Numerical Simulation of Heat Transfer in a 3D Cavity-Receiver

2015 ◽  
Author(s):  
Parthasarathy Pandi ◽  
Patrick Le Clercq
Keyword(s):  
Material Properties ◽  
Measurement Data ◽  
Power Input ◽  
Momentum Equation ◽  
Process Models ◽  
Conductive Heat ◽  
Recirculating Flow ◽  
Radiative Power ◽  
Ceria Reduction ◽  
Energy Equations

The unsteady 3D fluid flow coupled to radiative, convective, and conductive heat transfers are computed within a cavity-receiver that was successfully tested experimentally. A Monte-Carlo radiation model is used in the fluid regions of the reactor with source terms outside the cavity’s window to account for the concentrated radiative power input. Darcy’s law for the viscous regime and the Forchheimer’s term for the inertial regime are used in the momentum equation to account for the pressure drop within the porous region (RPC). Two separate energy equations for the solid and for the fluid regions of the porous domain are solved in order to capture the non-equilibrium effects in that region. Rosseland diffusion approximation is used in the solid regions of the RPC domain. The material properties and boundary conditions were taken from published experimental measurements. The simulation results are compared to the measurement data collected during the pre-heating and the ceria reduction phases, which sum up to four different radiative power inputs. Results of the comparison are very good and constitute the verification that the numerical methods, physical sub-process models and material properties are adequately selected and implemented. An analysis regarding the heat balance, the recirculating flow and, the effect of dual-scale porosity is also presented.

A Modular Ceramic Cavity-Receiver for High-Temperature High-Concentration Solar Applications

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
I. Hischier ◽  
P. Poživil ◽  
A. Steinfeld
Keyword(s):  
High Temperature ◽  
Material Properties ◽  
Gas Turbines ◽  
Power Input ◽  
Model Coupling ◽  
Transfer Model ◽  
High Concentration ◽  
Compound Parabolic Concentrator ◽  
Radiative Power ◽  
Reflective Coatings

A high-temperature pressurized air-based receiver is considered as a module for power generation via solar-driven gas turbines. A set of silicon carbide cavity-receivers attached to a compound parabolic concentrator (CPC) are tested on a solar tower at stagnation conditions for 35 kW solar radiative power input under mean solar concentration ratios of 2000 suns and nominal temperatures up to 1600 K. A heat transfer model coupling radiation, conduction, and convection is formulated by Monte Carlo ray-tracing, finite volume, and finite element techniques, and validated in terms of experimentally measured temperatures. The model is applied to elucidate the effect of material properties, geometry, and reflective coatings on the cavity’s thermal and structural performances.

scholarly journals Modeling of Ceria Reduction in a Solar Thermochemical Reactor via DEM Method

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Han Zhang ◽  
Joseph D. Smith ◽  
Keyword(s):  
Gas Flow ◽  
Three Dimensional ◽  
Textural Properties ◽  
Power Input ◽  
Reduction Reaction ◽  
Wide Range ◽  
Radiative Power ◽  
Solar Thermochemical ◽  
Ceria Reduction ◽  
Ceo2 Reduction

Solar thermochemical reactor provides an attractive approach that utilizes the most common solar radiation as the thermal driving force to motivate the reaction between CO2 and metal oxides, which is also called metal oxide redox pair-based thermochemical cycles. The CeO2/CeO2-δ is widely used in the two-step redox process due to its advantages including fast-redox kinetics, high crystallographic stability of a wide range of reacting oxygen non-stoichiometry, and relatively high oxygen solid-state conductivity. In this work, a three-dimensional transient numerical analysis has been completed to study the performance of a CeO2 reduction reaction in a 1/8th segment region of a novel partition cavity-receiver reactor. The porous CeO2 catalyst was analyzed using the discrete element method (DEM) to capture the heat transfer and reactive performances. The catalyst textural properties (particle size and void fraction) and reaction conditions (gas flow rate and radiative power input) were investigated in the CeO2 reduction reaction. The results indicated that increasing the catalyst specific surface area and the temperature are beneficial to the O2 production and further CO2 conversion.

