【摘要】 针对流体热物性参数随温度变化大或存在相变传热的管内流动问题,提出了分布参数研究方法,特点在于边界条件、物性参数、传热和阻力计算准则式等参数都实现了局部化,能够得到管内流动更加真实准确的传热和热力学特性,并以焓方程代替温度方程,统一了相变与非相变情况下的计算。以充分发展的空气圆管层流流动为例,与解析解的结果进行了对比,验证了分布参数模型的正确性。着重分析了热物性随温度变化较大的丙三醇以及湿空气中有相变发生时的管内流动的传热特性和熵产特性。本文模型不仅对研究管内流动的基本科学问题很有意义,也是研究换热器分布参数模型的基础。更多还原

【Abstract】 The distributed parameter model(DPM)of internal flow was presented for the cases,where large temperature variation or phase change existed.In this model the boundary conditions,thermo-physical properties,heat transfer and friction correlations all used the local values.By replacing the temperature equation with enthalpy equation in DPM,the governing equation could be unified for both single phase and phase change conditions.Hence,the more precise results of heat transfer and thermodynamics for internal flow could be obtained easily.The result of DPM agreed well with the analytic solution of fully developed laminar internal flow of air.On the basis of DPM,the characteristics of temperature and entropy generation were calculated for glycerol with great change of thermo-physical properties and humid air with phase change.This study is very important not only for the basic research of internal flow but also for the 3D DPM of the heat exchanger.更多还原