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.

scholarly journals Reproduction of melting behavior for vitrified hillforts based on amphibolite, granite, and basalt lithologies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
John S. McCloy ◽  
José Marcial ◽  
Jack S. Clarke ◽  
Mostafa Ahmadzadeh ◽  
John A. Wolff ◽  
...  
Keyword(s):  
Iron Age ◽  
Glass Production ◽  
Melting Behavior ◽  
Source Rocks ◽  
Ex Situ ◽  
Maximum Temperature ◽  
Heating And Cooling ◽  
Heat Treated ◽  
Granitoid Rocks ◽  
Dark Glass

AbstractEuropean Bronze and Iron Age vitrified hillforts have been known since the 1700s, but archaeological interpretations regarding their function and use are still debated. We carried out a series of experiments to constrain conditions that led to the vitrification of the inner wall rocks in the hillfort at Broborg, Sweden. Potential source rocks were collected locally and heat treated in the laboratory, varying maximum temperature, cooling rate, and starting particle size. Crystalline and amorphous phases were quantified using X-ray diffraction both in situ, during heating and cooling, and ex situ, after heating and quenching. Textures, phases, and glass compositions obtained were compared with those for rock samples from the vitrified part of the wall, as well as with equilibrium crystallization calculations. ‘Dark glass’ and its associated minerals formed from amphibolite or dolerite rocks melted at 1000–1200 °C under reducing atmosphere then slow cooled. ‘Clear glass’ formed from non-equilibrium partial melting of feldspar in granitoid rocks. This study aids archaeological forensic investigation of vitrified hillforts and interpretation of source rock material by mapping mineralogical changes and glass production under various heating conditions.

Direct observation of three-dimensional transient temperature distribution in SiC Schottky barrier diode under operation by optical-interference contactless thermometry (OICT) imaging

2022 ◽  
Author(s):  
Keiya Fujimoto ◽  
Hiroaki Hanafusa ◽  
Takuma Sato ◽  
Seiichiro HIGASHI
Keyword(s):  
Temperature Distribution ◽  
Schottky Barrier ◽  
Hot Spot ◽  
Local Heating ◽  
Three Dimensional ◽  
Schottky Barrier Diode ◽  
Transient Temperature ◽  
Optical Interference ◽  
Transient Temperature Distribution ◽  
Heating And Cooling

Abstract We have developed optical-interference contactless thermometry (OICT) imaging technique to visualize three-dimensional transient temperature distribution in 4H-SiC Schottky barrier diode (SBD) under operation. When a 1 ms forward pulse bias was applied, clear variation of optical interference fringes induced by self-heating and cooling were observed. Thermal diffusion and optical analysis revealed three-dimensional temperature distribution with high spatial (≤ 10 μm) and temporal (≤ 100 μs) resolutions. A hot spot that signals breakdown of the SBD was successfully captured as an anormal interference, which indicated a local heating to a temperature as high as 805 K at the time of failure.

Electromagnetic performance and thermal analysis of a novel permanent magnet fluxed-switching coupler

2021 ◽  
pp. 1-18
Author(s):  
Lezhi Ye ◽  
Yulong Zhang ◽  
Mingguang Cao
Keyword(s):  
Temperature Distribution ◽  
Permanent Magnet ◽  
Permanent Magnets ◽  
Three Dimensional ◽  
Load Condition ◽  
Maximum Load ◽  
Maximum Temperature ◽  
The Novel ◽  
Transient Field ◽  
Three Dimensional Finite Element

To solve the problem of complex operating device and permanent magnets (PMs) demagnetization at high temperature, a new type of permanent magnet fluxed-switching coupler (PMC) with synchronous rotating adjuster is proposed. Its torque can be adjusted by rotating a switched flux angle between the adjuster and PMs along the circumferential direction. The structural feature and working principle of the PMC are introduced. The analytical model of the novel PMC was established. The torque curves are calculated in transient field by using the three-dimensional finite element method (3-D FEM). The temperature distribution of the novel PMC under rated condition is calculated by 3-D FEM, and the temperature distribution of the PM is compared with that of the conventional PMC. The simulation and test results show that the maximum temperature of copper disc and PM of the novel PMC are 100 °C and 48 °C respectively. The novel PMC can work stably for a long time under the maximum load condition.

