A new framework for design and validation of complex heat transfer surfaces based on adjoint optimization and rapid prototyping technologies

Abstract

In order to drastically accelerate the development processes of advanced heat exchangers, a new design framework integrating shape optimization, rapid prototyping and experimental validation is proposed. For the optimal design of heat transfer surfaces, a new adjoint-based shape optimization algorithm taking into account unsteady turbulent transport is developed. The present shape optimization algorithm is applied to two different conventional pin-fin arrays with circular cross sections so as to maximize the analogy factor, i.e., the ratio of heat transfer and pumping power for driving the fluid. The resultant optimal fin shapes are elongated in the streamwise direction and also characterized by bump-like structures formed on the upstream side of the pins. Investigation of numerical results reveals that the pressure drop of the optimal shape is significantly reduced by the suppression of vortex shedding behind the fin, whereas the heat transfer performance is maintained by the extended surface. The optimal shapes are fabricated by a resin-based additive manufacturing technique. A single-blow method allows to evaluate the heat transfer coefficient of low-thermal conductivity materials by measuring the inlet and outlet air temperature only, while the pressure loss is estimated from the pressure measurements at the upstream and downstream of the text matrix by Pitôt-tubes. As a result, significant improvement of thermal hydraulic performance is experimentally confirmed for the optimal pin-fin arrays as predicted by numerical analyses.

Keywords

• shape optimization
• turbulent flow
• heat transfer
• direct numerical simulation
• single blow method