Page 317 - Defrosting for Air Source Heat Pump

312 Defrosting for Air Source Heat Pump

Table 10.7 Calculation data and experimental results of the four defrosting cases
Item Parameters Case D3 Case D4

1 Calculated FEC 75.7% 96.6%
2 Defrosting duration 215 s 185 s
3 Total power inputs to compressor and indoor air fan 133.0 kJ 107.6 kJ
4 Energy from indoor air 727.7 kJ 541.2 kJ
5 Condition shown in Fig. 10.2 (A) (B)

inputs to the compressor and indoor air fan, and the thermal energy from the indoor air
were calculated and listed in Table 10.7. All these data would be used in the later eco-
nomic analysis process.
(4) Cooling assumptions
In order to calculate the running cost of an ASHP unit in the cooling season, the fol-
lowing assumptions were also given:
i. Duration of cooling season was assumed at 120 days in a year.
ii. Duration of cooling operation was assumed at 12 h in a day.
iii. The system COP was assumed at the rated value, as listed in Table 10.1.
iv. The capacity of the ASHP unit was assumed as the rated cooling value, as listed in
Table 10.1.
Based on the total 30 given assumptions in four types, the technoeconomic analysis
was conducted with the following equations.

10.2.1.3 Economic analysis equations
(1) First cost
The first costs of the six valves and their installation costs were C f, V and C i, V , respec-
tively. The total first cost of the new ASHP unit, C f, i , covered the cost of an ASHP
unit, C ASHP , and the additional first cost of valves. The total first costs in the two typ-
ical cases could be calculated by,

C f,i ¼ C f,V,i + C i,V,i + C ASHP i ¼ D3and D4ð Þ (10.1)
(10.2)
C f,D3 ¼ C ASHP

C f,D4 ¼ C ASHP + C f,V + C i,V (10.3)
In this research, the first cost of the ASHP unit was $1200, which was the same in the
two cases. The additional cost of the valves was approximately $45. The price was
relatively high because it was made to order for this experimental study. However,
if batch production of this equipment could be achieved, the additional first cost of
valves was expected to be as low as 150 CNY. It was only about 2% of the first cost