Electrothermal Analogy Research Articles

Calculation of termostabilization system led matrices by heat pipes

Using the method of electrothermal analogy, a mathematical model of the thermal stabilization system of the LED matrix with a heat pipe was developed. The system of differential equations is solved, including the stationary equation of heat conduction and the equation of heat generation, which are supplemented by boundary conditions of conjugation for heat fluxes and temperatures. The calculated temperature distribution in the structural elements of the thermal stabilization system depending on the power of the LED matrix, heat pipe parameters and the temperature of the environment. It is shown that the use of the proposed thermal stabilization system will allow to increase the luminous flux of the LED-matrix (increase the light power) without increasing the temperature of its active zone. This will allow to reduce the number of LED-matrix in the semiconductor lamp and its cost without shortening the service life.

Вплив енерговтрат імплантата з бездротовим живленням на тепловий стан організму

Technical means that create for regenerating lost functions of the human body primarily focused on the target function. However, even when implants achieve performance that corresponds to natural organs and systems, in many cases the developers do not pay enough attention to the energy supply of implants and additional heat load due to energy losses in mechanical, electrical, and electronic units. If you do not consider these factors, it limits the duration and medical safety of the devices. It is especially true for implants with significant power consumption and wireless power supply. Therefore, this work determines the allowable additional heat load of the human body to justify the choice of further circuit solutions for wireless powering of implants with significant energy consumption and long-term operation. The subject of research is the processes of heat exchange between the implant and body structures and their energy and temperature indicators. The research object was chosen as an implant of the type "Artificial Heart" device (AHD) with a maximum power of 20… 25 W and the magnetic induction principle of energy transfer. The research tasks are to analyze the processes of heat exchange between the implant and the biostructures of the body; to calculate quantitative indicators of energy exchange in the location of the main components of the implant; to determine the temperature of biotissues in the area of the receiving inductor. The subject of research is the processes of heat exchange between the implant and body structures and their energy and temperature indicators. The research object was chosen as the implant of the type "Artificial Heart" device (AHD) with a maximum power of 20… 25 W and the magnetic induction principle of energy transfer. The research tasks are to analyze the processes of heat exchange between the implant and the biostructures of the body; to calculate quantitative indicators of energy exchange in the location of the main components of the implant; to determine the temperature of biotissues in the area of the receiving inductor. Research results. The processes of heat exchange between the structural elements of the implant and the biostructures of the body have a complex combination of physiological and physical mechanisms. Estimates are made based on the thermal conductivity process, as the most objective in terms of known quantitative indicators. With an average efficiency of ~ 0.8 for mechanical, electrical, and electronic components of the implant "Artificial Heart," the human body can maintain a stable temperature of internal organs in the presence of an implant with a maximum power consumption of 20 watts. The calculation conducted using the method of electrothermal analogy showed a possible increase in the temperature of biotissues in contact with the surface of the receiving implanted inductor, by 1.32 ° C. This value refers to the critical levels of internal tissue temperature rise. Summary. For practical implementation of the autonomous device the Artificial Heart Device, it is necessary to combine known or to find the original circuit-technical and design decisions of construction of components of wireless power supply with the magnetic induction principle and efficiency of not less than 0,8. To prevent thermal overload of biotissues, it is advisable to introduce a temperature control channel at potentially critical locations of the implanted elements. It is possible to predict the finding of these critical points by calculations by the method of electrothermal analogy.

Thermal computer modeling of laser gyros at the design stage: a promising way to improve their quality and increase the economic efficiency of their development and production

In the paper, we consider the ways to improve the quality and economic efficiency of development and production of complex innovative electronic devices, among which are laser gyros (LGs). Development, manufacturing and testing of high-tech LG are relatively expensive. The accurate thermal modeling at the early stages of LG designing is an effective way to reduce overall costs owing to noticeable savings of expenses on multiple-laboratory tests of the LG under development and its re-design due to overheating. Use of the inexpensive Russian computer system ASONIKA for thermal modeling provides yet another boost to cost efficiency. In the paper, details of application of the electro-thermal analogy method, finite difference method, grid method, graph method in ASONIKA are described. The developed algorithm of creation of LG thermal model with the procedure of step-by-step disaggregation (zooming technique) is presented. The process of LG modeling by ASONIKA computer system is explained; the created LG thermal model in graphic view and the obtained thermal field of one of PCB in colored view are demonstrated. Electronic components prone to overheating are specified. The paper also presents the results of empirical verification of modeling with actual measurement of temperature by the thermal sensors installed in places corresponding to the model nodes; those measurements confirmed high accuracy of ASONIKA-based simulation.

