Combined Heat Transfer of Natural Convection-Conduction and Surface Radiation in an Open Cavity Heated by Constant Flux

2010 ◽  
Author(s):  
ZhiYun Wang ◽  
Mo Yang ◽  
YuWen Zhang ◽  
Ling Li
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Model ◽  
Simple Algorithm ◽  
Open Cavity ◽  
Surface Radiation ◽  
Surface Emissivity ◽  
Constant Flux ◽  
Quick Scheme ◽  
Combined Heat Transfer

Combined heat transfer of natural convection-conduction and surface radiation in an open cavity heated by constant flux is studied in this paper. Flow model is laminar and SIMPLE algorithm and QUICK scheme are employed. The relevant parameters are as follows, Prandtl number is 0.7 and dimensionless solid thickness is 0.2, conductivity ratio rangs from 0 to 1000, Rayleigh number ranges from 103 to 109, surface emissivity ranges from 0 to 1. The numerical results shows secondary circular formed as an effect of radiation which increased the average Nusselt number about from 54.1% to 100.3%.

Oscillation and Chaos in Combined Heat Transfer by Natural Convection, Conduction, and Surface Radiation in an Open Cavity

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Zhiyun Wang ◽  
Mo Yang ◽  
Ling Li ◽  
Yuwen Zhang
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Simple Algorithm ◽  
Open Cavity ◽  
Surface Radiation ◽  
Bottom Surface ◽  
Thermal Plumes ◽  
Flow And Heat Transfer ◽  
Quick Scheme ◽  
Combined Heat Transfer

Combined heat transfer by natural convection, conduction, and surface radiation in an open cavity is solved numerically by employing SIMPLE algorithm with QUICK scheme. The unsteady-state flow and heat transfer exhibited periodic oscillating or chaotic behaviors due to formation of the thermal plumes at the bottom wall. If the formation of thermal plumes is periodic, the oscillations of flow and heat transfer are also periodic. On the other hand, chaotic oscillations of flow and heat transfer can be observed when the formation of thermal plumes at the bottom surface is chaotic.

scholarly journals Combined Heat Transfer Mechanisms in the Porous Char Layer Formed from the Intumescent Coatings under Fire

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 200
Author(s):  
Lingyun Zhang ◽  
Yupeng Hu ◽  
Minghai Li
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Thermal Conduction ◽  
Total Heat ◽  
Surface Radiation ◽  
Total Heat Transfer ◽  
Char Layer ◽  
Competition Result ◽  
Transfer Mechanisms ◽  
Combined Heat Transfer

This study examines the combined heat transfer by thermal conduction, natural convection and surface radiation in the porous char layer that is formed from the intumescent coating under fire. The results show that some factors, such as the Rayleigh number, conductivity ratio, emissivity, radiation–conduction number, void fraction and heating mode have a certain effect on the total heat transfer. In addition, the natural convection of the air in the cavity always inhibits surface radiation among the solid walls and thermal conduction, and the character of the total heat transfer is the competition result of the three heat transfer mechanisms.

Numerical study of surface radiation and combined natural convection heat transfer in a solar cavity receiver

2017 ◽  
Vol 27 (10) ◽  
pp. 2385-2399 ◽  
Author(s):  
Kamel Milani Shirvan ◽  
Mojtaba Mamourian ◽  
Soroush Mirzakhanlari ◽  
A.B. Rahimi ◽  
R. Ellahi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Numerical Solutions ◽  
Convection Heat Transfer ◽  
Surface Radiation ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Surface Emissivity ◽  
Content Type

Purpose The purpose of this paper is to present the numerical solutions of surface radiation and combined natural convection heat transfer in a solar cavity receiver. The paper aims to discuss sundry issues that take place in the said model. Design/methodology/approach The numerical solutions are developed by means of second-order upwind scheme using the SIMPLE algorithm. Findings The effects of physical factors such as Rayleigh number (104 ≤ Ra ≤ 106), inclination angels of insulated walls (0º ≤ θ ≤ 10º) and the wall surface emissivity (0 ≤ ε ≤ 1) on natural convection-surface radiation heat transfer rate are analyzed. Impact of sundry parameters on flow quantities are discussed and displayed via graphs and tables. Stream lines and isothermal lines have also been drawn in the region of cavity. The numerical results reveal that increasing the Rayleigh number, wall surface emissivity and inclination angels of insulated walls in an open cavity enhances the mean total Nusselt number. The variations of the surface radiation and natural convection heat transfer mean Nusselt numbers are very small to the inclination angle of θ, while a significant change is noted for the case of Rayleigh number and emissivity. Originality/value To the best of authors’ knowledge, this model is reported for the first time.

