Temperature Distribution In Layers Research Articles

Mathematical model to analyse the skin layers temperature with cloth during and after exercise

The human body is a complex system that can be disrupted by various types of infections and viruses, and body temperature is a major contributor to these problems. To prevent this, doctors recommend comfortable clothing made from good fabric. This paper proposes a model that can be used to analyze how different types of fabric impact the thermal profile of skin layers during and after physical activity. The information gained from this model could be useful in designing exercise apparel for different climates and in generating thermal stress protocols for treating infections and providing physical activity guidelines for healthy living. The model uses Pennes’ bio-heat equation and finite difference method to examine the temperature distribution in skin layers while accounting for both physiological and clothing parameters. The numerical findings were compared to existing studies, and the model’s accuracy was found to be in good agreement with previous research. The proposed model can be used to predict how much rest and acclimation are needed to cope with thermal stress and could also be modified to obtain thermal information for patients with skin diseases. Additionally, the thermal profile obtained from this model could be helpful in designing exercise clothes for patients with skin diseases.

High spatial resolution fluid thermometry in boundary layers by macroscopic imaging of individual phosphor tracer particles

We introduce a measurement concept using seeded thermographic phosphor particles, which achieves high spatial resolution and rejection of surface induced signals, and is thereby applicable to resolve two-dimensional temperature distribution in sub-millimeter thermal boundary layers. Unlike previous implementations of ratiometric phosphor thermometry in fluid flows, which is based on the division of two spectrally or temporally separated images of the luminescence from groups of seeded particles, here we treat the individual phosphor particles as independent temperature detectors positioned at the discrete particle locations. 2D rotated Gaussian functions are fitted to each particle image as to integrate particle signals in the two frames for ratio-based thermometry and to position the particles with sub-pixel resolution (<10μm). In addition, the fitting method allows to separate the luminescence signal of the imaged particles from interfering signals with a low spatial frequency, for example from surface reflection or re-scattering of luminescence light. After assessing the spatial resolution, and the robustness of the temperature measurements against high levels of re-scattered signals, near-wall measurements are demonstrated. The ability to finely resolve the temperature distribution within a 500μm thin thermal boundary layer is validated against the laminar Prandtl–Blasius equation. As the thermometry counterpart and complement to Particle Tracking Velocimetry, this technique allows to probe the fine details of heat transfer in boundary layers.

Influence of Thermal Coupling on Lifetime Under Power Cycling Test

In this article, the influence of thermal coupling in power modules on lifetime under power cycling test (PCT) is investigated. In a full-bridge power module for electric vehicle application, the thermal coupling is strong due to high power density and causes lateral temperature difference. In PCT, at the same maximum junction temperature <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vjmax</sub> and temperature swing Δ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vj</sub> , the influence of thermal coupling on lifetime and failure mode is investigated. The root cause of why thermal coupling influences lifetime and the failure mode is discussed by finite-element analysis. Transient thermal impedance is used to calibrate the simulation model. The Influence of thermal coupling on chip surface and solder layer temperature distribution is analyzed under the same test conditions. Furthermore, two parameters are extracted from the temperature distribution of chip surface as flags of failure mode determination. Finally, taking thermal coupling into account, combined with direct copper bonding structure, an improved layout is recommended in terms of lifetime.

Thermal Layer Design in Fused Filament Fabrication

The current limitations of design for additive manufacturing (DfAM) are the state of knowledge on materials and the effects of production parameters. As more engineering-grade polymers become available for fused filament fabrication (FFF), the designs and processes must be adapted to fully utilize the structural properties of such materials. By studying and comparing the production parameters of a material test specimen and a component, the effects of layer temperature on the strength, surface roughness, and dimensional accuracy of PA6-CF were found. As the cross-section increases in component manufacturing, maintaining the layer temperature becomes a major challenge. From the findings, the concept of thermal layer design (TLD) was introduced as a way of increasing strength via temperature in selected regions after presenting the effect of layer temperature. TLD proved to have a major effect on layer temperature and heat distribution. Depending on the investigated layer temperature, from 147 °C to 193 °C the UTS of PA6-CF increased from 42 MPa to 73 MPa. Implementing TLD in DfAM represents a big leap for designing high-performance polymer components.

