Heat Penetration Depth Research Articles

Basic theorems and wave propagation in a piezothermoelastic medium with dual phase lag

The basic governing equations for an anisotropic piezothermoelastic solid with dual phase lag are presented and used to study the problem. Some basic theorems like variational principle, uniqueness theorem and theorem of reciprocity are established for the assumed model. Also, we characterize an alternative formulation of the mixed initial boundary value problem. These theorems are also summarized for a special case of orthotropic piezothermoelastic solid with dual phase lag. We formulated the plane wave propagation in an orthotropic piezothermoelastic solid with dual-phase-lag model. The non-trivial solution of the system is insured by a quartic equation whose roots represent the complex velocities of four attenuating waves in the medium. Various characteristics of the waves like phase velocity, attenuation quality factor, specific heat loss and penetration depth are computed numerically and shown graphically for three different models with the direction of propagation in three-dimensional space. Some special cases are also deduced from the present investigation.

Influence of the quasiparticle spectral weight in FeSe on spectroscopic, magnetic, and thermodynamic properties

We report on an extensive experimental and numerical study of the low-energy electronic properties of superconducting FeSe single crystals, using point-contact Andreev reflection Spectroscopy (PCAR), specific heat, and London penetration depth measurements. Taking explicitly into account Fermi surface anisotropy and recently suggested orbital-selective quasiparticle spectral weights ${Z}_{i}$ ($i={d}_{xy},{d}_{{x}^{2}\ensuremath{-}{y}^{2}},{d}_{xz},{d}_{yz},{d}_{{z}^{2}}$), our calculations quantitatively account for all our measurements as well as data from the literature, assuming that ${Z}_{yz}g{Z}_{xz}g{Z}_{xy}$. This study confirms the picture of a highly different quantum coherence of the Fe orbitals at the Fermi energy. In particular, the normal state properties (Sommerfeld coefficient and zero-temperature London penetration depth) strongly depend on the ${Z}_{i}$ values, which seem to be significantly sensitive to disorder.

Determination residual strength concrete of post-fire using ultrasonic pulse velocity

Assessment of residual strength of concrete post fire is importance. Concrete exposed at high temperatures causes chemical and physical phenomena that cause various level of damage. Heat distribution unevenly causes different of hot spots on the concrete surface. The correlation between high temperature and duration heat raises the heat penetration depth differently which effect on the strength of concrete. The research aims determine substantial reduction of the compressive strength concrete the post-fire as result of the depth of heat penetration. Experimental method by vertical furnaces was used in this research. Specimens use two of the concrete panel which has 1065 mm x 1055 mm and 100 mm thickness and ten the cylinder concrete with the diameter 150 mm and 300 mm height. Combustion of the specimens was performed with gradual heat follow the heat curve according to SNI 1741: 2008. The combustion duration carried out for 2 hours and an hour that result the depth heat penetration differently. The depth heat penetration was measured with a set thermocouple that has embedded in the concrete panels with various depths. The residual concrete strength post-fire was measured using ultrasonic pulse velocity.

Monte Carlo prediction of ballistic effect on phonon transport in silicon in the presence of small localized heat source

Understanding phonon transport at nanoscale is critically important for thermal nanometrology applications including scanning thermal microscopy, three-omega and time domain thermoreflectance experiments. In this paper, a multidimensional non-gray Monte Carlo simulation is developed to investigate the ballistic phonon transport in a silicon sample heated on the top by a small localized heater line. We observed that heat confinement occurs for very small heat sources. This result contradicts the classical Fourier model, according to which the heat penetration depth is always significant, even with small sources. The temperature fields inside the sample exhibit different penetration depths depending strongly on the heater line size. Maximum thermal resistance and a large interface temperature jump take place in the limit of very small heater width compared to the phonon mean free path due to the nonequilibrium and ballistic nature of phonon transport. Increasing the heater width leads to a decrease in the heat flux and temperature jump. In the limit of a very large heat source, the heat flux and temperature jump become independent of heat source size. In accordance with experimental investigations for the case of sapphire material (Siemens et al 2010 Nature Mat. 9 26–30), the thermal resistance of the silicon sample due to the localized heat source decreases and then tends to reach a plateau with increasing source size from tens of nanometers to micrometers. These results are important, not only for understanding the thermal transport in the sample during nanometrology experiments, but also for the design and manipulation of heat at nanoscale.

