scholarly journals A CFD Design Approach for Industrial Size Tubular Reactors for SNG Production from Biogas (CO2 Methanation)

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6175
Author(s):  
Victor Soto ◽  
Claudia Ulloa ◽  
Ximena Garcia
Keyword(s):  
Heat Transfer ◽  
Molten Salts ◽  
Hot Spot ◽  
Tubular Reactor ◽  
Gas Production ◽  
Thermal Design ◽  
Coolant Flow ◽  
Reactor Performance ◽  
Transfer Coefficients ◽  
Co2 Methanation

A tubular reactor based on the disk and doughnut concept was designed as an engineering solution for biogas upgrading via CO2 methanation. CFD (Computational Fluid Dynamics) benchmarks agreed well with experimental and empirical (correlation) data, giving a maximum error of 8.5% and 20% for the chemical reaction and heat transfer models, respectively. Likewise, hot spot position was accurately predicted, with a 5% error. The methodology was used to investigate the effect of two commercially available coolants (thermal oil and molten salts) on overall reactor performance through a parametric study involving four coolant flow rates. Although molten salts did show higher heat transfer coefficients at lower coolant rates, 82% superior, it also increases, by five times, the pumping power. A critical coolant flow rate (3.5 m3/h) was found, which allows both a stable thermal operation and optimum pumping energy consumption. The adopted coolant flow range remains critical to guarantee thermal design validity in correlation-based studies. Due to the disk and doughnut configuration, coolant flow remains uniform, promoting turbulence (Re ≈ 14,000 at doughnut outlet) and maximizing heat transfer at hot spot. Likewise, baffle positioning was found critical to accommodate and reduce stagnant zones, improving the heat transfer. Finally, a reactor design is presented for SNG (Synthetic Natural Gas) production from a 150 Nm3 h−1 biogas plant.

Thermal Analysis of Cooling System in a Gas Turbine Transition Piece

2011 ◽  
Author(s):  
Jun Su Park ◽  
Namgeon Yun ◽  
Hokyu Moon ◽  
Kyung Min Kim ◽  
Sin-Ho Kang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Cooling System ◽  
Structural Information ◽  
Thermal Analyses ◽  
Thermal Design ◽  
Transfer Coefficients ◽  
Transition Piece ◽  
Inlet Conditions

This paper presents thermal analyses of the cooling system of a transition piece, which is one of the primary hot components in a gas turbine engine. The thermal analyses include heat transfer distributions induced by heat and fluid flow, temperature, and thermal stresses. The purpose of this study is to provide basic thermal and structural information on transition piece, to facilitate their maintenance and repair. The study is carried out primarily by numerical methods, using the commercial software, Fluent and ANSYS. First, the combustion field in a combustion liner with nine fuel nozzles is analyzed to determine the inlet conditions of a transition piece. Using the results of this analysis, pressure distributions inside a transition piece are calculated. The outside of the transition piece in a dump diffuser system is also analyzed. Information on the pressure differences is then used to obtain data on cooling channel flow (one of the methods for cooling a transition piece). The cooling channels have exit holes that function as film-cooling holes. Thermal and flow analyses are carried out on the inside of a film-cooled transition piece. The results are used to investigate the adjacent temperatures and wall heat transfer coefficients inside the transition piece. Overall temperature and thermal stress distributions of the transition piece are obtained. These results will provide a direction to improve thermal design of transition piece.

Heat Transfer Modeling in a Counter-Current Moving-Bed Tubular Reactor for High-Temperature Thermochemical Energy Storage

2021 ◽  
Author(s):  
Wei Huang ◽  
Eric Million ◽  
Kelvin Randhir ◽  
Joerg Petrasch ◽  
James Klausner ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Tubular Reactor ◽  
Operating Conditions ◽  
Transfer Model ◽  
Reactor Performance ◽  
Low Oxygen ◽  
Moving Bed ◽  
Oxidation Reactor ◽  
Counter Current

Abstract An axisymmetric model coupling counter-current gas-solid flow, heat transfer, and thermochemical redox reactions in a moving-bed tubular reactor was developed. The counter-current flow enhances convective heat transfer and a low oxygen partial pressure environment is maintained for thermal reduction within the reaction zone by using oxygen depleted inlet gas. A similar concept can be used for the oxidation reactor which releases high-temperature heat that can be used for power generation or as process heat. The heat transfer model was validated with published results for packed bed reactors. After validation, the model was applied to simulate the moving-bed reactor performance, through which the effects of the main geometric parameters and operating conditions were studied to provide guidance for lab-scale reactor fabrication and testing.

