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UDC 621.56/.59.001.4
IS0
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
IS0 RECOMMENDATION
R 916
TESTING OF REFRIGERATING SYSTEMS
1st EDITION
December 1968
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 916, Testing of refrigerating systems, was drawn up by Technical Committee
ISO/TC 86, Refrigeration, the Secretariat of which is held by the British Standards Institution (BSI).
Work on this subject was entrusted to Sub-Committee ISO/TC 86/SC3, the Secretariat of which is held by
Belgium. The work began in 1960, and was carried out using as a basis for discussion the “Recommendations for
an international code for refrigerating machines”*, published in November 1957 by the International Institute
of Refrigeration. The work led to the adoption of a Draft IS0 Recommendation.
In March 1967, this Draft IS0 Recommendation (No. 1153) was circulated to all the IS0 Member Bodies
for enquiry. It was approved, subject to a few modifications of an editorial nature, by the following Member
Bodies :
Australia Germany Sweden
Greece
Belgium Switzerland
Canada Hungary
U.A.R.
Chile Italy United Kingdom
Czechoslovakia Netherlands
Yugoslavia
Denmark New Zealand
France Poland
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council? which decided,
in December 1968, to accept it as an IS0 RECOMMENDATION.
* Bulletin IIF - 177 Boulevard Malesherbes, Paris 17e - Volume XXXVIII, No. 1.
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HO/R 9164968 (E)
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CONTENTS
Page
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6
1. Units .
......................... 7
2. Definitions and test data
....................... 8
3. Determination of performance
.......................... 8
4. Organization of tests
9
.....................
5. Measurement of refrigerating capacity
..................... 17
6. Measurement of energy consumption
.......................... 17
7. Measuring instruments
..............................
18
8. Tolerances
........................... 19
9. Statement of results
....................... 19
Numerical tables - Diagrams
10.
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ISO/R 916-1968 (E)
December 1968
R 916
IS0 Recommendation
TESTING OF REFRIGERATING SYSTEMS
INTRODUCTION
This IS0 Recommendation has for its object the determination of the technical performance of a refrigerating
system, but not of the functional duty of a complete installation or of the performance of its individual
components.
The term refrigerating system implies the conventional vapour compression type consisting of compressing,
condensing and evaporating apparatus, together with the interconnecting piping, and the accessories necessary to
complete the refrigerant circuit.
The determination of technical performance for other refrigerating systems such as, for example, absorption
machines and ejector type machines is not provided for in this IS0 Recommendation, but may be dealt with in
other IS0 Recommendations.
The only tests envisaged are those of complete refrigeration systems operating normally and under steady working
conditions (frequency, voltage, water supply, etc.), and where the refrigerant is entirely in a liquid state at entry
to the expansion valve.
The direction of the tests should be entrusted only to persons possessing the necessary technical knowledge and
experience.
When none of the combined methods given in this IS0 Recommendation is practicable or acceptable, it may be
possible to restrict the test to a determination of the performance of the compressor only, in accordance with
IS0 Recommendation R 9 17, Testing of refrigerant compressors.
