Page 166 - Defrosting for Air Source Heat Pump

160 Defrosting for Air Source Heat Pump

4
Circuit 1 Circuit 2 Circuit 3
0
Tube surface temperature ( o C) –12
–4

–8

–16

–20

0 500 1000 1500 2000 2500 3000 3500 4000
Time (s)

Fig. 6.6 Measured tube surface temperatures during frosting in Case 1.

4
Circuit 1 Circuit 2 Circuit 3
0
Tube surface temperature ( o C) –12
–4

–8

–16

–20
0 500 1000 1500 2000 2500 3000 3500 4000
Time (s)

Fig. 6.7 Measured tube surface temperatures during frosting in Case 2.

temperatures at the exit of the outdoor coil, and the average fin surface temperatures at
the center of the three circuits in the two cases, respectively. Finally, the variation of
the calculated COP of the ASHP unit during frosting in the two cases is shown in
Fig. 6.13.
As shown in Fig. 6.6, the measured tube surface temperature of Circuit 1 and Cir-
cuit 2 was kept the same in Case 1. This is the reason why the frost that accumulated on