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Journal articles on the topic 'Lumped heat capacities method'

Author: Grafiati

Published: 30 May 2022

Last updated: 31 May 2022

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1

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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2

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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3

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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4

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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5

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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6

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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7

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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8

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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9

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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10

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.

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11

Li, Xin Jun. "The Numerical Analysis of Spiral Heat Exchanger." Advanced Materials Research 860-863 (December 2013): 1474–77. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.1474.

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The lumped parameter method was used to establish a mathematical model for the spiral heat exchanger with complex structures and specific heat transfer. By implementing the finite difference method, the differential equation was discretized, and then the steady temperature field of the spiral heat exchanger and the dynamic response of temperature can be obtained under boundary conditions and initial conditions. And the essential correctness and measurement accuracy of the model was proved by fluent. The results show that this model can simulate the temperature field and the dynamic response of it well.

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12

Yi, Duo, and Min Zhang. "Heat flux investigations during flame thermal spray process using the lumped capacitance method." Applied Thermal Engineering 123 (August 2017): 554–61. http://dx.doi.org/10.1016/j.applthermaleng.2017.05.143.

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13

Kobasko, Nikolai. "STUDY OF DIFFERENCES BETWEEN REAL AND EFFECTIVE HEAT TRANSFER COEFFICIENTS TO PROVIDE CORRECT DATA ON TEMPERATURE FIELD CALCULATIONS AND COMPUTER SIMULATIONS DURING HARDENING OF STEEL." EUREKA: Physics and Engineering 3 (May 31, 2018): 42–51. http://dx.doi.org/10.21303/2461-4262.2018.00646.

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The paper analyses contemporary methods and probes for testing liquid media used as a quenchant in heat treating industry. It is shown that lumped-heat-capacity method, often used for testing liquid media, produces big errors during transient nucleate boiling processes due to incorrect calculation condition caused by use effective heat transfer coefficient (HTC). The effective heat transfer coefficients (HTCs), utilized for this purpose, are almost seven times less as compared with real HTCs that results in incorrect calculation the value of Bi. Instead of lumped-heat -capacity method, a general cooling rate equation is proposed for HTC calculation. It is underlined that effective HTCs can be used only for approximate core cooling rate and core cooling time of steel parts calculations. For investigation cooling capacity of liquid quenchants, including initial heat flux densities, HTCs and critical heat flux densities, high developed technique of solving inverse problem should be used based on accurate experimental data generated by testing liquid media with the Liscic/Petrofer probe or other similar technique.

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14

Silva, V. S., J. M. P. Q. Delgado, W. M. P. Barbosa de Lima, and A. G. Barbosa de Lima. "Heat and Mass Transfer in Holed Ceramic Material Using Lumped Model." Diffusion Foundations 7 (June 2016): 30–52. http://dx.doi.org/10.4028/www.scientific.net/df.7.30.

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The drying is a thermodynamic process of simultaneous heat transfer and moisture removal of a porous material. Clay products when exposed to drying without control can suffer cracks and deformations, reducing its quality post-drying. Thus, this work aims to study the holed solid drying with arbitrary shape using the global capacitance method. Application has been made for the drying of clay products. The analytical solution of the governing equations was made using the method of separation of variables.Kinetic results for mass loss and heating of the material are presented and analyzed. It was observed that the moisture loss process occurs at a lower speed than the heating of the ceramic material because its thermal diffusivity is greater than the mass diffusivity and that the area/volume relationshipstrongly affects the phenomena of heat and mass transport.

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15

MEHMETOGLU, TURAL. "AN ANALYTICAL TECHNIQUE FOR EVALUATING HEAT CAPACITY OF GeS, GeSe, GeTe AND SnS SEMICONDUCTORS USING EINSTEIN-DEBYE APPROXIMATION." Journal of Science and Arts 21, no. 3 (September 30, 2021): 857–62. http://dx.doi.org/10.46939/j.sci.arts-21.3-c04.

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A new analytical method for the evaluation of heat capacities of semiconductors (GeS, GeSe, GeTe, and SnS) has been proposed using the Einstein-Debye approximation. These formulae differ from the Debye model representations and they involve a combination of the Einstein and Debye approximations. The proposed method allows developing an increasing accuracy for the determination of the temperature dependent heat capacities of semiconductors GeS, GeSe, GeTe and SnS. The approach suggested in this study for calculation of heat capacities is very well suitable to determine other thermodynamical properties of materials. The temperature dependence of heat capacities of GeS, GeSe, GeTe and SnS semiconductors has been evaluated and shows a good agreement with literature at different temperature ranges.

