scholarly journals The Effect of Refractory Wall Emissivity on the Energy Efficiency of a Gas-Fired Steam Cracking Pilot Unit

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 880
Author(s):  
Stijn Vangaever ◽  
Joost Van Thielen ◽  
Jeremy Hood ◽  
John Olver ◽  
Petra Honnerovà ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Elevated Temperatures ◽  
Furnace Wall ◽  
Fuel Gas ◽  
Pilot Unit ◽  
Before And After ◽  
Steam Cracking ◽  
High Emissivity

The effect of high emissivity coatings on the radiative heat transfer in steam cracking furnaces is far from understood. To start, there is a lack of experimental data describing the emissive properties of the materials encountered in steam cracking furnaces. Therefore, spectral normal emissivity measurements are carried out, evaluating the emissive properties of refractory firebricks before and after applying a high emissivity coating at elevated temperatures. The emissive properties are enhanced significantly after applying a high emissivity coating. Pilot unit steam cracking experiments show a 5% reduction in fuel gas firing rate after applying a high emissivity coating on the refractory of the cracking cells. A parametric study, showing the effect of reactor coil and furnace wall emissive properties on the radiative heat transfer inside a tube-in-box geometry, confirms that a non-gray gas model is required to accurately model the behavior of high emissivity coatings. Even though a gray gas model suffices to capture the heat sink behavior of a reactor coil, a non-gray gas model that is able to account for the absorption and re-emission in specific bands is necessary to accurately model the benefits of applying a high emissivity coating on the furnace wall.

Spectroscopic Measurements of High Emissivity Materials Using Two-Dimensional Two-Color Thermometry

2004 ◽  
Vol 127 (3) ◽  
pp. 472-477 ◽  
Author(s):  
Yuichiro Tago ◽  
Fumie Akimoto ◽  
Kuniyuki Kitagawa ◽  
Norio Arai ◽  
Stuart W. Churchill ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Optical Filters ◽  
Bandpass Filters ◽  
Temperature Measurements ◽  
Two Dimensional ◽  
Heating Furnaces ◽  
A Charge ◽  
High Emissivity

Radiative heat transfer characteristics from the surface of a substance coated with a high-emissivity material have been examined from the measured two-dimensional (2D) temperature distribution using two-color thermometry principle. The technique utilized a charge coupled device camera and optical filters having either wide or narrow wavelength bandpass filters. The results obtained were compared to evaluate the accuracy of the temperature measurements. The 2D emissivity distributions were also derived from the measured 2D temperature distributions. The results indicate that the substrate coated with high-emissivity material exhibit high emission of radiation, resulting in effective cooling. The enhanced emissivity of materials also results in improved radiative heat transfer in heating furnaces and other high-temperature applications. The emissivity measured with the wide-bandpass filters increased with temperature. Atmospheric absorption, mainly due to humidity, made a negligible contribution to the total spectral intensity and to the temperature measurements. The small discrepancies are attributed to the dependence of emissivity on wavelength. Thus, the use of narrow-bandpass filters in thermometry is advantageous over the wide-bandpass ones.

Using Infrared Thermography for Detecting Defects on Surfaces With Low and Variable Emissivity

2009 ◽  
Author(s):  
Christopher Dalton ◽  
Brandon Olson ◽  
Feng C. Lai
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Performance Enhancement ◽  
System Development ◽  
Computer Software ◽  
Infrared Scanning ◽  
Transfer Equations ◽  
Infrared Cameras ◽  
High Emissivity

Currently infrared scanning technology has been successfully applied for the detection of a wide variety of defects in many applications provided that the surfaces have a high emissivity that doesn’t reflect radiation from outside sources. However, surfaces with low and variable emissivity present a challenge for the application of this technology because infrared cameras and sensors cannot differentiate between the emitted radiation from the surface of interest and those reflected from outside sources. The system presented is an attempt to reduce and/or remove the effects of reflected radiation to increase the system’s applicability beyond the limit of high emissivity surfaces. Physical hardware and computer software are used in concert with radiative heat transfer equations to first determine the emissivity of each point on the surface, then use that information obtained to accurately depict the surface temperature. While this newest iteration of the system development has addressed many important issues regarding accuracy, efficiency as well as performance enhancement in the removal of the artifacts of reflected radiation, the technique still has difficulties to be applied to most surfaces with variable emissivity.

An Instrument for Local Radiative Heat Transfer Measurement Around a Horizontal Tube Immersed in a Fluidized Bed

1990 ◽  
Vol 112 (2) ◽  
pp. 486-491 ◽  
Author(s):  
N. Alavizadeh ◽  
R. L. Adams ◽  
J. R. Welty ◽  
A. Goshayeshi
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Horizontal Tube ◽  
Total Heat ◽  
Total Heat Transfer ◽  
Bed Temperature ◽  
Before And After ◽  
Transfer Measurement

An instrument for the measurement of the radiative component of total heat transfer in a high-temperature gas fluidized bed is described. The main objective of this paper is to emphasize the design, instrumentation, and calibration of this device. The results are presented and discussed elsewhere (Alavizadeh, 1985; Alavizadeh et al., 1985). The design makes use of a silicon window to transmit the radiative heat flux to a thermopile-type heat flow detector located at the base of a cavity. The window material thermal conductivity is sufficiently large to prevent conduction errors due to the convective component of total heat transfer. Also, its transmission and mechanical hardness are well suited for the fluid bed environment. The device has been calibrated using a blackbody source both before and after exposure to a fluidized bed, indicating the effect of the abrasive bed environment on performance. The instrument has been used to measure local radiative heat transfer around a horizontal tube. Typical results for a particle size of 2.14 mm and a bed temperature of 1050 K are presented and discussed to illustrate instrument performance.

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