BS/EN 328-2014 pdf download.Heat exchangers Forced convection unit air coolers for refrigeration Test procedures for establishing the performance.
In order to fulfil the requirements of this standard, two methods of determining the cooling capacity shall be used simultaneousIy. The primary method shall determine the capacity on the air side. The confirming method shall determine the capacity on the refrigerant I 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 liquid overfeed by pump circulation. The method in Annex F shall be used as a confirmation method.
8.1.1.2 Primary test method
The following primary test method shall be used to determine the gross cooling capacity on the air side in a calorimeter. The principle of this method is to measure the total heat flow into a calorimeter room in order to balance the cooling capacity of the unit cooler under test. This heat input is equal to the cooling capacity of the unit cooler, taking into consideration the heat flow exchanged between the calorimeter and the ambient as well as the connecting pipes for the unit cooler within the calorimeter.
8.1.1.3 Confirming test method
The following confirming test method shall be used to determine the gross cooling capacity on the refrigerant I liquid cycle side. The principle of this method is to measure the refrigerant I liquid flow rate and to multiply this flow rate by the difference between the specific enthalpies at the outlet and inlet connections of the unit cooler. The specific enthalpy difference of the refrigerant I liquid shall be determined from the temperature and pressure measurements and physical properties of the refrigerant.
8.1.1.4 Air flow method
For the purposes of this standard the air flow method for determining the capacity is considered to be inaccurate and therefore its use is not permitted.
8.12 Airflow
The method used shall be to measure the overall air flow rate at free inlet and discharge conditions.
NOTE Forced convection unit coolers create very turbulent air flows. Therefore measurements of air speeds at individual points cannot be used.
8.1.3 Heat exchange with the ambient
The heat exchange with the ambient is measured via the electric heat inducement into the calorimeter room.
8.2 Equipment
c) all distances correspond to the minimum requirements of the installation instructions provided by the manufacturer, particularly the distance of the air inlet from the back wall and the ceiling;
d) the volume in m3 of the compartment, housing the unit cooler under test, shall be between 1/30 and 1/600 of the air flow rate in m3Th produced by the unit cooler under test together with all auxiliary air moving devices.
Where A and B are the air inlet dimensions of the unit cooler.
The total heat content of the calorimeter shall be chosen such that it does not vary by more than ± 0,5 % of
the capacity measured during the test duration.
8.2.1.3 Ambient arrangement
All equipment in the refrigerant cycle, except for the measuring points at the unit cooler and the expansion device shall be placed outside the calorimeter room.
The calorimeter room shall be designed and arranged in its ambient such, that verification of the heat exchange with the ambient according to the requirements of this standard is possible.
The calorimeter room shall be located in an ambient the average temperature of which can be held constant. There shall be no significant heat radiation to the test room. The clearance between the caloiimeter room and the walls of the enclosing space shall be sufficient to allow the reproducible measurement of the ambient temperature.
Ambient conditions of the calorimeter room shall be such that the same air conditions, particularly air movements, prevail during the calibration test as during the capacity test.BS/EN 328-2014 pdf download.