scholarly journals One-parameter model of sterilisation process. Heating and cooling period

2012 ◽  
Vol 52 (No. 3) ◽  
pp. 97-106
Author(s):  
M. Loučka ◽  
P. Veselý ◽  
F. Jaroš ◽  
J. Pavlík
Keyword(s):  
Heat Transfer ◽  
Transfer Model ◽  
Cooling Period ◽  
First Order ◽  
Heating And Cooling ◽  
Wide Range ◽  
Process Heating ◽  
The Common ◽  
The One ◽  
Computing Method

The article deals with the simplification of the heat transfer model for food sterilisation in cans and jars. The one-parameter model was derived and identification procedures of its parameters were examined. It is shown that the concept of the first order dynamics satisfies the technological purposes but the common method of the least squares is not suitable for the calculation of model constants. A new computing method is presented and compared with statistically evaluated experiments with wide range of stuffs and packages.

Modified methodology of computation of admissible continuous currents of plain conductors of overhead transmission lines and catenaries

2021 ◽  
Vol 2 (2) ◽  
pp. 36-43
Author(s):  
Evgeniy P. FIGURNOV ◽  
◽  
Yury I. ZHARKOV ◽  
Valeriy I. KHARCHEVNIKOV ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Transmission Lines ◽  
Power Transmission ◽  
Convection Heat Transfer ◽  
Heating And Cooling ◽  
Continuous Current ◽  
The Subject ◽  
The Common ◽  
Overhead Power Transmission Line

Methodology provided summarizes published, original and foreign theoretic and experimental data on the subject of heating and cooling of standard and shaped conductors of overhead power transmission line and uses those of them which are most affected to fundamental heat-transfer laws. Computation surface area of standard and shaped wire formulas are given. The common formula of convection heat transfer coefficient is provided, based on wind speed and direction, concerning antiicing mode. Parameters of this formula do not coincide with those existing, as they are based on experimental data on standard and shaped conductors but not on round tubes. Formula of computation of heat transfer power under the influence of solar radiation is given. Summarized formula of admissible continuous current computation is given, all the components have detailed description in the article.

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part II—Transition and Turbulent Flows

1993 ◽  
Vol 115 (4) ◽  
pp. 890-896 ◽  
Author(s):  
R. M. Manglik ◽  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flows ◽  
Published Data ◽  
Twisted Tape ◽  
Heating And Cooling ◽  
Twisted Tapes ◽  
Family Of Curves ◽  
Wide Range ◽  
Limiting Case

Thermal-hydraulic design correlations are developed to predict isothermal f and Nu for in-tube, turbulent flows with twisted-tape inserts. Experimental data taken for water and ethylene glycol, with y = 3.0, 4.5, and 6.0, are analyzed, and various mechanisms attributed to twisted tapes are identified. Tube blockage and tape-induced vortex mixing are the dominant phenomena that result in increased heat transfer and pressure drop; for loose- to snug-fitting tapes, the fin effects are insignificant. The limiting case of a straight tape insert correlates with the hydraulic-diameter-based smooth tube equation. Tape twist effects are thus isolated by normalizing the data with the asymptotic predictions for y = ∞, and the swirl effects are found to correlate with Re and l/y. The validity of the final correlations is verified by comparing the predictions with previously published data, which include both gases and liquids, under heating and cooling conditions and a wide range of tape geometries, thereby establishing a very generalized applicability. Finally, correlations for laminar (presented in the companion Part I paper) and turbulent flows are combined into single, continuous equations. For isothermal f, the correlation describes most of the available data for laminar-transition-turbulent flows within ±10 percent. For Nu, however, a family of curves is needed due to the nonunique nature of laminar-turbulent transition.

Parallel Heat Transfer Model of a Panel with Phase Change Material for Thermal Storage Applications Computed on Graphics Processing Units

2014 ◽  
Vol 1077 ◽  
pp. 118-123 ◽  
Author(s):  
Lubomír Klimeš ◽  
Pavel Charvát ◽  
Milan Ostrý ◽  
Josef Stetina
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Material ◽  
Graphics Processing Units ◽  
Parallel Implementation ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Wide Range ◽  
Graphics Processing ◽  
Change Material

Phase change materials have a wide range of application including thermal energy storage in building structures, solar air collectors, heat storage units and exchangers. Such applications often utilize a commercially produced phase change material enclosed in a thin panel (container) made of aluminum. A parallel 1D heat transfer model of a container with phase change material was developed by means of the control volume and effective heat capacity methods. The parallel implementation in the CUDA computing architecture allows the model for running on graphics processing units which makes the model very fast in comparison to traditional models computed on a single CPU. The paper presents the model implementation and results of computational model benchmarking carried out with the use of high-level and low-level GPUs NVIDIA.

