Dependence of heat transfer and pressure drop on arc diameter of internal ring-type ribs in circular tube

• Main Authors: Yu-Wei Gong, 龔育威
• Other Authors: 沈君洋
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/71135073157494038375

碩士 === 國立中興大學 === 機械工程學系所 === 102 === 　　This work investigated the effect of groove diameter (da) of internal ring-type protrusions in circular tubes on the heat transfer and pressure drop. Totally twelve test tubes were tested. Protrusion pitch to tube diameter ratios (p/d) of the test tubes were 0.72, 1.45, and 2.9. Protrusion height to tube diameter ratios (e/d) were 0.043 and 0.069. In addition, three groove diameter to tube diameter ratios (da/d), 0.14, 0.43 and 0.72, were considered. The obtained heat transfer and fluid friction data were compered to those of a smooth tube. Two working fluids, air and water, were individually considered. The Reynolds numbers (Re) were in the range of 3502 to 17850. The result shows that, at the same p/d, e/d and Re values, the Nusselt number (Nu) enhancement index (r1) increases with a decrease of the da/d value, while the Nu/friction factor (f) index (r2) and the heat transfer rate/comsumed mechanical work index (r3) increase with the da/d values. Either air or water, the larger the da/d value, the better the overall heat transfer and pressure drop performance. For air, at p/d=1.45, e/d=0.043 and da/d=0.72, a largest r3 value of 0.62 was found and it occurs at Re=16011. For water, at the same p/d, e/d, and da/d values, the largest r3 valus was 0.53 and it occurs at Re=14215. Comparing the r1, r2, and r3 values shows that the tube with p/d=1.45, e/d=0.043 and da/d=0.72 consumes less mechanical work than the other tubes. Correlation result shows that the Nu and f values are proportional to (da/d)-0.05 and (da/d)-0.13 respectively.