An experimental study of the flow phenomena of R134a flowing through a capillary tube

In the present work, the flow phenomena of the R-134a flowing through the adiabatic capillary coiled tube are experimentally studied. The main parameters relating flow conditions such as inlet pressure, degree of subcooling mass flow rate, are examined. The test section is made from copper tubing with inner diameters of 1.07mm and the coil diameters of 50 mm. The local pressure and temperature distribution along the length of the capillary coiled tube are measured at several inlet pressures and various degrees of subcooling. The experiments are performed at inlet pressure ranging from 10 to 12 bar, mass flow rate from 9 to 11 kg/hr, and the degrees of subcooling from 6 to 10.5 degrees C. It was found that there are three regions of the refrigerant flow inside capillary tube including subcooled liquid region, metastable liquid region, and metastable two-phase region and these are discussed in details.