Estimation of Heat Transfer Coefficients in Dry and Cold-Air Cutting

2010 ◽  
Vol 126-128 ◽  
pp. 341-346 ◽  
Author(s):  
Feng Jiang ◽  
Jian Feng Li ◽  
Jie Sun ◽  
Song Zhang ◽  
Lan Yan
Keyword(s):  
Heat Transfer ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Temperature Dependent ◽  
Element Analysis ◽  
Cold Air ◽  
Heat Transfer Coefficients ◽  
The Finite Element Analysis ◽  
Infra Red ◽  
Cutting Inserts

For the analysis of cooling effect, the cutting inserts were heated to 900°C and then exposed in the room-air and cold-air with different pressure respectively. The temperature variation were recorded by infra-red (IR) pyrometer. The temperature-dependent global heat transfer coefficients were estimated by the theoretical analysis and experimental data. The finite element analysis (FEA) was employed to simulate the cooling process and modify the estimated heat transfer coefficients. The heat transfer coefficients decreased from 55.1 W/m2•°C (800°C) to 9.32 W/m2•°C (350°C) in the natural cooling and approximately 300 W/m2•°C (600°C) to 60 W/m2•°C (300°C) in the cold-air cooling. Cold-air cooling greatly increased the heat transfer coefficients, but it seemed the air pressure had little pressure on the heat transfer coefficients.

Experimental Platforms and Finite Element Analysis on Hot Stamping Processes

2014 ◽  
Vol 1063 ◽  
pp. 334-338 ◽  
Author(s):  
Tzu Hao Hung ◽  
Heng Kuang Tsai ◽  
Fuh Kuo Chen ◽  
Ping Kun Lee
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Process Design ◽  
Hot Stamping ◽  
Boron Steel ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
The Finite Element Analysis

Due to the complexity of hot stamping mechanism, including the coupling of material formability, thermal interaction and metallurgical microstructure, it makes the process design more difficult even with the aid of the finite element analysis. In the present study, the experimental platforms were developed to measure and derive the friction and heat transfer coefficients, respectively. The experiments at various elevated temperatures and contact pressures were conducted and the friction coefficients and heat transfer coefficients were obtained. A finite element model was also established with the experimental data and the material properties of the boron steel calculated from the JMatPro software. The finite element simulations for the hot stamping forming of an automotive door beam, including transportation analysis, hot forming analysis and die quenching analysis were then performed to examine the forming properties of the door beam. The validation of the finite element results by the production part confirms the efficiency and accuracy of the developed experimental platforms and the finite element analysis for the process design of hot stamping.

MEMS Impinging-Jet Cooling

2000 ◽  
Author(s):  
Qiao Lin ◽  
Shuyun Wu ◽  
Yin Yuen ◽  
Yu-Chong Tai ◽  
Chin-Ming Ho
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Jet Cooling

Abstract This paper presents an experimental investigation on MEMS impinging jets as applied to micro heat exchangers. We have fabricated MEMS single and array jet nozzles using DRIE technology, as well as a MEMS quartz chip providing a simulated hot surface for jet impingement. The quartz chip, with an integrated polysilicon thin-film heater and distributed temperature sensors, offers high spatial resolution in temperature measurement due to the low thermal conductivity of quartz. From measured temperature distributions, heat transfer coefficients are computed for single and array micro impinging jets using finite element analysis. The results from this study for the first time provide extensive data on spatial distributions of micro impinging-jet heat transfer coefficients, and demonstrate the viability of MEMS heat exchangers that use micro impinging jets.

