Transient Heat Transfer in a Conducting Particle With Internal Radiant Absorption

1992 ◽  
Vol 114 (2) ◽  
pp. 304-309 ◽  
Author(s):  
A. Tuntomo ◽  
C. L. Tien
Keyword(s):  
Heat Transfer ◽  
Liquid Droplet ◽  
Local Maximum ◽  
Transient Heat Transfer ◽  
Maximum Temperature ◽  
Transient Temperature ◽  
Radiation Parameter ◽  
Current Effort ◽  
Transient Temperature Field ◽  
Conducting Particle

The objective of the present work is to analyze rigorously the transient heat transfer of an irradiated particle by treating the radiant absorption on a local basis. A new conduction-to-radiation parameter is introduced to characterize the relative importance of heat transfer by conduction as compared with that by radiation. The study on the transient temperature field as a function of conduction-to-radiation parameter establishes a criterion identifying the circumstances where heat transfer by radiation is so predominant that conduction is negligible. The current effort is also directed at developing a convenient method for predicting the transient local maximum temperature and explosion time delay of an intensely irradiated liquid droplet.

Transient Heat Transfer of a Hollow Cylinder Subjected to Periodic Boundary Conditions

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Yujia Sun ◽  
Xiaobing Zhang
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Hollow Cylinder ◽  
Periodic Boundary ◽  
Periodic Boundary Conditions ◽  
Transient Heat Transfer ◽  
Maximum Temperature ◽  
Water Cooling ◽  
Chromium Plating ◽  
Inner Surface

The purpose of this paper is to study the transient temperature responses of a hollow cylinder subjected to periodic boundary conditions, which comprises with a short heating period (a few milliseconds) and a relative long cooling period (a few seconds). During the heating process, the inner surface is under complex convection heat transfer condition, which is not so easy to approximate. This paper first calculated the gas temperature history and the convective heat transfer coefficient history between the gas flow and the inner surface and then they were applied to the inner surface as boundary conditions. Finite element analysis was used to solve the transient heat transfer equations of the hollow cylinder. Results show that the inner surface is under strong thermal impact and large temperature gradient occurs in the region adjacent to the inner surface. Sometimes chromium plating and water cooling are used to relief the thermal shock of a tube under such thermal conditions. The effects of these methods are analyzed, and it indicates that the chromium plating can reduce the maximum temperature of the inner surface for the first cycle during periodic heating and the water cooling method can reduce the growth trend of the maximum temperature for sustained conditions. We also investigate the effects of different parameters on the maximum temperature of the inner surface, like chromium thickness, water velocity, channel diameter, and number of cooling channels.

scholarly journals Cooling Process Analysis of a 5-Drum System for Radioactive Waste Processing

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2689
Author(s):  
Alfredo Iranzo ◽  
Francisco Pino ◽  
José Guerra ◽  
Francisco Bernal ◽  
Nicasio García
Keyword(s):  
Heat Transfer ◽  
Radioactive Waste ◽  
Cooling System ◽  
Process Analysis ◽  
Internal Heat ◽  
Maximum Temperature ◽  
Transient Temperature ◽  
Cfd Modelling ◽  
Air Inlet ◽  
Slag Properties

A cooling system design for the processing of radioactive waste drums is investigated in this work, with the objective of providing insights for the determination of the air flow rate required to ensure an acceptable slag temperature (323 K or below) after 5 days. A methodology based on both 3D and 2D axisymmetric Computational Fluid Dynamics (CFD) modelling is developed. Transient temperature distributions within the drums in time and space determined by the heat transfer characteristics are studied in detail. A sensitivity analysis is also carried out assuming different physical properties of the radioactive slag. It was found out that for all variations analyzed, the maximum temperature of slag at the end of five days cooling is below 323 K, where the maximum outlet air temperature for a minimum air inlet velocity of 1 m/s is between 320 K and 323 K depending on the radioactive slag properties. When glass-like radioactive slag properties are assumed, the internal heat conduction within the slag is limiting the overall heat transfer, therefore requiring significantly longer cooling times.