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ISO/R 916-1968 (E)
1. UNITS
Conversion factor8
Quantity Symbol
I
T,O K K “R -
absolute temperature
t “C = T K - 273.15
“F
customary temperature “c
t, 0
t”F=T”R-459.67
98 066.5 N/m*
1 kgf/cm* =
N/m* lbf/in*
pressure kgf/cm*
P
1 lbf/in* = 6894.76 N/m*
I
-
lb/ft3 1 lb/ft3 = 16.0185 kg/m3
density (mass density) kg/m3
P kg/m3
I I
I
1 kcal,,/kg = 4186.8 J/kg
specific enthalpy h Btu/lb
J/kg kc+&g
1 Btu/lb = 2326 J/kg
1 kcal,,/(kg.K) = 4186.8 J/(kg*K)
S Btu/(lb*“R)
specific entropy J/(kgK) kcal&(kg*K)
1 Btu/(lbeOR) = 4186.8 J/(kg*K)
1 kcaliT/(kg*oC) = 4186.8 J/(kg*K)
Btu/(lb=“F)
specific heat capacity C J/(kgeK) kcal,T /(kg*Oc)
1 Btu/(lb*“F) = 4186.8 J/(kg.K)
specific latent heat 1 kcal,,/kg = 4186.8 J/kg
I Btu/lb
J/kg kc&,/kg
of evaporation 1 Btu/lb = 2326 J/kg
1 kcalIT/(h*m-“C) = 1.163 W/(m*K)
W/(m*K) kcalIT/(h~m*“c)
thermal conductivity x Btu/(h.ft.“F)
1 Btu/(h.ft*‘F) = 1.730 73 W/(m*K)
surface coefficient 1 kcallT/(h*m2 *“C) = 1.163 W/(m* *K)
W&m* *K) * -“c) Btu/(h.ft* .“F)
cy kcal,,/(h*m
of heat transfer 1 Btu/(h.ft * *OF) = 5.678 W/(m* ‘K)
overall coefficient 1 kcal,,/(h*m * -“C) = 1.163 W/(m* *K)
K W/(m* SK) * -“C) Btu/(h-ft* .“F)
kcal,,/(h*m
of heat transfer 1 Btu/(h.ft* e” F) = 5.678 W/(m* l K)
kinematic viscosity V m2/s m* /s ft2/s 1 ft* /s = 0.092 903 0 m*/s
St 1 St = 0.0001 m*/s
mass flow rate lb/h 1 lb/h = 126 X IO+ kg/s
kg/s kg/h
qrn
I
I I
1 kcal,,/h = 1.163 W
heat flow rate kcal&h Btu/h
1 Btu/h = 0.2931 W
~~
refrigerating capacity
1 fg/h(= 1 kcal15/h)= 1.163 W
(overall, net, useful)
1 ton of refrigeration (= a heat flow rate
of 12 000 Btu/h removed by the refrig-
erating system from the cold body)
= 3516.85 W
refrigerating performance
(overall, net, useful)
-
efficiency
power
‘i
2
area of an exchange surface A m* m* ft2 . -
- - - -
relative humidity
9,
specific humidity
- - - -
X
(mixture ratio)
.
I
It is recommended that the figures 1, 2, 3, etc. be used to indicate any state point of the refrigerant (see, for example, Fig. 1).
Inferior indexes ambient atmosphere, air a
water
heat transfer liquid (brine, alcohol, etc.) ;Y
refrigerant (no index)
saturated S
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ISO/R 916-1968 (E)
2. DEFINITIONS AND TEST DATA
2.1 Definitions
2.1.1 Overall refrigerating capacity. The rate at which heat is removed from external media by the refrigerant.
The only heat quantities excluded from this refrigerating capacity are those which result from internal
heat exchanges within the refrigerating circuit.
It should be noted that, in many cases, the overall refrigerating capacity can be obtained from the
difference in specific enthalpy of the refrigerant entering the compressor and of the refrigerant leaving
the condenser or the liquid sub-cooler, if any, multiplied by the mass flow of refrigerant circulated.
2.1.2 Net refrigerating capacity. The rate at which heat is removed by the refrigerant from the cooling
medium which is used to transmit the refrigerating effect.
2.1.3 Useful refbigerating capacity. The rate at which heat is removed by the refrigerant or by the secondary
cooling medium between two specific points, taking into account the conditions of utilisation.
2.2 Test data
2.2.1 One of the three refrigerating capacities defined under clause 2.1 should be stated.
2.2.2 In the case of refrigerating systems having several stages of evaporation and carrying out partial
refrigerating duties, the intermediate temperatures should also be given.
2.2.3 In all cases, the following figures of consumption should be given :
(a) the intake of power (in terms of consumption of electricity, coal, steam, fuel oil, etc., together
with the requisite data regarding characteristics);
water for cooling, if used, together with full details of supply.
