SIST EN 328:2014

SLOVENSKI STANDARD
01-november-2014
1DGRPHãþD
SIST EN 328:1999
SIST EN 328:1999/A1:2004
Prenosniki toplote - Hladilniki zraka s prisilno konvekcijo za hlajenje - Postopki
preskušanja za ugotavljanje lastnosti
Heat exchangers - Forced convection unit air coolers for refrigeration - Test procedures
for establishing the performance
Wärmeaustauscher - Prüfverfahren zur Bestimmung der Leistungskriterien von
Ventilatorluftkühlern
Échangeurs thermiques - Procédures d'essai pour la détermination de la performance
des aérofrigorifères à convection forcée
Ta slovenski standard je istoveten z: EN 328:2014
ICS:
23.120 =UDþQLNL9HWUQLNL.OLPDWVNH Ventilators. Fans. Air-
QDSUDYH conditioners
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
toplote
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 328
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2014
ICS 23.120; 27.060.30 Supersedes EN 328:1999
English Version
Heat exchangers - Forced convection unit air coolers for
refrigeration - Test procedures for establishing the performance
Echangeurs thermiques - Aérofrigorifères à convection Wärmeübertrager - Ventilatorluftkühler - Prüfverfahren zur
forcée pour la réfrigération - Procédures d'essai pour la Leistungsfeststellung
détermination de la performance
This European Standard was approved by CEN on 22 May 2014.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 328:2014 E
worldwide for CEN national Members.

Contents Page
Foreword .4
Introduction .5
1 Scope .6
2 Normative references .6
3 Terms and definitions .6
4 Symbols . 11
5 Standard capacity . 13
5.1 Basis of standard capacity data . 13
5.2 Standard conditions for the cooling capacity . 14
5.2.1 General . 14
5.2.2 Refrigerants . 14
5.2.3 Liquids . 15
5.3 Conditions for the nominal air flow rate . 15
5.4 Conditions for nominal fan power . 15
6 Manufacturer's data . 15
7 Measurements . 16
7.1 Uncertainty of measurements . 16
7.2 Measurement criteria . 17
7.2.1 Pipe side temperature measurement . 17
7.2.2 Superheating temperature . 18
7.2.3 Temperature at expansion device inlet . 18
7.2.4 Liquid temperatures . 18
7.2.5 Water temperatures (balancing air heater) . 18
7.2.6 Air temperature measurement . 18
7.2.7 Pressure measuring points . 19
7.2.8 Flow rates . 19
7.2.9 Oil content . 19
7.2.10 Non azeotropic refrigerant . 19
8 Testing methods and equipment . 20
8.1 Testing methods . 20
8.1.1 Capacity . 20
8.1.2 Air flow . 20
8.1.3 Heat exchange with the ambient . 20
8.2 Equipment . 20
8.2.1 Calorimeter room . 20
8.2.2 Refrigerant / liquid pipes . 22
8.2.3 Expansion device. 22
8.2.4 Flashgas . 22
8.2.5 Air flow measurement . 22
8.2.6 Liquid receiver . 22
9 Test procedures . 23
9.1 General . 23
9.2 Calibration of the calorimeter room . 23
9.3 Measurement of the cooling capacity . 24
9.3.1 Air humidity . 24
9.3.2 Subcooled refrigerant temperature. 24
9.3.3 Steady-state conditions . 24
9.3.4 Test duration . 24
9.3.5 Conducting the test . 25
9.3.6 Air inlet temperature . 26
9.3.7 Data to be recorded . 26
9.4 Measuring the fan performance . 26
10 Calculating the cooling capacity . 27
10.1 Heat loss factor . 27
10.2 Cooling capacity . 27
10.2.1 From the air side energy input . 27
10.2.2 From flow rate of refrigerant . 27
10.2.3 From the flow rate of liquid . 27
10.2.4 Measured capacity . 28
11 Conversion to standard conditions . 28
11.1 Cooling capacity . 28
11.1.1 General correction for atmospheric pressure . 28
11.1.2 Refrigerants with direct expansion operation . 28
11.1.3 Refrigerants - operation with liquid overfeed by pump circulation . 29
11.1.4 Liquids . 29
11.2 Calculating the standard liquid side pressure drop . 30
11.2.1 General . 30
11.2.2 Single Test . 30
11.2.3 Duplicate Tests . 30
11.3 Nominal air flow . 31
11.4 Nominal fan power . 31
12 Test report . 31
Annex A (informative) Bubble point temperature . 32
A.1 Diagram bubble point temperature . 32
Annex B (normative) Test installation for direct expansion operation . 33
Annex C (normative) Test installation for liquids . 35
Annex D (informative) Superheating and capacity . 36
Annex E (normative) Test arrangement . 37
Annex F (normative) Operation with liquid overfeed by pump circulation . 38
F.1 Scope . 38
F.2 Standard conditions . 38
F.3 Measurements . 39
F.4 Testing methods and equipment . 39
F.5 Test procedures . 40
F.6 Capacity calculations . 41
