scholarly journals 3D Microscale Heat Transfer Model of the Thermal Properties of Wood-Metal Functional Composites Based on the Microstructure

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2709
Author(s):  
Yuan Chai ◽  
Shanqing Liang ◽  
Yongdong Zhou ◽  
Lanying Lin ◽  
Feng Fu
Keyword(s):  
Heat Transfer ◽  
Composite Material ◽  
Thermal Properties ◽  
Heat Transfer Process ◽  
Transfer Model ◽  
Metal Composite ◽  
Model Framework ◽  
Element Analysis ◽  
Microscale Heat Transfer ◽  
Functional Composites

This study presents a model for simulating the microscopic heat transfer processes in a wood-metal composite material. The model was developed by analyzing the microstructure of experimental samples comprising a melted alloy impregnated in a wood matrix. According to the thermal parameters of the materials and the boundary conditions, an analytical model of microscale heat transfer was established using Abaqus finite element analysis software. The model was validated experimentally by comparing temperature curves obtained via simulation and experiments; the resulting correlation coefficient was 0.96557. We then analyzed the temperature distribution of the composite material with different cell geometries and heat transfer conditions (heat transfer direction and applied temperature). The thermal properties of the unit cell models were in good agreement with the general trends predicted by several heat transfer equations. This study provides a method for analyzing the microscale heat transfer process in wood-based composites. In addition, the model framework characteristics can be used to evaluate the heat transfer mechanism of impregnated modified wood.

Numerical Investigation on the Heat Transfer Enhancement Behavior Outside Longitudinal Finned Tubes

2018 ◽  
Author(s):  
Yujia Zhou ◽  
Hanliang Bo ◽  
Jingyu Du
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Transfer Process ◽  
Numerical Results ◽  
Transfer Model ◽  
Hydraulic Characteristics ◽  
Finned Tubes ◽  
Smooth Tubes

With the purpose of enhancement of heat transfer performance and reduction of the volume of steam generator (SG), a structure of longitudinal finned tubes was proposed to replace the smooth tubes of SG in this paper. Taking the SG smooth tubes of Daya bay Nuclear Power plant as a reference, the simplified heat transfer model of new longitudinal finned tubes was established by ANSYS CFX. Three-dimensional numerical model was developed to investigate the fluid-solid coupled thermal hydraulic characteristics of different types of the longitudinal finned tubes compared with the smooth tubes. Analysis of calculation results were sufficiently discussed for the effect of mass flow rate, fin array, solid thermal conductivity and frictional resistance. The numerical results revealed that the heat transfer coefficient increase with the increasing mass flow rate in the secondary side. The material of the tubes has significantly influence on the heat transfer process. Different flow conditions have different thermal hydraulic characteristics. The evaluated criterion to judge the enhancement of the heat transfer of the coupled process was also proposed. The numerical results can provide some useful guidance for design optimization of longitudinal finned tubes in SG.

Effective heat conductivity of Honeycomb (porous) composite panel

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Cletus Matthew Magoda ◽  
Jasson Gryzagoridis ◽  
Kant Kanyarusoke
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Composite Material ◽  
Thermal Properties ◽  
Heat Conductivity ◽  
Composite Panel ◽  
Porous Composite ◽  
Content Type ◽  
One Dimensional ◽  
Coefficient Of Thermal Conductivity

