TEMPERATURE FIELD AND DEFINITION OF SERVICEABILITY OF THE MULTI-FLOW COUNTER-CURRENT HEAT EXCHANGER WITH CHANGES OF PHASE IN STREAMS

Abstract

The method of a numerical integration of the heat transfer differential equations is applied to the multi-flow counter-current heat exchanger at presence of boiling or condensation in streams. The method is applied to the 11 streams heat exchanger. The processes of boiling or condensation occur in 3 streams. Calculations are carried out for alternatives of the heat exchanger with a modification of a surface in 20 times. At conducting calculations the cases of computing unstability and divergency have been detected. Unstability of computing process increases with decrease of a temperature difference between streams. The concept of incomplete temperature recuperation with reference to multi-flow heat exchangers is surveyed. Necessity of an estimation of incomplete recuperation by thermal effect of underheating of inverse streams is shown. The effective method of definition of serviceability of the multi-flow counter-current heat exchanger is offered by comparison of an amount of the heat which have been given up by direct streams at cooling up to some temperature, with the heat received by inverse streams at heating from the same temperature. The method is founded on a strict thermodynamic rule about conditions of limiting serviceability of heat exchangers. The method can be used for check of an admissibility of initial parameters at a stage of development of the technical project.