Page 310 - Defrosting for Air Source Heat Pump

Technoeconomic performances 305

Experimental results & assumptions
Experimental study • Frosting operation data collected: COP, indoor
• An ASHP unit selected air thermal energy supplied
• A three-circuit outdoor coil made • Defrosting experimental results obtained:
• Two typical conditions designed Defrosting duration, power inputs, and indoor air
• Frosting/defrosting experiments undertaken thermal energy consumed
• Four types assumptions given

Economic analysis & energy equations
Techno-economic evaluation
• First cost: ASHP unit, valves and trays
• Running cost analysis • Running cost:
• Total cost evaluation as operating year Stage 1, Heating season with frost formation
• Discussions on payback periods Stage 2, Heating season without frost formation
Stage 3, Cooling season
Fig. 10.1 Flow chart for the methodology used in this study.

designed, considering the installation of valves or not. After the experimental proce-
dures were confirmed, a series of frosting and defrosting experiments was undertaken
with the frost accumulated at different FECs. Thereafter, these experimental results
and calculations, such as COP, indoor air thermal energy supplied at the frosting oper-
ation, defrosting duration, power inputs, etc., could be used as the known parameters
for the later technoeconomic evaluations. In addition, many assumptions would be
given at this step. The third step is the development work of equations, including
the first and running costs at different operating stages. At the fourth step, evaluation
results and relative discussions are given. Finally, the technoeconomic analysis on the
frosting/defrosting operations for the new ASHP unit is undertaken.

10.2.1.1 Experimental study
(1) Experimental case studies
An experimental ASHP unit was specifically established for carrying out the exper-
imental work. The experimental ASHP unit was a split-type one and it consisted of a
swing-type compressor, an accumulator, a four-way valve, an EEV, an indoor coil,
and an outdoor coil. It was modified from a commercially variable speed Daikin
ASHP unit, with its performance parameters listed in Table 10.1. In cooling mode,
the rated capacity was 5.2 kW, the rated power consumption 1600 kW, and the rated
COP 3.25. In heating mode, the rated capacity was 6.5 kW, the rated power consump-
tion 1840 kW, and the rated COP 3.53. In Harbin, the price of this unit was about
$1200.
In the experimental ASHP unit, the indoor coil used was the prototype, with its
model name of FTXD50FVM. However, to calculate the FECs in the experiments,
water-collecting trays were designed and located between the circuits. Thus, consid-
ering the installation of valves and trays, a three-parallel refrigerant circuit outdoor
coil was specially designed and carried out. Three solenoid valves and three manual
stop valves were installed at the entrance and exit of each circuit in the outdoor coil.
The solenoid valves can stop the refrigerant flowing into/out of a circuit, and the man-
ual stop valves were used to adjust their flow rates. Using this method, the frost