Heat transfer and pressure drop penalty study in flattened micro-finned tubes

Abstract

The heat transfer,friction factor,pressure drop,and performance of the micro-finned flattened tubes are studied numerically. This chapter presents the heat transfer to single-phase steady-state fluid flow with water as fluid media from the isothermally heated wall of one meter long straight tube. The Reynolds numbers are varied between 10,000 and 30,000. Separate geometric models are developed with 12 and 16 longitudinal microfins. The cross-sectional perimeter of the flattened micro-finned tube is considered equal to the circular finned tube while modeling the cases. The heat transfer has enhanced in the flattened micro-finned tubes for all Reynolds numbers. The heat transfer coefficient has comparatively improved in the flattened tubes. However,a tremendous increase in pressure drop has been produced in the flattened microfin tubes. It thus decreases the pressure drop penalty for the flattened tubes leading to significantly increased pumping power. The pressure drop penalty decreases with an increase in Reynolds number. A nearly 2.5 times enhancement is estimated for the heat transfer coefficient. In contrast,a nearly 25-fold increase in pressure drop is noticed in the flattened micro finned tubes. Thus,the pressure drop generated in the flattened tube is substantially more prominent than the enhancement in the heat transfer. The performance evaluation factor is more than two for the flattened tubes with microfins.