Modeling of Heat Transfer in a Moving Packed Bed: Case of the Preheater in Nickel Carbonyl Process

2005 ◽  
Vol 73 (1) ◽  
pp. 47-53 ◽  
Author(s):  
Redhouane Henda ◽  
Daniel J. Falcioni
Keyword(s):  
Heat Transfer ◽  
Packed Bed ◽  
Outer Wall ◽  
Volume Averaging ◽  
Equation Model ◽  
Operating Conditions ◽  
Design Parameters ◽  
Gas Phases ◽  
Calculation Results ◽  
The Difference

Heat transfer in a two-dimensional moving packed bed consisting of pellets surrounded by a gaseous atmosphere is numerically investigated. The governing equations are formulated based on the volume averaging method. A two-equation model, representing the solid and gas phases separately, and a one-equation model, representing both the solid and gas phases, are considered. The models take the form of partial differential equations with a set of boundary conditions, some of which were determined experimentally, and design parameters in addition to the operating conditions. We examine and discuss the parameters in order to reduce temperature differences from pellet to pellet. The calculation results show that by adopting a constant temperature along the preheater outer wall and decreasing the velocity of the pellets in the preheater, the difference in temperature from pellet to pellet is reduced from ∼120°C to ∼55°C, and the thermal efficiency of the preheater is tremendously improved.

scholarly journals Comparison of Building Simulation Methods for Modeling Apartment Balconies

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3955
Author(s):  
Yonghan Ahn ◽  
Hanbyeol Jang ◽  
Junghyon Mun
Keyword(s):  
Heat Transfer ◽  
Air Temperature ◽  
Parameter Analysis ◽  
Interior Space ◽  
Heating And Cooling ◽  
Significant Difference ◽  
Calculation Results ◽  
Infiltration Parameter ◽  
The Difference ◽  
Heating And Cooling Load

The purpose of this study is to compare the load calculation results by a model using the air changes per hour (ACH) method and a model using an airflow network (AFN) and to ascertain what causes the difference between the two models. In the basic case study, the difference in the heat transfer distribution of the model in the interior space was investigated. The most significant difference between the two models is the heat transfer that results from infiltration. Parameter analysis was performed to investigate the relationship between the difference and the environmental variables. The result shows that the greater the difference is between the air temperature inside the balcony and the outdoor air temperature, and the greater the air flows from the balcony to the residential area, and the greater the heating and cooling load difference occurs. The analysis using the actual weather files of five domestic cities in South Korea rather than a virtual case shows that the differences are not so obvious when the wind blows at a constant speed throughout the year, but are dominant when the wind does not blow during the night and is stronger alongside the occurrence of sunlight during the day.

Merits of Employing Foam Encapsulated Phase Change Materials for Pulsed Power Electronics Cooling Applications

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
K. Lafdi ◽  
O. Mesalhy ◽  
A. Elgafy
Keyword(s):  
Phase Change ◽  
Heat Sink ◽  
Phase Change Materials ◽  
Electronics Cooling ◽  
Volume Averaging ◽  
Equation Model ◽  
Heat Diffusion ◽  
Solid Matrix ◽  
Design Parameters ◽  
Heat Diffusion Equation

In the present work, the potential of using foam structures impregnated with phase change materials (PCMs) as heat sinks for cooling of electronic devices has been numerically studied. Different design parameters have been investigated such as foam properties (porosity, pore size, and thermal conductivity), heat sink shape, orientation, and use of internal fins inside the foam-PCM composite. Due to huge difference in thermal properties between the PCM and the solid matrix, two energy equation model has been adopted to solve the energy conservation equations. This model can handle local thermal nonequilibrium condition between the PCM and the solid matrix. The numerical model is based on volume averaging technique, and the finite volume method is used to discretize the heat diffusion equation. The findings show that, for steady heat generation, the shape and orientation of the composite heat sink have significant impact on the system performance. Conversely, in the case of power spike input, use of a PCM with low melting point and high latent heat is more efficient.

An Experimental Investigation of Heat Transfer in Variable Porosity Media

1985 ◽  
Vol 107 (3) ◽  
pp. 642-647 ◽  
Author(s):  
K. Vafai ◽  
R. L. Alkire ◽  
C. L. Tien
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Packed Bed ◽  
Volume Averaging ◽  
Experimental Results ◽  
Variable Porosity ◽  
Local Volume Averaging ◽  
Convection In Porous Media ◽  
Impermeable Boundary ◽  
Good Agreement

This paper presents an experimental investigation on the effects of a solid impermeable boundary and variable porosity on forced convection in porous media. Emphasis is placed on the channeling effects on heat transfer in packed beds. The local volume-averaging technique is used to establish the governing equations and a numerical scheme is developed which incorporates the boundary and variable porosity effects on heat transfer. The experimental results for the heat flux at the boundary are presented as a function of the pertinent variables in a packed bed. The Nusselt number is found to increase almost linearly with an increase in the Reynolds number based on the pore diameter. The experimental results are found to be in good agreement with the theoretical results which account for the variable porosity effects. A comparison between the numerical and the experimental results demonstrates the importance of boundary and variable porosity effects on heat transfer in variable porosity media.

