Page 299 - Defrosting for Air Source Heat Pump

Defrosting control strategy 293

Fig. 9.36 Measured temperatures of the tube surface at the entrance and exit of the outdoor coil
during defrosting.

Fig. 9.37 Total energy coming from outside the system during defrosting.

° ° ° ° °
periods are 3.6 C for P 1 , 6.1 C for P 2 , 6.6 C for P 3 , 4.7 C for P 4 , and 4.0 C for P 5 ,
respectively. Clearly, at P 3 , from 172 to 189 s, the temperature difference is the big-
gest. In fact, this period lasts about 17 s, which is not the longest one in the five
periods. Therefore, it is demonstrated that the best defrosting termination is at
this period.