Investigations on the microstructure and mechanical properties of laser welded dissimilar galvanized steel–aluminum joints

In this study, galvanized high-strength steel and aluminum alloy sheets were laser-welded in zero-gap lap joint configuration. In order to determine the influences of the heat input levels, microstructural and mechanical properties of the joints were investigated. The weld bead geometry, microstructure, and intermetallic phases at the interface of welded joints were investigated using an optical microscope and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) at different heat input levels. Mechanical properties and microhardness distribution of the welded joints were examined according to the weld bead dimension. The results revealed that there is a correlation between the weld seam geometry and intermetallic phase formation. At relatively high heat input level, the penetration depth increased, and thick Al-rich intermetallic layer was observed at the interface of the weld seam, which deteriorated the tensile strength of the joint. It has been found that without the need for any additional precaution, the thickness of the IMC layer can be limited to 5–15 μm when the optimum welding parameters were conducted. The experimental results showed that with limited heat input and penetration depths, up to 108.7-N/mm tensile strength could be achieved and fracture initiated at the weld seam–steel interface.

Amplification and regulation of periodic nanostructures in multipulse ultrashort laser-induced surface evolution by electromagnetic-hydrodynamic simulations

The formation of periodic structures in ultrafast laser-irradiated surfaces implies dynamic coupling between the incoming light and the light-driven material. To capture the mutual influence and feedback between light and evolving surface topographies, we investigate numerically the evolution of metal surfaces irradiated by multiple femtosecond laser pulses of sub-, near-, and slightly above-threshold ablation fluence. The multiphysical model combines Maxwell equations and thermohydrodynamic approach based on electron-ion heat transfer and compressible Navier-Stokes equations and allows us to account for interpulse feedback on the resulting surface topographies. First pulses of the subthreshold energy lead to material swelling, nanocavitation few tens of nanometers below the surface, and, as a result, nanoroughness formation on the initially flat surface. Further pulses contribute to the development of periodic surface structures, enhanced absorption, and increased removal rate. Cavitation in the tips of ripples is found to play a crucial role in modification and regulation of surface topography for sub- and near-threshold ablation fluences. At higher laser pulse energy, thermal ablation is mostly involved in surface modification, and the ablation rate per power reaches its maximum at three to five times the ablation threshold fluence, resulting from the optimal heat penetration depth for laser ablation. The numerical results offer a better understanding of the surface topography modifications upon multipulse femtosecond laser irradiation.

Dielectric properties, effect of geometry, and quality changes of whole, nonfat milk powder and their mixtures associated with radio frequency heating

Radio frequency (RF) heating is a promising pasteurization technique providing a fast and more uniform heat generation throughout a sample. In this paper, the effect of composition, frequency (1–30 MHz) and temperature (20–90 °C) on the dielectric properties of whole, nonfat milk powder and their mixtures were studied to develop an effective RF pasteurization. Moreover, the effect of the shape and dimension of the container on RF heating were evaluated. Milk powders were loaded into rectangular and cylindrical boxes with the same volume and different heights (3, 6 and 9 cm), and heated in a 6 kW, 27.12 MHz pilot scale free-running oscillator RF oven. The heating rate, temperature profile, penetration depth, and electric field strength were determined. The quality of the RF heated milk powders was evaluated by measuring moisture content, water activity, solubility, and color. Overall, heating milk powder in the 6 cm height cylindrical box showed a relatively more uniform temperature distribution than 6 cm height rectangular box, with moderate heating rate as well as improved quality in the finished product with less changes in moisture content, water activity, solubility and color. Electric field strength increased with the increase in the height of the container.

