WHATS NEW IN CONVECTIVE HEAT-TRANSFER

This paper describes the quest for invariant descriptors of the convec tive process, and the new requirements those descriptors put on quanti tative full-field thermal imaging. There is increasing need, in applic ations, for heat transfer descriptors which can deal with non-uniform thermal boundary conditions, including those induced by conjugate effe cts. This paper discusses two approaches which have arisen within the past 10 years:(1) the use of h(adiabatic) and T-adiabatic to describe the convective process and more recently, (2) the emergence of discret ized Green's functions for convection. Both of these approaches acknow ledge the effects of upstream heat transfer on local behavior but both do so using coefficients which; themselves, are invariant with respec t to changes in the thermal boundary conditions. Thus measurements mad e in the lab can be applied in the field, under different thermal boun dary conditions. Both approaches can:be used in complex flow fields, s uch as flows on surfaces with obstructions. To realize the full potent ial of either approach, the uncertainties in full-field optical data a cquistion techniques must be reduced by about a factor of 3. (C) 1998 Elsevier Science Inc. All rights reserved.