Conjugate Thermal Analysis of Air-Cooled Discrete Flush-Mounted Heat Sources in a Horizontal Channel

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Jing He ◽  
Liping Liu ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Hot Spot ◽  
Horizontal Channel ◽  
Bottom Surface ◽  
Comprehensive Treatment ◽  
Heat Sources ◽  
Surface Emissivity ◽  
Thick Substrate ◽  
Uniform Temperature Field

Thermal analysis with comprehensive treatment of conjugate heat transfer is performed in this study for discrete flush-mounted heat sources in a horizontal channel cooled by air. The numerical model accounts for mixed convection, radiative exchange and two-dimensional conduction in the substrate. The model is first used to simulate available experimental work to demonstrate its accuracy and practical utility. A parametric study is then undertaken to assess the effects of Reynolds number, surface emissivity of walls and heat sources, as well as thickness and thermal conductivity of substrate, on flow field and heat transfer characteristics. It is shown that due to radiative heat transfer, the wall temperatures are brought closer, and the trend of temperature variation along the top wall is significantly altered. Such effects are more pronounced for higher surface emissivity and/or lower Reynolds numbers. The influence of substrate conductivity and thickness is related in that a large value of either substrate conductivity or thickness facilitates redistribution of heat and tends to yield a uniform temperature field in the substrate. For highly conductive or thick substrate, the “hot spot” cools down and may occur in upstream sources. Radiation loss to the ambient increases with substrate conductivity and thickness due to the elevated temperature near the openings, yet the total heat transfer over the bottom surface by convection and radiation remains essentially unaltered.

Conjugate Mixed Convection With Surface Radiation and Substrate Conduction in Laminar Channel Flow With Discrete Flush-Mounted Heat Sources

2010 ◽  
Author(s):  
Jing He ◽  
Anthony M. Jacobi
Keyword(s):  
Mixed Convection ◽  
Hot Spot ◽  
Surface Radiation ◽  
Bottom Surface ◽  
Heat Sources ◽  
Thick Substrate ◽  
Laminar Channel Flow ◽  
Uniform Temperature Field ◽  
Influence Of Substrate ◽  
High Reynolds

Thermal analysis employing a full conjugation model is performed in this study for laminar airflow in a parallel-plate channel with discrete flush-mounted heat sources. The numerical model accounts for mixed convection, surface radiation, and two-dimensional conduction in the substrate. The effects of Reynolds number, surface emissivity of walls and heat sources, as well as thickness and thermal conductivity of the substrate, are analyzed in detail. It is shown that participation of radiation brings the wall temperatures closer, and the trend of temperature variation along the top wall is drastically altered. Such effects are pronounced for black enclosures and diminished for high Reynolds numbers. The influence of substrate conductivity and thickness is very similar in that a large value for both parameters would facilitate redistribution of heat and tend to yield a uniform temperature field in the substrate. For highly conductive or thick substrate, the ‘hot spot’ cools down and may move upstream to the penultimate source. Radiation loss to the ambient increases with substrate conductivity and thickness due to the elevated temperature near the inlet and outlet, yet the total heat transfer over the bottom surface by convection and radiation remains unaltered.

Conjugate Mixed Convection With Surface Radiation and Substrate Conduction in Laminar Channel Flow With Discrete Flush-Mounted Heat Sources

2010 ◽  
Author(s):  
Jing He ◽  
Anthony M. Jacobi
Keyword(s):  
Mixed Convection ◽  
Hot Spot ◽  
Surface Radiation ◽  
Bottom Surface ◽  
Heat Sources ◽  
Thick Substrate ◽  
Laminar Channel Flow ◽  
Uniform Temperature Field ◽  
Influence Of Substrate ◽  
High Reynolds

Thermal analysis employing a full conjugation model is performed in this study for laminar airflow in a parallel-plate channel with discrete flush-mounted heat sources. The numerical model accounts for mixed convection, surface radiation, and two-dimensional conduction in the substrate. The effects of Reynolds number, surface emissivity of walls and heat sources, as well as thickness and thermal conductivity of the substrate, are analyzed in detail. It is shown that participation of radiation brings the wall temperatures closer, and the trend of temperature variation along the top wall is drastically altered. Such effects are pronounced for black enclosures and diminished for high Reynolds numbers. The influence of substrate conductivity and thickness is very similar in that a large value for both parameters would facilitate redistribution of heat and tend to yield a uniform temperature field in the substrate. For highly conductive or thick substrate, the ‘hot spot’ cools down and may move upstream to the penultimate source. Radiation loss to the ambient increases with substrate conductivity and thickness due to the elevated temperature near the inlet and outlet, yet the total heat transfer over the bottom surface by convection and radiation remains unaltered.