F.7 Conversion to standard conditions . 42
Annex G (informative) Procedure to measure the oil content . 45
Bibliography . 46

Foreword
This document (EN 328:2014) has been prepared by Technical Committee CEN/TC 110 “Heat exchangers”,
the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by February 2015, and conflicting national standards shall be withdrawn
at the latest by February 2015.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 328:1999 and EN 328:1999/A1:2002.
The main changes with respect to the previous edition are listed below:
a) Clause 3 “Terms and definitions” is modified;
b) The revised standard takes into account the application of CO .
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Introduction
This European Standard is one of a series of European Standards dedicated to heat exchangers.
1 Scope
This European Standard is applicable to non-ducted unit air coolers for refrigeration operating:
a) with direct dry expansion of a refrigerant;
b) with liquid overfeed by pump circulation of a refrigerant;
c) with a liquid.
This standard specifies uniform methods of performance assessment to test and ascertain the following:
— product identification;
— standard capacity;
— standard liquid pressure drop;
— standard refrigerant pressure drop (for operation with liquid overfeed by pump circulation only);
— nominal air flow rate;
— nominal fan power.
It does not cover evaluation of conformity.
It is not applicable to air coolers for duct mounting or with natural air convection.
This standard does not cover technical safety aspects.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories (ISO/IEC
17025)
EN 60034-1, Rotating electrical machines - Part 1: Rating and performance (IEC 60034-1)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply:
3.1
physical definitions
3.1.1
forced convection unit air cooler
refrigeration system component transferring heat from air to a refrigerant or liquid. The air is mechanically
circulated over the heat transfer surface by integral fan(s) and fan drive(s)
Note 1 to entry: The heat transfer coil includes refrigerant distributing and collecting headers.
Note 2 to entry: In the following “forced convection unit air cooler” is referred to as “unit cooler”.
3.1.2
heat transfer surface (air side)
external surface of the cooling coil which is in contact with the air flow passing the cooling coil
3.1.3
internal volume
volume of the refrigerant containing parts of the unit cooler between its two connections
3.1.4
fouling resistance
thermal resistance of a layer of unwanted deposit on the heat exchanger surface reducing its heat transfer
performance
Note 1 to entry: The fouling resistance for a clean surface is zero. Clean, in this context, means that all production
residues have been removed from the heat transfer surface and the fan(s) by the factory's cleaning process.
3.2
refrigerant
working fluid in a cooling system, which absorbs heat at low pressure / temperature by evaporation and
rejects heat at a higher pressure / temperature by condensation
3.3
liquid
working fluid remaining liquid during the absorption of heat
3.4
capacities
3.4.1
sensible air cooling capacity
heat flow rejected by the air resulting from a dry bulb temperature drop
3.4.2
latent cooling capacity
heat flow rejected by the air resulting from condensation of water vapour or frost formation including
subcooling on the unit cooler surface
3.4.3
total cooling capacity
sum of the sensible and the latent capacities measured at the same time
3.4.4
gross cooling capacity
total heat flow absorbed by the refrigerant or liquid
3.4.5
net cooling capacity
cooling capacity available for cooling the air equal to the gross cooling capacity minus the fan power
3.4.6
standard capacity
gross cooling capacity at standard conditions and normal atmospheric pressure of 1013,25 hPa of a unit
cooler with clean internal and external surfaces
3.4.7
fan power
electric power, absorbed by the fan motors at the electrical terminals of the motor(s)
3.4.8
nominal fan power
fan power measured during the air flow test and corrected to the normal atmospheric pressure of 1013,25 hPa
Note 1 to entry: The fan power will also differ with the temperature at which the fan runs. As the fan power is only a
small proportion of the total cooling load, the deviations are considered to be negligible.
