Modeling Transient/Steady-State Convection From Isoflux Vertical Plates

2012 ◽  
Author(s):  
Mehran Ahmadi ◽  
Majid Bahrami
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Analytical Model ◽  
Vertical Plate ◽  
Convection Heat Transfer ◽  
Constant Property ◽  
Nusselt Numbers ◽  
Proposed Model ◽  
Transient And Steady State ◽  
State Average

A new compact analytical model is developed to predict transient heat convection from isoflux vertical plates into a constant property surrounding region. The proposed model is based on a blending of the two asymptotes corresponding to transient diffusion into a half-space and the steady-state convection heat transfer from an isoflux vertical plate. A compact relation for transient and steady-state average Nusselt numbers is proposed. The proposed model is successfully verified with existing experimental data of Goldstein and Eckert. The maximum difference between the proposed compact analytical model and the experimental data is less than 6%.

Two-dimensional steady-state thermal analytical model of permanent-magnet synchronous machines operating in generator mode

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zakarya Djelloul Khedda ◽  
Kamel Boughrara ◽  
Frédéric Dubas ◽  
Baocheng Guo ◽  
El Hadj Ailam
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Permanent Magnet ◽  
Analytical Model ◽  
Electrical Machines ◽  
Synchronous Machines ◽  
Analytical Prediction ◽  
Two Dimensional ◽  
Content Type ◽  
Proposed Model

Purpose Thermal analysis of electrical machines is usually performed by using numerical methods or lumped parameter thermal networks depending on the desired accuracy. The analytical prediction of temperature distribution based on the formal resolution of thermal partial differential equations (PDEs) by the harmonic modeling technique (or the Fourier method) is uncommon in electrical machines. Therefore, this paper aims to present a two-dimensional (2D) analytical model of steady-state temperature distribution for permanent-magnet (PM) synchronous machines (PMSM) operating in generator mode. Design/methodology/approach The proposed model is based on the multi-layer models with the convolution theorem (i.e. Cauchy’s product theorem) by using complex Fourier’s series and the separation of variables method. This technique takes into the different thermal conductivities of the machine parts. The heat sources are determined by calculating the different power losses in the PMSM with the finite-element method (FEM). Findings To validate the proposed analytical model, the analytical results are compared with those obtained by thermal FEM. The comparisons show good results of the proposed model. Originality/value A new 2D analytical model based on the PDE in steady-state for full prediction of temperature distribution in the PMSM takes into account the heat transfer by conduction, convection and radiation.

scholarly journals A New Dynamic Model to Predict Transient and Steady State PV Temperatures Taking into Account the Environmental Conditions

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 2 ◽  
Author(s):  
Socrates Kaplanis ◽  
Eleni Kaplani
Keyword(s):  
Steady State ◽  
Environmental Conditions ◽  
Solar Irradiance ◽  
Model Performance ◽  
Transient Temperature ◽  
Temperature Profiles ◽  
Time Constants ◽  
Proposed Model ◽  
Pv Cell ◽  
Transient And Steady State

Photovoltaic (PV) cell and module temperature profiles, Tc and Tpv, respectively, developed under solar irradiance were predicted and measured both at transient and steady state conditions. The predicted and measured Tc or Tpv covered both a bare c-Si PV cell, by SOLARTEC, at laboratory conditions using a solar light simulator, as well as various c-Si and pc-Si modules (SM55, Bioenergy 195W, Energy Solutions 125W) operating in field conditions. The time constants, τ, of the Tc and Tpv profiles were determined by the proposed model and calculated using the experimentally obtained profiles for both the bare PV cell and PV modules. For model validation, the predicted steady state and transient temperature profiles were compared with experimental ones and also with those generated from other models. The effect of the ambient temperature, Ta, wind speed, vw, and the solar irradiance, IT, on the model performance, as well as of the mounting geometries, was investigated and incorporated in the prediction model. The predicted temperatures had the best matching to the measured ones in comparison to those from six other models. The model developed is applicable to any geographical site and environmental conditions.

A Study of High-Temperature Heat Pipes With Multiple Heat Sources and Sinks: Part II—Analysis of Continuum Transient and Steady-State Experimental Data With Numerical Predictions

1991 ◽  
Vol 113 (4) ◽  
pp. 1010-1016 ◽  
Author(s):  
A. Faghri ◽  
M. Buchko ◽  
Y. Cao
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Heat Pipe ◽  
Pipe Wall ◽  
Heat Sources ◽  
Maximum Heat ◽  
Sources And Sinks ◽  
Numerical Predictions ◽  
Wick Structure ◽  
Transient And Steady State

The experimental data presented in Part I were analyzed concerning the heat pipe performance characteristics and design. Postexperiment examination of the loosely wrapped screen wick revealed annular gaps both between the wick and the heat pipe wall and between adjacent screen layers, which greatly enhanced the maximum heat capacity of the heat pipe compared to the analytical capillary limit for a tightly wrapped screen wick. A numerical simulation for transient heat pipe performances including the vapor region, wick structure, and the heat pipe wall is given. Numerical results for continuum transient and steady-state operations with multiple heat sources were compared with experimental results and found to be in good agreement.