Purpose The purpose of this paper is to validate an assumption of what to use as an effective (steady state) heat transfer coefficient of thermal conductivity for the honeycomb core sandwiched by Fiberglass face sheets composite. A one-dimensional model based on Fourier law is developed. The results are validated experimentally. Design/methodology/approach The results were obtained from the one-dimensional mathematical model of an overall or effective heat conductivity of the Honeycomb composite panel. These results were validated experimentally by applying heat flux on the specimen under controlled environment. The surface temperatures at different voltages were recorded and analysed. The skin of the sandwich composite material used in the investigation was Fiberglass sheet with a thickness of 0.5 mm at the bottom and 1.0 mm at the top surface. Both skins have a stacking sequence of zero degrees. Due to the presence of air cells in the core (Honeycomb), the model considers the conduction, convection and radiation heat transfer, across the thickness of the panel, combined as an effective conduction mode, whose value may be predicted by using the coefficient of thermal conductivity of the air based on the average temperature difference between the two skins. The experimental results for the heat transfer through the thickness of the panel provide validation of this assumption/prediction. Both infrared thermography and conventional temperature measurement techniques (thermocouples) were used to collect the data. Findings The heat transfer experiment and mathematical modeling were conducted. The data obtained were analyzed, and it was found that the effective thermal conductivity was temperature-dependent as expected. The effective thermal conductivity of the honeycomb panel was close to that of air, and its value could be predicted if the panel surface temperatures were known. It was also found that as temperature raised the variation between experimental and predicted effective air conduction raised up. This is because there was an increase in molecular diffusion and vibration. Therefore, the convection heat transfer increased at high temperatures and the air became an insulator. Originality/value Honeycomb composite panels have excellent physical and thermal properties that influence their performance. This study provides an appropriate method in determining thermal conductivity, which is one of the critical thermal properties of porous composite material. This paper also gives useful and practical data to industries that use or manufacture honeycomb composite panels.

Heat Transfer on a Turbocharger Under Constant Load Points

2009 ◽  
Author(s):  
A. Romagnoli ◽  
Ricardo Martinez-Botas
Keyword(s):  
Heat Transfer ◽  
Combustion Engine ◽  
Constant Load ◽  
Heat Transfer Process ◽  
Transfer Model ◽  
Performance Deterioration ◽  
Exit Temperature ◽  
Standard Set ◽  
Compressor Performance ◽  
Compressor Efficiency

The processes occurring in turbo machinery applications are frequently treated as adiabatic. However, in a turbocharger significant heat transfer occurs, leading to a deficit of turbocharger performance. The overall objective of this experimental work is to improve the understanding of the heat transfer process taking place in a turbocharger when installed on an internal combustion engine. In order to do this, beyond the standard set of measurements needed to define the turbo operating point, a large number of thermocouples were installed on the turbocharger. The tests results allow the quantification of the temperatures within the turbocharger and revealed that a nonuniform temperature distribution exists on the compressor and turbine casings. This is partly attributed to the proximity of the turbocharger to the engine. This process plays a role on the deterioration of the compressor efficiency when compared to the corresponding adiabatic efficiency. A correlation that allows the calculation of the compressor exit temperature is proposed. The method uses the surface temperature of the bearing housing; it was validated against experimental data with deviations no larger than 3%. A simplified 1-dimensional heat transfer model was also developed and compared with experimental measurements. The algorithms calculate the heat transferred through the turbocharger, from the hot end to the cold end by means of lump masses. The compressor performance deterioration from the adiabatic map is predicted.

Simulation Study on Heat Insulating Material Used in Refrigerated Cargo Hold Shipboard of Fishing Vessel

2011 ◽  
Vol 311-313 ◽  
pp. 1953-1956
Author(s):  
Jing Fu Jia ◽  
Wei He
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Heat Transfer Process ◽  
Transfer Model ◽  
Fishing Vessel ◽  
Transfer Property ◽  
Insulating Material ◽  
Temperature Distributions ◽  
Heat Transfer Property ◽  
Computational Fluid Dynamics Cfd

To choose the suitable heat insulating material for refrigerated cargo hold shipboard of fishing vessel, a steady state three-dimensional mathematical model of heat transfer is developed in this paper. The heat-transfer model is simplified reasonably in order to facilitate analyzing and solving. After defining the boundary conditions of the model according to the heat-transfer process of the shipboard, numerical simulations with different heat insulating material are performed using computational fluid dynamics (CFD) software PHOENICS. The obtained temperature distributions of the model in each case are analyzed. The suitable one is pointed out according to the degree of influence of the heat insulating material on heat-transfer property of the shipboard.

scholarly journals Experimental Investigation on Condensation of Vapor in the Presence of Non-Condensable Gas on a Vertical Tube

