“…The ICP-AES data showed an initial rapid increase in concentration of corrosion products in the melt during the first 200 h followed by little further increase until 800 h exposure, when rapid attack commenced (with spalling) until 1200 h; another passive period followed until 1700 h and then further attack, with spalling, until the run was terminated after 2000 h. A generalized outline is shown in Figure 6. These results have been published (2).…”
“…There are essentially three distinct high temperature corrosion problems in fossil fuel steam boilers: (1) Fireside corrosion of the steam-containing superheater and reheater tubes due to the deposition of fuel impurities from the flue gas at its highest temperature. (2) Fireside corrosion of the tubes containing water located in the furnace enclosure, and…”
“…The ICP-AES data showed an initial rapid increase in concentration of corrosion products in the melt during the first 200 h followed by little further increase until 800 h exposure, when rapid attack commenced (with spalling) until 1200 h; another passive period followed until 1700 h and then further attack, with spalling, until the run was terminated after 2000 h. A generalized outline is shown in Figure 6. These results have been published (2).…”
“…There are essentially three distinct high temperature corrosion problems in fossil fuel steam boilers: (1) Fireside corrosion of the steam-containing superheater and reheater tubes due to the deposition of fuel impurities from the flue gas at its highest temperature. (2) Fireside corrosion of the tubes containing water located in the furnace enclosure, and…”
“…Wang [30] notes that in the case of a continuous casting solid flux film photon transfer accounts for 73% of the total heat transmission to the mould. However, the question of the influence of photon conductivity on the structure of heat balances in liquid slags and fluxes has largely been neglected with work on the topic generally focussed on the alternative of relating the phonon conductivity to the chemical structure of the liquid concerned [35,61,62]. Figure 1. Transmission spectrum of CaF 2 .…”
Section: Heat Transfer In Liquid Slagsmentioning
confidence: 99%
“…Hence the presence of a significant concentration of Fe 2+ for example would reduce the overall ability of the slag to transfer heat by photon conduction. Measurements on lower temperature systems [62] suggest that this effect would strongly reduce photon transfer at Fe 2+ concentrations approaching 1 wt-% which would be unusual, but not unknown, in a modern ESR system. A study on the optical properties of a liquid silicate glass in the temperature range of 1400–1600°C [69] found a decrease in effective heat transfer coefficient from 60 to 80 W m −1 K −1 for clear glass to 10–20 W m −1 K −1 with the addition into the glass of small contents of iron in the range of 0.5–1 wt-%.…”
The extensively published models of the ESR process assume a singular value of the slag thermal conductivity and employ that value in a format which assumes heat conduction entirely by a phonon mechanism. In this work we investigate the possibility that the mechanism is a phonon/ photon mechanism in a slag which is diathermanous. The conclusion is that such a model assumption better represents the practical behaviour of the process and should be used in model structures. It is also suggested that the concept has a wider application to other metallurgical processes which use slags having some degree of photon conductivity.
“…Determining the degree of improvement requires measurement of the absorption coefficient in the spectral range of interest. Unfortunately, traditional spectroscopic methods are ill-suited for work with molten salts: Direct transmittance measurements overestimate absorption if they do not capture backscattering, and many window materials are prone to corrosive attack by these 1 molten salts [18]. Another strategy to employ would be attenuated total reflectance spectroscopy [19]; but, here again, owing to the close contact between the reflecting prism and liquid, material compatibility renders this method impractical.…”
This study describes the development and characterization of novel high-temperature thermal storage media, based on inclusion of transition metal chlorides in the potassium–sodium chloride eutectic system, (K–Na)Cl (melting temperature of 657 °C, latent heat of 278 J/g). At the melting temperature of (K–Na)Cl, infrared (IR) radiation can play a major role in the overall heat transfer process—90% of spectral blackbody radiation falls in the range of 2–13 μm. The authors propose inclusion of small amounts (less than 0.2 wt.%) of IR-active transition metal chlorides to increase radiative absorption and thereby enhance heat transfer rates. A new IR-reflectance apparatus was developed to allow for determination of the spectral absorption coefficient of the newly formulated phase-change materials (PCMs) in the molten state. The apparatus consisted of an alumina crucible coated at the bottom with a reflective (platinum) or absorptive (graphite) surface, a heated ceramic crucible-holder, and a combination of zinc sulfide (ZnS) and zinc selenide (ZnSe) windows for containment of the salt and allowance of inert purge gas flow. Using this apparatus, IR spectra were obtained for various transition metal chloride additives in (K–Na)Cl and improved IR activity, and radiative transfer properties were quantified. Further, thermophysical properties relevant to thermal energy storage (i.e., melting temperature and latent heat) are measured for the pure and additive-enhanced thermal storage media.
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