Page 135 - Defrosting for Air Source Heat Pump

128 Defrosting for Air Source Heat Pump

28
Circuit 1 Circuit 2 Circuit 3
24
o
4 C
Tube surface temperature ( o C) 16 8 T > T > T 3 15 s 173 s
20

1
2
12

T – T > T – T
3
1
2
2
4
182 s
186 s
0
80 100 120 140 160 180 200 220
Time (s)
Fig. 5.8 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
o
4 C 14 s
Tube surface temperature ( o C) 16 8 9.6 C T > T > T 1 T = T = T 3
20

12
2
2
3
1
o
o
40 s
0 4 106 s 1.87 C 145 s 172 s 186 s
60 80 100 120 140 160 180 200
Time (s)

Fig. 5.9 Measured tube surface temperatures at the exits of the three refrigerant circuits during
defrosting in Case 2.

gravity, from 80 s to 186 s, the relationship of tube surface temperatures kept at
T 1 > T 2 > T 3 clearly. In addition, from 110 s to 150 s, the order of the curves was
T 1 T 2 > T 2 T 3 because the mass of the melted frost flowing into Circuit 3 was
much more than that into Circuit 2. In this section, this case was mainly used to be
compared with Case 2.