ML-11-006 -- The Impact of Refrigerant Charge, Airflow, and Expansion Devices on the Measured Performance of an Air-Source Heat Pump—Part I PDF

This paper describes extensive tests performed on a 3-ton R-22 split heat pump in heating mode. The tests contain 150 steady-state performance tests, 18 cyclic tests, and 18 defrost tests. During the testing work, the refrigerant charge level was varied from 70% to 130%, relative to the nominal value; the outdoor temperature was altered by three levels at 17°F (–8.3°C), 35°F (1.7°C) and 47°F (8.3°C); indoor airflow rates ranged from 60% to 150% of the rated airflow rate; and the expansion device was switched from a fixed-orifice to a thermal expansion value. Detailed performance data from the extensive steady-state cyclic and defrost testing performed were presented and compared.