scholarly journals Model representations of heat shock in terms of dynamic thermal elasticity

2020 ◽  
Vol 8 (2) ◽  
pp. 85-108
Author(s):  
E. M. Kartashov
Keyword(s):  
Thermal Shock ◽  
Heating Time ◽  
Solid Boundary ◽  
Compatibility Equation ◽  
Spherical Coordinate ◽  
Heating And Cooling ◽  
Wave Nature ◽  
Radial Heat Flow ◽  
Special Cases ◽  
Radial Heat

This article is devoted to mathematical models of thermal shock in terms of dynamic thermoelasticity and their application to the specific conditions of intensive heating and cooling of solids. A scheme is proposed for deriving the compatibility equation in voltages for dynamic problems, which generalizes the well-known Beltrami-Mitchell relation for quasistatic cases. The proposed relation can be used to consider numerous special cases in the theory of thermal shock in Cartesian coordinates for both bounded canonical bodies and partially bounded ones. As a detailed study, the latter case was considered under conditions of abrupt temperature heating and cooling, thermal heating and cooling, and medium heating and cooling. Numerical experiments were carried out, and the wave nature of the propagation of thermoelastic waves was described. The effect of relaxation of the solid boundary on sudden heating and sudden cooling, which has been little studied in thermomechanics, is described. It is established that this effect influences maximum of internal temperature stresses, which depend on the parameters characterizing the elastic and thermal properties of materials, as well as the heating time and cooling time. A “compatibility equation” in displacements was proposed to study the problem of thermal shock in cylindrical and spherical coordinate systems in bodies with a radial heat flow and central symmetry. The formulation of a generalized problem in the theory of thermal shock is formulated, which is of practical and theoretical interests for many areas of science and technology.

Thermal Reaction During Thermal Shock of a Massive Body with an Internal Cylindrical Cavity

2020 ◽  
pp. 60-79
Author(s):  
E.M. Kartashov ◽  
E.V. Nenakhov
Keyword(s):  
Mathematical Models ◽  
Thermal Shock ◽  
Cylindrical Cavity ◽  
Thermal Stresses ◽  
Thermal Reaction ◽  
Inertial Effects ◽  
Compatibility Equation ◽  
Near Surface ◽  
Dynamic Thermoelasticity ◽  
Special Cases

The paper examines mathematical models of thermal shock in terms of dynamic thermoelasticity and their application to specific cases during intense heating of a solid boundary. We introduce a stress compatibility equation for dynamical problems, generalizing the well-known Beltrami --- Mitchell relation for quasi-static cases. It is convenient to use this relation when considering numerous special cases in the theory of heat shock in Cartesian coordinates both for bounded bodies of a canonical form, i.e., an infinite plate, and for partially bounded bodies, i.e., space bounded from the inside by a flat surface. In the latter case, the obtained analytical solutions of dynamic problems of thermoelasticity lead to visual and convenient for physical analysis functional structures describing the kinetics of thermal stresses. For cylindrical and spherical coordinate systems, we propose a compatibility equation in displacements, which is convenient for studying the problem of thermal shock in bodies with a radial heat flux and under conditions of central symmetry. In the study, we singled out a class of problems in which the consideration of the geometric dimensions of a structure investigated for a thermomechanical reaction under conditions of intense heating concerns mainly the near-surface layers. According to the experimental results, it is these layers that absorb the main amount of heat during a time close to the beginning of heating, which corresponds to the time of the microsecond duration of the inertial effects. We investigated the thermal reaction of a massive body with an inner cylindrical cavity within the framework of dynamic thermoelasticity under various modes of intense heating of the cavity surface. Finally, we carried out numerical experiments and described the wave character of thermal stresses with the corresponding quasi-static values, and established the role of inertial effects in mathematical models of the theory of thermal shock

Dissociation and Subsidence of Hydrated Sediment: Coupled Models

2009 ◽  
Vol 27 (2) ◽  
pp. 105-131 ◽  
Author(s):  
Mohamed Iqbal Pallipurath
Keyword(s):  
Thermal Dissociation ◽  
Hydrate Formation ◽  
Coupled Models ◽  
Two Phase ◽  
Strength Deterioration ◽  
Intrinsic Kinetics ◽  
Radial Heat Flow ◽  
Radial Heat ◽  
Definition Of ◽  
Pressure Changes

Thermal dissociation of hydrated sediment by a pumped hot fluid is modeled. A radial heat flow from the hot pipe is assumed. The coordinate system is cylindrical. Three components (hydrate, methane and water) and three phases (hydrate, gas, and aqueous-phase) are considered in the simulator. The intrinsic kinetics of hydrate formation or dissociation is considered using the Kim-Bishnoi model. Mass transport, including two-phase flow, molecular diffusions and heat transfer involved in formation or dissociation of hydrates are included in the governing equations, which are discretized with finite volume difference method and are solved in an explicit manner. The strength deterioration of the hydrate bed as a result of dissociation is investigated with a geo-mechanical model. The way in which dissociation affects the bed strength is determined by plugging in the porosity and saturation change as a result of dissociation into the sediment collapse equations. A mechanism to measure the pore pressure changes occurring due to dissociation is developed. The rate of collapse as dissociation proceeds is determined and the model thus enables the definition of a safety envelope for gas hydrate drilling.

scholarly journals The effect of metal wool on the charging and discharging rate of the phase transition thermal storage material

