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%.

Optimal Distribution of Discrete Heat Sources Under Mixed Convection—A Heuristic Approach

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Tapano Kumar Hotta ◽  
C. Balaji ◽  
S. P. Venkateshan
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Optimal Configuration ◽  
Surface Radiation ◽  
Horizontal Wind ◽  
Maximum Temperature ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Temperature Excess ◽  
Effect Of Surface

Steady state experiments are conducted in a low speed horizontal wind tunnel under mixed convection for five discrete heat sources (aluminum) of nonidentical sizes arranged at different positions on a substrate board (bakelite) to determine the optimal configuration. The optimal configuration is one for which the maximum temperature excess (difference between the maximum temperature among the heat sources of that configuration, and the ambient temperature) is the lowest among all the other possible configurations and is determined by a heuristic nondimensional geometric parameter λ. The maximum temperature excess is found to decrease with λ, signifying an increase in heat transfer coefficient. In view of this, the configuration with highest λ is deemed to be the optimal one. The effect of surface radiation on the heat transfer characteristic of heat sources is also studied by painting their surface with black, which reduces their temperature by as much as 12%. An empirical correlation is developed for the nondimensional maximum temperature excess (θ) in terms of λ, by taking into account the effect of surface radiation. The correlation when applied for highest λ of the configuration returns the minimum value of θ at the optimal condition, which is a key engineering quantity that is sought in problems of this class.

An Experimental Study of Transient Heat Transfer From Discrete Heat Sources in Water Cooled Vertical Rectangular Channel

2004 ◽  
Vol 127 (3) ◽  
pp. 193-199 ◽  
Author(s):  
H. Bhowmik ◽  
K. W. Tou
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Source ◽  
Rectangular Channel ◽  
Convection Heat Transfer ◽  
Uniform Heat Flux ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Wide Range ◽  
Transfer Behavior

Experiments are performed to study the single-phase transient forced convection heat transfer on an array of 4×1 flush-mounted discrete heat sources in a vertical rectangular channel during the pump-on transient operation. Water is the coolant media and the flow covers the wide range of laminar flow regime with Reynolds number, based on heat source length, from 800 to 2625. The applied uniform heat flux ranges from 1 to 7W∕cm2. For flush-mounted heaters the heat transfer characteristics are studied and correlations are presented for four chips as well as for overall data in the transient regime. The experimental results indicate that the heat transfer coefficient is affected strongly by the number of chips and the Reynolds number. Finally the general impacts of heat source protrusions (B=1, 2 mm) on heat transfer behavior of four chips are investigated by comparing the results obtained from flush-mounted (B=0) heaters.

Mixed Convection Heat Transfer From Thermal Sources Mounted on Horizontal and Vertical Surfaces

1990 ◽  
Vol 112 (4) ◽  
pp. 975-987 ◽  
Author(s):  
S. S. Tewari ◽  
Y. Jaluria
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Mixed Convection ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Finite Width ◽  
Heat Sources ◽  
Wide Range ◽  
Thermal Sources

An experimental study is carried out on the fundamental aspects of the conjugate, mixed convective heat transfer from two finite width heat sources, which are of negligible thickness, have a uniform heat flux input at the surface, and are located on a flat plate in the horizontal or the vertical orientation. The heat sources are wide in the transverse direction and, therefore, a two-dimensional flow circumstance is simulated. The mixed convection parameter is varied over a fairly wide range to include the buoyancy-dominated and the mixed convection regimes. The circumstances of pure natural convection are also investigated. The convective mechanisms have been studied in detail by measuring the surface temperatures and determining the heat transfer coefficients for the two heated strips, which represent isolated thermal sources. Experimental results indicate that a stronger upstream heat source causes an increase in the surface temperature of a relatively weaker heat source, located downstream, by reducing its convective heat transfer coefficient. The influence of the upstream source is found to be strongly dependent on the surface orientation, especially in the pure natural convection and the buoyancy dominated regimes. The two heat sources are found to be essentially independent of each other, in terms of thermal effects, at a separation distance of more than about three strip widths for both the orientations. The results obtained are relevant to many engineering applications, such as the cooling of electronic systems, positioning of heating elements in furnaces, and safety considerations in enclosure fires.

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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