Relative temperature index maximum

Over the years many attempts have been made to provide some measure of the maximum service temperature which a material will be able to withstand without thermal degradation rendering it unfit for service. Quite clearly any figure will depend on the time the material is likely to be exposed to elevated temperatures. One assessment that is being increasingly quoted is the UL 746B Relative Temperature Index Test of the Underwriters Laboratories (previously known as the Continuous Use Temperature Rating or Index). 

The temperature at which the threshold is reached in (usually) 20,000 hours is called the Temperature Index (TI) in ISO 2578. The Relative Temperature Index (RTI) is a comparative value with a reference material. The HIC is the halving interval - the temperature change needed to halve the time to the end point from TI. MCUT is the Maximum Continuous Use Temperature which is normally based on 100,000 hours. One criticism of MCUT and similar measures is that the changes in properties are made at... 

RTI Relative thermal index (formerly named continuous-use temperature) is the maximum service temperature at which the critical properties of a material will remain within acceptable limits over a long time, as established by UL 746B. There can be up to three independent RTI ratings assigned to a material ... 

Dow Fire and Explosion Index. The Dow Eire and Explosion Index (3) is a procedure usehil for determining the relative degree of hazard related to flammable and explosive materials. This Index form works essentially the same way as an income tax form. Penalties are provided for inventory, extended temperatures and pressures, reactivity, etc, and credits are appHed for fire protection systems, process control (qv), and material isolation. The complete procedure is capable of estimating a doUar amount for the maximum probable property damage and the business intermptionloss based on an empirical correlation provided with the Index. 

D. R. Stull11 developed a rating system to establish the relative potential hazards of specific chemicals the rating is called the reaction hazard index (RHI). The RHI is related to the maximum adiabatic temperature reached by the products of a decomposition reaction. It is defined as... 

The Meteorological environment is evaluated by four indicators including daily maximum temperatures, daily minimum temperatures, relative humidity and Pollution meteorological condition. Specially, the index of pollution meteorological condition reflects... 

In fig.2 the red-shifts ( in cm" ) of spheroidene in different solvents relative n-hexane (A = i (hM) - (soiv)) are plotted against the refractive index term (n - l)/(n + 2), where n is the refractive index of the solvent. The shifts were calculated from the maximum absorbance peak. The circular dots are from measurements of spheroidene in CS with temperatures between -5 C and -99 °C. The refractive index increases linearly with decreasing temperature. In fig. 2 we see that Lv is linear function of (n -l)/(n ... 

There are other methods that predict reactivity more reliably than the oxygen balance method. These methods, however, require the use of data generated by measurements. Stull devised a relatively simple Reaction Hazard Index or RHI that used both kinetic and thermodynamic data measurements. This index is a graphic model (nomagraph) that uses the Arrhenius activation energy and the decomposition temperature The latter term is the maximum adiabatic temperature reached by the products of a decomposition reaction. If data are available or can be measured, the RHI may be a very useful method to predict reactivity. Coffee described a method that predicts the explosive potential of a compound using thermal stability (measured), impact sensitivity (measured), and the heat of reaction (calculated). Compounds found to be thermally unstable and sensitive to impact were explosive. 

The weak maximum principle can certainly be used to maximize the performance index of Eq. 13.33, for instance, for the independent deactivation problem given by Eqs. 13.40 through 13.45 with the addition of a heat balance at the pellet-bulk fluid interface for the pellet surface temperature 7 [( )s]. Nevertheless, the optimal inlet temperature will be a function of time. Thus, the inlet temperature is to be manipulated in a prescribed manner in time without any regard to what happens to the reactor. This open-loop control is rarely practiced in actual applications because of the uncertainties regarding the model, measurements, and disturbances. Rather, closed-loop control using feedback from the process is usually practiced. This fact should not discourage one from using the maximum principle for optimization, for it will at least indicate what the best possible performance is in a relative sense. At the same time it can yield in some simple cases a very powerful optimal policy such as the constant conversion policy, which can be implemented by a feedback control scheme. 

---