(b)
2.2.4 It is advised that the following operating details should be included in the data :
(a) the refrigerant used;
the speed of rotation of the compressor;
(b)
(c) if applicable, the pressure of the refrigerant at compressor suction, at the condenser inlet and at
the evaporator outlet;
when the overall refrigerating capacity is specified (see clause 2.1. l), the conditions of the
(4
refrigerant at the expansion valve and at the entry of the compressor;
e when the net refrigerating capacity is given (see clause 2.1.2),
0
-
either the temperature of the heat transfer medium at the entry and exit of the
condenser and of the evaporator,
--
or the temperature of the heat transfer medium, either entering or leaving the
condenser and the evaporator, together with the corresponding rate of flow. Preference
should be given to the following :
(1) for an evaporative condenser : the inlet temperature of the water, the temperature
of the air and the relative humidity of ambient air (generally the temperature at
inlet);
(2) for an air cooled evaporator : the inlet temperature of the air and, if appropriate,
its relative humidity;
(3 j jbr a brine circulation evporator : the outlet temperature of the brine.
2.2.5 It is not necessary to assess the flow of the heat transfer medium in an evaporator when its temperature
should be practically uniform around the evaporator, in a space or in a reservoir (e.g. a brine tank).
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ISO/R 916-1968 (E:
3. DETERMINATION OF PERFORMANCE
3.1 The determination of the technical performance required in the Introduction concerns the following data
in particular :
3.1.1 The refrigerating capacity given in clause 2.2.1 above, which should be so chosen that it is capable of
practical verification.
3.1.2 The corresponding consumption given in clause 2.2.3.
3.1.3 The conditions of operation given in clause 2.2.4.
3.2 The data should be capable of verification under the conditions of operation laid down for the test.
3.2 As the test conditions are subject in practice to temporary unclassifiable variations, it is advised that the
data be set out in such a way that they are applicable throughout the specified period of the test.
3.3.1 It is therefore advisable that the data in clauses 2.2.1 to 2.2.3 should provide for varying conditions in
the neighbourhood of the conditions of operation in clause 2.2.4, and especially for different values
in the neighbourhood of the temperatures given. For ease of interpolation, and in order to avoid
adjustment by calculation, these values may be presented3raphically, within the limits of fluctuation,
for each pair of temperatures specified. Maximum permissible deviations should be laid down.
3.3.2 So far as the influence of temporary variations in other operating conditions is concerned, this should
be the subject of an agreement between the interested parties.
4. ORGANIZATION OF TESTS
exclusively to refrigerating plant operating under
4.1 The tests refer steady working conditions (see
Introduction).
4.2 Preliminary tests for adj ustment to specified condi tions should be carried out
before the official test is
started. After this, only agreed a .djustments should be made du .ring the ac tual test period.
4.3 The tests should be made under the condi tions defined in clause 4.4, which should be as close as possible
to the working conditions.
4.4 The stability of operation (steady condition) should preferably be checked by plotting successive measure-
ments over a sufficiently long time interval and until the initial and final states are the same for all
quantities essential to the verification of the data.
4.5 Readings showing an excessive variation from the mean should be disregarded.
4.6 The nu .mber of readi .ngs used for a calculation should be at least ten. The readings should
be regularly
spaced at maximum inte WdS of 20 minutes.
4.7 All measurements should be made in conformity with international rules which may be in force, or, failing
this, in conformity with the national rules accepted by those concerned. All measuring instruments should
have been tested and certified for the purpose of the test.
4.8 The refrigerating system should be provided with the necessary thermometer and pressure gauge connections.
These should be of a type suitable for the purpose for which they are to be used, so as to avoid errors in
measurement (frosting, longitudinal heat flow along pipes, etc.).
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9
ISO/R 916-1968 (E)
9
.
4.9 All equipment required exclusively for these tests should in no way interfere with normal operation or
accessibility.
4.10 It is advisable that a sightglass should be provided upstream of the expansion valve to serve as a means of
determining the level of the refrigerant. Furthermore, it is necessary to ascertain that the plant has been
purged before testing, and that the entrainment of lubricating oils is not excessive.
4.11
It is recommended that, wherever possible, two simultaneous tests should be made, with particular reference
for the second test to the indirect methods described in clause 5.2.
If it is only possible to make use of one test method, two consecutive tests should be made, except in the
case of a contrary agreement between the interested parties.
4.12 Attention is drawn to the causes of inaccuracy in measurements of liquid or vapour flow by calibrated
flow-meters (pulsation in pipelines, oil entrainment, impurities in the circuit).
