Academic literature on the topic 'Lumped heat capacities method'
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Journal articles on the topic "Lumped heat capacities method"
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Andriotty, Tiago Haubert, Letícia J. Rodrigues, Luiz Alberto Oliveira Rocha, and Paulo Smith Schneider. "Optimization of a Sensible Thermal Storage System by a Lumped Approach." Defect and Diffusion Forum 366 (April 2016): 182–91. http://dx.doi.org/10.4028/www.scientific.net/ddf.366.182.
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This study is focused on the optimization of a sensible thermal storage system subjected to a cyclic energy source. The objective is to minimize the system heat storage mass and its geometry to guarantee its operation within an admissible temperature range. The storage medium is modeled as a Lumped system and the working fluid by a non-capacitive energy balance. The storage medium is composed of an array of parallel flat plates submitted to an air stream. The optimization is based on an exhaustive search method. It is observed that the minimum heat storage mass is proportional to the mass airflow rate. An optimal relationship between the superficial heat transfer rate and the fluid flow inertia, given by the dimensionless parameter NTU, is found to be constant (4.03) and independent in respect to the mass flow rate. The system time constant was invariable (3,230 s) for the optimal relationship between the interface heat transfer rate and the system inertia.
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Chatrath, Anmol, and Neel Kanth Grover. "Transient Heat Transfer Solution Using Improved Lumped Model." Applied Mechanics and Materials 813-814 (November 2015): 773–75. http://dx.doi.org/10.4028/www.scientific.net/amm.813-814.773.
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In present study, transient state one-dimensional heat conduction is analyzed using polynomial approximation method. In comparison with the classical lumped model, an improved lumped model have been employed as the classical lumped model is applicable for biot number of less than 0.1 and it cannot be used for high temperature gradient. An improved lumped model has been employed for sphere to calculate average temperature as a function of time for higher and lower values of biot number. The study shows that the lumped model provides better accuracy as compared to finite difference model.
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Li, Bin, Liang Yan, and Wenping Cao. "An Improved LPTN Method for Determining the Maximum Winding Temperature of a U-Core Motor." Energies 13, no. 7 (March 28, 2020): 1566. http://dx.doi.org/10.3390/en13071566.
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In a traditional lumped-parameter thermal network, no distinction is made between the heat and non-heat sources, resulting in both larger heat flux and temperature drop in the uniform heat source. In this paper, an improved lumped-parameter thermal network is proposed to deal with such problems. The innovative aspect of this proposed method is that it considers the influence of heat flux change in the heat source, and then gives a half-resistance theory for the heat source to achieve the temperature drop balance. In addition, the coupling relationship between the boundary temperature and loading position of the heat generator is also added in the lumped-parameter thermal network, so as to amend the loading position and nodes’ temperature through iterations. This approach breaks the limitation of the traditional lumped-parameter thermal network: that the heat generator can only be loaded at the midpoint, which is critical to determining the maximum temperature in asymmetric heat dissipation. By adjusting the location of heat generator and thermal resistances of each branch, the accuracy of temperature prediction is further improved. A simulation and an experiment on a U-core motor show that the improved lumped-parameter thermal network not only achieves higher accuracy than the traditional one, but also determines the loading position of the heat generator well.
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Oliveira, Pedro N., Elza M. M. Fonseca, and Raul D. S. G. Campilho. "Easy Trends to Analyse Structural Profiles: Lumped Capacitance Vs Simplified Equation." International Journal of Safety and Security Engineering 10, no. 5 (November 30, 2020): 625–29. http://dx.doi.org/10.18280/ijsse.100506.
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This work presents the calculation of the temperature in different cross-sections of structural profiles (IPE, HEM, L and UAP) using the lumped capacitance method and the simplified equation from Eurocode 3 part 1-2. The lumped capacitance method allows the temperature calculation of the solid body at any time instant during the heat transient process, as a constant and uniform value. The simplified equation from Eurocode 3 part 1-2 is a simple model for heat transfer based on the uniformly distributed temperature over the cross-section surface and directly proportional to section factor of the element. Steel profiles have as almost thermal behaviour uniform during the heat transfer process when submitted to fire conditions and the lumped capacitance method allows a great simplification to estimate the temperature field in the element and may be used when Biot number is lower than unity. Therefore, thermal analysis of solids with high thermal conductivity using this method is adequate. For the studied steel profiles, a thermal analysis was also performed using the simplified equation from the Eurocode 3 part 1-2 in order to validate the obtained results from the lumped capacitance method. The results from both methods are presented for discussion and analysis.
