Article,
Principle of equipartition of entransy dissipation for heat exchanger design
SCIENCE CHINA Technological Sciences, (2010)
DOI: 10.1007/s11431-010-0128-y
Abstract
In the present work, a principle of equipartition of entransy dissipation (EoED) for heat exchanger design is established, which says that for a heat exchanger design with given heat duty and heat transfer area, the total entransy dissipation rate reaches the minimum when the local entransy dissipation rate is uniformly distributed along the heat exchanger. When the heat transfer coefficient is unfixed, the total entransy dissipation obtained by the EoED principle is less than that obtained by the principle of equipartition of temperature difference (EoTD). Furthermore, the exchanger effectiveness obtained by the EoED principle is larger than that obtained by the EoTD principle. When the heat transfer coefficient is fixed, the EoED principle is equivalent to the EoTD principle. We show that the equipartition of entropy production (EoEP) and EoED principles give rise to difference in entropy generation and entransy dissipation for a heat exchanger optimization design. The discrepancies are caused by distinct features of entropy production minimization and entransy dissipation minimization principles, the former is to optimize the design of heat exchanger by making the lost available work minimum, while the latter is not involved with heat-work conversion. It is found that the entropy generation number is not suitable for evaluating heat exchanger performance, since it directly depends on the inlet and outlet temperatures of working fluids. On the contrary, the entransy dissipation number is not directly related to the inlet and outlet temperatures of working fluids. Therefore, the entransy dissipation number is more suitable for serving as a criterion to evaluate heat exchanger performance.
