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首页> 外文期刊>International Journal of Heat and Mass Transfer >Convection heat transfer in concentric micro annular tubes with constant wall temperature
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Convection heat transfer in concentric micro annular tubes with constant wall temperature

机译：壁温恒定的同心微环形管中的对流传热

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摘要

Heat transfer characteristics of gaseous flows in concentric micro annular tubes with constant wall temperature whose temperature is lower or higher than the inlet temperature were numerically investigated. The slip velocity, temperature jump and shear stress work were considered on the slip boundary. The numerical methodology was based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The computations were performed for two thermal cases. This is, the wall temperature was constant at the outer wall and inner wall was adiabatic (Case t) and the wall temperature was constant at the inner wall and the outer wall was adiabatic (Case ii). The stagnation temperature was fixed at 300 K and the computations were done for the wall temperature which ranges from 250 K to 350 K. The outer tube radius ranged from 20 to 150 urn with the radius ratio 0.02,0.05,0.1, 0.25 and 0.5 and the ratio of length to hydraulic diameter was 100. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1 to 0.8. The outlet pressure was fixed at the atmospheric pressure. The heat transfer characteristics in concentric micro annular tubes were obtained. The bulk temperature and the total temperature are compared with those of both cooled and heated cases and also compared with those of the simultaneously developing incompressible flow obtained by SIMPLE algorithm. The results show that the compressible slip flow static bulk temperature along the length is different from that of incompressible flow. Therefore heat transfer characteristics of the gaseous flow are different from those of the liquid flow and also have different trends whether the wall temperature is lower or higher than the inlet temperature. A correlation for the prediction of the heat transfer rate of gas slip flow in concentric micro annular tubes is proposed.
机译：数值研究了壁温恒定或低于入口温度的同心微环形管中气流的传热特性。在滑移边界上考虑了滑移速度，温度跃变和切应力功。数值方法基于任意拉格朗日欧拉（ALE）方法。针对两个热工况进行了计算。即，外壁的壁温度恒定，内壁是绝热的（情况t），内壁和外壁的壁温度恒定是绝热的（情况ii）。停滞温度固定为300 K，壁温度范围为250 K至350K。外管半径为20至150 urn，半径比为0.02、0.05、0.1、0.25和0.5，以及长度与水力直径之比为100。停滞压力的选择应使出口马赫数在0.1至0.8的范围内。出口压力固定在大气压。获得了同心微环形管的传热特性。将整体温度和总温度与冷却和加热情况下的温度进行比较，还与通过SIMPLE算法获得的同时发展的不可压缩流的温度进行比较。结果表明，沿长度方向的可压缩滑流静态整体温度与不可压缩流不同。因此，无论壁温低于还是高于入口温度，气流的传热特性都不同于液体的传热特性，并且还具有不同的趋势。提出了一种用于预测同心微环形管中瓦斯流的传热速率的相关性。

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