Numerical Modeling of Multidirectional Flow and Heat Transfer in Graphitic Foams

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
S. A. Mohsen Karimian ◽  
Anthony G. Straatman
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Pore Structure ◽  
Linear Models ◽  
A Priori ◽  
Experimental Results ◽  
Transfer Model ◽  
Thermal Dispersion ◽  
Wide Range ◽  
Graphitic Foam

To investigate the feasibility of the use of foams with an interconnected spherical pore structure in heat transfer applications, models for heat transfer and pressure drop for this type of porous materials are developed. Numerical simulations are carried out for laminar multidirectional thermofluid flow in an idealized pore geometry of foams with a wide range of geometry parameters. Semiheuristic models for pressure drop and heat transfer are developed from the results of simulations. A simplified solid-body drag equation with an extended high inertia term is used to develop the hydraulic model. A heat transfer model with a nonzero asymptotic term for very low Reynolds numbers is also developed. To provide hydraulic and heat transfer models suitable for a wide range of porosity, only a general form of the length-scale as a function of pore structure is defined a priori, where the parameters of the function were determined as part of the modeling process. The proposed ideal models are compared to the available experimental results, and the source of differences between experimental results and the ideal models is recognized and then calibrated for real graphitic foam. The thermal model is used together with volume-averaged energy equations to calculate the thermal dispersion in graphitic foam. The results of the calculations show that the linear models for thermal dispersion available in literature are oversimplified for predicting thermal dispersion in this type of porous material.

scholarly journals Analysis of heating and cooling periods in Budapest using station data

Időjárás ◽  
2021 ◽  
Vol 125 (3) ◽  
pp. 431-448
Author(s):  
Csenge Dian ◽  
Attila Talamon ◽  
Rita Pongrácz ◽  
Judit Bartholy
Keyword(s):  
Energy Use ◽  
Transitional Period ◽  
Design Parameters ◽  
Data Series ◽  
Total Energy Consumption ◽  
Regional Warming ◽  
Cooling Systems ◽  
Cooling Period ◽  
Heating And Cooling ◽  
The One

The built environment has a very complex role in cities. On the one hand, various urban climatological phenomena are caused and influenced by buildings (e.g., urban heat island effect, local wind conditions, air pollution). On the other hand, buildings are important contributors to energy use via heating and cooling, e.g. they account for about 40% of total energy consumption on average in Europe. Daily average outdoor temperature is taken into account to design the heating and cooling systems of residential, commercial, or office buildings. That is why we analyzed the available temperature time series of the capital of Hungary, Budapest for the period between 1901 and 2019. The aims of this study are (i) to investigate the changes in temperature data series that influence building energy design parameters, (ii) to analyze the heating and cooling periods in the last 119 years based on different definitions, and (iii) to define a third (transitional) period between the heating and cooling periods. Based on the results, it can be concluded that the variability of warm days is smaller than that of cold days, consequently, the optimal design of heating systems is a greater challenge compared to cooling systems. Furthermore, the length of the temperature-based heating period decreased substantially, while the length of the cooling period increased as a consequence of overall regional warming.

scholarly journals Verification and Improving the Heat Transfer Model in Radiators in the Wide Change Operating Parameters

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6543
Author(s):  
Mieczysław Dzierzgowski
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Water Mass ◽  
Heat Transfer Model ◽  
Operating Conditions ◽  
Transfer Model ◽  
Flow Rates ◽  
Wide Range ◽  
Different Types ◽  
Mass Flow Rates

Laboratory measurements and analyses conducted in a wide range of changes of water temperature and mass flow rate for different types of radiators allowed to provides limitations and assessment of the current radiators heat transfer model according to EN 442. The inaccuracy to determinate the radiator heat output according to EN 442, in case of low water mass flow rates may achieve up to 22.3% A revised New Extended Heat Transfer Model in Radiators NEHTMiRmd is general and suitable for different types of radiators both new radiators and radiators existing after a certain period of operation is presented. The NEHTMiRmd with very high accuracy describes the heat transfer processes not only in the nominal conditions—in which the radiators are designed, but what is particularly important also in operating conditions when the radiators water mass flow differ significantly from the nominal value and at the same time the supply temperature changes in the whole range radiators operating during the heating season. In order to prove that the presented new model NEHTMiRmd is general, the article presents numerous calculation examples for various types of radiators currently used. Achieved the high compatibility of the results of the simulation calculations with the measurement results for different types of radiators: iron elements (not ribbed), plate radiators (medium degree ribbed), convectors (high degree ribbed) in a very wide range of changes in the water mass flow rates and the supply temperature indicates that a verified NEHTMiRmd can also be used in designing and simulating calculations of the central heating installations, for the rational conversion of existing installations and district heating systems into low temperature energy efficient systems as well as to directly determine the actual energy efficiency, also to improve the indications of the heat cost allocators. In addition, it may form the basis for the future modification of the European Standards for radiator testing.

scholarly journals A one-dimensional modeling study on the effect of advanced insulation coatings on internal combustion engine efficiency

2020 ◽  
pp. 146808742092158
Author(s):  
Alberto Broatch ◽  
Pablo Olmeda ◽  
Xandra Margot ◽  
Josep Gomez-Soriano
Keyword(s):  
Heat Transfer ◽  
Combustion Engine ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Insulation Material ◽  
One Dimensional ◽  
Engine Efficiency ◽  
Dimensional Modeling ◽  
The One ◽  
The Impact

This article presents a study of the impact on engine efficiency of the heat loss reduction due to in-cylinder coating insulation. A numerical methodology based on one-dimensional heat transfer model is developed. Since there is no analytic solution for engines, the one-dimensional model was validated with the results of a simple “equivalent” problem, and then applied to different engine boundary conditions. Later on, the analysis of the effect of different coating properties on the heat transfer using the simplified one-dimensional heat transfer model is performed. After that, the model is coupled with a complete virtual engine that includes both thermodynamic and thermal modeling. Next, the thermal flows across the cylinder parts coated with the insulation material (piston and cylinder head) are predicted and the effect of the coating on engine indicated efficiency is analyzed in detail. The results show the gain limits, in terms of engine efficiency, that may be obtained with advanced coating solutions.

