1,721,295 research outputs found
Spectral remote sensing for furnaces and flames
No full textThe spectral remote sensing (SRS) technique to measure the gas temperature profile in a combustion system is introduced from fundamental concept to lab-size bench test. As the bases of the technique, computationally working models of narrow, band emission in the CO2 4.3 mu-wide band are tested, and inversion algorithms to convert the spectral intensity data into a temperature profile are proposed. Actual applications to three lab-size test benches are made to confirm the practical applicability of the technique. With the latest inversion methods and instruments, the SRS technique can retrieve the temperature profile within a 20-30 K error for peak temperature of 1500 K within seconds. A scheme called BCIM incorporating base function approach and nodal temperature approach is recommended. It is also shown that a pure concentration problem cannot be handled by SRS. However, SRS can be applied to combustion flames thanks to a strong temperature/concentration correlation
Thermal analysis on the letter mark spot of the corvette Cheonan-hit torpedo
No full textDispute is going on over the letter mark on the torpedo that is believed to have sunk the Korean corvette Cheonan in March, 2010. This research is made to investigate if the spot has experienced temperature high enough to burn, which can be proof of later fabrication. Conditions to maximize the heating are introduced and the temperature is calculated numerically as the explosion 'bubble' expands underwater, the gas stream heats the disk front surface and heat is conducted to the letter-written rear surface. Results show less than 20 degrees C rise everywhere in the torpedo propulsion part and essentially no temperature rise on the letter mark over extensive tests. Therefore, the assertion that the letter mark should have been burnt turns out to be fallacious
Parametric Study of the Thermal Performance of a Natural Gas-Fired Furnace, in Industrial Combustion Technologies, Edi. by M.A.Lukasiewicz
No full textCOMPARISON OF ENGINEERING MODELS OF NONGRAY BEHAVIOR OF COMBUSTION PRODUCTS
No full textVarious engineering models of nongray behavior of combustion products are compared with one another for two types of sample problem. The Curtis-Godson approximation method and the weighted-sum-of-gray-gases-model (WSGGM) are used to compute the emission from a Lorentz line in a non-isothermal path, as the first problem. The Milne-Eddington type WSGGM underestimates the effective line width. Secondly, the gray gas model, the WSGGM and the spectral group model (SGM, a modification of WSGGM) are used to solve one-dimensional inhomogeneous slab problems and are compared with the nongray wide band results. The results from both the WSGGM and the SGM are in good agreement with the reference. The result from the gray gas model is significantly away from those of the other models
Stability of a fluid layer with uniform heat generation and convection boundary conditions
No full textConduction/radiation combined heat transfer with contact resistance for application to vacuum insulation
No full textCombined heat transfer of conduction and radiation is investigated with thermal contact resistance boundary condition to scrutinize the effect on heat transfer and to evaluate the thermal performance of vacuum insulation panels (VIPs). Numerical analysis shows that introduction of contact resistance flattens temperature profile and reduces both the conductive and the radiative heat transfer. In VIPs, if interstitial material is purely absorbing/emitting and well contacting the radiation shield, center-of-panel thermal conductivity can be more than twice larger than that estimated by separate analysis of conduction and radiation, especially when the optical thickness of the layer is moderate and the wall emissivity is low. On the other hand, this error decreases with increased scattering albedo and reduced conduction/radiation interaction. In any case, use of low-emissivity shields greatly improves the insulation performance. Further, contact resistance between the interstitial material and the shields reduces the heat transfer substantially. Thus, insulation performance of VIP with artificial core structures can be greatly improved by employing rough or embossed, and highly reflecting shields. (C) 2018 Elsevier Ltd. All rights reserved.
PREDICTION OF THE THERMAL PERFORMANCE OF AN INDUSTRIAL NATURAL GAS-FIRED FURNACE.
No full textA two-dimensional combustion-heat transfer model is used to predict the thermal performance of an industrial natural gas-fired furnace. The flow, combustion and heat transfer model equations are solved numerically using the Simpler algorithm. The physical processes taking place in the furnace are discussed and the numerical results are compared with those based on the gray-gas computations. Local heat fluxes at the load and results of extensive parametric calculations are reported
Measurement of gas temperature profile using spectral intensity from CO2 4 3 mu m band
No full textSpectral remote sensing (SRS) method for determining the temperature profile along a line-of-sight is investigated experimentally Quartz tube, within which combustion gas flows, is used as the test section The inversion procedure is carried out with a line-by line (LBL) method and a CK-based WNB model, The optimal gas temperature profile that minimizes the error between the measured narrow band intensities around the CO2 4 3 mum band and the calculated ones is obtained as the result of the inversion process The gas temperature is also measured with a shielded thermocouple and corrected for the error The results show that the front center and back temperatures are within errors of 1% 4% and 12%, respectively SRS technique shows poor performance in measuring cold gas temperatures behind a hot layer The reconstructed temperature profile in the front region is however in good agreement with the thermocouple reading The potential applicability of SRS is positively demonstrated and current technical limitations are also discussed (C) 2002 Editions scientifiques et medicales Elsevier SAS All rights reserved.This work has been supported by the Critical Technology 21 Project of theMinistry of Science and Technology,Korea and also by a grant from Korea Science and Engineering Foundation (grant No. KOSEF 995-1000-013-2)
- …