A Finite Volume Analysis of the Thermohydrodynamic Performance of Finite Journal Bearings

1990 ◽  
Vol 112 (3) ◽  
pp. 557-565 ◽  
Author(s):  
T. Han ◽  
R. S. Paranjpe
Keyword(s):  
Finite Volume ◽  
Numerical Scheme ◽  
Reverse Flow ◽  
Journal Bearings ◽  
Simultaneous Solution ◽  
Volume Analysis ◽  
Recirculating Flow ◽  
Supply Pressure ◽  
Good Sample ◽  
Energy Equations

A rigorous thermohydrodynamic (THD) analysis of finite journal bearings has been developed. THD analysis not only allows a more accurate prediction of the bearing performance characteristics, but it also provides the temperature distribution in the bearing. It involves the simultaneous solution of the Reynolds and energy equations and can handle a wide variety of flow situations, including reverse flow, recirculating flow, and cavitation. The overall numerical scheme is based on a fully conservative finite-volume formulation. The calculated results are compared with the published literature. The qualitative agreement is good. Sample calculations for a typical automotive bearing show that the oil supply pressure and supply configuration significantly affect the bearing performance.

Asymptotic Model of Free Convection Flow on a Vertical Surface in Porous Media with Newtonian Heating

2015 ◽  
Vol 756 ◽  
pp. 469-475
Author(s):  
Anna A. Bocharova ◽  
Irina V. Plaksina ◽  
Andrey A. Obushnyy
Keyword(s):  
Mathematical Model ◽  
Porous Media ◽  
Free Convection ◽  
Vertical Surface ◽  
Momentum Equation ◽  
Convection Flow ◽  
Asymptotic Model ◽  
Free Convection Flow ◽  
Energy Equations ◽  
The Mathematical Model

The mathematical model based on system of momentum and energy equations for free convection flow along a vertical surface in porous media under boundary conditions of the third sort is solved analytically using the method of matched asymptotic expansions. The region of validity for boundary layer model and expansions for stream function and temperature with parameter of perturbations were defined. The dependence of characteristic flow from governing dimensionless parameters and was analyzed numerically. The influence of viscous and convective terms of momentum equation in the proposed mathematical model significantly increases the rate of heat transfer on plate in porous media in comparison with Darsy flow model.

MEMS Die Warpage During Curing of Die Attach Material

2015 ◽  
Author(s):  
Hohyung Lee ◽  
Ruiyang Liu ◽  
Seungbae Park ◽  
Xiaojie Xue
Keyword(s):  
Material Properties ◽  
Residual Strain ◽  
Critical Role ◽  
Measurement Data ◽  
Curing Process ◽  
Assembly Process ◽  
Structural Elements ◽  
Mems Sensor ◽  
Fea Model ◽  
Die Attach

Microelectromechanical system (MEMS) packages are vulnerable to stresses due to its functional structure. During the assembly process of the package, stresses stemming out of CTE mismatches of the structural elements and curing of the die attach material can cause warpage of the MEMS die [1]. Even though die attach material takes relatively small volumetric portion of the package, it plays a critical role in warpage of the die due to its location and sensitivity of a MEMS sensor. Most of virgin die attach adhesives are in a state of viscous liquid and, as it is cured the material properties such as modulus and CTE change. Accordingly, residual strain is cumulated on MEMS die after curing process and signal trim process is required. Therefore, the material properties changes depending on the curing profile is valuable information for assembly process of the MEMS package. To monitor the material properties changes and shrinkage during curing process, strain and modulus of a die attach material are measured in each curing step. Also, to investigate the material property change depending on the curing profile, two different curing profiles are used. Experimental data show that die attach materials are gradually cured after each thermal cycling, which cause the increment of the modulus and glass transition temperature (Tg) with shrinkage at elevated temperature. Using the measurement data, FEA model is built to predict the warpage of the MEMS die. In the FEA model, residual strain on MEMS die is calculated by inputting material properties of die attach in each curing step. Also, die warpage of the package during the curing process is monitored using an optical profiler for the validation of the simulation results.

scholarly journals Overview of combustion process models in a cylinder of piston engine