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16

Saeed, Umer, and Mujeeb ur Rehman. "Assessment of Haar Wavelet-Quasilinearization Technique in Heat Convection-Radiation Equations." Applied Computational Intelligence and Soft Computing 2014 (2014): 1–5. http://dx.doi.org/10.1155/2014/454231.

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We showed that solutions by the Haar wavelet-quasilinearization technique for the two problems, namely, (i) temperature distribution equation in lumped system of combined convection-radiation in a slab made of materials with variable thermal conductivity and (ii) cooling of a lumped system by combined convection and radiation are strongly reliable and also more accurate than the other numerical methods and are in good agreement with exact solution. According to the Haar wavelet-quasilinearization technique, we convert the nonlinear heat transfer equation to linear discretized equation with the help of quasilinearization technique and apply the Haar wavelet method at each iteration of quasilinearization technique to get the solution. The main aim of present work is to show the reliability of the Haar wavelet-quasilinearization technique for heat transfer equations.

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17

Xu, Qiyue, Jiong Ding, Suijun Yang, and Shuliang Ye. "Measurement and calculation method of changing heat capacities during the reaction." Thermochimica Acta 675 (May 2019): 55–62. http://dx.doi.org/10.1016/j.tca.2019.03.004.

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18

Vassiliev, V. P., Weiping Gong, A. F. Taldrik, and S. A. Kulinich. "Method of the correlative optimization of heat capacities of isostructural compounds." Journal of Alloys and Compounds 552 (March 2013): 248–54. http://dx.doi.org/10.1016/j.jallcom.2012.10.075.

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19

Chavelas, Eneas A., Rafael A. Zubillaga, Nancy O. Pulido, and Enrique García-Hernández. "Multithermal titration calorimetry: A rapid method to determine binding heat capacities." Biophysical Chemistry 120, no. 1 (March 2006): 10–14. http://dx.doi.org/10.1016/j.bpc.2005.09.022.

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20

Oliveira, Pedro N., Elza M. M. Fonseca, Raul D. S. G. Campilho, and Paulo A. G. Piloto. "Analytical Equations Applied to the Study of Steel Profiles under Fire According to Different Nominal Temperature-Time Curves." Mathematical and Computational Applications 26, no. 2 (June 18, 2021): 48. http://dx.doi.org/10.3390/mca26020048.

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Some analytical methods are available for temperature evaluation in solid bodies. These methods can be used due to their simplicity and good results. The main goal of this work is to present the temperature calculation in different cross-sections of structural hot-rolled steel profiles (IPE, HEM, L, and UAP) using the lumped capacitance method and the simplified equation from Eurocode 3. The basis of the lumped capacitance method is that the temperature of the solid body is uniform at any given time instant during a heat transient process. The profiles were studied, subjected to the fire action according to the nominal temperature–time curves (standard temperature-time curve ISO 834, external fire curve, and hydrocarbon fire curve). The obtained results allow verifying the agreement between the two methodologies and the influence in the temperature field due to the use of different nominal fire curves. This finding enables us to conclude that the lumped capacitance method is accurate and could be easily applied.

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21

Sun, Zehui, Guoli Li, Zhe Qian, Weifei Li, and Jian Jing. "Lumped-Capacity Method for Easy Estimation of Interfacial Heat Transfer Coefficients in Die Casting." International Journal of Materials, Mechanics and Manufacturing 8, no. 3 (June 2020): 104–8. http://dx.doi.org/10.18178/ijmmm.2020.8.3.492.

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22

Keshavarz, P., and M. Taheri. "An improved lumped analysis for transient heat conduction by using the polynomial approximation method." Heat and Mass Transfer 43, no. 11 (November 11, 2006): 1151–56. http://dx.doi.org/10.1007/s00231-006-0200-0.

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23

Chatzipantelidis, Panagiotis, Zoltan Horváth, and Vidar Thomée. "On Preservation of Positivity in Some Finite Element Methods for the Heat Equation." Computational Methods in Applied Mathematics 15, no. 4 (October 1, 2015): 417–37. http://dx.doi.org/10.1515/cmam-2015-0018.

