Page 191 - Defrosting for Air Source Heat Pump

Frosting evenness coefficient 185

1.8
Case 1 Case 2 Case 3
1.5
Temperature of surrounding air Temperature of melted
frost collected
1.2
Temperature ( o C) 0.9

0.6
157 s
0.3
141 s
0.0
135 s
–0.3
0 30 60 90 120 150 180 210 240
Time (s)
Fig. 6.37 Average value of measured temperature of surrounding air and melted frost collected
in the three cases.

1.8 Case 1 Steeply decrease
Measured refrigerant volumetric flow rate (L/M) 1.2 Steeply increase R Case 3 > R Case 2 > R Case 1 Fluctuate
1.6
Case 2
Case 3
1.4

1.0

0.8
165 s
0.6
170 s
0.4
0.2

0.0
0 Fluctuate 80 120 160 200 175 s 240
40
Time (s)
Fig. 6.38 Measured refrigerant volumetric flow rate during defrosting in the three cases.

three cases is at Case 1 > Case 2 > Case 3. Moreover, as listed in Table 6.5, in Case 2
and 3, the mass of melted frost collected from the surface of Circuit 2 is the biggest
among the three circuits. However, as shown in Figs. 6.28 and 6.29, the temperature of
Circuit 2 is always the highest among the three circuits during defrosting. Therefore, it
is contradictory between the maximum deviations and the FECs, and the mass of