Studi Distribusi Temperatur Pada Kulit Manusia yang mengalami Cryotherapy dengan Finite Difference Method (FDM)

Biological heat transfer studies the transfer of heat in biological systems from inside the human body or from outside to inside the body. The biological heat transfer equation uses the Pennes equation, which applies to the layers of skin made up of the epidermis, dermis, fat, and muscle. This investigation solves the biological heat transfer equation to obtain a one-dimensional unstable temperature distribution in human skin layers subjected to cryotherapy with cold packs at temperatures of 278 K and 283 K using the finite difference method (FDM). The results show that cold compresses influence the temperature distribution on human skin due to the very significant temperature difference between the heat sink temperature and the core temperature of the human body. The greater the temperature difference, the more significantly the temperature distribution in human skin decreases. This is due to the heat transfer that occurs due to two temperature differences, namely the core temperature of the body and the temperature of the cold substance, and is also favored by differences in thermal conductivity, density, and specific heat. that exist in every layer of the skin.

Direct Phase-Change Cooling of Vapor Chamber Integrated With IGBT Power Electronic Module for Automotive Application

In electric vehicles and hybrid electric vehicles, insulated-gate bipolar transistor (IGBT) power module trends to dissipate higher heat flux due to increased power rating and reduced package size. An inefficient cooling method will result in stringent thermal reliability problems. Therefore, there is a strong need for innovative and efficient cooling technologies in order to tackle these issues. In this article, a localized direct phase-change cooling strategy is applied and integrated with direct bonded copper in IGBT power module. Vapor chamber with light weight, high thermal conductivity, and even temperature uniformity replaces original copper baseplate. Layers of thermal grease and original cooling plate are removed, leading to a further reduction in thermal resistance. In order to evaluate the new module, a thermal model and an experiment were built to analyze temperature distribution in layers, junction temperature, temperature uniformity, and thermal resistance. Results indicate the integrated thermal management system outperforms traditional cooling solutions on the cooling capacity. Improvements on junction temperature, temperature uniformity, and total thermal resistance are 34.6%, 76.6%, and 41.6%, respectively. The results illustrate the potential of phase-change cooling by vapor chamber. It provides a new perspective in the compact and efficient design of power electric modules.

Investigation of Liquid Water Distribution under Temperature Gradient in PEFC Using in-situ X-ray Visualization

Polymer electrolyte fuel cells (PEFCs) are one of promising electric generating devices. It is necessary to understand the relationships between the water distribution and the temperature distribution in gas diffusion layers (GDLs) to improve the performance at high current density. To reveal the effects of cell temperature on liquid water accumulation inside PEFCs, in-situ X-ray measurement and numerical simulation were performed at 40, 60, 70, and 80°C. The measurement was carried out using a fuel cell having a serpentine-type flow field, ribs and flow channels of 300 μm width, and 1.5×3.0mm2 active area. Current density was kept 1.5 A/cm2 for 300 secs in all cases. Both the experimental results and the numerical results showed that the liquid water distribution in GDLs strongly depends on cell temperature. In the case of lower temperature, liquid water accumulated in a region near CL and MPL. While in the case of higher temperature, liquid water accumulated in a region near rib. In addition, the experimental results indicated that the vapor crossover depended on existence of liquid water in MPL, and it was shown that the amount of vapor crossover increased at lower temperature condition.

THE MAPPING OF SUBSURFACE TEMPERATURE AND STUDY OF GEOTHERMAL GRADIENT ANOMALY IN THE DISCHARGE AREA IN NORTH SULAWESI

The aim of this research is to measure and mapping the temperature distribution in several subsurface layers in the manifestation of geothermal warm ground and steaming ground, and analyze the geothermal subsurface gradient, to determine the heat source zone, and the pattern and direction of heat flow from subsurface to surface in Hydrothermal area of Minahasa Indonesia. The method used is direct measurement in the field. To determine the coordinates of geothermal manifestations and location mapping, using remote sensing techniques. The results showed that at a depth of 200 cm the temperature reaches 102 0C and the heat source comes from the northeast and from the south. At a depth of 150 cm the temperature varies from 52 to 100 0C with an even distribution in almost every direction. At a depth of 50 to 100 cm the maximum temperature reaches 98 0C with heat propagation starting to concentrate then northeast, and then out to the surface in the northeast. The pattern of heat transmission is almost linear along with the geothermal gradient.

