NUMERICAL INVESTIGATION OF ENHANCING MIXED CONVECTION HEAT TRANSFER BY USING SEMI-CYLINDRICAL OBSTACLES IN A VERTICAL CHANNEL

In this study; effects of mixed convection on heat transfer and flow properties was investigated numerically for a vertical channel which has semi-cylindrical obstacles with heat flux. Effects of distance, location and number of these semi-cylindrical obstacles on heat transfer and flow properties have been examined. The effect of one semi-cylindrical obstacle, two semi-cylindrical obstacles located one under the other and two semi-cylindrical obstacles on opposite sides were investigated in the study. As a result; it is obtained that increasing the ratio of the obstacle diameter to the channel width (BR) causes an increase on heat transfer. Increasing BR ratio from 0.15 to 0.75, depending on the increase of Ri number from 50 to 200 causes an increase of 58.3% on average Nu number. Increasing L/D ratio, which represents the distance between obstacles, causes generally an increase in the average Nu number. Increasing L/D ratio from 0.25 to 1.5 results in an increase of 25.2% on the average Nu number. The highest Nu number can be obtained for L/D = 1 and Ri = 300. For the case of two semi-cylindrical obstacles on opposite sides; it was seen that increasing the BR ratio causes an increase in the average Nu number depending on the increase in the Ri number. Increasing BR ratio from 0.15 to 0.30 yields an increase of 36.3% for a low Ri number (Ri=50) and an increase of 23.1% for a high Ri number (Ri = 200) in the average Nu number. Moreover; it has been shown that numerical results can well represent the temperature distribution and flow properties by comparison of these results with experimental results in the literature.