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Experimental study on portable air-conditioning system with enhanced PCM condenser.

Number: pap. 2483

Author(s) : QIAO Y., MALLOW A., MUEHLBAUER J., et al.

Summary

A portable personal air-conditioning system with a vapor compression cycle (VCC), electrical battery, and thermal battery is an attractive option for localized cooling as compared with stationary air-conditioning systems. A phase change material (PCM) can be used for storing waste heat from the VCC condenser, thereby acting as a thermal battery. In the PCM condenser, copper tubes are submerged in the PCM container. Due to the low thermal conductivity of pure PCM, the overall heat transfer coefficient of the PCM condenser is limited resulting in high VCC condensing pressure and thus, low VCC coefficient of performance (COP). Therefore, it is necessary to improve VCC system performances by applying heat transfer augmentation in PCM. In this work, a portable air-conditioning system with heat transfer enhanced PCM that stores heat from condenser during VCC operation and is regenerated by a thermosyphon operation is proposed. The system also includes a receiver to address the charge difference between the thermosyphon and the VCC operation. The paper experimentally studies the effects of the following three types of enhanced PCM condensers on the system performance: (1) copper mesh enhanced PCM with helically coiled copper tube branches and large refrigerant distribution headers (CMPHX), (2) graphite matrix enhanced PCM with straight copper tube branches and small headers (GMPHX1), and (3) graphite matrix enhanced PCM with straight copper tube branches and large headers (GMPHX2). Results show that this system operates properly and effectively during both VCC and PCM regeneration operations. The system can provide four hours of continuous cooling, and the PCM can be fully regenerated after 7.4 hours by thermosyphon operation. The comparisons of three PCM condensers indicate that the system with GMPHX2 performs the best with the average VCC COP of 4.7. The VCC system with CMPHX has an average COP of 4.2, and GMPHX1 has an average COP of 3.1. GMPHX2 has the best heat transfer enhancement with an overall heat transfer coefficient of 632.1 W·m-2·K-1, which is more than twice of GMPHX1 and five times of CMPHX. Moreover, GMPHX2 can achieve more uniform refrigerant flows and PCM temperature distributions than GMPHX1. This leads to the higher utilization ratio of PCM latent heat. CMPHX is the second best but needs larger heat transfer surface area and inner volume as well as more refrigerant charge. In conclusion, the system design with GMPHX2 is recommended due to its small refrigerant charge, high VCC COP, and the use of good heat transfer enhancement material.

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Pages: 10

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Details

  • Original title: Experimental study on portable air-conditioning system with enhanced PCM condenser.
  • Record ID : 30024577
  • Languages: English
  • Source: 2018 Purdue Conferences. 17th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2018/07/09

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