Establishment and solution of the RNC flow network model

Abstract

Refrigerant natural circulation (RNC) system is a closed loop recycling system which is composed of evaporator, condenser, gas pipe and the liquid pipe. The difference in indoor and outdoor temperatures will lead to the refrigerant phase-change, and the gravity difference caused by different heights of condenser and evaporator will make the low boiling point refrigerants carry on natural circulation to realize the indoor heating or cooling. In order to analyze the effect of changes in the RNC system upon the working conditions of the indoor and outdoor units as well as the function of the indoor unit, this paper describes the incidence relations among the various components of the RNC system, and establishes gas–liquid two-phase fluid network mathematical model by using the method of fluid network; besides utilizing the model, it also conducts simulator investigation of coupling characteristics of the RNC system's refrigeration condition, and makes an analysis of indoor temperature, indoor unit's air volume, the number of indoor units and the indoor unit capacity and other factors' changes on the coupling characteristics of the RNC system. The results show that under refrigeration conditions, the increase in the air volume of a single indoor unit or room temperature will result in an increase in the cooling capacity of its own indoor units, a decrease in the cooling capacity of other indoor units and a reduction in the total cooling capacity of indoor units of the RNC system; however, the decrease in the outdoor units' inlet temperature will lead to a drop in the evaporation temperature of the system and increase in the cooling capacity.