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AbstractWe consider the initial boundary value problem for the homogeneous heat equation, with homogeneous Dirichlet boundary conditions. By the maximum principle the solution is nonnegative for positive time if the initial data are nonnegative. We complement in a number of ways earlier studies of the possible extension of this fact to spatially semidiscrete and fully discrete piecewise linear finite element discretizations, based on the standard Galerkin method, the lumped mass method, and the finite volume element method. We also provide numerical examples that illustrate our findings.

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24

CHOI, JONG WON, IL HWAN LEE, and MIN SOO KIM. "ANALYTICAL STUDY ON THE HEATING PERFORMANCE OF A MULTI-TYPE HEAT PUMP SYSTEM WITH n-INDOOR UNITS." International Journal of Air-Conditioning and Refrigeration 19, no. 01 (March 2011): 25–36. http://dx.doi.org/10.1142/s2010132511000375.

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This paper presents the steady-state heating performance of a multi-type heat pump system. The compressor and expansion valves are described by a lumped parameter model for its rapid and prompt response to the disturbances compared to those of the heat exchangers. Fully distributed model (or spatially dependent model) is used for the evaporator and condenser since the lumped method does not guarantee enough accuracy in estimating the performance of heat exchangers with phase change. Most researches on the numerical simulation in heat pump system focuses on the precise modeling for the steady or transient states while few researches on the simulations consider the relationships among several indoor units, expansion valve openings and compressor speed in multi-type heat pump system. In this study, the heating performance of a multi-type heat pump system using R410A with three indoor units is simulated for the investigation of system characteristics and the simulation results are verified for several experimental conditions. Finally, the simulation technique is extended to the system with n-indoor units.

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25

Danes, Florin, and Bertrand Garnier. "Improved Differential Scanning Calorimetric Measurement Method for the Small Reaction Heat Capacities." Rubber Chemistry and Technology 78, no. 1 (March 1, 2005): 114–29. http://dx.doi.org/10.5254/1.3547865.

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Abstract Heat capacities of the different rubber states are important features for the engineering calculation of rubber manufacturing. The heat capacity change Δcp due to the vulcanization process has been measured with a differential scanning calorimeter (DSC) only after reducing the standard error of a Δcp measurement under 5 J kg−1 K−1. For this purpose, we used sealed (up to 150 bar) DSC sample pans which avoid mass losses. Heat capacities before and after vulcanization were measured on the same samples using special DSC procedure and reversible thermal effects due to rubber components were corrected. For natural rubber vulcanized with sulfur at t=40…110 °C we found, in J/(kg S)−1 K−1: Δcp=76+11 t, whatever the temperature vulcanization between 100 and 160 °C.

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26

Coniglio, L., and J. L. Daridon. "A group contribution method for estimating ideal gas heat capacities of hydrocarbons." Fluid Phase Equilibria 139, no. 1-2 (December 1997): 15–35. http://dx.doi.org/10.1016/s0378-3812(97)00143-x.

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27

Qiu, Liyan, and Mary Anne White. "The Constituent Additivity Method to Estimate Heat Capacities of Complex Inorganic Solids." Journal of Chemical Education 78, no. 8 (August 2001): 1076. http://dx.doi.org/10.1021/ed078p1076.

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28

Jat, Ram Avtar, S. C. Parida, K. Krishnan, N. S. Anand, S. G. Sawant, Renu Agarwal, Ziley Singh, S. K. Aggarwal, and V. Venugopal. "Heat capacities of polycrystalline nLiH and nLiD by differential scanning calorimetric method." Journal of Alloys and Compounds 505, no. 1 (August 2010): 309–14. http://dx.doi.org/10.1016/j.jallcom.2010.06.059.

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29

Peng, S., and G. Grimvall. "A method to estimate entropies and heat capacities applied to alkali oxides." International Journal of Thermophysics 15, no. 5 (September 1994): 973–81. http://dx.doi.org/10.1007/bf01447107.

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30

Węglarz, Katarzyna, Dawid Taler, Magdalena Jaremkiewicz, Jan Taler, and Mateusz Marcinkowski. "Analytical-numerical method for calculating cross-flow tube heat exchangers considering temperature-dependent fluid heat capacities." International Journal of Heat and Mass Transfer 183 (February 2022): 122202. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2021.122202.

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31

von Wolfersdorf, J., R. Hoecker, and C. Hirsch. "A Data Reduction Procedure for Transient Heat Transfer Measurements in Long Internal Cooling Channels." Journal of Heat Transfer 120, no. 2 (May 1, 1998): 314–21. http://dx.doi.org/10.1115/1.2824248.

