Page 137 - Defrosting for Air Source Heat Pump

130 Defrosting for Air Source Heat Pump

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

T > T ; T > T
1
12
1
1
1
2
o
8.1 C
4
173 s
135 s 188 s
0 40 s 141 s
60 80 100 120 140 160 180 200
Time (s)
Fig. 5.12 Measured fin surface temperatures at the center of the three refrigerant circuits during
defrosting in Case 2.

28
Fin in Circuit 1
Fin in Circuit 2
24
Fin in Circuit 3 o
4 C 13 s
20
Fin surface temperature ( o C) 16 8 T = T = T 3 T > T > T 2 T = T > T 2
Stage 3:
Stage 1:
Stage 2:
Positive effect
Negative effect
No effect
12
1
3
3
1
2
1
o
1.2 C
4
114 s 207 s
123 s 145 s 205 s
0 40 s
80 100 120 140 160 180 200 220
Time (s)
Fig. 5.13 Measured fin surface temperatures at the center of the three refrigerant circuits during
defrosting in Case 3.
between the three tube surface temperatures was small, with the biggest difference of
1.87°C at 110 s. It is very obvious that the temperature curves steeply increased from
100 s to 130 s, which met Fig. 5.7 well. From 145 s to the end of defrosting, the rela-
tionship of tube surface temperatures kept at T 1 ¼ T 2 ¼ T 3 . All the temperature curves