摘要
高压加热器为火电机组回热系统的主要换热设备,其换热过程的优劣直接影响火电机组回热系统的热经济性。基于热力学第二定律,为动态分析高压加热器内换热过程优劣,利用(火积)耗散理论,从传热效率的方向建立了高压加热器过热段(火积)平衡方程,推导出了高压加热器过热段(火积)耗散的计算方法。以某高压加热器的过热段为例,得到了高压加热器过热段的(火积)耗散分布规律,计算结果表明:对冷热流体进出口参数固定、对流换热系数为常数的高压加热器,总(火积)耗散为管长的单调函数;(火积)耗散量的增长速度取决于温度梯度的大小,即(火积)耗散理论与温差均匀性理论的一致;高压加热器内流动阻力引起的(火积)耗散对总(火积)耗散影响较小。
High pressure is the main heat exchange equipment of heat recovery system in thermal power unit , and the quality of its heat transfer process directly affects the thermal efficiency of heat recovery system in thermal power unit. Based on the second law of thermodynamics, in order to dynamically analyze the thermal process in high pres- sure heater, entransy balance equations and the calculation method for the superheating section in high-pressure heater are developed in this paper with entransy dissipation theory. Then taking the superheating section of certain high-pressure heater as an example, entransy dissipation distribution of the superheating section of high-pressure heating is calculated. The results show that the total entransy dissipation is a monotonic function of the tube length in high pressure hearter with the import and export of hot and cold fluid parameters being fixed and the convective heat transfer coefficient being constant ; the growth of entransy dissipation depends on the value of the temperature gradient, that is the entransy dissipation theory being consistent with the uniformity of the temperature difference theory; the impact of entransy dissipation caused by flow resistance weaker entransy dissipation is weaker in high- pressure heater.
出处
《电力科学与工程》
2015年第1期5-9,共5页
Electric Power Science and Engineering
关键词
(火积)耗散
高压加热器
温差均匀
entransy dissipation
high-pressure heater
uniform temperature difference
