换热器系统的能质传递有效度

Exergy Transfer Effectiveness of Heat Exchanger System

基于热力学能质传递理论定义并导出了换热器系统的能质传递有效度计算公式,系统地讨论了传热单元数、冷热流体热容量流率比以及单台换热器的流型对换热器系统能质传递有效度的影响,比较了换热器系统的能质传递有效度与换热器系统的传热有效度。结果表明,对于由多台结构和流型相同的换热器串-并联组合而成的换热系统,当其中的每台换热器为逆流布置时其热力学性能最佳;在相同的情况下,换热器系统的传热有效度总是大于换热器系统的能质传递有效度,且换热器系统的能质传递有效度和换热器系统的传热有效度以及两者之间的差值随传热单元数、冷热流体热容量流率比以及单台换热器的流型的变化呈现不同的规律。

The definition and expression of exergy transfer effectiveness have been obtained for the heat exchanger system based on the exergy transfer theory of thermodynamics. The effects of heat transfer units number, the ratio of cold and hot fluids heat capacity rate and flow patterns of an individual heat exchanger on exergy transfer effectiveness of heat exchanger system were discussed systemically. In addition,the comparisons of exergy transfer effectiveness with heat transfer effectiveness of heat exchanger system were given. The results showed that the thermodynamic performance of series-parallel connected heat exchanger system, which is composed of the same configuration and flow pattern heat exchangers,was optimal when each heat exchanger in system was counter flow,and the heat transfer effectiveness of heat exchanger system was always greater than the exergy transfer effectiveness of heat exchanger system under the same conditions. Furthermore,when the ratio of cold and hot fluids heat capacity rate,heat transfer units number and flow patterns of an individual heat exchanger of heat exchanger system were varied,the exergy transfer effectiveness, heat transfer effectiveness and the difference between them presented different characteristics.