Mechanical sub-cooling vapor compression systems: Current status and future directions

•Recent progress with respect to mechanical sub-cooling systems is examined.•Both theoretical and experimental studies are reviewed.•Important results with respect to performance characteristics and reduced maintenance are examined.•Potential for these systems for energy conservation is substantial.•Future directions to help put these systems in practice are also outlined.

Using mechanical sub-cooling systems to increase COP of vapor compression cycles is a known method in literature to save energy and increase efficiency. Recently, much progress has been made with respect to investigation into its different aspects that can help to put it into practice. Numerical and experimental works are considered for the purpose of highlighting this progress. These can be categorized as: a) simulation of performance characteristics resulting from different refrigerant combinations in dedicated mechanical sub-cooling systems, b) variation in performance characteristics for a vapor compression cycle using integrated mechanical sub-cooling because of fouling, c) experimental study about consequences of employing a dedicated mechanical subcooling cycle with a simple vapor compression system, and d) experimental investigation about consequences of employing a subcooler in a two-stage refrigeration cycle. Some important results are discussed. Finally, some suggestions are made to provide direction into future research in this area to help put it into practice.