The effect of baffles on vertical wall PCM to enhance natural convection

Abstract

The objective of this study is to enhance convective heat transfer within phase change materials (PCM) using baffles on a vertical wall. PCMs have major drawbacks of low thermal conductivity, high viscosity, and limited natural convection. To address these issues, we investigated a passive approach to enhance natural convection with baffles. The new approach is to arrange multiple baffles with gaps on the opposite side of the heated vertical wall. This placement can minimize vertical temperature difference by blending upward-flowing hot liquid PCM with downward-flowing cold liquid PCM across the gaps and also increase circulating velocity by shortening path of circulation cell through sections divided by baffles. Visualization experiments of shadowgraphy and particle image velocimetry (PIV) were conducted to compare the case with baffle (WB) against the case without baffle (NB). The presence of the baffles lowered the average temperature difference in the horizontal direction by 40%. The WB case reduced the temperature difference in the vertical direction by 50%, compared with the NB case. Furthermore, comparison of the WB with NB showed that at the heat power levels of (4, 6, and 8) W, the convection coefficient increased by up to (28, 34, and 27)%, respectively. Therefore, by changing the internal flow pattern, the baffles on the vertical wall improved convective heat transfer performance.