Lower Entropy Generation in Microchannels With Laminar Single Phase Flow

Abstract

In this study the entropy generation minimization method is used to find the optimum channel dimensions in micro heat exchangers with a uniform heat flux. With this approach, pressure drop and heat transfer in the micro channels are considered simultaneously during the optimization analysis. A computational model is developed to find the optimum channel depth knowing other channel geometry dimensions and coolant inlet properties. The flow is assumed laminar and both hydrodynamically and thermally fully developed and incompressible. However, to take into account the effect of the developing length in the friction losses, the Hagenbach’s factor is introduced. The micro channels are assumed to have an isothermal or isoflux boundary condition, non-slip flow, and fluid properties have dependency on temperature accordingly. For these particular case studies, the pressure drop and heat transfer coefficient for the isoflux boundary condition is higher than the isothermal case. Higher heat transfer coefficient and pressure drop were found when the channel size decreased. The optimum channel geometry that minimizes the entropy generation rate tends to be a deep, narrow channel.

Entropy generation analysis due to heat transfer and nanofluid flow through microchannels: a review

“…The increase in the rarefaction results in HT loss whereas decrease in the AR results in the improvement in the HT. Galvis and Culham (2011) analysed the EG in a micro heat exchanger to find the optimum channel dimension by developing a computational domain. Thermal EGR increases with an increase in the channel width but EGR was found to be minimum corresponding to optimum channel AR.…”