scholarly journals Effect of heater size on heat transfer in a falling liquid film

2021 ◽  
pp. 50-55
Author(s):  
В.В. Кузнецов
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Analytical Formula ◽  
Temperature Fields ◽  
Maximum Temperature ◽  
Physical Factors ◽  
Thermocapillary Effect ◽  
Average Value ◽  
Surface Deformations ◽  
Falling Liquid Film

Проведены расчеты полей скорости и температуры, а также положение границы раздела жидкость-газ при стекании тонкой пленки жидкости по плоской подложке, наклоненной к горизонту. На подложке расположен нагреватель квадратной формы, мощность которого фиксирована, а размеры варьировались в ходе расчетов:- одним из перспективных методов отвода высоких тепловых потоков от электронного оборудования являются технологии, использующие тонкие пленки жидкости, движущиеся по охлаждаемой поверхности. Целью работы было исследование зависимости динамики и теплообмена в пленки от размера нагревателя;- на основе разработанной трехмерной нестационарной модели движения проведены расчеты теплообмена в движущейся поенке. При этом учитывалось действие всех основных физческих факторов при их взаимодействии: диффузионный и конвективный теплопереносы, зависимость вязкости от температуры, термокапиллярный эффект, появление и эволюция поверхностных деформаций;- установлено, что размер нагревателя существенно влияет на поля температуры и поверхностные деформации, а также на значение температурных экстремумов. Выведена аналитическая формула для расчета наибольшего достигаемого на подложке превышения температуры её среднего значения;- результаты могут применяться при проектировании систем охлаждения электронного оборудования. On the basis of the developed three-dimensional non-stationary model of motion, calculations of heat transfer in a moving roll were carried out. In this case, the action of all the main physical factors during their interaction was taken into account: diffusion and convective heat transfer, the dependence of viscosity on temperature, the thermocapillary effect, the appearance and evolution of surface deformations.  it was found that the size of the heater significantly affects the temperature fields and surface deformations, as well as the value of temperature extremes. An analytical formula is derived for calculating the maximum temperature rise attainable on the substrate of its average value.

Effect of Periodic Imposed Heat Flux on Three-Dimensional Natural Convection in a Partially Heated Cubical Enclosure

2016 ◽  
Vol 831 ◽  
pp. 83-91
Author(s):  
Lahoucine Belarche ◽  
Btissam Abourida
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Maximum Temperature ◽  
Cubical Enclosure ◽  
Simplec Algorithm ◽  
Volume Method

The three-dimensional numerical study of natural convection in a cubical enclosure, discretely heated, was carried out in this study. Two heating square sections, similar to the integrated electronic components, are placed on the vertical wall of the enclosure. The imposed heating fluxes vary sinusoidally with time, in phase and in opposition of phase. The temperature of the opposite vertical wall is maintained at a cold uniform temperature and the other walls are adiabatic. The governing equations are solved using Control volume method by SIMPLEC algorithm. The sections dimension ε = D / H and the Rayleigh number Ra were fixed respectively at 0,35 and 106. The average heat transfer and the maximum temperature on the active portions will be examined for a given set of the governing parameters, namely the amplitude of the variable temperatures a and their period τp. The obtained results show significant changes in terms of heat transfer, by proper choice of the heating mode and the governing parameters.

Cooling of Concentrator Photovoltaic Cells Using Mini-Scale Jet Impingement Heat Sinks

2018 ◽  
Author(s):  
Ali Radwan ◽  
Meshack Hawi ◽  
Mahmoud Ahmed
Keyword(s):  
Heat Transfer ◽  
Flow Model ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Heat Sinks ◽  
Maximum Temperature ◽  
Transfer Model ◽  
Cell Temperature ◽  
Maximum Cell ◽  
T System

In this study, an efficient cooling technique for concentrator photovoltaic (CPV) cells is proposed to enhance the system electrical efficiency and extend its lifetime. To do this, a comprehensive three-dimensional conjugate heat transfer model of CPV cells layers coupled with the heat transfer and fluid flow model inside jet impingement heat sink is developed. Four different jet impingement designs are compared. The investigated designs are (A) central inlet jet, (B) Hypotenuse inlet jet, (C) staggered inlet jet, and (D) conventional jet impingement design with side drainage. The effect of coolant flowrate on the CPV/T system performance is investigated. The model is numerically simulated and validated using the available experiments. The performance of CPV system is investigated at solar concentration ratios of 20 and coolant flowrate up to 6000g/min. It is found that increasing the flowrate from 60 g/min to 600 g/min decrease the maximum cell temperature by 31°C for the configuration D while increasing the flowrate from 600 g/min to 6000 g/min reduce the cell temperature by 20.2°C. It is also concluded that at a higher flowrate of 6000g/min, all the investigated configurations relatively achieve better temperature uniformity with maximum temperature differences of 0.9 °C, 2.1 °C, 3.6 °C, and 3.9 °C for configurations A, B, C, and D respectively.