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Borodin, Vladimir N., Valery A. Kozlov, Evgeny A. Mikhalitsyn, and Alexander V. Sorokin. "Computer aided design of ferrite lumped element circulators." Physics of Wave Processes and Radio Systems 23, no. 4 (February 11, 2021): 74–84. http://dx.doi.org/10.18469/1810-3189.2020.23.4.74-84.
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The results of integrity of narrowband and wideband lumped element circulators design methodology to the computer aided design system of microwave devices AWR Microwave Office are presented in the article. The calculation method of narrow band circulators circuits which consist of serious and shunt tuning capacities is investigated. The simple and visual method of wideband ferrite isolators optimize design based on circulation impedance calculation is described here. The results of design of the ultra wideband circulator with shunt capacity, serious resonant matching circuit and serious resonant circuit between common terminal and ground are considered. The new theoretical results of calculation of two schematics of wideband high power circulators with serious tuning capacity are presented. The first schematic is formed with matching resonant network being connected in serious at each terminal. It is shown that double hump characteristic is realized. The second schematic is formed with serious resonant network connected between common terminal and the ground. It is shown that four-order Tchebycheff characteristic is realized.
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Chen, C. M., and V. Thomée. "The lumped mass finite element method for a parabolic problem." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 26, no. 3 (January 1985): 329–54. http://dx.doi.org/10.1017/s0334270000004549.
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AbstractFor the heat equation in two space dimensions we consider semidiscrete and totally discrete variants of the lumped mass modification of the standard Galerkin method, using piecewise linear approximating functions, and demonstrate error estimates of optimal order in L2 and of almost optimal order in L∞.
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Zhao, Li Bin, Yuan Wei Li, and Feng Rui Liu. "Taylor Series Numerical Method in Transient Heat Conduction Analysis." Applied Mechanics and Materials 275-277 (January 2013): 677–80. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.677.
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Taylor series numerical method (TSNM) is extended to the field of transient heat conduction. Theoretical description of TSNM for transient heat conduction problems is presented. Furthermore, the algorithm is realized and embedded in commercial software ANSYS®. If a lumped mass heat capacity matrix provided, the governing equation of transient heat conduction problems, which is a differential equation, will be solved by a series of recursion calculation of Taylor expanding coefficients. A typical transient heat conduction problem with analytical solution was discussed to verify the TSNM. At last, the TSNM is applied in the transient heat analysis of an all-solid fiber optic gyro (FOG).
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Sugianto, A., Michiharu Narazaki, and M. Kogawara. "Iterative Modification of Lumped Heat Capacity Method on Predicting Residual Stress and Distortion of Still-Quenched S45C Steel Cylinder." Materials Science Forum 561-565 (October 2007): 1857–60. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.1857.
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Computer simulation can be utilized to predict the property and quality of heat-treated products. The prediction accuracy depends upon the thermal boundary condition and the thermal history from which surface heat transfer coefficient (HTC) is derived. Variables studied are thermal boundary and the surface HTC. Zone-based thermal boundary is set with and without edge effect. Lumped heat capacity method is used to predict HTC of silver probe (1st step), then iterative modification method is applied to the prediction of HTC of SUS304 cylinder (2nd step) and S45C cylinder itself (3rd step). Using FEM tool of DEFORM-HT combined with lumped heat program LUMPPROB, this research is intended to obtain the number of thermal boundary and iterative modification step. The higher accuracy is obtained by employing the edge effect of thermal boundary. The 2nd step significantly increases the prediction accuracy of radial distortion and residual stress distribution. However, 3rd step does not significantly increase the prediction accuracy.
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Stanisic, Stevan, Milica Jevtic, Bhaba Das, and Zoran Radakovic. "Fem CFD analysis of air flow in kiosk substation with the oil immersed distribution transformer." Facta universitatis - series: Electronics and Energetics 31, no. 3 (2018): 411–23. http://dx.doi.org/10.2298/fuee1803411s.
