A Convective-Heat Transfer Model for Underground Combustion

1968 ◽  
Vol 8 (04) ◽  
pp. 323-324
Author(s):  
C.H. Kuo
Keyword(s):  
Temperature Distribution ◽  
Convective Heat ◽  
Heat Generation ◽  
Temperature Rise ◽  
Combustion Front ◽  
Combustion Process ◽  
Front Velocity ◽  
Paradoxical Result ◽  
Heat Recuperation ◽  
Heat Front

In the underground combustion process, part of the heat generated at the combustion front is carried downstream by convection. Temperature distribution in the combustion process can be obtained by including a delta function for heat generation at the combustion surface. This is similar to the hot-fluid injection model of Lauwerier. The dimensionless temperature in the reservoir, phi T1(x, t), and the overburden, phi T2(x, y, t), are as follows: ..........................................(1) ..........................................(2) The ratio R of the heat-front velocity, u, h, to the combustion front velocity, uc, is one of the most important factors governing the temperature distribution in the pay zone. For cases of ub less than uc, no heat is carried ahead of the combustion front and the temperature at the combustion front remains constant for all times. The fraction of the heat stored between the heat front and the combustion front decreases as the time increases. This is because more of the heat is consumed in heating the formation behind the heat front and in heating the cap and bass rock. A more advantageous condition obtains for uh is greater than uc. For this case, the formation ahead of the combustion front is preheated and the amount of heat in this region increases with time. Therefore, due to heat generation and preheating, the total temperature rise at the combustion front also increases with time. Eq. 1 also shows that the temperature at the combustion front is higher at a given time for a thinner reservoir. This seemingly paradoxical result takes place because the amount paradoxical result takes place because the amount of heat recovered from the overburden and subrock upstream of the combustion front is almost independent of the pay zone thickness. On the other hand, this heat is distributed in the pay zone, which has a heat content directly proportional to the formation thickness b. For thin reservoirs, therefore, the temperature rise in the pay zone due to heat recuperation is higher than that in thick reservoirs. For very thick pay zones (h-oo) there would be no heat recuperation, and consequently the combustion- front temperatures would be lowest. For many cases encountered, uh is smaller than uc. Convective-heat transport. ahead of the combustion front can be achieved by increasing uh to obtain the condition uh, >uc. The wet and partially quenched combustion processes have a similar objective. The temperature at the combustion front, however, decreases as the uh/uc ratio increases. If this temperature should fall below the ignition point, the fire would die out. Consequently, at any point, the fire would die out. Consequently, at any time there exists a maximum ratio of uh/uc for which the formation ahead of the combustion front can be heated to increase oil mobility while combustion is maintained. For the case where the heat front moves faster than the combustion front (uh is greater than uc), the downstream heat efficiency E can be derived by applying the integration method given in Ref. 3. P. 323

Correlation of Electronic and Thermal Properties of Short Channel nMOSFETS

1999 ◽  
Author(s):  
M. Palaniappan ◽  
V. Ng ◽  
R. Heiderhoff ◽  
J.C.H. Phang ◽  
G.B.M. Fiege ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Temperature Distribution ◽  
Heat Generation ◽  
Hot Spots ◽  
Light Emission ◽  
Photon Emission ◽  
Thermal Image ◽  
Short Channel ◽  
Physical Phenomena ◽  
Backside Illuminated

Abstract Light emission and heat generation of Si devices have become important in understanding physical phenomena in device degradation and breakdown mechanisms. This paper correlates the photon emission with the temperature distribution of a short channel nMOSFET. Investigations have been carried out to localize and characterize the hot spots using a spectroscopic photon emission microscope and a scanning thermal microscope. Frontside investigations have been carried out and are compared and discussed with backside investigations. A method has been developed to register the backside thermal image with the backside illuminated image.