scholarly journals Optimizing air velocity for the underfloor forced ventilation to protect a refrigerated warehouse from frost heaving

2018 ◽  
Vol 38 (3) ◽  
pp. 321-327
Author(s):  
Jingfu Jia ◽  
Manjin Hao ◽  
Jianhua Zhao
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Frost Heave ◽  
Forced Ventilation ◽  
Air Velocity ◽  
Set Up

Forced or natural ventilation is the most common measure of frost heave protection for refrigerated warehouse floor. To optimize air velocity for the underfloor forced ventilation system of refrigerated warehouse, a steady state three-dimensional mathematical model of heat transfer is set up in this paper. The temperature fields of this system are simulated and calculated by CFD software PHOENICS under different air velocity, 1.5m/s, 2.5m/s or 3.5m/s. The results show that the optimized air velocity is 1.5m/s when the tube spacing is 1.5m.

Three-Dimensional Modelling of Heat Transfer in Micro-Channels With Synthetic Jet

2010 ◽  
Author(s):  
Ann Lee ◽  
Victoria Timchenko ◽  
Guan H. Yeoh ◽  
John A. Reizes
Keyword(s):  
Heat Transfer ◽  
Silicon Substrate ◽  
Three Dimensional ◽  
Synthetic Jet ◽  
Numerical Results ◽  
Maximum Temperature ◽  
Complex Conjugate ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Micro Channels

An in-house computer code is developed and applied to investigate the effect of a synthetic jet on heat transfer rates in forced convection of water in silicon micro-channels etched in the rear side of the silicon substrate. To account for the deflection of the membrane located at the bottom of the actuator cavity, a moving mesh technique to solve the flow and heat transfer is purposefully adopted. The governing equations are transformed into the curvilinear coordinate system in which the grid velocities evaluated are then fed into the computation of the flow in the cavity domain thus allowing the conservation equations of mass, momentum and energy to be solved within the stationary computational domain. The fully three-dimensional model considers the SIMPLE method to link the pressure and velocity. A heat flux of 1 MW/m2 is applied at the surface of the top of the silicon wafer and the resulting complex, conjugate heat transfer through the silicon substrate is included. The hydrodynamics feature of the flow is validated against existing experimental results and verified against numerical results from commercial package ANSYS CFX 11.0. Good agreement has been achieved. To track the development of the flow and heat transfer when the actuator is switched on, numerical results of 20 full cycles of the actuator are simulated. When the actuator is switched on, noticeable temperature drop is observed at all points in the substrate from those which existed when there has been a steady water flow in the channel. At the end of 20th cycle of actuation, the maximum temperature in the wafer has reduced by 5.4 K in comparison with the steady flow values. In comparison with the two-dimensional study which account for 17K reduction, it indicates that synthetic jet has only smaller beneficial cooling and has been over-estimated in the previous two-dimensional study.

Three-Dimensional Finite Element Analysis on Heavy Cutting for High Strength Steel

2013 ◽  
Vol 274 ◽  
pp. 3-6 ◽  
Author(s):  
Yuan Sheng Zhai ◽  
Xian Li Liu ◽  
Yu Wang
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Feed Rate ◽  
Cutting Forces ◽  
High Strength Steel ◽  
Three Dimensional ◽  
High Strength ◽  
Temperature Fields ◽  
Maximum Temperature ◽  
Element Modeling

The finite element modeling and experimental validation of three-dimensional heavy cutting of high strength steel (2.25Cr-1Mo-0.25V) are presented. The commercial software Deform 3D applied for the finite element modeling is studied the effect of feed rate on the principal cutting forces and the temperature fields. The friction between the tool and the chip is assumed to follow a shear model and the local adaptive remeshing technique is used for the formation of chip. The feed rate significantly affects the cutting forces, but slightly influences the maximum temperature of the chip. The simulation results are compared with experimental data and found to be in good agreement.

Numerical Analysis on the Temperature Field in Laser-Plasma Hybrid Welding of an Aluminum Alloy

2008 ◽  
Vol 580-582 ◽  
pp. 279-282
Author(s):  
Zhi Ning Li ◽  
Bao Hua Chang ◽  
Dong Du ◽  
Hua Zhang
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Laser Plasma ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Transfer Model ◽  
Heat Sources ◽  
Hybrid Welding ◽  
Plasma Arc ◽  
Simulation Results

A three dimensional heat transfer model on laser-plasma hybrid welding has been proposed, that takes into account the interaction between laser beam and plasma arc. Through FEM computation, the temperature fields were computed and analyzed for an Al-Li alloy during laserplasma hybrid welding with different distances between the two heat sources. The simulation results are in agreement with the experimental results.

