scholarly journals Laminar forced convection in a cylindrical collinear ohmic sterilizer

2017 ◽  
Vol 21 (5) ◽  
pp. 2217-2226
Author(s):  
Tommaso Pesso ◽  
Stefano Piva
Keyword(s):  
Thermal Analysis ◽  
Iterative Procedure ◽  
Thermal Field ◽  
Practical Interest ◽  
Liquid Food ◽  
Simultaneous Solution ◽  
Thermal Fields ◽  
Fluid Analysis ◽  
Ohmic Heater ◽  
Laminar Forced Convection

The present work deals with a thermo-fluid analysis of a collinear cylindrical ohmic heater in laminar flow. The geometry of interest is a circular electrically insulated glass pipe with two electrodes at the pipe ends. For this application, since the electrical conductivity of a liquid food depends strongly on the temperature, the thermal analysis of an ohmic heater requires the simultaneous solution of the electric and thermal fields. In the present work the analysis involves decoupling the previous fields by means of an iterative procedure. The thermal field has been calculated using an analytical solution, which leads to fast calculations for the temperature distribution in the heater. Some considerations of practical interest for the design are also given.

Long-term thermal two- and three-dimensional analysis of roller compacted concrete dams supported by monitoring verification

2010 ◽  
Vol 37 (4) ◽  
pp. 600-610 ◽  
Author(s):  
Vladan Kuzmanovic ◽  
Ljubodrag Savic ◽  
John Stefanakos
Keyword(s):  
Thermal Analysis ◽  
Boundary Conditions ◽  
Thermal Field ◽  
Numerical Models ◽  
Three Dimensional ◽  
Roller Compacted Concrete ◽  
Rcc Dam ◽  
Field Investigations ◽  
Good Agreement

This paper presents two-dimensional (2D) and three-dimensional (3D) numerical models for unsteady phased thermal analysis of RCC dams. The time evolution of a thermal field has been modeled using the actual dam shape, RCC technology and the adequate description of material properties. Model calibration and verification has been done based on the field investigations of the Platanovryssi dam, the highest RCC dam in Europe. The results of a long-term thermal analysis, with actual initial and boundary conditions, have shown a good agreement with the observed temperatures. The influence of relevant parameters on the thermal field of RCC dams has been analyzed. It is concluded that the 2D model is appropriate for the thermal phased analysis, and that the boundary conditions and the mixture properties are the most influential on the RCC dam thermal behavior.

Prediction of Comprehensive Thermal Error of a Preloaded Ball Screw on a Gantry Milling Machine

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Kuo Liu ◽  
Haibo Liu ◽  
Te Li ◽  
Yongqing Wang ◽  
Mingjia Sun ◽  
...  
Keyword(s):  
Thermal Field ◽  
Thermal Characteristics ◽  
Thermal Error ◽  
Least Square Method ◽  
High Accuracy ◽  
Least Square ◽  
Ball Screw ◽  
Milling Machine ◽  
Thermal Fields ◽  
Proposed Model

The conception of the comprehensive thermal error of servo axes is given. Thermal characteristics of a preloaded ball screw on a gantry milling machine is investigated, and the error and temperature data are obtained. The comprehensive thermal error is divided into two parts: thermal expansion error ((TEE) in the stroke range) and thermal drift error ((TDE) of origin). The thermal mechanism and thermal error variation of preloaded ball screw are expounded. Based on the generation, conduction, and convection theory of heat, the thermal field models of screw caused by friction of screw-nut pairs and bearing blocks are derived. The prediction for TEE is presented based on thermal fields of multiheat sources. Besides, the factors influencing TDE are analyzed, and the model of TDE is established based on the least square method. The predicted thermal field of the screw is analyzed. The simulation and experimental results indicate that high accuracy stability can be obtained using the proposed model. Moreover, high accuracy stability can still be achieved even if the moving state of servo axis changes randomly, the screw is preloaded, and the thermal deformation process is complex. Strong robustness of the model is verified.

Thermal Analysis on the Shell Stiffeners of Double Steel Wall LNG Storage Tank

2011 ◽  
Vol 105-107 ◽  
pp. 403-407
Author(s):  
Xiao Chun Zhang ◽  
Yuan Qi Cai
Keyword(s):  
Thermal Analysis ◽  
Structural Design ◽  
Storage Tank ◽  
Thermal Field ◽  
Local Buckling ◽  
Thermal Design ◽  
Normal Operation ◽  
Analysis Of Results ◽  
Design Requirements ◽  
Lng Tank

Shell stiffeners are used effectively to prevent preferential local buckling of LNG tank shell. In this paper, Finite element method (FEM) is applied to pay attention to the thermal analysis on the shell stiffeners of double steel wall LNG storage tank. The structural requirements according to British Standard 7777-2:1993 has been considered and then some dimensional adjustments of shell stiffeners are made to evaluate their influence on the thermal field of double steel wall LNG storage tank. Temperature distributions and heat flux of different dimensional shell stiffeners are presented. Though the analysis of results, it puts forward the conclusion that the dimensional design of shell stiffeners used in double steel wall LNG storage tank shall take not only the structural design requirements but also the thermal design ones into consideration in order to finally save cost in both construction and normal operation.

