1987

STANDARD for

.IJP;

...I'..

AIR-CONDITIONING

& REFRIGERATION

INSTITUTE

DESUPERHEATERI

WATER HEATERS

I Standard 470 I

EXHIBIT 1

1501 WILSON BOULEVARD ARLINGTON, VIRGINIA 22~09

EE-RM-90-201 COMMENT OOR18

1987 

STANDARD for 

,liP. 

.... ,. AIR,CONDITIONING 

& REFRIGERATION 

INSTITUTE 

DESUPERHEATERI 

WATER HEATERS 

I Standard 470 I 

EXHIBIT 1 

1501 WI LSO N BOULEV A RD • A R LINGTON, VIR G IN IA 22", 09 
TABLE OF CONTENTS

PART PAGE

Section I. Purpose I

Section 2. Scope 1

'Section 3. Definitions 1

Section 4. Standard Equipment and Accessories I

Section 5. Testing and Rating Requirements I

Section 6. Safety Recommendations and Sanitary Provisions 4

Section 7. Marking 4

Section 8. Voluntary Conformance 4

APPENDIX A. METHOD OF TESTING DESUPERHEATER/WATER HEATERS

Section A 1. Purpose 5

Section A2. Scope '5

Section A3. Definitions 5

Section A4. Expression of Test Results 5

Section AS. Test Methods 5

Section A6. Instruments, Test Apparatus, and Thermodynamic Properties 6

Section A7. Test Procedure 6

Section A8. Computation of Results 7

TABLES

Table I. Standard Rating Conditions 4

NOTE

This standard supersedes ARI Standard 470-80.

PrICe $8.00

Printed in U.S.A. © COPYRIGHT; 1987 by Air-Conditioning and Refrigeration Institute

EE-RM-90-201 COMMENT OOR18

PART 

Section I. Purpose 

Sectio n 2. Scope 

'Section 3. Defini tions 

TABLE OF CONTENTS 

PAGE 

.. I 

. . . . . . . . I 

...•. 1 

Sectio n 4. Stand ard Eq uipment a nd Accesso ries 

Section 5. Testin g and Rating Req uireme nts 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 

Section 6. Safety Recommendations and Sanitary Provisions .. . .. . 

Section 7. Mark ing . . 

Section 8. Vol untary Conformance .. 

APPENDIX A. METHOD OF TESTING DESUPERHEATER/WATER HEATERS 

Section A I. 

Section A2. 

Purpose . .. . 

Scope . ... .......... ... .. . 

Sec ti on A3. Defi niti ons ....... . 

Section A4. 

Section A5 . 

Expression of Te st Results ... .. ..... ................ ... .... .. . ..... . 

Test Me thods .. 

Section A6. Instruments. Test Apparatus. and The rmodynamic Pro perties 

Section A 7. Test Proced ure 

Section A8. Comput ation of Results 

TABLES 

Table J. Standard Rali ng Conditions 

NOTE 

This standard supersedes ARI Standard 470.s0. 

.... I 

. . . 4 

. . .. . 4 

. . .. 4 

. .... 5 

..5 

. .... 5 

..5 

; 

. .. 6 

. .. 6 

.. . 7 

. 4 

I'"ell SB.OO 

P"moo III U.S.A CI COPYRIGHT, 1987 by Air-CondItioning and Relrigeratiollinsfitu/e 
_______________________ ARI STANDARD 470·87

DESUPERHEATER/WATER HEATERS

Section 1. Purpose

1.1 Purpose. The purpose of this standard is to establish, for desuperheater/water heaters: definitions; a

specification of what constitutes standard equipment;

procedures for testing and rating; safety provisions; and

requirements for marking.

1.1.1 This standard is suggested as a guide for the

industry, including manufacturers, distributors,

contractors, consulting engineers, and users of

desuperheater/water heaters.

1.2 Review and Amendment. Thisstandard is subject to

review and amendment as the art of the industry advances.

Section 2. Scope

2.1 Scope. This standard applies to desuperheater/

water heaters supplied as separate components, as defined in 3.1.

2.2 Exclusion. This standard does not apply to

desuperheater/water heaters supplied as components of

factory-assembled refrigeration or airconditioning units.

Section 3. Definitions

3.1 Desuperheater/Water Heater. A factory-made assembly of elements by which the flows of refrigerant

vapor and water are maintained in such heat transfer

relationship that the refrigerant vapor is desuperheated

and the water is heated.

3.2 Useful Heat Exchange Effect. The useful heat exchanged between the refrigerant vapor and the water

being heated. This value is the product of the mass rate

of water flow, the specific heat of water and the water

temperature rise, expressed in Btuh (W].

3.3 Total Heat Exchange Effect. The total heat removed from the refrigerant in the heat exchanger. This is

the sum of the useful heat exchange effect and the heat

loss through the external surfaces of the heat exchanger

to the ambient air.

3.4 Nominal Refrigerating System Capacity. The cooling effect produced by the product of the mass flow of

refrigerant and the difference in enthalpy between the

refrigerant entering the evaporator and the refrigerant

leaving the evaporator.

3.5 Cleaned Tube Capacity (Btu/h). Cleaned tube capacity in Btu per hour [W] is the total heat exchange

effect (3.3) in the operation of the heat exchanger with

cleaned tubes at the rating condition chosen per Table

1.

3.6 Field Fouling Allowance. Provisions for anticipated

fouling factor during use.

3.6.1 Fouling Factor. The thermal resistance due

to fouling on the heat transfer surface.

3.7 "Shall", "Should", "Recommended", or "It Is

Recommended". "Shall", "should", "recommended",

or "it is recommended" shall be interpreted as follows:

3.7.1 Shall. Where "shall" or '\shall not" is used

for a provision specified, that provision is mandatory if compliance with the standard is claimed.

3.7.2 Should, Recommended or It Is Recommended. "Should", "recommended" or "it is recommended" is used to indicate provisions which

are not mandatory but which are desirable as good

practice.

