Page 202 - Defrosting for Air Source Heat Pump

196 Defrosting for Air Source Heat Pump

40
Circuit 1 Circuit 2 Circuit 3
36
Tube surface temperature ( o C) 28 T T T 3
32

24
20
2
1
16
12
T > T > T
8 1 3 2
15 s 110 s
4
0 20 40 60 80 100 120
Time (s)

Fig. 7.1 Measured tube surface temperatures at the exits of the three refrigerant circuits on
defrosting mode without any frost accumulated in Case 1.

44
Circuit 1 Circuti 2 Circuit 3
40

36
Tube surface temperature ( o C) 28 T > T > T 1 T = T = T 3
32

2
1
2
3
24
20
16
10 s 40 s 115 s
12
8
0 20 40 60 80 100 120
Time (s)
Fig. 7.2 Measured tube surface temperatures at the exits of the three refrigerant circuits on
defrosting mode without any frost accumulated in Case 2.

shown that the temperatures were observed at T Circuit1 > T Circuit3 > T Circuit2 from 15 to
110 s defrosting operation point. However, in Case 2, as shown in Fig. 7.2, the tem-
peratures of the three circuits were nearly the same from 40 to 110 s. Only during the
first 40 s were the three temperature curves not coincident while the system was