Page 101 - Defrosting for Air Source Heat Pump

Modeling study on uneven defrosting 93

5.0
4.5 Circuit 1
4.0 Circuit 2
Circuit 3
3.5
The mass of melted frost (g) 2.5
3.0

2.0
1.5
1.0
0.5
85 s 145 s
0.0
155 s
–0.5
0 20 40 60 80 100 120 140 160 180 200 220 240
Defrosting time (s)

Fig. 4.16 The mass of melted frost during defrosting.

5500
5000 Circuit 1
Circuit 2
4500 Circuit 3
Energy used from refrigerant (J) 3000
4000
3500

2500
2000
1500
1000
500
0 Water flowing Water vaporizing
Forst melting 85 s 145 s
–500
0 20 40 60 80 100 120 140 160 180 200 220 240
Defrosting time (s)

Fig. 4.17 Energy used from the refrigerant at each 5 s.

Figs. 4.16 and 4.17 show the mass of the melted frost during defrosting and the
energy used from the refrigerant at each 5 s, respectively. The two figures also show
the changing at different stages, with the time points at 85 and 145 s into defrosting.
This is just at the second and third stages in the model. As shown in Fig. 4.16, the frost
is mainly melted from 85 to 145 s, and the difference between the three circuits is
clear. The peak values for Circuits 1–3 are 4.3, 4.0, and 3.7 g, respectively.