Abstract
Turning diffuser is a type of diffuser with certain angle of turn used as adapter or ejector in flow line for energy recovery. It is also employed in HVAC systems, wind tunnels, piping systems, gas turbine cycles and aircraft engine. Although significant works have been done on diffusers in the literature but not much focus has been given to the 3D turning diffuser. In this study, the effects of curvature ratio, adverse pressure gradient parameter and tuning angle on entropy generation rate due to viscous dissipation, turbulent dissipation, volumetric entropy generation rate and efficiency are investigated in the curved rectangular diffuser under turbulent flow regime. The tuning angles, curvature ratios and adverse pressure gradient parameters are considered $$ \theta = 60^{^\circ } ,80^{^\circ } ,90^{^\circ } ,\frac{\delta }{R} = 0.0113, 0.0161, 0.023 $$ and $$ \beta = 0.56, 0.62, 0.86 $$ , respectively. The analysis on entropy generation using Bejan’s entropy generation equation for curved rectangular diffuser with different turning angles, curvature ratios and adverse pressure gradient parameters has not been addressed before and is introduced in this study for the first time. Results show that in order to reach the maximum efficiency with minimum entropy generation for curved rectangular diffuser design in air-conditioning systems, the highest turning angle, the lowest adverse pressure gradient parameter and curvature ratio should be selected. In addition, the efficiency increases with increasing turning angle, and decreasing the adverse pressure gradient parameter and curvature ratio. Finally, it is concluded that for all different turning angles, curvature ratios and adverse pressure gradient parameters, the entropy generation due to turbulence dissipations is more than the entropy generation due to viscous dissipations.
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