l'rc(picnc\ Stainlaials Branch: High I'rcTpicncx Mcctrical Standards.

Radio Broadcast .Serx icc. High liaMpicncx I ni|)cdancc Standards. M icrow axe Standards Branch:

Ixtrcmc High l'r<‘qucncx and Noi.se. Microxxaxc |'rc(plcncx ami Spect roscopx . MuToxxaxe

( .irenit .Standards.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003=10-14831 July 10 , 1958 14740

Progress 'Report

Heat Absorbing Capacity of an Underground

Reservoir used as a Heat Sink

by

Bo A„ Peavy

Ro So Dill

Heating and Air Conditioning Section

Building Technology Division

to

Protective Structures Section

Protective Construction Brancbi

Office of the Chief of Engineers

Department of the Army

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, n

unless permission I 25 , D, C, Such pe

cally prepared If I

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

In part, is prohibited

tandards, Washington

^port has been specihepori for its own use,

HEAT ABSORPTION CAPACITY OF A 1„5 MILLION GALLON

UNDERGROUND RESEliVOIR USED AS A HEAT SINK

by

Bo A„ Feavy and Ro S„ Dill

lo INTRODUCTION

As far back as 1952, there were serious discussions of the vulnerability of the outside cooling

water service of underground installations « The

Bureau of Standards, by request of the Office of

Chief of Engineers, initiated a study of the use of

underground reservoirs for the absorption of heat

dissipated by engines, compressors, etc„ This

study involved both a theoretical and experimental

approach to the subjecto The experiments were made

with a relatively small existing underground reservoir containing about 13,000 gallons and heat was

added to the water at a constant rate during two

periods each of about 30 days duration^ Results

of these tests show that a considerable portion of

the heat added to the water is stored in the surrounding rocko These tests Involved lower heat

input rates than were anticipated for larger

reservoirs

„

As suggested by staff members of the National

Bureau of Standards, the reservoir In a large

installation was considered for absorption of heat

from the Diesel engines and refrigeration condensers, From computations made by both the architect^

engineer and the NBS staff members, it was determined

by analytical approach that the installation could

4^ ^ self -sustaining for a period of seven days or

more with a heat input rate to the water of 6 million

Btu per hour. This estimate was made on the assumption that the initial water temperature would be

52°F and that water would be discharged from the

Diesel engines to the sewer after it attained a temperature of 95 °F the outlet from the reservoir, A resume of the findings is given under

Discussion in this report.
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2. PROCEDURE

A test was conducted under a siFaUlated

emergency condition, to determine the time at which

a lo5 million gallon reservoir becomes too hot to

be suitable for absorbing heat from the refrigeration condenser and Diesel engines. This time was

defined arbitrarily as the instant at which the

temperature of the water leaving the reservoir

attained a temperature of The object of

this test was to determine the feasibility of using

the reservoir as a heat absorber during the

emergency condition when outside water would not

be available for cooling purposes, to corroborate

the design computation and also to show the

potentialities of storing heat in the surrounding

rock mas So

3, INSTRUMENTATION

A water meter was installed in the water line

from the reservoir. Thermocouples were installed

in the pipes to measure temperatures of water

flowing from the reservoir and water returning

to the reservoir. Thermocouples were also located

in the reservoir, at the water surface and at

depths of 6, 10, 15, and 21 feet. The temperatures were recorded on a strip chart by a potentiometer recorder. Heat input rates to the

reservoir were computed from water flow rates and

the differences in temperature between waterentering and leaving the reservoir.

RESULTS

Observed conditions during the test were as

f ollows

;

1 , Initial reservoir water

temperature, deg F 50
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2 , Duration of test, hours 117

3. Average heat input rate to

water, Btu /hr 6,13x10

Temperature history-see

accompanying graphs.

Figures 1 and 2

5. Average reservoir water temperature at 117 hours, deg F 101

6 , Heat added to water, total,

Btu 717^^10^

7 . Heat absorbed by water, Btu 636x10^

8 . Heat absorbed by surrounding

rock, Btu 79 x10

^

9 o Additional time allowed by

storage of heat in the

surrounding rock, hours 13

An analytical study of the heat absorption of

the rock surrounding the large reservoir is given

in NBS Progress Report No, 29I42, subraitted to the

Office of the Chief of Engineers, November 27 , 1953 • The results of the computations from the above

report are shown below in Figure 3 ^ heat

input rate of 6 , 13 x10 ° Btu per hour to the reservoir, The resulting curve closely follows the

observed temperatures which are also plotted on

Figure 3 » 1^® observed temperatures wei-e obtained

by averaging the water temperatures measured at

the various depths. The temperatures obtained

analytically and given in Report 29^2 were adjusted

for the actual heat input rate of 6 . 13 x10 ° Btu per hour

by means of the formula:

T = (T< - 50)

6,13:^10^

6xl0<3 + 50

where T* is an analytically-determined temperature

taken from Report 29 ^42 ,
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During the tests, the water returned to the

reservoir through spray nozzles and bathed the

rock above. the water in the reservoir and then

drained into the reservoir by gravity. In the

reservoir, the warmer water, due to i^ts lower

density, tended to stay on top and de.cended to

lower levels as colder water was taken from the

bottom. Figure 1 illustrates this point. The

outgoing water temperature is seen to remain at

approximately ^0°F for the first 52 hours.

