Melting from heat sources flush mounted on a conducting vertical wall

2000 ◽  
Vol 10 (3) ◽  
pp. 286-307 ◽  
Author(s):  
Bruno Binet ◽  
Marcel Lacroix
Keyword(s):  
Heat Source ◽  
Numerical Study ◽  
Vertical Wall ◽  
Melting Process ◽  
Source Distribution ◽  
Heat Sources ◽  
Aspect Ratios ◽  
Electric Equipment ◽  
Convection Dominated ◽  
Storage Units

A numerical study is conducted for natural convection dominated melting inside discretely heated rectangular enclosures. This study finds applications in the design and operation of thermal energy storage units and the cooling of electric equipment. Results show the benefits of discrete heating over uniform heating for optimizing the melting process. For enclosures of high aspect ratios (A ∼> 4), configurations leading to well controlled heat source temperatures and long melting times are obtained. For cavities of low aspect ratios (A ∼< 4), it is found that the source span η is the most influential parameter. For η ∼ < 0.45, the melting times are shorter and the heat source temperatures remain equal and moderate during the entire melting process. A map for determining the cavity size and the source distribution that optimizes the melting process is presented.

scholarly journals Convection in an internally heated stratified heterogeneous reservoir

2019 ◽  
Vol 870 ◽  
pp. 67-105 ◽  
Author(s):  
Angela Limare ◽  
Claude Jaupart ◽  
Edouard Kaminski ◽  
Loic Fourel ◽  
Cinzia G. Farnetani
Keyword(s):  
Heat Source ◽  
Scaling Laws ◽  
Lower Layer ◽  
Thermal Structure ◽  
Internal Heat ◽  
Source Distribution ◽  
Heat Sources ◽  
Homogeneous Fluid ◽  
Earth’S Mantle ◽  
Lower Fluid

The Earth’s mantle is chemically heterogeneous and probably includes primordial material that has not been affected by melting and attendant depletion of heat-producing radioactive elements. One consequence is that mantle internal heat sources are not distributed uniformly. Convection induces mixing, such that the flow pattern, the heat source distribution and the thermal structure are continuously evolving. These phenomena are studied in the laboratory using a novel microwave-based experimental set-up for convection in internally heated systems. We follow the development of convection and mixing in an initially stratified fluid made of two layers with different physical properties and heat source concentrations lying above an adiabatic base. For relevance to the Earth’s mantle, the upper layer is thicker and depleted in heat sources compared to the lower one. The thermal structure tends towards that of a homogeneous fluid with a well-defined time constant that scales with $Ra_{H}^{-1/4}$, where $Ra_{H}$ is the Rayleigh–Roberts number for the homogenized fluid. We identified two convection regimes. In the dome regime, large domes of lower fluid protrude into the upper layer and remain stable for long time intervals. In the stratified regime, cusp-like upwellings develop at the edges of large basins in the lower layer. Due to mixing, the volume of lower fluid decreases to zero over a finite time. Empirical scaling laws for the duration of mixing and for the peak temperature difference between the two fluids are derived and allow extrapolation to planetary mantles.

Three-Dimensional Steady and Oscillatory Natural Convection in a Rectangular Enclosure With Heat Sources

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Amin Bouraoui ◽  
Rachid Bessaïh
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Three Dimensional ◽  
Air Cooling ◽  
Heat Sources ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Simpler Algorithm ◽  
Strong Relation

In this paper, a numerical study of three-dimensional (3D) natural convection air-cooling of two identical heat sources, simulating electronic components, mounted in a rectangular enclosure was carried out. The governing equations were solved by using the finite-volume method based on the SIMPLER algorithm. The effects of Rayleigh number Ra, spacing between heat sources d, and aspect ratios Ax in x-direction (horizontal) and Az in z-direction (transversal) of the enclosure on heat transfer were investigated. In steady state, when d is increased, the heat transfer is more important than when the aspect ratios Ax and Az are reduced. In oscillatory state, the critical Rayleigh numbers Racr for different values of spacing between heat sources and their aspect ratios, at which the flow becomes time dependent, were obtained. Results show a strong relation between heat transfers, buoyant flow, and boundary layer. In addition, the heat transfer is more important at the edge of each face of heat sources than at the center region.

