Mixed convection heat transfer of AL₂O₃ nanofluid in a horizontal channel subjected with two heat sources

Mixed convection flow is investigated numerically for nanofluid flow and heat transfer in a horizontal channel considering two localized heat sources compared with pure fluid. The channel’s walls are insulated and the heat sources are at the center of the channel. Al₂O₃ nanoparticles are employed to modify the thermal conductivity of the base fluid. The effect of different parameters including Richardson number, Reynolds number, thermal conductivity, sources separation distance and the length-to-height ratio of heat sources is investigated. The results indicate that by enhancing the Richardson number from 1 to 10, the heat transfer from the source surfaces slightly increases; however, no significant effect is observed on thermal behavior. Increasing Reynolds number modifies heat transfer from sources and has a large effect on the streamlines and isotherms. In Richardson number of 5, for Reynolds number of 5, 50, 100, 150, the Nusselt number is 1.01, 4.50, 14.11 and 22.13, respectively. Furthermore, for a higher sources thermal conductivity, heat transfer increases due to the lower thermal resistance. The increase in average Nusselt number with changing the dimensionless thermal conductivity in the range of 1 ≤ k¯ ≤ 100 is 314%. By examining the length-to-height ratio of heat sources, the results show that heat transfer decreases initially and then increases for higher values of length-to-height ratios. Furthermore, the heat sources separation distance shows a pronounce influence on heat transfer and thermal distribution. Besides, the results show that the effect of nanofluid concentration on average Nusselt number is more significant at low Reynolds number. The increase of average Nusselt number for Reynolds numbers of 5, 80 and 150 is 25%, 15% and 6.5%, respectively.