Experimental measurement of thermal-hydraulic characteristics at low Reynolds number in wavy fin heat exchangers.

摘要

Experiments were conducted to predict the thermal hydraulic characteristics for flow in wavy fin heat exchangers. Low Reynolds number (0.1 Re 100) and larger Prandtl number (318 Pr 573) were considered using high viscous oil. Experimental results were obtained for fifteen different fin specimens having various geometric parameters. The corrugation ratio ranged from 0.1 to 0.18, the aspect ratio ranged from 0.07 to 0.67, and spacing ratio ranged from 0.4 to 1.23.;Finally, an asymptotic model was developed by combining both analytical models for predicting the Fanning friction factor, f, and Colburn factor, j, which covered a wide range of Reynolds number. Most of the experimental data sets agreed with this model to within +/- 25%.;Experimental results of heat transfer and fluid friction data for all the wavy fins exposed the presence of two flow regimes. These were: (1) the low Reynolds number regime where the flow behaviour is the same as that in rectangular ducts, (2) the laminar boundary layer regime where vortices induced in the wall waviness valley region with the increase of Reynolds number provided a higher heat transfer performance and pressure drop penalty. This could be due to the complex flow pattern in the wavy fin channels. Models for each regime were developed from fundamental solutions of fluid dynamics and heat transfer. Experimental results were compared with both models which suggested a new model.