Full Description

A multiple-source heat pump for heating in cold climates has been investigated. The heat pump had four modes of operation: two solar-source modes, and ambient-air-source mode, and a storage-source mode. Solar collectors cooled by Refrigerant 12 served as the evaporator for the heat pump. The solar energy collected was used to heat space air or water storage if heating was not required. During periods of low solar radiation and at night, ambient air was circulated through the collectors, which served as the evaporator to extract heat from the ambient air.

A tempering heat exchanger was used in series with the storage evaporator to enable the heat pump to extract heat. Under stable operating conditions when the storage water was heated to a high temperature.

The solar-source mode operated with minimum collector efficiencies of 0.5 at ambient temperatures as low as -10F (â23C). The air-source mode operated with a minimum output of 85 Btuh/ft (268 Watts/m) of net frontal collector area at an ambient temperature of 0F (â18C). The water storage was heated to 125F (52C) and cooled to 42F (5C).

It was noted that at low refrigerant flow rates even when the time-averaged temperature of the refrigerant at the location controlled by the expansion valve was higher than the saturation temperature, the refrigerant at this location was actually wet. This possible condition should be taken into account in calculating from experimental data the energy absorbed by collectors.

Citation: ASHRAE Transactions, 1983, vol. 89, pt. 2A, Washington, D.C.

Product Details

Published: 1983 Number of Pages: 16File Size: 1 file , 1.1 MB Product Code(s): D-DC-2797