Influence of Coiled Wire Presence on the Convective Heat Transfer Coefficients in R-600 Condensers

An experimental investigation has been performed to examine the heat transfer enhancement achieved by helically coiled wire inserts during forced convective condensation of R-600 vapor inside horizontal tubes. The experimental set-up is a vapor-compression refrigeration cycle. This system includes a main condenser which is a coaxial double-pipe counter-flow heat exchanger with water as a coolant. To reach the favorable vapor qualities, pre-condenser and after-condenser systems were invoked. Experiments were carried out for a plain tube and five different coiled wire inserted tubes. At each test, various parameters were measured like refrigerant mass flow rate, inlet and outlet water temperature of the condenser, refrigerant pressure, etc. Using the acquired data, heat transfer coefficients were calculated for different tubes. Investigation of the results showed that increasing the thickness of the wires can augment the heat transfer rate. Also, it is seen that reducing the coil pitch can enhance the heat transfer rate as high as 31.6%. Also, it was seen that employing coiled wire inserts inside the tube, increases the average heat transfer coefficient up to approximately 80 % regarding the plain tube results.