3.5
rotational speed of the fans
average rotational speeds of fans
3.6
pressures and pressure differences
for the purposes of this standard all pressures are average values ascertained over the test duration
3.6.1
evaporating pressure
absolute pressure of the refrigerant, at the outlet connection of the unit cooler
3.6.2
liquid inlet pressure
static pressure of the liquid at the inlet connection of the unit cooler
3.6.3
liquid outlet pressure
static pressure of the liquid at the outlet connection of the unit cooler
3.6.4
liquid pressure difference
difference between the liquid inlet pressure and the liquid outlet pressure
3.6.5
refrigerant inlet pressure
absolute pressure of the refrigerant, at the inlet connection of the unit cooler (see Annex F)
3.6.6
critical pressure
pressure at the critical point where the liquid and gaseous phases of the refrigerant have the same physical
properties
3.7
temperatures
for the purposes of this standard all temperatures are average values ascertained over the test duration
3.7.1
air temperatures
3.7.1.1
air inlet temperature
average dry bulb temperature of the air at the unit cooler inlet, taking into consideration the local air velocities
3.7.1.2
air dew point temperature
dew point temperature of the air within the calorimeter room
3.7.1.3
inside temperature
air temperature inside the calorimeter room responsible for the heat exchange with the ambient
3.7.1.4
ambient temperature
temperature around the calorimeter room responsible for the heat exchange with the inside
3.7.2
refrigerant temperatures
3.7.2.1
evaporating temperature
dew point temperature of the refrigerant, corresponding to the evaporating pressure
3.7.2.2
superheating temperature
temperature of the refrigerant vapour at the outlet connection of the unit cooler, measured on the wall of the
tube at the location recommended by the manufacturer for fixing the expansion valve sensing element or
downstream of the liquid-suction heat exchanger where this is an integral part of the unit cooler
3.7.2.3
subcooled refrigerant temperature
temperature of the liquid refrigerant at the inlet connection to the expansion device (not necessarily part of the
unit cooler)
3.7.2.4
bubble point temperature for cooler measurement
temperature calculated from the enthalpy based on the temperature and pressure at the inlet of the expansion
valve
3.7.3
liquid temperatures
3.7.3.1
liquid inlet temperature
average temperature of the liquid at the inlet connection of the unit cooler taking into consideration the local
liquid velocities
3.7.3.2
liquid outlet temperature
average temperature of the liquid at the outlet connection of the unit cooler taking into consideration the local
liquid velocities
3.7.4
water temperatures
(applicable only where the balancing heat is supplied by water)
3.7.4.1
water inlet temperature
temperature of the water as it enters the calorimeter
3.7.4.2
water outlet temperature
temperature of the water as it leaves the calorimeter
3.7.5
vapour outlet temperature
temperature of the refrigerant vapour at the vapour outlet connection of the separator
3.8
temperature differences
3.8.1
temperature differences for refrigerants
3.8.1.1
inlet temperature difference
difference between the air inlet temperature and the evaporating temperature
3.8.1.2
superheating
difference between the superheating temperature and the evaporating temperature
3.8.1.3
degree of superheating
ratio of the superheating to the inlet temperature difference
3.8.1.4
subcooling
difference between the bubble point temperature corresponding to the absolute pressure of the refrigerant at
the inlet connection to the expansion device and the subcooled refrigerant temperature
3.8.2
temperature differences for liquids
3.8.2.1
inlet temperature difference
difference between the air inlet temperature and the liquid inlet temperature
3.8.2.2
liquid temperature difference
difference between the liquid inlet and outlet temperatures
3.9
high glide
refrigerant where the difference between the condensing and bubble point temperatures at a condensing
temperature of 40 °C is greater than 3K
3.10
operation with refrigerants
3.10.1
direct expansion operation
evaporation process in which the refrigerant enters the unit cooler via a direct expansion device as a liquid-
vapour mixture and leaves it in superheated state (see system boundaries in Annex A)
3.10.2
operation with liquid overfeed by pump circulation
evaporation process in which the refrigerant leaves the unit cooler in partially evaporated state, the process
being operated by a mechanical liquid pump and a separator being parts of a refrigerating machine
Note 1 to entry: The refrigerant is transported from the separator to the unit cooler by the mechanical pump (see
Annex F).
