Dynamic analysis of nonsteady heat transfer in a fixed bed of spheres at a variable gas-flow temperature

1968 ◽  
Vol 14 (2) ◽  
pp. 156-158
Author(s):  
V. A. Makovskii
Keyword(s):  
Heat Transfer ◽  
Dynamic Analysis ◽  
Gas Flow ◽  
Fixed Bed ◽  
Flow Temperature ◽  
Nonsteady Heat ◽  
Nonsteady Heat Transfer

Study on Effective Radial Thermal Conductivity of Gas Flow through a Methanol Reactor

2015 ◽  
Vol 13 (1) ◽  
pp. 103-112 ◽  
Author(s):  
Kun Lei ◽  
Hongfang Ma ◽  
Haitao Zhang ◽  
Weiyong Ying ◽  
Dingye Fang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Temperature Distribution ◽  
Large Scale ◽  
Gas Flow ◽  
Fixed Bed ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Particle Reynolds Number

Abstract The heat conduction performance of the methanol synthesis reactor is significant for the development of large-scale methanol production. The present work has measured the temperature distribution in the fixed bed at air volumetric flow rate 2.4–7 m3 · h−1, inlet air temperature 160–200°C and heating tube temperature 210–270°C. The effective radial thermal conductivity and effective wall heat transfer coefficient were derived based on the steady-state measurements and the two-dimensional heat transfer model. A correlation was proposed based on the experimental data, which related well the Nusselt number and the effective radial thermal conductivity to the particle Reynolds number ranging from 59.2 to 175.8. The heat transfer model combined with the correlation was used to calculate the temperature profiles. A comparison with the predicated temperature and the measurements was illustrated and the results showed that the predication agreed very well with the experimental results. All the absolute values of the relative errors were less than 10%, and the model was verified by experiments. Comparing the correlations of both this work with previously published showed that there are considerable discrepancies among them due to different experimental conditions. The influence of the particle Reynolds number on the temperature distribution inside the bed was also discussed and it was shown that improving particle Reynolds number contributed to enhance heat transfer in the fixed bed.

A Simplified Numerical Approach to Characterize the Thermal Response of a Moving Bed Solar Reactor

2021 ◽  
Author(s):  
Assaad Al Sahlani ◽  
Kelvin Randhir ◽  
Nesrin Ozalp ◽  
James Klausner
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Energy Storage ◽  
Solid Particle ◽  
Gas Flow ◽  
Plug Flow ◽  
Fixed Bed ◽  
Flow Rates ◽  
Proposed Model ◽  
Simulation Results

Abstract Concentrated solar thermochemical storage in the form of a zero-emission fuel is a promising option to produce long-duration energy storage. The production of solar fuel can occur within a cylindrical cavity chemical reactor that captures concentrated solar radiation from a solar field. A heat transfer model of a tubular plug-flow reactor is presented. Experimental data from a fixed bed tubular reactor are used for model comparison. The system consists of an externally heated tube with counter-current flowing gas and moving solid particles as the heated media. The proposed model simulates the dynamic behavior of temperature profiles of the tube wall, gas, and particles under various gas flow rates and residence times. The heat transfer between gas-wall, solid particle-wall, gas-solid particle, are numerically studied. The model is compared with experiments using a 4 kW furnace with a 150 mm heating zone surrounding a horizontal alumina tube (reactor) with 50.8 mm OD and a thickness of 3.175 mm. Solid fixed particles of magnesium manganese oxide (MgMn2O4) with the size of 1 mm are packed within the length of 250 mm at the center of the tube length. Simulation results are assessed with respect to fixed bed experimental data for four different gas flow rates, namely 5, 10, 15, 20 standard liters per minute of air, and furnace temperatures in the range of 200 to 1200 °C. The simulation results showed good agreement with maximum steady state error that is less than 6% of those obtained from the experiments among all runs. The proposed model can be implemented as a low-order physical model for the control of temperature inside plug-flow reactors for thermochemical energy storage (TCES) applications.

