Multi-objective optimization of an externally finned two-phase closed thermosyphon using response surface methodology

•An externally finned two-phase closed thermosyphon is studied experimentally.•RSM is used to optimize the performance of the thermosyphon.•Empirical quadratic correlations are developed for he and hc.•The predicted values and the experimental results are in a good agreement.•The optimum values of 4554 and 502.986 W/m2K are obtained for he and hc, respectively. In this work, an experimental research is conducted on the thermal performance (TP) of an externally finned thermosyphon working with water. The thermosyphon is made of copper and consists of the evaporator part with 200 mm length, the adiabatic part with 100 mm length, and the condenser part with 200 mm length. Longitudinal fins with 200 mm length, 5 mm width, 0.7 mm thickness and rectangular cross section are joined to the external surface of the condenser. Empirical correlations are developed for predicting the heat transfer coefficients of the evaporator (he) and condenser (hc) as functions of thermosyphon operating parameters such as the heat input, filling ratio, coolant flow rate, and the number of fins. The experiments are designed using Central Composite Design (CCD) and conducted by measuring the thermosyphon wall temperature and temperature difference of the coolant. The operating parameters of thermosyphon are optimized using Response Surface Methodology (RSM) to achieve the highest performance. Results reveal that the presented correlations by RSM can predict the he and he with high accuracy. Moreover, the highest he of 4554 W/m2K and highest hc of 504.314 W/m2K are achieved under the optimum values of 300 W of heat input, 35.13% of filling ratio, 219.3 ml/min of the coolant flow rate, and 8 fins.