Refrigerant film flow and heat transfer characteristics on the elliptical tube under constant wall temperature

Numerical computations were performed to obtain for heat transfer characteristics of turbulent gas flow in micro-tubes with constant wall temperature whose temperature is lower than the inlet temperature (cooled case). The numerical methodology was based on Arbitrary-Lagrangian-Eulerinan (ALE) method to solve compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was employed to evaluate eddy viscosity coefficient and turbulence energy. The tube diameter ranges from 100 μm to 400 μm and the aspect ratio of the tube diameter and the length is fixed at 200. The stagnation temperature was fixed at 300 K and the computations were done for wall temperature, which ranged from 250 K to 295 K. The stagnation pressure was chosen in such a way that the flow is in turbulent flow regime. The results in wide range of Reynolds number and Mach number were obtained. The bulk temperature based on the static temperature and the total temperature of the cooled case are compared with those of heated case and also with temperatures of the incompressible flow. The result shows that different heat transfer characteristics are obtained for each cooled and heated case. A correlation for the prediction of the heat transfer rate of the turbulent gas flow in a micro-tube is proposed.

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Heat transfer characteristics of thermally developing flow in rectangular microchannels with constant wall temperature

International Journal of Thermal Sciences ◽

10.1016/j.ijthermalsci.2020.106412 ◽

2020 ◽

Vol 155 ◽

pp. 106412 ◽

Cited By ~ 1

Author(s):

Liangbin Su ◽

Zhipeng Duan ◽

Boshu He ◽

Hao Ma ◽

Xiaoru Ning ◽

...

Keyword(s):

Heat Transfer ◽

Wall Temperature ◽

Heat Transfer Characteristics ◽

Constant Wall Temperature ◽

Rectangular Microchannels ◽

Transfer Characteristics ◽

Developing Flow

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AL2O3-WATER NANOFLUID FALLING-FILM FLOW AND HEAT TRANSFER CHARACTERISTICS ON A HORIZONTAL CIRCULAR TUBE

Journal of Enhanced Heat Transfer ◽

10.1615/jenhheattransf.2013007763 ◽

2013 ◽

Vol 20 (3) ◽

pp. 213-223

Author(s):

Saeid Jani

Keyword(s):

Heat Transfer ◽

Film Flow ◽

Circular Tube ◽

Falling Film ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Flow And Heat Transfer

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Numerical Investigation of Fully Developed Fluid Flow and Heat Transfer in Double-Trapezoidal Microchannels

Volume 10: Micro- and Nano-Systems Engineering and Packaging ◽

10.1115/imece2013-66734 ◽

2013 ◽

Author(s):

Mostafa Shojaeian ◽

Ali Koşar

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Fluid Flow ◽

Aspect Ratio ◽

Heat Transfer Characteristics ◽

Constant Wall Temperature ◽

Base Angle ◽

Transfer Characteristics ◽

Flow And Heat Transfer ◽

Poiseuille Number

Fully developed fluid flow and heat transfer characteristics of double-trapezoidal microchannels with constant wall temperature are numerically investigated in the slip flow regime. The governing equations are solved together with the appropriate boundary conditions using finite volume method. The effect of rarefaction on Poiseuille number, Po, and Nusselt number, Nu, is studied for Knudsen numbers, Kn, varying from 0 to 0.1. The effects of base angle, B, and aspect ratio, A, on the fluid flow and the heat transfer characteristics are also examined. The results reveal that the rarefaction and the cross-section shapes have prominent effects on these characteristics of double-trapezoidal microchannels. According to the results, the Poiseuille number decreases with increasing Kn, while the values of the Nusselt number completely depend on the impacts of the rarefaction and the fluid-surface interaction. Po and Nu decrease with aspect ratio for A<1, while the effect of aspect ratio on Po and Nu becomes unclear for A>1. Moreover, an increase in the base angle has a positive effect on Po and Nu, however this increasing trend is less pronounced for B > 60 ° and A < 1.67.

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