Radiation Heat Transfer in a Spherical Enclosure Containing a Participating, Heat-Generating Gas

1961 ◽  
Vol 83 (2) ◽  
pp. 199-206 ◽  
Author(s):  
E. M. Sparrow ◽  
C. M. Usiskin ◽  
H. A. Hubbard
Keyword(s):  
Integral Equation ◽  
Radiation Heat Transfer ◽  
The Other ◽  
Gas Temperature ◽  
Radiation Heat ◽  
Energy Principle ◽  
Conservation Of Energy ◽  
Concentric Spheres ◽  
Wide Range ◽  
Enclosure Size

An analysis is made of the thermal radiation in an absorbing-emitting nonisothermal gas confined in a hollow spherical enclosure or in the space between two concentric spheres. The gas is gray and contains a volume heat source, while the bounding walls are black and isothermal. The conservation of energy principle yields an integral equation which has been solved for a wide range of geometric and radiative conditions. It is found that as the absorption coefficient increases in a fixed geometry, the gas temperature decreases and becomes more nonuniform. On the other hand, as the enclosure size increases, the gas temperature increases and becomes more nonuniform. An approximate analysis using a conduction-type transfer law has been carried out, and the results are compared with the integral equation solutions.

A Simplified Thermal Model and Comparison Analysis for a Stratospheric Lighter-Than-Air Vehicle

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Wei Zheng ◽  
Xiangyi Zhang ◽  
Rong Ma ◽  
Yong Li
Keyword(s):  
Thermal Model ◽  
Radiation Heat Transfer ◽  
Simplified Model ◽  
Full Model ◽  
Gas Temperature ◽  
Radiation Heat ◽  
Flight Data ◽  
Comparison Results ◽  
Inner Surface ◽  
Transient Thermal

Transient thermal behavior modeling and simulation is a key issue in predicting flight performance of stratospheric lighter-than-air (LTA) vehicles, such as airships or balloons. To reduce computational load of the transient thermal model without significant loss of accuracy, first this paper adopted an analytical model of view factor from the element surfaces to the Earth and constructed a full distributed parameter transient thermal model. Then, the full model was validated by comparing the predictions obtained from the full model with the flight experimental data. The comparison results show that the divergence of the predicted average internal gas temperatures from the flight data is about 0.4%, and the divergence of the predicted envelop temperatures from the flight data is less than 2.4%. Furthermore, considering that the effect of the net radiation heat transfer among the inner surface enclosure on average internal gas temperature is far less than radiation heat transfer of the outer surfaces, the full model was simplified by omitting radiant heat exchange within the inner surface enclosure. The accuracy of the simplified model was investigated by comparing the predictions of average internal gas temperature and skin temperature distribution between the simplified model and full model under various conditions, such as flight time, altitude, and different external skin thermal properties. The comparison results indicate that the simplified model agrees well with the full model. The discrepancies of the predicted average internal gas temperature between the two models are less than 0.3% under most conditions, and the discrepancies of the predicted temperature distribution between the two models are also acceptable when the LTA vehicle, especially with low absorptivity/emissivity ratio coatings, operates at about 20 km altitude.

Heat Recovery and Burner Modification of an Industrial Tubular Furnace

2015 ◽  
Vol 737 ◽  
pp. 296-300
Author(s):  
Xi Lai Zhang ◽  
Wei Yao
Keyword(s):  
Heat Recovery ◽  
Radiation Heat Transfer ◽  
Exhaust Gas ◽  
Heat Absorption ◽  
Tubular Furnace ◽  
Gas Temperature ◽  
Radiation Heat ◽  
Air Preheater ◽  
Burner Flame ◽  
Exhaust Gas Temperature

The air preheater was installed on the furnace to decrease the exhaust gas temperature and heat the air to about 290°C. A radiant cylinder was added to the radiation section. Swirl flames were formed by adjusting the shape and the installation angles of the burner flame tubes. The radiation heat transfer was strengthened and the heat absorption was enhanced in the radiation section, while the temperature at the outlet of the furnace was decreased. Thus energy was saved by 16.7%.

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.

