scholarly journals Constructal Optimization for Cooling a Non-Uniform Heat Generating Radial-Pattern Disc by Conduction

Entropy ◽  
2018 ◽  
Vol 20 (9) ◽  
pp. 685 ◽  
Author(s):  
Jiang You ◽  
Huijun Feng ◽  
Lingen Chen ◽  
Zhihui Xie
Keyword(s):  
Heat Transfer ◽  
Finite Element Method ◽  
Heat Conduction ◽  
Heat Transfer Performance ◽  
Variable Cross ◽  
Transfer Performance ◽  
Cross Sectional ◽  
Radial Pattern ◽  
Uniform Heat ◽  
Width Coefficient

A heat conduction model in a radial-pattern disc by considering non-uniform heat generation (NUHG) is established in this paper. A series of high conductivity channels (HCCs) are attached on the rim of the disc and extended to its center. Constructal optimizations of the discs with constant and variable cross-sectional HCCs are carried out, respectively, and their maximum temperature differences (MTDs) are minimized based on analytical method and finite element method. Besides, the influences of the NUHG coefficient, HCC number and width coefficient on the optimal results are studied. The results indicate that the deviation of the optimal constructs obtained from the analytical method and finite element method are comparatively slight. When the NUHG coefficient is equal to 10, the minimum MTD of the disc with 25 constant cross-sectional HCCs is specifically reduced by 48.8% compared to that with 10 HCCs. As a result, the heat conduction performance (HCP) of the disc can be efficiently improved by properly increasing the number of HCCs. The minimum MTD of the disc with variable cross-sectional HCC is decreased by 15.0% when the width coefficient is changed from 1 to 4. Therefore, the geometry of variable cross-sectional HCC can be applied in the constructal design of the disc to a better heat transfer performance. The constructal results obtained by investigating the non-uniform heat generating case in this paper can contribute to the design of practical electronic device to a better heat transfer performance.

Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms

2015 ◽  
Vol 17 (25) ◽  
pp. 16476-16482 ◽  
Author(s):  
Liu Cui ◽  
Yanhui Feng ◽  
Peng Tan ◽  
Xinxin Zhang
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Heat Conduction ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Reduction Mechanisms ◽  
Double Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Theoretical insights into the heat transfer performance and its reduction mechanisms in double-walled carbon nanotubes with intertube additional carbon atoms.

Thermo-Fluid Dynamic Design Exploration of a Double Pipe Heat Exchanger

2019 ◽  
Author(s):  
Tomohiro Hirano ◽  
Mitsuo Yoshimura ◽  
Koji Shimoyama ◽  
Atsuki Komiya
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Nsga Ii ◽  
Cross Sectional ◽  
Average Temperature ◽  
Double Pipe ◽  
Sectional Shape ◽  
Pipe Heat

Abstract Toward a practical application of the additive manufacturing (AM), this study proposes a shape optimization approach for the cross-sectional shape of the inner pipe of a counter-flow double pipe heat exchanger. The cross-sectional shape of the inner pipe is expressed by an algebraic expression with a small number of parameters, and their heat transfer performance is evaluated by a commercial Computational Fluid Dynamics (CFD) solver. The optimization is conducted by the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) assisted by the Kriging surrogate model, and the NSGA-II finds the optimal cross-sectional shape with many protrusions around the perimeter of the inner channel to improve the heat transfer performance. In this study, heat transfer performance is evaluated from the temperature drop at the outlet of the high-temperature fluid. Through the comparison of two cross-sectional shapes with the same heat transfer surface area — average temperature at the outlet of the optimal high-temperature channel is 324.58 K while average temperature at the outlet of a circular high-temperature channel with the same area as the optimal channel is 331.93 K, it is revealed that the number of protrusions plays important roles which contribute not only to increase heat transfer area but also to improve heat transfer performance.

scholarly journals MHD Heat Transfer in W-Shaped Inclined Cavity Containing a Porous Medium Saturated with Ag/Al2O3 Hybrid Nanofluid in the Presence of Uniform Heat Generation/Absorption

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3457 ◽  
Author(s):  
Mohamed Dhia Massoudi ◽  
Mohamed Bechir Ben Hamida ◽  
Hussein A. Mohammed ◽  
Mohammed A. Almeshaal
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Aspect Ratio ◽  
Heat Generation ◽  
Heat Transfer Performance ◽  
Convection Heat Transfer ◽  
Hybrid Nanofluid ◽  
Transfer Performance ◽  
Convection Heat ◽  
Uniform Heat

