Design Studies for a Solar Reactor Based on a Simple Radiative Heat Exchange Model

2005 ◽  
Vol 127 (3) ◽  
pp. 425-429 ◽  
Author(s):  
C. Wieckert
Keyword(s):  
Heat Transfer ◽  
Solar Power ◽  
Radiation Heat Transfer ◽  
Heat Transfer Analysis ◽  
Physical Parameters ◽  
Concentrated Solar Power ◽  
Radiation Heat ◽  
Small Aperture ◽  
Lower Cavity ◽  
Solar Reactor

A high-temperature solar chemical reactor for the processing of solids is scaled up from a laboratory scale (5kW concentrated solar power input) to a pilot scale (200kW). The chosen design features two cavities in series: An upper cavity has a small aperture to let in concentrated solar power coming from the top. It serves as the solar receiver, radiant absorber, and radiant emitter to a lower cavity. The lower cavity is a well-insulated enclosure. It is subjected to thermal radiation from the upper cavity and serves in our application as the reaction chamber for a mixture of ZnO and carbon. Important insight for the definition of the geometrical parameters of the pilot reactor has been generated by a radiation heat transfer analysis based on the radiosity enclosure theory. The steady-state model accounts for radiation heat transfer within the solar reactor including reradiation losses through the reactor aperture, wall losses due to thermal conduction and heat consumption by the endothermic chemical reaction. Key results include temperatures of the different reactor walls and the thermal efficiency of the reactor as a function of the major geometrical and physical parameters. The model, hence, allows for a fast estimate of the influence of these parameters on the reactor performance.

Analysis to Reduce Thermal Stress in Oxide Single Crystal During Czochralski Growth

2004 ◽  
Author(s):  
Shigeki Hirasawa ◽  
Hiroyuki Ishibashi ◽  
Kazuhisa Kurashige ◽  
Akihiro Gunji
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Temperature Distribution ◽  
Thermal Radiation ◽  
Single Crystal ◽  
Radiation Heat Transfer ◽  
Heat Transfer Analysis ◽  
Czochralski Growth ◽  
Radiation Heat ◽  
Radial Temperature

Temperature distributions and thermal stress distributions in a semi-transparent GSO crystal during Czochralski (CZ) single crystal growth were numerically investigated by thermal radiation heat transfer analysis and anisotropy stress analysis. As GSO has special optical properties, such as semi-transparency at a wavelength shorter than 4.5 μm, thermal radiation heat transfer was calculated by the Monte Carlo method. These calculations showed that thermal stress is caused by the radial temperature distribution on the outside of the upper part of the crystal. To reduce this temperature distribution, the following three manufacturing conditions were found to be effective: use a sharp taper angle of the crystal, install a lid to the top of the insulator, and install a ring around the tapered part of the crystal.

Radiation Heat Transfer Analysis of the Monolith-Type Solid Oxide Fuel Cell

2003 ◽  
Author(s):  
Sunil Murthy ◽  
Andrei Fedorov
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiation Effects ◽  
Radiation Transport ◽  
Radiation Heat Transfer ◽  
Heat Transfer Analysis ◽  
Radiation Heat ◽  
Modeling Framework ◽  
Flux Approximation ◽  
Ysz Electrolyte

In this study, a modeling framework for heat and mass transport is investigated for a unit cell of the monolith type SOFC, with emphasis on quantifying the radiation heat transfer effects. The Schuster-Schwartzchild two-flux approximation is used for treating thermal radiation transport in the optically thin YSZ electrolyte, and the Rosseland radiative thermal conductivity is used to account for radiation effects in the optically thick Ni-YSZ and LSM electrodes. The thermal radiation heat transfer is coupled to the overall energy conservation equations through the divergence of the local radiative flux. A commercially available CFD software was used as a platform for the global thermal-fluid modeling of the SOFC and the radiation models were implemented through the user-defined functions. Results from sample calculations show significant changes in the operating temperatures and parameters of the SOFC with the inclusion of radiation effects.

A Numerical Investigation of Ray Tracing Method in a View Factor Calculation Procedure for Zonal Radiation Heat Transfer in Complex Systems

2009 ◽  
Author(s):  
German Malikov ◽  
Vladimir Lisienko ◽  
Roman Koptelov ◽  
Jakov Kalugin ◽  
Raymond Viskanta
Keyword(s):  
Heat Transfer ◽  
Ray Tracing ◽  
Direct Method ◽  
Radiation Heat Transfer ◽  
Three Dimensional ◽  
Heat Transfer Analysis ◽  
View Factor ◽  
Radiation Heat ◽  
Zonal Method ◽  
Metallurgical Furnaces

In this paper a variety of well known computer graphics algorithms (Binary Spatial Partitioning-BSP, Bounding Box-BB, and direct method of sequential search) for ray tracing are studied numerically in the context of the view factor calculations for the zonal method of radiation heat transfer analysis in complex industrial furnace geometries. The paper reports on a modified BSP algorithm which takes into account the specific types of obstructions and their arrangement in different types of metallurgical furnaces. The modified algorithm enhances the ray tracing calculations by two to three orders of magnitude. An universal algorithm to obtain an intersection with a polyhedron obstruction is developed. The method is tested for simple three dimensional and complex furnace geometries.

Numerical Study of Radiation Heat Transfer for a Supercritical CO2 Turbine Linear Cascade

2019 ◽  
Author(s):  
Akshay Khadse ◽  
Andres Curbelo ◽  
Jayanta S. Kapat
Keyword(s):  
Heat Transfer ◽  
Absorption Coefficient ◽  
Supercritical Co2 ◽  
Cooling System ◽  
Radiation Heat Transfer ◽  
Heat Transfer Analysis ◽  
Inlet Temperature ◽  
Radiation Heat ◽  
Linear Cascade ◽  
Wide Range

Abstract The fundamental research and technology development for supercritical CO2 (sCO2) power cycles is gaining worldwide popularity. This is due to their promise of high efficiency, compactness, wide-range-applicability and eco-friendliness. One of the active research areas in the sCO2 power cycle field is to increase cycle efficiency by utilizing a higher turbine inlet temperature. At high temperatures within turbines, radiation may contribute a significant portion of overall heat transfer. The purpose of this paper is to investigate and quantify the effects of radiation heat transfer within a first stage sCO2 turbine linear cascade. This particular topic has not been explored by researchers yet. The correct estimation of radiation heat transfer can prove to be critical for the design of turbine blade cooling system. The aerodynamic and heat transfer analysis of a turbine cascade is carried out using a commercial computational code, STAR-CCM+. Spectral absorption coefficient for CO2 is derived using HITRAN database at required temperature and pressure. Broadening and shifting of intensity lines due to high pressure and temperature are taken into consideration. A second approach utilizes Planck mean absorption coefficient as a function of temperature. Although the data can be extrapolated for the required higher pressure, accuracy of that extrapolated data cannot be verified. Hence the secondary purpose of this study is to encourage researchers to fill the fundamental gaps in the knowledge of CO2 radiation. Findings presented here suggest that radiation can be neglected for cooling system design of the sCO2 turbine stage 1 vane for both inlet temperatures of 1350K and 1775K.

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