Effect of Materials on the Heat Transfer to Supercritical Pressure Fluids

2017 ◽  
Author(s):  
Xianliang Lei ◽  
Xiangfei Kong ◽  
Qian Zhang ◽  
Weiqiang Zhang ◽  
Huixiong Li
Keyword(s):  
Heat Transfer ◽  
Chemical Properties ◽  
Heating Surface ◽  
Supercritical Pressure ◽  
Operating Conditions ◽  
Inconel 600 ◽  
Heat Transfer Efficiency ◽  
Circular Pipes ◽  
The Difference ◽  
Aisi 321

Supercritical pressure fluids are widely used in many advanced single-phase thermosiphons as a working medium due to its high convective heat transfer efficiency and simpler design. However, the heat transfer in the pseudocritical region is very complex due to its steep variation of thermophysical properties and effect by the operating parameters. Under supercritical pressures, special heat transfer phenomenon can be observed in the heated tubes, three totally different heat transfer regimes present. As a result of the similarity between subcritical boiling phenomena and the deteriorated heat transfer behavior at supercritical pressure, scholars observed that heater with different materials but the same operating conditions, different types of free convection would be appeared by investigating the boiling-like phenomenon of carbon dioxide, which seems that boiling-like phenomena are specific to heater materials. The aim of this present study is to investigate the effects of thermophysical and chemical properties of heater materials upon heat transfer to supercritical water. In the present paper, two circular pipes with differential usual materials (AISI 321 and Inconel 600) are experimentally investigated by the electrically heating methods. The difference between AISI 321 and Inconel 600 in both enhanced and deteriorated heat transfer regimes are discussed respectively, then the heat transfer discrepancy caused by the materials analyzed. The results show that the heat transfer of supercritical pressure fluids dependent not only on the variation of the operating/boundary conditions but also on the materials of heating surface.

scholarly journals MEASURING TEMPERATURE OF THE MEDIUM OF SHIP COMPRESSOR PIPING USING TEMPERATURE OF THE OUTER WALL

2018 ◽  
pp. 81-86
Author(s):  
Alexander Evgenyevich Semenov ◽  
Sergey Anatolyevich Putilin
Keyword(s):  
Heat Transfer ◽  
Theoretical Data ◽  
Outer Wall ◽  
Operating Conditions ◽  
Measured Temperature ◽  
Medium Temperature ◽  
Factors Affecting ◽  
Operating Modes ◽  
Piping Systems ◽  
Pipeline Wall

To determine the temperature of the medium in the ship's piping systems there are used readings of contact thermometers, pyrometers and thermal scans which measure the temperature of the pipeline rather accurately. Aside from corrections for accuracy of the measurement of the wall temperature, it is necessary to move towards measuring temperature of the medium. Readings of the temperature of the pipeline wall differ from the readings of the medium temperature inside the pipeline, so it is necessary to calculate and find the temperature of the medium in the pipeline. After solving a system of equations describing the phenomenon of heat transfer through the cylindrical surface, there has been worked out the technique of measuring temperature of the pipeline medium, according to the measured temperature of the pipe wall. The conditions of heat transfer can vary for different pipelines and media. The paper gives calculated temperature corrections for different operating conditions of the pipeline. To carry out calculations, a computer program has been written in the Mathcad mathematical package. Temperature corrections have been calculated to determine the medium temperature inside the pipeline using the temperature value of the outer wall of the pipeline. There has been carried out analysis of various factors affecting temperature changes: heat transfer to the air, heat transfer of medium inside the pipeline, wall thickness and contamination. Verification of theoretical data has been made on a ship of the compressor unit. The experiment confirmed the possibility of measuring temperature of the medium inside the pipeline, according to the temperature of pipeline surface using the developed corrections. Devices measuring the temperature of the pipeline walls can be used as additional measurement to enhance informativeness of testing results, analysis of operating modes, and improve the operation reliability of ship piping systems

scholarly journals Methodology of constructing driving cycles by the synthesis

2021 ◽  
Vol 264 ◽  
pp. 01033
Author(s):  
Akmal Mukhitdinov ◽  
Kamoliddin Ziyaev ◽  
Janserik Omarov ◽  
Shokhsanam Ismoilova
Keyword(s):  
Fuel Consumption ◽  
Information Technologies ◽  
Operating Conditions ◽  
Design Parameters ◽  
Systematic Analysis ◽  
Driving Cycles ◽  
The Difference ◽  
Traffic Organization ◽  
The City ◽  
Car Driving

The difference in the dynamics of the development of motorization in the regions of the world, the levels of traffic organization, determines the need to develop a methodology for specific operating conditions. Improvement of the existing driving cycles and methods of their development, which characterize the real operating conditions, is of great importance. An important task is considered the implementation of targeted research to improve automobile operation efficiency of vehicles by introducing modern information technologies into the process of determining the driving cycles, modernizing the design parameters of vehicles by assessing the influence of driving conditions when rationing fuel consumption, developing methods for choosing the design parameters of vehicles and the most adapted vehicle for specific operating conditions. The article provides a systematic analysis of scientific research of methodology for constructing driving cycles, factors influencing the performance and driving modes, as well as the fuel consumption of the car. The methodology for constructing a standard driving cycle for specific urban operating conditions is given based by synthesizing on passenger car driving modes in the city.

