Research Article
Experimental Study of a Novel Direct-Expansion Variable Frequency Finned Solar/Air-Assisted Heat Pump Water Heater
Table 5
Average COP and heating time under different ambient and operation conditions.
| | Ambient conditions | Compressor frequency | Average COP | Heating time (min) | | Ambient temperature | Solar irradiation | Air | Dual | Solar | Air | Dual | Solar |
| | 20°C | 900 W/m2 | 30 Hz | 2.23 | 2.65 | 3.35 | 382.2 | 328.8 | 336.3 | | 45 Hz | 3.37 | 2.54 | 3.29 | 191.9 | 186.7 | 237.3 | | 60 Hz | 3.85 | 3.66 | 2.92 | 129.7 | 139.3 | 201.4 |
| | 30°C | 900 W/m2 | 30 Hz | 3.40 | 3.48 | 4.15 | 260.0 | 262.2 | 276.3 | | 45 Hz | 4.12 | 3.96 | 3.88 | 147.9 | 167.2 | 200.9 | | 60 Hz | 4.07 | 3.97 | 3.61 | 122.8 | 128.6 | 161.7 |
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