Section 4. Standard Equipment

and Accessories

4.1 Standard Equipment. The following items shall be

required as standard equipment:

1. Refrigerant inlet connection

2. Refrigerant outlet connection

3. Water inlet connection

4. Water outlet connection

5. Data plate or other suitable marking

Section 5. Testing and Rating Requirements

5.1 Published Ratings. Published ratings consist of

Standard Ratings and application ratings. Such ratings

shall be based on tests of desuperheater/hot water heaters with the refrigerant specified in the ratings. The tests

shall be conducted in accordance with the procedure

contained in Appendix A.

5.1.1 Published ratings shall state all the pertinent operating conditions and shall include the

following:

a. Refrigerant designation

b. Entering refrigerant temperature, F (0C]

c. Entering refrigerant pressure psi (kPa]

d. Useful heat exchanger effect, Btu/h [W]

e. Water flow rate, gpm [Lis]

f. Water pressure drop, psi or feet of water

(kPa]

g. Refrigerant side pressure drop, psi (kPa]

h. Refrigerant mass flow rate, Ib/hr [kg/s]

i. Fouling factor (water side) fe·hr·F/Btu

[m2 .oCIW]

plus at least one of the following:

j. Temperature entering water, F rOC]

k. Temperature of leaving water, F rOC]

EE-RM-90-201 COMMENT OOR18

________________________ ARI STANDARD 470·87 

DESUPERHEATER/WATER HEATERS 

Section 1. Purpose 

1.1 Purpose . The purpose of this sta ndard is to establish, for desu pe rhea ter/water hea lers: definitions; a 

specifica tion of what constitutes sta ndard eq uipment; 

procedures for testing and rati ng; safe ty provisions; and 

requireme nts for marking. 

1.1.1 This standard is suggested as a guide fo r the 

ind ustry, incl ud ing ma nufacturers, distri butors, 

contractors, consulting engineers, and use rs of 

desupe rheater/water hea lers. 

1.2 Review and Amendmefll. This sta ndard is subject to 

review and amendment as the art of the ind ustry advances. 

Section 2. Scope 

2.1 Scope. This standard applies to desuperheate rl 

wate r hea lers supplied as separate components, as defined in 3.1. 

2.2 Exclu.sion. T his standard d oes not apply to 

desuperheate r/watcr hea ters supplied as compone nts of 

factory-assembled refrigeration or airconditioning un its. 

Section 3. Definitions 

3.1 DesuperheaterlWarer Heater. A factory-made assembly of elements by which the flows of refrigerant 

vapor and water are maintai ned in such heat transfer 

relationship that the refrigerant vapor is desupe rheated 

and the water is heated. 

3.2 Useful Heat Exchange Effect. The useful heat exchanged between the refrigerant vapor and the water 

being heated. This value is the product of the mass rate 

of wa ter flow, the specific hea t of wa ter and the water 

temperature rise, expressed in Btuh [W]. 

3.3 Total Heal Exchange Effect. The total heat removed from the refrigera nt in the heat exchanger. Th is is 

the sum of the useful heat exchange effcct and the heat 

loss through the external surfaces of thc heat exchanger 

10 the ambient air. 

3.4 Nominal Refrigerating System Capacity. The cooling effect produced by the product of the mass flow of 

refrigerant and the difference in enthalpy between the 

refrige rant entering the evaporator and the refrigerant 

leaving the evaporator. 

3.5 Cleaned Tube Capacity (Btulh). Cleaned tube capacity in Btu per hour [WI is the total heat exchange 

effect (3.3) in the operation of the heat exchanger with 

cleaned tubes at the rati ng condition chosen per Table 

I. 

3.6 Field Fouling Allowance. Provisions for anticipated 

fouling factor d uring use. 

3.6.1 Fouling Factor. The thermal resistance due 

to fouling o n the heat transfer surface. 

3.7 " Shall", "Should", " Recommended", or " It Is 

Recommended". "Shall", "should", " recommended", 

or " it is recommended" shall be interpreted as follows: 

3.7.1 Shall. Where "shall" or 'Ishall not" is used 

for a provision specified . that provision is mandatory if compli ance with the standard is claimed. 

3.7.2 Should, Recommended or It Is Recommended. "Should", " recommended" or "it is recommended" is used to indicate provisions which 

are not manda tory but which are desirable as good 

practice. 

Section 4. Standard Equipment 

and Accessories 

4.1 Standard Equipment. The following items shall be 

req uired as standard equipment: 

1. Refrigerant inlet connection 

2. Refrige rant ou tlet con nection 

3. Wa ter inlet connection 

4. Water outlet connection 

5. Da ta plate or other suitable marking 

Section 5. Testing and Rating Requirements 

5.1 Published Ratings. Published ratings consist of 

Standard Ratings and application ratings. Such rati ngs 

shall be based on tests of desuperheater/hot water heaters wi th the refrigerant specified in the ratings. The tests 

shall be conducted in accordance with the procedure 

contained in Appendix A. 

5.1.1 Published ratings shall sta te all the pertinent o perating conditions and shall include the 

following: 

a. Refrigerant designation 

b. Ente ring refrigerant temperature, F [0C] 

c. En tering refrige ran t pressure psi [kPaJ 

d. Useful heat exchanger effect, Btufh [Wl 

e. Water How rate , gpm {Us) 

f. Water pressure drop, psi or fee t of water 

(kPa] 

g. Refrige ran t side pressu re drop, psi [kPaJ 

h. Refrigerant mass flow rate, lb/hr [kg/s] 

i. Fouli ng factor (water side) fe·hr·FlBtu 

(m' ,"OWI 

plus at least one of the following: 

J. Tempera ture ente ri ng water, F {OCJ 

k. Temperature of leaving water, F [0C] 
ARI STANDARD 470-87 _

5.1.2 Published ratings may also include a nominal refrigerating system capacity. The nominal system capacity in tons shall be based upon a total

heat transfer effect in the desuperheater/water

heater of 2000 Btu/h [588 W] per ton of total system capacity at the 75 F [23.9 0c] entering water

temperature, air-cooled conditions shown in Table

1.