Electrodynamic Apparatuses for Concentration of Solutions

The results of complex research of electrodynamic vacuum evaporators are presented. The scientific and technical concept of the directed energy action technology applicable to apparatuses of the electrodynamic type is substantiated. A system analysis of the energies of traditional dehydration equipment is given. Their technological and energy problems are determined by the electrothermal analogy method. It is shown how these problems are solved in the electrodynamic type apparatuses. A physical scheme and a mathematical model of a electrodynamic continuous operation vacuum evaporator are developed. Assumptions that take into account the specifics of evaporation in an electromagnetic field are formulated. A system of differential equations that defines the solution interaction with an electromagnetic field in vacuum is presented. A nonstationary model is transformed into relations in dimensionless variables using the methods of similarity theory and the “dimension analysis”. The tasks of experimental modeling are defined. The results of complex experimental studies of microwave vacuum evaporators are presented. The influence of the electromagnetic field power, the solution type and concentration, and the pressure level on the steam output is established. Constants of the equation in generalized variables, which, with an error within 8%, establishes the relationship of the number of energy actions with dimensionless complexes that characterize the technological parameters, are defined.

Mathematical modeling of heat-trapping properties of a developed radiator surface in mechanical engineering

In this work the research of heat-removing properties of areas of extended surfaces, for example, of finned and needle radiators for assessment of efficiency of distribution of a thermal field and heat extraction is described. Also the description of the carried-out computational modeling is provided in the Fluent processor of universal program system of the final and element analysis Ansys. The relevance of the selected subject is confirmed by the fact that one of the most important and difficult tasks arising when developing the electronic equipment is a withdrawal of heat generated by it. At a current steady trend in reduction of dimensions of electronic devices this problem does not disappear, and opposite, becomes more and more sharp, and that is stronger, than device high power less its physical volume, and not only the efficiency of heat extraction, but also dimensions and, of course, reliability of operation of electronic devices depends on constructions of heat-removing elements. In work the conclusion is drawn that for a solution of a complex problem of assessment of efficiency of the heat sink for the purpose of decrease in temperature of heatterminated element, it is necessary to use electrothermal analogy.

Heat model of a spindle support of a precesion metal cutting machine

Based on the use of the electrothermal analogy in describing the heat transfer process, an engineering technique has been developed to determine the thermal state of the supports of spindle assemblies, which does not require “heavy” software packages based on the application of the finite element method. The design features of modern control rooms made it possible to reasonably present the thermal model in the form of a flat model. The principles of dividing the blocks of a flat model into enlarged elements are proposed, taking into account the features of the geometry of the calculated structure and heat sources. A technique has been developed for determining the thermal resistance of an element of a calculated thermal model taking into account boundary conditions. The use of enlarged elements of the thermal model makes it easy to assess the influence of technological features of processing and assembly of individual structural parts on its thermal state. The presented methodology for developing a thermal model can be used to estimate stationary thermal processes of any axisymmetric structures with insignificant temperature variations.

Numerical junction temperature calculation method for reliability evaluation of power semiconductors in power electronics converters

The junction temperature of power semiconductors is a critical parameter during reliability evaluation. The incorporation of long-term mission profiles, such as power loadings and ambient temperature, into lifetime and reliability evaluations of power semiconductors increases the computational burden. Thus, there is an urgent need for a more accurate method for junction temperature acquisition. Current methods for junction temperature calculation are computationally inefficient and do not comprehensively incorporate long-term factors into junction temperature calculation and power semiconductor reliability evaluation. Here, a junction temperature calculation method is proposed that enables reliability evaluation for insulated gate bipolar transistor (IGBT) power semiconductors. This approach calculates the IGBT module junction temperature on the basis of an electro-thermal analogy using Gauss–Seidel iteration. When compared with electrical–thermal simulation and other numerical calculation methods, the proposed method guarantees accuracy, while greatly reducing the computational time and load. A performance comparison between the proposed method, electro-thermal simulation based on a Fuji IGBT simulator, and experimental results was carried out using a three-phase DC/AC inverter as a case study.

