Mathematical modeling and optimum design for capillary tubes in R-410A Air Conditioner

Abstract

The capillary tube is crucial for vapor compression refrigeration systems to control refrigerant pressure and flow. The selection of capillary tubes is based mainly on the experience of the technicians on the trial-and-error method. Improper and incorrect selections will affect the system's energy efficiency. This research developed a mathematical model of the design of capillary tubes for R-410A refrigeration systems. The model was verified by experiment. The variations in diameter and length of the capillary tube and the effects of these variations were analyzed by using the verified model. The rate of change of refrigerant properties is low during the initial flow and higher when closer to the outlet. The research analyzed the math model with the air conditioner in the 0.75 – 5 TR range. The research outputs the simplified capillary tube selection chart for various cooling capacities which can be conveniently used by the designer. A smaller diameter needs a shorter length but must be larger than the choked flow limit. A larger diameter needs a longer length and resulting in unnecessarily high costs.

URN:NBN:sciencein.jist.2023.v11.403