5.1.3 Published ratings shall be accompanied by

the following information:

a. Design pressures for water-side and

refrigerant-side, psig [kPa]

b. All connection sizes and types

c. Shipping weight

d. Operating weight (including refrigerant and

water)

e. Overall dimensions

f. Construction type and details

g. Minimum water flow rate at minimum entering water temperature

h. If only clean tube ratings are published a

statement shall be included to contact the

manufacturer if fouled tube ratings are required.

5.2 Standard Ratings. Published ratings shall include

the Standard Rating, given for at least one of the Standard Rating Groups shown in Table 1 and properly identified as the Standard Rating. Standard Ratings shall be

based on tests with initially clean tubes. Water-side and

refrigerant-side fouling shall be assumed to be 0.000.

5.3 Application Ratings. Application ratings give performance data under operating conditions other than

those shown in Table 1. Whenever application ratings

are published or printed, they shall include, or be accompanied by the Standard Rating clearly designated as

such, including a statement of the conditions at which

the ratings apply. Application ratings shall contain all

information shown in 5.1.1. When application ratings

include water-side field fouling allowance(s) they shall

be calculated by the method specified in 5.4. Published

ratings shall be subject to the tolerances ofthis standard.

5.3.1 Either application ratings or a method of

adjusting the cleaned tube ratings may be presented to show the effect of various water-side field

fouling allowances. These calculation methods or

method of adjusting these ratings shall be calculated in accordance with 5.4.

5.3.2 The manufacturer should provide published information as to the maximum recommended flow rate to minimize erosion and prevent

refrigerant from condensing in the desuperheater.

5.4 *Determination ofRatings. Ratings shall be determined in accordance with the following:

'Note: Where steady state operation is in a condensing mode, this

analysis will be in error.

2

5.4.1 Cleaned Tube Ratings. Published ratings

shall be determined with initially cleaned tubes at

conditions specified for the selected rating group

in Table 1 and conducted in accordance with 5.1.

The results of these tests shall be accepted as including a fouling factor of 0.000 sq ft . hr . F/Btu

[0.000 m2 • °C/W]

5.4.2 Fouled Ratings. From the results of the

cleaned tube tests, calculate the cleaned tube overall heat transfer coefficient, Uc ' Then, mathematically add the specified fouling resistance to the

reciprocal of the cleaned tube Uc and <:alculate the

fouled ratings for publication, using the following

methods, as applicable.

(a) Tube-in-tube (counter flow arrangement

shown -parallel flow also covered).

~( ~e

+ • n n

tw,,~ j:,.... t,cf

(b) Single tube pass shell-in-tube (counter flow

arrangement shown-parallel flow also covered).

"'-I~_----.-..-I-"· o

,

~f

(c) Coil-in-shell, single pass (counter flow

arrangement shown - parallel flow also

covered).

t,f]{

t

I

I

I

\,..----,

1' .... _-_...

: ---.... i<: -~

J,,,,., __') i' '" I __ ........

'.... ,.. ,I

, '--'" \ ..........--, 1" /

I

\.

~f~,-,----,'~_---J

t

t.ve

EE-RM-90-201 COMMENT OOR18

ARI STANDARD 470-87 _______________________ _ 

S.l .Z Published ratings may also include a nomina l refrige rating system capacity. The nominal system capacity in tons shall be based upon a lolal 

hea l transfe r effect in the desuperheater/watcr 

heater of 2000 Btulh (588 Wl per ton of total system ca pacity at the 75 F [23.9 °C) en te ring water 

temperatu re, air-cooled conditions shown in Table 

I. 

5.1.3 Published ralings shall be accompanied by 

the following info rmatio n: 

a. De sign pressures for water-side and 

refrige rant-side. psig rkPa) 

b. All connectio n sizes and lypeS 

c. Shipping we ight 

d . Operating weight (including refrigerant and 

water) 

e . Ove rall dimensions 

f. Construction type and detai ls 

g. Minimum wa ler flow rale al minimum entering water tempe ralUre 

h. If only clea n tube ratings are published a 

statem!:·nt shall be included to contact the 

manufacture r if fouled lube ratings are required. 

5_2 Standard Ratings. Published ratings shall include 

the Standard Rating, given for at least one of the Sta ndard Rating G roups shown in Table 1 and properly identified as th e Standard Rating. Standard Ralings shall be 

based on tests with initially clean tubes. Water-side and 

refrigerant-side fouling shall be assumed to be 0.000. 

5.3 Application Ratings. Application ratings give performance data under operating conditions other than 

those shown in Table I. Whenever application ratings 

are published or printed, they shall include, or be accompanied by the Standard Rating clearly designated as 

such , including a statement of the conditions at which 

the ratings apply. Application ratings shall contain all 

information shown in 5. 1.1. When application ratings 

include water-side field fouli ng allowance(s) they shall 

be calculated by the method specified in 5.4. Published 

ratings shall be subject to the tolerances of this standard. 

5.3.1 Either application ratings or a method of 

adjusting the cleaned tube ratings may be presented to show the effect of various water-side field 

fouling allowances. These calculation methods o r 

method of adjusting these ratings shall be calculated in accordance with 5.4. 

5.3.2 The ma nufactu rer should provide published info rmation as to the maximum recommended flow rate to minimize erosion and prevent 

refrigerant from condensing in the desuperheater. 

5.4 ., Determination of Ratings. Ratings shall be determined in accordance with the following: 

' Note: Whe re steady scate operation is in a condensing mode, this 

analysis will be in error. 

2 

5.4.1 Cleaned Tube Ratings. Published ratings 

shall be determined with initially cleaned tubes at 

nditi s specified for the selected rating group 

In Table 1 and conducted in accordance with 5.1. 

The results of these tests shall be accepted as including a fouling factor of O.OCIO sq ft . hr . FlBtu 

[0.000 m' . °CIWj 

5.4.2 Fouled Ratings. From the results of the 

cleaned tube tests, calculate the cleaned tube overall heat transfer coefficient , Uc • Then, mathematically add the specified fouling resistance to the 

reciprocal of the cleaned tube ~ and calculate the 

fou led ratings for publication, using the following 

methods, as applicable. 

