插入物强化管内单相流体传热的研究

为寻求强化低Re数下气体传热的较好插入物型式,在Re=500-10000范围内,对6种插入物用氢气泡示踪法进行流态显示,在恒壁温条件下进行竖直管内空气传热和阻力对比试验,得出各插入物的f-Re和Nu-Re关联式,并对各插入物进行传热强化性能评价.在此基础上进行参数范围为e/D=0.067—0.234、S/e=3.89—13.25的螺旋片试验,得出其阻力和传热关联式.综合研究流态显示结果和传热性能评价,认为在层流或过渡流区,利用螺旋流与利用边界层分离二者相比较,前者可以耗能较少而获得同样的传热强化效果.

An Investigation on Augmentation of Single Phase Heat Transfer in Tube by Means of Inserts

In order to find out the better types of inserts in tubes for augmentation of heat transfer of gases in the lower Reynolds number range, flow visualization by means of hydrogen bubble technique and comparative tests of the friction drag and heat transfer of air in vertical tubes with uniform wall temperature were made. Six types of inserts were studied in the region of Reynolds numbers from 500 to 10,000. The f-Re and Nu-Re correlations of various inserts under the test condition were obtained. The heat transfer augmentation performance of these types of inserts was evaluated. On this basis, friction drag and heat transfer characteristics of the helical ribbon were investigated experimentally. The friction drag and heat transfer correlations of this kind of insert with e/d from 0.067 to 0.234 and S/e from 3.89 to 13.25 were obtained. Combining the results of the flow visualization with the performance of heat transfer augmentation, it was suggested that the spiral flow consumes less energy than the boundary layer separation to produce the same heat transfer augmentation in the laminar or transitional range.