Effect of reduced evaporator airflow on the high temperature performance of air conditioners

Two residential sized air conditioners were tested in psychrometric rooms at reduced evaporator airflows ranging from 0 to 50% below that recommended by the manufacture of each of the units. Outdoor temperatures ranged from 35 to 49°C. One of the units used a thermal expansion valve for flow control while the other unit used a short tube orifice. Performance of the units was quantified by the capacity, power, coefficient of performance, and sensible heat ratio. Results at 35°C indicated that the reduction in air produced a larger drop in capacity and coefficient of performance for the orifice controlled unit than the thermal expansion valve controlled unit. The power showed less than a 4% reduction for either unit as the airflow was reduced by 50%.