Constructal Placement of Discrete Heat Sources With Different Lengths in Vertical Ducts Under Natural and Mixed Convection

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Bugra Sarper ◽  
Mehmet Saglam ◽  
Orhan Aydin
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Hot Spot ◽  
Experimental Studies ◽  
Vertical Channel ◽  
Working Fluid ◽  
Heat Sources ◽  
Ansys Fluent ◽  
Cooling Performance ◽  
Spot Temperature

In this study, convective heat transfer in a discretely heated parallel-plate vertical channel which simulates an IC package is investigated experimentally and numerically. Both natural and mixed convection cases are considered. The primary focus of the study is on determining optimum relative lengths of the heat sources in order to reduce the hot spot temperature and to maximize heat transfer from the sources to air. Various values of the length ratio and the modified Grashof number (for the natural convection case)/the Richardson number (for the mixed convection case) are examined. Conductive and radiative heat transfer is included in the analysis while air is used as the working fluid. Surface temperatures of the heat sources and the channel walls are measured in the experimental study. The numerical studies are performed using a commercial CFD code, ANSYS fluent. The variations of surface temperature, hot spot temperature, Nusselt number, and global conductance of the system are obtained for varying values of the working parameters. From the experimental studies, it is showed that the use of identical heat sources reduces the overall cooling performance both in natural and mixed convection. However, relatively decreasing heat sources lengths provides better cooling performance.

scholarly journals Longevity and power density of intermediate-to-deep geothermal wells in district heating applications

2021 ◽  
Vol 136 (1) ◽  
Author(s):  
Eero Hirvijoki ◽  
David Pfefferlé ◽  
Manasvi Lingam
Keyword(s):  
Heat Transfer ◽  
Power Density ◽  
Large Scale ◽  
Hot Spot ◽  
District Heating ◽  
Heat Sources ◽  
Heating Systems ◽  
District Heating Systems ◽  
Geothermal Wells ◽  
The City

AbstractThis paper assesses the potential of intermediate-to-deep geothermal wells for district heating purposes in non-hot spot regions as a means for replacing carbon-intensive heat sources. In analysing the problem of heat transfer from the bedrock to a flowing coolant in the well, we perform parameter scans to assess the longevity and power density of different-size wells and derive analytical estimates to explain salient characteristics of the well behaviour. The results are then utilized to illustrate how intermediate-to-deep geothermal wells would compare with the requirements of typical large-scale district heating systems, by using the city of Helsinki in Finland as an example.

Underhood Fluid Flow and Thermal Analysis for Passenger Vehicle

2012 ◽  
Vol 165 ◽  
pp. 150-154 ◽  
Author(s):  
Yusoff Lukeman ◽  
Fang Yau Lim ◽  
Shahrir Abdullah ◽  
Zulkifli R. ◽  
A. Shamsudeen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Fluid Flow ◽  
Hot Spot ◽  
Three Dimensional ◽  
Constant Density ◽  
Passenger Vehicle ◽  
Heat Transfer Efficiency ◽  
Segregated Flow ◽  
Air Intake

The present paper reports a simulation study of the fluid flow and thermal phenomena in the passenger vehicle underhood compartment by analysing velocity magnitude, temperature, radiator heat transfer rate and heat transfer efficiency. Analyses are carried out on a half cut passenger vehicle sample model by using commercial computational fluid dynamics (CFD) software, Star CCM+. Total volume meshes of the model are 24 451 759 cells, and the speed of the car is 0.036, 40, 70, 110, 130 and 213 km/h. Investigation are performed for three dimensional conditions, steady state gas with segregated flow, constant density, turbulence flow, with the use of the Reynolds-Averaged Navier-Stokes model and the K-Epsilon turbulence model. In the thermal analysis, particular attention is given to find hot spot locations under the hood. . High temperature region is observed at the right side of the hood (from the top of view) due primary heat sources from the engine. An air intake at hood is introduced in order to facilitate the airflow to engine room and to remove hot spot to the atmosphere. It is shown that the underhood average temperature decreases by 26.2% and the average airflow velocity at section plane of the centreline increases by 14.5% by adding this air intake.

