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The enhancement of heat transfer performance in heat exchanger is achieved by reducing the size of the hydraulic diameter or by using a working fluid that has a better thermal conductivity compared to conventional working fluids. The application of a small hydraulic diameter can be found in the microchannel heat exchanger (MCHE). The design and the testing of the MCHE were done in this research. The MCHE was tested with several working fluids, such as the distilled water, the Al2O3-water nanofluids at 1%, 3% and 5% volume concentration, and the SnO2-water nanofluids at 1% volume concentration. The temperature of inlet and outlet were set at 50°C and 25°C, respectively. The variations of flow rate at the inlet were applied from 100 ml/min up to 300 ml/min. The addition of nanoparticle in the base fluid was proven to improve the heat transfer of the MCHE, the 5% Al2O3-water and 1% SnO2-water nanofluids are able to absorb the heat 9% and 12% higher than the base fluid. The overall heat transfer coefficient of MCHE with 5% Al2O3-water and 1% SnO2-water nanofluids were 13% and 14% higher than the base fluid. [ABSTRACT FROM AUTHOR]

Abstract: Heat pipes have been widely used as one of the alternative methods to absorb more heat in the cooling systems of electronic devices. To improve the thermal performance of heat pipes, the practice of using various combinations of heat pipes and nanofluids has been widely observed. The purpose of this research was to determine the concentrations and the types of nanofluids that can best enhance the thermal performance of screen mesh wick heat pipes and to determine the effect of coatings on the structure of the screen mesh wick after using nanofluids as the working fluid. In this research, screen mesh wick heat pipes were manufactured and tested to determine the thermal resistance of nanofluids such as Al2O3–water, Al2O3–ethylene glycol, TiO2–water, TiO2–ethylene glycol and ZnO–ethylene glycol charged in the screen mesh wick heat pipes. The concentration of the nanoparticles was varied from 1% to 5% of the volume of the base fluid. The screen mesh wick heat pipe with the best performance was that which used Al2O3–water nanofluid with 5% volume concentration. Using nanofluids in the heat pipes resulted in the formation of a thin coating on the screen mesh surface from the element of the nanoparticles. However, the thin coating promotes good capillary structure. The higher thermal performance of heat pipes charged with nanofluids proved the potential of nanofluids as a substitute for conventional working fluids. This finding makes nanofluids attractive as working fluids in screen mesh wick heat pipes. [Copyright &y& Elsevier]