Development of a direct expansion solar assisted heat pump for hot water supply

Experimental investigations were conducted on the direct expansion solar assisted Heat Pump, (DESAHP). Refrigerant R-22 was expanded in the solar collector which also acted as the evaporator in a conventional vapor compression refrigerating machine. The experiments were conducted under conditions of high and low solar radiation, with evaporator completely shaded from the sun, and at night. System thermal performance was determined by measuring refrigerant flow rate, temperature and pressure at numerous points in the system. The results showed that 227-l of water could be heated from 30degrees to 55degreesC in about 105 minutes. Higher water temperatures were obtained during hot sunny days. The coefficient of performance. of heating, COPN ranged from 11 to 4.7, depending upon operating conditions. The total saving of electric energy during hot sunny days was about 460%. It means that for 1 kWh Of electrical input to the system, we achieve 4.6 kWh. This percentage decreases as the evaporator temperature. decreases and is a function of solar energy input. [GRAPHICS]