A-4 赤外線放射温度計を用いた過渡応答法によるTeardrop形状ディンプル面の熱伝達率計測(伝熱,一般講演)

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Recently, heat transfer enhancement by using dimpled surfaces has been an attractive topic because of its low pressure loss. In this configuration, flow separation occurs at leading edge of the dimple, and local heat transfer coefficient becomes low there. Chyu et al. proposed teardrop-shaped dimples, having a linear slope at the leading edge of the dimple to prevent the flow separation, and it gave higher heat transfer although pressure lossalso became larger. In this study, modified teardrop-shaped dimple having a curved slope at the leading edge of the dimple was proposed aiming at the smooth fluid entry to the dimple. Using the transient technique with the infrared thermometer, local heat transfer distributions on the dimpled surfaces have been obtained. The cases of smooth surface and surfaces with hemispheric dimples were also measured for comparison. The experiments were performed in the range of 6,000 ≤ Re ≤ 11,000, and the maximum Nusselt number of teardrop-shaped dimple case was 3.6 times higher than that of smooth case.
2008-10-01