# Mathematical modeling of capillary tube designs for refrigeration systems using R410A refrigerant

## Authors

• Supavut Sinprasong -
• Prakob Surawattanawan ภาควิชาวิศวกรรมเครื่องกล คณะวิศวกรรมศาสตร์ มหาวิทยาลัยเกษตรศาสตร์

## Keywords:

vapor compression refrigeration, capillary tube, mathematical modeling, design

## Abstract

The capillary tube is an important device for vapor compression refrigeration systems to control refrigerant pressure and flow rate. Today, there are still many operators who lack the knowledge to use capillary tubes. The choice of equipment is largely based on the experience of the operator and the use of trial and error. Improper and incorrect selections will result in system malfunctions and affect the system's energy efficiency as well. In this work, a mathematical model of the design of capillary tubes for R410A refrigeration systems was developed. R410A was selected for this study as a replacement for R22. Hydrochlorofluorocarbon refrigerants must be discontinued in the near future for reasons of ozone depletion potential. The model evolved from the idea that the refrigerant flowing through the capillary tube changes its properties along the length of the tube through it. The capillary tube is divided into smaller control volumes. The law of conservation of mass, law of conservation of energy, and law of conservation of momentum have been applied to each control volume. The initial parameters consist of the size of the conditioner, the fluid flow rate, and the initial capillary tube size. The model can analyze the properties of the refrigerant, flow velocity, Reynold number, and friction continuously. This model makes the capillary tube design more accurate. It reduces trial and error and reduces the possibility of system malfunctions and failures. Model analysis results in the cooling system operating efficiently and saving energy.

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