Flow behavior and heat transfer characteristics in Rayleigh-Bénard laminar convection with fluid-particle interaction

2020 ◽  
Vol 146 ◽  
pp. 118840 ◽  
Author(s):  
Mufeng Chen ◽  
Xiaodong Niu ◽  
Peng Yu ◽  
Haruhiko Yamasaki ◽  
Hiroshi Yamaguchi
Keyword(s):  
Heat Transfer ◽  
Flow Behavior ◽  
Particle Interaction ◽  
Fluid Particle ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Laminar Convection ◽  
Rayleigh Benard

Effect of Participating Medium Radiation and Nano-Fluidic Behaviour of Atmospheric Aerosol on Natural Convection of Industrial Dusty Air

2013 ◽  
Author(s):  
Sofen K. Jena ◽  
Swarup K. Mahapatra
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Behavior ◽  
Carbon Black Particle ◽  
Laboratory Model ◽  
Heat Transfer Characteristics ◽  
Participating Media ◽  
Transfer Characteristics ◽  
Flow Circulation ◽  
Marker And Cell Method

The current study is focused on thermal radiation interaction with the natural convection of atmospheric brown cloud (ABC). The current study puts emphasis on ultra fine carbon-black particle suspension of several nano meter range along with some pollutant gas mixture with atmospheric air. The numerical simulation of double diffusive thermo-gravitational convection of ABC is done with Hide and Mason laboratory model for atmosphere. The effect of flow circulation is simulated by setting different value of buoyancy ratios. The effect of participating media radiation has been investigated for various values of optical depth. The governing equations, describing circulation of ABC are solved using modified Marker and Cell method. Gradient dependent consistent hybrid upwind scheme of second order is used for discretization of the convective terms. Discrete ordinate method, with S8 approximation is used to solve radiative transport equation. Comprehensive studies on controlling parameters that affect the flow and heat transfer characteristics have been addressed. The results are provided in graphical and tabular form to delineate the flow behavior and heat transfer characteristics.

Experimental Investigation of the Air Flow Behavior and Heat Transfer Characteristics in Microchannels With Different Channel Lengths

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Zhi Tao ◽  
Zhibing Zhu ◽  
Haiwang Li
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Critical Reynolds Number ◽  
Flow Behavior ◽  
Channel Length ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Poiseuille Number ◽  
Channel Lengths

This paper attempts to experimentally investigate the influence of channel length on the flow behavior and heat transfer characteristics in circular microchannels. The diameters of the channels were 0.4 mm and the length of them were 5 mm, 10 mm, 15 mm, and 20 mm, respectively. All experiments were performed with air and completed with Reynolds number in the range of 300–2700. Results of the experiments show that the length of microchannels has remarkable effects on the performance of flow behavior and heat transfer characteristics. Both the friction factor and Poiseuille number drop with the increase of channel length, and the experimental values are higher than the theoretical ones. Moreover, the channel length does not influence the value of critical Reynolds number. Nusselt number decrease as the increase of channel length. Larger Nusselt numbers are obtained in shorter channels. The results also indicate that in all cases, the friction factor decreases and the Poiseuille number increases with the increase of the Reynolds number. It is also observed that the value of critical Reynolds number is between 1500 and 1700 in this paper, which is lower than the value of theoretical critical Reynolds number of 2300.

scholarly journals Numerical study on heat transfer characteristics of nanofluid based natural circulation loop

2018 ◽  
Vol 22 (2) ◽  
pp. 885-897 ◽  
Author(s):  
Ramesh Bejjam ◽  
Kiran Kumar
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Natural Circulation ◽  
Flow Behavior ◽  
Circulation Loop ◽  
Heat Transfer Characteristics ◽  
Step Size ◽  
Particle Volume ◽  
Transfer Characteristics ◽  
Natural Circulation Loop

