Void Fraction and Flow Pattern of Dimethyl Ether in a Horizontal Condenser: Effect of Condensing Temperature

Flow quality, void fraction, and flow pattern are important parameters in two-phase flow that are often found in evaporator and condenser of an air conditioner. Experimental or simulation studies concerning these parameters are still limited. This paper discusses these three parameters of RE170 (dimethyl ether/DME) refrigerant in a horizontal condenser. The study was carried out under different condensing temperatures on an air conditioner with a nominal cooling capacity of 2.64 kW. Based on simulation using Refprop software, it is obvious that condensation occurs first at the lower condensing temperature. From the condenser inlet to 90% of condenser length, the higher rate of change of void fraction is found for the higher condensing temperature. At the axial position near the condenser outlet, however, the higher rate of change of void fraction is found for the lower condensing temperature. Three main flow patterns are identified in the condenser: annular, intermittent, and stratified-wavy. Annular flow occurs at flow quality higher than 0.33, while the stratified-wavy flow is found at a range of flow quality 0 to 0.15. Intermittent flow is found at the transition between the annular and stratified-wavy flow.