Transient Heat Transfer of Piston/Rings/Liner System in Diesel Engines

2005 ◽  
Author(s):  
Daxi Xiong ◽  
Tian Tian ◽  
Victor Wong
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Transfer Process ◽  
Diesel Engines ◽  
Frictional Heating ◽  
Heat Transfer Process ◽  
Transient Heat Transfer ◽  
Transient Temperature ◽  
Piston Rings ◽  
Liner System

In diesel engines, transient heat transfer in the piston/rings/liner system greatly affects the performance of the engine, such as in carbon deposit buildup, microwelding, lubricant degradation, and changing mechanical properties of the materials. The current work aims at studying the local piston/rings/liner transient heat-transfer process by incorporating real time dynamics of the rings in sufficient detail. In the present study, several techniques have been adopted to simulate the transient heat transfer process, with fully-incorporated ring dynamics. These techniques include using the model/submodel approach, local refined mesh approach, and the virtual thermal conductivity approach. The transient temperature and heat flux profiles in the piston and rings are illustrated. The results show that the relative movement of the rings greatly affects the temperature/heat flux distribution and the peak temperature in the top ring. The friction heating between the top ring and the liner is also evaluated. The analysis demonstrates that under some extreme conditions when frictional heating reaches its peak value, some heat flux directs back to enter the ring.

Investigation of Transient Heat Transfer Coefficients in Quenching Experiments

1990 ◽  
Vol 112 (4) ◽  
pp. 843-848 ◽  
Author(s):  
A. M. Osman ◽  
J. V. Beck
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Response ◽  
Transient Heat Transfer ◽  
Transient Temperature ◽  
Empirical Correlations ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Inverse Heat Transfer

Methodological and experimental aspects of the estimation of transient heat transfer coefficients in quenching experiments, using inverse heat transfer methods, were addressed and investigated. Beck’s method was used for the estimation of the transient heat transfer coefficient history from interior transient temperature measurements during quenching. Experiments involved plunging a high-purity copper sphere into cooling baths without boiling. The sphere was instrumented with several interior thermocouples for measuring the transient temperature response during quenching. Water and ethylene glycol were investigated. The early transient values of the heat transfer coefficient history were found to be about 100–120 percent higher than the values predicted using well-known empirical correlations for free convection. The later time values were in good agreement with those predicted with empirical correlations. The transient inverse technique has the capability of estimating early transients and subsequent quasi-steady-state values of heat transfer coefficient in a single transient experiment.

Research on Gradient Heat Treatment of Dual-Property Disk for Alloy FGH96

2013 ◽  
Vol 747-748 ◽  
pp. 783-787
Author(s):  
Yu Wang ◽  
Jin Wen Zou ◽  
Guo Qing Zhang ◽  
Wu Xiang Wang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Treatment ◽  
Transient Temperature ◽  
Heating Process ◽  
Fixture Design ◽  
Dual Property ◽  
Transient Temperature Field ◽  
Heat Treated ◽  
Treatment Experiment

The transient temperature field in the dual-property disk of alloy FGH96 was investigated during the solution heating process of the gradient heat treatment by numerical simulation. The temperature curves for the different locations of the disk were attained. Then, the gradient heat treatment experiment was carried out, and the heat profiles were obtained. The numerical and the experimental results were almost consistent. The method of heat transfer for the bore of the disk was changed evidently through effective fixture design during the gradient heat treatment. The gradient of temperature (ΔT) can reach 121 or more, which lead to a supersolvus heat treated rim and subsolvus heat treated bore for the disk.

Design and Testing of a Carbon Foam Based Supercooler for High Heat Flux Cooling in Optoelectronic Packages

2009 ◽  
Author(s):  
Walter W. Yuen ◽  
Jianping Tu ◽  
Wai-Cheong Tam ◽  
Dan Blumenthal
Keyword(s):  
Heat Flux ◽  
Heated Surface ◽  
Local Maximum ◽  
Carbon Foam ◽  
High Heat ◽  
Maximum Temperature ◽  
Transient Temperature ◽  
High Heat Flux ◽  
Periodic Heating ◽  
Heating Region

The feasibility of using carbon foam as a heat sink and heat spreader in optoelectronic packages is assessed. A “supercooler” is designed, fabricated and tested to verify its cooling capability under high heat flux conditions in a typical optoelectronic package. The supercooler uses carbon foam as a primary heat transfer material. Water is soaked into the carbon foam and under evacuated pressure, boiling is initiated under the heating region to provide enhanced cooling. Experiments were conducted for a heat flux of up to 400 W/cm2 deposited over a heating area of 0.5 mm × 5 mm. Two dimensional transient temperature distributions were recorded using a high speed infrared camera. Data were obtained for steady heating, as well as periodic heating with frequency up to 8 hz. Results show that the supercooler is very efficient in dissipating heat away from the heating region. Data obtained under 8 hz periodic heating with a peak power input of 10W, for example, showed that the temperature of the heated surface rises quickly to a local maximum of 15 to 20 °K above the ambient. The heated surface is then cooled uniformly back to a near ambient condition (with a maximum temperature of less than 5 °K above ambient) during the cooling half of the cycle (less than 0.0625 sec after the heating is turned off). The average cooling rate during the cooling period exceeds 170 °K/s. A numerical model, based on COMSOL, is developed to interpret the experimental data and to provide insights on the relevant physics responsible for the rapid cooling. Numerical data are presented to demonstrate how the supercooler can be further improved and adopted for other applications.

