Second law analysis of compressible flow through a diffuser subjected to constant heat flux at wall

The Taylor Couette flow of pseudoplastic fluids is examined while dissipation due to viscous effects through the energy balance. The viscosity of fluid is simultaneously dependent on shear rate and temperature. Exponential dependence of viscosity on temperature is modeled through Nahme law and the shear dependency is modeled according to the Carreau equation. Hydrodynamically, stick boundary conditions are applied and thermally, both constant temperature and constant heat flux on the exterior of cylinders are considered. The governing motion and energy balance equations are coupled adding complexity to the already highly correlated set of differential equations. Introduction of Nahme number has resulted in a nonlinear base flow between the cylinders. As well, the condition of constant heat flux has moved the point of maximum temperature towards the inner cylinder. Taking viscous heating into account, the effects of parameters such as Nahme Number, Deborah Number, material time and pseudoplasticity constant on the heat transfer of the flow are investigated by second law analysis. Moreover, the study shows that the total entropy generation number decreases as the fluid elasticity increases. It, however, increases with increasing Nahme Number.

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Second law analysis of compressible flow through a diffuser subjected to constant wall temperature

International Journal of Exergy ◽

10.1504/ijex.2010.029618 ◽

2010 ◽

Vol 7 (1) ◽

pp. 110

Author(s):

Mohammad Hasan Arshad ◽

Ramazan Kahraman ◽

Ahmet Z. Sahin ◽

Rached Ben Mansour

Keyword(s):

Compressible Flow ◽

Wall Temperature ◽

Second Law ◽

Constant Wall Temperature ◽

Second Law Analysis ◽

Flow Through

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Thermal and Fluid Dynamic Model for Capillary-Driven Heat Pipe With Closed-Form Solution

Volume 1B, Symposia: Fluid Measurement and Instrumentation; Fluid Dynamics of Wind Energy; Renewable and Sustainable Energy Conversion; Energy and Process Engineering; Microfluidics and Nanofluidics; Development and Applications in Computational Fluid Dynamics; DNS/LES and Hybrid RANS/LES Methods ◽

10.1115/fedsm2017-69441 ◽

2017 ◽

Author(s):

Jesse Maxwell

Keyword(s):

Boundary Condition ◽

Heat Flux ◽

Closed Form ◽

Heat Pipe ◽

Closed Form Solution ◽

Constant Heat Flux ◽

Form Solution ◽

Constant Heat ◽

Micro Channels ◽

Flow Through

A model is derived for the steady state performance of capillary-driven heat pipes on the basis treating fluid flow through miniature- and micro-channels and applied as bulk properties to a large aspect ratio quasi-one-dimensional two-phase system. Surface tension provides the driving force based on an equivalent bulk capillary radius while laminar flow through micro-channels and the vapor core are treated. Heat conduction is accounted for radially while isothermal advection is treated along the axis. A closed-form solution is derived for a steady state heat pipe with a constant heat flux boundary condition on the evaporator as well as a constant heat flux or a convective boundary condition along the condenser. Two solution methods are proposed, and the result is compared to empirical data for a copper-water heat pipe. The components of the closed-form solution are discussed as contributors to driving or frictional forces, and the existence of an optimal pore radius is demonstrated.

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