CFD Simulation of Reaction and Heat Transfer Near the Wall of a Fixed Bed

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Anthony G. Dixon ◽  
Michiel Nijemeisland ◽  
Hugh Stitt
Keyword(s):  
Heat Transfer ◽  
Steam Reforming ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Control Volume ◽  
Fixed Bed ◽  
Particle Diameter ◽  
Effect Of Temperature ◽  
Temperature Profiles ◽  
Computational Domain

Modeling of fluid flow, heat transfer and reaction in fixed beds is an essential part of their design. This is especially critical for highly endothermic or exothermic reactions in low tube-to-particle diameter ratio (N) tubes, such as are used in steam reforming and partial oxidation. In the simulations a near-wall section of an entire bed is used to create a simulation geometry that can be handled in the available computational domain. A full bed model was also available for validation of the wall-segment model. In the wall-segment approach a section of the bed is modeled in more detail, allowing for a relatively smaller control volume size and a more detailed view of the flow and heat transfer patterns. A simple model of a steam reforming process is used in the CFD simulation to incorporate the effect of reaction rate on temperature profiles in the bed. Simulations were performed under realistic industrial conditions of high temperature, pressure and gas flow rate, with gas properties corresponding to those of steam reforming. A constant wall heat flux was imposed, and various shapes of particles studied with heat sinks on the surface to simulate the reforming endothermic reaction, which is mainly confined to the surface of the pellet. Results will be presented showing the existence and effect of temperature profiles on the catalyst particles, and the effect on the local heat transfer rates of different gas compositions, corresponding to conditions at different locations along the catalyst tube. Local deactivation of catalyst particles can also lead to wall hot spots, or 'giraffe-necking' which can be well-reproduced by the simulations.

Nonsteady heat transfer in diffusing systems

1983 ◽  
Vol 44 (1) ◽  
pp. 91-96
Author(s):  
T. N. Abramenko ◽  
I. Mashtovskii ◽  
E. A. Shashkov ◽  
A. F. Zolotukhina
Keyword(s):  
Heat Transfer ◽  
Nonsteady Heat ◽  
Nonsteady Heat Transfer

Nonsteady heat transfer and transient processes in blast furnaces

2015 ◽  
Vol 45 (9) ◽  
pp. 654-657 ◽  
Author(s):  
Yu. G. Yaroshenko ◽  
V. S. Shvydkii ◽  
N. A. Spirin ◽  
V. V. Lavrov ◽  
V. Yu. Noskov
Keyword(s):  
Heat Transfer ◽  
Transient Processes ◽  
Blast Furnaces ◽  
Nonsteady Heat ◽  
Nonsteady Heat Transfer

Process Intensification in a “Simulated Moving-Bed” Heat Regenerator

2008 ◽  
Vol 130 (9) ◽  
Author(s):  
D. S. Murthy ◽  
S. V. Sivakumar ◽  
Keshav Kant ◽  
D. P. Rao
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Fixed Bed ◽  
Process Intensification ◽  
Thermal Recovery ◽  
Simulated Moving Bed ◽  
Thermal Regeneration ◽  
Heat Transfer Intensification ◽  
Moving Bed ◽  
High Heat Transfer

The solid-gas contacting for thermal storage and thermal recovery is generally carried out in fixed-bed regenerators. Compared to a fixed bed, higher thermal recovery can be achieved in a moving bed with countercurrent flow of gas and solids. However, the moving beds have not been widely used due to difficulties in solid handling. The relative movement of the bed to the gas flow can be simulated in a fixed bed by moving the inlet and outlet ports of the gas along the length of the bed. Similar simulated moving beds are already in use for adsorptive separation of liquid mixtures in chemical industries. A novel moving-port system is proposed to achieve simulated moving-bed operation in a fixed bed. We have carried out studies to evaluate the relative performance of the fixed and the simulated moving-bed heat regenerators. We have examined the feasibility of replacing a set of three blast furnaces and thermal regeneration of an adsorption bed with the simulated moving-bed regenerator. It is found that high-heat transfer intensification can be achieved. The results indicate that three blast-furnace stoves can be replaced by a simulated moving-bed regenerator of volume of about 100 times smaller than the stoves. The heat-transfer intensification is high enough to carry out thermal regeneration of the adsorption beds in a cycle time that is in the range of the pressure swing adsorption, which is favored for its faster rate of regeneration.

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