PCM-Based heat exchanger for Low-Temperature hybrid residential air conditioning with ground-source heat pumps: Design and validation

This work presents the design, experimental validation, and performance evaluation of a patented phase change material–based thermal energy storage (PCM-TES) heat exchanger integrated into a hybrid open-loop ground-source heat pump (GSHP) system for low-temperature residential heating and air-conditioning applications. The system employs phase change materials to store and release thermal energy, providing thermal buffering under variable operating conditions. The main objective is to characterize experimentally the thermal behavior, energy buffering capacity, and internal heat-transfer mechanisms of the PCM-TES unit under controlled and repeatable conditions. A fully instrumented experimental test bench was developed, including calibrated thermal energy meters and a high-resolution temperature sensor network to monitor the heat-transfer fluid (HTF), PCM domain, and inlet and outlet conditions in real time. An experimental campaign was conducted for twelve operating configurations, varying the PCM load factor and the thermal extraction rate, and including sensible-heat-only reference cases. The results show that the integration of PCM significantly improves temperature stability during discharge, increases effective thermal autonomy, and reduces sensitivity to load variations through latent heat storage. Axial temperature gradients within the PCM-TES unit were found to be negligible, supporting the validity of simplified one-dimensional thermal modeling approaches. These experimentally validated results provide a reliable basis for future system-level performance assessments, fault detection methodologies, and the deployment of PCM-based thermal energy storage in residential GSHP applications.