传热强化管管内熵产分析与热力性能评价

Entropy Generation Analysis and Thermal Performance Evaluation of Internally Heat Transfer Enhanced Tubes

根据热力学第二定律,对传热强化管管内热力过程进行熵产分析,建立了基于流动与传热过程熵增原理的管内传热熵产方程,导出恒热流和恒壁温2种常见工况下的无因次熵产数表达式。在不同雷诺数和进口温差条件下,对2种螺旋槽管和光管进行恒壁温工况的熵产分析和热力性能评价,分析了传热和流动摩阻引起的熵产变化规律及2种不可逆损失占总熵产的份额。结果表明,熵产分析可用于评价传热强化管的综合热力性能,确定合理的运行工况、结构参数及强化换热形式,为强化管的应用评估及优化设计提供参考。

Entropy generation during heat transfer, within internally enhanced tubes, has been analyzed, on the basis of the second law of thermodynamics, and an entropy generation equation has been derived, based on the theory of entropy increase during flow and heat transfer, as well as a dimensionless expressions of generated entropy during often met constant heat flux or constant wall temperature conditions. Entropy generation analysis and thermal performance evaluations, under constant wall temperature conditions, of internally rifled tubes and also of smooth tubes, for various Reynolds＇ number and different inlet temperatures, have been performed, accompanied by a discussion concerning entropy variations originating from heat transfer, as well as caused by flow resistance, and concerning the percentage each makes of the total. Results indicate that the thermal performance of heat transfer enhanced tubes may be comprehensively evaluated by entropy analyses and applied to choosing of proper ways of heat transfer enhancements, herewith serving as a reference for comprehensively evaluating the application of enhanced tubes and for optimizing designs.