Laminar Forced Convection From a Circular Cylinder Placed in a Micropolar Fluid

2006 ◽  
Vol 129 (3) ◽  
pp. 256-264 ◽  
Author(s):  
F. M. Mahfouz
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Prandtl Number ◽  
Drag Coefficient ◽  
Forced Convection ◽  
Vortex Shedding ◽  
Micropolar Fluid ◽  
Clear Trend ◽  
Thermal Fields ◽  
Laminar Forced Convection

In this paper laminar forced convection associated with the cross-flow of micropolar fluid over a horizontal heated circular cylinder is investigated. The conservation equations of mass, linear momentum, angular momentum and energy are solved to give the details of flow and thermal fields. The flow and thermal fields are mainly influenced by Reynolds number, Prandtl number and material parameters of micropolar fluid. The Reynolds number is considered up to 200 while the Prandtl number is fixed at 0.7. The dimensionless vortex viscosity is the only material parameter considered in this study and is selected in the range from 0 to 5. The study has shown that generally the mean heat transfer decreases as the vortex viscosity increases. The results have also shown that both the natural frequency of vortex shedding and the amplitude of oscillating lift force experience clear reduction as the vortex viscosity increases. Moreover, the study showed that there is a threshold value for vortex viscosity above which the flow over the cylinder never responds to perturbation and stays symmetric without vortex shedding. Regarding drag coefficient, the results have revealed that within the selected range of controlling parameters the drag coefficient does not show a clear trend as the vortex viscosity increases.

Thermal Analysis of Solids at High Peclet Numbers Subjected to Moving Heat Sources

1999 ◽  
Vol 121 (1) ◽  
pp. 182-186 ◽  
Author(s):  
O. Manca ◽  
B. Morrone ◽  
S. Nardini
Keyword(s):  
Thermal Field ◽  
Three Dimensional ◽  
Heat Losses ◽  
Transfer Model ◽  
Heat Sources ◽  
Moving Heat Source ◽  
Motion Direction ◽  
Thermal Fields ◽  
Diffusion Component ◽  
Conductive Thermal Field

A three-dimensional heat transfer model has been developed to obtain the conductive thermal field inside a brick-type solid under a moving heat source with different beam profiles. The problem in quasi-steady state has been approximated by neglecting the axial diffusion component; thus, for Peclet numbers greater than 5, the elliptic differential equation becomes a parabolic one along the motion direction. The dependence of the solution on the radiative and convective heat losses has been highlighted. Thermal fields are strongly dependent on different spot shapes and on the impinging jet; this situation allows control of the parameters involved in the technological process.

Nanoscale Continuous Directional Motion Driven by a Cyclic Thermal Field

2021 ◽  
pp. 1-19
Author(s):  
Yichang Chen ◽  
Jiantao Leng ◽  
Zhengrong Guo ◽  
Yingyan Zhang ◽  
Tienchong Chang
Keyword(s):  
Carbon Nanotube ◽  
Thermal Gradient ◽  
Thermal Field ◽  
Joint Actions ◽  
Thermal Fields ◽  
Heating Region ◽  
Directional Motion ◽  
Gradient Forces ◽  
Controllable Motion ◽  
Novel Devices

Abstract Directional motion plays a crucial role in various mechanical systems. Although mechanisms for nanoscale directional motion have been widely used in many aspects of nanotechnology, it remains a great challenge to generate continuous and controllable motion at the nanoscale. Herein we propose a nanoscale continuous directional motion in cyclic thermal fields by using a double-walled system which consists of an outer BN/C heterojunction nanotube and a concentric inner carbon nanotube (CNT). By manipulating the heating region of the outer BN/C heterojunction tube, the continuous motion of the inner CNT can be realized with ease. The inner CNT demonstrates three distinct movements due to the joint actions of the asymmetric thermal gradient forces and interlayer attraction forces caused by the presence of the outer BN/C heterojunction nanotube. The mechanism revealed in the present study may be useful in designing novel devices for energy conversion and directional transportation.

scholarly journals The Effects of Water Friction Loss Calculation on the Thermal Field of the Canned Motor

Processes ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 256 ◽  
Author(s):  
Yiping Lu ◽  
Azeem Mustafa ◽  
Mirza Abdullah Rehan ◽  
Samia Razzaq ◽  
Shoukat Ali ◽  
...  
Keyword(s):  
Thermal Field ◽  
Test Method ◽  
Friction Loss ◽  
Heat Sources ◽  
Thermal Fields ◽  
Flow And Heat Transfer ◽  
Transfer Equations ◽  
Volume Method ◽  
Canned Motor ◽  
Separation Test

The thermal behavior of a canned motor also depends on the losses and the cooling capability, and these losses cause an increase in the temperature of the stator winding. This paper focuses on the modeling and simulation of the thermal fields of the large canned induction motor by different calculation methods of water friction loss. The values of water friction losses are set as heat sources in the corresponding clearance of water at different positions along the duct and are calculated by the analytical method, loss separation test method, and by assuming the values that may be larger than the experimental results and at zero. Based on Finite volume method (FVM), 3D turbulent flow and heat transfer equations of the canned motor are solve numerically to obtain the temperature distributions of different parts of the motor. The analysis results of water friction loss are compared with the measurements, obtained from the total losses using the loss separation method. The results show that the magnitude of water friction loss within various parts of the motor does not affect the position of peak temperature and the tendency of the temperature distribution of windings. This paper is highly significant for the design of cooling structures of electrical machines.