Semi-Analytical Solution of a Non-Linear Heat Transfer Model for a Tubular Co-Current Moving-Bed Reactor with a First-Order Chemical Reaction in the Solid Phase

2021 ◽  
Author(s):  
Lucas Ivan de Souza Vereza Medeiros ◽  
Sávio Leandro Bertoli ◽  
Marcel Jefferson Gonçalves ◽  
Tuany Gabriela Hoffmann ◽  
Betina Louise Angioletti ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Chemical Reaction ◽  
Solid Phase ◽  
Transfer Model ◽  
Moving Bed ◽  
First Order ◽  
Order Chemical Reaction ◽  
Non Linear ◽  
Linear Problems ◽  
First Order Chemical Reaction

Abstract The development of mathematical models plays a fundamental role in the design, optimization and control of processes. Regarding heat transfer in moving bed reactors, the chemical reaction implies in the inclusion of a non-homogeneous and non-linear term in model equations, making the analytical integration a very difficult task. Up to date, there is not an analytic and/or a semi-analytic solution to a heat transfer model of a moving bed reactor (MBR) with isothermal walls to distributed parameter in the solid phase. Therefore, starting from analytical solutions of the associated homogeneous (linear) problems and through the spectral expansion of the non-homogeneous vector, this work presents strategies for determining semi-analytical solutions of non-homogeneous and non-linear problems. A MBR with a first-order chemical reaction in the solid phase - kaolinite dehydroxylation in the kaolinite flash calcination process - is selected as the case study; however, the strategies can easily be applied to other non-linear models. Results for conversion, and fluid and particle temperatures, are given for different parameter values. The solutions perform stable, fast and accurate. When compared with a hybrid Finite Difference and Finite Analytic (FD\&FA) numerical method, the solution showed a very good agreement.

Heat-Transfer Stability of Porous Fibrous Composition under Different Condition

2014 ◽  
Vol 1004-1005 ◽  
pp. 557-561
Author(s):  
Yu Juan Wang ◽  
Hai Zhen Chen ◽  
Jin Mei Wang ◽  
Mei Zhen Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Process ◽  
Surface Condition ◽  
Transfer Model ◽  
Unsteady Heat Transfer ◽  
One Dimensional ◽  
The One ◽  
Thermal Difference ◽  
Key Parameter

In this paper, the influences of different conditions on heat-transfer stability of porous fibrous composition were analyzed by the one-dimensional unsteady heat transfer model. It was resulted that the surface condition of composition was key parameter for heat performance during different thermal process. Great humidity and thermal difference caused the heat transfer fluctuating of material covering, and then changed the thermal conductivity. For the insulation materials under low temperature, the heat performance was sharply fluctuated nearby 0°C.

scholarly journals Numerical Evaluation of the Transient Performance of Rock-Pile Seasonal Thermal Energy Storage Systems Coupled with Exhaust Heat Recovery

2020 ◽  
Vol 10 (21) ◽  
pp. 7771
Author(s):  
Leyla Amiri ◽  
Marco Antonio Rodrigues de Brito ◽  
Seyed Ali Ghoreishi-Madiseh ◽  
Navid Bahrani ◽  
Ferri P. Hassani ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Waste Heat ◽  
Fluid Velocity ◽  
Transfer Model ◽  
Mining Operations ◽  
Exhaust Heat ◽  
Wide Range

This study seeks to investigate the concept of using large waste rocks from mining operations as waste-heat thermal energy storage for remote arctic communities, both commercial and residential. It holds its novelty in analyzing such systems with an experimentally validated transient three-dimensional computational fluid dynamics and heat transfer model that accounts for interphase energy balance using a local thermal non-equilibrium approach. The system performance is evaluated for a wide range of distinct parameters, such as porosity between 0.2 and 0.5, fluid velocity from 0.01 to 0.07 m/s, and the aspect ratio of the bed between 1 and 1.35. It is demonstrated that the mass flow rate of the heat transfer fluid does not expressively impact the total energy storage capacity of the rock mass, but it does significantly affect the charge/discharge times. Finally, it is shown that porosity has the greatest impact on both fluid flow and heat transfer. The evaluations show that about 540 GJ can be stored on the bed with a porosity of 0.2, and about 350 GJ on the one with 0.35, while the intermediate porosity leads to a total of 450 GJ. Additionally, thermal capacity is deemed to be the most important thermophysical factor in thermal energy storage performance.

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