(a) Tube-in -tube (counter flow arrangement 

shown - parallel fl ow also covered). 

(b) Single tu be passshell-in -tube (counter now 

arrangement shown - parallel flow also cove red). 

~1'-------------rrFo I- ~· + l" 

(c) Coil-in -s hell, single pass (co unler flow 

arrangemen t shown - parallel flow also 

covered). 

~ 
________________________ ARI STANDARD 470-87

Obtain Uc from the following equation

U - q c - A x (LMTD)c

where (LMTD)c is defined by:

Counterflow Parallel Flow

Now calculate the following:

Chot = (W cp)r = hot fluid (refrigerant)

capacity rate at rating conditions, Btu/(hr F)

[WfOC)

Ccold = (W cp)u' = cold fluid (water) capacity rate at rating conditions, Btu/(hr F)

[W/°C)

Flow Length Flow Length

the smaller of Chot or Ccold

the larger of Chot or Ccold

Cmin (tre - lwe), Btu/hr. [W]

(Rt

)~Cmin) , dimensionless

where Rt is based on area A

for counterflow:

for parallel flow:

The actual heat transfer under fouled conditions, ~, is calculated from

= E qmax

where E is determined for either counter flow or

parallel flow arrangements of the exchanger

types shown in 5.4.2, items a, band c.

Counterflow:

Symbols

Total heat transfer area, ft. 2 [m2]

Flow-stream capacity rate (Wep), Btu/(hr F)

[WfOC)

Specific heat at constant pressure, Btu/(lbm F)

[kj/kg .0C]

Base of natural logarithm

Log mean temperature difference, F rOC]

Number of exchanger heat transfer units

Total heat transferred, Btu/h. [W]

Total thermal resistance, hr sq ft F/Btu

[m2 ·°c/W]

1 - (Cmin/Cmax) e-Ntu(l - c",inICl7w:r)

Parallel flow

E =

E = 1 - eNtu(l + c",in1c",ax)

1 + Cmin/Cmax

Now having the actual heat transfer under fouled

conditions, the leaving water and refrigerant

temperatures can be calculated from:

tree t,.'e + ~/Ccold

tre tre - qJChor

The combination of ~, tree and tre define the fouled

ratings at the given operating conditions.

A

C

c"

e

LMTD

Ntll

q

R

A x (LMTD)c

q

Rc =_1Uc

2. Basing calculations on inside surface area

The next step in determination of fouled ratings is

the calculation of the total thermal resistance including fouling. This is found by adding the specified fouling resistance to the cleaned-tube overall

resistance, as illustrated below.

The total thermal resistance is equal to the reciprocal of the overall coefficient of heat transfer.

A. Refrigerant Outside Tubes (fouling inside)

1. Basing calculations on outside surface area

2. Basing calculations on inside surface area

~; = R,.; + rn

B. Refrigerant Inside Tubes (fouling outside)

1. Basing calculations on outside surface area

3

EE-RM-90-201 COMMENT OOR18

________________________ ARI STANDARD 470-87 

Obtain U ... from the following eq uation 

u - q ... - A x (LMTD) .. 

where (LMTD).. is defined by: 

Cowlierflow Parallel Flow 

~t" 

~~t ~ .' 

t., 

Flow Length 

for counterflow: 

for parallcl flow: 

R ow Length 

(LMT D), = (~, - <.',) - (~, - <.. ) 

' \ell n Irt' t .. J 

The tolal therma l resistance is equal to the reciprocal of the ove rall coefficient of heal transfe r. 

R" = _I = A x (LMTD), 

u, q 

The next step in determination of foul ed ra tings is 

the calculation of the total thermal resistance including fouling. This is found by adding the specified fouling resistance to the cleaned-lube overall 

resistance , as illustrated below. 

A. Refrigerant Outside Tubes (fo uling inside) 

I. Basing calculations on outside surface area 

2. Basing calculations on inside surface a rea 

I = R,..I + TIf 

B. Refrige rant Inside Tubes (fouling outside) 

J. Ba si ng ca lculations on ou tside surface a rea 

RIa = R.-u + r/<> 

2. Basi ng ca lculations on illside surface a rea 

Now calculate the following: 

Cit'" = (W c,,)r = ho t flu id (refrige rant) 

capacity ra te at rating conditions, BtU/(hr F) 

[WrC] 

old = (W cp ) ... = cold fluid (wate r) capacity rate a t rati ng conditi ons, Blu/(hr F) 

[W/"C] 

c",in = the smaller of c...", or c"Old 

c",,, ... = the larger of 4", o r d 

q",,,... c". ~ (1,., - '-), Btulhr. [W] 

NIII = (Rr) c""n ) , dimensionless 

where Rr is based on area A 

The actual hea t transfer under fouled conditions, q" is calculated from 

C!J = f q ... " ... 

whe re E is de tennined for eithe r counter flow or 

paralle l flow a rrangements of the exchanger 

types shown in 5.4.2, items a , band c. 

Cou nterfl ow: 

, = c--c~~-~e~~N~'~(t~ C.~,~" C.~.~r~)~_c 

1 - (C"'in/c"." ... ) e Nfu(l - c",fMICm"r) 

Parall el fl ow 

f = 1 - c=N,u(1 + c",iM1c",ar) 

1 + C", C", ..... 

Now having the actual heat transfer under fou led 

conditio ns, the lea vi ng water a nd refrige ra nt 

tempe ratures ca n be calculated from: 

t,..( l"., + <trIc..old 

The combina tion of q" t.. ... and 1,. .. define the fouled 

ratings at the give n ope rating conditions. 