Finite element method estimation of temperature distribution of automotive tire using one-way-coupled method

2021 ◽  
pp. 095440702110087
Author(s):  
Zumrat Usmanova ◽  
Emin Sunbuloglu
Keyword(s):  
Thermal Analysis ◽  
Temperature Distribution ◽  
Heat Generation ◽  
Complex Geometry ◽  
Rolling Resistance ◽  
Operating Conditions ◽  
Deformation Analysis ◽  
Coupled Method ◽  
Experimental Values ◽  
Hysteretic Loss

Numerical simulation of automotive tires is still a challenging problem due to their complex geometry and structures, as well as the non-uniform loading and operating conditions. Hysteretic loss and rolling resistance are the most crucial features of tire design for engineers. A decoupled numerical model was proposed to predict hysteretic loss and temperature distribution in a tire, however temperature dependent material properties being utilized only during the heat generation analysis stage. Cyclic change of strain energy values was extracted from 3-D deformation analysis, which was further used in a thermal analysis as input to predict temperature distribution and thermal heat generation due to hysteretic loss. This method was compared with the decoupled model where temperature dependence was ignored in both deformation and thermal analysis stages. Deformation analysis results were compared with experimental data available. The proposed method of numerical modeling was quite accurate and results were found to be close to the actual tire behavior. It was shown that one-way-coupled method provides rolling resistance and peak temperature values that are in agreement with experimental values as well.

An improved model on forecasting temperature rise of high-speed angular contact ball bearings considering structural constraints

2018 ◽  
Vol 70 (1) ◽  
pp. 15-22 ◽  
Author(s):  
De-xing Zheng ◽  
Weifang Chen ◽  
Miaomiao Li
Keyword(s):  
Heat Generation ◽  
Temperature Rise ◽  
High Speed ◽  
Structural Constraints ◽  
Ball Bearings ◽  
Content Type ◽  
Grid Model ◽  
Simulation Results ◽  
Operation Parameters ◽  
Improved Model

Purpose Thermal performances are key factors impacting the operation of angular contact ball bearings. Heat generation and transfer about angular contact ball bearings, however, have not been addressed thoroughly. So far, most researchers only considered the convection effect between bearing housings and air, whereas the cooling/lubrication operation parameters and configuration effect were not taken into account when analyzing the thermal behaviors of bearings. This paper aims to analyze the structural constraints of high-speed spindle, structural features of bearing, heat conduction and convection to study the heat generation and transfer of high-speed angular contact ball bearings. Design/methodology/approach Based on the generalized Ohm’s law, the thermal grid model of angular contact ball bearing of high-speed spindle was first established. Next Gauss–Seidel method was used to solve the equations group by Matlab, and the nodes temperature was calculated. Finally, the bearing temperature rise was tested, and the comparative analysis was made with the simulation results. Findings The results indicate that the simulation results of bearing temperature rise for the proposed model are in better agreement with the test values. So, the thermal grid model established is verified. Originality/value This paper shows an improved model on forecasting temperature rise of high-speed angular contact ball bearings. In modeling, the cooling/lubrication operation parameters and structural constraints are integrated. As a result, the bearing temperature variation can be forecasted more accurately, which may be beneficial to improve bearing operating accuracy and bearing service life.

scholarly journals Heat Localization in the Medium in Blow-Up Regime

2020 ◽  
Keyword(s):  
Temperature Distribution ◽  
Blow Up ◽  
Maximum Temperature ◽  
Heating Regime ◽  
Heating And Cooling ◽  
Localized Heating ◽  
Finite Period ◽  
Equation Of Heat Conduction ◽  
The Given ◽  
Heat Front

The existence of the effect of heat metastable localization in the medium in the blow-up heating regime was experimentally proved. This is the regime in which the heating energy for a finite period of time tends to infinity. Previous theoretical studies have shown that in this case some regions, inside of which the temperature increases, may arise, while their size remains constant or decreases with time (heat localization regions). These regions exist as long as there is some energy input from the outside. An installation for the experimental study of the thermal blow-up regimes in a solid was developed. The object of research was an aluminum rod with a heater at its end. The temperature distribution along the rod was measured with thermocouples. The temperature of the rod end could vary according to the given law. Calibration of the installation was performed. The sensitivity of thermocouples was determined. The inertia of the heating and cooling process was estimated. The mathematical description of the thermal processes, occurring during the experiment, was made. The nonlinear equation of heat conduction for the rod was solved, with the heat exchange with the environment by convection and radiation taken into account. The thermal regime at the boundary, which is necessary to create the thermal structures, was determined. The temperature distribution in the rod in the blow-up regime and non-blow-up regime was measured. In the blow-up regime the heat front (the coordinate of the point with the temperature equal to half the maximum temperature) initially shifts from the heat source, and then in the opposite direction, and the size of the area under heating decreases. In the non-blow-up regime the size of the heated region increases all the time. The predicted effect was supposed to be used in installations for thermonuclear fusion where the target was heated by laser radiation pulses of a special shape. This effect can also be used for localized heating in cutting and welding, when the adjacent regions are not to get very hot, and in other similar situations.