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In practice of loading of oil-immersed distribution transformers, there is a need to have lumped thermal model, requiring no big computational resources and computational time. One such model is presented in international transformer loading guide (IEC 60076-7), where heat transfer inside the transformer is modeled. In case of indoor transformer operation, this model does not consider transient thermal phenomena in the room. We developed a lumped model that includes heat transfer in the transformer room. In scope of the research, we also built FEM CFD (finite element method, computational fluid dynamics) model of air flow and heat transfer. The purpose of FEM CFD was to make a better insight into air flow, i.e. to study the simplifications introduced in lumped model and suggest potential improvements. This paper presents results achieved with FEM CFD. The considered case was the transformer with natural oil and natural air flow (ONAN).
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Silva, Humberto, and Jay S. Golden. "Spatial Superposition Method via Model Coupling for Urban Heat Island Albedo Mitigation Strategies." Journal of Applied Meteorology and Climatology 51, no. 11 (November 2012): 1971–79. http://dx.doi.org/10.1175/jamc-d-11-064.1.
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AbstractA spatial superposition design is presented that couples the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) with the National Center of Excellence (NCE) lumped urban thermal model for application to the city of Phoenix, Arizona. This technique utilizes an approach similar to Reynolds decomposition from turbulence theory. The presented decomposition takes the NCE model prediction from a mitigated strategy as the mean temperature and the difference between the NCE and MM5 predictions without mitigation strategy as the perturbed temperature. The goal of this coupled model is to provide spatial variability when simulating mitigation strategies for the urban heat island effect, as compared with the spatially invariant lumped model. A validation analysis was performed incorporating a maximum 35% change from the baseline albedo value for the urban environment. It is shown that the coupled model differs by up to 0.39°C with comparable average surface temperature predictions from MM5. The coupled model was also used to perform analysis of three different albedo-driven spatial mitigation schemes. This resulted in the identification that having a lesser number of mitigated points on a square urban grid in Phoenix with the same average albedo leads to a greater reduction in average hourly temperature.
Dissertations / Theses on the topic "Lumped heat capacities method"
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Антонец, Тарас Юрьевич. "Метод и устройство контроля кратковременной перегрузочной способности высоковольтного кабеля в условиях производства." Thesis, НТУ "ХПИ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21791.
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Диссертация на соискание научной степени кандидата технических наук по специальности 05.11.13 – приборы и методы контроля и определения состава веществ. – Национальный технический университет "Харьковский политехнический институт", Харьков, 2016.
Диссертация посвящена разработке метода контроля кратковременной перегрузочной способности высоковольтного силового кабеля в условиях производства и необходимый комплекс аппаратуры для его экспериментального подтверждения. Предложена модель нагрева жилы в начальный период нагрева кабеля, которая является решением дифференциального уравнения второй степени для теплового баланса в течение адиабатного нагрева кабеля. Модель позволила количественно характеризовать кратковременную перегрузочную способность кабеля и сравнивать ее с кратковременной перегрузочной способностью, полученной с помощью известных моделей нагрева кабеля. Предложен количественный показатель кратковременной перегрузочной способности высоковольтного кабеля со сшитой полиэтиленовой изоляцией для контроля изготовленных кабелей в условиях производства. Данный показатель не зависит от условий окружающей среды, а значит, является качественной характеристикой самого кабеля. Создан и опробован комплекс аппаратуры для определения показателя кратковременной перегрузочной способности высоковольтного кабеля в условиях производства. Проверен разработанный метод оперативного неразрушающего контроля показателей кратковременной перегрузочной способности на примере СПЭ-кабеля на напряжение 35 кВ.Dissertation for the degree of Ph. D. in Engineering Science, specialty 05.11.13 – Devices and methods of testing and materials structure determination. – National Technical University "Kharkov Polytechnic Institute", Kharkov, 2016. The thesis is devoted to the developing of control method of the short-term over-load capacity of high voltage cable in the conditions of production and the required complex of equipment for the verification of method. It was proposed the quantitative criterion of the short-term overload capacity of high voltage cable with cross linked polyethylene insulation for the control of the manufacturing cables in the conditions of production. It was created and proofed the complex of equipment for determination the criterion of the short-term overload capacity of high voltage cable in the conditions of production. The developed prompt method of the nondestructive testing of the quantitative criteria of the short-term overload capacity was tested on the 35 kV XLPE-cable.
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Антонець, Тарас Юрійович. "Метод і пристрій контролю короткочасної перевантажувальної здатності високовольтного кабелю в умовах виробництва." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21790.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.11.13 – прилади і методи контролю та визначення складу речовин. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2016 р.
