波节换热管内纳米流体传热与流动实验研究

Experimental Study on Heat Transfer and Flow of Nanofluids in Corrugated Tube

针对波节换热管内纳米流体的传热与流动特性进行实验研究,使用“两步法”制备了均匀稳定的SiO2纳米流体,并定量分析了强化换热的机理。结果表明:在相同工况下随着管内纳米流体质量流量qm的增大,换热器总传热系数K和管程进出口压力损失Δp逐渐增大;由于壁面结构的扰动作用,波节高度H的增大增强了流体的换热能力与流动阻力,波节间距S的增大削弱了流体换热能力与流动阻力。尺寸为H=3.5 mm、S=25 mm、管程内径Dt=25 mm的波节换热管内纳米流体综合换热因子η达到最大,是相同工况下光滑换热管内纳米流体的1.4~2.2倍。

The heat transfer and flow characteristics of nanofluids in corrugated tube were experimentally studied.The uniform and stable SiO2 nanofluids were prepared by two-step method,and the principle of enhanced heat transfer was analyzed quantitatively.The results show that under the same conditions,with the increase of nanofluid mass flow rate qm in corrugated tube,the total heat transfer coefficient K and the tube side inlet and outlet pressure lossΔp gradually increase;due to the disturbance of wall structure,the increase of corrugation height H enhances the fluid heat transfer capacity and flow resistance,while the increase of corrugation spacing S weakens the fluid heat transfer capacity and flow resistance.The comprehensive heat transfer factorηof nanofluid in corrugated tube with H of 3.5 mm,S of 25 mm and inner diameter Dt of 25mm reaches the maximum,which is 1.4 to 2.2 times that of nanofluid in smooth heat exchange tube under the same working conditions.