scholarly journals Heat Transfer Measurements for Rotating Turbine Discs

1989 ◽  
Author(s):  
G. Qureshi ◽  
M. H. Nguyen ◽  
N. R. Saad ◽  
R. N. Tadros
Keyword(s):  
Heat Transfer ◽  
Coolant Flow ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Rotating Disc ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Rotating Discs ◽  
Turbine Disc ◽  
State Technique

To optimise the turbine disc weight and coolant flow requirements, the aspect of improving thermal analysis was investigated. As a consequence, an experimental investigation was undertaken to measure the rates of convective heat transfer. The constant temperature steady state technique was used to determine the local and average heat transfer coefficients on the sides of rotating discs. The effects of coolant flow rates, CW (3000 ≤ CW ≤ 18600) with two types of cavity in-flow conditions and of the rotational speeds, Reθ (from 4×105 to 1.86×106) on the disc heat transfer were studied and correlations developed. For a rotating disc in confined cavities with superimposed coolant flows, Nusselt numbers were found to be higher than those for the free rotating disc without confinement.

Microprocessor Silicon Die Temperature Prediction by Simplified Boundary Conditions

2015 ◽  
Author(s):  
Koji Nishi ◽  
Tomoyuki Hatakeyama ◽  
Shinji Nakagawa ◽  
Masaru Ishizuka
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Boundary Conditions ◽  
Thermal Resistance ◽  
Hot Spot ◽  
Three Dimensional ◽  
Thermal Design ◽  
Target Temperature ◽  
One Dimensional ◽  
Thermal Network

The thermal network method has a long history with thermal design of electronic equipment. In particular, a one-dimensional thermal network is useful to know the temperature and heat transfer rate along each heat transfer path. It also saves computation time and/or computation resources to obtain target temperature. However, unlike three-dimensional thermal simulation with fine pitch grids and a three-dimensional thermal network with sufficient numbers of nodes, a traditional one-dimensional thermal network cannot predict the temperature of a microprocessor silicon die hot spot with sufficient accuracy in a three-dimensional domain analysis. Therefore, this paper introduces a one-dimensional thermal network with average temperature nodes. Thermal resistance values need to be obtained to calculate target temperature in a thermal network. For this purpose, thermal resistance calculation methodology with simplified boundary conditions, which calculates thermal resistance values from an analytical solution, is also introduced in this paper. The effectiveness of the methodology is explored with a simple model of the microprocessor system. The calculated result by the methodology is compared to a three-dimensional heat conduction simulation result. It is found that the introduced technique matches the three-dimensional heat conduction simulation result well.

Heat Removal and Thermal Stabilization of High-temperature Surfaces by a Dispersed Coolant Flow

Vestnik MEI ◽  
2021 ◽  
pp. 19-26
Author(s):  
Valentin S. Shteling ◽  
◽  
Vladimir V. Ilyin ◽  
Aleksandr T. Komov ◽  
Petr P. Shcherbakov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flux Density ◽  
Flow Rate ◽  
Heat Flux Density ◽  
Coolant Flow ◽  
Transfer Coefficients ◽  
Stationary Heat ◽  
Heat Transfer Coefficients ◽  
Stationary Heat Transfer

The effectiveness of stabilizing the surface temperature by a dispersed coolant flow is experimentally studied on a bench simulating energy intensive elements of thermonuclear installations A test section in which the maximum heat flux density can be obtained when being subjected to high-frequency heating was developed, manufactured, and assembled. The test section was heated using a VCh-60AV HF generator with a frequency of not lower than 30 kHz. A hydraulic nozzle with a conical insert was used as the dispersing device. Techniques for carrying out an experiment on studying a stationary heat transfer regime and for calculating thermophysical quantities were developed. The experimental data were obtained in the stationary heat transfer regime with the following range of coolant operating parameters: water pressure equal to 0.38 MPa, water mass flow rate equal to 5.35 ml/s, and induction heating power equal to 6--19 kW. Based on the data obtained, the removed heat flux density and the heat transfer coefficients were calculated for each stationary heat transfer regime. The dependences of the heat transfer coefficient on the removed heat flux density and of the removed heat flux density on the temperature difference have been obtained. High values of heat transfer coefficients and heat flux density at a relatively low coolant flow rate were achieved in the experiments.

