A theoretical study of new-style cool storage air-conditioning systems with high-temperature water

Abstract

Cool storage technology is an effective means of shifting peak electrical loads by storing cooling capacity during off-peak time. A new-style cool storage scheme working with high-temperature water for air-conditioning is introduced in this paper. By supercooling refrigerant before being throttled with 2–38 °C water, the refrigerating output is raised and the water's sensible heat is converted to cool energy to be used for cool storage air-conditioning. The characteristics and performance of three systems with different water cycle patterns, viz., unmixed, fully mixed and partially mixed, were theoretically analyzed and simulated. For an unmixed system, its performance is sensitive to g, the ratio of heat capacity flow rate of supercooling water to that of refrigerant, and the total cool storage efficiency reaches a max value when g = 1. For a fully mixed system, its performance changes with time and the supercooling efficiency decreases gradually. For a partially mixed system, a thermal transfer model for the thermally stratified water tank was established in order to simulate the time-dependent temperature profiles. The influences of water mass flow rate, design service time and tank height on its dynamic performance were investigated. The results help design, control and optimization of these systems.