THERMAL PERFORMANCE ANALYSIS OF JET IMPINGEMENT HEAT SINK WITH NANOFLUID

Abstract

Small scale thermal devices are very effective and interesting to use for the applications which involves large amount of heat flux. The current investigation introduces the concept of heat sink with combination of jet impingement, micro – channel and air foil shaped pillars. In the current research three techniques have been operated to enhance the rate of heat transfer in a heat sink. The amalgamation of Impingement of jet, air foil pillars and Nanofluid are used. Nanofluid has a lot of potential to enhance the heat transportation in contrast to the water. The use of Nano particles in the base fluid like water also augment the various properties which helps in the heat dissipation from the components subjected to high temperatures. In the current study, the various combinations of jet-channel and pillars have been investigated comparatively. A numerical model is designed to explore the thermal performance of jet impingement with constant heat flux. The study has been carried out for a constant value of heat flux at the bottom surface. The investigation has been executed with the help of three dimensional numerical model using Computational fluid Dynamics. In the current work, computational fluid dynamics investigation has been performed in case of air foil shaped pillars in heat sink with impingement of jet. The steady state conditions are assumed for the laminar and incompressible flow. For the purpose of study dimensionless variables are formed. The investigation has been made in terms of thermal and fluid attributes. The performance of jet impingement was predicted in terms of different parameters like temperature rise, drop in pressure and coefficient of heat transfer, Nusselt number, thermal resistance and pumping power. At the onset the model has been validated with the inspection carried out already in experimental form. The model has been validated with the available experimental and simulation results. The study has been performed using water, CuO – water Nanofluid and V Al2O3 – water Nanofluid with different concentrations. CuO is used with 0.5 % and 1% concentration and Al2O3 is used with 5% concentration. Augmentation in pitch ratio, leads to increase in temperature for a particular value of height ratio. Also the heat transfer coefficient gets lowered with the increase in pitch ratio. So proper selection of dimensionless parameters to increase the heat dissipation is of utmost importance. From the results the conclusion is made that the use of airfoil pillars and Nanofluid has increased the thermal characteristics of the three dimensional model in the form of heat exchange coefficient by almost 28.2%. The Nanofluid has been utilized for the 0.5% concentration. Minimum temperature is found in case of jet-pillar combination. The channel flow diminished the heat exchange coefficient. With pillars, augmentation in height diameter proportion, almost 44 % reduction in the temperature of the base has been noticed. Also 24 % augmentation has been deduced in the convection coefficient, with an increase in the design parameter. Advancement in height ratio leaded to 16 % improvement in the Nusselt number. From the results minimum 14 % reduction in the temperature is detected for height ratio with Nanofluid (CuO -1%). Also in differentiation with water minimum 10 % reduction is noticed. The model is also analysed for separate combinations of jet-channel and pillars using Al2O3 – water Nanofluid with 5% concentration. The relation between thermal resistance and pumping power is predicted.