GEOTHERMAL GRADIENT AND SUBSURFACE TEMPERATURE FOR ESTIMATION OF SOURCES, PATTERNS AND HEAT FLOW DIRECTIONS IN THE HYDROTHERMAL AREA OF MINAHASA INDONESIA

Geothermal gradient anomaly studies and subsurface temperature mapping play an important role in the estimation of heat flow sources and patterns, and also make a fundamental contribution in the field of geothermal physics, especially methods for geothermal energy exploration. The purpose of this study is to measure and mapping the temperature distribution in several subsurface layers in the manifestation of geothermal warm ground and steaming ground, and analyze the geothermal subsurface gradient, to determine the heat source zone, and the pattern and direction of heat flow from subsurface to surface in Hydrothermal area of Minahasa Indonesia. The method used is direct measurement in the field. To determine the coordinates of geothermal manifestations and location mapping, using remote sensing techniques. The results showed that the temperature gradient under the manifestation of geothermal energy increased with increasing depth. The pattern of heat flow in the warm ground manifestation is perpendicular from shallow depths to the surface, while the heat flow pattern under the steaming ground manifestation tends to spread towards the North-East.

Performance evaluation of concentrator photovoltaic systems integrated with a new jet impingement-microchannel heat sink and heat spreader

Thermal regulation of concentrator photovoltaic (CPV) systems is of great importance to keep silicon layer temperature within the maximum allowable temperature range, as it enhances overall performance and avoids potential solar cells damage. Therefore, a novel jet impingement mini- and- micro channel heat sink with a heat spreader integrated with a CPV system is designed. To evaluate the performance of the developed system, a three-dimensional conjugate thermo-fluid model for the solar cell layers, jet impingement with microchannel flow, and heat spreader is established. This model is numerically solved, and results are validated using the available measurements. The new system is then compared using several heat sink designs including a jet impingement-mini-channel with and without a heat spreader at different concentration ratios (CR) and coolant Reynolds numbers (Re). The findings indicate that at CR = 20, integrating a jet impingement-micro-channel heat sink, and a heat spreader with the CPV system accomplishes a uniform silicon layer temperature distribution with the lowest average temperature compared to other designs. In addition, the established design attains the highest net electrical power and electrical efficiency. The results of the current study demonstrate the effectiveness of combining active and passive cooling methods for thermal management of the CPV systems.

MEAN CLIMATIC PARAMETERS OF THE UPPER MIXED LAYER IN THE BERING SEA (LOWER BOUNDARY, TEMPERATURE, SALINITY) AND THEIR ANNUAL VARIABILITY

All available deep-water oceanographic data obtained in the Bering Sea in 1929–2019 are analyzed (101,425 oceanographic stations). Lower boundary of the upper mixed layer is determined from the vertical temperature profiles using the criterion of temperature deflection from SST (10 % for June-October and 0.2, 0.3, and 0.5 o С for November-May). The mixed layer is rather thin in June-September, its thickness is 10–20 m over the major part of the sea, and 30–40 m at the straits between central Aleutian Islands. In DecemberMarch, the mixed layer depth increases to 120–160 m in the northern deep-water sea and up to 180–200 m at the straits between central and eastern Aleutian Islands, though it is thinner in plumes of warm waters entering from the Pacific. At the continental shelf, the mixed layer can be traced to the depth of 20–40 m in the eastern Bering Sea and 60–80 m at Kamchatka in December-January and to 60–80 m in the eastern Bering Sea and 80–100 m at Kamchatka in February-March. The mixed layer temperature distribution is distinguished by two completely different seasonal patterns. The winter distribution pattern with the highest temperature in the areas adjacent to the Aleutian Straits is typical for November-June. The summer pattern with high temperature in the Karaginsky Bay, Bristol Bay, and Norton Sound and lower temperature near the Aleutian Straits is typical for July-October. On the contrary, the salinity distribution pattern is stable, with the highest salinity at the central and eastern Aleutian Straits and lower salinity in the coastal zone as the Anadyr Bay and Norton Sound influenced by the river runoff.

A study of heat transfer during cryosurgery of lung cancer.