The impact of technology on architecture in Iran with focus on saving in energy consumption

2015 ◽  
Vol 16 (SE) ◽  
pp. 97-103
Author(s):  
Allah Bakhsh Kavoosi ◽  
Shahin Heidari ◽  
Hamed Mazaherian
Keyword(s):  
Energy Consumption ◽  
Energy Demand ◽  
Industrial Revolution ◽  
Demand Prediction ◽  
Interior Spaces ◽  
Heating And Cooling ◽  
Impact Of Technology ◽  
Contemporary Architecture ◽  
The Impact ◽  
The Given

Growth and development of technology caused enormous transformation and change in the world after Industrial Revolution. The contemporary human has prepared the platform for their realization in many activities that the humans were unable to do it in the past time and struck the dream of their realization in their mind so that today doing many of those activities have been apparently practical by human. This accelerating growth accompanied with consuming a lot of energy where with respect to restriction of the given existing resources, it created energy crises. On the other hand, along with growth in industry and requirement for manpower and immigration from village to city and basic architectural changes in houses, which have emerged due to change in social structure it has led to change in lifestyle and type and quantity of consuming energy in contemporary architecture. Inter alia, with increase in human’s capability, cooling and heating and acoustic and lighting technologies were also changed in architecture and using mechanical system was replaced by traditional systems. Application of modern systems, which resulted from growth of industry and development of technology and it unfortunately, caused further manipulation in nature and destruction of it by human in addition to improving capability and potential of human’s creativity. With respect to growth of population and further need for housing and tendency to the dependent heating and cooling systems to them in this article we may notice that the housing is assumed as the greatest consumer of energy to create balance among the exterior and interior spaces in line with creating welfare conditions for heating and cooling and lighting. The tables of energy demand prediction in Iran show that these costs and energy consumption will be dubbed with energy control smart management in architecture.

scholarly journals Research on Influence of Different Simulation Methods of Bypass Flow in Thermal Hydraulic Analysis on Temperature Distribution in HTR-10

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Shiyan Sun ◽  
Youjie Zhang ◽  
Yanhua Zheng
Keyword(s):  
Temperature Distribution ◽  
Reactor Core ◽  
Flow Distribution ◽  
Maximum Temperature ◽  
Flow Ratio ◽  
Hydraulic Analysis ◽  
Bypass Flow ◽  
Pebble Bed ◽  
The Core ◽  
Thermal Hydraulic Analysis

In pebble-bed high temperature gas-cooled reactor, gaps widely exist between graphite blocks and carbon bricks in the reactor core vessel. The bypass helium flowing through the gaps affects the flow distribution of the core and weakens the effective cooling of the core by helium, which in turn affects the temperature distribution and the safety features of the reactor. In this paper, the thermal hydraulic analysis models of HTR-10 with bypass flow channels simulated at different positions are designed based on the flow distribution scheme of the original core models and combined with the actual position of the core bypass flow. The results show that the bypass coolant flowing through the reflectors enhances the heat transfer of the nearby components efficiently. The temperature of the side reflectors and the carbon bricks is much lower with more side bypass coolant. The temperature distribution of the central region in the pebble bed is affected by the bypass flow positions slightly, while that of the peripheral area is affected significantly. The maximum temperature of the helium, the surface, and center of the fuel elements rises as the bypass flow ratio becomes larger, while the temperature difference between them almost keeps constant. When the flow ratio of each part keeps constant, the maximum temperature almost does not change with different bypass flow positions.

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

The Effect of Curvature and Torsion on the Temperature Distribution in a Helix

1985 ◽  
Vol 52 (3) ◽  
pp. 529-532 ◽  
Author(s):  
D. D. Sayers ◽  
M. C. Potter
Keyword(s):  
Differential Equation ◽  
Finite Element Method ◽  
Partial Differential Equation ◽  
Temperature Distribution ◽  
Strong Dependence ◽  
Maximum Temperature ◽  
Nonuniform Heating ◽  
The Finite Element Method ◽  
Curvature Parameter ◽  
Curvature And Torsion

Traditional analysis treats the helix as a straight wire with the effects of nonuniform heating, torsion, and large curvature ignored. Using a helical coordinate system the governing partial differential equation including these effects is derived. The equation is then solved numerically using the finite element method. The results indicate a strong dependence of the temperature on the torsion parameter when the curvature parameter is significant. As the curvature parameter increases, the temperature distribution becomes skew-symmetric and the maximum temperature in the helix increases. Nonuniform heating influences the temperature distribution independent of the curvature and torsion.

scholarly journals Simplified Grinding Temperature Model Study

2019 ◽  
Vol 6 (2) ◽  
pp. a1-a7
Author(s):  
N. V. Lishchenko ◽  
V. P. Larshin ◽  
H. Krachunov
Keyword(s):  
Differential Equation ◽  
Heat Conduction ◽  
Heat Source ◽  
Boundary Conditions ◽  
Grinding Temperature ◽  
Temperature Model ◽  
One Dimensional ◽  
Heating And Cooling ◽  
Equation Of Heat Conduction ◽  
The One