3.10.3
supercritical operation
thermodynamic cycle in which the outlet pressure at the compressor is higher than the critical pressure of the
refrigerant with a gas cooler being part of the refrigerator
3.11
refrigerant enthalpies
3.11.1
refrigerant inlet specific enthalpy
specific enthalpy of the refrigerant at the inlet connection of the unit cooler system. For capacity calculation it
is defined as the specific enthalpy of the saturated liquid refrigerant at the inlet to the expansion device
corresponding to the subcooled refrigerant temperature and for transcritical operation it is defined as the
enthalpy corresponding to temperature and pressure
Note 1 to entry: For liquid overfeed by pump circulation the refrigerant inlet enthalpy cannot be defined by temperature
and pressure measurement at the unit cooler's connections (see Annex E).
3.11.2
refrigerant outlet specific enthalpy
specific enthalpy of the refrigerant at the outlet connection of the unit cooler system. For capacity calculation it
is defined as the specific enthalpy of the refrigerant corresponding to the evaporating pressure and the
superheating temperature
Note 1 to entry: For liquid overfeed by pump circulation the refrigerant outlet enthalpy cannot be defined by
temperature and pressure measurement at the unit cooler's connections (see Annex E).
3.11.3
specific vaporization enthalpy
enthalpy at the evaporating pressure without regard to the pressure drop across the unit cooler (see Annex F)
3.12
nominal air flow
air volume flow rate flowing through the unit cooler, when its air side is dry and clean
3.13
oil content
proportion of oil by mass in the refrigerant related to the pure refrigerant
3.14
refrigerant recirculation rate
ratio between the actual mass flow rate through the unit cooler and the mass flow rate necessary for the total
evaporation of the refrigerant (see Annex F)
4 Symbols
For the purposes of this document, Table 1 applies:
Table 1 — Symbols
E kJ
electrical energy input into the calorimeter
el
F correction factor for the deviation from standard atmospheric pressure Pa
h liquid inlet specific enthalpy kJ/kg
L1
h liquid outlet specific enthalpy kJ/kg
L2
h refrigerant inlet specific enthalpy kJ/kg
R1
h refrigerant outlet specific enthalpy kJ/kg
R2
h refrigerant specific enthalpy at the outlet connection of the unit cooler (see Annex E) kJ/kg
R3
h water inlet specific enthalpy (balancing air heater) kJ/kg
W1
h water outlet specific enthalpy (balancing air heater) kJ/kg
W2
HL heat flow from the calorimeter inside to its ambient kW
n rotational speed of fans 1/min
p atmospheric pressure Pa
atm
p bar
evaporating pressure
e
p refrigerant pressure at the inlet connection of the unit cooler (see Annex E) bar
e1
p bar
refrigerant pressure at the vapour outlet connection of the separator (see Annex E)
e2
p
liquid pressure at unit cooler inlet bar
L1
p
liquid pressure at unit cooler outlet bar
L2
p
refrigerant pressure at expansion device inlet bar
R1
P capacity (primary method) kW
P capacity (confirming method) kW
P measured capacity kW
M
q kg/s
mass flow rate
m
q refrigerant mass flow rate on the low pressure side through the pump kg/s
mRPu
q volume flow rate m /s
V
rd relative deviation -
ρ density kg/m3
r r recirculation rate -
t temperature of liquid at the flow measuring point °C
LM
t temperature of refrigerant at the flow measuring point (liquid line) °C
RM
t temperature of water at the flow measuring point (balancing air heater) °C
WM
t air inlet temperature (dry bulb) °C
A1
t temperature of refrigerant at boiling curve °C
bp
t air dew point temperature within the calorimeter room °C
dp
t evaporating temperature °C
e