Measuring the dielectric properties of date palm fruit, date palm leaflet, and Dubas bug at radio and microwave frequency using two-port coaxial transmission/reflection line technique

This paper presents a simple, innovative and effective procedure for measuring the dielectric properties of materials over a frequency range, based on the coaxial transmission/reflection method. The technique can measure the dielectric properties of materials from low to high loss with different sample sizes at different temperatures over a wide frequency range. The designed setup is tested and verified using air and polyamide samples, and simulated with 3D-electromagnetic software. Newer physical methods including dielectric heating have been considered, but information on the dielectric properties of date fruit, leaflet and Dubas bug, which causes great damage by reducing the quality and quantity of the date palm fruits in several countries, are lacking. The dielectric properties of date fruit, leaflet, and Dubas bug are measured at five temperatures between 20 and 60 °C and over the frequency range from 14 to 915 MHz. The experimental and simulation results show good statistical agreement. The designed setup is very useful for materials with low to high loss factor and for small objects like insects at different temperatures. The results show that the dielectric properties of the tested materials decrease with frequency and increase with temperature. Comparison of the dielectric loss factor of insects, date fruit, and leaflet shows that the insect differentially heats up faster than the date fruit and leaflet. The penetration depth decreases with increasing frequency and temperature. The results show that the dielectric heating at radio frequency might provide practical applications in controlling insects because of the differential heating and sufficient penetration depth.

Selective laser broiling of Atlantic salmon

Selective laser broiling is a novel food processing technique that utilizes a 2-axis mirror galvanometer system to direct laser power to cook raw food. Unlike conventional cooking processes, laser cooking benefits from the high spatial and temporal precision of power delivery. In this investigation, we use a trochoidal scanning pattern to optimize the cooking of Atlantic salmon (Salmo salar), which is used as a model food system. We vary geometry of the trochoidal cooking pattern (circle diameter, circle density, and period) as well as the heat flux (2.71 MW/m2 and 0.73 MW/m2) and power (2 W and 5 W) of the blue laser and measure the internal temperature and depth of heat penetration via color analysis. Heat generated by blue laser operating at 445 nm has a thermal penetration depth nearing 2 mm in salmon and provide sufficient protein denaturation for cooking thin food layers. We achieve food safe cooking temperatures (>62.8 °C) in the salmon fillets and desirable color and textural changes through the use of high speeds and repetitive exposure. Ultimately, the goal of this study is to explore laser cooking of meat with an eye to applications both in food printing as well as an augmentation of conventional oven cooking.

Finite Element Analysis of the 3ω Method for Characterising High Thermal Conductivity Ultra-Thin Film/Substrate System

The 3ω method is an attractive technique for measuring the thermal conductivity of materials; but it cannot characterise high thermal conductivity ultra-thin film/substrate systems because of the deep heat penetration depth. Recently, a modified 3ω method with a nano-strip was specifically developed for high thermal conductivity thin film systems. This paper aims to evaluate the applicability of this method with the aid of the finite element analysis. To this end, a numerical platform of the modified 3ω method was established and applied to a bulk silicon and an AlN thin-film/Si substrate system. The numerical results were compared with the predictions of theoretical models used in the 3ω method. The study thus concluded that the modified 3ω method is suitable for characterising high thermal conductivity ultra-thin film/substrate systems.

Evaluation of temperature profiling quality in determining energy efficiencies of borehole heat exchangers

By profiling the natural temperature of borehole heat exchangers it is possible to determine the thermal conductivity λ of the ground using Fourier’s law. However, analyses of borehole temperature profiles lead to the conclusion that the profiles differ from the theoretical data. The causes are many, including urban infrastructure leading to ground temperature profiles being heavily distorted. Among factors impacting ground temperature profiles are: buildings, roads, heat pipelines, water pipelines, and sewers. Ground temperature profiles influenced by urban infrastructure are not valid for determining ground thermal conductivity. The aim of the work is to analyze factors influencing temperature logging changes in borehole heat exchangers and their suitability for determining ground thermal conductivity. Based on the temperature logging, the depth of periodic heat penetration is assessed and is compared with the value determined on the basis of the map. It is found that the natural temperature profiles in borehole heat exchangers are only partially suitable for the analysis of the thermal conductivity of rocks.