2018 ◽  
Vol 19 (4) ◽  
pp. 48-52
Author(s):  
Dominika Cuper Przybylska
Keyword(s):  
Diesel Engine ◽  
Fluid Mechanics ◽  
Combustion Process ◽  
Measurement Data ◽  
Process Models ◽  
Mass Movements ◽  
Piston Engine ◽  
Reliable Measurement ◽  
3 Dimensional ◽  
Physical Phenomena

The article presents an overview of models used to calculate combustion process parameters in piston engines. One of the applied techniques is modelling based on the mathematical description of physical phenomena. The level of complexity of such a description depends, however, on the purpose of the model, the efficiency of calculations and the possibility of obtaining reliable measurement data. The paper presents various methods of modelling phenomena occurring in the cylinder of a Diesel engine. Presented are assumptions and effects of modelling using models from 0-dimensional and single-zone to complex 3-dimensional models, describing the phenomena of turbulent mass movements using computer fluid mechanics.

scholarly journals Modeling an RF Cold Crucible Induction Heated Melter With Subsidence

2004 ◽  
Author(s):  
Grant Hawkes
Keyword(s):  
Vector Potential ◽  
Molten Glass ◽  
Melting Process ◽  
Power Input ◽  
Magnetic Vector Potential ◽  
Cold Crucible ◽  
Magnetic Vector ◽  
Melt Temperature ◽  
Experimental Apparatus ◽  
Energy Equations

A method to reduce radioactive waste volume that includes melting glass in a cold crucible radio frequency induction heated melter has been investigated numerically. The purpose of the study is to correlate the numerical investigation with an experimental apparatus that melts glass in the above mentioned melter. Unique to this model is the subsidence of the glass as it changes from a powder to molten glass and drastically changes density. A model has been created that couples the magnetic vector potential (real and imaginary) to a transient startup of the melting process. This magnetic field is coupled to the mass, momentum, and energy equations that vary with time and position as the melt grows. The coupling occurs with the electrical conductivity of the glass as it rises above the melt temperature of the glass and heat is generated. Natural convection within the molten glass helps determine the shape of the melt as it progresses in time. An electromagnetic force is also implemented that is dependent on the electrical properties and frequency of the coil. This study shows the progression of the melt shape with time along with temperatures, power input, velocities, and magnetic vector potential. Coupled to all of this is a generator that will be used for this lab sized experiment. The coupling with the 60 kW generator occurs with the impedance of the melt as it progresses and changes with time. A power controller has been implemented that controls the primary coil current depending on the power that is induced into the molten glass region.

Warpage Analysis of Panelized Molding Process for Plastic IC Packages

2004 ◽  
Author(s):  
Bhuvaneshwaran Vijayakumar ◽  
Yifan Guo
Keyword(s):  
Material Properties ◽  
Large Range ◽  
Low Cost ◽  
Measurement Data ◽  
Ball Grid Array ◽  
Element Model ◽  
Molding Process ◽  
Plastic Ball ◽  
Plastic Ball Grid Array ◽  
Simulation Results

Panelized molding process is vastly used in low cost molding process for PBGA (Plastic Ball Grid Array), LGA (Land Grid Array), QFP (Quad Flat Pack) and other types of packages. In a panelized molding process, arrays of packages are assembled on a substrate board, which is then molded as a single panel. After the molding process, the package array is cut into single packages. When laminated substrates are used, panel warpage formed during the molding process is very common due to the mismatches of material properties in the substrates and molding compounds. The warpage, however, is one of the major issues in the back-end assembly process. For example, the warpage can cause great difficulties in singulation. Large warpage could also cause high stresses in the components and results in reliability problems in the packages. In this paper, a 3-D finite element model is created to study the relations between the panel warpage and the material properties of the substrate boards and mold compounds. In a 40mmx50mm panel area, the model shows that the global warpage can be as high as +/-10 mils (0.25 mm) using different mold compounds. Test vehicles are assembled to validate the simulation results. The measurement data on warpage from the testing vehicles, although at first seems to vary over a large range across different panel designs, a closer observation and analysis suggests a definite trend and a strong correlation between the substrate panel and the mold compound properties.

Sign in / Sign up

Export Citation Format

Share Document