RESEARCH ON CONTROL STRATEGY OF REFRIGERATION AIR CONDITIONING SYSTEM BASED ON MINIMUM PRESSURE DIFFERENCE BETWEEN CONDENSER AND EVAPORATOR

摘要

A new control strategy applied to refrigeration and air conditioning (R&AC) systems with variable-speed compressor and electronic expansion valve (EEV) is presented in this paper. Based on mathematical modeling, the system running efficiencies on different pressure difference between condenser and evaporator are analyzed. As a result, a distinctive control strategy is proposed for energy saving by holding the EEV opening as maximal as possible in order to minimize the pressure difference. This strategy of EEV opening control is different from that of feedback control according to the superheat of evaporator, and pays sufficient attention to utilizing the heat exchanging ability of condenser for optimizing the system operating performance. In this strategy, the supercooling of condenser is one of control parameters, and consequently a cross-flow heat exchanger model distinguishing refrigerant flow patterns is used. A new EEV model associated with supercooling control and a corresponding R&AC system controller are both described. The simulation results have been proved on a refrigeration & air conditioning experiment system.