Effect Of Roughness Shape On Heat Transfer And Flow Friction Characteristics Of Solar Air Heater With Roughened Absorber Plate
Free (open access)
A. Chaube, P. K. Sahoo & S. C. Solanki
A 2-D computational analysis is carried out to assess the comparative performance of the absorber plate of a solar air heater with different roughness elements using commercial software package Fluent 6.1. The assessment is based on heat transfer enhancement with minimum pressure penalty. Ten different rib shapes (viz. Rectangular, Square, Chamfered, Triangular, Semicircle etc) are investigated at the Reynolds number range from about 3000–20000, in which solar air heaters normally operate. The SST kω turbulence model is selected by comparing the predictions of different turbulence models with experimental results available in the literature. Using the selected turbulence model a computational analysis is carried out to predict the heat transfer performance and flow friction characteristics of absorber plates with 10 different rib roughness elements. The analysis is carried out for both the flow regimes i.e. transitional flow regime (5 ≤ e+ ≤ 70) and fully rough regime (e+ ≥ 70). Keywords: turbulence, roughness Reynolds number, aspect ratio, friction factor, heat transfer coefficient, Nusselt number, chamfer angle, pitch etc. 1 Introduction Artificial roughness up to laminar sub-layer to enhance heat transfer coefficient is used in various applications like gas turbine blade cooling channels, heat exchangers, nuclear reactors and solar air heaters. A number of experimental studies [1, 2] in this area have been carried out but very few attempts of numerical investigation have been made so far due to complexity of flow pattern and computational limitations. In the present work, an attempt is made to predict
turbulence, roughness Reynolds number, aspect ratio, friction factor, heat transfer coefficient, Nusselt number, chamfer angle, pitch etc.