Numerical Simulations for Conjugate Heat Transfer from Heat Sources Mounted on a Conductive Wall

2002 ◽  
Vol 2002.15 (0) ◽  
pp. 679-680 ◽  
Author(s):  
Hideo YOSHINO ◽  
Xing ZHANG ◽  
Motoo FUJII
Author(s):  
Mohamed-Nabil Sabry

Thermal stresses developed in electronic systems mainly depend, not only on average temperature values, but rather on wall temperature profiles. These profiles are difficult to predict unless one uses detailed finite element or finite difference modeling and simulation techniques. This type of analysis is only suitable at final design phases were geometrical details are available or being finalized. It is not suitable at early design phases to get a rapid estimate of wall thermal gradients to orient design appropriately. Standard approaches involving correlations for the heat transfer coefficient fail to predict temperature profiles for many reasons. In fact, these correlations depend on temperature profile as an input. In most engineering applications, walls are neither infinitely conducting nor of negligible conductivity to justify the usage of either uniform temperature or uniform heat flux assumptions. Correlations addressing conjugate heat transfer would not be able to solve the problem, unless a large number of them were available covering all possible combinations of fluid and wall conditions. Besides, the case of multiple heat sources, quite common in modern systems, can never be correctly handled by such an approach. The flexible profile technology was proposed earlier to model heat transfer in either solids (conduction) or fluids (forced convection. The model depends on domain (fluid or solid) geometry and physical properties, regardless of the particular set of applied boundary conditions, including that of multiple heat sources. Combining a fluid flexible profile model with a solid one, will allow predicting wall temperature profiles, with an adjustable level of precision, depending on the number of degrees of freedom retained. It will be applied in this paper to predict thermally induced stresses in some simple test cases as a demonstrator of the potentials behind this approach.


Author(s):  
Muhammad M. Rahman ◽  
Phaninder Injeti

Effects of protrusions on heat transfer in a microtube and in a two-dimensional microchannel of finite wall thickness were investigated for various shapes and sizes of the protrusion. Calculations were done for incompressible flow of a Newtonian fluid with developing momentum and thermal boundary layers under uniform and discrete heating conditions. It was found that the local Nusselt number near the protrusions changes significantly with the variations of Reynolds number, height, width, and distance between protrusions, and the distribution of discrete heat sources. The results presented in the paper demonstrate that protrusions can be used advantageously for the enhancement of local heat transfer whereas the global performance may be enhanced or diminished based on the tube geometry.


2021 ◽  
Author(s):  
Louis Christensen ◽  
Richard Celestina ◽  
Spencer Sperling ◽  
Randall Mathison ◽  
Hakan Aksoy ◽  
...  

Abstract Experimental work measuring heat transfer due to internal convection on a smooth straight passage is recreated using unsteady Reynolds averaged Navier-Stokes conjugate heat transfer simulations. The experimental work utilizes 1-dimensional and 3-dimensional conduction models to determine internal heat transfer rates from external surface temperature measurements collected with an infrared camera. The numerical simulations recreated these experiments to verify the conduction model and investigate the differences between the k-ω shear stress transport turbulence model, Reynolds stress turbulence model, and the k-ε turbulence model. It is found that the conduction model can accurately predict the heat transfer in the passage within an average error of 6% but with reduced spatial accuracy. The lower spatial accuracy can be accounted for by utilizing both the conduction model to predict the magnitude of the heat transfer and the numerical simulations to capture the spatial distribution. No one turbulence model was found to provide consistently superior heat transfer predictions, but rather each model excelled in some scenarios and underperformed in others. Overall, the k-ε model was found to best match the experimental heat transfer calculations with an average error of 5.9% of the total heat transfer, and it takes a more conservative approach as it can over predict the external surface temperatures by approximately 0.4 K. The end goal of this study is to develop a way to derive heat-flux data from infrared measurements on a range of geometries. A simple and well-understood geometry is investigated here to provide a firm foundation for future work.


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