Drying temperature profile

Figure 7.45 Drying monitor probe reads temperature at six different points in the hopper. Maintaining the correct drying temperature profile through the hopper results in proper drying. A change in the profile can warn of problems.

A wide variety of special malts are produced which impart different flavor characteristics to beers. These malts are made from green (malt that has not been dried) or finished malts by roasting at elevated temperatures or by adjusting temperature profiles during kilning. A partial Hst of specialty malts includes standard malts, ie, standard brewers, lager, ale, Vienna, and wheat caramelized malts, ie, Munich, caramel, and dextrine and roasted products, ie, amber, chocolate, black, and roasted barley. 

Figure 5 shows conduction heat transfer as a function of the projected radius of a 6-mm diameter sphere. Assuming an accommodation coefficient of 0.8, h 0) = 3370 W/(m -K) the average coefficient for the entire sphere is 72 W/(m -K). This variation in heat transfer over the spherical surface causes extreme non-uniformities in local vaporization rates and if contact time is too long, wet spherical surface near the contact point dries. The temperature profile penetrates the sphere and it becomes a continuum to which Fourier s law of nonsteady-state conduction appfies. 

Shown in Figure 15.5 are the temperature dependent XRD data for the 5% Pd-1% Sn catalyst. As noted above, the scans were offset in the order that they were obtained (the Time axis, as shown, is the scan sequence number and not the actual temperature). The inset of Figure 15.5 illustrates the temperature profile for the scan sequence. The first scan was obtained at room temperature, at which time hydrogen was introduced into the chamber at 500 Torr. The temperature was then ramped in 10°C increments to 160°C and XRD scans were taken after each increment. The sample was held at 160°C for I/2 hour, and then cooled to room temperature. After I/2 hour at room temperature, the sample was purged with dry nitrogen. 

Barriers to heat transfer produce corresponding temperature differences in a freeze-drying system, the actual temperature profile depending upon the rate of sublimation, the chamber pressure, and the container system as well as the characteristics of the freeze dryer employed. An experimental temperature profile is shown in Figure 5 for a system where vials were placed in an aluminum tray with a flat 5 mm thick bottom and a tray lid containing open channels for escape of water vapor. Here, heat transfer is determined by four barriers ... 

Figure 5 Temperature profile in primary drying of dobutamine HCl-mannitol (1 1), 53 mg solids/mL, 10 mL fill volume. Vials are 5304 molded glass vials (8.3 cm2 cross-sectional area) which are placed in a flat aluminum tray. The heat flux is 42 cal/(cm2 hr), and the chamber pressure is 0.1 torr. (From Ref. 5.)...

Schellenz et al. [ 1.133] confirmed that the assumption of an infinite plate in Eq. (12) is a reasonable approximation, even for drying of products in vials. They show by the measurement of temperature profiles and by X-ray photos during drying of a 5 % mannitol solution, 23 mm filling height, that the sublimation front retreats mostly from the top parallel to the bottom. The heat transfer from glass vials deforms the flat surface only to some extent close to the wall. 

The potential temperatiue 0 is that to which dry air originally in the state (T, p) would come if brought adiabatically to po- Adiabatic temperature profiles expressed in terms of 0 are vertical on a plot of z vs 0, facilitating comparisons of actual temperature profiles to the adiabatic lapse rate. 

FIG. 24-4 Gasifier types and temperature profiles a) fixed bed (dry ash) h) fluidized bed (c) entrained flow. This figure teas published in N. Holt and S. Alpert, Integrated Gasification Combined-Cycle Po-werG vol. 7, pp. 897-905, in Encyclopedia of Physical Science and Technology 3d ed. Copyright Elsevier, 2002.)... 

Describe the reaction engineering of a kitchen toaster. The reactions are thermal drying (which alone makes stale bread) and thermal decomposition and oxidation of starch, which requires temperatures of -300°C. [Recall that the bread appears white until it is nearly done, and then it browns quickly and blackens if left in too long. Recall also that good toast has a brown layer < 1 mm thick while the interior is still white and soft. The control of temperature profiles and heat transfer aspects are essential in producing good toast.]... 

The zinc salt and BaS solutions are mixed thoroughly under controlled conditions (vessel geometry, temperature, pH, salt concentration, and stirring speed, see (a) in Fig. 20). The precipitated raw lithopone does not possess pigment properties. It is filtered off (b2) and dried (c) ca. 2 cm lumps of the material are calcined in a rotary kiln (d) directly heated with natural gas at 650-700 °C. Crystal growth is controlled by adding 1-2 wt% NaCl, 2 wt % Na2S04 and traces of Mg2 + (ca. 2000 ppm), and K+ (ca. 100-200 ppm). The temperature profile and residence time in the kiln are controlled to obtain ZnS with an optimum particle size of ca. 300 nm. 

Figure 2. Schematic vertical profiles (a) h (dashed) and h (solid) and (b) q (dashed) and q (solid), (c) The temperature profile, corresponding to cpT = h — gZ — Lyq, illustrates die constant lapse rate within the boundary layer and the reduced lapse rate above the boundary layer. The boundary level (1 km) is indicated by die horizontal dashed line in each panel. These profiles illustrate typical climatic values that are determined by moist convective adjustment in the free atmosphere and dry adiabatic convection in the boundary layer. [Used by permission of Geological Society of America, from Forest et al. (1999), Geol. Soc. Am. Bull., Vol. Ill, Fig. 2, p. 500.]...

A model for transient simulation of radial and axial composition and temperature profiles In pressurized dry ash and slagging moving bed gasifiers Is described. The model Is based on mass and energy balances, thermodynamics, and kinetic and transport rate processes. Particle and gas temperatures are taken to be equal. Computation Is done using orthogonal collocation In the radial variable and exponential collocation In time, with numerical Integration In the axial direction. 

Fig. 10 Structure development of clearcoat at varying drying temperature left 3-D substrate, bottom roughness profile- riehr profile clearcoat coated directly on substrate at RT, 80 °C and 140 °C (scan length 15 mm, y-scale 2 pm left 1 pm right) ...

Thermal Analysis Measurements. DSC scans at 40°C/min were obtained on a Perkin-Elmer DSC-2. Dried copolymer powder was used. In situ annealing treatments were applied as discussal below by programming the desired temperature profiles on the instrument. 

After printing the ceramic ink on ceramic substrates, the coatings are dried at about 150°C for 15 minutes. After the drying step the films are densified at about 1100°C for 15 minutes using a temperature profile which is compatible with the manufacturing process of the ceramic substrates. 

In this section, we assume that the green body is already dry and the stress is caused by the thermal expansion of the ceramic particles that make up the porous ceramic due to the temperature profile in the green body in either heating or cooling. For an infinite plate of thickness 2xq> the normal stress ofx) at a position x in the green body depends on the temperature difference between that point, T, and the average temperature, T. This gives the strain at that point and fixes the net local stress at [28]... 

Secondary drying Shelf temperature profile, maximum operation pressure, maximum condenser temperature and desorption rates to determine the end of. secondary drying. 

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