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.

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%.

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.

Nonlinear Characteristics of a Sudden Expansion Followed by Sudden Contraction Channel

2016 ◽  
Author(s):  
Keyan Liu ◽  
Mo Yang ◽  
Yuwen Zhang ◽  
Chunyun Shen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Temperature Field ◽  
Simple Algorithm ◽  
Sudden Expansion ◽  
Nonlinear Characteristics ◽  
Classic Problem ◽  
Flow And Heat Transfer ◽  
Quick Scheme ◽  
Sudden Contraction

The flow and heat transfer in a sudden expansion followed by sudden contraction channel are widely applied in industry, and it is also a classic problem for theoretical study. In this article, the SIMPLE algorithm with QUICK scheme were used to study the flow and heat transfer in a sudden expansion followed by sudden contraction channel. The nonlinear characteristics and temperature field were investigated for various Reynolds number and geometrical dimension. The results show that the temperature field evolves from symmetric to asymmetric state with the increasing Re. When Re ≥ Rec, the flow loses stability and from symmetric to asymmetric via a symmetry-breaking bifurcation; when the Reynolds number continues to increase, the fluid flow and heat transfer oscillation. The nonlinear characteristics of flow and heat transfer within the channel is further analyzed.

Fundamental Issues and Recent Advancements in Analysis of Aircraft Brake Natural Convective Cooling

1998 ◽  
Vol 120 (4) ◽  
pp. 840-857 ◽  
Author(s):  
M. P. Dyko ◽  
K. Vafai
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Field ◽  
Three Dimensional ◽  
Convective Cooling ◽  
Cooling Flow ◽  
Physical Mechanisms ◽  
Braking System ◽  
Flow And Heat Transfer ◽  
Convection Cooling

A heightened awareness of the importance of natural convective cooling as a driving factor in design and thermal management of aircraft braking systems has emerged in recent years. As a result, increased attention is being devoted to understanding the buoyancy-driven flow and heat transfer occurring within the complex air passageways formed by the wheel and brake components, including the interaction of the internal and external flow fields. Through application of contemporary computational methods in conjunction with thorough experimentation, robust numerical simulations of these three-dimensional processes have been developed and validated. This has provided insight into the fundamental physical mechanisms underlying the flow and yielded the tools necessary for efficient optimization of the cooling process to improve overall thermal performance. In the present work, a brief overview of aircraft brake thermal considerations and formulation of the convection cooling problem are provided. This is followed by a review of studies of natural convection within closed and open-ended annuli and the closely related investigation of inboard and outboard subdomains of the braking system. Relevant studies of natural convection in open rectangular cavities are also discussed. Both experimental and numerical results obtained to date are addressed, with emphasis given to the characteristics of the flow field and the effects of changes in geometric parameters on flow and heat transfer. Findings of a concurrent numerical and experimental investigation of natural convection within the wheel and brake assembly are presented. These results provide, for the first time, a description of the three-dimensional aircraft braking system cooling flow field.

scholarly journals Computational Performance of Disparate Lattice Boltzmann Scenarios under Unsteady Thermal Convection Flow and Heat Transfer Simulation

Computation ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 65
Author(s):  
Aditya Dewanto Hartono ◽  
Kyuro Sasaki ◽  
Yuichi Sugai ◽  
Ronald Nguele
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Convection ◽  
Lattice Boltzmann ◽  
Numerical Results ◽  
Convection And Heat Transfer ◽  
Steady State Condition ◽  
Physical Systems ◽  
Flow And Heat Transfer ◽  
Computational Performance

The present work highlights the capacity of disparate lattice Boltzmann strategies in simulating natural convection and heat transfer phenomena during the unsteady period of the flow. Within the framework of Bhatnagar-Gross-Krook collision operator, diverse lattice Boltzmann schemes emerged from two different embodiments of discrete Boltzmann expression and three distinct forcing models. Subsequently, computational performance of disparate lattice Boltzmann strategies was tested upon two different thermo-hydrodynamics configurations, namely the natural convection in a differentially-heated cavity and the Rayleigh-Bènard convection. For the purposes of exhibition and validation, the steady-state conditions of both physical systems were compared with the established numerical results from the classical computational techniques. Excellent agreements were observed for both thermo-hydrodynamics cases. Numerical results of both physical systems demonstrate the existence of considerable discrepancy in the computational characteristics of different lattice Boltzmann strategies during the unsteady period of the simulation. The corresponding disparity diminished gradually as the simulation proceeded towards a steady-state condition, where the computational profiles became almost equivalent. Variation in the discrete lattice Boltzmann expressions was identified as the primary factor that engenders the prevailed heterogeneity in the computational behaviour. Meanwhile, the contribution of distinct forcing models to the emergence of such diversity was found to be inconsequential. The findings of the present study contribute to the ventures to alleviate contemporary issues regarding proper selection of lattice Boltzmann schemes in modelling fluid flow and heat transfer phenomena.

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