Homogeneous equivalent model coupled with P1-approximation for dense wire meshes volumetric air receivers

A three dimensional homogeneous equivalent model to analyze the thermal behavior of open volumetric receivers made of staggered stack plain-weave wire meshes is presented. The main boundary conditions, optical and geometrical parameters, assumptions and methodology are described. Then, the model is compared with available literature data in a 3D simulation accounting for the inhomogeneous concentrated solar flux profile of the experiments. A parametric study is conducted to study the thermal behavior of different absorbers submitted to a homogeneous concentrated solar flux and to analyze the influence of the heat transfer coefficient and penetration depth.

Spontaneous Thermal Hall Effect in Three-dimensional Chiral Superconductors with Gap Nodes

Generic chiral superconductors with three-dimensional electronic structure have nodal gaps and are not strictly topological. Nevertheless, they exhibit a spontaneous thermal Hall effect (THE), i.e. a transverse temperature gradient in response to a heat current even in the absence of an external magnetic field. While in some cases this THE can be quantized analogous to the Quantum Hall effect, this is not the case for nodal superconductors in general. In this study we determine the spontaneous THE for tight binding models with tetragonal and hexagonal crystal symmetry with chiral $p$- and d-wave superconducting phase. At the zero-temperature limit, the thermal Hall conductivity $ \kappa_{xy} $ provides information on the structure of the gap function on the Fermi surface and the Andreev bound states on the surface. The temperature dependence at very low temperatures is determined by the types of gap nodes, point or line nodes, leading to characteristic power law behaviors in the temperature, as known for other quantities such as specific heat or London penetration depth. The generic behavior is discussed on simple models analytically, while the analysis of the tight-binding models is given numerically.

Study of residual thermal stresses in hard-alloy coatings obtained by electropulse technology

Qualitative and quantitative estimates of the temperature fields and level of the residual thermal stresses (RTS) in a steel substrate and hard-alloy coating obtained by electropulse technology (EPT) are presented. The estimation was carried out using the finite element method (FEM) and universal COMSOL Multiphysics® software to simulate applied problems. The results of the simulation showed that the higher the rate of mechanical loading, the smaller the depth of heat penetration into the substrate, the residual thermal stresses being localized in the zone of thermal influence near the interaction surface. At the same time, a thin layer of steel cannot cause considerable stresses in the bulk of the hard alloy. The stresses in the steel layer reach the yield point and the layer deforms without formation of large tensile stresses in the hard alloy. A criterion has been obtained that makes it possible to reveal the range of coating application parameters in which the impact of the steel substrate on the formation of residual thermal macro-stresses in the bulk of the hard-alloy coating is minimum. Electropulse equipment has been developed for application of the hard alloy coatings. Standard x-ray sin2Ψ-method (rotation method) is used for experimental evaluation of the macrostresses in the zone of the steel contact with the coating. Studies have shown that both radial and axial stresses are compressive; the maximum absolute values of the stress are observed in the radial direction in the outer layers of the coating, while the axial stresses relax near the free surface. Radial stresses in the outer layers of the coating reach a value of -210 MPa, and axial -110 MPa. The stresses in the coating layers contacting with steel are also characterized by rather high values, of the order of -160 ... -170 MPa. A high level of stress is attributed to the fact that the coating is formed under external pressure. At the same time the compressive stresses are favorable for a hard alloy, since it exhibits high values of the ultimate compression strength.

Thermal aspects in machining CFRPs: effect of cutter type and cutting parameters

The problem of heat generation and distribution in edge trimming of carbon fiber-reinforced polymers (CFRP) was investigated. The heat diffusion problem in the cutting zone was modeled numerically and an inverse head conduction technique was applied to determine the heat partition. Measurements of boundary temperatures allowed the determination of the proper magnitude of heat flux applied to the workpiece and the cutting tool. It was found that less than 16% of the total heat is conducted into the workpiece and that higher feed speeds allowed less heat to conduct into the workpiece. The depth of heat penetration into the workpiece caused the temperature to reach the glass transition temperature of the epoxy only for the slower feed speed. When tested at the same feed per revolution, a PCD 2-flute end mill was the most effective tool in removing the heat from the cutting zone as compared to burr tools.