In this paper, a 2D numerical study of natural convection heat transfer in a W-shaped inclined enclosure with a variable aspect ratio was performed. The enclosure contained a porous medium saturated with Ag/Al2O3 hybrid nanofluid in the presence of uniform heat generation or absorption under the effect of a uniform magnetic field. The vertical walls of the enclosure were heated differentially; however, the top and bottom walls were kept insulated. The governing equations were solved with numerical simulation software COMSOL Multiphysics which is based on the finite element method. The results showed that the convection heat transfer was improved with the increase of the aspect ratio; the average Nusselt number reached a maximum for an aspect ratio (AR) = 0.7 and the effect of the inclination was practically negligible for an aspect ratio of AR = 0.7. The maximum heat transfer performance was obtained for an inclination of ω = 15 and the minimum is obtained for ω = 30 . The addition of composite nanoparticles ameliorated the convection heat transfer performance. This effect was proportional to the increase of Rayleigh and Darcy numbers, the aspect ratio and the fraction of Ag in the volumetric fraction of nanoparticles.

Influence of Brazing on the Heat Transfer Performance of Fins in Radiators

2000 ◽  
Author(s):  
Bengt Sundén ◽  
Andreas Abdon ◽  
Daniel Eriksson
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Detrimental Effect ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Two Dimensional ◽  
Air Gaps ◽  
One Dimensional ◽  
Temperature Distributions ◽  
Braze Joint

Abstract The performance of a radiator copper fin is considered as the braze joint between the fin and the brass tube is not perfect. The influence of different thermophysical properties of the brazing materials, created intermetallic compounds and possible air gaps is considered. Numerical methods for both two-dimensional and one-dimensional calculations have been developed. The finite volume technique is applied and in the two-dimensional case, boundary fitted coordinates are used. Heat conduction in the fin and braze joint coupled with convective heat transfer in a gas stream is analysed. Results in terms of fin temperature distributions and fin efficiencies are provided. It is found that the detrimental effect of a poor braze joint is not as large as reported previously in the literature.

Enhanced Flow Boiling Heat Transfer Using Radial Microchannels

2016 ◽  
Author(s):  
Alyssa Recinella ◽  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Flow Boiling ◽  
Cross Sectional Area ◽  
Working Fluid ◽  
Transfer Performance ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Flow Cross

Flow boiling has the ability to remove high heat fluxes while maintaining a low wall superheat. Various researchers have developed enhanced microchannel geometries to improve the heat transfer performance of the system. Recently, a number of new studies have used the increasing flow cross-sectional area concept to overcome flow instabilities and record high CHF. In this work, a new geometry is experimentally investigated utilizing a radial cross-section, which provides the increasing fluid flow cross-sectional area in the flow direction. The flow boiling performance is studied using radial microchannels and water as the working fluid. Four different flow rates ranging from 120–400 mL/min are studied for this new geometry. Heat transfer performance (boiling curve and heat transfer coefficient) and pressure drop characteristics are discussed for all flow rates. Furthermore, the work is supported by high speed visualization of the bubble dynamics. The boiling performance obtained is compared to the existing data in the literature.

Heat Conduction Effect on Oscillating Heat Pipe Operation

2011 ◽  
Author(s):  
C. D. Smoot ◽  
H. B. Ma ◽  
C. Wilson ◽  
L. Greenberg
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Block Design ◽  
Transfer Performance ◽  
Copper Block ◽  
Oscillating Heat Pipe ◽  
Continuous Block ◽  
Adiabatic Section

The effect of heat conduction through the adiabatic section on the oscillating motion and heat transfer performance in an oscillating heat pipe (OHP) was investigated experimentally. Two, closed loop, 6-turn OHPs were constructed; one with a separate copper block for the evaporator and condenser sections (split block design) and one using a single continuous copper block for the evaporator, adiabatic, and condenser sections (continuous block design). The results show that the presence of heat conduction directly from the evaporator wall to the adiabatic section and from the adiabatic section to the condenser of a heat pipe will reduce the oscillating amplitude of the evaporator, adiabatic, and condenser temperatures. It was also found that in addition to a higher level of temperature uniformity, the continuous block design results in better heat transfer performance than a heat pipe without conduction through the adiabatic section.