A Study of Forced Convection Direct Air Cooling in the Downstream Vicinity of Heat Sinks

1990 ◽  
Vol 112 (3) ◽  
pp. 234-240 ◽  
Author(s):  
G. L. Lehmann ◽  
S. J. Kosteva
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Packaging System ◽  
Transfer Rates ◽  
Heat Transfer Coefficients

An experimental study of forced convection heat transfer is reported. Direct air cooling of an electronics packaging system is modeled by a channel flow, with an array of uniformly sized and spaced elements attached to one channel wall. The presence of a single or complete row of longitudinally finned heat sinks creates a modified flow pattern. Convective heat transfer rates at downstream positions are measured and compared to that of a plain array (no heat sinks). Heat transfer rates are described in terms of adiabatic heat transfer coefficients and thermal wake functions. Empirical correlations are presented for both variations in Reynolds number (5000 < Re < 20,000) and heat sink geometry. It is found that the presence of a heat sink can both enhance and degrade the heat transfer coefficient at downstream locations, depending on the relative position.

scholarly journals Online Fatigue-Monitoring Models with Consideration of Temperature Dependent Properties and Varying Heat Transfer Coefficients

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
HengLiang Zhang ◽  
Shi Liu ◽  
Danmei Xie ◽  
Yangheng Xiong ◽  
Yanzhi Yu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Stress ◽  
Transfer Coefficient ◽  
Green’S Function ◽  
Green's Function ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Temperature Dependent ◽  
Heat Transfer Coefficients

Thermal stress failure caused by alternating operational loads is the one of important damage mechanisms in the nuclear power plants. To evaluate the thermal stress responses, the Green’s function approach has been generally used. In this paper, a method to consider varying heat transfer coefficients when using the Green’s function method is proposed by using artificial parameter method and superposition principle. Time dependent heat transfer coefficient has been treated by using a modified fluid temperature and a constant heat transfer coefficient. Three-dimensional temperature and stress analyses reflecting entire geometry and heat transfer properties are required to obtain accurate results. An efficient and accurate method is confirmed by comparing its result with corresponding 3D finite element analysis results for a reactor pressure vessel (RPV). From the results, it is found that the temperature dependent material properties and varying heat transfer coefficients can significantly affect the peak stresses and the proposed method can reduce computational efforts with satisfactory accuracy.

Squeal and Thermal Analysis of Automobile Disc Brake Rotors

2015 ◽  
Vol 764-765 ◽  
pp. 369-373
Author(s):  
Wei Hsin Gau ◽  
Kun Nan Chen ◽  
Chin Yuan Hung
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Finite Element ◽  
Aluminum Alloy ◽  
Cast Iron ◽  
Cfd Simulation ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Brake Rotors

The brakes of an automobile are among the most critical components regarding the safety features, and disc brakes are the most common type used in passenger vehicles. In this research, the squeal phenomena of a swirl-vent brake rotor and the thermal analysis of two straight-vent brake rotors, made of cast-iron and aluminum-alloy, are investigated. For the squeal analysis, finite element models are created and analyzed using a prestressed modal analysis with complex eigen-solutions. For the thermal analysis, heat transfer coefficients on the surfaces of a rotor as functions of time are first estimated by CFD simulation, and then imported to a thermal analysis program as the boundary condition. Finally, the temperature distribution of the rotor can be calculated by finite element analysis. The simulation results show that vortices will arise in the vented passages of straight-vent rotors, which means less heat carried away and lower heat transfer coefficients. The swirl-vent brake design is clearly better for thermal ventilation. Furthermore, under the same condition, aluminum-alloy rotors exhibit more uniform temperature distributions with smaller temperature gradients than cast-iron rotors do.

Modeling of Wellbore Overall Heat Transfer in Circulation

2012 ◽  
Vol 260-261 ◽  
pp. 537-542
Author(s):  
Hui Fang Song ◽  
Rui He Wang ◽  
Hong Jian Ni
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Steady State ◽  
Radial Direction ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Temperature Calculation ◽  
Wellbore Pressure ◽  
Film Heat Transfer

Heat is transferred between the fluid and the surroundings in the wellbore. Quantitative knowledge of wellbore heat transfer is important in drilling and production operations. A new model of wellbore heat transfer using finite element analysis is developed in this study. This solution assumes the heat transfer in the wellbore is steady state and only happens in radial direction. The model considers heat gained due to wellbore pressure loss in circulation, which is more accurate in temperature calculation. The overall heat resistance in the wellbore is analyzed, taking into account the film heat transfer coefficients difference between the tube and the annulus. Previous literature has been reviewed to determine the correlation which can be used in the model.

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