Page 321 - Defrosting for Air Source Heat Pump

316 Defrosting for Air Source Heat Pump

Stage 2: Heating season without frost formation
When the ASHP unit works in heating season without frost formation, the total run-
ning cost, C r, NFDH , includes three parts of the electricity cost: (1) electricity cost of the
compressor, C r, comp, h , (2) electricity cost of the indoor air fan, C r, id, fan , and (3) elec-
tricity cost of the outdoor air fan, C r, od, fan :

(10.21)
C r,NFDH ¼ C r,comp,NFDH + C r,id, fan + C r,od, fan
The three unknown parameters could be calculated by,

(10.22)
C r,comp,NFDH ¼ C e,unit P NFDH T Y T NFDH T ODH
C r,id, fan ¼ C e,unit P id, fan T Y T NFDH T ODH (10.23)

C r,od, fan ¼ C e,unit P od, fan T Y T NFDH T ODH (10.24)

In Eqs. (10.22)–(10.24), T ODH was the operating duration in the heating season with-
out frost formation, assumed at 12 h in this study. Considering the Eqs. (10.21)–
(10.24), the total running cost in the heating season without frost formation could
be evaluated by,

(10.25)
C r,NFDH ¼ C e,unit P NFDH + P id, fan + P od, fan T Y T NFDH T ODH
Q id,air,NFDH
C r,NFDH ¼ (10.26)
COP NFDH
where the thermal energy supplied to the indoor air during frosting operation and the
COP in this season, Q id, air, NFDH and COP NFDH , were also obtained from the previous
frosting experiments.

Stage 3: Cooling season
The total running cost for the ASHP unit in the cooling season, C r, C , consists of the
electricity cost of the compressor, C r, comp, C , the electricity cost of the indoor air
fan,C r, id, fan , and the electricity cost of the outdoor air fan, C r, od, fan :

C r,C ¼ C r,comp,C + C r,id, fan + C r,od, fan (10.27)

In Eq. (10.27), the same as those in Eq. (10.21), the three unknown parameters were
evaluated by,

(10.28)
C r,comp,C ¼ C e,unit P C T Y T CD T ODC
(10.29)
C r,id, fan ¼ C e,unit P id, fan T Y T CD T ODC
(10.30)
C r,od, fan ¼ C e,unit P od, fan T Y T CD T ODC