Thermal and mechanical analysis of an SU8 polymeric actuator using infrared thermography

2008 ◽  
Vol 222 (1) ◽  
pp. 73-86 ◽  
Author(s):  
B Solano ◽  
S Rolt ◽  
D Wood
Keyword(s):  
Heat Transfer ◽  
Infrared Thermography ◽  
Microelectromechanical Systems ◽  
Thermomechanical Analysis ◽  
Mechanical Analysis ◽  
Thermal Design ◽  
Conductive Heat ◽  
Transfer Coefficients ◽  
Design Assessment ◽  
Spatially Resolved

In the current paper, report the detailed thermomechanical analysis of a polymeric thermal actuator integrated in a microelectromechanical systems microgripper, is reported. The inclusion of an actuator design which eliminates completely the parasitic resistance of the cold arm improves considerably the thermal efficiency of the system and enables large displacements at lower input voltages and operating temperatures than reported previously. Two different microgrippers built using a trilayer polymer/metal/polymer combination of SU8/gold/SU8 have been modelled, fabricated, and tested. As opposed to standard models, heat transfer by conduction to the ambient as well as between adjacent beams has been modelled. A semi-empirical approach for the calculation of conductive heat transfer coefficients has also been provided. The analysis combines simulations with electrical, deflection, and spatially resolved temperature measurements. The latter was carried out using infrared thermography, its use in polymeric actuators reported here for the first time. The good agreement between the models and the experimental data support the conclusions of the basic analytical model, i.e. thermal losses are dominated by two conduction mechanisms (into the ambient and between the hot and cold arms), and encourage its use for qualitative thermal design assessment and optimization.

Effect of Rotation and Coolant Throughflow on the Heat Transfer and Temperature Field in an Enclosure

1976 ◽  
Vol 98 (3) ◽  
pp. 387-394 ◽  
Author(s):  
E. M. Sparrow ◽  
Leonardo Goldstein
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Flow Rate ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Transfer Coefficients ◽  
Disk System ◽  
Heat Transfer Coefficients

Measurements were performed to determine the local heat transfer coefficients along the heated shroud of a shrouded parallel disk system. The temperature field within the enclosure formed by the shroud and the disks was also measured. One of the disks was rotating, whereas the other disk and the shroud were stationary. Coolant air was introduced into the enclosure through an aperture at the center of the stationary disk and exited through a slot at the rim of the rotating disk. The coolant entrance-exit arrangement differed from that of previous studies, with the additional difference that the incoming coolant stream was free of rotation. The coolant flow rate, the disk rotational speed, and the aspect ratio of the enclosure were varied during the experiments. The heat transfer coefficients were found to be increasingly insensitive to the absence or presence of rotation as the coolant flow rate increased. There was a general increase of the transfer coefficients with increasing coolant flow rate, especially for low rotational speeds. The temperature field in the enclosure differed markedly depending on the relative importance of rotation and of coolant throughflow. When the latter dominates, the temperature in the core is relatively uniform, but in the presence of strong rotation there are significant nonuniformities. A comparison was made between the present Nusselt number results and those of prior experiments characterized by different coolant entrance—exit arrangements. The positioning of the coolant exit slot relative to the direction of the boundary layer flow on the shroud emerged as an important factor in the comparison.

Fluidized Bed Solar Collector

1988 ◽  
Vol 110 (4) ◽  
pp. 321-326 ◽  
Author(s):  
L. R. Glicksman ◽  
J. Azzola ◽  
J. Modlin
Keyword(s):  
Heat Transfer ◽  
Power Consumption ◽  
Fluidized Bed ◽  
Solar Collector ◽  
Effective Conductivity ◽  
Thermal Design ◽  
Low Density ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Order Of Magnitude