Forced Convection in a Porous Channel With Localized Heat Sources

1994 ◽  
Vol 116 (2) ◽  
pp. 465-472 ◽  
Author(s):  
A. Hadim
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Pressure Drop ◽  
Heat Source ◽  
Forced Convection ◽  
Numerical Study ◽  
Porous Channel ◽  
Heat Sources ◽  
Porous Layers ◽  
Channel Configuration

A numerical study is performed to analyze steady laminar forced convection in a channel filled with a fluid-saturated porous medium and containing discrete heat sources on the bottom wall. Hydrodynamic and heat transfer results are reported for two configurations: (1) a fully porous channel, and (2) a partially porous channel, which contains porous layers above the heat sources and is nonporous elsewhere. The flow in the porous medium is modeled using the Brinkman-Forchheimer extended Darcy model. Heat transfer rates and pressure drop are evaluated for wide ranges of Darcy and Reynolds numbers. Detailed results of the evolution of the hydrodynamic and thermal boundary layers are also provided. The results indicate that as the Darcy number decreases, a significant increase in heat transfer is obtained, especially at the leading edge of each heat source. For fixed Reynolds number, the length-averaged Nusselt number reaches an asymptotic value in the Darcian regime. In the partially porous channel, it is found that when the width of the heat source and the spacing between the porous layers are of the same magnitude as the channel height, the heat transfer enhancement is almost the same as in the fully porous channel while the pressure drop is significantly lower. These results suggest that the partially porous channel configuration is a potentially attractive heat transfer augmentation technique for electronic equipment cooling, an end that motivated this study.

A Numerical Study of Natural Convection in Partially Open Enclosures With a Conducting Side-Wall

2004 ◽  
Vol 126 (1) ◽  
pp. 76-83 ◽  
Author(s):  
G. Desrayaud ◽  
G. Lauriat
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Finite Thickness ◽  
Vertical Wall ◽  
Side Wall ◽  
Practical Applications ◽  
Hot Air ◽  
Aspect Ratios ◽  
Vertical Walls ◽  
Rayleigh Numbers

A numerical study of natural convection generated by a cold vertical wall of an enclosure with two openings on the opposite wall of finite thickness is presented. The enclosure is connected to an infinite reservoir filled with hot air. A two-dimensional laminar flow is assumed both within the enclosure and along the side of the bounding wall immersed into the reservoir. The effects of the size of the openings, spacing between the vertical walls and thermal resistance of the bounding wall are investigated. Numerical results are discussed for aspect ratios of the enclosure and Rayleigh numbers relevant to practical applications.

scholarly journals Numerical Investigation on Two-Phase Flow Heat Transfer Performance and Instability with Discrete Heat Sources in Parallel Channels

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4408
Author(s):  
Changming Hu ◽  
Rui Wang ◽  
Ping Yang ◽  
Weihao Ling ◽  
Min Zeng ◽  
...  
Keyword(s):  
Heat Source ◽  
Heat Transfer Performance ◽  
Source Distribution ◽  
Phase Flow ◽  
Heat Sources ◽  
Two Phase ◽  
Discrete Heat Sources ◽  
Discrete Heat Source ◽  
Parallel Channels ◽  
Heat Source Distribution

With the rapid development of integrated circuit technology, the heat flux of electronic chips has been sharply improved. Therefore, heat dissipation becomes the key technology for the safety and reliability of the electronic equipment. In addition, the electronic chips are distributed discretely and used periodically in most applications. Based these problems, the characteristics of the heat transfer performance of flow boiling in parallel channels with discrete heat source distribution are investigated by a VOF model. Meanwhile, the two-phase flow instability in parallel channels with discrete heat source distribution is analyzed based on a one-dimensional homogeneous model. The results indicate that the two-phase flow pattern in discrete heat source distribution is more complicated than that in continuous heat source distribution. It is necessary to optimize the relative position of the discrete heat sources, which will affect the heat transfer performance. In addition, compared with the continuous heat source, the flow stability of discrete heat sources is better with higher and lower inlet subcooling. With a constant sum of heating power, the greater the heating power near the outlet, the better the flow stability.

