Thermal Circuit Modeling and Numerical Verification for Concurrent Fluid Flows through an Iso-Flux Heated Concentric Double Tube

Enhancing convection heat transfer performance of internal flows have been a subject of interest relevant to thermal engineering applications. The present study aims to elucidate, via a novel thermal circuit modeling, the heat flow paths and the heat transport mechanisms of thermally developing forced convection of concurrent fluid flows through the outer annulus and inner tube of an externally iso-flux heated concentric double tube, which was demonstrated as an effective heat transfer enhancement configuration with respect to its parent single tube under identical operation conditions, including the inlet fluid temperature, the total volumetric flow rate, the length of heated section, as well as the wall heat flux imposed. To examine the validity of the model developed, corresponding numerical simulations based on the finite volume method were conducted to evaluate the local thermal resistance relationships. The resulting local total thermal resistance fully demonstrated the local convective effect of the fluid flows in managing the heated wall temperature at the outer-ring wall, from which the local heated wall temperature can be readily evaluated from the given imposed heat flux and the inlet fluid temperature.