In this study, a mathematical model describing two-dimensional bio-heat transfer during cryosurgery of lung cancer is developed. The lung tissue is cooled by a cryoprobe by imposing its surface at a constant temperature or a constant heat flux or a constant heat transfer coefficient. The freezing starts and the domain is distributed into three stages namely: unfrozen, mushy and frozen regions. In stage I where the only unfrozen region is formed, our problem is an initial-boundary value problem of the hyperbolic partial differential equation. In stage II where mushy and unfrozen regions are formed, our problem is a moving boundary value problem of parabolic partial differential equations and in stage III where frozen, mushy, and unfrozen regions are formed, our problem is a moving boundary value problem of parabolic partial differential equations. The solution consists of the three-step procedure: (i) transformation of problem in non-dimensional form, (ii) by using finite differences, the problem converted into ordinary matrix differential equation and moving boundary problem of ordinary matrix differential equations, (iii) applying Legendre wavelet Galerkin method the problem is transferred into the generalized system of Sylvester equations which are solved by applying Bartels-Stewart algorithm of generalized inverse. The complete analysis is presented in the non-dimensional form. The consequence of the imposition of boundary conditions on moving layer thickness and temperature distribution are studied in detail. The consequence of Stefan number, Kirchoff number and Biot number on moving layer thickness are also studied in specific.

Temperature and moisture distribution in a highway in south-eastern Kazakhstan

The matters of investigation for water thermal regime of pavement and subgrade structures of the highways are especially important as the moisture and temperature distribution in pavement and subgrade layers impact greatly on their deformation and strength indicators. Experimental results, which can be obtained by special measurement devices, are primary ones for establishing of peculiarities and regularities for distribution and migration of heat and moisture in the mentioned structural elements of the highways. Special measurement devices are required to obtain such experimental data. The paper shows the results for analysis of temperature and moisture variation in points of pavement and subgrade of “Almaty-Bishkek” highway. Temperature measurement has been performed by set of special sensors. Regular temperature and moisture measurement have been performed for the period from September 18, 2015 to June 2, 2016. Regularities for temperature regime variation in points of pavement for 24 hours are coordinated with air temperature variations. Amplitude of vibration for temperature is decreased with the depth increase. Moisture in subgrade points is gradually decreased with the reduction of daily average air temperature.

Selective electron beam surface alloying of aluminum with TiCN nanoparticles

In this work we present a mathematical model of the temperature distribution in layers formed by selective electron beam surface alloying of Al with TiCN nanoparticles following circular trajectories. The model is based on analytical solution of the heat transfer equation using Green’s functions. The obtained numerical results show that the frequency and radius of the electron beam rotation have the strongest influence on the distribution of the temperature field. The molten zone depth decreases from 25 to 17 µm for frequency variation from 5 to 10 kHz. Decreasing the beam rotating radius from 2.6 to below 2 mm leads to an increase in the molt depth from 10 to more than 30 µm. The model is verified by experimental investigation of layers formed by selective electron beam alloying of Al with TiCN nanoparticles, where the phase composition, layer thickness and microhardness were determined. The results show the successful incorporation of the nanoparticles in the surface layer, leading to an increase in their microhardness by 16–22 times. A good agreement is obtained between the experimental and the numerical results regarding the thickness of the molten zone, confirming the feasibility of the proposed model.

RETRACTED: Dual Solutions in a Boundary Layer Flow of a Power Law Fluid over a Moving Permeable Flat Plate with Thermal Radiation, Viscous Dissipation and Heat Generation/Absorption

The aim of the present study is to investigate the combined effects of the thermal radiation, viscous dissipation, suction/injection and internal heat generation/absorption on the boundary layer flow of a non-Newtonian power law fluid over a semi infinite permeable flat plate moving in parallel or reversely to a free stream. The resulting system of partial differential equations (PDEs) is first transformed into a system of coupled nonlinear ordinary differential equations (ODEs) which are then solved numerically by using the shooting technique. It is found that the dual solutions exist when the flat plate and the free stream move in the opposite directions. Dimensionless boundary layer velocity and temperature distributions are plotted and discussed for various values of the emerging physical parameters. Finally, the tables of the relevant boundary derivatives are presented for some values of the governing physical parameters.

Numerical simulation of low temperature on plastic runway of cement base

Surface polyurethane materials in sports venues, which have good elasticity, high strength, excellent wear resistance and fine damping capacity, easily crack in winter. These cracks will affect their service performance for applications in sports. In this study, the temperature and stress distribution in cement concrete base layers in sports venues was investigated. A transient, two-dimensional finite-element model was built to predict the transient temperature distributions at various depths in a plastic runway of cement concrete base using the Ansys software. The results show that the temperature change almost occurs in the surface polyurethane layer. The low thermal conductivity of the polyurethane layer will be helpful for temperature distribution across the layer in winter. It should be realized to control or decrease the crack’s appearance in the plastic runway. Ultimately, the model is aimed at providing runway engineers with an efficient computational tool that attempts to increase the prediction accuracy of temperature in plastic runways of cement concrete base layer in cold regions for more reliable runway design.

