The use of phase change materials in domestic refrigerator applications

This paper presents a conventional domestic refrigerator analysis that demonstrated that for current single speed compressors, efficiency increases with compressor displacement. The method proposed to exploit the superior performance of large compressors is to accumulate their high cooling capacity in a PCM increasing the refrigerator autonomy i.e. off-cycle period, without power supply, from a few minutes to several hours. Employing thin PCM slabs (≤ 5 mm) ensures that the net volume of the compartment is not substantially reduced, while moderate length compressor run times (i.e. on-cycle times) are obtained. Both the numerical simulation and the experimental results demonstrated that the integration of a 5 mm PCM slab into the refrigerator allowed between 3 and 5 hours of continuous autonomous operation depending on the thermal load. The
combination of a large displacement compressor and a thin PCM is a novel design approach with the potential to significantly enhance refrigerator efficiency and temperature stability.
The CFD model predicted the airflow and temperature distribution within the thermal storage refrigerator. Several design options were simulated to identify the most effective PCM configuration (horizontal or vertical) and the optimum phase change temperature. This analysis enabled identification of the best design options to optimise the performance of the thermal storage refrigerator. A horizontal PCM configuration was found to be more efficient than a vertical PCM. For the horizontal PCM, the CFD predicted temperatures were compared with experimentally measured values and found to be in close agreement.
Both the simulation and the experiments results suggested that a eutectic with a phase change temperature below 0°C would need to be employed to maintain the compartment temperature within the required range for domestic refrigerators.