Thermal performance of an internally finned two phase closed thermosyphon with refrigerant R134a: A combined experimental and numerical study

In this work, the heat transfer performance of a two phase closed internally finned thermosyphon has been studied by both experimental and numerical investigations. The working fluid considered for the experiments is R134a, which is compatible with copper material and is environment friendly. The thermosyphon comprises an evaporator of length 200 mm, adiabatic length 100 mm and a condenser section 200 mm long. Rectangular cross section fins are placed internally along the length of the condenser. These are of constant area and are 5 mm wide and 1 mm thick. The fill ratios considered in this study are 20, 35, 50, 65 and 80%. Experiments are carried out for different cooling water mass flow rates of 10, 30, and 40 LPH. A lumped parameter model is developed to validate the experimental results, wherein the heat transfer equations are coupled with the mass transfer equations and the resulting equations are discretized explicitly. A boiling heat transfer coefficient correlation is developed with the experimental data to calculate the thermal resistance at the evaporator wall. The thermosyphon is tested between power levels of 25 and 150 W. The heat transfer performance of the R134a charged internally finned thermosyphon is found to be superior to that of a water charged thermosyphon.