Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 52 2 2020 04 20 Three-Dimensional Simulation of Helium Gas Flow in an Aluminum Heat Sink with Rectangular Microchannel in Slip Flow Regime Three-Dimensional Simulation of Helium Gas Flow in an Aluminum Heat Sink with Rectangular Microchannel in Slip Flow Regime 477 492 2791 10.22060/mej.2018.13345.5604 FA Ahmad Reza Rahmati ِDepartment of mechanical Eng, Univ. of Kashan Mojtaba Sepehrnia Department of Mechanical Engineering, Shahabdanesh University, Qom, Iran 0000-0002-2950-1111 Journal Article 2017 08 26 In the present work, for the first time, gas flow with considering slip velocity and temperature jump boundary condition is studied in a heat sink consisting of rectangular fins and microchannels with calculating conjugated heat transfer. In this paper, helium gas flow with Knudsen number between 0.048 to 0.06 has been studied. Heat flux applied to the bottom of the aluminum heat sink is 500W/m2. The governing equation for fluid flow has been discretized using second-order upwind method and solved with using the Coupled algorithm in Ansys-Fluent commercial software. Results show that inlet and local Knudsen numbers decrease with increasing pressure ratio and also local Poiseuille number decreases with increasing inlet Knudsen number. Also, with increasing inlet Knudsen number (reduction of pressure ratio), first the average Nusselt number decreases and then increases. In this case, the average Nusselt number decreases about 54.4% with increasing Knudsen number from 0.006 to 0.024 and the average Nusselt number increases with increasing Knudsen number from 0.024 to 0.048. With increasing Knudsen number, thermal resistance increases continuously. The results show that with increasing inlet Knudsen number, slip and temperature jump coefficients increase. In the present work, for the first time, gas flow with considering slip velocity and temperature jump boundary condition is studied in a heat sink consisting of rectangular fins and microchannels with calculating conjugated heat transfer. In this paper, helium gas flow with Knudsen number between 0.048 to 0.06 has been studied. Heat flux applied to the bottom of the aluminum heat sink is 500W/m2. The governing equation for fluid flow has been discretized using second-order upwind method and solved with using the Coupled algorithm in Ansys-Fluent commercial software. Results show that inlet and local Knudsen numbers decrease with increasing pressure ratio and also local Poiseuille number decreases with increasing inlet Knudsen number. Also, with increasing inlet Knudsen number (reduction of pressure ratio), first the average Nusselt number decreases and then increases. In this case, the average Nusselt number decreases about 54.4% with increasing Knudsen number from 0.006 to 0.024 and the average Nusselt number increases with increasing Knudsen number from 0.024 to 0.048. With increasing Knudsen number, thermal resistance increases continuously. The results show that with increasing inlet Knudsen number, slip and temperature jump coefficients increase. https://mej.aut.ac.ir/article_2791_ad82140cafe816c41a9c9974e9240b7a.pdf