2018 ◽  
Author(s):  
Shengjun Zhang ◽  
Feng Shen ◽  
Xu Cheng ◽  
Xianke Meng ◽  
Dandan He
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Total Pressure ◽  
Mass Fraction ◽  
Heat Removal ◽  
Heat Transfer Process ◽  
Transfer Model ◽  
Operation Conditions ◽  
The Heat Transfer Coefficient

According to the operation conditions of time unlimited passive containment heat removal system (TUPAC), a separate effect experiment facility was established to investigate the heat transfer performance of steam condensation in presence of non-condensable gas. The effect of wall subcooling temperature, total pressure and mass fraction of the air on heat transfer process was analyzed. The heat transfer model was also developed. The results showed that the heat transfer coefficient decreased with the rising of subcooling temperature, the decreasing of the total pressure and air mass fraction. It was revealed that Dehbi’s correlation predicted the heat transfer coefficient conservatively, especially in the low pressure and low temperature region. The novel correlation was fitted by the data obtained in the following range: 0.20~0.45 MPa in pressure, 20% ~ 80% in mass fraction, 15°C ~ 45°C in temperature. The discrepancy of the correlation and experiment data was with ±20%.

Microscopic Observation of Energy Propagation in Polymeric Fluids Crossing a Barrier

2008 ◽  
Author(s):  
Rashad Aouf ◽  
Vojislav Ilic
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Large Scale ◽  
Complex Geometry ◽  
Molecular Model ◽  
Heat Transfer Process ◽  
Transfer Model ◽  
Energy Propagation ◽  
Lennard Jones ◽  
Macro Scale

A major challenge facing tumour treatment procedures, including hyperthermia, is the inadequate modelling of the bio-heat transfer process. Therefore, an accurate mathematical bio-heat transfer model has to precisely quantify the temperature distribution within a complex geometry of a tumour tissue, in order to help optimize unwanted side effects for patients and minimize (avoid) collateral tissue damage. This study examines the three-dimensional molecular dynamics (MDs) simulation of a Lennard-Jones fluid in the hope of contributing to the understanding of the propagation of a thermal wave in fluids causing phase change i.e. irreversible gelation. It is intended to establish, from such information, a useful benchmark for application to large scale phenomena involving macro scale heat transfer. Specifically, this study examines assemblies of N particles (N = 500 atoms) and analyses the microscopic simulation of double well interaction with permanent molecular bond formation at various temperatures within the range 1–2.5Kb/εT. The dynamics of the fluid is also being studied under the influence of a temperature gradient, dt/dx, where neighbouring particles (i.e. atoms/molecules) are randomly linked by permanent bonds to form clusters of different sizes. The atomic/molecular model consist of an isothermal source and sink whose particles are linked by springs to lattice sites to avoid melting, and a bulk of 500 atoms/molecules in the middle representing the Lennard-Jones fluid. Then, this study simulates the energy propagation following the temperature gradient between the heat source and heat sink at T1 = 2.5 and T2 = 1.5 respectively. The potential equation involved in this study is given by the Finitely Extensible Non Elastic (FENE) and Lennard-Jones (LJ) interaction potential. It is observed that the atoms of the bulk start to form a large cluster (∼ 300 atoms) with long time of simulation estimated by 106 time steps where τ = SQRT(ε/mσ2) and Δt = 10−3. It is also obtained that the potential energy of 13.65KbT across a barrier to establish permanent bonds giving rise to irreversible gel formation. All the parameters used in this study are expressed in Lennard-Jones units.

scholarly journals Study on the Thermal Properties of Hollow Shale Blocks as Self-Insulating Wall Materials

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Guo-liang Bai ◽  
Ning-jun Du ◽  
Ya-zhou Xu ◽  
Chao-gang Qin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Properties ◽  
Transfer Coefficient ◽  
Wall Material ◽  
Element Analysis ◽  
Experimental Heat ◽  
Wall Materials ◽  
Save Energy ◽  
The Heat Transfer Coefficient