scholarly journals Thermal-hydraulic modeling of the steady-state operating conditions of a fire-tube boiler

2009 ◽  
Vol 24 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Ahmed Rahmani ◽  
Ahmed Dahia
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Hydraulic Modeling ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Saturated Steam ◽  
Operating Pressure ◽  
Operating Data ◽  
Boiler Operation ◽  
Calculation Results

In this work, we are interested to simulate the thermal-hydraulic behavior of three-pass type fire-tube boiler. The plant is designed to produce 4.5 tons per hour of saturated steam at 8 bar destined principally for heating applications. A calculation program is developed in order to simulate the boiler operation under several steady-state operating conditions. This program is based upon heat transfer laws between hot gases and the fire-tube internal walls. In the boiler combustion chamber, the heat transfer has been simulated using the well-stirred furnace model. In the convection section, heat balance has been carried out to estimate the heat exchanges between the hot gases and the tube banks. The obtained results are compared to the steady-state operating data of the considered plant. A comparative analysis shows that the calculation results are in good agreement with the boiler operating data. Furthermore, a sensitivity study has been carried out to assess the effects of input parameters, namely the fuel flow rate, air excess, ambient temperature, and operating pressure, upon the boiler thermal performances.

Heat Transfer in a High-Temperature Packed Bed Thermal Energy Storage System—Roles of Radiation and Intraparticle Conduction

1996 ◽  
Vol 118 (1) ◽  
pp. 50-57 ◽  
Author(s):  
A. A. Jalalzadeh-Azar ◽  
W. G. Steele ◽  
G. A. Adebiyi
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Packed Bed ◽  
Energy Storage System ◽  
Operating Conditions ◽  
Thermal Energy Storage System

A model is developed and experimentally verified to study the heat transfer in a high-temperature packed bed thermal energy storage system utilizing zirconium oxide pellets. The packed bed receives flue gas at elevated temperatures varying with time during the storage process and utilizes air for the recovery process. Both convection and radiation are included in the model of the total heat transfer between the gas and the pellets. It is found that thermal radiation and intraparticle conduction do not play a major role in the overall heat transfer in the packed bed under the specified operating conditions. An uncertainty analysis is performed to investigate the propagation of the uncertainties in the variables to the overall uncertainty in the model predictions and the experimental results.

Failure Analysis of Plastic Pipe Reinforced by Cross Helically Wound Steel Wire Subjected to Internal Pressure and Bending Load

2016 ◽  
Author(s):  
Jie Zhang ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Internal Pressure ◽  
Steel Wire ◽  
Operating Conditions ◽  
Combined Loading ◽  
Design Parameters ◽  
Fe Model ◽  
Plastic Pipe ◽  
Bending Load ◽  
Calculation Results ◽  
Bending Loads

Plastic pipe reinforced by cross helically wound steel wire (PSP) has been widely used in the transportation of petroleum, natural gas, municipal water, etc. In some serious occasions, PSP suffers from bending load caused by operating conditions such as ocean wave, pipeline laying and geological sedimentation, besides internal pressure. Thus, to understand the strength of PSP under the complex loads is crucial for ensuring safety. In this study, a finite element (FE) model of PSP was proposed by taking both internal pressure and bending load into consideration. By gradually increasing the bending load, the strength of PSP was obtained by taking the break of steel wires as the failure criterion. Then, combined loading tests were conducted to verify the proposed model. The results show that the applied bending loads bear a nonlinear relationship with the increasing deformation. By comparing experimental results and FE model calculation results, good agreement was obtained. Based on the verified FE model, the limit bending load and the effects of design parameters and internal pressure on the strength of PSP were discussed.

Influence of twisted tape fins on heat transfer and friction factor characteristics for impinging jet solar air heater

2021 ◽  
pp. 095440892199528
Author(s):  
MM Matheswaran ◽  
TV Arjunan ◽  
Mukesh K Sahu
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Impinging Jet ◽  
Operating Conditions ◽  
Design Parameters ◽  
Twisted Tape ◽  
Solar Air Heater ◽  
Air Heater ◽  
Twist Ratio ◽  
Pitch Ratio

In this work, an experimental study was carried out to investigate the enhancement of heat transfer and friction factor characteristics of an impinging jet solar air heater integrated with twisted tape fins. During the analysis, the Reynolds number fin design parameters namely twist ratio (Y), and pitch ratio (py) are varied from 3500 –13500, 5.5–9.5, and 0.1–0.3, respectively. During the experimentation, the constant heat flux of 1000 W/m2 was maintained on the absorber plate. From the results, it was observed that the heat transfer rate increases while increasing the twist ratio up to 7.5 and further increase in twist ratio diminishes the performance. It was also concluded that the rise in pitch ratio (py) deteriorates the rate of heat transfer. The present work enhances the heat transfer and friction factor by the maximum of 1.9 and 1.81 times as compared with the conventional jet impingement solar air heater at identical operating conditions.

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