Compact Thermal Model of the Pulse Transformer Taking into Account Nonlinearity of Heat Transfer

This paper presents a compact nonlinear thermal model of pulse transformers. The proposed model takes into account differentiation in values of the temperatures of a ferromagnetic core and each winding. The model is formulated in the form of an electric network realising electrothermal analogy. It consists of current sources representing power dissipated in the core and in each of the windings, capacitors representing thermal capacitances and controlled current sources modelling the influence of dissipated power on the thermal resistances in the proposed model. Both self-heating phenomena in each component of the transformer and mutual thermal couplings between each pair of these components are taken into account. A description of the elaborated model is presented, and the process to estimate the model parameters is proposed. The proposed model was verified experimentally for different transformers. Good agreement between the calculated and measured waveforms of each component temperature of the tested pulse transformers was obtained. Differences between the results of measurements and calculations did not exceed 9% for transformers with a toroidal core and 13% for planar transformers.

Design and Development of a Battery Powered Electrofusion Welding System for Optical Fiber Microducts

At present, optical fiber microducts are coupled together by mechanical types of joints. Mechanical joints are thick, require a large space, and reduce the installation distance in multi-microduct installation. They may leak or explode in the blown fiber installation process. Mechanical joints are subjected to time dependent deterioration under long service times beneath the earth's surface. It may start with a small leakage, followed by damage due to water freezing inside the optical fiber microduct. Optical fiber microducts are made up of high-density polyethylene, which is considered most suitable for thermoelectric welding. For thermoelectric welding of two optical fiber microducts, the welding time should be one second, and should not cause any damage to the inner structure of the microducts that are being coupled. To fulfill these requirements, an LTspice simulation model for the welding system was developed and validated. The developed LTspice model has two parts. The first part models the power input to joule heating wire and the second part models the heat propagation inside the different layers of the optical fiber microduct and surrounding joint by using electro-thermal analogy. In order to validate the simulation results, a battery powered prototype welding system was developed and tested. The prototype welding system consists of a custom-built electrofusion joint and a controller board. A 40 volt 4 ampere-hour Li-Ion battery was used to power the complete system. The power drawn from the battery was controlled by charging and discharging of a capacitor bank, which makes sure that the battery is not overloaded. After successful welding, a pull strength test and an air pressure leakage test were performed to ensure that the welded joints met the requirements set by the mechanical joints. The results show that this new kind of joint and welding system can effectively replace mechanical joints in future optical fiber duct installations.

LTspice Electro-Thermal Model of Joule Heating in High Density Polyethylene Optical Fiber Microducts

At present, optical fiber microducts are joined together by mechanical type joints. Mechanical joints are bulky, require more space in multiple duct installations, and have poor water sealing capability. Optical fiber microducts are made of high-density polyethylene which is considered best for welding by remelting. Mechanical joints can be replaced with welded joints if the outer surface layer of the optical fiber microduct is remelted within one second and without thermal damage to the inner surface of the optical fiber duct. To fulfill these requirements, an electro-thermal model of Joule heat generation using a copper coil and heat propagation inside different layers of optical fiber microducts was developed and validated. The electro-thermal model is based on electro-thermal analogy that uses the electrical equivalent to thermal parameters. Depending upon the geometric shape and material properties of the high-density polyethylene, low-density polyethylene, and copper coil, the thermal resistance and thermal capacitance values were calculated and connected to the Cauer RC-ladder configuration. The power input to Joule heating coil and thermal convection resistance to surrounding air were also calculated and modelled. The calculated thermal model was then simulated in LTspice, and real measurements with 50 µm K-type thermocouples were conducted to check the validity of the model. Due to the non-linear transient thermal behavior of polyethylene and variations in the convection resistance values, the calculated thermal model was then optimized for best curve fitting. Optimizations were conducted for convection resistance and the power input model only. The calculated thermal parameters of the polyethylene layers were kept intact to preserve the thermal model to physical structure relationship. Simulation of the optimized electro-thermal model and actual measurements showed to be in good agreement.

Determining the Self-Thermal Impedances of Power Transistors and Diodes of an IGBT Module Based on Its 3D Model

An approach to determine self-thermal impedances for construction of a thermal model of a power IGBT module based on the electrothermal analogy method has been considered. Unlike the conventional method, the suggested approach takes into account a change in the thermal resistances depending on the location of a power semiconductor device in the IGBT module. The thermal parameters to construct the model of a power module based on the electrothermal analogy were determined by the finite element method using a 3D model of the IGBT module in the ANSYS environment. The suggested approach is intended to improve the quality of prediction of temperature of chips in the power module under conditions close to operating ones.

