基于网络热力学的热力系统能量流描述

Energy Flow Description of Thermodynamic System Based on Network Thermodynamics

网络热力学起源于热力系统分析,但其广泛应用却是在生命系统等非热系统领域,这是因为网络热力学方法需要从能量的角度分析系统,而热力系统中的热量在输运过程中具有物质属性,因此必须有新的能量形式。若将热量视作"流",而将温度视为"力",那么流与力的乘积就为(火积)流。(火积)具有能量的内涵,(火积)流就可以被视为热力系统的能量流。并且,在能量输运过程中,其他形式的能量如功量也可以视为一种物质。由此,在(火积)流的统一视角下,各种形式的能量在网络中便可得到有机结合。分析结果表明,对于换热系统以及热力系统,基于网络热力学的能量流法也可以表达系统的物理本质。在(火积)流的视角下,能量流键图可以很好地反映热力系统的拓扑结构。例如对于热机-热泵供热联合循环,热机与热泵之间的功量交换过程即使是可逆过程,也会存在(火积)的损失或产生,这从能量流键图中可以被直观地刻画出来。

Network thermodynamics originated from thermodynamic system,but it was widely applied in the non-thermal field such as living system.This is because network thermodynamics analyzes a system from the point of view of energy flow,but the heat in a thermodynamic system presents the material property in transfer process,so new energy forms are needed.If the heat is regarded as"flow"and the temperature is regarded as"force",then the product of flow and force is the entransy flow.Entransy has the meaning of energy and thus the entransy flow can be regarded as the energy flow of thermodynamic system.Moreover,other kinds of energy such as work can be also regarded as the substances in transfer process.As a result,various kinds of energy are organically combined in the same one network system under the unified perspective of the entransy flow.The analysis show that the energy flow method based on network thermodynamics can express the physical nature of the purely heat-transfer system as well as the thermodynamic system with heat-work conversion.The bond graph of the entransy flow gives a good representation of the system topology property.For example,for a combined cycle of heat engine and heat pump,there is a loss or generation of entransy in the energy-exchange process even if it is reversible,which can be visually expressed from the bond graph of energy flow.