scholarly journals CFD Model for Aircraft Ground Deicing: Verification and Validation of an Extended Enthalpy-Porosity Technique in Particulate Two Phase Flows

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 210
Author(s):  
Sami Ernez ◽  
François Morency
Keyword(s):  
Heat Transfer ◽  
Melting Process ◽  
Transient Temperature ◽  
Ice Melting ◽  
Two Phase ◽  
Transient Temperature Field ◽  
Proposed Model ◽  
Deicing Fluid ◽  
Cfd Method ◽  
Surface Ice

Researchers have focused in the last five years on modelling the aircraft ground deicing process using CFD (computational fluid dynamics) in order to reduce its costs and pollution. As preliminary efforts, those studies did not model the ice melting nor the diffusion between deicing fluids and water resulting from the melting process. This paper proposes a CFD method to simulate this process filling these gaps. A particulate two-phase flow approach is used to model the spray impact on ice near the contaminated surface. Ice melting is modelled using an extended version of the enthalpy-porosity technique. The water resulting from the melting process is diffused into the deicing fluid forming a single-phase film. This paper presents a new model of the process. The model is verified and validated through three steps. (i) verification of the species transport. (ii) validation of the transient temperature field of a mixture. (iii) validation of the convective heat transfer of an impinging spray. The permeability coefficient of the enthalpy-porosity technique is then calibrated. The proposed model proved to be a suitable candidate for a parametric study of the aircraft ground deicing process. On the validation test cases, the precision of heat transfer prediction exceeds 88%. The model has the ability of predicting the deicing time and the deicing fluid quantities needed to decontaminate a surface.

scholarly journals Transient Heat Transfer Analysis for Brake Disks Using SPH

2009 ◽  
Vol 417-418 ◽  
pp. 617-620
Author(s):  
Gui Ming Rong ◽  
Hiroyuki Kisu
Keyword(s):  
Heat Transfer ◽  
Transfer Problem ◽  
Calculation Model ◽  
Heat Transfer Analysis ◽  
Transient Heat Transfer ◽  
Transient Temperature ◽  
Approximation Technique ◽  
Model Calculations ◽  
Various Boundary Conditions ◽  
Emergency Braking

Smoothed particle hydrodynamics (SPH) is a mesh-free numerical approximation technique for simulating various physical problems. A calculation system for transient heat transfer problem by SPH has been improved to deal with various boundary conditions and several model calculations are performed to verify it. As a practical application, the transient temperature field of a brake disk under emergency braking is analyzed. Both solid and ventilated disks are modeled with a moving heat source on the sliding surface. The numerical results show that the temperature sharply fluctuates because of the cyclic loading. Improvement of the calculation model is also discussed.

Effect of Bonding Force on the Conducting Particle With Different Sizes

2003 ◽  
Vol 125 (4) ◽  
pp. 624-629 ◽  
Author(s):  
N. H. Yeung ◽  
Y. C. Chan ◽  
C. W. Tan
Keyword(s):  
Heat Transfer ◽  
Stress Level ◽  
Transfer Problem ◽  
Bonding Temperature ◽  
Heat Transfer Analysis ◽  
Transient Heat Transfer ◽  
Element Analysis ◽  
Bonding Force ◽  
Conducting Particle ◽  
Center Area

Finite element analysis was used to model the transient heat transfer problem and the mechanical influence of the conducting particle in the anisotropic conductive adhesive (ACF). Three-dimensional (3D) brick element was performed for the transient heat transfer analysis, and the result was found that heat was transferred and spread from the die to the ACF and its conducting particle very quickly; in around 0.5 sec the ACF can reach the bonding temperature of 220°C. For the mechanical stress analysis of the conducting particle, the degree of the deformation was increased as the bonding force increased. The conducting particle was subjected to the larger stress level as the smaller of the particle size. The stress concentration was located at the edge area and diminished at the center area. It was also found that the cracks were found at the four corners of the conducting particles which was due to the highest stress level subjected on that location. Moreover, if only considering the plastic particle, the stress level was concentrated at the center area and vanished at the edge area.

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