肋开孔高度对大宽高比矩形通道流动传热的影响 *

Effects of Holes Height on Flow and Heat Transfer in a Ribbed Rectangular Channel with Large Aspect Ratio

关键词:  燃气轮机  矩形通道  实体肋  开孔肋  强化传热

Key words:  Gas turbine  Rectangular channel  Solid rib  Perforated rib  Enhanced heat transfer

摘要:

为了获得大宽高比矩形通道内开孔肋的流动与传热特性，采用数值模拟的方法在开孔肋的肋高e/Dh=0.188、开孔率β=0.131时研究了通道的摩擦系数、努塞尔数等参数随孔排高度和雷诺数的变化规律。结果表明:与实体肋相比，开孔肋能够减小通道的摩擦系数并提高其壁面温度分布的均匀性，但是传热增强因子有所减小；随着孔排高度的提升，通道的摩擦系数单调减小，壁面温度分布的不均匀度增大，而传热增强因子则先增大后减小，因此存在一最优孔排高度(h/e)opt=0.65使开孔肋的强化传热综合指标达到最大值；随着雷诺数的增大，开孔肋通道的摩擦系数缓慢减小、换热逐渐增强，这与实体肋的变化规律是类似的。

Abstract:

Numerical study of flow and heat transfer characteristics in a large aspect ratio rectangular channel with a perforated rib mounted on the bottom surface were performed for the rib height-to-channel hydraulic diameter (e/Dh) and the open area ratio (β) fixed at 0.188 and 0.131 respectively. The effects of non-dimensional holes height (h/e) and entrance flow Reynolds number on the friction factor and Nusselt number of channel were analyzed. The results show that the perforated rib has a lower friction factor and more uniform surface temperature distribution as compared with the solid rib，but its averaged Nusselt number ratio slightly drops. As the holes height elevating，both the friction factor and the temperature field uniformity decrease gradually，while the averaged Nusselt number ratio take on the up-down tendency，so there is an optimal holes height (h/e)opt=0.65 for the thermal performance factor reached its maximum. Similarly to the solid rib，the friction factor slowly decreases and the averaged Nusselt number monotonic increases with the increasing of Reynolds number for the perforated rib.