Optimization study of tube bundle in cross-flow for different tube shapes in a boiler
Résumé
A circular tube bundle is one of the simplest geometries and widely used in heat transfer applications, but in the recent years, cross-flow heat exchanger with non-circular tube arrangement is receiving increased attention. The main purpose of this work is to gain insight into the local heat transfer and fluid flow conditions in different tube bundles arrangement: circular, ellipsoidal and wing-shaped, for heat exchangers in boiler. All tube shapes are investigated under similar operating condition. The investigation covers the effects of minor-to-major axis ratios and flow angles of attack. A two-dimensional (2D) numerical CFD model using finite volume discretization was conducted to evaluate the boiler system performance. The results indicated that, for certain tubeshapes, increasing the angle of attack 90° enhance the convective heat transfer coefficient considerably. The overall best thermal performance was seen in the elliptic tube heat exchanger and it was qualified with the lower axis ratio and angle of attack. Thus, we can propose elliptic tubes for heat exchangers in boilers.