scope:

Commercialand industrial refrigeration systemsconsumea significant portion of U.S. electrical energy. In this research, advanced expansion valve and control algorithms are evaluated to quantify the potential energy savings due to improved system regulation and efficient start-up of vapor-compression refrigeration systems. The performance of the new micro-electromechanical system (MEMS) actuators with different control strategies is compared with that of the standard mechanical valves and a commercially available superheat controller. Additionally, thisresearchincludesacomprehensivesetofexperimental tests that identify themosteffective elements ofadvancedvalve control strategies, including the impact of refrigerant migration control strategies. The experimental results confirm that 30% to 50% improvements in cyclic coefficient of performance (COP) are possible using improved expansion valve controls, while the benefits of preventing refrigerant migration do not outweigh the additional cooling achieved if refrigerant continues to flow through the expansion valve during the compressor OFF period.