t individual air temperature inside the calorimeter °C
i
t saturation temperature corresponding to p °C
(pR1) R1
t liquid inlet temperature °C
L1
t liquid outlet temperature °C
L2
t refrigerant temperature at the inlet to the expansion device °C
R1
t vapour outlet temperature at the vapour outlet connection of the separator (see Annex E) °C
R2
t actual temperature at unit cooler outlet connection (see Annex E) °C
R3
t water inlet temperature °C
W1
t water outlet temperature °C
W2
t superheating temperature °C
sup
Δp pressure drop bar
Dt K
inlet temperature difference
Δh refrigerant specific enthalpy change in the unit cooler at p (see Annex E) kJ/kg
e e
Δh specific vaporization enthalpy at p (see Annex E) kJ/kg
O e
Δh difference between refrigerant outlet and inlet specific enthalpies kJ/kg
R
Δt subcooling = t - t K
(pR1)
sub R1
Δt superheating K
sup
Δt temperature difference between liquid inlet and outlet K
L
τ test duration S
U voltage V
Subscripts
m mass;
v
volume;
L liquid;
M
flow meter;
R refrigerant;
W
water.
Numbers indicate positions defined on the circuit diagrams.
Superscripts
(a) (b)
(a / b) refers to the test sequence, above and below the standard conditions.
(st) refers to standard conditions.
5 Standard capacity
5.1 Basis of standard capacity data
The cooling capacity of a given unit cooler, or its overall coefficient of heat transfer depends on the following:
a) the inlet temperature and the humidity content of the entering air;
b) the mass flows of air, refrigerant or liquid;
c) the evaporating temperature or the inlet temperature of the liquid;
d) the degree of refrigerant superheating;
e) further conditions e.g.
— the degree of refrigerant subcooling;
— pressure and temperature at the inlet of the expansion device in supercritical operation;
— oil content;
f) the state of frosting.
Because of the related dependence of the overall coefficient of heat transfer on both the mass flow and the
temperature difference, it is not permissible to specify cooling capacities per unit of temperature difference, as
the coefficient of heat transfer can only be taken as a constant value in a very limited range of operating
conditions.
Therefore cooling capacities are given for specific operating conditions.
The influence of frosting on the unit cooler surfaces (latent cooling capacity) can only be measured with great
difficulty because of the changing processes. Therefore this standard only considers cooling capacities under
non frosting conditions, as these can be measured and tested under steady-state conditions.
5.2 Standard conditions for the cooling capacity
5.2.1 General
The standard capacity shall be based on tests performed on a clean unit cooler at nominal voltage and
frequency under one or more of the conditions specified in 5.2.2 and 5.2.3.
5.2.2 Refrigerants
The standard conditions for refrigerants are given in Table 2 and Table 3:
Table 2 — Standard conditions for refrigerants
Standard t t t Δt / Dt t
A1 dp e sup 1 R1
condition
°C °C °C – °C
SC 1 +10 < −2 0 0,65 30
SC 2 0 < −10 - 8 0,65 30
SC 3 - 18 < - 27 - 25 0,65 20
SC 4 - 25 < - 33 - 31 0,65 20
SC 5 - 34 < - 42 - 40 0,65 20
NOTE It is essential that the oil content be below 1 % of mass.
The standard rating conditions for the operation with R744 (CO ) is given in Table 3:
Table 3 — Standard conditions for operation with R744 (CO )
Standard t t t Δt / Dt t
A1 dp e sup 1 bp
Condition
°C °C °C °C
SC 1 +10 < −2 0 0,65 20
SC 2 0 < −10 - 8 0,65 20
SC 3 - 18 < - 27 - 25 0,65 10
SC 4 - 25 < - 33 - 31 0,65 10
SC 5 - 34 < - 42 - 40 0,65 10
The enthalpy of t applies.
bp
For standard conditions for operation with liquid overfeed by pump circulation see Annex E.
