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ASHRAE STD 28 1996 Edition, June 21, 1996
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Methods of Testing Flow Capacity of Refrigerant Capillary Tubes
Includes all amendments and changes through Reaffirmation Notice , January 23, 2010
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This standard prescribes two test methods, a traditional method and an alternative method, for determining the flow capacity of capillary tubes such as are used for refrigerant metering in refrigeration systems. Both methods use dry nitrogen and provide comparable results, but the alternative method is more convenient if electronic devices are used.

The results obtained by the prescribed procedures are indicative of the refrigerant flow characteristics of the tube but are not intended to represent the actual refrigerant flow characteristics in a refrigerating cycle.

The scope of this standard does not include specifications of tolerances on tube diameters or nitrogen flow capacity; however, acceptable variation in test results is suggested.


This standard provides uniform methods for laboratory testing of the flow capacity of refrigerant capillary tubes.