The study of laminar convective heat transfer of CuO/water nanofluid through an equilateral triangular duct at constant wall heat flux

Convective heat transfer of a thermally developing rarefied gas flow in a microtube with boundary shear work, viscous dissipation, and axial conduction is analyzed numerically for both constant wall temperature (CWT) and constant wall heat flux (CHF) boundary conditions. Analytical solutions for the fully developed flow conditions including the boundary shear work are also derived. The proper thermal boundary condition considering the sliding friction at the wall for the CHF case is implemented. The sliding friction is also included in the calculation of the wall heat flux for the CWT case. A comparative study is performed to quantify the effect of the shear work on heat transfer in the entrance—and the fully developed—regions for both gas cooling and heating. Results are presented in both graphical and tabular forms for a range of problem parameters. The results show that the effect of shear work on heat transfer is considerable and it increases with increasing both the Knudsen number and Brinkman number. Neglecting the shear work in a microtube slip flow leads to over- or underestimating the Nusselt number considerably. In particular, for the CWT case with fully developed conditions, the contribution of the shear work to heat transfer can be around 45% in the vicinity of the upper limit of the slip flow regime, regardless of how small the nonzero Brinkman number can be.

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Convective Heat Transfer of Molten Salt in Receiver Tube with Axially and Circumferentially Non-Uniform Heat Flux

Journal of Thermal Science ◽

10.1007/s11630-021-1470-z ◽

2021 ◽

Author(s):

Xiangyang Shen ◽

Jing Ding ◽

Jianfeng Lu

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Molten Salt ◽

Convective Heat Transfer ◽

Convective Heat ◽

Uniform Heat Flux ◽

Uniform Heat

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Analysis of flow and heat transfer over stretching/shrinking and porous surfaces

Journal of Plastic Film & Sheeting ◽

10.1177/87560879211025805 ◽

2021 ◽

pp. 875608792110258

Author(s):

Azhar Ali ◽

Dil Nawaz Khan Marwat ◽

Aamir Ali

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Convective Heat Transfer ◽

Convective Heat ◽

Current Model ◽

Uniform Heat Flux ◽

Similarity Transformations ◽

Flow And Heat Transfer ◽

Special Cases ◽

Porous Surfaces

Flows and heat transfer over stretching/shrinking and porous surfaces are studied in this paper. Unusual and generalized similarity transformations are used for simplifying governing equations. Current model includes all previous cases of stretched/shrunk flows with thermal effects discussed so far. Moreover, we present three different cases of thermal behavior (i) prescribed surface temperature (ii) Variable/uniform convective heat transfer at plat surface and (iii) prescribed variable/uniform heat flux. Stretching/shrinking velocity Uw(x), porosity [Formula: see text], heat transfer [Formula: see text], heat flux [Formula: see text] and convective heat transfer at surface are axial coordinate dependent. Boundary layer equations and boundary conditions are transformed into nonlinear ODEs by introducing unusual and generalized similarity transformations for the variables. These simplified equations are solved numerically. Final ODEs represent suction/injection, stretching/shrinking, temperature, heat flux, convection effects and specific heat. This current problem encompasses all previous models as special cases which come under the scope of above statement (title). The results of classical models are scoped out as a special case by assigning proper values to the parameters. Numerical result shows that the dual solutions can be found for different possible values of the shrinking parameter. A stability analysis is accomplished and apprehended in order to establish a criterion for determining linearly stable and physically compatible solutions. The significant features and diversity of the modeled equations are scrutinized by recovering the previous problems of fluid flow and heat transfer from a uniformly heated sheet of variable (uniform) thickness with variable (uniform) stretching/shrinking and injection/suction velocities.

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