Effect of Surface Emissivity on Conjugate Turbulent Natural Convection in an Air-Filled Cavity with a Heat Source

2016 ◽  
Vol 685 ◽  
pp. 315-319 ◽  
Author(s):  
Igor V. Miroshnichenko ◽  
Mikhail A. Sheremet
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Surface Radiation ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Heat Conducting ◽  
Surface Emissivity ◽  
Turbulent Natural Convection ◽  
Effect Of Surface

The interaction of conjugate turbulent natural convection and surface thermal radiation in an air-filled square enclosure having heat-conducting solid walls of finite thickness and a heat source has been numerically studied. The primary focus was on the influence of surface emissivity on complex heat transfer. The mathematical model has been formulated in dimensionless variables such as stream function, vorticity and temperature using k-ε turbulent model. The effect of surface emissivity on the average total Nusselt number has been defined. The distributions of streamlines and temperature fields, describing characteristics of the analyzed fluid flow and heat transfer have been obtained. The results clearly show an essential effect of surface radiation on unsteady turbulent heat transfer.

Lattice Boltzmann Method for Combined Natural Convection Surface Radiation in Open Cavity

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Ayoub Msaddak ◽  
Mohieddine Ben Salah ◽  
Ezeddine Sediki
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Lattice Boltzmann Method ◽  
Inclination Angle ◽  
Lattice Boltzmann ◽  
Surface Radiation ◽  
Surface Emissivity ◽  
Boltzmann Method

Lattice Boltzmann method (LBM) is performed to study numerically combined natural convection and surface radiation inside an inclined two-dimensional open square cavity. The cavity is heated by a constant temperature at the wall facing the opening. The walls normal to the heated surface are assumed to be adiabatic, diffuse, gray, and opaque while the open boundary is assumed to be black at ambient temperature. A Bathnagar, Gross and Krook (BGK) collision model with double distribution function (D2Q9-D2Q4) is adopted. Effects of surface radiation, inclination angle, and Rayleigh number on the heat transfer are analyzed and discussed. Results are presented in terms of isotherms, streamlines, and Nusselt number. It was found that the presence of surface radiation enhances the heat transfer. The convective Nusselt number decreases with increasing surface emissivity as well as with Rayleigh number, while the total Nusselt number increases with increasing surface emissivity and Rayleigh number. The inclination angle has also a significant effect on flow and heat transfer inside the cavity. However, the magnitude of total heat transfer decreases considerably when open cavity is tilted downward.

The Influence of Burner Nozzle Angle for Flow Field and Heat Transfer of Ultra-Supercritical Tower Boiler

2011 ◽  
Author(s):  
Saike Chen ◽  
Mo Yang ◽  
Yuwen Zhang ◽  
Zhangyang Kang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Theoretical Analysis ◽  
Flow Field ◽  
Velocity Distribution ◽  
Velocity Vector ◽  
Flow Model ◽  
Simple Algorithm ◽  
Quick Scheme ◽  
Burner Nozzle

The angle of burner nozzle is an important factor for burning of ultra-supercritical tower boiler. In this paper, gassolid multiphase flow and combustion in 1000MW Ultra-supercritical tower furnace were of the numerical simulation under different conditions. The angle of burner nozzle deflects downward, and the angle is 0°, 3°, 6°, 9° and 12°. Flow model is turbulence and SIMPLE algorithm and QUICK scheme are employed. Through theoretical analysis of different conditions (the velocity distribution in different face; the velocity vector in furnace; the temperature in furnace; the NOx, CO2 and O2 emissions in outlet), finally, the law of the angle of burner nozzle for flow field and heat transfer in ultra-supercritical tower boiler is found.

Numerical Survey of the Melting Driven Natural Convection Using Generation Heat Source: Application to the Passive Cooling of Electronics Using Nano-Enhanced Phase Change Material

2019 ◽  
Vol 12 (2) ◽  
Author(s):  
Hamza Faraji ◽  
Mustapha Faraji ◽  
Mustapha El Alami
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Phase Change ◽  
Phase Change Material ◽  
Metallic Nanoparticles ◽  
Simple Algorithm ◽  
Bottom Side ◽  
Volume Method ◽  
Change Material

Abstract The present paper reports numerical results of the melting driven natural convection in an inclined rectangular enclosure filled with nano-enhanced phase change material (NePCM). The enclosure is heated from the bottom side by a flush-mounted heat source (microprocessor) that generates heat at a constant and uniform volumetric rate and mounted on a substrate (motherboard). All the walls are considered adiabatic. The purpose of the investigation is analyzing the effect of nanoparticles insertion by quantifying their contribution to the overall heat transfer. Combined effects of the PCM type, the inclination angle and the nanoparticles fraction on the structure of the fluid flow and heat transfer are investigated. A 2D mathematical model based on the conservation equations of mass, momentum, and energy was developed. The governing equations were integrated and discretized using the finite volume method. The SIMPLE algorithm was adopted for velocity–pressure coupling. The obtained results show that the nanoparticles insertion has an important quantitative effect on the overall heat transfer. The insertion of metallic nanoparticles with different concentrations affects the thermal behavior of the heat sink. They contribute to an efficient cooling of the heat source. The effect of nanoparticles insertion is also shown at the temperature distribution along the substrate.

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