Evaluation of the Effect of Cooling Conditions and Heat Transfer Coefficients on Solidification of Al-Cu Binary Alloy in Static Casting Process

2020 ◽  
Vol 1158 ◽  
pp. 1-16
Author(s):  
Chijioke Peter Egole ◽  
Henry E. Mgbemere ◽  
Gbeminiyi M. Sobamowo ◽  
Ganiyu I. Lawal
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Solid Fraction ◽  
Heat Extraction ◽  
Surface Tension Gradient ◽  
Cooling Curves ◽  
Source Terms ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Cooling Conditions

Source-based method for modelling solidification problems have been modified and presented in the current work. It coupled the effect of thermal radiation to macro-transport codes and was solved using finite volume method. The problem was formulated based on the classic continuum energy conservation equation for transient conduction controlled solidification system. Radiation heat transfer and latent heat evolution were added as source terms and solved with appropriate numerical treatments to obtain a system of linearized source terms. This circumvented the need for the application of any analytical solution to the intricate heat transfer regimes included in the model. The effect of cooling was carried out under various cooling conditions imposed on different surfaces of the mould for the solidifying metal. The resultant influence of cooling on the solid fraction evolution during static casting was then evaluated. The simulated cooling curves show that thermal radiation have no influence on the rate of heat extraction and the results show that the predicted cooling curves and solid fraction updates are similar to the results of previous models. The predicted curves at the top section of the open mould however show a little deviation due to effect of surface tension gradient forces. It was further revealed that heat transfer coefficients has more effect cooling curves and temperature contours at the lateral mould surfaces than the interior of the casting which is in agreement with theory of Newtonian cooling.

scholarly journals The Effect of Cooling Agent on Stress and Deformation of Charge-loaded Cast Pallets

2017 ◽  
Vol 17 (4) ◽  
pp. 13-18
Author(s):  
A. Bajwoluk ◽  
P. Gutowski
Keyword(s):  
Heat Transfer ◽  
Heat Treatment ◽  
Temperature Gradient ◽  
Effect Of Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Cooling Conditions ◽  
Cooling Agent ◽  
Stress And Deformation ◽  
A Charge

Abstract The results of research on the effect of the type of cooling agent used during heat treatment and thermal-chemical treatment on the formation of temperature gradient and stress-deformation distribution in cast pallets, which are part of furnace accessories used in this treatment, are disclosed. During operation, pallets are exposed to the effect of the same conditions as the charge they are carrying. Cyclic thermal loads are the main cause of excessive deformations or cracks, which after some time of the cast pallet operation result in its withdrawal due to damage. One of the major causes of this damage are stresses formed under the effect of temperature gradient in the unevenly cooled pallet construction. Studies focused on the analysis of heat flow in a charge-loaded pallet, cooled by various cooling agents characterized by different heat transfer coefficients and temperature. Based on the obtained temperature distribution, the stress distribution and the resulting deformation were examined. The results enabled drawing relevant conclusions about the effect of cooling conditions on stresses formed in the direction of the largest temperature gradient.

Numerical Simulation on the Temperature Field of Steel 1045 Quenched by Different Hardening Media

2013 ◽  
Vol 444-445 ◽  
pp. 1222-1228
Author(s):  
Jian Bin Xie ◽  
Chang Chang Wu ◽  
Jing Fan ◽  
Miao Fu ◽  
Deng Feng Hu
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Temperature Field ◽  
Temperature Fields ◽  
Cooling Curves ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Theory ◽  
Quenching Process ◽  
Estimate Method

Based on the experimental measured cooling curves and the boiling heat transfer theory, the inverse problem of nonlinear heat conduct equation for Steel 1045 quenched by different hardening media was established by functional analysis and finite element method, and the surface heat-transfer coefficients in continuous cooling during quenching were calculated by nonlinear estimate method. Then the constitutive model of Steel 1045 during quenching was established subsequently. Finally, the temperature field of Steel 1045 cylinder quenched by different hardening media was simulated by Finite Element Methods (FEM). Results show that the calculated temperature fields agree with the practical quenching process.

scholarly journals Performance Optimization of Unglazed Nanofluid Photovoltaic/Thermal System: Energy and Exergy Analyses

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
M. Imtiaz Hussain ◽  
Jun-Tae Kim
Keyword(s):  
Heat Transfer ◽  
Performance Optimization ◽  
Pure Water ◽  
Operating Conditions ◽  
Heat Extraction ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Energy And Exergy ◽  
Exergy Analyses ◽  
T System

The focus of this paper is to predict the transient response of a nanoengineered photovoltaic thermal (PV/T) system in view of energy and exergy analyses. Instead of a circular-shaped receiver, a trapezoidal-shaped receiver is employed to increase heat transfer surface area with photovoltaic (PV) cells for improvement of heat extraction and thus achievement of a higher PV/T system efficiency. The dynamic mathematical model is developed using MATLAB® software by considering real-time heat transfer coefficients. The proposed model is validated with experimental data from a previous study. Negligible discrepancies were found between measured and predicted data. The validated model was further investigated in detail using different nanofluids by dispersing copper oxide (CuO) and aluminum oxide (Al2O3) in pure water. The overall performance of the nanoengineered PV/T system was compared to that of a PV/T system using water only, and optimal operating conditions were determined for maximum useful energy and exergy rates. The results indicated that the CuO/water nanofluid has a notable impact on the energy and exergy efficiencies of the PV/T system compared to that of Al2O3/water nanofluid and water only cases.

scholarly journals Heat Transfer Coefficients and Quenching Performance of Vegetable Oils

