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Experimental analysis and simulation of coils in an air-to-water heat pump operating at full and part load conditions.

Number: 2325

Author(s) : KRISHNAMURTI S., ORTEGA I., SIERES J., AUTE V.

Summary

Dual mode heat pumps are a crucial technology to minimize emissions from cooling and heating systems as we strive to achieve a decarbonized future. With the use of variable speed drives, these heat pumps have become more efficient. However, under extreme part load conditions, the control of these devices is challenging and current heat exchanger model capabilities cannot fully handle such phenomenon. This research presents comprehensive experimental analysis of an air-coil used in an R410A air-to-water heat pump. The coil has 2 rows of 36 tubes each. The refrigerant flow is distributed in 5 refrigerant circuits of 7 hairpins each (14 tubes per circuit), arranged one on top of the other, plus an additional hairpin located at the bottom of the coil that collects the refrigerant flow from the 5 circuits. In order to estimate the refrigerant temperature profiles in the coil circuitry, temperature sensors were attached on different locations of the tubes of the coil. Airflow maldistribution measurements were also conducted. Experiments were performed combining different compressor and fan speed values. The experimental temperature profiles suggest that the refrigerant distribution in each circuit is not equal and that some refrigerant accumulation and/or low refrigerant flow occurs in the lower refrigerant circuits. This is in part due to gravity, and the effect is more pronounced when operating the unit with low compressor speeds. The experimental data were used to validate existing air-to-refrigerant
heat exchanger models and to identify future model development and validation initiatives. The predicted performance agreed with measured data within ±5%, but this deviation was significantly higher for low mass flux conditions, highlighting the need for improved modeling of gravity for accurate predictions of refrigerant mass flow
maldistribution in headers.

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  • Original title: Experimental analysis and simulation of coils in an air-to-water heat pump operating at full and part load conditions.
  • Record ID : 30033176
  • Languages: English
  • Subject: Technology
  • Source: 2024 Purdue Conferences. 20th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2024/07/17

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