膜片管通道流动与换热过程的数值模拟

采用SIMPLE算法模拟膜片管通道中的流动与换热,分析流场中出现的非线性现象以及不同管束排列方式对换热的影响。物理模型长度为185. 6 mm,高度为92. 8 mm,圆管直径为32 mm。烟气入口温度为400 K,上下两侧固体壁面温度为300 K。假设流动与换热进入充分发展阶段,雷诺数(Re)的取值范围是3 000～25 000,通入不同流速的烟气与两侧的壁面进行换热。结果表明:采用雷诺应力模型(RSM)所得的努塞尔数(Nu)与实验关联式结果最吻合,而且相对误差在5%～17%间;采用直接模拟(DNS)模拟时,稳态到非稳态的临界Re是100;在同一Re时,随着管间距减小,Nu是逐渐增加的,当Re取为25 000,管束水平间距和竖直间距均取为43. 2 mm时,通道换热能力达到最大且相应的Nu是195. 23。

Numerical Simulation of Fluid Flow and Heat Transfer in Membrane Channel

SIMPLE algorithm is employed to analyze the non linear phenomena and the effect of tube spacing on heat transfer in the membrane channel. The length of the physical model is 185.6 mm,the height of the physical model is 92.8 mm and the diameter of the tube is 32 mm. The given inlet temperature is 400 K and the channel consists of two walls at 300 K . The numerical simulation is then performed based on the assumption that fluid flow and heat transfer are periodically fully developed. Fluid enters from the inlet with different velocities when the Reynolds number is between 3 000 and 25 000. It is concluded that the Nusselt number obtained by the RSM is closer to the experimental results than the results obtained from other turbulent models and the relative error between the simulation results and the experimental results is 5%~17%. The critical Reynolds number obtained by the DNS is 100. At the same Reynolds number,the Nusselt number increases gradually with the decrease of tube spacing,showing better heat transfer characteristics. And the maximum Nusselt number is 195.23 and it appears when the Reynolds number is 25 000 and the transverse and the longitudinal pitches of adjacent circular tubes are 43.2 mm.