scholarly journals Laser interferometry - Report #HT-01-2017

2021 ◽  
Author(s):  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Light Beam ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Laser Interferometry ◽  
Local Heat ◽  
Temperature Fields ◽  
Fluid Temperature ◽  
Two Dimensional ◽  
Transfer Rates

An introduction is given to the optical setup and principle of operation of classical and holographic interferometers that are used for convective he at transfer measurements. The equations for the evaluation of the temperature field are derived and methods of analysis are discussed for both two-dimensional and three-dimensional temperature fields. Emphasis is given to techniques for measuring local heat transfer rates. For two-dimensional fields, a method is presented for measuring the surface temperature gradient directly from a finite (wedge) fringe interferogram. This “direct gradient method” is shown to be most useful for the measurement of low convective heat transfer rates. For three-dimensional fields, the equations for calculating the beam-averaged local heat flux are presented. The measurement of the fluid temperature averaged along the light beam is shown to be approximate. However, an analysis is presented showing that for most cases the error associated with temperature variations in the light beam direction is small. Digital image analysis of interferograms to obtain fringe spacings is also discussed briefly.

scholarly journals Analysis of the efficiency of an embedded floor heating for snow melting and freeze protection

2020 ◽  
Vol 207 ◽  
pp. 01008
Author(s):  
Nina Penkova ◽  
Merima Zlateva ◽  
Boian Mladenov
Keyword(s):  
Heat Transfer ◽  
Design Method ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Snow Melting ◽  
Climate Conditions ◽  
The Road ◽  
Flow Parameters ◽  
Road Surfaces ◽  
Volume Method

An algorithm for modelling and numerical simulation of the three dimensional conjugate heat transfer in slab-embedded snow melting and freeze protecting systems is developed. The influence of the climate conditions on the heat transfer in the constructions is modelled according to the correspondent design method of ASHRAE. The models are verified and solved numerically via finite volume method for a road embedded hydronic installation at different piping configurations. The fluid flow parameters and temperature fields in the construction are obtained at steady state climate conditions, hardest for 95 % of the wintertime for the region. An analysis of the efficiency of the modelled configurations is implemented based on the computed snow-free area ratio of the road surfaces.

Direct Numerical Simulation of Flow and Heat Transfer From a Sphere in a Uniform Cross-Flow

2000 ◽  
Vol 123 (2) ◽  
pp. 347-358 ◽  
Author(s):  
P. Bagchi ◽  
M. Y. Ha ◽  
S. Balachandar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Vortex Shedding ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Temperature Fields ◽  
Flow And Heat Transfer

Direct numerical solution for flow and heat transfer past a sphere in a uniform flow is obtained using an accurate and efficient Fourier-Chebyshev spectral collocation method for Reynolds numbers up to 500. We investigate the flow and temperature fields over a range of Reynolds numbers, showing steady and axisymmetric flow when the Reynolds number is less than 210, steady and nonaxisymmetric flow without vortex shedding when the Reynolds number is between 210 and 270, and unsteady three-dimensional flow with vortex shedding when the Reynolds number is above 270. Results from three-dimensional simulation are compared with the corresponding axisymmetric simulations for Re>210 in order to see the effect of unsteadiness and three-dimensionality on heat transfer past a sphere. The local Nusselt number distribution obtained from the 3D simulation shows big differences in the wake region compared with axisymmetric one, when there exists strong vortex shedding in the wake. But the differences in surface-average Nusselt number between axisymmetric and three-dimensional simulations are small owing to the smaller surface area associated with the base region. The shedding process is observed to be dominantly one-sided and as a result axisymmetry of the surface heat transfer is broken even after a time-average. The one-sided shedding also results in a time-averaged mean lift force on the sphere.

Laminar Mixed Convection in the Entrance Region of a Helical Pipe

1999 ◽  
Author(s):  
B. Zheng ◽  
C. X. Lin ◽  
M. A. Ebadian
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Control Volume ◽  
Three Dimensional ◽  
Entrance Region ◽  
Temperature Fields ◽  
Uniform Structure ◽  
Buoyancy Effect ◽  
Laminar Mixed Convection ◽  
Helical Pipe

Abstract A fully elliptic numerical study is performed to investigate the buoyancy-affected, three-dimensional laminar flow and heat transfer in the entrance region of a helical pipe at a constant wall temperature. The Control Volume Method with second-order accuracy is used to numerically solve the three-dimensional fully elliptic governing equations for the problem. The O-type non-uniform structure grid system is adopted to discretize the computation domain (two complete turns of a helical pipe) in this study. The Bossinesq approximation is applied to deal with the buoyancy effect caused directly by density difference. The developments of flow and temperature fields, profiles and characteristics at different Gr/Re2 are given and discussed. The computed results reveal that the entrance region of heat transfer is increased rapidly when buoyancy force is considered. In the meantime, the buoyancy effect on the average Nusselt number and friction factor is greater at the entrance region of the helical pipe, but it gradually becomes weaker further downstream.

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