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The effect of streamwise fluid temperature variation on the local heat transfer coefficient measurements in transient heat transfer tests in long channels is addressed. Previous methods are shown to result in considerable errors. A simplified model is proposed to characterize the local fluid temperature, which drives the heat transfer. With it, analytical solutions for the local wall temperature history are derived, which involve two unknowns, the local heat transfer coefficient and a lumped upstream heat transfer parameter. Using these solutions in the data reduction, these two parameters are determined from surface temperature measurements. Numerical experiments that simulate the physical experiment show the applicability and robustness of the proposed method. The method is finally demonstrated experimentally by investigating heat transfer in a smooth, square duct.

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32

Carvalho, Carolina, Esdras Carvalho, and Mauro Ravagnani. "Combined neural networks and predictive control for heat exchanger networks operation." Chemical Industry and Chemical Engineering Quarterly 26, no. 2 (2020): 125–34. http://dx.doi.org/10.2298/ciceq190530031c.

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Optimal operation of integrated heat exchangers is a challenging task in the field of process control due to system nonlinearities, disturbances and adequate model identification. This paper describes the design of an advanced neural network predictive control (NNPC) applied to a heat exchanger network. A case study with two hot and one cold streams, through three counter-current heat exchangers is used to test the proposed strategy. A lumped dynamic model is built based on the concept of multi-cells topology (mixed tanks), where the hot and cold cells are connected by a wall element throughout the heat exchanger length. Each cell is assumed perfectly mixed and all physical properties are constant. A distributed behavior is achieved by increasing the number of cells. The main assumptions of the lumped model are constant temperature in each cell, heat exchanger volume and area equally distributed between cells and negligible heat loss to the environment. The predictive controller relies on a neural-based model of the plant that is used to identify the system and to predict future performance over a predefined horizon. Results were compared to a traditional controller, and the control performance was improved when compared to the Ziegler-Nichols tuning method.

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33

Naef, Rudolf. "Calculation of the Isobaric Heat Capacities of the Liquid and Solid Phase of Organic Compounds at and around 298.15 K Based on Their “True” Molecular Volume." Molecules 24, no. 8 (April 24, 2019): 1626. http://dx.doi.org/10.3390/molecules24081626.

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A universally applicable method for the prediction of the isobaric heat capacities of the liquid and solid phase of molecules at 298.15 K is presented, derived from their “true” volume. The molecules’ “true” volume in A3 is calculated on the basis of their geometry-optimized structure and the Van-der-Waals radii of their constituting atoms by means of a fast numerical algorithm. Good linear correlations of the “true” volume of a large number of compounds encompassing all classes and sizes with their experimental liquid and solid heat capacities over a large range have been found, although noticeably distorted by intermolecular hydrogen-bond effects. To account for these effects, the total amount of 1303 compounds with known experimental liquid heat capacities has been subdivided into three subsets consisting of 1102 hydroxy-group-free compounds, 164 monoalcohols/monoacids, and 36 polyalcohols/polyacids. The standard deviations for Cp(liq,298) were 20.7 J/mol/K for the OH-free compunds, 22.91 J/mol/K for the monoalcohols/monoacids and 16.03 J/mol/K for the polyols/polyacids. Analogously, 797 compounds with known solid heat capacities have been separated into a subset of 555 OH-free compounds, 123 monoalcohols/monoacids and 119 polyols/polyacids. The standard deviations for Cp(sol,298) were calculated to 23.14 J/mol/K for the first, 21.62 J/mol/K for the second, and 19.75 J/mol/K for the last subset. A discussion of structural and intermolecular effects influencing the heat capacities as well as of some special classes, in particular hydrocarbons, ionic liquids, siloxanes and metallocenes, has been given. In addition, the present method has successfully been extended to enable the prediction of the temperature dependence of the solid and liquid heat capacities in the range between 250 and 350 K.

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34

Lee, Shin Pyo. "Heat Transfer Characteristics of Nanofluids by Applying the Lumped Capacitance Method on a Heated Metal Sphere." Transactions of the Korean Society of Mechanical Engineers - B 44, no. 10 (October 31, 2020): 611–18. http://dx.doi.org/10.3795/ksme-b.2020.44.10.611.

