Page 150 - Defrosting for Air Source Heat Pump

Investigation of effect on uneven defrosting performance 143

The measured operating performances of the experimental ASHP unit during
defrosting, corresponding to the two experimental cases, are presented in
Figs. 5.20–5.23. In all these figures, for their time (horizontal) axis, 60 s is the chosen
starting time in order to clearly show the temperature rise during defrosting. Figs. 5.20
and 5.21 present the measured tube surface temperatures at the exits of the three refrig-
erant circuits during defrosting. Figs. 5.22 and 5.23 show the measured fin

28
Circuit 1 Circuit 2 Circuit 3
24
o
4 C 14 s
Tube surface temperature ( o C) 16 8 o T > T > T 1 T = T = T 1
20

2
3
12
3
2

0 4 6.5 C 103 s 30 s 145 s 172 s 186 s

60 80 100 120 140 160 180 200
Time (s)

Fig. 5.20 Measured tube surface temperatures at the exit of refrigerant circuits in Case 1.

28
Circuit 1 Circuit 2 Circuit 3
24
o
4 C 11 s
Tube surface temperature ( o C) 16 8 8.7 C 2 3 T > T > T 3 T = T = T 3
20
T > T ; T > T
3
1
1
2
1
2
12
o
145 s
0 4 105 s 30 s 156 s 167 s

60 80 100 120 140 160 180 200
Time (s)
Fig. 5.21 Measured tube surface temperatures at the exit of refrigerant circuits in Case 2.