Handbook of Turbomachinery Second Edition Revised - Ventech!

After four decades of advancement in numerical analysis and
turbomachinery studies, the state-of-the-art analytical techniques are still
limited in providing an accurate life prediction for the components.
Therefore, experimental calibration and verification of the analysis are
playing a major role in the development cycle. Experimental validation of
the analysis is performed after a design team is satisfied with the concept and
analytical prediction. The section on combustor cooling describes major
elements of experimental validation.
DEFINITION OF MAJOR HEAT- AND MASS TRANSFER
SIMILARITY PARAMETERS
Three distinct heat-transfer phenomena should be considered when turbine
components are analyzed:
1. Heat transfer by conduction
2. Heat transfer by convection
3. Heat transfer by radiation
Radiative heat transfer is often important in the analytical prediction of
combustor liner and stage 1 nozzle vanes facing a combustor liner. Typical
so-called conjugate heat transfer in a turbine component, for example, a
cooled turbine vane, involves a combination of convective external heat
transfer from the hot gas to the vanes, conduction through the wall of the
hollow vane, convective internal heat transfer from the vane to the cooling
air, and possible flame radiation as well as radiative heat transfer from
higher-temperature walls of the liner.
Heat–Mass Transfer Interaction in the Airfoil Boundary Layer
The transfer of heat in a fluid can occur through conduction as well as
advection through the movement of the fluid (it is customary to use term
‘‘convection’’ when referring to cumulative transport by random motion of
molecules and the term ‘‘advection’’ when referring to transport due to bulk
fluid motion). The overall heat transfer combining advection and conduction
in a moving media is usually referred to as convective heat transfer. The
heat and mass transfer defining the temperature and velocity field are closely
coupled and interact, strongly affecting each other. Forced convection plays
the dominant role for most of the turbine components compared to natural
convection. The critical elements in the external heat transfer from the hot
gas to the wall of a blade are the boundary layer developing on the surface
and the free-stream total temperature. The boundary layers, which act as a
Copyright © 2003 Marcel Dekker, Inc.