Pressure Drop if Tetraflouroethane in Small Hydraulic Diameter Capillary Tubes

Abstract

Developing a compact device has become a current trend in this modern world which pertains to a lesser energy consumption. It also applies to a mini refrigerator unit to accommodate a small device being cooled wherein the cooling unit has to be in a smaller configuration compared with the conventional sizes. This study focuses on the pressure drop of capillary tubes with six(6) different small hydraulic diameters of 0.20mm, 0.25mm, 0.30mm, 0.35mm, 0.40mm, and 0.45mm with 3 different total lengths of 300mm, 600mm, and 900 mm. Tetraflouroethane liquid refrigerant is used as the cooling medium for the refrigeration system which allows the expansion of the refrigerant in order to absorb heat from the surroundings. In fabricating these six(6) different small hydraulic diameters, stainless steel strings were inserted into the conventional capillary tubes to reduce and attain the required hydraulic diameters. The pressure sensors were installed and pressure readings were then obtained in every 300-mm section of the capillary tube assembly. By allowing the pressurized tetrafluoroethane refrigerant to flow from its reservoir tank through the capillary tubes, pressure readings were taken by the data logger in every 300-mm section of the capillary tube. With these data, the pressure drops were then calculated. Pressure drop of all the six(6) sets of capillary tubes were tested and analyzed. The result showed that the 0.20mm with a length of 900 mm capillary tube has the greatest pressure drop compared to the other specimens of the capillary tubes. It then implies that fabricating a small hydraulic diameter of capillary tube as small as 0.20mm by stainless steel string insertion is possible for 300-mm section, however for the longer section it needs more skills in inserting the string.