Conjugate heat transfer: Some fundamentals and recent progress

Abstract

For convective heat transfer, the fluid-domain based decoupled approach has been well established and widely applied for a long time. In this approach, the convective heat transfer coefficient is solved from the perspective of the fluid, without consideration of conductive heat transfer within the solid object. Fluid-solid coupled conjugate heat transfer (CHT), a seemingly more complete approach with higher fidelity, though computationally more involved, has also been continuously developed and applied in past decades. With CHT, the heat transfer at the interface between the fluid and the solid is determined holistically, with both internal conduction and external convection combined together. It is rather noteworthy however that there is a lack of discussion on the role of the CHT: when should CHT be applied and why and how should it be applied? These issues seem to be intrinsically linked to other questions such as when, why and how would the convectional fluid-only decoupled approach be limited? In this chapter, we will start with a brief introduction to the general background of the conventional heat transfer coefficient based decoupled approach and its underlying wisdom. Then we will carry out a more systematic analysis and discussion on the theoretical bases underpinning the conventional approach. Particular attention will be paid to two contrasting theoretical regimes: a linear fluid flow system and a nonlinear one. It is shown that the validity and applicability of the conventional HTC based approach will be challenged in the two regimes in different ways respectively, also with different implications within the context of CHT and beyond. Then we will look at the specific physical and numerical modeling challenges arising from the time scale disparity, and how it may impact our solution capability for time-dependent CHT problems. Some recent progress will be presented in addressing the challenging issues with a new multiscale modeling strategy, particularly for CHT methods with scale-resolving Large Eddy Simulation (LES) turbulent flow solutions.