A review of numerical modelling studies on short-tube orifice performance with applications to air-conditioning systems

The manufacturers of air conditioners need a precise method for calculating the critical flow rate of refrigerant through the short-tube orifice, and they must select the proper size of short-tube orifice at given operating conditions in order to achieve optimum system performance. The present study divides the research into two main groups: studies conducted under the semi-empirical model and those conducted under the theoretical model. The former model has been developed based on the single-phase orifice equation with the correction factor. The latter model applies the proper governing equations, including conservation of mass, momentum, and energy, to determine the refrigerant flow mechanism inside the short-tube orifice. Because these equations are rather difficult to solve, only a few studies have been conducted. This paper describes the details of the numerical modelling of refrigerant flow characteristics through the short-tube orifice reported in previous publications as well as the guideline for future research.