Application of a Phase-Change Material Heat Exchanger to Improve the Efficiency of Heat Pumps at Partial Loads

Koharu Tani, Sayaka Kindaichi (), Keita Kawasaki and Daisaku Nishina
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Koharu Tani: Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima 739-8527, Japan
Sayaka Kindaichi: Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima 739-8527, Japan
Keita Kawasaki: Department of Architecture and Structural Engineering, National Institute of Technology (KOSEN), Kure College, Kure 737-8506, Japan
Daisaku Nishina: Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima 739-8527, Japan

Energies, 2025, vol. 18, issue 14, 1-18

Abstract: Inverter-equipped heat pumps allow for increased energy efficiency. However, air conditioning (AC) systems often operate at low load ratios below where inverter control is effective, which reduces their energy efficiency. We developed an AC system that increases the apparent load ratio of the heat pump by using a phase-change material (PCM). Cooling and heating experiments were conducted with a PCM heat exchanger, which comprised aluminum plates and fins filled with paraffinic PCM. The result indicated a high heat transfer coefficient of >70 W/(m 2 ·K). A simplified numerical model of the PCM heat exchanger as a lumped constant system was created based on the experiment. The calculations generally reproduced the experimental results, with root mean squared errors of 0.39 K for cooling and 0.84 K for heating, confirming their accuracy. Simulations were then conducted to evaluate the energy performance of the proposed system for the cooling season. While low load operation accounted for 39% of the total AC time for a non-PCM system, it was reduced to 2.7% for the proposed system. The proposed system demonstrated load ratios of 50–60% for most of the season, achieving an energy reduction of 11.4% owing to the improved efficiency at partial load ratios.

Keywords: inverter heat pumps; energy efficiency; phase change materials (PCMs); PCM heat exchanger; heat transfer coefficient; numerical model; energy consumption (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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