On the changes in phase speed of one train of water waves in the presence of another

1988 ◽  
Vol 192 ◽  
pp. 97-114 ◽  
Author(s):  
S. J. Hogan ◽  
Idith Gruman ◽  
M. Stiassnie
Keyword(s):  
Integral Equation ◽  
Perturbation Method ◽  
Gravity Waves ◽  
Water Waves ◽  
Phase Speed ◽  
Capillary Waves ◽  
The Other ◽  
Wide Range ◽  
Correct Form ◽  
General Method

We present calculations of the change in phase speed of one train of water waves in the presence of another. We use a general method, based on Zakharov's (1968) integral equation. It is shown that the change in phase speed of each wavetrain is directly proportional to the square of the amplitude of the other. This generalizes the work of Longuet-Higgins & Phillips (1962) who considered gravity waves only.In the important case of gravity-capillary waves, we present the correct form of the Zakharov kernel. This is used to find the expressions for the changes in phase speed. These results are then checked using a perturbation method based on that of Longuet-Higgins & Phillips (1962). Agreement to 6 significant digits has been obtained between the calculations based on these two distinct methods. Full numerical results in the form of polar diagrams over a wide range of wavelengths, away from conditions of triad resonance, are provided.

Thermotunneling Systems for Advanced Efficient Cooling

2009 ◽  
Author(s):  
Mehmet Arik ◽  
Stanton Weaver ◽  
James W. Bray
Keyword(s):  
Heat Transfer ◽  
Power Generation ◽  
Near Field ◽  
Radiation Heat Transfer ◽  
The Other ◽  
Junction Temperature ◽  
Thermodynamic Efficiency ◽  
Dual Use ◽  
Radiation Heat ◽  
Field Radiation

Refrigeration for electronics components has been studied to keep the junction temperature below allowable limits. Thermoelectrics have been investigated heavily for their dual use over the last six decades These devices can be used for both cooling and power generation. Thermotunneling devices, on the other hand, have been known only for the last two decades, and nobody has been able to manufacture or show the performance of those devices. In this study, we will discuss the thermodynamic efficiency of these systems and design bottlenecks to reach high efficiencies, such as thermal back path and electrical losses. Concepts for possible device designs will be discussed. Then attention will be turned to near field radiation heat transfer that becomes critical in nano scale device designs.

2D Color-Intensity Representation of Ultrasonic Thickness Gauge Measurements

2020 ◽  
pp. 1192-1198
Author(s):  
M.S. Mohammad ◽  
Tibebe Tesfaye ◽  
Kim Ki-Seong
Keyword(s):  
Cost Effective ◽  
The Other ◽  
Thickness Gauge ◽  
Color Intensity ◽  
Digital Readout ◽  
Flat Surfaces ◽  
Video Cameras ◽  
Wide Range ◽  
Cost Effective Alternative ◽  
Ultrasonic Thickness

Ultrasonic thickness gauges are easy to operate and reliable, and can be used to measure a wide range of thicknesses and inspect all engineering materials. Supplementing the simple ultrasonic thickness gauges that present results in either a digital readout or as an A-scan with systems that enable correlating the measured values to their positions on the inspected surface to produce a two-dimensional (2D) thickness representation can extend their benefits and provide a cost-effective alternative to expensive advanced C-scan machines. In previous work, the authors introduced a system for the positioning and mapping of the values measured by the ultrasonic thickness gauges and flaw detectors (Tesfaye et al. 2019). The system is an alternative to the systems that use mechanical scanners, encoders, and sophisticated UT machines. It used a camera to record the probe’s movement and a projected laser grid obtained by a laser pattern generator to locate the probe on the inspected surface. In this paper, a novel system is proposed to be applied to flat surfaces, in addition to overcoming the other limitations posed due to the use of the laser projection. The proposed system uses two video cameras, one to monitor the probe’s movement on the inspected surface and the other to capture the corresponding digital readout of the thickness gauge. The acquired images of the probe’s position and thickness gauge readout are processed to plot the measured data in a 2D color-coded map. The system is meant to be simpler and more effective than the previous development.

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