Thermal Analysis in Phase Change Materials (PCMs) Embedded With Metal Foams

2010 ◽  
Author(s):  
Y. Tian ◽  
C. Y. Zhao
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Natural Convection ◽  
Heat Transfer Enhancement ◽  
Flow Resistance ◽  
Phase Change Materials ◽  
Heat Transfer Performance ◽  
Metal Foams ◽  
Transfer Performance ◽  
Transfer Enhancement

The heat transfer enhancement for phase change materials (PCMs) has received increasing attention nowadays, since most of PCMs have low thermal conductivities which prolong the charging and discharging processes. Metal foams, as a sort of novel material with high thermal conductivity, are believed to be a promising solution to enhance the heat transfer performance of PCMs for thermal energy storage systems. The effects of natural convection on heat transfer enhancement for PCMs embedded with metal foams are investigated in this paper. The numerical investigation is based on the two-equation non-equilibrium heat transfer model, where the coupled heat conduction and natural convection in PCMs are considered at phase transition and liquid zones. The numerical results are validated by experimental data. In order to investigate the effect of metal foams on heat transfer, two different cases are compared in this study, which are the Case A (PCMs embedded with metal foams) and the Case B (pure PCMs). At the solid zone, heat conduction plays a dominant part because of natural convection’s absence, thus metal foams achieve much higher heat conduction rate than pure PCMs, and this can be attributed to the high thermal conductivity of metal foams skeleton and the heat can be quickly transferred through the foam solid structure to the whole domain of PCMs. At the two-phase zone and liquid zone, natural convection takes place and becomes the dominant heat transfer mode, but metal foam structures suppress the natural convection inside the PCMs owing to big flow resistance in metal foams. In spite of this suppression caused by metal foams, the overall heat transfer performance of Case A is still superior to the counterpart of Case B (pure PCMs), implying the enhancement of heat conduction offsets or exceeds the natural convection loss. The results show that the heat transfer enhancement due to the natural convection in PCMs embedded with metal foams is not as strong as expected, since metal foams have big flow resistance and the natural convection is suppressed. It also shows that better heat transfer performance can be achieved by using the metal foams of smaller porosity and bigger pore density. Last but not least, a series of detailed velocity and temperature profiles are given through numerical solutions, in order to present a vivid evolution of flow field and temperature profiles in the whole melting process.

scholarly journals Heat Transfer Enhancement of Indirect Heat Transfer Reactors for Ca(OH)2/CaO Thermochemical Energy Storage System

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1136
Author(s):  
Boyan Wang ◽  
Zhiyuan Wang ◽  
Yan Ma ◽  
Yijing Liang
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Energy Storage ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Transfer Performance ◽  
Storage System ◽  
Energy Storage System ◽  
Transfer Performance ◽  
Pin Fin

The efficiency of a thermochemical energy storage system can be improved by optimizing the structure of the thermochemical energy storage reactor. We proposed two modified structures for indirect heat transfer thermochemical energy storage reactors for a Ca(OH)2/CaO system to improve their heat transfer performance. Our results showed that improving convective heat transfer offered varying effects on heat transfer performance in different reaction processes. For a half-plate pin fin sinks (HPPFHS) reactor and a plate pin fin sinks (PPFHS) reactor, enhancing the convective heat transfer process could improve the heat transfer performance in the dehydration process for a porosity of 0.5, and the time needed to complete reaction was reduced by around 33% compared with plate fin sinks (PFHS) reactor. As for the hydration process, because heat conduction along the bed dominated heat transfer performance, this method had little effect. Furthermore, we found that enhancing heat conduction along the bed and convective heat transfer had different effects on reaction process at different reaction areas. The HPPFHS reactor had a lower pressure drop along the HTF channel and exorbitant velocity of heat transfer fluid (HTF) was unnecessary. Under the condition of the bed porosity of 0.8, due to the lower thermal conductivity of material, both modified reactor structures had little effect on dehydration. However, because the temperature difference between bed and HFT was bigger, the PPFHS reactor could reduce the time of completing the hydration reaction by 20%. Above all, when planning to modify the reactor structure to improve the heat transfer performance to enhance the reaction process, the heat conditions along the bed, convective heat transfer between HTF and the bed and material parameters should be considered totally.

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