Potential of latent thermal energy storage for performance improvement in small-scale refrigeration units: A review

Over the past two decades, latent thermal energy storage has been a proven technology to improve the performance of refrigeration appliances. In this work, an up to date literature review is presented on the application of latent thermal energy storage into small-scale refrigeration systems, including domestic refrigerators, beverage coolers, display cabinets, etc. Initially, a data analysis is carried out to uncover trends and limitations, where it is presented the rate of publications, as well as the number of investigations on different systems and types of PCMs, not found in previous reviews. Subsequently, the improvements achieved by coupling phase-change materials (PCMs) into small-scale systems are introduced in sections that discuss the thermal management, compressor run-time, energy efficiency, economic, and environmental aspects. After summarizing some pros and cons of placing the PCM at different locations, a new section examines the advancements on the mathematical modelling of PCM-based refrigerators. Prior to conclude, a perspective section discuss the potential of using cascaded PCMs and the necessity to develop an integral PCM heat exchanger. At that point, a novel configuration for a wire-on-tube PCM condenser is proposed as another contribution of this work. Limitations and opportunities for future investigations are also explored, including: the utilization of bio-based PCMs, application of machine learning and decision making techniques to select PCMs and find optimal configurations; and the discussion of carbon emissions. Despite the necessity of continuous research and development, the actual knowledge on PCM-based refrigerators is sufficient for a transition from laboratory-scale to a commercial implementation.