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35

Mohamed, I. O. "An inverse lumped capacitance method for determination of heat transfer coefficients for industrial air blast chillers." Food Research International 41, no. 4 (2008): 404–10. http://dx.doi.org/10.1016/j.foodres.2008.01.005.

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36

Cui, Guo Min, Jin Yang Wang, Tao Jiang, and Xiang Bai Hu. "Transfer Behavior of Heat Exchanger." Advanced Materials Research 233-235 (May 2011): 1281–87. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.1281.

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This study deals with the transient response of heat exchanger which is approximated to the first-order system with delay. This function is of simple form and easy to be applied to design the practical controllers. The parameters such as gain K, time constant T and delay time are derived in this paper. On the basis of using the first-order system as the transfer function for a heat exchanger, more accurate models are built to derive the parameters K, T and respectively, which are constructed with a lumped parameter approach. Unlike a number of recent analyses K is obtained by using arithmetic mean temperature difference, log mean temperature difference has been employed instead, which minimized the error; time constant T is obtained by deriving the time constant of baffle; delay time is estimated by flow rate. The result shows that this method to study the dynamic characteristics of heat exchanger is easier, more accurate.

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Svoboda, Václav, Kornelia Gottmanová, Vladimír Hynek, and Bohumír Koutek. "Heat Capacities of Some Alkyl Acetates at 295-323 K." Collection of Czechoslovak Chemical Communications 62, no. 10 (1997): 1527–32. http://dx.doi.org/10.1135/cccc19971527.

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Molar heat capacities Cp,m at constant atmospheric pressure have been determined with a typical uncertainty of about 0.3% for eight liquid alkyl acetates H(CH2)nOCOCH3 (n = 6-12, 14), over the temperature range 295-323 K. The Cp,m values were found to be a linear function of temperature. A comparison of experimental data with those predicted by the group additivity method demonstrated a rather limited capability of the additivity scheme to predict correctly the Cp,m values for higher (n > 10) homologues in the series.

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Shawki, E. E., S. N. Flengas, and D. R. Sadoway. "Drop calorimetry of the compounds NbCl5, TaCl5, RbNbCl6, CsNbCl6, RbTaCl6, and CsTaCl6." Canadian Journal of Chemistry 67, no. 7 (July 1, 1989): 1193–99. http://dx.doi.org/10.1139/v89-180.

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Enthalpy contents for NbCl5, TaCl5, RbNbCl6, CsNbCl6, RbTaCl6, and CsTaCl6 were measured as functions of temperature using a high temperature aluminum block drop calorimeter. It was found that the solid compounds RbNbCl6, CsNbCl6, RbTaCl6, and CsTaCl6 undergo allotropie solid–solid transformations and the enthalpies and entropies associated with these phase changes, as well as from fusion, have been evaluated.Molar heat capacities for the systems investigated are reported as linear functions of temperature.The molar heat capacities for solid and molten NbCl5 or TaCl5 were used together with available vapour pressure data to express enthalpies and free energies of vaporization for these compounds as functions of temperature through the third law calculation method. Keywords: calorimetry, heat capacities, transition enthalpies, niobium compounds, tantalum compounds.

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Chen, Chu, Zhi Guo Lu, and Jian Ping Lin. "Temperature Variation History Prediction of Fully-Closed Adhesive Joint in Curing Process." Applied Mechanics and Materials 44-47 (December 2010): 394–99. http://dx.doi.org/10.4028/www.scientific.net/amm.44-47.394.

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To describe the heat transfer of fully-closed adhesive joint in curing process, adhesive joint, enclosure for closing joints and its inner air are simplified as a multi-lumped-heat-capacity system neglecting the heat from adhesive chemical reaction. Based on heat transfer theory, a temperature prediction model of fully-closed joint was proposed. Combining experimental temperature history of the joint with finite difference method, the combined heat transfer coefficients of adhesive under different curing temperatures were obtained according to Newton's heat transfer formula. And the model was validated by the experiments. The results revealed that the model can be used to predict the temperature of fully-closed adhesive joint in curing process.

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Liu, Zhenliang, and Suchao Li. "Development of an ANN-Based Lumped Plasticity Model of RC Columns Using Historical Pseudo-Static Cyclic Test Data." Applied Sciences 9, no. 20 (October 11, 2019): 4263. http://dx.doi.org/10.3390/app9204263.

