Mixed convection heat transfer and pressure drop of entrance region in an inclined rectangular duct

The short rectangular duct is widely used in the electronic equipment cooling systems because of its high heat transfer coefficients. The present experiment was conducted on an inclined rectangular duct with length to diameter ratio being 15, which was made of aluminum alloy. The influence of Reynolds numbers, Grashof numbers and inclination angles on the heat transfer and pressure drops was investigated. The Reynolds numbers range from 402 to 2750, Grahsof numbers from 2.43x105 to 1.46x106 and inclinations angles from 00 to 600. According to the experimental results, the average Nusselt numbers increase with Reynolds numbers and Grashof numbers, and decreases with inclinations angles. The pressure drops, less than 10 Pa, increase with Reynolds numbers and decreases with inclination angles, but intersect at different Reynolds numbers when Re < 1000. A fitting correlation of the average Nusselt numbers subjected to Reynolds numbers, Grahsof numbers, inclination angles and length to diameter ratio of the rectangular duct was developed according to the experimental results, and the correlation has an accuracy of better than +/- 11.5% from the experimental results. The agreement of average Nusselt numbers from the present experiment and from literature is within +/- 16.7%.