Дисертація присвячена розробці методу контролю короткочасної перевантажувальної здатності високовольтного силового кабелю в умовах виробництва та необхідний комплекс апаратури для його експериментального підтвердження. Запропоновано модель нагріву жили в начальний період нагріву кабелю. Модель дозволила кількісно характеризувати короткочасну перевантажувальну здатність кабелю і порівнювати її з короткочасною перевантажувальною здатністю, одержаною за допомогою відомих моделей нагріву кабелю. Виконано теоретичні та експериментальні дослідження для визначення теплофізичних параметрів відведення тепла з поверхні кабелю в приміщенні та дослідження залежності нагріву кабелю від відстані між фазами при прокладанні в площині. Запропоновано кількісний показник короткочасної перевантажувальної здатності високовольтного кабелю зі зшитою поліетиленовою ізоляцією для контролю виготовлених кабелів в умовах виробництва. Перевірено розроблений метод оперативного неруйнівного контролю показників короткочасної перевантажувальної здатності на прикладі ЗПЕ-кабелю на напругу 35 кВ.Dissertation for the degree of Ph. D. in Engineering Science, specialty 05.11.13 – Devices and methods of testing and materials structure determination. – National Technical University "Kharkov Polytechnic Institute", Kharkov, 2016. The thesis is devoted to the developing of control method of the short-term over-load capacity of high voltage cable in the conditions of production and the required complex of equipment for the verification of method. It was proposed the quantitative criterion of the short-term overload capacity of high voltage cable with cross linked polyethylene insulation for the control of the manufacturing cables in the conditions of production. It was created and proofed the complex of equipment for determination the criterion of the short-term overload capacity of high voltage cable in the conditions of production. The developed prompt method of the nondestructive testing of the quantitative criteria of the short-term overload capacity was tested on the 35 kV XLPE-cable.
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Jandaud, Pierre-Olivier. "Étude et optimisation aérothermique d'un alterno-démarreur." Thesis, Valenciennes, 2013. http://www.theses.fr/2013VALE0018/document.
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Cette thèse porte sur l’étude et l’optimisation aérothermique d’un alterno-démarreur utilisé dans les véhicules hybrides. Ces machines produisant beaucoup plus de puissance qu’un alternateur classique, leur refroidissement est donc critique. La machine est modélisée en utilisant la méthode nodale en régime permanent qui utilise des réseaux de conductances thermiques. Pour alimenter le modèle, on utilise des corrélations issues de la littérature pour modéliser les transferts convectifs et on effectue des calculs CFD de la machine complète pour obtenir la répartition des débits. Les résultats obtenus numériquement sont ensuite validés expérimentalement à l’aide d’essais par Vélocimétrie par Images de Particules et d’essais thermiques par mesure thermocouples. Dans un deuxième temps, on couple un algorithme d’optimisation au code pour obtenir une géométrie de la machine optimale d’un point de vue thermique. La méthode retenue est l’Optimisation par Essaim Particulaire (PSO). L’optimisation se fait sur la taille des têtes de bobines, la position des ventilateurs et la section des canaux rotoriques. On obtient des géométries différentes selon les objectifs que l’on cherche à atteindre. La dernière partie de la thèse porte sur l’optimisation multi-objectifs d’un dissipateur située sur la partie électronique à l’arrière de l’alternateur : le dissipateur doit refroidir le plus possible l’électronique sans pour autant perturber l’écoulement. On étudie aussi plusieurs formes d’ailettes pour atteindre ces objectifsThe goal of this thesis is the aero-thermal study and optimization of a starter-alternator used in hybrid cars. This kind of machines being more powerful than a regular alternator, their cooling is critical. The machine is modeled using lumped method in steady state which uses networks of thermal conductances. The inputs for the model are obtained using correlations from bibliography for the convective heat transfers and three dimensional CFD for the flow rates inside the machine. The numerical results are validated by experimental results with PIV for the fluid results and a machine fitted with thermocouples for the thermal part. In the second part, the thermal code is coupled with an optimization algorithm to obtain an optimal geometry of the machine from a thermal point of view. The method chosen is Particle Swarm Optimization (PSO). The parameters are the sizes of the end-windings, the positions of the fans and the cross section of the rotor channels. For different objectives, different optimal geometries are obtained. The last part of this work aims at the multi-objectives optimization of a heat sink located at the back of the machine. The heat sink has to be thermally efficient but should not affect the flow. Different shapes of fins are also studied
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Pao-JuChen and 陳寶如. "Analysis of Metal-Mold Interfacial Heat Transfer by Using Lumped Capacitance Method." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/b5adjh.
