Studies on Heat Transfer and Pressure Drop Characteristics of Nanofluids in Microchannels

Abstract

High heat fluxes devices in an electronic industry pose a thermal challenge to the researchers of this area. Over the past decade, the use of microchannel heat sink to remove the high heat load from the active heat source has been studied. But as the amount of heat generated is quite high, so, an efficient fluid is required to enhance the cooling performance of microchannel heat sink. The suspensions of nanoparticles in the base fluids term as nanofluids proves an efficient fluid for the microchannels. This present work focuses to compare the different types of nanofluids flowing through the microchannels and find the nanofluids with high heat removal capacity. In the present work, nanoparticles such as alumina, copper oxide (CuO) and multiwalled carbon nanotubes (MWCNT) are extensively used with different types of base fluids such as water (W) or water/ethylene glycol (W/EG) mixtures (90:10, 80:20, 70:30, 60:40 and 50:50). Nanoparticles are dispersed at different concentration ranges from 0.1 vol % to 5 vol % in the base fluids by using two step method. Alumina nanofluids are stable without the use of any kind of surfactant while CuO nanofluids get stabilized by using 0.2 wt % sodium dodecyl sulphate and MWCNT are stabilized with 0.25 wt % of Gum arabic. Further, sonication can be done by using ultrasonicator water bath at a fixed frequency to make more stable nanofluids. As there is no fixed time for sonication has been reported, so optimization of sonication can be done on the basis of thermal conductivity measurements at 40 min, 60 min, 80 min and 100 min. For 80 min of sonication, maximum enhancement in thermal conductivity is observed. The stability of nanofluids can be determined by measuring the absorbance, thermal conductivity and zeta potential of nanofluids in terms of days without disturbing or shaking the samples.