Modeling of controlled synthesis of intermetallic coatings

Composite materials and coatings creation in modern combined technologies is perspective direction in the science when exothermic synthesis and electron beam or laser treatment are used together. Similar multifactor technologies demand the employment of mathematical modeling. In this work, two-dimensional model of the formation on the ferrous substrate of intermetallic coating from the powders Ni and Al is suggested. The model takes into account the heating by moving energy source corresponding to electron beam and the staging of chemical conversion. Due to small thickness of the treated layer temperature and composition distributions along the coating depth are not analyzed in a first approximation. However, the possibility of intermixing of materials of the coating and substrate and corresponding chemical reactions are taken into consideration for the temperature close to the melting temperature. The model was realized numerically. The distributions of the temperature and concentrations of individual species and new phases are studied for different time moments. It was shown that multi-phase coating forms in the conditions under study. It is possible to control the phase composition of the coating varying the composition of initial powders and treatment parameters. Self-sustained regime does not realize because heat losses to the substrate are high. This corresponds to experimental data. Effective properties of the coating could be evaluated for quasistationary stage that establishes quickly for each pass of electron beam.

Three-dimensional finite element model to study temperature distribution in peripheral layers of human limbs immediately after physical exercise

The physical exercise imposes challenges on the human thermoregulatory system, as heat exchange between the body and environment is substantially impaired, which can lead to decrease in performance and increased risk of heat illness. In view of above a three-dimensional finite element model is proposed to study the effect of different intensities of physical exercise on temperature distribution in peripheral regions of human limbs under moderate climatic conditions. Human limb is assumed to have a cylindrical cross-section. The peripheral region of the human limb is divided into three natural components, namely epidermis, dermis and subdermal tissues. The model incorporates the effect of important physiological parameters like blood mass flow rate, metabolic heat generation, and thermal conductivity of the tissues. Appropriate boundary conditions have been framed based on the physical conditions of the problem. The model is transformed into the discretized variational form and finite element method (FEM) has been employed to obtain the solution. The numerical results have been used to obtain the temperature profiles in the region immediately after exercise for an unsteady state case. The thermal information generated from the model can be useful for developing protocols for improving performance of sportsmen, military persons and labor-intensive workers.

Flow mal-distribution study in cryogenic counter-flow plate fin heat exchangers

Plate Fin Heat Exchangers are one of the main components in modern large capacity helium liquefiers/refrigerators. These heat exchangers should have more than 95% effectiveness in order to liquefy helium gas. Design of these heat exchangers are complex one and govern by many parameters such as flow mal-distribution, variable fluid properties, heat-in-leak from ambient and longitudinal heat conduction through wall. Among these design parameters, flow mal-distribution within heat exchanger layers is one of the important design parameters for achieving higher effectiveness. Flow mal-distribution reduces the effectiveness significantly and may bring down it to a much lower value than design value. In the present study, a numerical model has been developed which is capable to evaluate layer by layer temperature distribution in presence of flow mal-distribution. Two major mal-distribution conditions, linear weighted and center weighted, might occurs when flow leads from nozzle to different layers in plate fin heat exchangers. Present work studied the effect of these two conditions on performance of plate fin heat exchanger in the temperature range of 300-90 K as a case study.

Modelling of 3D temperature profiles and pressure drop in concentric three-phase HTS power cables

To meet the increasing power demand in cities under the spatial constraints for cable channels, the application of high temperature superconducting (HTS) cables cooled with liquid nitrogen offers an increasingly attractive alternative to conventional cable solutions. This paper presents a differential equation model for three-phase concentric HTS cables, describing the temperature distribution in the various cable layers and in the liquid nitrogen flow. The design of the 1km long AmpaCity cable is used as a reference, which presently is the longest HTS cable installation in the world. The model considers the AC losses in the superconducting phases in addition to the external thermal load, as well as pressure losses in the coolant flow. The integrity of the algorithm is verified through energy conservation, yielding negligible numerical solver errors. The model is then applied to the operation of the AmpaCity cable. The monitoring of its operating range is explained, based on electrical and coolant properties measured at the cable end. The final application study shows options for extending the cable length up to factor five, using a second cooling unit in combination with a mixed coolant.