Page 63 - Defrosting for Air Source Heat Pump

54 Defrosting for Air Source Heat Pump

Fig. 3.6 Measured tube surface temperature at the exits of refrigerant circuits in Case 1.

Fig. 3.7 Measured fin surface temperatures at the center of refrigerant circuits in Case 1.

frost melting began at 60 s into the defrosting operation, and afterward the tube sur-
face temperatures increased steadily from 0°Cto 24°C. The tube temperatures of the
two circuits reached 24°C at 138 and 152 s, respectively. However, in Fig. 3.7 with
two collecting trays installed in Case 2, the temperatures of the tube surface at the exits
of the two circuits reached 24°C almost at the same time, at 136 s. The time difference
of 14 s for the two circuits to reach 24°C in Case 1 clearly showed that it would take