Modeling of Intrinsic Thermal Feedback in Resistance Temperature Devices

Цель работы - исследование внутренней тепловой обратной связи в датчиках температуры - термопреобразователях сопротивления - путем компьютерного моделирования. Модель создана на основе электротепловой аналогии, то есть на сходстве математических уравнений описания тепловых и электрических процессов. Это позволило, с одной стороны, рассматривать тепловые процессы как электрические, с другой - одновременно при этом включить в рассмотрение электрические процессы в схемах включения термопреобразователей в термоизмерительной аппаратуре. В качестве среды моделирования выбрана известная компьютерная программа Micro-Cap, разработанная фирмой Spectrum Software, которая позволяет осуществлять вычисления с погрешностью до десятых долей процента как в статическом, так и динамическом режимах. Существенным достоинством программы является возможность применять идеализированные компоненты с произвольно устанавливаемыми номиналами основных параметров, что ранее невозможно было сделать при физическом моделировании по методу электротепловой аналогии с применением реальных электрических компонентов, таких как резисторы, конденсаторы и др. По результатам моделирования сделаны практические выводы по построению термометрических приборов и применению результатов в смежных областях. В частности установлено, что при питании термопреобразователя от источника тока или при сопротивлении последовательного ему резистора в мостовой схеме большего сопротивления, чем у термопреобразователя, наблюдается положительная тепловая обратная связь. При питании термопреобразователя от источника напряжения или небольших по сопротивлению последовательных термопреобразователю резисторах наблюдается отрицательная обратная связь. Существуют условия, при которых обратная связь не проявляется. Исследована зависимость перегрева чувствительного элемента от значения измерительного тока. Установлено, что зависимость имеет нелинейный характер, и при относительно больших токах происходит резкое нарастание перегрева вплоть до расплавления чувствительного элемента. Установлено также, что для снижения внутренней тепловой обратной связи в теромпреобразователях сопротивления необходимо снижать значение измерительного тока и уменьшать термическое сопротивление чувствительный элемент - среда.

A Thermal Model of an IGBT Module Taking into Account Thermal Interconnections between Chips

An approach to development of the thermal model of an IGBT module based on the method of electro-thermal analogy is considered. Unlike traditional one-dimensional thermal models, a new model is supplemented with thermal interrelations between chips. The parameters of thermal interrelations were determined using studying the 3D-model of the power module in the ANSYS environment. The proposed model is intended to improve the quality of predicting the temperature of power module chips due to taking into account the thermal mutual influence of the chips.

Electrothermal Analysis With Nonconvective Boundary Conditions

Electrothermal analogy allows heat conduction and heat convection to be modeled as a simple resistive or RC network. A practical environment in which a chip is located is often not purely convective. Nonetheless, the environment is typically approximated as convective for simplicity of analysis. This yields inaccuracy of temperature estimation; ad-hoc calibration process is necessary to match estimation and measurement by empirically adjusting thermal parameters. In this brief: 1) we extract electrothermal analogy through mathematical derivation and 2) this allows us to understand how the basic resistive network can be modified to handle non-convective environment accurately. The new network is applied in the estimation of steady-state and transient temperature as well as in thermal design power. A smartphone under the sunlight is assumed as an example of non-convective environment. Estimation of steady-state temperature using our network is compared to actual measurement, which demonstrates its accuracy.

Lifetime estimation of IGBT modules for MMC-HVDC application

Modular multilevel converters (MMCs) usually work in harsh operating environments due to their compact layouts and adverse mission profiles, which accelerate the thermomechanical fatigue process in insulated-gate bipolar transistor modules (IGBTs). Accurate lifetime estimation is desired to conduct reliability prediction and develop maintenance policies. This paper presents an analytical approach to estimating the lifetimes of IGBTs for MMC-HVDC application based on the thermal cycles, which are influenced by the transmission power profile and ambient temperature profile. The structure and operating principle of MMCs are studied to develop an analytical model for computing the IGBT power loss. A thermal equivalent network in the form of a Foster model is adopted to link the power losses and junction temperature. Next, an RC equivalent circuit analytical method for characterizing the fundamental-frequency thermal cycles, developed using electrothermal analogy theory, is proposed. The rainflow counting algorithm is applied to extract the low-frequency thermal cycles from the annual junction temperature data computed at every minute. The Bayerer model is employed to predict the IGBTs lifetime. Finally, the lifetime distribution, mission profiles and comparison of different IGBTs are analyzed via case studies.

THERMAL PROCESSES MODELING IN QUASI-DIFFERENTIAL CALORIMETER

The model of the quasi-differential calorimetric system based on the electrothermal analogy method is proposed. Using the model, the dynamics of average temperatures and heat flow changes in the system elements, the temperature perturbations and the technological parameters spread influences on the measurement error are researched.

