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Evaluation of a low charge heat pump circuit using propane.

Number: No 203

Author(s) : DANKWERTH C., METHLER T., BRAUNGARDT S., SONNER C., OLTERSDORF T., MIARA M., SCHOSSIG P., SCHNABEL L.

Summary

A low refrigerant charge brine-to-water heat pump circuit was evaluated addressing a heating capacity of 5 – 10 kW and using propane as refrigerant. Propane is a natural refrigerant, has a low global warming potential (GWP) of three and attractive thermodynamic properties. No regulations, except for safety, are expected to apply for this refrigerant. Therefore it was chosen as refrigerant for this evaluation, the refrigerant charge of propane was limited to 150g, resulting in 0.45kg of CO2 equivalent. The reduction of charge was achieved with different design approaches and techniques: The main goal was to minimize the internal volume on the refrigerant side in all components and tubes. The two heat exchangers and the liquid line are the components impacting the charge the most. To reduce the internal volume, different design aspects were taken into account: The condenser and evaporator are designed with an asymmetric plate profile and a long thermal length, the liquid line was designed as short and thin as possible, and the filter dryer in the liquid line was shifted to the suction line. Also, the refrigerant absorption in the oil has a large impact on the refrigerant charge. The majority of the oil is in the compressor sump and the rest in the refrigerant circuit. To reduce the quantity of refrigerant in the oil, the amount of oil was minimized and the arrangement of components in the refrigerant circuit was chosen carefully to prevent oil retention. The charge reduced heat pump circuit was tested with two different inverter-driven compressors (suction gas-cooled scroll compressor and a hot gas-cooled twin rotary compressor) at various points of operation. This paper presents the results of the experimental evaluation and discusses the safety issues and potential for further optimization.

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  • Original title: Evaluation of a low charge heat pump circuit using propane.
  • Record ID : 30030037
  • Languages: English
  • Subject: Technology
  • Source: 13th IEA Heat Pump Conference 2021: Heat Pumps – Mission for the Green World. Conference proceedings [full papers]
  • Publication date: 2021/08/31

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