5.2.3 Liquids
The standard conditions for liquids are given in Table 4:
Table 4 — Standard conditions for liquids
t
Standard t t t
A1 dp L1
L2
Intended for Comments
condition °C °C °C
°C
The flow
SC 10 + 16 < + 2 + 4 + 8 Water direction shall
be given
SC 11 0 < - 12 - 10 - 7 Specified liquid
NOTE The quality of the liquid needs to be such that it does not cause measurable fouling
during the entire operation for establishing the test.
5.3 Conditions for the nominal air flow rate
The nominal air volume flow rate shall be referred to an air temperature of + 20°C.
NOTE The air volume flow rate is not influenced by atmospheric pressure and air temperature when the fan speed is
constant.
5.4 Conditions for nominal fan power
The nominal fan power shall be referred to an air temperature of + 20°C and to an atmospheric pressure of
1013,25 hPa.
6 Manufacturer's data
To identify the unit cooler and allow traceability, the manufacturer or supplier shall supply the test house with
the following minimum information for each unit cooler to be tested:
a) model designation of unit;
b) model designation of fan;
c) rating of the fan motor(s) according to EN 60034-1;
d) standard capacity for the standard conditions in the range of application, stating the refrigerants used;
e) nominal air flow;
f) nominal fan power;
g) nominal voltage and frequency;
h) total heat transfer surface (air side);
i) fin pitch and thickness;
j) tube nominal bore;
k) tube geometry;
l) circuiting arrangement;
m) internal volume including distributors and headers;
n) installation instructions;
o) maximum permissible operating pressure PS.
7 Measurements
7.1 Uncertainty of measurements
The permissible uncertainty of significant measurements is given in Table 5.
Table 5 — Uncertainty of measurements
Measured quantity Unit Uncertainty of measurement
Air
— inlet temperature °C ±0,2 K
— dew point temperature °C ±2 K
— all other temperatures °C ±0,5 K
Refrigerant °C ±0,2 K
— temperature
— pressure kPa shall ensure that the evaporating temperature to be
a
obtained within ± 0,2 K
— volume flow rate kg/s
±0,2 %
m /s
Liquid
— temperature °C ±0,2 K
— temperature difference. K ±0,1 K
— pressure drop kPa ±5 % or
1 kPa (larger value applies)
— liquid refrigerant volume flow m /s ±1 %
a
rate
Electrical quantities (fans)
— electrical power input W ±1 % or at least 1 W
— current A ±0,5 %
— voltage V ±0,5 %
— frequency Hz ±0,5 %
Oil content in the refrigerant kg ±20 % of the measured value
Atmospheric pressure hPa ±5 hPa
−1
Fan speed min ±1 %
a
also mass flow rate with equivalent uncertainty can be used.
7.2 Measurement criteria
7.2.1 Pipe side temperature measurement
One of two methods of measurement shall be used as follows:
a) Method A
When the temperature is measured on the outside of the connecting pipe it shall be measured at two opposite
points of the same cross-section and, if the pipe is horizontal, there shall be one point above and one below.
The pipe shall be insulated on each side of the temperature measuring point for a length of at least 10 times of
its outside diameter. It shall be ensured, that good thermal contact exists between the sensor and the pipe at
the measuring point.
The measured value is the arithmetic mean of both individual values.
b) Method B
When the temperature is measured by a sensor immersed in the pipe, care shall be taken that temperature
stratifications and flow patterns do not influence the accuracy of the measurements.
7.2.2 Superheating temperature
The superheating temperature shall be measured as near as possible to the outlet connection provided by the
manufacturer.
This location shall be within a distance of 500 mm from the unit cooler outlet connection and within the
calorimeter room.
Where a liquid to suction heat exchanger is an integral part of the unit cooler the measuring point for the
superheating temperature shall be at the outlet connection of the heat exchanger.
