Page 117 - Defrosting for Air Source Heat Pump

Modeling study on uneven defrosting 109

90
Compressor Supply fan Indoor air
80
73.2 kJ
68.6 kJ
70 56.5 kJ
Heat supply for defrosting (kJ) 50 86.3% 86.3% 33.8 kJ 92.2%
60

40
30

20
1.0% 86.6%
10
1.0% 1.0% 1.1%
12.7% 12.5% 6.7%
0 12.4%
Experimental study Study Case 1 Study Case 2 Study Case 3
Fig. 4.29 Heat supply for defrosting after 172 s into defrosting in the previous experimental
study and the three study cases.

450
Frost melting Vaporizing
400
363.2 kJ
357.7 kJ 361.1 kJ
350 34.2 kJ 28.8 kJ 334.5 kJ 5.5 kJ 32.2 kJ
Energy use for defrosting (kJ) 250 329.0 kJ 329.0 kJ 329.0 kJ 329.0 kJ
300

200
150
100

50
0
Experimental study Study Case 1 Study Case 2 Study Case 3
Fig. 4.30 Energy consumption during defrosting in the previous experimental study and the
three study cases.

and 728.0 kJ for Case 3, respectively. Compared with the experimental value of
732.6 kJ, the defrosting energy uses in the three study cases were all less, with that
defrosting energy use in Study Case 2 being the lowest at about 94.6% of the exper-
imental value. It is noted that in Study Case 3, the compressor speed was reduced by