Title: Reducing entropy generation by volumetric heat transfer in a supersonic two-phase steam flow in a Laval nozzle

Authors: M.R. Mahpeykar, A.R. Teymourtash, E. Amiri Rad

Addresses: Department of Mechanical Engineering, Ferdowsi University of Mashhad, P.O. Box 91779-48944, Mashhad, Iran. ' Department of Mechanical Engineering, Ferdowsi University of Mashhad, P.O. Box 91779-48944, Mashhad, Iran. ' Ferdowsi University of Mashhad, P.O. Box 91779-48944, Mashhad, Iran

Abstract: In a supersonic flow of pure vapour in adiabatic diffusers, under some circumstances, nucleation phenomenon occurs and consequently vapour condensation is observed. In this process, the resulted pressure rise is called the condensation shock, which causes the entropy generation. The innovation of this research is analytically modelling the volumetric heat addition to the steam flow in a 1D convergent–divergent supersonic nozzle. The analysis of the results shows that an appropriate volumetric heat addition to the convergent section of a convergent–divergent supersonic nozzle can reduce the degree of supercooling and subsequently reduce the nucleation rates significantly. The condensation reduction declines the irreversible internal heat transfer, which improves the efficiency of the steam flow.

Keywords: condensation rate; Laval nozzles; nucleation; volumetric heat transfer; two-phase flow; supercooling; condensing flow; supersonic flow; pure vapour; adiabatic diffusers; nucleation; vapour condensation; condensation shock; entropy generation; modelling.

DOI: 10.1504/IJEX.2011.041428

International Journal of Exergy, 2011 Vol.9 No.1, pp.21 - 39

Received: 23 Aug 2010
Accepted: 05 Dec 2010
Published online: 22 Jul 2011 *

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