Full textBook chapters on the topic "Lumped heat capacities method"
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Sugianto, A., Michiharu Narazaki, and M. Kogawara. "Iterative Modification of Lumped Heat Capacity Method on Predicting Residual Stress and Distortion of Still-Quenched S45C Steel Cylinder." In Materials Science Forum, 1857–60. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-462-6.1857.
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Kum Ja, Marip, Qian Chen, Muhammad Burhan, Doskhan Ybyraiymkul, Muhammad Wakil Shahzad, Raid Alrowais, and Kim Choon Ng. "Direct Contact Heat and Mass Exchanger for Heating, Cooling, Humidification, and Dehumidification." In Heat Exchangers. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.102353.
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A direct-contact heat and mass exchanger (DCHME) has many advantages over a traditional surface-type heat exchanger, including a high heat transfer coefficient, simplicity of design, and low OPEX and CAPEX. DCHME has a capability to exchange of both heat and mass between the two fluids in the same process. Hence, DCHMEs are widely used in numerous applications in various industries, including the air conditioning industry for cooling and dehumidification and heating and humidification. Based on their structure, DCHME can be categorized into two groups; two fluids direct contact (TFDC) exchanger and two direct contacts with one non-contact fluid (TDCONF) exchanger. This study developed a mathematical model for these two types of exchangers by using a discretized volume with distributed lumped-parameters method instead of using the conventional log mean enthalpy difference (LMHD) and NTU-effectiveness method. Thus, this model can reflect both heat and mass transfer behavior in every spatially distributed physical system. The objective of this study is to develop a mathematical model to be used as a tool for designing DCHME and to be applied as a sub-function of the model predictive control system to predict the effectiveness and dependent parameters of DCHME under the different load conditions and its various input parameters.
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"Structure and Properties of Composite Adsorbents Salt Inside Porous Matrix." In Technology Development for Adsorptive Heat Energy Converters, 43–87. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-4432-7.ch003.
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The chapter is devoted to structure and properties of composite adsorbents ‘salt inside porous matrix'. Characteristics of adsorbents ‘salt inside porous matrix', such as ‘zeolite – crystalline hydrate', ‘vermiculite – crystalline hydrate', ‘silica gel – crystalline hydrate' were analysed. Main advantages of composite adsorbents are shown to be higher adsorptive capacity and lower regeneration temperature as compared with host matrix. Adsorptive capacities of composite materials are shown to be significantly enhanced by introduction of salts in host matrix such as zeolite, vermiculite, or silica gel. Water uptake by composite adsorbent is shown to be increased by rising the salt content in it. The drawback of most of existing impregnation technologies is shown to be impossibility of obtaining composite with salt content more than 40 – 60% along with complexity. Sol gel method is shown to be an alternative for conventional impregnation methods. Properties of adsorbents ‘silica gel – sodium sulphate' synthesized according to sol gel method developed by authors were considered. The composite ‘silica gel – sodium sulphate' composition and structure were studied by IR-spectroscopy and wide-angle x-ray scattering. Adsorptive properties of crystalline Na2SO4 when allocated in silicon oxygen matrix are shown to result from dispersion up to nanoscale. Adsorptive capacities and heat of adsorption of composites ‘silica gel – sodium sulphate' and ‘silica gel – sodium acetate' surpass almost by 30% the value calculated from the linear superposition of the sorption capacities of the sorbent and massive salt. Their adsorption properties are shown to be not a linear combination of properties of silica gel and salt. The formation of a unique structure promoting an increase in the rate of reaction between crystalline hydrates and water vapor in the developed pores of the silicon-oxygen matrix is confirmed. It leads to increasing the heat of adsorption and the heat energy storage density. Strong difference of water sorption kinetic curves of composite ‘silica gel – sodium sulphate' and massive sodium sulphate is revealed. The correlation of their composition, structure, water adsorption kinetic, and operating characteristic as heat storage material is stated.
