engleski

Local entropy production of the parallel flow and counterflow heat exchanger

The paper gives an analytical dimensionless analysis of the local entropy generation and its ratio with the local exchanged rate of heat flow for parallel flow and counterflow heat exchangers. The paper includes only the effect of the stream temperatures on the above mentioned values, so it does not observe the effect of the pressure drop on the amount of entropy generation. The end (side)of the heat exchanger, which is the inlet point of the weaker flow, is, among other, proven to be relevant variable for those local values. Elaborated algorithm provides explicit connection between entropy generation and ratio of the entropy generation in dependence on the relevant dimensionless variables. From obtained general equations for parallel flow and counterflow heat exchanger special cases for observed values were extracted, considering the cases where one of the flows condenses or evaporates. Also, expressions for so called balanced counterflow heat exchanger which has both stream flows with equal total heat capacities were derived from obtained equations for counterflow heat exchanger. In addition, a case where both flows undergo a phase change is presented. It is clear that the given algorithm, aside the local amounts of the observed values, also gives overall amounts of the mentioned values, often referred to by many scientific papers. The results are presented by appropriate diagrams and additionally interpreted.

parallel flow and counterflow heat exchanger, local entropy generation, local rate of heat flow, dimensionless analysis

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