2019 ◽  
Author(s):  
Jianfeng Gu ◽  
Jun Xu ◽  
Rosa L. Simencio Otero ◽  
Jônatas M. Viscaino ◽  
Lauralice C.F. Canale ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Vegetable Oils ◽  
Materials Science ◽  
Similar Data ◽  
Cooling Curves ◽  
Transfer Coefficients ◽  
Inconel 600 ◽  
Heat Transfer Coefficients ◽  
Materials Science And Engineering ◽  
Petroleum Oil

Abstract Vegetable oils are currently using basestocks for biodegradable and renewable quenchant formulation. However, there are relatively few references relating to their true equivalence, or lack thereof, relative to the quenching performance of petroleum oil-based quenchant formulations. To obtain an overview of the variability of vegetable oil quenching performance, cooling curves were determined, and the heat transfer coefficient profiles were calculated at the Institute of Materials Modification and Modeling School of Materials Science and Engineering in Shanghai, China. The vegetable oils that were studied included canola and palm oils. Cooling curves were obtained using the Tensi multiple surface thermocouple 15 mm diameter x 45 mm cylindrical Inconel 600 probe. For comparison, similar data were obtained with Houghtoquench HKM, an accelerated petroleum oil quenchant. The results of this work will be discussed here.

An Experimental and Numerical Investigation into the Thermal Behavior of the Pressure Die Casting Process

1999 ◽  
Vol 122 (1) ◽  
pp. 90-99 ◽  
Author(s):  
S. Bounds ◽  
K. Davey ◽  
S. Hinduja
Keyword(s):  
Heat Transfer ◽  
Die Casting ◽  
Casting Process ◽  
Heat Extraction ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Die Casting Process ◽  
Pressure Die Casting ◽  
Element Method

The modeling of the pressure die casting process generally requires the specification of heat transfer coefficients at the surfaces of the die. The coefficients at the cavity-casting interface and at the cooling channel surfaces are of particular importance. In order to provide estimates for these heat transfer coefficients, the behavior of a specifically designed zinc alloy casting is investigated using a three dimensional thermal model whose predictions are supported by experimentally obtained results. The numerical model uses the boundary element method for the dies, as surface temperatures are of particular importance, and the finite element method for the casting, where the nonlinear material behavior makes this technique suitable. The experimental data comprises of thermocouple measurements of both die, casting, and coolant temperatures for three sets of operating conditions. These measurements are complemented by qualitative data of casting defects caused by incomplete solidification and thermal imaging temperature measurements. An experimental technique for obtaining average heat transfer coefficients for the casting–die interface is presented. Although the technique circumvents the need to place thermocouples in the casting and provides average heat transfer coefficients of sufficient accuracy for modeling purposes, it is not sufficiently responsive to provide accurate transient information. The presence of coolant boiling is detected by its effect on the rates of heat extraction. Heat transfer coefficients are determined for the cooling channels using a boiling model. Comparison between predicted and experimental rates of heat transfer to the coolant support the need for a boiling model. Good agreement is obtained between experimental and numerical predictions. [S1087-1357(00)00601-8]

Heat Transfer Impact of Synthetic Jets for Air-Cooled Array of Fins

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Ri Li ◽  
William D. Gerstler ◽  
Mehmet Arik ◽  
Benjamin Vanderploeg
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Synthetic Jets ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Cooling Conditions ◽  
Multiple Jets ◽  
Cooling Enhancement

Free convection air cooling from a vertically placed heat sink is enhanced by upward concurrent pulsated air flow generated by mesoscale synthetic jets. The cooling enhancement is experimentally studied. An enhancement factor is introduced and defined as the ratio of convection heat transfer coefficients for jet-on (enhanced convection) to jet-off (natural convection) cooling conditions. To obtain the two coefficients, heat transfer by radiation is excluded. A high-resolution infrared (IR) camera is used to capture detailed local temperature distribution on the heat sink surface under both cooling conditions. Analysis is carried out to obtain local convection heat transfer coefficients based on measured local surface temperatures. The enhancement of convectional cooling by synthetic jets can be then quantified both locally and globally for the entire heat sink. Two categories of thermal tests are conducted. First, tests are conducted with a single jet to investigate the effects of jet placement and orifice size on cooling enhancement, while multiple jets are tested to understand how cooling performance changes with the number of jets. It is found that the cooling enhancement is considerably sensitive to jet placement. Jet flow directly blowing on fins provides more significant enhancement than blowing through the channel between fins. When using one jet, the enhancement ranges from 1.6 to 1.9 times. When multiple jets are used, the heat transfer enhancement increases from 3.3 times for using three jets to 4.8 times for using five jets. However, for practical thermal designs, increasing the number of jets increases the power consumption. Hence, a new parameter, “jet impact factor (JIF),” is defined to quantify the enhancement contribution per jet. JIF is found to change with the number of jets. For example, the four-jet configuration shows higher JIF due to higher contribution per jet than both three-jet and five-jet configurations.

The Effect of Surface Thermal Radiation on Heat Transfer in a Ventilated Cavity

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
J. M. A. Navarro ◽  
J. F. Hinojosa ◽  
A. Piña-Ortiz ◽  
J. Xamán
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Turbulence Models ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Ventilated Cavity ◽  
Experimental Heat Transfer ◽  
Effect Of Surface

Abstract In this work, experimental and numerical results were obtained to analyze the effect of surface thermal radiation on heat transfer by mixed convection in a ventilated cavity. Experimental temperature profiles were obtained at six different depths and heights consisting of 14 thermocouples each. Five turbulence models were evaluated against experimental data. The radiative heat transfer model was solved with the discrete ordinate method. The effect of thermal radiation on experimental heat transfer coefficients is significant; it increases between 87% (Re = 30,372 and Ra = 3.04 × 1011) and 110% (Re = 6021 and Ra = 2.27 × 1011), when the emissivity of the walls increases from 0.03 to 0.98.

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