Conference Year

2012

Keywords

entrasy dissipation, entropy generation, heat exchanger, optimization

Abstract

Several techniques and metrics based on the Second Law of Thermodynamics have been used in the past for the analysis of heat exchangers. The terms used for these techniques include irreversibility analysis, entropy generation minimization, exergy analysis and thermodynamic efficiency. Entransy is a recently developed concept reflecting the heat transfer potential, rather than the ability to convert heat to work. Entransy is transferred along with heat flux in the heat transfer process, and subsequently dissipates. The entransy dissipation extremum principle is applicable to heat transfer enhancement. Entropy on the other hand is a thermodynamic state-based quantity. This study focuses on the comparison of entransy dissipation and entropy generation units in the context of optimizing the widely used fin-tube heat exchanger. Local entransy balance equations are established and implemented in a finite-volume based fin-tube heat exchanger model. The model can then calculate the entransy dissipation in each control volume, as well as the total dissipation for the entire heat exchanger. Parametric study about two heat exchangers, one undergoing only single phase heat transfer (water coil) and the other undergoing both single phase and two-phase heat transfer (R134a evaporator) are conducted without water condensation on the air side.

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