水平旋转圆筒表面对流传热和传质实验

采用微热偶式测温和测湿技术,分别对大直径水平旋转圆筒表面对流传热和传质特性进行了对比实验研究.实验数据验证了在圆筒表面对流传热和传质之间存在着良好的可类比性,即旋转对圆筒表面对流传热边界层温度场分布和局部努塞尔数的影响规律与旋转对传质边界层浓度场分布和局部舍伍得数的影响规律相似,但顺向侧和逆向侧之间存在着明显的差异;旋转对圆筒表面平均传热努塞尔数数和平均传质舍伍得数的影响规律也相似,都存在临界雷诺数.当旋转雷诺数小于或等于临界雷诺数时,平均努塞尔数和平均舍伍得数随旋转雷诺数的变化基本保持不变;当旋转雷诺数大于临界雷诺数时,平均努塞尔数和平均舍伍得数随旋转雷诺数的增大而增大.实验中还发现,由于传热和传质的边界层条件不同,热质交换共存时的临界雷诺数小于纯对流传热时的临界雷诺数.

Experimental investigation of heat and mass transfer from horizontal rotating cylinders

Heat and mass transfer characteristics from a large diameter horizontal rotating cylinder has been investigated systemically by suing the temperature and concentration measurement instruments.The analogy between the convective heat and mass transfer is validated directly by the experimental data.The results indicate that the effect of rotation on the temperature distribution and local Nusselt number is similar to that on the concentration distribution and local Sherwood number,but there is a obvious difference between the downstream side and upstream side.There is a similar behavior between the variation of average Nusselt with rotational Reynolds number and the variation of average Sherwood number with rotational Reynolds number,i.e.,they both have a critical Reynolds number.When the rotational Reynolds number is lower than critical Reynolds number,the average number and the average Sherwood number are independent of rotational Reynolds number,when the rotational Reynolds number is larger than critical Reynolds number,the average Nusselt number and the average Sherwood number increase with increasing rotational Reynolds number.Because of the different conditions between the heat and mass transfer,the measured combined heat and mass transfer critical Reynolds number is lower than that of the pure heat transfer.