In this paper the steady-state analysis has been carried out on single phase natural circulation loop with water and water based Al2O3 (Al2O3-water) nanofluid at 1%, 3%, 5%, and 6% particle volume concentrations. For this study, a 3-D geometry of natural circulation loop is developed and simulated by using the software, ANSYS (FLUENT) 14.5. Based on the Stokes number, mixture model is adopted to simulate the nanofluid based natural circulation loop. For the simulations, the imposed thermal boundary conditions are: constant heat input over the range of 200-1000 W with step size of 200 W at the heat source and isothermal wall temperature of 293 K at the heat sink. Adiabatic boundary condition is imposed to the riser and down-comer. The heat transfer characteristics and fluid-flow behavior of the loop fluid in natural circulation loop for different heat inputs and particle concentrations are presented. The result shows that the mass-flow rate of loop fluid in natural circulation loop is enhanced by 26% and effectiveness of the natural circulation loop is improved by 15% with Al2O3-water nanofluid when compared with water. All the simulation results are validated with the open literature in terms of Reynolds number and modified Grashof number. These comparisons confidently say that the present 3-D numerical model could be useful to estimate the performance of natural circulation loop.

Fluid Flow and Heat Transfer Characteristics of Micro Oscillating Heat Pipes With and Without Expanding Channels

2019 ◽  
Author(s):  
Qin Sun ◽  
Jian Qu ◽  
Jianping Yuan ◽  
Hai Wang ◽  
Scott M. Thompson
Keyword(s):  
Heat Transfer ◽  
High Efficiency ◽  
Flow Behavior ◽  
Heat Pipes ◽  
Thermal Control ◽  
Working Fluid ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Oscillating Motion

Abstract The oscillating heat pipe is considered a promising candidate for high-efficiency and compact thermal control for next-generation electronics. In this paper, the visualized flow and heat transfer characteristics of two silicon-based micro oscillating heat pipes (micro-OHPs) with expanding and straight channels, respectively, were experimentally investigated. The overall size of these two micro-OHPs are both 28 mm × 23 mm × 1.025 mm and have thirty rectangular cross-section channels. The hydraulic diameter of parallel direct channel is 332.4 μm, while they are about 364.4 and 287.0 μm at the two ends of expanding channel, respectively. R141b was used as the working fluid with the volumetric filling ratio of 50%. Inside these two micro-devices, the fluid oscillating motion, including unidirectional movement and intermittent stopovers, was observed at the quasi-steady oscillation state, accompanied by bubbly flow, slug flow and annular/semi-annular flow in microchannels. The micro-OHP with expanding channels possessed better thermal performance and could achieve ephemeral circulation flow, while poorer heat transfer performance occurred for the micro-OHP with straight channels due to more localized slug/plug oscillations and intermittent stopovers. The oscillating amplitudes of liquid slugs are presented to estimate the flow behavior of working fluid inside micro-OHPs. The introduction of expanding channels in a micro-OHP is beneficial for realizing the more robust oscillating motion of liquid slugs with larger oscillating amplitudes for heat transfer enhancement.

Effect of Porosity on Flow Behavior and Heat Transfer Characteristics of Sintered Woven Wire Mesh Structures

2015 ◽  
Author(s):  
Liu Yangpeng ◽  
Xu Guoqiang ◽  
Xiang Luo ◽  
Ma Jiandong ◽  
Li Haiwang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Test Piece ◽  
Flow Direction ◽  
Flow Behavior ◽  
Wire Mesh ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Test Pieces ◽  
Mesh Structures

The structure of sintered woven wire mesh is one of classical porous medium. The porosity is one of the major parameters for the porous media. This paper presents the experimental results of the effect of porosity on internal flow behavior and heat transfer characteristics of sintered metal wire mesh structures. All the three test pieces made of stainless steel wires with the same wire diameter (d = 0.14mm) were sintered after woven. One of them was sintered using two sintered metal wire mesh structures with different porosities (55% and 26%) so that the porosity changed along the flow direction. The porosities of the other two test pieces are 55% and 26%, respectively. The experiments were completed with the Reynolds number in the range of 10 to 42. The permeability and inertia coefficient of each test piece were obtained as well as the friction factor. Infrared camera was used to measure the wall temperature of the test pieces to get the Nusselt numbers. The results show that for all test pieces permeability increases as porosity increases, while inertia coefficient shows the opposite trend. Pressure drop of all pieces increases with respect to the mass flow rate. Friction factor decreases as the Reynolds number increases. The curves for test piece #3 fall between those for test piece #1 and #2 and are more close to that for test #2. Nusselt number increases when the Reynolds number keeps arising. However, The Nusselt numbers of the test piece with changed porosity are influenced by the flow direction. There are no significant correlations of the flow behavior and heat transfer characteristics between the test piece with changed porosity and the other two test pieces with constant porosities.

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