Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Superheating, upper limit

Increasing superheated steam temperature has the direct result of increased efficiency. For example, an increase in steam temperature of 55°C can give around 4 per cent increase in efficiency. However, in practice the temperature is limited by metallurgical consideration with upper limits of around 540°C. This temperature can also be influenced by the boiler design and the fuel used. [Pg.181]

The temperature dependences of the isothermal elastic moduli of aluminium are given in Figure 5.2 [10]. Here the dashed lines represent extrapolations for T> 7fus. Tallon and Wolfenden found that the shear modulus of A1 would vanish at T = 1.677fus and interpreted this as the upper limit for the onset of instability of metastable superheated aluminium [10]. Experimental observations of the extent of superheating typically give 1.1 Tfus as the maximum temperature where a crystalline metallic element can be retained as a metastable state [11], This is considerably lower than the instability limits predicted from the thermodynamic arguments above. [Pg.131]

Figure 7. Relationship between upper limiting temperature A71 for superheating at which increase in supercooling temperature will begin and average value of supercooling temperature A7hc,un at cooling from a temperature of 7 K lower than ATI. Figure 7. Relationship between upper limiting temperature A71 for superheating at which increase in supercooling temperature will begin and average value of supercooling temperature A7hc,un at cooling from a temperature of 7 K lower than ATI.
The sublimation curve of all substances, so far as yet found, has its upper limit at the melting-point (triple point), although the possibility of the existence of a superheated solid is not excluded. The lower limit is, theoretically at least, at the absolute zero, provided no new phase, e.g. a different crystalline modification, is formed. If the... [Pg.20]

Is there an upper limit for superheating of the nematic phase This temperature would correspond to the second derivative being zero at the non-zero value for S. Setting both the first and second derivatives equal to zero yields... [Pg.252]

Accurate measurements of ATg in ebulliometry and cryoscopy of polymer solutions are made difficult by the small magnitudes of ATg since superheating and supercooling can introduce serious errors. Other practical problems often encountered include separate measurements of Tf and T in cryoscopy, and foaming of the boiling polymer solution in ebulliometry. With curreifi commercial instruments the upper limit for accurate measurement of M is about 5 x 10 gmol . ... [Pg.176]

In the analysis of MARK-I liner failure performed by Theofanous et al. [1990], two basic corium release scenarios have been examined. In one of them a predominantly oxidic corium was assumed, and corium containing mainly metallic phase was considered in the other. The results shown in the above-mentioned report indicate that in either case the probability of liner failure is very low. A common factor in both cases was the assumed low superheat of molten corium. The reasoning behind using Tsup = 70°C as the upper limit for melt superheat was that (especially in the case of high-temperature oxidic corium) the heat transfer between the corium and the reactor vessel would result in the lower head failure, and the subsequent melt release, thus preventing any substantial superheating of the molten corium. [Pg.198]

The boiling point is limited by the critical temperature at the upper end, beyond which it cannot exist as a liquid, and by the triple point at the lower end, which is at the freezing temperature. Between these two limits, if the liquid is at a pressure higher than its boiling pressure, it will remain a liquid and will be subcooled below the saturation condition, while if the temperature is higher than saturation, it will be a gas and superheated. If both liquid and vapour are at rest in the same enclosure, and no other volatile substance is present, the condition must lie on the saturation line. [Pg.4]

The constancy of the critical AT agrees with the equation-of-state explanation of superheated liquids and with the reaction-rate view of nucleation. It means there is an upper temperature limit above which a superheated liquid cannot exist (at a stated pressure) regardless of agitation. [Pg.63]


See other pages where Superheating, upper limit is mentioned: [Pg.131]    [Pg.395]    [Pg.21]    [Pg.9]    [Pg.479]    [Pg.31]    [Pg.4920]    [Pg.353]    [Pg.89]    [Pg.90]    [Pg.511]    [Pg.135]    [Pg.88]    [Pg.192]    [Pg.243]   
See also in sourсe #XX -- [ Pg.90 ]




SEARCH



Superheating

Upper Limit

© 2024 chempedia.info