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Taler, Dawid, Jan Taler, and Marcin Trojan. "The CFD Based Method for Determining Heat Transfer Correlations on Individual Rows of Plate-Fin and Tube Heat Exchangers." In Heat Transfer - Design, Experimentation and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97402.
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The chapter provides an analytical mathematical model of a car radiator, which includes different heat transfer coefficients (HTCs) on the first and second row of pipes. The air-side HTCs in the first and second row of pipes in the first and second pass were calculated using the correlations for the Nusselt number, which were determined by CFD simulation using the ANSYS software. Mathematical models of two radiators were built, one of which was manufactured of round tubes and the other of oval tubes. The model permits the determination of thermal output of the first and second row of tubes in the first and second pass. The small relative differences between the thermal capacities of the heat exchanger occur for different and uniform HTCs. However, the heat flow rate in the first row is much greater than the heat flow in the second row if the air-side HTCs are different on the first and second tube row compared to a case where the HTC is uniform in the whole heat exchanger. The heat transfer rates in both radiators calculated using the developed mathematical model were compared with those determined experimentally. The method for modeling of plate-fin and tube heat exchanger (PFTHE) proposed in the paper does not require empirical correlations to calculate HTCs both on the air side and on the inner surfaces of pipes. The presented method of calculating PFTHEs, considering different air-side HTCs evaluated using CFD modeling, may considerably reduce the cost of experimental research concerning new design heat exchangers implemented in manufacturing.
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Vinogradov, Alexander, Anatoly Sopov, Vadim Bolshev, and Alina Vinogradova. "Gainful Utilization of Excess Heat From Power Transformers." In Handbook of Research on Smart Computing for Renewable Energy and Agro-Engineering, 132–62. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-1216-6.ch006.
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The study analyzes the various methods of gainful utilization of excess heat from power transformers. The ways to reduce heat loss inside the tank power transformer are found. The potential amount of heat emitted by power transformers of different capacities is calculated. New ways of combining the functions of electric transformation and heating in a power transformer are described. A system has been developed to use the excess heat of power transformers in the agricultural power systems. There are the structural and schematic diagrams of the system and a method for calculating its main elements. An improved design of the power transformer cooling system has been developed to combine the functions of electric transformation and heating. Experiments to verify the effectiveness of decisions are described. A feasibility study of the implementation of the developed system was carried out.
Conference papers on the topic "Lumped heat capacities method"
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Fernandez, Christopher, and Sheldon Jeter. "Comparison and Implementation of Thermally Massive Wall and Roof Models for Use in Simplified Building Energy Models." In ASME 2019 13th International Conference on Energy Sustainability collocated with the ASME 2019 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/es2019-3909.
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Abstract Although contemporary and complex building energy models such as EnergyPlus are highly advanced and predictive, a simplified building energy model has many advantages and applications. Chief among the advantages are adaptability to the measured response of a building and conciseness in computer implementation. Important applications will include automated fault detection. One of the most important aspects of a successful building energy model is the ability to accurately account for the heat capacity of the structure, especially the envelope. As part of the development of a simplified physics-based building energy model, a variety of roof and wall models were considered. Three different generic models were considered for opaque walls and roofs (1) an analytical model with closed-form solution, (2) a time-series solution using the ASHRAE transfer function method, and (3) a lumped capacity model with various numbers of capacitive nodes. This paper will describe an investigation of various simplified models for the transient conduction through building walls. Specifically, how different kinds of wall constructions and materials can change when the conduction load passes through the wall and when it impacts the HVAC system. Understanding how the physics of dynamic envelope loading can change how much energy a building uses for heating or cooling and when room conditioning loads occur is vital for energy savings and proper modeling.
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Cao, Jianping, Cong Liu, and Yinping Zhang. "The Applied Condition of Lumped Parameter Method for Finite Mass Transfer Duration." In The 15th International Heat Transfer Conference. Connecticut: Begellhouse, 2014. http://dx.doi.org/10.1615/ihtc15.tdy.008937.
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Gandla, Pavan, and Naresh Nidamanuri. "Accurate Prediction of Buffer Air Temperatures Using Lumped Heat Transfer Method." In ASME 2019 Gas Turbine India Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gtindia2019-2519.