2021 ◽  
Vol 4 (5(112)) ◽  
pp. 12-20
Author(s):  
Olga Khliyeva ◽  
Vitaly Zhelezny ◽  
Aleksey Paskal ◽  
Yana Hlek ◽  
Dmytro Ivchenko
Keyword(s):  
Power Systems ◽  
Phase Change ◽  
Phase Change Materials ◽  
Thermal Storage ◽  
Heating Time ◽  
Phase Changes ◽  
Storage Material ◽  
Heat Accumulation ◽  
Heating And Cooling ◽  
Efficiency And Reliability

Thermal energy storage (TES) plays an important role in solar heat power systems. The use of phase change materials (PCM) and selecting additives to increase the rate of heat accumulation is a promising way to increase the efficiency and reliability of such systems. The objects of the study were pure paraffin wax (PW) and composite PCMs based on it (containing aluminum and copper wool of 30 and 45 μm in diameter, respectively). An experimental setup with a cylindrical measuring cell was created, which was also considered as a model of a capsule with a thermal storage material. The rate of temperature change in the pure PW sample and samples of composite PCMs was experimentally measured. Two modes of heating and cooling were investigated: from 48 to 59 °C (mode with a phase change) and from 30 to 40 °C (mode without phase changes). Heating time from 48 to 59 °C for the PW sample was 13 min., for the PW samples with the content of aluminum wool of 0.00588 and 0.01780 m3·m-3 − 11 and 10.5 min., for the PW samples with the content of copper wool of 0.00524 and 0.01380 m3·m-3 − 11 and 8 min., correspondingly. The minimum heating time from 30 to 40 °C was 6 min. for the sample of PW with 0.01380 m3·m-3 of copper wool in comparison with 9 min. for the sample of pure PW. The expediency of using copper wool as an additive to thermal storage materials of PW to increase the charging and discharging rate of TES devices without significantly raising their price was confirmed. The presence of metal wool in molten PW suppresses bottom-up convective currents, so the main mechanism of heat transfer is thermal conductivity. This fact will contribute to a faster equalization of the temperature field by the height of heat storage capsules

Thermal Shock Resistance of Plasma Sprayed Multi-Layered Functionally Graded Cr3C2-NiCr Coatings

2016 ◽  
Vol 852 ◽  
pp. 1000-1005 ◽  
Author(s):  
Dong Xing Fu ◽  
Jing Na Liu ◽  
Er Bao Liu ◽  
Zhao Bin Cai ◽  
Xiu Fang Cui ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Functionally Graded ◽  
X Ray Diffraction ◽  
Coating Materials ◽  
Heating And Cooling ◽  
Structure Of Coatings ◽  
Functionally Graded Coatings ◽  
Shock Resistance ◽  
Plasma Sprayed

The interface properties of multi-layered functionally graded Cr3C2-NiCr coatings deposited by plasma spraying technique were experimentally studied in this paper. The microstructure and phase structure of coatings were studied with scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The thermal shock resistance was investigated by cyclic heating and cooling tests using an electro-calefaction furnace. The crack appearances of the coatings were observed carefully. Results show that the plasma sprayed multi-layered functionally graded coatings are compact and the adhesion between the layers and the substrate is good. The coatings have better macro-hardness than the substrate, and the 6-layers coating has the highest macro-hardness and the best wear resistance. Besides, the micro-hardness of coatings increases with increasing content of Cr2C3 in coating materials. Results of cyclic thermal shock show that the main failure styles of the coatings are crack and desquamation and the thermal shock resistance of the coatings is improved obviously by increasing the number of coating layers.

Measurement of effective thermal conductivity of lithium metatitanate pebble beds by steady-state radial heat flow method

2021 ◽  
Vol 172 ◽  
pp. 112854
Author(s):  
Maulik Panchal ◽  
Vrushabh Lambade ◽  
Vimal Kanpariya ◽  
Harsh Patel ◽  
Paritosh Chaudhuri
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Heat Flow ◽  
Effective Thermal Conductivity ◽  
Flow Method ◽  
Radial Heat Flow ◽  
Radial Heat

Thermal Conductivity of Uranium Dioxide from -57o to 1100oC by a Radial Heat Flow Technique

1965 ◽  
Vol 48 (6) ◽  
pp. 297-305 ◽  
Author(s):  
T. G. GODFREY ◽  
W. FULKERSON ◽  
T. G. KOLLIE ◽  
J. P. MOORE ◽  
D. L. McELROY
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Uranium Dioxide ◽  
Radial Heat Flow ◽  
Radial Heat

A radial heat-flow apparatus for liquid thermal conductivity determinations

1958 ◽  
Vol 245 (1241) ◽  
pp. 259-267 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Temperature Drop ◽  
Measured Quantity ◽  
Concentric Cylinders ◽  
Radial Heat Flow ◽  
Radial Heat ◽  
Flow Apparatus ◽  
Liquid Thermal Conductivity ◽  
Quantity Of Heat

A radial heat-flow apparatus has been constructed in Pyrex glass and used for liquid thermal conductivity investigations. The liquid under test fills the 1.25mm space between concentric cylinders and a measured quantity of heat flows inwards. After calibration using liquids of known thermal conductivity, new values are obtained for pyridine and three chlorofluoro­carbon oils. The apparatus can also be used for direct determinations when allowance is made for the temperature drop occurring in each of the glass walls. For this purpose, a determination of the thermal conductivity of the glass was made using a similar method. A discussion of the results is included.

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