Experimental and numerical study of turbulent mixed convection in a cavity with an internal heat source

2017 ◽  
Vol 42 (2) ◽  
pp. 142-172
Author(s):  
A Piña-Ortiz ◽  
JF Hinojosa ◽  
JMA Navarro ◽  
J Xamán
Keyword(s):  
Heat Source ◽  
Numerical Study ◽  
Vertical Wall ◽  
Internal Heat ◽  
Turbulence Models ◽  
Internal Heat Source ◽  
Uniform Heat Flux ◽  
Air Conditioning System ◽  
Average Percentage ◽  
Nusselt Numbers

In this study, experimental and numerical results of heat transfer in a ventilated cavity with an internal heat source are presented. The cavity represents a ventilated room with a person inside in a 1:3 scale. It has a vertical wall receiving a constant and uniform heat flux, while the opposite wall is kept at a constant temperature. The rest of the walls is adiabatic. The cavity has multiple inlets and outlets of air, considering ventilation by ducts of an air-conditioning system. Experimental temperature profiles were obtained at six different depths and heights consisting of 14 thermocouples each. Six turbulence models were evaluated against experimental data. The minimum average percentage differences between numerical and experimental average Nusselt numbers of the hot wall and heat source were 12.9% and 4.1% with the renormalized k–ε turbulence model.

scholarly journals The influence of heat source distribution on the space cooling load oriented to local thermal requirements

2019 ◽  
pp. 1420326X1989163
Author(s):  
Chao Liang ◽  
Arsen Krikor Melikov ◽  
Xianting Li
Keyword(s):  
Heat Source ◽  
Source Distribution ◽  
Thermal Plume ◽  
Cooling Load ◽  
Heat Sources ◽  
Local Cooling ◽  
Thermal Requirements ◽  
Space Cooling ◽  
Airflow Field ◽  
Heat Source Distribution

Existing studies have shown that the space cooling load oriented to local thermal requirements is significantly influenced by different heat source distributions. However, numerical methods have been mainly used in the analysis based on a fixed airflow field and ignoring the thermal plume. Here, an experiment in a chamber with mixing ventilation was conducted. The heat sources were simulated by metal barrels and an oil-filled radiator, 13 types of heat source distributions were designed and the local cooling load (LCL) was used as the evaluation index. The results show that (1) the LCL is equal to the total amount of heat sources at the steady state in a room with mixing ventilation only if the heat sources are also distributed uniformly; (2) the LCL decreases with a decrease in the intensity of heat sources, achieving a decrease rate of 47.4%–70.8% in the experiment with different intensities; (3) the LCL is 9.2%–22.3% lower than the total amount of heat sources when these are located near the exhaust diffuser or far away from the target zone; (4) owing to its smaller surface area, the LCL with an oil-filled radiator is 7% lower than that with five metal barrels.

Natural convection far downstream of a heat source on a solid wall

1998 ◽  
Vol 361 ◽  
pp. 25-39 ◽  
Author(s):  
F. J. HIGUERA ◽  
P. D. WEIDMAN
Keyword(s):  
Natural Convection ◽  
Heat Source ◽  
Numerical Solutions ◽  
Solid Wall ◽  
Nonlinear Eigenvalue Problem ◽  
Vertical Wall ◽  
Heat Sources ◽  
Two Dimensional ◽  
Localized Source ◽  
Self Similar