Analytical and numerical approaches for Falkner–Skan flow of MHD Maxwell fluid using a non-Fourier heat flux model

PurposeThis paper aims to describe the laminar flow of Maxwell fluid past a non-isothermal rigid plate with a stream wise pressure gradient. Heat transfer mechanism is analyzed in the context of non-Fourier heat conduction featuring thermal relaxation effects.Design/methodology/approachFlow field is permeated to uniform transverse magnetic field. The governing transport equations are changed to globally similar ordinary differential equations, which are tackled analytically by homotopy analysis technique. Homotopy analysis method-Padè approach is used to accelerate the convergence of homotopy solutions. Also, numerical approximations are made by means of shooting method coupled with fifth-order Runge-Kutta method.FindingsThe solutions predict that fluid relaxation time has a tendency to suppress the hydrodynamic boundary layer. Also, heat penetration depth reduces for increasing values of thermal relaxation time. The general trend of wall temperature gradient appears to be similar in Fourier and Cattaneo–Christov models.Research limitations/implicationsAn important implication of current research is that the thermal relaxation time considerably alters the temperature and surface heat flux.Originality/valueCurrent problem even in case of Newtonian fluid has not been attempted previously.

Recent Progress in 808 nm Excited Upconversion Nanomaterials as Multifunctional Nanoprobes for Visualized Theranostics in Cancers.

Near-infrared (NIR) light responsive nanomaterials have attracted considerable attention due to their location in the biological window. Especially, lanthanide-doped nanomaterials exhibit unique upconversion luminescence (UCL) properties with low background interference and long luminescence lifetime, which makes them promising in imaging diagnosis of cancers. Compared with traditional upconversion nanomaterials excited by 980 nm laser, 808 nm excitation can overcome the disadvantages of high heating effect and weak penetration depth induced by excitation source. Therefore, developing 808 nm excited upconversion nanoprobes will be important for the in vivo bio-imaging and visualized theranostics of tumors in deep-tissue. In the review paper, we systematically summarized the synthesis strategy and luminescence modulation of Nd3+-sensitized upconversion nanomaterials under 808 nm excitation, discussed the influence of excitation source on heating effect and penetration depth, and particularly focused on their applications in UCL imaging, multi-modal imaging and imaging-guided therapy of cancers.

Correction: Buoyancy effects in stagnation-point flow of Maxwell fluid utilizing non-Fourier heat flux approach.

[This corrects the article DOI: 10.1371/journal.pone.0192685.].

Buoyancy effects in stagnation-point flow of Maxwell fluid utilizing non-Fourier heat flux approach.

Here we utilize a non-Fourier approach to model buoyancy aiding or opposing flow of Maxwell fluid in the region of stagnation-point towards a vertical stretchable surface. Flow field is permeated by uniform transverse magnetic field. Two different heating processes namely (i) prescribed surface temperature (PST) and (ii) constant wall temperature (CWT) are analyzed. Through suitable transformations, the similarity equations are formed which are treated numerically for a broad range of magnetic interaction parameter. The obtained solutions are compared with available articles under limiting situations and such comparisons appear convincing. The structure of boundary layer depends on a parameter measuring the ratio of free stream velocity to the stretching sheet velocity. The momentum transport via stretching boundary is opposed by both fluid relaxation time and magnetic interaction parameter. Thermal boundary layer expands as the effects of transverse magnetic field and thermal relaxation time are amplified. A reduction in heat penetration depth is anticipated for increasing values of thermal relaxation time. The variation in wall slope of temperature with increasing thermal relaxation time appears similar at any assigned value of Prandtl number. A comparative study of aiding and opposition flow situations is presented and deliberated.

Characterization of dough baked via blue laser

Depth of heat penetration and temperature must be precisely controlled to optimize nutritional value, appearance, and taste of food products. These objectives can be achieved with the use of a high-resolution blue diode laser—which operates at 445 nm—by adjusting the water content of the dough and the exposure pattern of the laser. Using our laser, we successfully cooked a 1 mm thick dough sample with a 5 mm diameter ring-shaped cooking pattern, 120 repetitions, 4000 mm min−1 speed, and 2 W laser power. Heat penetration in dough products with a blue laser is significantly higher compared to with an infrared laser. The use of a blue laser coupled with an infrared laser yields most optimal cooking conditions for food layered manufacture.