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This study explores the possibility of using an ANN-based model for the rapid numerical simulation and seismic performance prediction of reinforced concrete (RC) columns. The artificial neural network (ANN) method is implemented to model the relationship between the input features of RC columns and the critical parameters of the commonly used lumped plasticity (LP) model: The strength and the yielding, capping and ultimate deformation capacity. Cyclic test data of 1163 column specimens obtained from the PEER and NEEShub database and other sources are collected and divided into the training set, test set and validation set for the ANN model. The effectiveness of the proposed ANN model is validated by comparing it with existing explicit formulas and experimental results. Results indicated that the developed model can effectively predict the strength and deformation capacities of RC columns. Furthermore, the response of two RC frame structures under static force and strong ground motion were simulated by the ANN-based, bi-linear and tri-linear LP model method. The good agreement between the proposed model and test results validated that the ANN-based method can provide sufficiently accurate model parameters for modeling the seismic response of RC columns using the LP model.

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Abramov, D. O., T. N. Shvetsova, and D. I. Nazarenko. "Development of mathematical models of test systems as objects with lumped parameters." Proceedings of the Voronezh State University of Engineering Technologies 82, no. 2 (September 18, 2020): 42–48. http://dx.doi.org/10.20914/2310-1202-2020-2-42-48.

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This paper deals with the problem of constructing a mathematical model for studying the thermal regime of a test system at the design stage. The test system is presented as a complex chemical-technological system, which includes a large number of elements, components and devices, characterized by a variety of functional and thermal relationships. The block-hierarchical method is used for designing the system under consideration. A thermal block diagram of the system has been developed, which includes six interconnected blocks: a thermostat; coolant; heat exchanger; cubic apparatus, medium in apparatus and environment. A mathematical model has been created to estimate the average temperatures in the system, which allows you to calculate the integral characteristics of heat exchange processes (the values average intake temperatures and the values surface average temperatures, average heat fluxes) taking into account the interaction between all blocks of the system. It was assumed that each element of the system under consideration can have thermal connections, both with the environment and with other elements of the system. It was assumed that the element can dissipate its own power, as well as the power supplied for thermal control of the element, which depends on its temperature. The calculation of the temperature fields of bodies and flows of heat carriers was carried out on the basis of models with concentrated parameters, with the assumption that there are no temperature gradients in all directions. The model is represented by a system of ordinary differential equations. The dependences of temperature on time change for two non-stationary modes of a thermostatic system consisting of a hollow device of cubic shape with a volume 3 m3 filled with gas and equipped with a heat exchanger are shown. The developed mathematical model allows solving the problems of temperature stabilization of the test system.

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Uy, Robert Frederik, Qiaozi Miao, and Chenghao Yuan. "Bimetallic ammeter: a novel method of current measurement." Emergent Scientist 4 (2020): 2. http://dx.doi.org/10.1051/emsci/2020001.

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An electric current flowing through a bimetallic coil heats it up, and due to thermal expansion, the coil either unwinds or winds depending on the direction of net heat transfer and the specific heat capacities of the metals used. This means that by relating a certain measure of its mechanical displacement with current, the bimetallic coil can be used as an ammeter. Thus, a mathematical model relating the current to the time taken by the bimetallic coil to unwind a fixed displacement was developed and verified through experiments, which show a good agreement between theoretical and experimental values.

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Hakin, Andrew W., Susan A. M. Mudrack, and Colin L. Beswick. "The volumetric and thermochemical properties of L-ascorbic acid in water at 288.15, 298.15, and 308.15 K." Canadian Journal of Chemistry 71, no. 7 (July 1, 1993): 925–29. http://dx.doi.org/10.1139/v93-123.

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Measurements have been made at 288.15, 298.15, and 308.15 K with a flow microcalorimeter and densimeter to obtain heat capacities and densities for L-ascorbic acid and sodium chloride in water. These data are reported in terms of apparent molar volumes [Formula: see text] and apparent molar heat capacities [Formula: see text] The volume of ionization (ΔV0) and heat capacity of ionization (ΔCP0) for the acid at 298.15 K have been calculated using a method that does not require volumetric and thermochemical data for the sodium salts of the acid. Details of our methodology are presented.

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Dimova, Stefka N., and Daniela P. Vasileva. "LUMPED-MASS FINITE-ELEMENT METHOD WITH INTERPOLATION OF THE NONLINEAR COEFFICIENTS FOR A QUASILINEAR HEAT TRANSFER EQUATION." Numerical Heat Transfer, Part B: Fundamentals 28, no. 2 (September 1995): 199–215. http://dx.doi.org/10.1080/10407799508928830.