An analysis is presented of some steady natural convection flows at large distances downstream of point heat sources on solid walls. These asymptotic self-similar flows depend only on the Prandtl number of the fluid. The flow induced by a localized source on an adiabatic wall that is vertical or facing downwards is described numerically, whereas the flow due to a localized source on a wall facing upwards separates and leads to a self-similar plume. When the wall is held at the same temperature as the ambient fluid far from the source, the flow is described by a self-similar solution of the second kind, with the algebraic decay of the temperature excess above the ambient temperature determined by a nonlinear eigenvalue problem. Numerical solutions of this problem are presented for two-dimensional and localized heat sources on a vertical wall, whereas the problem for a localized heat source under an inclined isothermal downwards-facing wall turns out to capture the Rayleigh–Taylor instability of the flow and could not be solved by the methods used in this paper. The analogous flows in fluid-saturated porous media are found to be the solutions of parameter-free problems. A conservation law similar to the one holding for a wall jet is found in the case of a two-dimensional source on an isothermal wall and numerical solutions are presented for the other cases.

scholarly journals Forced Convection through Discrete Heat Sources and Simple Thermal Model – A Numerical Study

2019 ◽  
Vol 4 (6) ◽  
pp. 1397-1406
Author(s):  
Kartikaswami Hasavimath ◽  
Kishan Naik ◽  
Banjara Kotresha ◽  
N. Gnanasekaran
Keyword(s):  
Heat Source ◽  
Forced Convection ◽  
Thermal Model ◽  
Conjugate Heat Transfer ◽  
Numerical Study ◽  
Vertical Channel ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Discrete Heat Source ◽  
Bottom Heat

In this work a forced convection through discrete heat sources and simple thermal model placed inside the vertical channel is analyzed numerically. The problem considered for the investigation comprises of a vertical channel with distinct heat source assembly located at the center of the channel. The novelty of the present work is to replace the discrete heat source assembly by a simple thermal model to obtain uniformly distributed temperature and streamlines. A conjugate heat transfer investigation is carried out because the problem domain consists of aluminum solid strips as well as Bakelite strips in discrete heat source assembly which are replaced by a aluminum solid in case of simple thermal model. The numerically obtained data are initially compared with experimental data for the purpose of validation. The temperature of each discrete sources decrease with increase in inlet velocity of the fluid and bottom heat source is able to take higher heat load. The results in terms excess temperature obtained for both discrete heat source and simple thermal model is presented and discussed.

NUMERICAL STUDY OF NATURAL CONVECTION DOMINATED MELTING OF A PCM WITH CONJUGATE FORCED CONVECTION

1995 ◽  
Vol 19 (4) ◽  
pp. 455-469
Author(s):  
M. Lacroix
Keyword(s):  
Thermal Conductivity ◽  
Natural Convection ◽  
Forced Convection ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Melting Process ◽  
Reynolds Numbers ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Convection Dominated

This paper presents a numerical analysis of natural convection dominated melting inside a rectangular enclosure coupled with forced convection heat transfer in a transport fluid via a finite conductance heat exchanging surface. A computational methodology based on a stream function-vorticity-temperature formulation is adopted and the irregular shape of the moving solid-liquid interface is treated with body-fitted coordinates. The model is then employed to investigate the interaction between natural convection in the PCM filled cavity and forced convection in the HTF. Numerical experiments were carried out for Rayleigh numbers, Ra, between 2.08‧108 and 4.60‧109, modified Reynolds numbers, Re between 4.23 and 423.0, wall-PCM thermal diffusivity ratios, α, between 5.0 and 10.0 and dimensionless wall thickness, w, between 0.005 and 0.05. Results show that the melting process is increasingly delayed by heat conduction across a wall of decreasing thermal conductivity and/or increasing thickness. This effect is accentuated for low HTF flow rates (Re ~ 4.23). On the other hand, for a wail of given thickness and thermal conductivity, the effect of increasing the HTF flow rate on the melting process becomes imperceptible for Re ≥ 4.23.

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