A Numerical Simulation of the Effect of Ambient Temperature on Capillary Tube Performance in Domestic Split Air Conditioners with R22 Alternatives

Abstract

A numerical model has been formulated to simulate the capillary tube insplit air conditioners of 1 and 2 TR capacities under high outdoor air temperatures. The outdoor air temperature was varied from 35 to 55°C with 5 °Cincrements. Three environment friendly refrigerantswereused as alternatives to R22. They are  R290, R407C and R410A. Finite difference method has been adopted in conjunction with EES software. This model is capable of predicting pressure, temperature, quality, velocityandviscositydistributions through the capillary tube for all refrigerants. The geometrical parameters and input conditions to the capillary tube model areextracted from experimental data.  Theseinclude inner diameter, mass flow rate, surface roughness, temperature and pressure of the subcooledliquid refrigerant.  Theresults show that the capillary choking length increases with increasing outdoor air temperature.    Results of the simulation show thatR290 needsmore capillary length than the other refrigerants investigated,whereas  R410A needs less capillary tube length.

Keywords: Capillary tube simulation; capillary tube with R22,R290, R407C, R410A; high ambient effect on capillary tube.