Page 243 - Defrosting for Air Source Heat Pump

238 Defrosting for Air Source Heat Pump

900
Heating ambient air
Heating melted frost
800
Heating outdoor coil metal
700 Vaporizing retained water
Melting frost 44.97%
Energy consumptions (kJ) 500 52.04% 1.17%
600

400
6.68%
5.13%
1.33%
300
5.71%
200 3.59%
43.21%
38.67%
100
0
C e s a 1 C e s a 2
Fig. 8.13 Heat consumptions during defrosting in two cases.

Table 8.4 System operation differences in the two experimental cases
Item Parameters Case 1 Case 2
1 Circuit number of outdoor coil 3 (Circuit 1–3) 3 (Circuit 1–3)
working during frosting
2 Circuit number of outdoor coil 2 (Circuit 1–2) 3 (Circuit 1–3)
working during defrosting
3 Circuit number of indoor coil 3 (Circuit 1–3) 3 (Circuit 1–3)
working during frosting
4 Circuit number of indoor coil 3 (Circuit 1–3) 3 (Circuit 1–3)
working during defrosting
5 Number of water-collecting trays 1 (Tray B) 1 (Tray C)
installed during frosting
6 Number of water-collecting trays 1 (Tray B) 1 (Tray C)
installed during defrosting
7 Total metal mass of indoor coil 2496 g 2496 g
8 Total metal mass of outdoor coil 2020 g 3030 g
9 The lowest circuit detecting the Circuit 2 Circuit 3
defrosting termination temperature
10 Results shown in Figs. 8.5–8.14; Figs. 8.5–8.14;
Tables 8.5 and 8.6 Tables 8.5 and 8.6

3.0 kJ, at 0–80 s in Case 1 and 0–120 s in Case 2. It is demonstrated that at the start of
defrosting, little energy for defrosting came from the energy input, and most of the
energy came from the indoor air thermal energy, or the MES. This also met the
increase of air temperature differences between the inlet and outlet of the indoor coil,
as shown in Fig. 8.8.