Fluid Flow and Heat Transfer Characteristics for a Corrugated Duct

对低雷诺数流体在尖角波纹管中的流动进行了压降测量和流动显示。流体流动的雷诺数范围为40 ~ 2000。用珍珠草作为示踪剂进行流动可视化。由此得到了管道内流体流动的临界雷诺数和摩擦系数与雷诺数的关系式。这些结果发表在日本第26届传热研讨会上。实验采用波纹角为30度和45度的两种管道进行。30度和45度管道波纹循环次数分别为19.5次和25.5次。两管波纹标高均为10mm。风管的通道高度分别为5、10和15mm。结果表明：(1)30度波纹管和45度波纹管的临界雷诺数分别为100 ~ 210和60 ~ 220。(2)低雷诺数流体流动时的摩擦因数与层流假设下的数值计算结果一致。对低雷诺数流体进行了传质实验。雷诺数范围为200 ~ 550。采用萘升华法测定了传质系数。波纹角为30度，一个周期的长度为20mm，风管的通道高度为10mm。瓦楞循环总次数为13.5次。风管的宽度为110纳米。因此，风管截面的纵横比为11。结果表明：(1)周期完全发育区域的平均传质系数与层流假设下的数值计算结果吻合。(2)低雷诺数流体流动湍流度对换热的影响相对较小。

Measurements for the pressure drop and the flow visualization were done for low Reynolds number fluid flow in corrugated ducts with sharp edge corners. The Reynolds number of the fluid flow ranges from 40 to 2000. The pearl graze was used for the flow visualization as a tracer. The critical Reynolds numbers and correlations for the friction factor and the Reynolds number for the fluid flow in the ducts were obtained from these results. These results were presented at the 26th Heat Transfer Symposium in Japan. The experiments were done for two ducts with the corrugation angle of 30 and 45 degrees. The total numbers of corrugation cycle were 19.5 and 25.5 for 30 and 45 degree ducts, respectively. The elevation of the corrugation is 10 mm for both ducts. The channel height of the ducts were 5, 10 and 15 mm. The following results were obtained: (1) The critical Reynolds numbers range from 100 to 210 and 60 to 220 for the ducts of 30 and 45 degree corrugation angles, respectively. (2) The friction factor for low Reynolds number fluid flow coincides with the value which is obtained by numerical computation with the assumption of laminar flow.The experiments for the mass transfer were done for low Reynolds number fluid flow. The Reynolds number ranges from 200 to 550. The naphthalene sublimation technique was used for measurement of the mass transfer coefficient. The corrugation angle is 30 degree, the length of one cycle is 20 mm, and the channel height of the duct is 10 mm. The total number of corrugation cycle is 13.5. the width of the duct is 110 nm. As the consequence, the aspect ratio of the cross section of the duct is 11. The following results were obtained: (1) The mean mass transfer coefficient in the periodically fully developed region coincides with the value which is obtained by the numerical computation with the assumption of laminar flow. (2) The effect of the turbulence of the low Reynolds number fluid flow to heat transfer is relatively small.