Experimental Study on the Enhanced Thermal Performance of Two-Phase Closed Thermosyphon Using Mechanical and Chemical Treated MWCNTs Nanofluids

Abstract

Nowadays the two-phase closed thermosyphon (TPCT) has been widely used as an important heat transfer medium for passive cooling systems. Since the enhancement of the performance of electronic device releases a considerable amount of heat, the development of working fluids which can improve thermal performance of the TPCT is necessary. In this experiment, two different type of MWCNT nanofluids were successfully made by using ball-mill process and alkaline treatment. The morphological and structural analysis were conducted by using transmission electron microscope (TEM), fourier-transform infrared spectroscopy (FT-IR). Also thermal conductivity of modified MWCNT nanofluids were investigated by introducing transient hot wire method. The results of TEM, FT-IR and thermal conductivity showed that the MWCNTs were successfully functionalized as well as had higher thermal conductivity. The TPCT was fabricated with copper tube and total length of the TPCT is 700mm, in which the evaporator section, the adiabatic section and the condenser section are 150mm, 400mm, and 150mm, respectively. The experiment of the thermal performance of the TPCT was evaluated by introducing RMS value of the temperature of the evaporation section, thermal resistance and heat transfer coefficient at five different filling ratios, 10%, 30%, 50% and 70% by ratcheting up heat loads in five levels, 5W, 8W, 10W, 13W and 15W. The overall results showed that the both of modified MWCNT nanofluids can decrease thermal resistance and increase the heat transfer coefficient, especially at 10% filling ratio with 8W. M-CNT nanofluid can even enhance the thermal performance of TPCT at 30% filling ratio with all heat loads.