Not-in-kind cooling technologies: A quantitative comparison of refrigerants and system performance

With advances in solid-state cooling materials in the past decade, non-vapor compression technologies, or not-in-kind (NIK) cooling technologies have garnered great attention. Therefore, a universal performance index is urgently needed to compare these NIK technologies with each other and vapor compression cooling as well. In this study, a systematic method is developed to visualize the contributions to the coefficient of performance (COP) from materials (working fluids) level to the system level as a function of temperature lifts. Since the materials level COP depends solely on the materials properties under the specified cycle, it can be used for comparing refrigerants for all NIK technologies. We chose the water-cooled water chiller operating under identical conditions as the basis for the system performance comparison of all NIK cooling technologies. Upon normalizing the system COP to the Carnot COP, its variation with the system temperature lift reveals the intrinsic potential applications for each NIK cooling technology.