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Experimental Thermodynamic Investigation on the Refrigerant Charge in a Transcritical $CO_{2}$ Electric Bus Air Conditioning System
| Content Provider | MDPI |
|---|---|
| Author | Wang, Haidan Li, Shengbo Song, Yulong Yin, Xiang Cao, Feng Gullo, Paride |
| Copyright Year | 2021 |
| Description | Due to its considerable impact on climate, bus air conditioning systems are being pushed to take a new and sustainable path. Electric buses relying on transcritical $CO_{2}$ air conditioning units are perceived to be eco-friendly and future-proof solutions to achieving such a target. However, in order to have highly efficient air conditioning systems, the $CO_{2}$ charge needs to be optimized. In this paper the energy and exergy-based analyses were performed to investigate the effect of normalized refrigerant charge on the system performance by using a test rig of a transcritical $CO_{2}$ air conditioning unit for an 8 m electric bus. Results showed that the normalized refrigerant charge range of 0.248~0.336 was recommended in order to ensure the maximum coefficient of performance (COP). In addition, in sufficient charge conditions, the optimal COP, cooling capacity and exergy efficiency were 1.716, 18.97 kW and 29.79%, respectively, under the standard refrigeration condition of 35 °C/27 °C. As the ambient temperature rose from 35 °C to 40 °C, the COP, cooling capacity and exergy efficiency decreased by 16.03%, 10.90% and 12.22%, respectively. Furthermore, the exergy efficiency was found not to be sensitive to slightly insufficient charge, whereas overcharge was observed to be even beneficial to exergy efficiency under the condition of ensuring the maximum COP. In addition, insufficient refrigerant charging seriously affected the irreversible losses in the indoor and outdoor heat exchangers, whereas slight overcharge had little effect on the component exergy efficiency. Finally, the need to improve the $CO_{2}$ compressor efficiency to enhance the system performance was revealed. |
| Starting Page | 5614 |
| e-ISSN | 20763417 |
| DOI | 10.3390/app11125614 |
| Journal | Applied Sciences |
| Issue Number | 12 |
| Volume Number | 11 |
| Language | English |
| Publisher | MDPI |
| Publisher Date | 2021-06-17 |
| Access Restriction | Open |
| Subject Keyword | Applied Sciences Energy and Fuel Technology Industrial Engineering Transcritical Co2 System Electric Bus Refrigerant Charge Exergy Experimental Investigation R744 |
| Content Type | Text |
| Resource Type | Article |
