Page 320 - Defrosting for Air Source Heat Pump
P. 320
Technoeconomic performances 315
In this period, the electricity cost of the indoor air fan was given by,
(10.14)
C r,id, fan,DF ¼ C e,unit P id, fan T Y T FDH T OT T DD
And thus, using Eqs. (10.12)–(10.14), the following equation yields,
(10.15)
C r,DF ¼ C e,unit P DF + P id, fan T Y T FDH T OT T DD
The electricity cost at the defrosting operation, C r, DF , was calculated by Eq. (10.12).
In this equation, the electricity consumption data of the compressor and indoor air fan
were collected in the experimental study, and are listed in Table 10.7.
Finally, in Eq. (10.4), the corresponding electricity cost of indoor thermal energy
consumption during the defrosting operation, C r, ITE , was evaluated by,
Q id,air,DF
C r,ITE ¼ (10.16)
COP F
The COP F could be calculated with the experimental data during the frosting opera-
tion by,
Q id,air,F
(10.17)
COP F ¼
P comp + P id, fan + P aver,od, fan T DF
The energy supplied for the indoor environment, Q id, air, F , was:
Q id,air,F ¼ c i,air m i,air Δt ¼ c i,air ρ i,air i,air T ind,in T ind,out Þ (10.18)
V
ð
where ρ i, air was the density of air in the indoor heated space, V i, air the volumetric flow
rate of air passing through the indoor coil, and T ind, in and T ind, out the average values of
the measured air temperatures at the inlet and outlet of the indoor coil. All parameters
were obtained in the experiments as well as the thermal energy consumed from the
indoor air during the defrosting operation, Q id, air, DF in Eq. (10.16).
Considering Eqs. (10.4), (10.10), (10.15), and (10.16), the total running cost of the
ASHP unit in the heating season with frost formation was:
C r,FDH ¼ C e,unit T Y T FDH T OT ½ P f + P id, fan + P ave,od, fan T DF
(10.19)
Q id,air,DF
+ P DF + P id, fan T DD +
COP F
It was evaluated by Eqs. (10.4), (10.11), (10.12), and (10.16):
Q id,air,F + Q id,air,DF
C r,FDH ¼ + C r,comp,DF + C r,id, fan,DF (10.20)
COP F