A study of a simplified mathematical model for determining the grinding temperature is performed. According to the obtained results, the equations of this model differ slightly from the corresponding more exact solution of the one-dimensional differential equation of heat conduction under the boundary conditions of the second kind. The model under study is represented by a system of two equations that describe the grinding temperature at the heating and cooling stages without the use of forced cooling. The scope of the studied model corresponds to the modern technological operations of grinding on CNC machines for conditions where the numerical value of the Peclet number is more than 4. This, in turn, corresponds to the Jaeger criterion for the so-called fast-moving heat source, for which the operation parameter of the workpiece velocity may be equivalently (in temperature) replaced by the action time of the heat source. This makes it possible to use a simpler solution of the one-dimensional differential equation of heat conduction at the boundary conditions of the second kind (one-dimensional analytical model) instead of a similar solution of the two-dimensional one with a slight deviation of the grinding temperature calculation result. It is established that the proposed simplified mathematical expression for determining the grinding temperature differs from the more accurate one-dimensional analytical solution by no more than 11 % and 15 % at the stages of heating and cooling, respectively. Comparison of the data on the grinding temperature change according to the conventional and developed equations has shown that these equations are close and have two points of coincidence: on the surface and at the depth of approximately threefold decrease in temperature. It is also established that the nature of the ratio between the scales of change of the Peclet number 0.09 and 9 and the grinding temperature depth 1 and 10 is of 100 to 10. Additionally, another unusual mechanism is revealed for both compared equations: a higher temperature at the surface is accompanied by a lower temperature at the depth. Keywords: grinding temperature, heating stage, cooling stage, dimensionless temperature, temperature model.

scholarly journals Outdoor personal heating and cooling by a Janus textile

2020 ◽  
Author(s):  
Hao Luo ◽  
Yining Zhu ◽  
Qiang Li ◽  
Ziquan Xu ◽  
Yu Hong ◽  
...  
Keyword(s):  
Thermal Management ◽  
Electricity Generation ◽  
Outer Space ◽  
Outdoor Environment ◽  
Conventional Heating ◽  
Radiative Loss ◽  
Cooling Mode ◽  
Heating And Cooling ◽  
Outdoor Spaces ◽  
Localized Heating

Abstract Enhancing the personal thermal comfort in outdoor environment is of substantial significance to ameliorate the health conditions of pedestrian and outdoor laborer. However, the uncontrollable sunlight, substantial radiative loss, and intense temperature change in the outdoor environment present majestic challenges to outdoor personal thermal management. To date, a wearable device with optional passive heating and cooling abilities to abet people combat extreme temperatures in outdoor spaces, is lacking. Here, we report an eco-friendly passive textile which converts the challenges into opportunities and harvests energy from the sun and the outer space for optional localized heating and cooling. Compared to conventional heating/cooling textiles like black/white cotton, its heating/cooling mode enables a skin simulator temperature increase/decrease of 11.3 ℃/14.5 ℃ respectively under sunlight exposure. Meanwhile, the temperature gradient created between the textile and skin simulator allows a continuous electricity generation with thermoelectric modules. Owing to the exceptional outdoor thermoregulation ability, this Janus textile is promising to help maintain a comfortable microclimate for individuals in outdoor environment and provide a platform for pervasive power generation.

scholarly journals Computer Application for Simulation of Temperature Distribution Inside the Room

2018 ◽  
Vol 210 ◽  
pp. 04036
Author(s):  
Hana Charvátová ◽  
Martin Zálešák
Keyword(s):  
Spatial Distribution ◽  
User Interface ◽  
Temperature Distribution ◽  
Heat Input ◽  
Computer Application ◽  
Comsol Multiphysics ◽  
Heat Sources ◽  
Cyclic Heating ◽  
Heating And Cooling ◽  
Computer Testing

The paper deals with computer testing of the temperature distribution in buildings by using COMSOL Multiphysics software. It is devoted to a description of a computer application created in the Application Builder user interface for simulation of the temperature distribution in a room heated by two heat sources. The application allows you to change geometric dimensions of all elements of the studied model and their spatial distribution, as well as a choice of physical properties needed to access the distribution of temperature in the room depending on the ambient temperature and the heat input of the considered sources. Main functions of the application are presented by simulation of cyclic heating and cooling of the tested room.

Sign in / Sign up

Export Citation Format

Share Document