5. MEASUREMENT OF REFRIGERATING CAPACITY
Direct methods
5.1
5.1.1 Overall rejkigerating capacity. When the refrigerant vapour in circulation is dry saturated or superheated
at the compressor inlet, i.e. without liquid entrained or in suspension, the overall refrigerating effect
can be calculated by the equation :
=qm (h, -k) . . . . .
(1)
@cl
State 1 is the state at the inlet flange of the compressor, and state 5 is the state at the outlet from the sub-
cooler (to be exact, the inlet flange on the expansion valve or the inlet flange of the internal heat exchanger
on the high pressure side, as shown in Fig. 1 or 2).
Specific enthalpies for the more common refrigerants are given in the tables and diagrams referred to in
clause 10.1.
The measurement of the mass flow rate of refrigerant in the low pressure circuit should be made either
by heat balance (see clause 5.1.1.1) or by calibrated flow-meter (see clause 5.1-l .2).
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ISO/R 916-1968 (E
*
51.1 .l MEASUREMENT BY HEAT BALANCE. In principle, the mass flow rate can be found from the heat
balance of any apparatus in the circuit, provided that the same flow passes through it. If any of
the refrigerant has been bled off previously into subsidiary circuits, this quantity should be taken
into account.
.(a) For single stage installations, the apparatus most suitable for establishing a heat balance is
the condenser, when this is arranged for cooling by a liquid without evaporation. The
flow rate is then given by the equation :
4
MW cw*tw + @,
. . . . .
4, =
(2)
Ah
where the inferior index w refers to the cooling liquid (in general, water).
A h represents the drop in specific enthalpy or the refrigerant in passing through the condenser.
The mass flow rate qmw of the liquid is obtained by one of the methods in common use for
the measurement of flow (calibrated tanks, orifices, etc.).
The heat flow ac is a corrective term which should be employed whenever the temperature
of the external surface of the apparatus is different from the ambient temperature. This
correction is given by the formula :
=KA (tm -ta) . . . . .
(3)
@c
where
K
is the overall coefficient of heat transfer between the fluid circulating in the
external passage of the apparatus and the surrounding atmosphere; as Qc is merely
a corrective term, it will be sufficiently accurate to use the approximate value
K = 7 W/(m*K) [K =
6 kCalfT/h*m2 l oC] when the apparatus is not insulated;
A is the surface area of the apparatus in contact with the surrounding atmosphere;
is the mean temperature of the external surface, taken for this corrective term to
Gn
be the temperature of the fluid in the part of the circulation system immediately
adjacent to it;
is the ambient temperature.
%
The corrective term Qc, positive or negative, as the case may be, should be small relative to the
other terms in the heat balance since its determination is only approximate. In this case, it
should be decided, according to the tolerance laid down in clause 8.4.1, whether it is necessary
to insulate the apparatus in order to reduce the value of this term still further.
If so, the value of K will be determined by the approximate formula for flat plates, which is as
follows :
1 1 e
-=-
+-
. . . . .
K a h
where, according to the units selected (see definition for K, below equation (3)),
a = 7 W/(m2 l K) or a = 6 kcal rT/(h-m2 -“C)
and e and h represent respectively the thickness of the insulation and its coefficient of thermal
conductivity under the prevailing conditions.
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HO/R 916-1968 (E)
I-- g’
L
5
C
OX
.
6
E
0
FIG. 1
F
0
i
2 - log P
I =
=
I ----- t
-~- -Y
5ln
Internal heat transfer : 11 Ah, -6 e Ah,- 10 11
FIG. 2
A Condenser
0
B Sub-cooler
0
Expansion valve
C
0
D Separator
0
E Evaporator
0
F Compressor
0
G Internal heat exchanger
0
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ISO/R 916-1968 (E)
r
(b) If the condenser is followed by a sub-cooler, the‘heat balance should preferably be effected
on the two pieces of apparatus taken together.
c For atmospheric condensers, the effects of evaporation often render the establishment of
0
the heat balance difficult, but it is sometimes possible to reduce this difficulty by
...