OPTIMAL SYNTHESIS OF HEAT EXCHANGE SYSTEMS

A region of physical realizability of two- and multifl ow heat transfer has been constructed in the space of thermodynamic indicators: heat load, energy dissipation, and thermal conductivity coeffi cient. The boundary of this region is achievable in a counterfl ow displacement heat exchanger, provided the conditions placed on the fl ows′ heat capacities are observed. Using the concept of thermodynamic equivalence of a two-fl ow heat exchanger and a multifl ow system, the requirements for an optimal heat exchange system have been formulated. It is shown that the dependencies of the cold and hot fl ows′ temperatures on the heat load in an equivalent heat exchanger constructed using the suggested algorithm determine the total number of two-fl ow cells in the system, their heat loads, the heat transfer coeffi cients, entropy production, and the structure of the contacts. In this case, each hot fl ow in an optimal system can be in contact with several cold ones, and each cold fl ow can contact several hot ones. Cases of fl ow state phase variation have been considered. Limitations placed on the temperatures of all or part of the fl ows at the inlet and outlet of a heat exchange system have been taken into account. An algorithm has been suggested for selecting free parameters of fl ows, their heat capacities, boundary temperatures, and distribution of contact surfaces.
A region of physical realizability of two- and multifl ow heat transfer has been constructed in the space of thermodynamic indicators: heat load, energy dissipation, and thermal conductivity coeffi cient. The boundary of this region is achievable in a counterfl ow displacement heat exchanger, provided the conditions placed on the fl ows′ heat capacities are observed. Using the concept of thermodynamic equivalence of a two-fl ow heat exchanger and a multifl ow system, the requirements for an optimal heat exchange system have been formulated. It is shown that the dependencies of the cold and hot fl ows′ temperatures on the heat load in an equivalent heat exchanger constructed using the suggested algorithm determine the total number of two-fl ow cells in the system, their heat loads, the heat transfer coeffi cients, entropy production, and the structure of the contacts. In this case, each hot fl ow in an optimal system can be in contact with several cold ones, and each cold fl ow can contact several hot ones. Cases of fl ow state phase variation have been considered. Limitations placed on the temperatures of all or part of the fl ows at the inlet and outlet of a heat exchange system have been taken into account. An algorithm has been suggested for selecting free parameters of fl ows, their heat capacities, boundary temperatures, and distribution of contact surfaces.
Author:  A. M. Tsirlin
Keywords:  two- and multifl ow heat exchange, heat load, energy dissipation, thermal conductivity coeffi cient, optimal heat exchange system, exergy, entropy
Page:  287