Symbols 

A Total heat transfe r area , ft. 2 (m1] 

C Flo w-stream capacity rate (Wc,,), Btu/(hr F) 

[Wr C] 

c., Specific heat a t constant pressure , Btu/(lb", F) 

[kjlkg· "C] 

e Base of natural logarithm 

LMTD Log mean tempe rature difference , F (0C] 

Nlit Number of exchanger heat transfe r units 

q Total heat transferred , Btulh. IWJ 

R Total the rmal resistance , hr sq fl FIBtu 

[ml . OO W] 

3 
ARI STANDAR D 470-87 _

Table 1. Standard Rating Conditions

Saturated Actual

Type Temperature Temperature Temperature Temperature

of Entering of Entering of Entering of Leaving System Refrigerant Refrigerant Water Water

Vapor Vapor

F °C F °C F °C F °C

Air cooled 125 51.7 220 104.4 90 and 120 32.2 and 48.2 140 60

Water cooled lOS 40.6 180 82.2 90 and 120 32.2 and 48.2 140 60

r Individual thermal resistance term,

hr sq ft FlBtu [m2 ·°c/W]

t Temperature, F [0C]

U Overall heat transfer coefficient, Btulh sq ft F

[W/m2 .oCl

W Mass flow rate, Ibm/hr. [kg/s]

E Exchanger heat transfer effectiveness

Subscripts

c Cleaned

e Entering

f Fouled or fouling

I Inside

e Leaving

o Outside

r Refrigerant

w Water

5.5 Tolerances. To comply with this standard, published heat exchange effect shall be based on data obtained in accordance with the provisions of this section,

and shall be such that any production unit selected at

random and tested in accordance with this section will

have a useful heat exchange effect not less than 95 per

cent of the published rating, a water pressure drop not

more than 110 per cent of the published water pressure

drop and a refrigerant pressure drop not more than 110

percent of the published refrigerant pressure drop.

4

Section 6. Safety Recommendations and

Sanitary Provisions

6.1 Safety Recommendations. It is strongly recommended that the product be designed, constructed, assembled and installed in accordance with nationally recognized safety standards and codes appropriate for the

product covered by this standard.

6.2 Sanitary Provisions. Certain jurisdictions may require provisions to preclude possible potable water contamination by refrigerant.

Section 7. Marking

7.1 Each desuperheater/water heater shall have the

following minimum information shown in a conspicuous

place:

a. Name of manufacturer

b. Manufacturer's model number

c. Design working pressure for the water side

d. Design working pressure for the refrigerant side

Section 8. Voluntary Conformance

8.1 Conformance. While conformance with this standard is completely voluntary, conformance shall not be

claimed or implied for products or equipment within its

Purpose (Section 1.) and Scope (Section 2.) unless such

claims meet all of the requirements of the Standard.

EE-RM-90-201 COMMENT OOR18

ARI STAN D A RD 47 0 -8 7 ____ _ __________________ _ 

Table 1. Standard Rating Conditions 

Saturated AClUal 

Typ" Temperature Temperature 

System of Entering of Emerlng 

Refrigerant Refrigerant 

r 

Vapor 

F ·c 

Air cooled 115 5 1.7 

Walcrcookd 105 40.6 

Individual thermal resistance term, 

hr sq ft F/Btu [mI . DOW] 

Temperature , F [0C] 

Vapor 

F 

220 

180 

t 

U Overall heat transfer coefficient, Btulh sq ft F 

[W/ml . GC] 

w 

, 

Mass flow rate , lbm/hr. I kg/sJ 

Exchanger heat transfer effectiveness 

c Cleaned 

e Entering 

f Fouled or fouling 

i Inside 

{ Leaving 

o Outside 

r Refrigerant 

w Water 

Subscripts 

5.5 Tolerances. To comply wit h this standard. published hea t exchange effect shall be based on data obtained in accordance with thc provisions of this section. 

and shall be such th at any pmduction unit selected 111 

random and tested in accordance with this sectio n will 

have a use ful heat exchange effect not lcss than 95 per 

cent of the published rating, a wate r pressure drop not 

more than 110 pe r ce nt of the published wa ter prl!ssure 

drop an d a refrigeran t pressure drop not more than 110 

percent of the published refrigerant pressure drop. 

4 

'C 

104.4 

82.2 

Temperature Temperature 

of Emcring of lA:aving 

Water Water 

F ·C F ·C 

90 and 120 32.2 and 48.2 14O 60 

90 and 120 32.2 and 48.2 140 60 

Section 6 , Safety Recommendations and 

Sanitary Provisions 

6.1 Safety Recommendations. It is strongly recommended that the product be designed, constructed , assembled and installed in accordance with nationally recognized safety standards and codes appropriate for the 

product covered by this standard. 

6.2 Sanitary Provisions. Certain jurisdictions may require provisions to preclude possible potable water contamination by refrigerant. 

Section 7 . Ma rking 

7.1 Each dcsupe rheater/watc r heater shall have the 

following minimum info rma tio n shown in a conspicuous 

place: 

a. Name of manufacturer 

b. Manufacturer's model number 

c. Design working pressure for the water side 

d. Design working pressure for the refrigerant side 

Se ction 8. Vo luntary Conforma n ce 

8.1 Conformance. While conformance with this standard is completely voluntary, conformance shall not be 

claimed or implied for products or equipment within its 

Purpose (Section I.) and Scope (Section 2.) unless such 

claims meet aU of the requirements of the Standard. 
_______________________ ARI STAN DARD 470-87

APPENDIX A. METHOD OF TESTING

DESUPERHEATER/WATER HEATERS

Section A1. Purpose

AI.I Purpose. This appendix prescribes methods of

testing for rating desuperheater/water heaters.

Section A2. Scope

A2.1 Scope. This appendix applies to desuperheater/

water heaters supplied as a separate component.

Section A3. Definitions

A3.1 Desuperheater/Water Hearer. A factory-made assembly of elements by which the flows of refrigerant

vapor and water are maintained in such a heat transfer

relationship that the refrigerant vapor is desuperheated

and the water is heated.

A3.2 Useful Heat Exchanger Effect. The useful heat

transferred shall be the product of the mass flow of

water, the specific heat and the temperature difference

between entering and leaving water.

