Page 189 - Defrosting for Air Source Heat Pump

Frosting evenness coefficient 183

32
Tube in Case 1 Fin in Case 1
28 Tube in Case 2 Fin in Case 2
Tube in Case 3 Fin in Case 3
24
o
5.4 C
20
Temperature ( o C) 16 T > T 9.8 C 163 s
o
182 s
12
186 s

198 s
4 8 t f 188 s
203 s
0
80 100 120 140 160 180 200 220 240
Time (s)
Fig. 6.33 Average measured tube and fin surface temperatures during defrosting in the
three cases.

1.8
Circuit 1 Circuit 2 Circuit 3
1.5

1.2 T > T > T a1
Temperature ( o C) 0.9
a2
a3
0.6
150 s
w3
w2
w2
0.3
138 s T > T ; T > T w1
0.0
50 s 136 s
–0.3
0 30 60 90 120 150 180 210 240
Time (s)
Fig. 6.34 Measured temperatures of surrounding air and measured temperature of the melted
frost collected in the three cylinders during defrosting in Case 1.

respectively. Therefore, the defrosting durations in the three cases are 197 s for Case 1,
187 s for Case 2, and 175 s for Case 3, respectively. Therefore, the experimental
results first demonstrated that the defrosting duration could be shortened by about
22 s, or about 11.2%, when the FEC was increased from 79.4% to 96.6%.