Comparison of Vacuum Glazing Thermal Performance Predicted Using Two and Three Dimensional Models and Their Experimental Validation

The thermal performance of vacuum glazing was predicted using two dimensional (2-D) finite element and three dimensional (3-D) finite volume models. In the 2-D model, the vacuum space, including the pillar arrays, was represented by a material whose effective thermal conductivity was determined from the specified vacuum space width, the heat conduction through the pillar array and the calculated radiation heat transfer between the two interior glass surfaces within the vacuum gap. In the 3-D model, the support pillar array was incorporated and modeled within the glazing unit directly. The difference in predicted overall heat transfer coefficients between the two models for the vacuum window simulated was less than 3%. A guarded hot box calorimeter was used to determine the experimental thermal performance of vacuum glazing. The experimentally determined overall heat transfer coefficient and temperature profiles along the central line of the vacuum glazing are in very good agreement with the predictions made using the 2-D and 3-D models.

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Evaluation of Thermal Performance for Vacuum Glazing by Using Three-Dimensional Finite Element Model

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.492.328 ◽

2011 ◽

Vol 492 ◽

pp. 328-332 ◽

Cited By ~ 6

Author(s):

Zhi Ming Han ◽

Yi Wang Bao ◽

Wei Dong Wu ◽

Zheng Quan Liu ◽

Xiao Gen Liu ◽

...

Keyword(s):

Heat Transfer ◽

Thermal Performance ◽

Simulation Analysis ◽

Three Dimensional ◽

Central Area ◽

Element Model ◽

Transfer Coefficients ◽

Heat Transfer Coefficients ◽

Vacuum Glazing ◽

Three Dimensional Finite Element

Simulation analysis of thermal performance for vacuum glazing was conducted in this paper. The heat conduction through the support pillars and edge seal and the radiation between two glass sheets were considered. The heat conductance of residual gas in vacuum gap was ignored for a low pressure of less than 0.1Pa. Two pieces of vacuum glazing with sizes of 0.3 × 0.3 m and 1.0 × 1.0 m were simulated. In order to check the accuracy of simulations with specified mesh number, the thermal performance of a small central area (4mm×4mm) with a single pillar in the center was simulated using a graded mesh of 41×41×5 nodes. The heat transfer coefficients of this unit obtained from simulation and analytic prediction were 2.194Wm-2K-1and 2.257Wm-2K-1respectively, with a deviation of 2.79%. The three dimensional (3D) isotherms and two dimensional (2D) isotherms on the cold and hot surfaces of the specimens were also presented. For a validity of simulated results, a guarded hot box calorimeter was used to determine the experimental thermal performance of 1.0m×1.0m vacuum glazing. The overall heat transfer coefficients obtained from experiment and simulation were 2.55Wm-2K-1 and 2.47Wm-2K-1respectively, with a deviation of 3.14%.

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Effect of Surface Roughness on Fluid Flow and Heat Transfer Characteristics of Lattice Brick Setting in Tunnel Kilns

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4050327 ◽

2021 ◽

Vol 13 (6) ◽

Author(s):

Issa F. Almesri ◽

Mosab A. Alrahmani ◽

Jaber H. Almutairi ◽

Hosny Z. Abou-Ziyan

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Fluid Flow ◽

Pressure Drop ◽

Radiation Heat Transfer ◽

Three Dimensional ◽

Wall Roughness ◽

Radiation Heat ◽

Transfer Coefficients ◽

Pressure Drops

Abstract This paper presents the effect of brick and kiln wall roughness on the fluid flow, pressure drop, and convection and radiation heat transfer in tunnel kilns. The surface roughness of 0–4 mm is investigated for bricks and tunnel boundary. Another wall roughness of 10 mm is considered to explore the effect of significant defects in the tunnel boundary. The study is conducted using a three-dimensional computational fluid dynamics (CFD) model based on the finite volume method with the k – ω turbulence model. The convective heat transfer coefficients enhance by 45% and 97%, and the pressure drop increases by 25.1% and 80.4% as the brick roughness is increased from 0 to 1 mm and 0 to 4 mm, respectively. The ratio of heat transfer rate to pumping power reaches its maximum at a brick roughness of 2 mm. These results provide essential knowledge about the acceptable range of brick roughness for manufacturers. As the tunnel boundary roughness is increased from 0 to 1 and 0 to 10 mm, the heat transfer rates increase by 1.34% and 3.88%, while the pressure drops increase by 7.5% and 18.2%, respectively. These results are supportive of scheduling the maintenance of tunnel kilns’ interior structure. Moreover, the enhancement of the radiation heat transfer depends on the brick emissivity and the area ratio of rough to smooth surfaces.