To reduce energy consumption and protect the environment, a type of hollow shale block with 29 rows of holes was designed and produced. This paper investigated the thermal properties of hollow shale blocks and walls. First, the guarding heat-box method was used to obtain the heat transfer coefficient of the hollow shale block walls. The experimental heat transfer coefficient is 0.726 W/m2·K, which would save energy compared to traditional wall materials. Then, the theoretical value of the heat transfer coefficient was calculated to be 0.546 W/m2·K. Furthermore, the one-dimensional steady heat conduction process for the block and walls was simulated using the finite element analysis software ANSYS. The predicted heat transfer coefficient for the walls was 0.671 W/m2·K, which was in good agreement with the test results. With the outstanding self-insulation properties, this type of hollow shale block could be used as a wall material without any additional insulation measures in masonry structures.

scholarly journals Numerical investigation of the transient spray cooling process for quenching applications

2018 ◽  
Vol 22 (5) ◽  
pp. 1943-1953 ◽  
Author(s):  
Jakov Baleta ◽  
Fengsheng Qi ◽  
Marija Zivic ◽  
Martina Lovrenic-Jugovic
Keyword(s):  
Heat Transfer ◽  
Relevant Literature ◽  
Spray Cooling ◽  
Heat Transfer Process ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Wall Heat Transfer ◽  
Water Spray ◽  
Quenching Process ◽  
Particle Velocities

Water spray quenching distinguished itself as a promising method for industry production, especially for the parts which require good mechanical strength while simultaneously retaining the initial toughness. Studies have shown that the heat transfer process during the spray quenching is mostly influenced by the spray impingement density, particle velocities and sizes. The application of advanced numerical methods still plays insufficient role in the development of the production process, in spite of the fact that industry today is facing major challenges that can be met only by development of new and more efficient systems using advanced tools for product development, one of which is CFD. Taking the above stated, the object of this research is numerical simulation of spray quenching process in order to determine validity of mathematical models implemented within the commercial CFD code Fire, especially droplet evaporation/condensation and droplet-wall heat transfer model. After review of the relevant literature suitable benchmark case was selected and simulated by employing discrete droplet method for the spray treatment and Eulerian approach for the gas phase description. Simulation results indicated that existing droplet/wall heat transfer model is not able to reproduce heat transfer of dense water spray. Thus, Lagrangian spray model was improved by implementing experimental correlation for heat transfer coefficient during spray quenching. Finally, verification of the implemented model was assessed based on the conducted simulations and recommendations for further improvements were given.

Relationship Between the Nonlocal Effect and Lagging Behavior in Bioheat Transfer

2021 ◽  
Author(s):  
Xiaoya Li ◽  
Yan Li ◽  
Pengfei Luo ◽  
Xiao Geng Tian
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Order Effect ◽  
Heat Transfer Process ◽  
Bioheat Transfer ◽  
Transfer Model ◽  
Phase Lag ◽  
Medical Systems ◽  
Conduction Model ◽  
Transfer Equations

Abstract Lots of generalized heat conduction models have been developed in recent decades, such as local thermal non-equilibrium model, phase lagging model and nonlocal heat conduction model. But no attempt was made to prove which model is better (or worse) than others, or whether there is a certain relationship between these different models. With this inspiration, we establish the nonlocal bioheat transfer equations with lagging time, and the two and three-temperature bioheat transfer equations with considering all the carries' heat conduction effect are also constructed. Comparing the two (or three)-temperature equation model with the nonlocal bioheat transfer models with lagging time, one may obtain: the lagging time tt of temperature gradient and the nonlocal characteristic length ?q in the space derivative items of heat flux have the same effect on heat transfer; when the heat transport occur among N energy carriers with considering the conduction effects of all carries, the heat transfer process are depend on the high-order effect of tqN-1, ttN-1 and ?t(2N-1) in nonlocal dual phase lag bioheat transfer model. This phenomenon is very important for biological and medical systems where numerous carriers may exist on the cellular level.

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