A3.3 Total Heat Exchange Effect. The total heat removed from the refrigerant in the heat exchanger. This

is the sum of the useful heat exchange effect and the

heat loss through the external surfaces of the heat exchanger to the ambient air.

A3.4 Nominal Refrigeration System Capacity. The

cooling effect produced shall be the product of the refrigerant mass flow of refrigerant and the difference in

enthalpy between the refrigerant entering the evaporator and the refrigerant leaving the evaporator.

Section A4. Expression of Test Results

A4.1 Terms Recommended for Expressing Test ResuIts.

A4.t.l Test results shall be expressed in the following terms:

a. The useful heat transfer effect, Btuh [W)

b. Temperature of entering water, F rOC)

c. Temperature of leaving water, F rOC)

d. Temperature of entering vapor, F rOC]

e. Water flow rate, gpm [Us]

f. Refrigerant mass flow rate, lbs/hr [kg/s]

g. Water pressure drop through heat exchange,

psi [kPa]

h. Vapor pressure drop through heat exchanger, psi [kPa]

I. Pressure of vapor entering heat exchanger,

psig [kPa]

j. Refrigerant designation

Section AS. Test Methods

A5.1 Standard Test Methods.

A5.1.1 Tests shall consist of measurement of the

following at specified conditions:

a. Temperature of entering and leaving water,

F [0C]

b. Temperature of entering and leaving vapor,

F [0C]

c. Pressure of entering vapor, psig [kPa]

d. Water pressure drop through heat exchanger, psi [kPa)

e. Vapor pressure drop through heat exchanger, psi [kPa]

f. Water flow rate, gpm {Us]

g. Refrigerant mass flow rate, Ib/hr Ikgls] (measured on liquid side)

h. Ambient temperature, F [0C]

A5.t.2 The total heat transfer effect shall be determined by:

a. Multiplying the mass flow rate of water by

the specific heat and temperature difference

between entering and leaving water (useful

heat transfer effect) and adding to this the

heat lost by the refrigerant vapor through the

external surfaces of the heat exchanger (see

A5.1.6).

b. Multiplying the refrigerant mass flow rate by

the enthalpy differences between entering

and leaving refrigerant.

A heat balance calculated between a and b shall

be within ± 5%.

A5.t.3 The water flow rate shall be determined

in accordance with A6.4.1.

A5.t.4 Rate of refrigerant flow shall be determined in accordance with A6.4.2.

A5.t.5 The enthalpy difference between the entering and leaving refrigerant shall be determined

from temperature and pressure measurements and

the applicable thermodynamic properties of the

refrigerant.

A5.1.6 The heat lost through the external surfaces of the heat exchanger to the ambient air shall

be determined by:

All t,1l q=~

5

EE-RM-90-201 COMMENT OOR18

ARI STANDARD 470-87 

APPENDIX A. METHOD OF TESTING 

DESUPERHEATER/WATER HEATERS 

Section A 1. Purpose 

At.l Purpose. Th is append ix prescribes me thod s of 

testing for rating desupcrheatc r/wate r heaters. 

Section A2. Scope 

A2.1 Scope . This appendix applies to desupe rheate rl 

water hea te rs supplied as a sepa rate component. 

Section A3. Definitions 

A3. 1 DesuperheorerlWaler Heater. A faewry-made assembl y of elemen ts by which the flows of refrige rant 

vapor and wa ter are ma intained in such a heal transfer 

rcia tionshi p th aI the refrige rant va por is dcsupcrhcatcd 

and the water is hea ted. 

A3.2 Useful Heal Exchanger Effeci. The use ful heal 

transferred shall be the product of the mass flow of 

wa ter, the specific hea l and the temperatu re difference 

between e ntering and leaving water. 

A3.3 Total Heat Exchange Effect. The tolal heat removed from the refrigeran l in the heal exchanger. This 

is the sum of the useful heat exchange effect and the 

heat loss through the external surfaces of the heat exchanger to the ambient air. 

A3.4 Nom inal Refrigeration System Capacity. The 

cooli ng effect produced shall be the product of the refrigerant mass flow of refrigerant and the difference in 

enthalpy between the refrigerant entering the evaporator and the refrigerant leaving the evaporator. 

Section A4. Expression of Test Results 

A4.1 Terms Recommended for Expressing Test Results. 

A4.t.l Test results shall be expressed in the following terms: 

a. The useful heal transfer effect . Btuh [W] 

b. Temperature of e nteri ng water, F (OCl 

c. Te mperature of leavi ng wate r, F rOC] 

d. Temperature of e ntering vapor. F [OCl 

e. Water How rate , gpm (Us] 

f. Refrigerant mass flow rate , Ibslhr [kg/s] 

g. Water pressu re drop th rough hea t exchange. 

psi IkPa] 

h. Vapor pressu re d rop through hea t exchange r, psi [kPa] 

I. Pressure of vapor e ntering heat exchanger, 

psig [kPa] 

j. Refrigerant designation 

Section AS. Test Methods 

AS.! Standard Test Methods. 

AS.l.l Tests shall co nsist of measurement of the 

following at specified conditions: 

a. Tempe rature of entering and leaving water. 

F [0C] 

b. Te mperature of entering and leaving va por. 

F loCI 

c. Pressure of ente ring vapor. psig [kPa ] 

d. Wat e r p ress ure dro p th ro ugh heat exchange r, psi [k PaJ 

e. Vapor pressure drop throu gh heat exchange r, psi lkPaj 

f. Water flow rate , gpm [Us] 

g. Refrige rant mass flow rate. Iblhr [kg/sl (measured on liquid side) 

h. Ambie nt tempe rature, F roC] 

AS.t.2 The total heat transfer effecl sha ll be dete rmined by: 

a. Multiplyi ng the mass flow rate of wate r by 

the specific hea t and temperature differe nce 

between entering and leaving water (useful 

heal transfer effect) and adding to this the 

heat lost by the refrige rant vapor through the 

exte rnal surfaces of the heat exchanger (see 

AS. 1.6). 

b. Multiplyi ng the refrigerant mass How rate by 

the entha lpy diffe rences be tween entering 

and leaving refrigerant. 