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Thermal performance of buildings. Transmission and ventilation heat transfer coefficients. Calculation method

10.3403/30115305 ◽

2008 ◽

Keyword(s):

Heat Transfer ◽

Thermal Performance ◽

Calculation Method ◽

Transfer Coefficients ◽

Heat Transfer Coefficients

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Numerical simulation of variable thermal conductivity on 3D flow of nanofluid over a stretching sheet

Nonlinear Engineering ◽

10.1515/nleng-2020-0011 ◽

2020 ◽

Vol 9 (1) ◽

pp. 233-243 ◽

Cited By ~ 3

Author(s):

Nainaru Tarakaramu ◽

P.V. Satya Narayana ◽

Bhumarapu Venkateswarlu

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Stretching Sheet ◽

Three Dimensional ◽

Variable Thermal Conductivity ◽

Normal Velocity ◽

Transfer Coefficients ◽

Similarity Transformations ◽

Frictional Coefficients ◽

The Impact

AbstractThe present investigation deals with the steady three-dimensional flow and heat transfer of nanofluids due to stretching sheet in the presence of magnetic field and heat source. Three types of water based nanoparticles namely, copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are considered in this study. The temperature dependent variable thermal conductivity and thermal radiation has been introduced in the energy equation. Using suitable similarity transformations the dimensional non-linear expressions are converted into dimensionless system and are then solved numerically by Runge-Kutta-Fehlberg scheme along with well-known shooting technique. The impact of various flow parameters on axial and transverse velocities, temperature, surface frictional coefficients and rate of heat transfer coefficients are visualized both in qualitative and quantitative manners in the vicinity of stretching sheet. The results reviled that the temperature and velocity of the fluid rise with increasing values of variable thermal conductivity parameter. Also, the temperature and normal velocity of the fluid in case of Cu-water nanoparticles is more than that of Al2O3- water nanofluid. On the other hand, the axial velocity of the fluid in case of Al2O3- water nanofluid is more than that of TiO2nanoparticles. In addition, the current outcomes are matched with the previously published consequences and initiate to be a good contract as a limiting sense.

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Effect of Insulated/Uninsulated Channel Walls on Heat Transfer From a Horizontal Finned Tube in a Vertical Channel

Journal of Heat Transfer ◽

10.1115/1.3248092 ◽

1987 ◽

Vol 109 (2) ◽

pp. 388-391 ◽

Cited By ~ 1

Author(s):

E. M. Sparrow ◽

M. A. Ansari

Keyword(s):

Heat Transfer ◽

Radiation Heat Transfer ◽

Vertical Channel ◽

Finned Tube ◽

Radiation Heat ◽

Transfer Coefficients ◽

Heat Transfer Coefficients ◽

Metallic Sheet ◽

Rayleigh Numbers ◽

Metal Wall

Measurements were made of the combined natural convection and radiation heat transfer from a horizontal finned tube situated in a vertical channel open at the top and bottom. In one set of experiments, both walls of the channel were heavily insulated, while in a second set of experiments, one of the insulated walls was replaced by an uninsulated metallic sheet. In general, the heat transfer coefficients were found to be lower with the metal wall in place, but only moderately. With the finned tube situated at the bottom of the channel, the differences in the heat transfer coefficients corresponding to the two types of walls were only a few percent. When the tube was positioned at the mid-height of the channel, larger differences were encountered, but in the practical range of Rayleigh numbers, the differences did not exceed 5 percent.

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Flow Past a Spinning Sphere With Surface Blowing and Heat Transfer

Journal of Fluids Engineering ◽

10.1115/1.1852471 ◽

2005 ◽

Vol 127 (1) ◽

pp. 163-171 ◽

Cited By ~ 13

Author(s):

H. Niazmand ◽

M. Renksizbulut

Keyword(s):

Heat Transfer ◽

Three Dimensional ◽

Flow Regimes ◽

Solid Sphere ◽

Temporal Variations ◽

Transfer Coefficients ◽

Transfer Rates ◽

Particle Spin ◽

Flow Past ◽

Angular Velocities

Computations are performed to determine the transient three-dimensional heat transfer rates and fluid forces acting on a stream-wise spinning sphere for Reynolds numbers in the range 10⩽Re⩽300 and angular velocities Ωx⩽2. In this Re range, classical flow past a solid sphere develops four different flow regimes, and the effects of particle spin are studied in each regime. Furthermore, the combined effects of particle spin and surface blowing are examined. Sphere spin increases drag in all flow regimes, while lift shows a nonmonotonic behavior. Heat transfer rates are not influenced by spin up to a certain Ωx but increase monotonically thereafter. An interesting feature associated with sphere spin is the development of a special wake regime such that the wake simply spins without temporal variations in its shape. For this flow condition, the magnitudes of the lift, drag, and heat transfer coefficients remain constant in time. Correlations are provided for drag and heat transfer.

