对流换热可控温差场分布原则

Distribution principle of temperature-difference field controlled for convection heat transfer system

应用火积概念导出了对流换热过程的火积耗散表达式,进一步基于火积耗散极值原理讨论了换热器N股冷、热流在不同情况下参与换热的优化。研究表明,若参与换热的任何冷、热流之间的温差可以独立调控,在总换热量一定寻求火积耗散最小或在总火积耗散一定的条件下寻求换热量最大,则整个换热系统冷、热流之间的温差分布均匀时换热最优;若参与换热的任何冷、热流体之间的换热量或火积损耗可独立确定,则换热冷热流之间的温差分别保持各自的均匀温差分布时换热最优;若在任何冷、热流之间存在可能换热的情况下,无论是总换热量一定时寻求火积耗散最小,还是总火积耗散一定时寻求换热量最大,整个换热系统不同的冷热流换热的优化温差并不是同一个常数。

The entransy dissipation expression for a convection heat transfer process was derived by applying entransy conception,and the heat transfer optimizations for N-stream heat exchangers were investigated at different conditions by applying entransy dissipation extremum principle.The results show that the temperature-difference field between the hot and cold fluids is uniform if the entransy dissipation reaches a minimum for a given total heat duty or if the total heat duty reaches a maximum for a given total entransy dissipation on condition that any temperature-difference between hot and cold fluids involved in heat transfer can be controlled independently,that the temperature-difference field between the hot and cold fluids maintain its own uniformity if any heat duty or entransy dissipation between hot and cold fluids involved in heat transfer is given independently,and that the optimum temperature difference between the different hot and cold fluids maintain different uniformity whether the entransy dissipation reaches a minimum for a given total heat duty or the total heat duty reaches a maximum for a given total entransy dissipation when heat transfer exists within any possible hot and cold fluids.