The Effect of Thermal Field on the Deposition of Fe-TiC on Carbon Steel Using Laser Cladding

2010 ◽  
Author(s):  
Masoud Alimardani ◽  
Ali Emamian ◽  
Amir Khajepour ◽  
Stephen F. Corbin
Keyword(s):  
Carbon Steel ◽  
Numerical Model ◽  
Laser Cladding ◽  
Thermal Field ◽  
Deposition Process ◽  
Time Dependent ◽  
Experimental Investigations ◽  
Thermal Fields ◽  
Temperature Distributions ◽  
Laser Cladding Process

In this paper, a numerical and experimental method is used to investigate the effect of thermal fields on the deposition of Fe-TiC using the laser cladding process. Since in laser cladding temperature distributions and consequent rapid cooling rates determine the microstructure and final physical properties of the deposited layers, a 3D time-dependent numerical model is used to simulate the cladding process parallel to experimental analysis. The numerical results are used to study the temperature distributions and their evolutions throughout the deposition process. The experimental and verified numerical outcomes are then employed to study the variations of the microstructures of the deposited material as well as correlation between the formed microstructures and temperature distributions across the deposition domain. The numerical and experimental investigations are conducted through the deposition of Fe-TiC on the substrate of AISI 1030 carbon steel using a 1.1 kW fiber laser. The experimental results confirm that by increasing the substrate temperature throughout the process the distribution of the TiC particles changes along with the deposited tracks and the TiC particles start forming clusters at the top of the clad.

The interference of thermal fields from line sources in grid turbulence

1984 ◽  
Vol 144 ◽  
pp. 363-387 ◽  
Author(s):  
Z. Warhaft
Keyword(s):  
Line Source ◽  
Cross Correlation ◽  
Thermal Field ◽  
Grid Turbulence ◽  
Inference Method ◽  
Thermal Fields ◽  
Downstream Distance ◽  
Scalar Variance ◽  
Rate Of Decay ◽  
Total Temperature

The interference of passive thermal fields produced by two (and more) line sources in decaying grid turbulence is studied by using the inference method described by Warhaft (1981) to determine the cross-correlation coefficient ρ between the temperature fluctuations produced by the sources. The evolution of ρ as a function of downstream distance, for 0.075 < d/l < 10, where d is the wire spacing and l is the integral lengthscale of the turbulence, is determined for a pair of sources located at various distances from the grid. It is found that ρ may be positive or negative (thereby enhancing or diminishing the total temperature variance) depending on the line-source spacing, their location from the grid and the position of measurement. It is also shown that the effects of a mandoline (Warhaft & Lumley 1978) may be idealized as the interference of thermal fields produced by a number of line sources. Thus new light is shed on the rate of decay of scalar-variance dissipation. The thermal field of a single line source is also examined in detail, and these results are compared with other recent measurements.

scholarly journals Thermal Field Analysis and Simulation of an Infrared Belt Furnace Used for Solar Cells

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Bai Lu ◽  
Liang Zongcun ◽  
Shen Hui
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Gas Flow ◽  
Thermal Field ◽  
Field Analysis ◽  
Metal Particles ◽  
Thermal Fields ◽  
Internal Structures ◽  
Cell Firing ◽  
Transient Thermal

During solar cell firing, volatile organic compounds (VOC) and a small number of metal particles were removed using the gas flow. When the gas flow was disturbed by the thermal field of infrared belt furnace and structure, the metal particles in the discharging gas flow randomly adhered to the surface of solar cell, possibly causing contamination. Meanwhile, the gas flow also affected the thermal uniformity of the solar cell. In this paper, the heating mechanism of the solar cell caused by radiation, convection, and conduction during firing was analyzed. Afterward, four 2-dimensional (2D) models of the furnace were proposed. The transient thermal fields with different gas inlets, outlets, and internal structures were simulated. The thermal fields and the temperature of the solar cell could remain stable and uniform when the gas outlets were installed at the ends and in the middle of the furnace, with the gas inlets being distributed evenly. To verify the results, we produced four types of furnaces according to the four simulated results. The experimental results indicated that the thermal distribution of the furnace and the characteristics of the solar cells were consistent with the simulation. These experiments improved the efficiency of the solar cells while optimizing the solar cell manufacturing equipment.

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