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Refrigerant charge optimization of a variable speed residential heat pump with an expander/separator.

Number: 2154

Author(s) : OTHMAN A., BAHMAN A. M., BARTA R. B., ZIVIANI D., GROLL E. A.

Summary

Space cooling and heating account for almost one-third of the global energy consumption in buildings. To reduce the energy consumption of air conditioning (AC) and heat pump (HP) systems in buildings, is using variable-speed compressors during part-load conditions. Nonetheless, issues arise during part-load operation, as the required refrigerant
charge for optimal performance is not uniquely identified and varies depending on indoor and outdoor conditions. Moreover, the control of the expansion device at varying operating conditions and charge levels also presents unique challenges. In this work, an R-410A 5-ton (17.58 kW) HP unit equipped with a variable-speed rolling piston compressor and an
expander/separator has been considered to evaluate the effect of refrigerant charge during seasonal operation. The expander/separator replaces the conventional expansion device and generates auxiliary power during the expansion process. Using a validated and fully-tuned mechanistic steady-state HP cycle model, the refrigerant charge was increased
from 4.2 kg to 5.6 kg in 0.01 kg increments for six experimental testing conditions. The results showed that the coefficient of performance (COP) was maximized at a refrigerant charge of approximately 5 kg, with minor alterations of ±0.03 kg depending on the testing conditions. The cooling capacity increased directly with the increase in refrigerant charge, but the expander/separator was over-flooded, and therefore the power output was reduced. These
findings illustrate the importance of developing a refrigerant charge management system due to the necessity to establish means of controlling the refrigerant charge level for various ambient conditions, especially considering that future cooling technologies will be using low-GWP working fluids.

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  • Original title: Refrigerant charge optimization of a variable speed residential heat pump with an expander/separator.
  • Record ID : 30030495
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2022/07/10

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