A heat balance calculated between a and b shall 

be with in ± 5%. 

AS.1.3 The waler flow rate shall be determined 

in accord ance with A6.4. 1. 

AS.1.4 Ra te of refrige rant flow shall be determined in accordance with A6.4.2. 

AS.1.S The ent halpy difference between the ente ring a nd leaving refrigerant shall be de termined 

from te mperatu re and pressure measureme nts and 

the applicabl e thermodynamic properties of the 

refrigerant . 

AS.l .6 The heat lost th rough the ex ternal surfaces of the heat exchanger to the ambient air shall 

be dete rmined by: 

A6<". 

q -RS 
ARI STAN DARD 470-87 _

Where:

q heat loss through external surfaces, Btu/h

[W]

A external surface area, sq ft [m2 ]

Li t", log mean temperature difference, F [0C]

(calculated between entering and leaving

refrigerant temperature and the average

ambient air temperature)

x 1 R = - + - hr ftl F/Btu [m2 • °C/W] k hs '

Where:

x = insulation thickness, ft [m]

k thermal conductivity of insulation, Btu/h

ft F [W/m .0C]

hs = surface film coefficient

2 Btu/h ft2 F [11.36 W/m2 • 0c]

A5.1.7 The heat absorbed by the water is the

product of the mass flow, the specific heat and the

temperature difference between entering and leaving water.

A5.I.S The heat rejected from the refrigerant is

the product of the refrigerant mass flow rate and

the enthalpy difference between the refrigerant entering and leaving the desuperheater.

Section AG. Instruments, Test Apparatus,

and Thermodynamic Properties

A6.1 General.

A6.1.1 Instruments, whose types and accuracies

are listed below, shall be calibrated against standards before and after each test.

A6.2 Temperature Measuring Instruments.

A6.2.1 Temperature measurements shall be

made in accordance with ASHRAE Standard

41.1-74.

A6.3 Pressure Measuring Instruments.

A6.3.1 All pressure measuring instruments shall

have an accuracy within the limits of ± 1% of the

absolute pressure readings or ± 2% of the differential pressure readings.

A6.4 Flow Measuring Instruments.

A6.4.1 Water Flow Measuring Instruments.

A6.4.1.1 Accuracy of flow meter shall be

within ± 2% within the range of flows measured.

6

A6.4.2 Refrigerant Flow Measuring Instruments

A6.4.2.1 Direct volume flow measurement

shall be made with one or more of the following

instruments:

a. Liquid refrigerant quantity meter

b. Liquid refrigerant flow meter

c. Gaseous refrigerant flow meter

A6.4.2.2 A refrigerant calorimeter may also

be used for indirect measurement of the refrigerant flow. In this approach, the calorimeter is

used to accurately measure the amount of heat

required to evaporate and superheat the refrigerant flowing through it. The rate of refrigerant flow is determined by dividing the heat input, including leakage losses, by the enthalpy

difference between the entering and leaving refrigerant.

A6.4.2.3 Accuracy of either the direct or indirect refrigerant flow measurement shall be

within ± 2% within the range of flows measured.

A6.4.2.4 Instruments shall be applied and

used in accordance with ASME PTC 19.5.3 and

19.5.4.

A6.4.3 Thermodynamic Properties of Refrigerants. Thermodynamic properties of refrigerants

shall be obtained from the current issue of the

ASHRAE Refrigerant Tables, Charts and Characteristics (American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.).

Section A7. Test Procedure

A7.1 General.

A7.1.1 The desuperheater/water heater, the

selected instruments, and test apparatus are assembled, connected, tested, dehydrated,

evacuated, and charged with refrigerant. If necessary, a refrigerant superheater may be used, to

assure accuracy of measurements and to obtain

specified conditions.

A7.1.2 The water side surfaces of the heat exchangers should be cleaned immediately prior to

the test. This method gives cleaned-tube test results.

A7.1.3 The refrigerant system should be checked

for non-condensables. Non-condensables present

for a test intended for rating should not exceed that

amount which increases the condenser pressure

more than the equivalent of 0.5 F [0.3°C].

A7.2 Operation and Limits.

A7.2.1 Start the system and obtain and maintain

the specified conditions in accordance with the

following tolerances:

EE-RM-90-201 COMMENT OOR18

ARI STANDARD 470-87 _______________________ _ 

Where: 

q = heat loss through external surfaces, BtU/h 

[W] 

A = eXlernal surface area, sq fl [mIl 

6 I", = log mean lempe ralUre difference, F rOC] 

(calculated between entering and leavi ng 

refrige rant temperature and Ihe average 

ambie nt air temperature ) 

, I 

- + - hr ft l F/Bm 1m! ' °C/W I 

k h, ' R ~ 

Where: 

x = insulation thickness, ft [m1 

k = thermal conductivity of insulation , Btulh 

ft F [W/m . 0C) 

h. = surface film coefficient 

= 2 Btu/h ft2 F 111.36 W /m2 • 0c] 

AS.I.7 The heal absorbed by the wate r is the 

product of the mass flow, the specific heat a nd the 

te mpe rature difference between e nte ring and leaving water. 

AS.I.S The heat rejected from the refrigerant is 

the product of the refrige rant mass flow TalC and 

the enthalpy difference be tween the refrigerant entering and leaving the desuperheater. 

Section A6. Instruments, Test Apparatus, 

and Thermodynamic Properties 

A6.1 General. 

A6.1.1 In struments, whose types and accuracies 

are listed below, shall be calibrated against standards befo re and after each test. 

A6.2 Temperature Measuring Instruments. 

A6.2.1 Temperature me asureme nts s hall be 

made in accordance with ASH RAE Sta ndard 

41.1 -74. 

A6.3 Pressure Measuring Instrumenls. 

A6.3.1 All pressure measuring instruments shall 

have an accuracy within the limits of ± 1% of the 

absolute pressure readings or ± 2% of the differential pressure readings. 

