household refrigeration, flow visualization, T-junction, phase separation, flash tank
The objective of this study was to develop a methodology for designing a T-junction liquid-vapor separator for household refrigerators. The influence of the following independent parameters on the separator performance was studied: i) refrigerant mass flow rate, ii) inlet vapor quality, iii) evaporation temperature, iv) critical droplet diameter, v) critical bubble diameter and vi) suction ratio. For modeling purposes, the T-junction was divided into three sub-models: inlet, vapor and liquid branches. The inlet branch sub-model revealed that a proper phase separation occurs with larger diameters as the refrigerant mass flow rate and vapor quality increase. The dimensions of the vapor branch are governed by the droplet diameter, vapor mass flow rate and evaporation temperature while the dimensions of the liquid branch are dictated by concepts such as time of liquid degassing and residence time. Additionally, a testing facility was designed and constructed to allow the flow visualization through acrylic made T-junctions of distinct geometries. For a typical HC-600a domestic refrigeration condition a T-junction with an inlet diameter of 7 mm, a vertical diameter of 28 mm and total height of 40 mm was selected as one of the suitable options. The separator geometry and flow phenomena were experimentally investigated and associated with the refrigerating capacity of the fresh food and freezer compartments during closed door conditions.