热流体力学及其应用

热流体力学是一门涉及传热学、流体力学和热力学的交叉学科,并把重点放在讨论热过程对流体流动的影响。它由5部分组成:①热阻力。在某些情况下热阻力的存在对通道中的流体流量和换热系数有重大影响。借助于热阻力系数的定义和分析表达式,不仅可以预示单相通道流中的压力降,而且能用简便的方法预示气-液两相通道流中的压力降和临界热流。②热绕流。运用“虚质量源”和“热偶极子”的概念,对热绕流现象进行了分析和数值研究。它可在热除尘、粒子样品收集和热设备中流量分配等方面获得广泛的应用。③热驱动。不仅在重力场中,而且在如离心力场、表面张力场和电磁力场中也存在着热驱动流。着重讨论了流体运动的起因及其带来的后果,它包括环境污染、传热强化和同位素分离系数的提高等,④热不稳定性。重点讨论了热不稳定性的物理机理。用各种动力学方法所得到的流动不稳定性的临界准则对材料加工、热减阻、水源热污染等都是十分重要的。⑤热优化。研究了基于熵产生最小(热力学第二定律)为目标函数的流动和传热过程的优化。探讨了在一定条件下热力学第一定律效率和第二定律效率的内在联系。

THERMOFLUID DYNAMICS AND ITS APPLICATIONS

Thermofluid Dynamics is a cross-discipline related to heat transfer, thermodynamics, and fluid dynamics with emphasis on the effect of thermal process on fluid flow. It consists of four parts:(1) Thermal Drag. In some cases this may strongly influence flow properties, such as mass flow rate, and heat transfer etc. From its definition and the analytical expression of the thermal drag coefficient, it is possible to predict the pressure drop and the critical heat flux of single phase gas flow and gas-liquid two-phase flow in channel under heating in a very simple way ; (2)Thermal Roundabout Flow. This is describee! analytically and numerically using the concept of "false source" and "thermal dipolc" . Their applications cover the dust remover, particle collector and control of mass flow distribution in thermal devices; (3) Thermal Drive, which can appear in miscellaneous force fields,for instance, centrifugal forces and surface tensions as well as the gravitational field. The origin of the flow and the consequent effects including the heat transfer enhancement, environmental pollution and increase in isotope separation cffciency arc emphasized; (4) Thermal Instability. Its physical mechanism is discussed. Various dynamic approaches arc used to obtain the critical criterion of instability which is important for material processing, drag reduction and thermal pollution of water sources.