Page 204 - Defrosting for Air Source Heat Pump

198 Defrosting for Air Source Heat Pump

circuits for the tube surface and fin center at the same time point are T Circuit 1 >
T Circuit 2 > T Circuit 3, from 80 s into the defrosting operation to termination, as shown
in Figs. 3.13 and 3.16. In this section, the same parameters in the two cases were mea-
sured and presented in Figs. 7.4–7.7, but with water-collecting trays installed between
circuits. In all these figures, for their time (horizontal) axis, 80 s is the chosen starting

28
Circuit 1 Circuit 2 Circuit 3
24
T > T > T 1
3
2
20
Tube surface temperature ( o C) 16 8 o
12

(T – T) = 2.8 C
2
1 max
4
125 s 185 s
0
80 100 120 140 160 180 200
Time (s)
Fig. 7.4 Measured tube surface temperatures at the exits of the three refrigerant circuits during
defrosting in Case 1.
28
Circuit 1 Circuit 2 Circuit 3
24 T > T > T 1

20
Tube surface temperature ( o C) 16 8 (T – T ) = 7.5 C
3
2

12
o
2
1 max

4
125 s 172 s 185 s
0
80 100 120 140 160 180 200
Time (s)
Fig. 7.5 Measured tube surface temperatures at the exits of the three refrigerant circuits during
defrosting in Case 2.