Some mixing of the water may be noticed during

the period from I4 O to 52 hours by a slight

increase above 50°F» Beyond 53 hours a sharp

temperature increase of the water from 5 I 'to 70°F in 16 hours occuired after which the

increase was at a slower rate. This temperature increase at the bottom follows the initial

temperature increase of the surface at a slower

rate and with a time lag of 52 hours.

If there were perfect mixing of water in the

reservoir, the leaving water temperature would

closely follow the average water temperatures

of Figure 3 and 95 outgoing temperature would

have been reached at 101 hours. The effects of

stratification Increased the length of this test

by approximately 16 hours. This appears to be

considerable savings in time, but it must be

realized that after 117 hours, the water in the

reservoir which is to be dumped to the sewer afterbeing used for cooling the r efrl ger a Lion condenser

and Diesel engines was above 95°F average

of 101 °F.

.

If the installation must be self °sus talning

for a period of one week (I 66 hours), 168-117=^51

hours are left in which to drain the reservoir

at a water flow rate from the reservoir o^* I49 O gpm.

At the average heat input rate of 6,13x10° Btu

per hour the temperature rise of the water through

the refrigeration condenser and Diesel engine would

be 25 °F, which indicates that temperatures as

high as 130°F leaving the Diesels might occur,

6 During the 117 hour period, 717^10 Btu were

added to the water of which 636x10° Btu were in

the reservoir water and 79x10° Btu were dlsbipared
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by conduction of heat into the surrounding rock and^

to a minor e:xtent, overflow from the reservoir due

to e-xparision of the water. Although the heat thus

accounted for comprises only 11 percent of the

total heat added to the water, it served to

lengthen the reservoir life by about I 3 hours.

To perform by use of the present reservoir,

one or both of the following functions: (1)

extend the length ol' the emergency period beyond

one week, and/or (2) exceed the heat input rate

of 6x10° Btu per hour, strong consideration

should be given to maintaining the reservoir at

some temperature below . For the sake of

example, one degree P temperature rise in 1,5

million gallons accounts for 12o5^10° Btu per

hour or approximately 2 hours of running time

at a heat input rate of 6.13x10° Btu per hoiur

.

The present test was probably run at the optimum

time of the year when the well water temperature

was near its minimum. Late summer well water

temperatures are probably higher. Maintaining

the reservoir at [|0°F would have Increased the

reservoir life by 20 Lours if the only consideration were the heat in the water. It is also

feasible to riialntaln an ice to water balance in

the reservoir whereby the latent heat of fusion

mu Btu/lb) will add a heat sink. An example of

this, assume that one-fourth of the water is ice

at 32°F. Then the increase in reservoir life would

be 110 hours, which does not Include the additional

heat capacity of the surrounding rock due to its

lower temperature.

Proportionately, theNbenefits possible from

utilizing the heat storage^ capacity of rock

surrounding a reservoir (Is) greater at lower heat

input rates since lower input rates permit a longer time interval for the rock to absorb heat

in any given temperature increment.
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HEAT

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W/VTER TEMPERATURES AND HEAT INPUT RATES iTQ VV^ATER

FOR TEST ON 1.5 MILLION GALLON RESERVOIR

TEST STARTE!) 1200 - 6 MAR 56

TEST ENDED 0900 - II MAR 56

SURFAC!

DEPTH

FLOW RA'TES; Qf^

TIME, HOURS
temperature

LL

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WATER

TEMPERATURE

AT

DEPTH

IN

RESERVOIR

ocrcPRvniR

DEPTHFT

WATER TEMPERATURE,

FIG.

2

WATER

TEMPERATURE

AT

DEPTH

IN

RESERVOIR

TIMF-"

HOURS

V/ A T t. K T E M E E h' A T K f , F

CJl CD -n1 CD (X) o

O O O O O o

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

development of standard practices, codes, and specifications. The work includes bas’C and applied

research, development,' engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of the Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic Energy

Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project

or program. Published papers appear either in the Bureau’s own series of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

summary and preliminary reports on work in progress; and Basic Radio Propagation Predictions,

which provides data for determining the best frequencies to use for radio communications throughout

the world. There are also five series of nonperiodical publications: The Applied Mathematics

Series, Circulars, Handbooks, Building Materials and Structures Reports, and Miscellaneous

Publications.

Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

the National Bureau of Standards ($1.25) and its Supplement ($0.75), available from the Superintendent of Documents, Government Printing Office. Inquiries regarding the Bureau’s reports and

publications should be addressed to the Office of Scientific Publications, National Bureau of

Standards, Washington 25, D. C.