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Abstract Buffer air system plays a vital role in gas turbine engines as it pressurizes bearing compartments, thermal conditioning of life limiting parts, purging the hot gas ingestion and antiicing. Buffer air is normally tapped from compressor section and routed to several locations of the engine through tubes, struts and ducts. Air supply is controlled though a buffer valve which sources air from different sources based on the flight condition. Accurate prediction of steady state buffer air temperature is critical in achieving gas turbine performance, durability and operability. It allows design community to determine optimum amount of buffer air which directly impacts gas turbine efficiency. As buffer air passes through different section of the engine by the time it reaches its intended destination, it losses or gains heat which eventually alter its temperature. Buffer air is currently modelled through a network of chambers and restrictors which is solved through an iterative solver for flow and energy convergence. Heat transfer is neglected in this solver and captures only enthalpy balance and pressure losses. An effort has been made to capture buffer air convective heat transfer as it passes through many channels and ducts on its routing. Lumped heat transfer method is employed and estimated the delta temperature b/w inlet and outlet of the corresponding passage. Outside and inside heat transfer coefficients are estimated using empirical correlations. Under steady state conditions, Final temperature of the buffer air would be the surrounding air temperature at that location and initial temperature of the air is its entry temperature. This delta temperate is incorporated in the buffer air network which then predicts corrected buffer air temperature for any flight conditions. With this methodology predicted buffer air Temperature is matched very close to thermo couple test data for various engine power conditions. Buffer air network model fidelity is greatly improved and gives greater confidence on air temperature for any flight conditions. Design studies are carried out and made a recommendation to incorporate thermal barrier coating on passages so that buffer temperature is retained which improves its thermal conditioning capabilities.
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Bermúdez, Alfredo, and Francisco Pena. "The Galerkin Lumped Parameter Method for Thermal Problems." In ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/esda2012-83003.
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In this contribution, we present a method called Galerkin lumped parameter (GLP) method, as a generalization of the lumped parameter models used in engineering. This method can also be seen as a model-order reduction method. Similarities and differences are discussed. In the GLP method, introduced in [1], domain is decomposed into several sub-domains and a time-independent adapted reduced basis is calculated solving elliptic problems in each sub-domain. The method seeks a global solution in the space spanned by this basis, by solving an ordinary differential system. This approach is useful for electric motors, since the decomposition into several pieces is natural. Numerical results concerning heat equation are presented. Firstly, the comparison with an analytic solution is shown to check the implementation of the numerical algorithm. Secondly, the thermal behavior of an electric motor is simulated, assuming that the electric losses are known. A comparison with the solution obtained by the finite element method is shown.
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Chipman, Veraun, Bruce Kirstein, and John Case. "Yucca Mountain Project Preclosure Ventilation Heat Transfer Analysis: Solution Method and Results." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56387.
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The thermal energy balance for emplacement drift ventilation is solved analytically by using “well-mixed” volume elements that discretize the domain down the length of a drift. The solution technique is based on the use of a lumped parameter quasi-steady-state approximation, and the principle of superposition. The lumped parameters are convective and linearized radiation heat transfer coefficients. The quasi-stead-state approximation allows the energy balance equations to be written without time derivatives and solved algebraically for a single time step. The progress of the heat transfer analysis through time is like that of integrating a function using Euler’s method. The principle of superposition is used to calculate the temperature response of the drift wall due to an arbitrary heat flux and a given set of thermophysical rock properties. The results of this calculation are used as a “multiplier” on the drift wall heat flux in the algebraic solution of the four energy balances, and eliminates the need to solve the conduction heat transfer in the rock mass at every time step. The results of the analysis are compared to a similar numerical model and include time and location dependent waste package, in-drift air, and drift wall temperatures, and ventilation efficiencies.
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Sherwin, Keith, and Henry Barrow. "Determination of the Heat Transfer Performance of Finned Surfaces Using a Transient Lumped-Capacity Method." In Vehicle Thermal Management Systems Conference. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1993. http://dx.doi.org/10.4271/931134.
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Tagliafico, Luca A., Federico Scarpa, and Maurizio Senarega. "A Compact Dynamic Model for Vapor Compression Refrigerated Systems." In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95221.
