Investigation of heat transfer and pressure drop for various obstacles in a rectangular‐sectioned 90° bend

Abstract

Purpose

Re<95,000 based on hydraulic diameter, heat transfer and turbulent flow through a rectangular‐sectioned 90° bend was investigated numerically and experimentally. To develop turbulence level, square prism and cylindrical obstacles was placed in the center of the bend.

Design/methodology/approach

For heat transfer, uniform heat flux of 5,000 W/m² from bend surfaces is assumed. Numerical analysis was realized for both the turbulent flow and heat transfer. For numerical study, FLUENT 6.1.22 code, RSM turbulence model, hybrid hexahedral‐tetrahedral cell structures and uniform inlet velocity assumption were selected. For the pressure distribution in the bend and velocity profile at the outlet of the bend, the experiments was carried out by means of manometers with ethyl alcohol, Mano‐air 500 Equipment and pitot‐static tube.

Findings

There was a high level of validation obtained between the numerical and the experimental results. Thereby, the mentioned numerical calculation method can be used most engineering applications. For Re>20,000, the square prism obstacles provide higher turbulence level and more favorable heat transfer than cylindrical obstacles. For Re<20,000, the obstacle use would not require for enhanced heat transfer aim. The obstacle in the bend cause considerably pressure drop in the bend.

Originality/value

The turbulent flow in the bend without obstacle has been numerically investigated by various turbulence models with the non‐refined mesh structure and various wall functions. For numerical solution of the turbulence flows and the heat transfer in the rectangular bend with obstacles, the FLUENT code and RSM turbulence model with enhanced wall functions are selected. In order to adapt the cell size and number to the turbulent flow the mesh structure was refined over curvature of turbulence dissipation rate in the bend.

Citation

Ünalan, S., Orhan Akansu, S. and Konca, A. (2007), "Investigation of heat transfer and pressure drop for various obstacles in a rectangular‐sectioned 90° bend", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 17 No. 5, pp. 494-511. https://doi.org/10.1108/09615530710752964