Problem of the Variability of Substitute Thermo-Physical Properties for Heat Transfer Modelling in Iso- and Iso-Exo Porous Materials

2009 ◽  
Vol 283-286 ◽  
pp. 376-381 ◽  
Author(s):  
Zenon Ignaszak ◽  
Paweł Popielarski
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Solution Procedure ◽  
Problem Solution ◽  
Heat Sources ◽  
Inverse Problem Solution ◽  
Thermophysical Parameters ◽  
Transfer Modelling ◽  
Materials Used ◽  
Thermo Physical Properties

In foundry technology the modeling of heat transfer in materials containing exothermic components must take into consideration the presence of heat sources in the Fourier–Kirchhoff equation. The aim of this investigation was the identification of real and effective thermophysical parameters of the insulating and insulating –exothermic materials used as riser sleeves containing these exothermic heat sources. The experiments of liquid steel or cast iron pouring into the mould, containing different insulating and exothermic sleeves were carried out, using thermocouples meas-urement systems (thermal analysis of casting–mould system). Then the thermo-physical coefficients of these materials were calculated using inverse problem solution. The numerical system Calcosoft and its Inverse Solution procedure were applied.

A Multi-Grid Based Multi-Scale Thermal Analysis Approach for Combined Mixed Convection, Conduction, and Radiation Due to Discrete Heating

2005 ◽  
Vol 127 (1) ◽  
pp. 18-26 ◽  
Author(s):  
Lan Tang ◽  
Yogendra K. Joshi
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Mixed Convection ◽  
Single Step ◽  
Heat Transfer Analysis ◽  
Heat Sources ◽  
Length Scales ◽  
Multi Scale ◽  
Discrete Heat Sources ◽  
Wide Range

A multi-grid embedded multi-scale approach is presented for conjugate heat transfer analysis of systems with a wide range of length scales of interest. The multi-scale analysis involves a sequential two-step “zoom-in” approach to resolve both the large length scales associated with the system enclosure, and the smaller length scales associated with fine spatial structures of discrete heat sources contained within. With this approach, computation time is shortened significantly, compared to conventional single-step computational fluid dynamics/computational heat transfer (CFD/CHT) modeling, with a very fine mesh. Performance of the two-step multi-scale approach is further enhanced by integrating the multi-grid technique in the CFD/CHT solver. Implementation of the enhanced approach is demonstrated for thermal analysis of an array of substrate mounted discrete heat sources cooled by mixed and forced convection, with accompanying experiments performed for validation and for the assessment of the importance of mixed convection. It is found that the multi-grid embedded multi-scale thermal analysis reduces simulation run time by 90% compared to the multi-grid integrated single step solution. The computed temperatures were in good agreement with measurements, with maximum deviation of 8%.

A Multigrid Based Multi-Scale Thermal Analysis Approach for Conjugate Problems Involving Discrete Heating

2003 ◽  
Author(s):  
Lan Tang ◽  
Yogendra K. Joshi
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Computation Time ◽  
Analysis Approach ◽  
Length Scale ◽  
Heat Sources ◽  
Scale Analysis ◽  
Time Saving ◽  
Multi Scale ◽  
Multi Scale Analysis

A multi-grid enhanced multi-scale analysis approach is presented for conjugate heat transfer systems with a large range of length scales of interest. The multi-scale analysis involves a sequential two-step “zoom-in” approach to resolve both the large length scale associated with the enclosure and the smaller length scale associated with fine spatial structures of heat sources. Significant computation time saving with this approach is realized compared to conventional computational fluid dynamics/computational heat transfer (CFD/CHT) modeling. Performance of the multi-scale approach is further enhanced by integrating the multi-grid technique as the CFD/CHT solver. Implementation of the enhanced approach is demonstrated for the thermal analysis of an array of discrete heat sources cooled by mixed and forced convection. It is found that the multi-grid enhanced multi-scale thermal analysis reduces simulation run time by 90% compared to multi-grid with SIMPLER. And the temperatures computed from the approach are in good agreement with measurements, deviate by no more than 8% from measurements.

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