Applicability of entransy dissipation based thermal resistance for design optimization of two-phase heat exchangers

• The liquid–vapor two-phase entransy is derived and applied to two-phase heat exchanger optimization studies.
• Real case studies to optimize a fin-tube condenser and a microchannel condenser are presented.
• Entransy metric has no advantage over capacity as optimization objective if flow rates are fixed.
• Entransy metric could be used to optimize air flow rate together with heat transfer area.
• In air cooled two-phase HXs, entransy metric and entropy metric show little difference in optimization results.

Recently, entransy dissipation theory showed its potential applicability in heat exchanger design optimization. Physical definition of two-phase entransy is presented in this study to extend its application to heating, ventilation, air conditioning and refrigeration systems. In this study, the evaluation of two-phase entransy is achieved by optimizing one tube-fin heat exchanger and one microchannel heat exchanger based on a validated heat exchanger modeling tool. Based on analytical approach and optimization results, the applicability and necessity of using entransy dissipation based thermal resistance are discussed. It has been proven that the entransy dissipation is an effective way to optimize heat exchangers with air flow rate as one design variable but has its limitation for optimizing heat exchangers with fixed flow rate.