Second law analysis and optimization for film-wise condensation from downward flowing vapors onto a sphere

Abstract

The present study performs entropy generation analysis and optimization for saturated vapor flowing slowly onto and condensed on an isothermal sphere. This analysis makes us understand the function of the entropy generation and optimization in film-wise condensation outside a sphere. The result demonstrates that entropy generation increases with both group Rayleigh and Brinkman numbers. The minimum entropy generation number in condensation heat transfer for optimal diameter (D) or optimal (Ra/Ja) is expressed in terms of the group Brinkman number. The result provides an immediate estimate of the relative increase in irreversibility associated with using a sphere of diameter (D) ≠ optimal diameter (D).