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Bernardes, Carlos E. S., Luís M. N. B. F. Santos, and Manuel E. Minas da Piedade. "A new calorimetric system to measure heat capacities of solids by the drop method." Measurement Science and Technology 17, no. 6 (May 2, 2006): 1405–8. http://dx.doi.org/10.1088/0957-0233/17/6/018.

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46

Zhang, Xiaoxuan, Reinhardt Klein, Anantharaman Subbaraman, Sergei Chumakov, Xiaobai Li, Jake Christensen, Christian Linder, and Sun Ung Kim. "Evaluation of convective heat transfer coefficient and specific heat capacity of a lithium-ion battery using infrared camera and lumped capacitance method." Journal of Power Sources 412 (February 2019): 552–58. http://dx.doi.org/10.1016/j.jpowsour.2018.11.064.

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47

Xu, Zhe Zhu, Qi Zhang, and Sung Ki Lyu. "Improvement of Positioning Error on a Ball Screw by Cooling System." Applied Mechanics and Materials 86 (August 2011): 752–55. http://dx.doi.org/10.4028/www.scientific.net/amm.86.752.

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A high speed ball screw system generates more heat naturally and resultant more thermal expansion, which adversely affects the accuracy of positioning. Therefore, an air cooling system was set in ball screw shaft in this paper to dominate the thermal error and achieve temperature equilibrium faster. In order to estimate the thermal error of ball screw system and effectiveness of air cooling system, thermal behavior models of finite element method and modified lumped capacitance method were developed separately which includes the heat generation power of the main heat source of the ball screw system and other boundary conditions. The completed models were used to simulate the temperature distribution, thermal deformation and air cooling performance. Compared with experiments, it is shown that these methods can well predict the air cooling performance.

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Benhamida, Mohammed Ali, Hamza Ennassiri, and Yacine Amara. "Reluctance network lumped mechanical & thermal models for the modeling and predesign of concentrated flux synchronous machine." Open Physics 16, no. 1 (November 23, 2018): 692–705. http://dx.doi.org/10.1515/phys-2018-0088.

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Abstract The aim of this paper is the multi-physical modeling of synchronous permanent magnet machines, dedicated to hybrid electrical vehicles application, using reluctance network lumped mechanical and thermal models. The modeling approaches are presented and validated by comparing the obtained results to those of finite element method with a close look to the airgap modeling and the consideration of soft magnetic materials non-linearity in the electromagnetic modeling. As well as a close look also on the conduction and convection heat coefficients for the machine different regions in the thermal modeling. Finally a focus on the mass, damping and stiffness matrix computation in lumped mechanical modeling taking into account the temperature influence on the materials mechanical properties. In addition a simplified rotating electrical machine is described and multiple coupled analysis were done in order to derive the structure magneto-vibroacoustic performances.

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Jovanovic, Jovan, Andjela Knezevic-Stevanovic, and Dusan Grozdanic. "Prediction of high pressure liquid heat capacities of organic compounds by a group contribution method." Journal of the Serbian Chemical Society 76, no. 3 (2011): 417–23. http://dx.doi.org/10.2298/jsc100511031j.

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A new method for estimating high pressure liquid heat capacities based on molecular structure and group contribution is proposed. A common set of structural groups was employed. The method was developed using 67 sets of 43 organic compounds with 3449 experimental heat capacity data. A small number of measured compounds, data points per compound and other comparable methods were observed. This is a simple first-order approximation with acceptable accuracy of 2.548%.

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Wilson, William R. D. "A Framework for Thermohydrodynamic Lubrication Analysis." Journal of Tribology 120, no. 2 (April 1, 1998): 399–405. http://dx.doi.org/10.1115/1.2834440.

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Thermohydrodynamic lubrication is complicated by the multiplicity of heat transfer paths from the site of dissipation to the surroundings. This has impeded a general understanding of thermohydrodynamic phenomena. The method of lumped variables is applied to a simple slider bearing (as an example) to explore thermohydrodynamic lubrication. This approach leads to a better understanding of the interplay between the different modes of heat transfer and the influence of the associated temperature rises on performance, and how this can be captured by the use of appropriate non-dimensional measures. Such measures also allow the mapping of the problem into a set of regimes characterized by the relative importance of different heat transfer modes.

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