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In the paper a simplified dynamic lumped model for the simulation of a refrigerator working according to an inverse cycle between two thermal sources with finite thermal capacity is presented. A variable capacity compressor (VCC) is considered. The model is compact enough to be employed in actual regulation systems, but sufficient to describe all the underlying physical phenomena relevant to the transient response of the refrigerated cell. The dynamic behaviour of the system is simulated taking into account all the heat capacities involved in the heat transfer processes between the system, the refrigerating fluid and the outside. On the other hand the dynamic of the physical phenomena having time constants smaller than a few seconds has been neglected. The validity of this approach is proved by comparing the numerical results with the transient experimental data coming from an instrumented chest-freezer (one kind of small refrigerator often used in household and super-market applications).
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Tso, C. Y., S. C. Fu, and Christopher Y. H. Chao. "Modeling a Novel Composite Adsorbent Based Adsorption Chiller Driven by Solar Energy." In ASME 2013 7th International Conference on Energy Sustainability collocated with the ASME 2013 Heat Transfer Summer Conference and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/es2013-18037.
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This paper aims to study the performance of a solar-powered adsorption chiller with a novel composite adsorbent material (silica activated carbon/CaCl2) operating during some typical months in Hong Kong. Modeling is established to investigate the cooling performance of this adsorption chiller driven by flat-type solar collectors with three different configurations of glaze: 1) single glazed cover; 2) double glazed cover and 3) transparent insulation material (TIM) cover. The simulation results show that the higher the solar collector temperature is, the better the coefficient of performance (COP) and the specific cooling power (SCP) of the adsorption chiller are. It is suggested to select a double glazed collector with a small value of the lumped capacitance for this adsorption chiller. Seasonal effects are discussed in which the solar COP achieves its highest value during autumn. However, the cooling capacities in spring, summer and autumn are similar. All in all, this newly developed composite material as adsorbent used in the adsorption chiller could achieve a mean solar COP of 0.36 and SCP of 94W/kg on a typical summer day of operation.
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Cortés, C., A. Campo, and L. Correas. "A Lumped-Parameter Method for the Computation of the Temperature of Hot Combustion Gases Flowing Inside Chimneys." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0999.
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Abstract This paper addresses the practical calculation of the thermal performance of industrial chimneys by means of recent results in forced convection heat transfer. The temperature decay of the combustion gases is a result of heat transfer processes involving both internal forced convection and external heat transfer to the surroundings, and the analysis of the problem is scarcely treated in the energy- and environmental-related literature. Thermal design and performance estimations of chimneys are therefore based on engineering rules of thumb dictated by experience. The aim of this paper is to introduce rigorous heat transfer results into the subject, but from a framework accessible to design engineers. To this end, a 1-D lumped model of this kind of situations is used (Campo and Lacoa, 1994). Although largely simplified, the model provided adequate estimates of the mean bulk temperatures when compared with those computed with a 2-D distributed model (Campo and Lacoa, 1995), thus satisfying the requirements of simplicity and accuracy for the present purpose. The paper describes the design criteria for thermal calculation of industrial chimneys, the application of the 1-D lumped model through the use of standard heat transfer correlations, and several examples. The sequence of calculations is easy to accomplish and it is explained in such a way that it can be directly employed by engineers engaged in thermal design of tall chimneys.
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Taher, Matt. "ASME PTC-10 and Heat Capacity Relations for Polytropic and Isentropic Compression Process of Real Gas." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63106.
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ASME PTC-10 (reaffirmed 2009) serves as an internationally recognized standard factory acceptance and field performance testing for centrifugal compressors. It provides a test procedure to determine the thermodynamic performance of centrifugal compressors for gases conforming to ideal gas laws and for real gases. ASME PTC-10 defines ideal gases as those, which fall within the limits of table 3.3. The ratio of heat capacities is one of the parameters used to determine the limits of departure from ideal gas in table 3.3. However, ASME PTC-10 does not clearly define whether to use the ideal gas or a real gas method to calculate the ratio of heat capacities. The relationship Ĉp – Ĉv = R, is valid for ideal gases, but not real gases. The validity of Ĉp – Ĉv = R is examined across a typical range of pressures and temperatures and a composition applicable to the natural gas industry. Isentropic processes of ideal gases are accurately described with a simple relationship with the ratio of heat capacities. However, for real gases, that relationship is not valid and a more complex relationship is required for similar accuracy. Thermodynamic relationships used in calculating isentropic and polytropic exponents are summarized. Limitations for real and ideal gas calculation methods are described. The deviations of real gas isentropic and polytropic volume and temperature exponents from ideal gas calculation methods are presented.