A6.4 Flow Measuring InstrumenlS. 

6 

A6.4.1 Warer Flow Measuring Inslruments. 

A6.4.1.1 Accuracy of flow meter shall be 

withio ± 2% within the range of flows measured. 

A6.4.2 Refrigeranl Flow Measuring InSlruments 

A6.4.2.1 Direct volume flow measurement 

shall be made wit h one or more of the following 

instruments: 

a. Liquid refrige rant quantity meter 

b. Liquid refrigerant flow me ter 

c. Gaseous refrige rant flow mete r 

A6.4.2.2 A refrige ran t calorimete r may also 

be used for indirect measurement of the Tefrigera tli flow. In this approach , the calorimeter is 

used to accurately measure the amount of heat 

required to evaporate and superheat the refrige rant flowing through it. The rate of refrigerant fl ow is determined by dividing the heat input. including lea kage losses, by the enthalpy 

difference between the ente ring and leaving refrigerant. 

A6.4.2.3 Accuracy of either the direct or indirect refrige rant How measurement shall be 

within ± 2% within the range of flows measured. 

A6.4.2.4 In strume nts shall be applied and 

used in accordance with ASME PTe 19.5.3 and 

19.5.4. 

A6.4.3 Thermodynamic Proper/ies of Refrigerants. Thermodynamic properties of refrige ran ts 

shall be o btained from the current issue of the 

ASH RAE Refrigerant Tables, Charts and Characleris/ics (Ame rica n Society of Hea ting, Refrige rating and Air-Conditioning Engineers, Inc.). 

Section A7. Test Procedure 

A 7.1 Gel/eral. 

A7.t.1 The desuperheater!wat er heate r, the 

se lected instruments, and test apparatus are asse mbl ed, connec ted, tested. de hyd rated, 

evacuated, and charged with refrige rant. If necessa ry. a refrige rant superhea te r may be used, to 

assure accuracy of measurements and to obtain 

specified conditions. 

A 7.1.2 The water side surfaces of the heat exchangers should be cleaned immediately prior to 

the test. This me thod gives clea ned-tube test results. 

A 7.1.3 The refrigera nt system should be checked 

fo r non- condensables. Non-condensables prese nt 

for a test intended for rating should not exceed that 

amount which increases the condense r pressure 

more than the eq uivalent of 0.5 F [O .3"C). 

A7.2 Operation and Limits. 

A 7 .2.1 Start the syste m and obtain and mai ntain 

the specified conditions in accordance with the 

following tolerances: 
_______________________ ARI STANDARD 470-87

a. The arithmetic average of pressure readings

used to determine refrigerant enthalpies and

refrigerant saturated temperatures shall not

vary from the required values, by more than

2.0% of their absolute values, nor shall the

individual pressure readings vary by more

than this amount from the average value.

Pressure readings shall be converted to absolute values to determine refrigerant saturated temperatures.

b. The arithmetic average of temperature readings of water and vapor entering and leaving

the desuperheater/water heater shall not

vary from the specified value by more than

1.0 F [O.6°C] nor shall the individual readings

vary by more than this amount from the average value.

A7.2.2 After establishment of steady flow conditions, all required readings shall be taken at intervals of not less than fifteen minutes, and the test

shall be continued until two consecutive sets of

readings are within the specified limits.

A7.2.3 The test re<:ord shall include the date,

observers' names, essential identifying physical

data of the desuperheater/water heater tested, refrigerant used, all test readings, reference to instrument calibrations and computations, and the

determined results.

Section A8. Computation of Results

AS.1 The useful heat exchan,ger effect, q, is by definition the heat gained by the water and is the product of

the mass flow of the water, the specific heat and the.

temperature difference of the water.

q = we"dt = [1000 w e"llt]

Where:

w Mass flow rate, lbs/hr [kg/s]

Cp Specific heat of the water, Btu/lbF [kJ/kgOC]

Ilt Temperature difference between the entering

and leaving water, F [0C]

q Heat transferred, Btu/h [W]

7

EE-RM-90-201 COMMENT OOR18

____ ___________ _____ _ ___ ARI STANDARD 470 - 87 

a. The arithmetic ave rage of pressure readings 

used to dete rmine refrige rant enlhalpies and 

refrige rant saturated temperatures shall nOI 

va ry from the required values, by morc than 

2.0% of thciT absolute values, no r shall the 

individual pressure readi ngs vary by morc 

than this amo unt from Ihe average value. 

Pressure readings shall be conve rted to absolute va lues 10 determine refrige rant sa tu -

rated temperatures. 

b. The arithmetic average of temperature readings o f water and vapor entering and leavi ng 

Ihc dcsupe rhea tc r/w3tc r heale r shall nOI 

va ry from the specified value by more Ihan 

1.0 F [O.6°C] nor shall thc individual readings 

va ry by mo re than this amount from the average va luc . 

A 7 .2.2 After establishment of steady How con· 

ditio ns, all rcquired readi ngs shall be taken at in· 

tcrvals o f not Icss tha n fifteen minutes, and the test 

shall be continued until two consecutive sets of 

readings are within the specified limits. 

A 7.2.3 Thc test record shall include the date, 

o bse rve rs' names, essen tial identifying physical 

data of the desuperheater/water heater tested. re· 

frigerant used, all lest readings, reference to in· 

strument cali brations and computations, and the 

determined results. 

Section A8. Computation of Res ults 

AS.1 The use ful heat exchanger effect, q. is by defini· 

tion the heat ga ined by the wa ter and is the prod uct of 

the mass flow of the water, the specific heat and the . 

temperature differe nce of the water. 

q ::: wc..At '" [IOOOwc"AtJ 

Where: 

W : Mass flow rate, lbs/hr [kg/s] 

.. : Specifi c heal of the water, Bl ullbF [k J/kg°C] 

", : Tempe rat ure difference be twee n the e ntering 

and leaving wa ler, F [0C] 

q : Heat transferred, Btuth (W] 

7