Investigation of Bending Fatigue of Composite Plates by Using Infrared Thermography

2011 ◽  
Vol 268-270 ◽  
pp. 406-411 ◽  
Author(s):  
Ömer Sinan Şahin ◽  
Murat Selek ◽  
Şirzat Kahramanlı
Keyword(s):  
Infrared Thermography ◽  
Heat Generation ◽  
Temperature Rise ◽  
Epoxy Composite ◽  
Composite Plates ◽  
Fatigue Loading ◽  
Thermal Camera ◽  
Thermal Images ◽  
Bending Fatigue ◽  
Damage Initiation

In this study, the temperature rise of composite plates with a hole during fatigue loading was investigated. Woven glass/epoxy composite plates with eight plies were subjected to bending fatigue loading and materials were observed by using a thermal camera during the test. Previous works showed that a heat generation can form due to internal friction and damage formation. Therefore, a thermographic infrared imaging system was used to detect the temperature rise of composite specimens. During the tests, the thermal images of the specimens have been recorded by a thermal camera and then transferred to the image processing program which has been developed by using MATLAB. By using these thermal images, the spot temperatures of the specimen were obtained by using artificial neural networks. The obtained temperatures show local increase at places where the heat generation localized. These regions considered being the probable damage initiation sites. It is shown in this study that most probable damage initiation zones in the woven glass/epoxy composite material can be detected by using infrared thermography (IRT) approach prior to failure.

Hysteresis Heating of Railroad Bearing Thermoplastic Elastomer Suspension Element

2017 ◽  
Author(s):  
Oscar O. Rodriguez ◽  
Arturo A. Fuentes ◽  
Constantine Tarawneh ◽  
Robert E. Jones
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Steady State ◽  
Temperature Distribution ◽  
Heat Generation ◽  
Internal Heat ◽  
Thermoplastic Elastomer ◽  
Internal Heat Generation ◽  
Element Analysis ◽  
Railroad Bearing

Thermoplastic elastomers (TPE’s) are increasingly being used in rail service in load damping applications. They are superior to traditional elastomers primarily in their ease of fabrication. Like traditional elastomers they offer benefits including reduction in noise emissions and improved wear resistance in metal components that are in contact with such parts in the railcar suspension system. However, viscoelastic materials, such as the railroad bearing thermoplastic elastomer suspension element (or elastomeric pad), are known to develop self-heating (hysteresis) under cyclic loading, which can lead to undesirable consequences. Quantifying the hysteresis heating of the pad during operation is therefore essential to predict its dynamic response and structural integrity, as well as, to predict and understand the heat transfer paths from bearings into the truck assembly and other contacting components. This study investigates the internal heat generation in the suspension pad and its impact on the complete bearing assembly dynamics and thermal profile. Specifically, this paper presents an experimentally validated finite element thermal model of the elastomeric pad and its internal heat generation. The steady-state and transient-state temperature profiles produced by hysteresis heating of the elastomer pad are developed through a series of experiments and finite element analysis. The hysteresis heating is induced by the internal heat generation, which is a function of the loss modulus, strain, and frequency. Based on previous experimental studies, estimations of internally generated heat were obtained. The calculations show that the internal heat generation is impacted by temperature and frequency. At higher frequencies, the internally generated heat is significantly greater compared to lower frequencies, and at higher temperatures, the internally generated heat is significantly less compared to lower temperatures. However, during service operation, exposure of the suspension pad to higher loading frequencies above 10 Hz is less likely to occur. Therefore, internal heat generation values that have a significant impact on the suspension pad steady-state temperature are less likely to be reached. The commercial software package ALGOR 20.3TM is used to conduct the thermal finite element analysis. Different internal heating scenarios are simulated with the purpose of obtaining the bearing suspension element temperature distribution during normal and abnormal conditions. The results presented in this paper can be used in the future to acquire temperature distribution maps of complete bearing assemblies in service conditions and enable a refined model for the evolution of bearing temperature during operation.

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