Entropy generation and exergy destruction in condensing steam flow through turbine blade with surface roughness

Abstract

In the steam turbine, the wetness loss due to vapor condensation is one of the most crucial losses at low-pressure stage. This study focused on entropy generation and exergy destruction of condensing steam flow in turbine blade with the roughness. The governing equations including entropy transport equation combined with condensation model, transition SST model and roughness correlation were established and verified by experiments and theory. Flow field behaviors, such as wetness fraction, intermittency and turbulent viscosity distributions, controlled by the deviation angle were obtained to evaluate effects of back pressure ratio and surface roughness. The mass-averaged wetness fraction at outlet was also extracted considering the influence of uneven mass flux. Finally, each part of entropy generation derived from viscous, heat conduction, phase change and aerodynamic losses and exergy destruction ratio were analyzed.Research shows that roughness plays an important part in the intermittency and turbulent viscosity. The mass-averaged wetness fraction at outlet sharply drops with back pressure ratio but slightly decreases with the roughness. With the roughness rising * at stagnation condition mass generation rate, kgm -3 s -1 * 1

Performance of steam ejector with nonequilibrium condensation for multi-effect distillation with thermal vapour compression (MED-TVC) seawater desalination system

“…Fundamental equations governing the flow features in a steam ejector are compressible Navier-Stokes equations [27][28][29]. Considering the complicated flow structure inside steam ejectors, including the supersonic flow, condensing flow, flow separation and shock waves, the shear stress transport (SST) k-ω turbulence model is employed for performance evaluations of steam ejectors for MED-TVC seawater desalination systems.…”

Optimisation study of a supersonic separator considering nonequilibrium condensation behaviour

“…where ρ is the mixture density, kg m -3 ; u is the mixture velocity, m s -1 ; y is the liquid fraction, dimensionless; n is the droplet number, m -3 ; t is the time, s; J is the nucleation rate, m -3 s -1 ; Г is the mass generation rate due to the nonequilibrium condensation, kg m -3 s -1 , which is given [27,28]:…”

Entropy Analysis of Complete Condensation of Saturated Steam on a Vertical Wall Using Nusselt Velocity and Temperature Profile in a Condensate Layer

“…Esfahani and Modirkhazeni [17] analyse the entropy generation number in forced convection film condensation on a horizontal isothermal elliptical tube. On the other hand, some studies [18] are focused on entropy generation and exergy destruction of condensing steam flow in turbine blade with roughness. Entropy generation and exergy loss of nanofluid refrigerant condensation is experimentally examined in Sheikholeslami et al [19].…”