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Computational Insights Into Air-Side Flow and Heat Transfer in Compact Heat Exchangers

Heat Transfer: Volume 2 ◽

10.1115/ht2005-72846 ◽

2005 ◽

Author(s):

D. K. Tafti

Keyword(s):

Heat Transfer ◽

Heat Capacity ◽

Heat Exchangers ◽

Three Dimensional ◽

Computer Experiments ◽

Transfer Coefficients ◽

Substantial Impact ◽

Compact Heat Exchangers ◽

Thermal Phenomena ◽

Side Flow

The paper describes two- and three-dimensional computer simulations which are used to study fundamental flow and thermal phenomena in multilouvered fins used for air-side heat transfer enhancement in compact heat exchangers. Results pertaining to flow transition, thermal wake interference, and fintube junction effects are presented. It is shown that a Reynolds number based on flow path rather than louver pitch is more appropriate in defining the onset of transition, and characteristic frequencies in the louver bank scale better with a global length scale such as fin pitch than with louver pitch or thickness. With the aid of computer experiments, the effect of thermal wakes is quantified on the heat capacity of the fin as well as the heat transfer coefficient, and it is established that experiments which neglect accounting for thermal wakes can introduce large errors in the measurement of heat transfer coefficients. Further, it is shown that the geometry of the louver in the vicinity of the tube surface has a large effect on tube heat transfer and can have a substantial impact on the overall heat capacity.

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Experimental Investigation of Heat Transfer in Impingement Air Cooled Plate Fin Heat Sinks

Journal of Electronic Packaging ◽

10.1115/1.2351906 ◽

2005 ◽

Vol 128 (4) ◽

pp. 412-418 ◽

Cited By ~ 21

Author(s):

Zhipeng Duan ◽

Y. S. Muzychka

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Thermal Resistance ◽

Thermal Performance ◽

Heat Transfer Model ◽

Heat Sinks ◽

Transfer Model ◽

Transfer Coefficients ◽

Developing Flow ◽

Rectangular Channels

Impingement cooling of plate fin heat sinks is examined. Experimental measurements of thermal performance were performed with four heat sinks of various impingement inlet widths, fin spacings, fin heights, and airflow velocities. The percent uncertainty in the measured thermal resistance was a maximum of 2.6% in the validation tests. Using a simple thermal resistance model based on developing laminar flow in rectangular channels, the actual mean heat transfer coefficients are obtained in order to develop a simple heat transfer model for the impingement plate fin heat sink system. The experimental results are combined into a dimensionless correlation for channel average Nusselt number Nu∼f(L*,Pr). We use a dimensionless thermal developing flow length, L*=(L∕2)∕(DhRePr), as the independent parameter. Results show that Nu∼1∕L*, similar to developing flow in parallel channels. The heat transfer model covers the practical operating range of most heat sinks, 0.01<L*<0.18. The accuracy of the heat transfer model was found to be within 11% of the experimental data taken on four heat sinks and other experimental data from the published literature at channel Reynolds numbers less than 1200. The proposed heat transfer model may be used to predict the thermal performance of impingement air cooled plate fin heat sinks for design purposes.

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Simulation of Radiation Heat Transfer of Three Dimensional Participating Media by Radiative Exchange Method

Heat Transfer: Volume 3 ◽

10.1115/ht2008-56076 ◽

2008 ◽

Author(s):

Mohammad Hadi Bordbar ◽

Timo Hyppa¨nen

Keyword(s):

Heat Transfer ◽

Balance Equation ◽

Radiation Heat Transfer ◽

Three Dimensional ◽

Radiation Balance ◽

Scattering Media ◽

Radiation Heat ◽

Exchange Method ◽

Participating Media ◽

Radiative Exchange

This paper describes the theoretical bases of the Radiative Exchange Method, a new numerical method for simulating radiation heat transfer. By considering radiative interaction between all points of the geometry and solving the radiation balance equation in a mesh structure coarser than the structure used in computational fluid flow calculation, this method is able to simulate radiative heat transfer in arbitrary 3D space with absorbing, emitting and scattering media surrounded by emitting, absorbing and reflecting surfaces. A new concept is introduced, that of the exchange factors between the different elements that are necessary for completing the radiative balance equation set. Using this method leads to a set of algebraic equations for the radiative outgoing power from each coarse cell being produced and the result of this set of equations was then used to calculate the volumetric radiative source term in the fine cell structure. The formulation of the exchange factor for a three-dimensional state and also a mesh size analysis that was conducted to optimize the accuracy and runtime are presented. The results of this model to simulate typical 3D furnace shape geometry, is verified by comparison with those of other numerical methods.

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