Method A shall be used.
7.2.3 Temperature at expansion device inlet
The subcooled liquid refrigerant temperature shall be measured as near as possible to the expansion device
inlet.
NOTE At low evaporating temperatures and small capacities the temperature measurement can be influenced by
conductivity.
Where a liquid to suction heat exchanger is an integral part of the unit cooler the measuring point for the
subcooled liquid refrigerant temperature shall be at the inlet connection of the expansion device.
Both methods A or B may be used. When method B is applied, care shall be taken that the sensor does not
cause the generation of flash gas.
7.2.4 Liquid temperatures
The liquid temperatures shall be measured as near as possible to the connections, provided by the
manufacturer.
Method A or B may be used.
7.2.5 Water temperatures (balancing air heater)
Water temperatures shall be measured as the water enters or leaves the calorimeter. Method B is preferred.
7.2.6 Air temperature measurement
7.2.6.1 Air inlet temperatures
The air inlet dry bulb temperatures shall be measured in the centre of equal sections of the face area of the
coil. These sections shall not be larger than 0,2 m and be square if possible. There shall be at least 6
sections. Temperature sensing elements shall be shielded against radiation and any other form of heat
transfer affecting the accuracy of the measurement.
The dew point shall be measured at one point within the calorimeter room.
7.2.6.2 Inside and ambient air temperatures
Inside and ambient air temperatures shall be measured 0,15 m perpendicular to the surface of the calorimeter.
Only dry bulb temperatures are significant.
If the calorimeter is in direct contact with the floor, the temperature shall be measured on the outer surface of
the insulation.
NOTE The quantity and location of temperature measuring points will be dependent on the calorimeter design and
the variation in inside and ambient temperatures.
There shall be at least one inside and ambient temperature measuring point on each of the six surrounding
surfaces.
7.2.7 Pressure measuring points
The pressure measuring points shall be located in the middle of a straight part of pipe of constant diameter,
equal to that of the cooler connections, having a length of not less than 10 times its diameter ensuring that
there is no restriction involved. They shall be positioned between the temperature measuring points and the
connections of the unit cooler.
7.2.8 Flow rates
7.2.8.1 General
The flow rates of refrigerants, liquids and water shall be measured according to the recommendations of the
installation instructions for the flow measuring devices.
7.2.8.2 Refrigerant flow rate
When measuring the refrigerant flow rate, the refrigerant shall be sufficiently subcooled to prevent the
generation of flashgas which causes inaccurate measurements. In order to check that there is no flashgas, a
sight glass shall be placed immediately after the flow measuring section.
NOTE 1 When measuring refrigerant flow rate, it is practical to locate the measuring device on the liquid side of the
circuit, and for transcritical operation between gas cooler and expansion device.
NOTE 2 Refrigerant flow rates usually fluctuate over any length of time. Therefore to measure these, integrating
devices are more suitable than momentary indicators.
7.2.8.3 Liquid and water flow rate
NOTE As with refrigerants, integrating devices are more suitable than momentary indicators.
7.2.9 Oil content
The oil content shall be measured unless it can be guaranteed that is below 1 % by mass.
For a recommended measurement procedure see Annex F (informative).
7.2.10 Non azeotropic refrigerant
For high-glide refrigerants the refrigerant mixture shall be measured unless it can be guaranteed that the
mass fraction varies by less than ± 2 % from the manufacturer's data.
8 Testing methods and equipment
8.1 Testing methods
8.1.1 Capacity
8.1.1.1 General
In order to fulfil the requirements of this standard, two methods of determining the cooling capacity shall be
used simultaneously. The primary method shall determine the capacity on the air side. The confirming method
shall determine the capacity on the refrigerant / liquid side. The result of the confirming method shall agree
with that of the primary method within ± 4 %.The testing methods and arrangements are shown in Annexes B
to E. If the deviation between the two methods is greater than ± 4 %, it can be assumed that there is an error
either in the testing arrangement or in the execution of the tests.
These test methods are not suitable for high glide refrigerants used with liquid feed by gravity or
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