THE METHOD OF CALCULATION AND ANALYSIS OF HEAT TRANSFER COEFFICIENT OF BIMETALLIC FINNED TUBES OF AIR COOLING UNITS WITH IRREGULAR EXTERNAL CONTAMINATION

The article focuses on a new method of calculating heat transfer coefficient of bimetallic finned tubes of air coolers taking into account external operational pollution. In contrast to wellknown methods that use the assumption of a uniform distribution of operational contamination layer with a constant thickness over the entire surface of the fins in the present method being introduced it is assumed that the thickness of the pollution layer during long-term operation is changed irregularly. Under such conditions the thickness of the pollution layer at the base of the fins becomes much greater than at the rest of the finned surface. The suggested method is based on a mathematical model developed with the use of the method of electrothermal analogy, whereby the heat flow through the wall of the finned tube is considered as divided into two components, viz. through the annular layer of outside contamination adjacent to the base of the ribs, and through the remaining part of the external ribbed surface covered with a thin layer of pollution. Within the framework of the developed methodology a new method for determining the thermal resistance of the pollution layer, which is based on analytical solution of two dimensional problem of heat conduction in the annular layer has been created. With the use of this technique the influence of the degree of contamination of the intercostal space of the industrially manufactured bimetallic finned tubes on the heat transfer coefficient has been studied taking into account the intensity of heat transfer of air and the properties and composition of the pollutant for industrial manufactured bimetallic finned tubes. It is established that a layer thickness of the pollutant at the base of the ribs has the greatest influence on the heat transfer coefficient. This is due primarily to the change of actual coefficient of the fins. It is demonstrated that the heat conductivity of the external pollutant has a significant impact on the heat transfer coefficient when the heat exchanger functions in the mode of forced convection of air.

A new analytical electro-thermal model in 3D resistive switching memory arrays

Resistive switching memory (RRAM) with three-dimensional (3D) integration is one of the most effective methods to satisfy the requirement of ultra-high density and ultra-large data storage. With the increase of the integration density of 3D RRAM, Joule heating effect and thermal crosstalk of the RRAM device will seriously affect the stability, reliability and life of RRAM device. Therefore, the biggest challenge for 3D RRAM is how to solve the problem of the thermal effect. Otherwise, the thermal effect will be particularly prominent as the feature size of RRAM device is ceaselessly decreased. Especially with the improving of the storage cell densities and hence the decreasing of the distance between adjacent cells, the thermal crosstalk from the adjacent cells will seriously restrict the development and application of 3D integrated RRAM. In this work, we present a new electro-thermal compact model for 3D RRAM arrays. The proposed model is based on the electro-thermal analogy which can couple thermal network to its electrical schematic. The comparison between the compact model simulation results and numerical simulation shows a good accuracy. This proposed model can be used to predict temperature distribution and analyze thermal crosstalk in 3D RRAM arrays. Our work will provide a reliable technical support for the late circuit design and practical application, and lay the foundation for the realization of the high-density 3D integration RRAM.

Accuracy Enhancement of Thermoelectric Simulation by Modeling the Electrical Contact

The main objective of this study is to numerically analyze the uncertainty of the electrical interface resistance in thermoelectric modules (TEMs) and its contribution to the error of practical device and system simulation. To improve the simulation, the numerical implementation of the interface resistance in TEMs of any size, especially its temperature-dependent characteristics, is critical in the thermoelectric modeling. Using the electrothermal analogy and the PSpice simulator as the simulation baseline, the proposed nonlinear and statistical modeling of the interface resistance is examined and supported through extensive comparisons between experimental findings and numerical results. Considerable accuracy improvement is obtained for a single TEM and a system consisting of a number of interconnected TEMs.

Simulation of a Superconducting Fault Current Limiter: A Case Study in the Brazilian Power System With Possible Recovery Under Load

In this paper, simulations of superconducting fault current limiters (SFCLs) in a real scenario are presented as an alternative solution for overstressing installed components in a substation of the Brazilian Interconnected Power System. A technical comparison between SFCLs and air-core reactors has been made. Simulations were based on the electrothermal analogy method, which allows the study of the electrical transitory and thermal behavior of the device with low computational effort. The simulated design of SFCL is supposed to operate without a circuit breaker in line with the device, since its design enables its recovery to normal operating conditions under load. Simulations indicate that SFCLs may be more effective than air-core reactors for protecting the substation in study. Furthermore, a fast recovery to the superconducting state has been found.