Laminar Forced Convection Heat Transfer in the Combined Entry Region of Non-Circular Ducts

2004 ◽  
Vol 126 (1) ◽  
pp. 54-61 ◽  
Author(s):  
Y. S. Muzychka ◽  
M. M. Yovanovich
Keyword(s):  
Circular Tube ◽  
Convection Heat Transfer ◽  
Numerical Data ◽  
Asymptotic Results ◽  
Cross Sectional ◽  
Fully Developed Flow ◽  
Nusselt Numbers ◽  
Proposed Model ◽  
Laminar Forced Convection ◽  
Plate Channel

A new model for predicting Nusselt numbers in the combined entrance region of non-circular ducts and channels is developed. This model predicts both local and average Nusselt numbers and is valid for both isothermal and isoflux boundary conditions. The model is developed using the asymptotic results for convection from a flat plate, thermally developing flows in non-circular ducts, and fully developed flow in non-circular ducts. Through the use of a novel characteristic length scale, the square root of cross-sectional area, the effect of duct shape on Nusselt number is minimized. Comparisons are made with several existing models for the circular tube and parallel plate channel and with numerical data for several non-circular ducts. Agreement between the proposed model and numerical data is within ±15percent or better for most duct shapes.

Natural Convective Heat Transfer From an Unconfined or a Confined Heated Surface

2005 ◽  
Author(s):  
L. K. Liu ◽  
T. W. Lin ◽  
M. C. Wu ◽  
C. H. Peng ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Steady State ◽  
Local Nusselt Number ◽  
Average Nusselt Number ◽  
Heated Surface ◽  
Nusselt Numbers ◽  
Extended Surface ◽  
Extended Surfaces ◽  
State Average

A series of experimental investigations with a stringent measurement method on the natural heat transfer from an unconfined or confined smooth and extended surface have been successfully conducted. From the results, the maximum transient-/steady-state local Nusselt number exists in the region near the edge of the heated smooth or extended surface, and the transient-/ steady-state local Nusselt number decreases along the distance from the surface edge toward the surface center. The transient-/steady-state local and average Nusselt number increases with increasing Grs, H/W or Hes/W. The effects of Grs, H/W and Hes/W on the Nus/Nus,o distribution are not significant; and the Nus/Nus,o distribution can be expressed as a generalized bowl-shaped profile, which is independent of Grs, H/W and Hes/W. By the statistical sensitivity analysis of ANOVA F-test, the steady-state average Nusselt number for unconfined/confined smooth or extended surface is significantly affected by either one of Grs, H/W and Hes/W. Among them, Grs has the most significant effect. Four new correlations of steady-state average Nusselt number in terms of relevant influencing parameters for unconfined/ confined smooth or extended surfaces are proposed, respectively. Furthermore, two normalized steady-state average Nusselt numbers for confined smooth or extended surfaces are proposed, respectively. As compared with the steady-state average Nusselt numbers for unconfined/confined smooth surface, the steady-state heat transfer enhancement for unconfined/confined extended surface can be achieved between 93.99% and 254.65%.

TRANSIENT AND STEADY STATE PROPERTIES OF THE INVERSE FARADAY EFFECT — SIMULATION AND THEORY

1991 ◽  
Vol 05 (22) ◽  
pp. 1533-1542 ◽  
Author(s):  
M.W. EVANS
Keyword(s):  
Experimental Data ◽  
Computer Simulation ◽  
Steady State ◽  
Laser Pulse ◽  
Kerr Effect ◽  
Faraday Effect ◽  
Inverse Faraday Effect ◽  
Visible Frequency ◽  
Frequency Laser ◽  
Transient And Steady State

A computer simulation of the inverse Faraday effect in a chiral and achiral ensemble has shown the presence of dynamic magnetisation and second order orientational rise/fall transients due to the conjugate product of a circularly polarised visible frequency laser pulse. Neither effect is known analytically, and the simulated transients are potentially directly comparable with experimental data using modified Kerr effect apparatus.

Nonlinear dynamic analysis of periodic ferroresonance based on a novel hysteresis approach

2016 ◽  
Vol 30 (09) ◽  
pp. 1650164 ◽  
Author(s):  
Mi Zou ◽  
Wen-Xia Sima ◽  
Ming Yang ◽  
Qing Yang ◽  
Licheng Li ◽  
...  
Keyword(s):  
Steady State ◽  
Power Systems ◽  
Power Transformer ◽  
Nonlinear Dynamic Analysis ◽  
Stability And Convergence ◽  
Iron Core ◽  
Voltage Transformer ◽  
Proposed Model ◽  
Transformer Model ◽  
Transient And Steady State

Ferroresonance is one of the most harmful and longest known power quality disturbances in the history of AC power systems. The ability of predicting transient and steady-state ferroresonance simulations mainly depends on the accuracy of the power transformer model. Most existing voltage transformer models apply single-valued nonlinear functions to represent the core nonlinearities. This study, based on our previous work, proposes a newly improved and accurate transformer iron core hysteresis model for ferroresonance simulation by extension of the classical arctangent model. To verify the proposed model’s accuracy and superiority, three different ferroresonant voltage and current waveform simulations were performed using both the proposed model and renowned EMTP Type-96 model under the same system parameters. In addition, simulation results were compared with the corresponding experimental measurements. The results indicate that the proposed model is easily implemented using numerical modeling method with good stability and convergence, and is sufficiently accurate for both transient and steady-state periodic ferroresonance analysis.

Sign in / Sign up

Export Citation Format

Share Document