An air fluidized bed, contained in the wall cavity of an exterior building wall, forms the basis of a new solar collector design which is simpler than a water-cooled collector and has a thermal performance superior to that of an air-cooled collector. The fluidized bed serves as an intermediate heat transfer medium between a solar flux absorbed on the external building surface and a liquid thermal transfer loop. Fluidized beds yield heat-transfer coefficients an order of magnitude higher than single phase air flow. Low density particles are used in the bed to minimize power consumption. When defluidized, the bed acts as a good thermal insulator. Recent experimental results are presented for the heat-transfer coefficients of the immersed tubes, bounding walls, the effective conductivity of the bed, and the overall full-scale thermal design efficiency for various low density materials. Structural and power consumption performance is examined as well. An integrated fluidized bed solar collector design is proposed and compared with representative water and air collector designs.

scholarly journals Selection of the Design of a Contact Condenser of a Gas-Steam Plant with Steam Injection into the Combustion Chamber

2021 ◽  
pp. 29-34
Author(s):  
Oksana Lytvynenko ◽  
Irina Myhaylova
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Gas Turbines ◽  
Packed Column ◽  
High Heat ◽  
Thermal Design ◽  
Gas Mixture ◽  
Design Calculation ◽  
Transfer Coefficients ◽  
High Heat Transfer

Due to the importance of the problems of implementing energy-saving technologies in modern conditions, one of the promising areas is the use of gas turbines for combined heat and power generation. One of the areas of effective development and technical re-equipment is the widespread use of highly economical combined steam and gas plants and gas turbines. The operation of the gas turbine unit “Aquarius” SE NPCG “Zorya-Mashproekt” with the injection of steam into the combustion chamber, which operates on the advanced cycle A-STIG and has in its circuit equipment for water regeneration, condensed from a vapor-gas mixture is considered. For condensation of steam from the vapor-gas mixture, a contact condenser-gas cooler is used, which is a mixing heat exchanger of complex design. The efficiency of heat transfer is determined by the design of the nozzle, namely, the developed heat transfer surface, small hydraulic supports, high heat transfer coefficients. An important aspect is the overall dimensions, which must be within certain limits. In the work it is offered to execute a design of the condenser in the form of a packed column. Different types of nozzles are considered to choose the best option. As a result of thermal design calculation of the contact capacitor, it is proposed to use Rashiga rings (15152) as a nozzle, which provide the lowest height of the nozzle at the required diameter of the device.

An Experimental Setup for Multiple Air Jet Impingement Over a Surface

2018 ◽  
Author(s):  
Flávia V. Barbosa ◽  
João P. V. Silva ◽  
Pedro E. A. Ribeiro ◽  
Senhorinha F. C. F. Teixeira ◽  
Delfim F. Soares ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Thermal Design ◽  
Test Facility ◽  
Experimental Setup ◽  
Optimized Design ◽  
Transfer Coefficients ◽  
Reflow Soldering ◽  
Air Jet ◽  
High Heat Transfer

Air jet impingement technology receives considerable attention due to its high performance for heat transfer enhancement in thermal equipment, providing high heat transfer rates. Due to its inherent characteristics of high average heat transfer coefficients and uniformity of the heat transfer over the impinging surface, this technology is implemented in a variety of engineering applications and industrial processes, such as reflow soldering, drying of textile, cooling of turbojet engine blades and fusion reactors. Multiple jet impingement involves several variables such as: jets arrangement, jet diameter, nozzle-to-surface distance, nozzle shape, jet-to-jet spacing, jet velocity and Reynolds number, among others. However, the total control of all these parameters is still one of the remarkable issues of the thermal design of jet impingement systems. In some industries that have implemented this technology in their processes, such as reflow soldering, the range of values of these variables are established through empiricism and “trial and error” techniques. To improve the process and to reduce time and costs, it is fundamental to define accurately all the process parameters in order to obtain an optimized design with a high degree of control of the heat transfer over the target surface. To perform an accurate and complete study of the multiple jet impingement variables for a specific application, the development of both experimental and numerical studies is fundamental in order to obtain reliable results. In that sense, this work reports the project and construction of a purpose-built test facility which has been commissioned, using a PIV system. This experimental setup is based on the oven used in the reflow soldering process. The optimization of the multiple jets geometry which is integrated in the experimental setup is herein described and discussed both experimentally and numerically. The numerical simulation of the jet impingement inside the oven was conducted using the ANSYS software, specially designed to predict the fluid behavior. Regarding the relevance of the multiple jet impingement, this work intends to improve the knowledge in this field and to give reliable and scientifically proved answers to the industries that apply this technology in their processes.

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