Temperature adjustment, scale

A combination of jacket zoning and aspect ratio adjustment is used to provide a scale-up reactor that performs temperature adjustment steps in the same time as the pilot scale unit [14], From Equation 13-27... 

In specifying the number of jacket zones and the aspect ratio for a full-scale reactor, there is a limitation on the temperature adjustment time. This implies that it must be of the same duration as experienced in the pilot plant reactor. Combining Equations 13-89 and 13-97 yields... 

Substituting X2 into Equations 13-67, 13-49, and 13-50, it is possible to determine the effect of scale-up on the jacket outlet temperature and the time required in completing the temperature adjustment step. In directly predicting the expected value for the outlet temperature t2 from the jacket of a reactor scaled-up by some volume scale-up factor SUFV, substitute Equation 13-58 into form II of Equation 13-67. This gives... 

The cooling time in a full-scale batch reactor is 1.27 hr, which is approximately 49% more than the 0.85 hr predicted at the smaller scale. Multiple temperature adjustment steps occur in a chemical reactor production cycle. The sum of these cycle time increases may be significant, and the plant capacity at the larger scale may be adversely affected if the cycle times are not corrected [13], An Excel spreadsheet (EXAMPLE 13-2.xls) was developed for Example 13-2. 

The time required to complete a cooling temperature adjustment step for the full-scale reactor is ... 

Ideal-gas tables of thermodynamic properties derived from statistical mechanics are based on the thermodynamic temperatures (as well as on the values of the physical constants used) and are hence independent of any practical temperature scale. The enthalpy of formation, Gibbs energy of formation, and logarithm of the equilibrium constant might depend on temperature-adjusted data. 

The power-loss meter is the most common type of dielectric moisture meter. It senses the product of the dielectric constant and loss factor. Generally, the loss factor increases with wood moisture content but may exhibit variations from this behavior depending on the frequency of measurement (JO, 11, 14). An increase in temperature produces effects similar to increasing moisture content, with interaction between these two parameters. Therefore, temperature adjustments of meter readings are complex, sometimes increasing and sometimes decreasing the scale reading as temperature increases... 

The polymer molecular weight is the most important factor determining the viscosity of melts. The scaling rule is tj In many cases a solution viscosity (for example, intrinsic viscosity, [ ]) is used as a measure for polymer molecular weight. Since for many flexible polymers [//] we can derive another scaling rule, of melt viscosity as a function of solution viscosity tj It is evident that a higher melt temperature will reduce melt viscosity, but only small variations in molecular weight can be compensated for by temperature adjustment. 

In a molecular dynamics calculation, you can add a term to adjust the velocities, keeping the molecular system near a desired temperature. During a constant temperature simulation, velocities are scaled at each time step. This couples the system to a simulated heat bath at Tq, with a temperature relaxation time of "r. The velocities arc scaled bv a factor X. where... 

If the thermometer is to be used to determine the elevation of the boiling-point of a liquid on the addition of a solute, it must be remembered that at the boiling-point of the pure solvent the mercury must now be about 1-2 above the bottom of the scale S, and hence for adjustment purposes the temperature of the beaker of water should be 6—7 above the boiling-point of the liquid itself, instead of 1-2 as before. 

One of the disadvantages of oil and metal baths is that the reaction mixture cannot be observed easily also for really constant temperatures, frequent adjustment of the source of heat is necessary. These difficulties are overcome, when comparatively small quantities of reactants are involved, in the apparatus shown in Fig. II, 5,4 (not drawn to scale). A... 

These calculations can incorporate various types of constraints. It is most common to run simulations with a hxed number of atoms and a hxed volume. In this case, the temperature can be computed from the average kinetic energy of the atoms. It is also possible to adjust the volume to maintain a constant pressure or to scale the velocities to maintain a constant temperature. 

The KTTS depends upon an absolute 2ero and one fixed point through which a straight line is projected. Because they are not ideally linear, practicable interpolation thermometers require additional fixed points to describe their individual characteristics. Thus a suitable number of fixed points, ie, temperatures at which pure substances in nature can exist in two- or three-phase equiUbrium, together with specification of an interpolation instmment and appropriate algorithms, define a temperature scale. The temperature values of the fixed points are assigned values based on adjustments of data obtained by thermodynamic measurements such as gas thermometry. 

A worker was told to control the temperature of a chemical reaction at 60° C he adjusted the setpoint of the leiiijier.ilure controller to be 60. The scale indicated 0-100% of a temperature range of 0-200 C. so tlie sci point was is. iliv 1 -O C A runaway reaction resulted which overpressured the vessel. Discharged liquid iirul injured il e worker. 

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