Heating-up time

Load Temperature, °C Holding time. Air removal Heat-up time. Safety Exposure time. 

Great care is needed in the design of autoclaves and sterilization cycles because of the requirement for the presence of moisture. The autoclave must be loaded to allow complete steam penetration to occur in all parts of the load before timing of the sterilization cycle commences. The time required for complete penetration, the so-called heat-up time, varies with different autoclave constmction and different types of loads and packaging materials. The time may not exceed specific limits in order to guarantee reproducibility and, for porous loads, saturated steam. The volume of each container has a considerable effect on the heatup time whenever fluids are sterilized. Thermocouples led into the chamber through a special connector are often employed to determine heatup times and peak temperatures. The pressure is refleved at the end of each sterilization cycle. Either vented containers must be used or... 

Equation 7-101 ean also he used to ealeulate the heat-up time for non-isothermal heating (e.g., hy hot-water jaeketing), provided that the differenee between the outlet and inlet jaeket temperatures is not greater than 10% of the differenee between the hateh and average water temperature [47]. 

A large part of the heating load when operating in daytime will be for fresh or outside air, which is not needed before occupation, and the heat-up time will be reduced if the fresh air supply can remain inoperative for this time. 

Dry heat is widely used to sterilize glassware and equipment parts in manufacturing areas for parenteral products. It has good penetration power and is not as corrosive as steam. However, heat-up time is... 

Transient Heating of Droplets When a cold liquid fuel droplet is injected into a hot stream or ignited by some other source, it must be heated to its steady-state temperature Ts derived in the last section. Since the heat-up time can influence the V/2 law, particularly for high-boiling-point fuels, it is of interest to examine the effect of the droplet heating mode on the main bulk combustion characteristic—the burning time. 

Procedure. One hundred grams of coal liquid was combined with a predetermined amount of presulfided Co-Mo-Al catalyst and charged to the autoclave. Reaction temperature for the runs varied from 360 to 435°C, depending on the run. A stirring setting of 1000 rpm was used, and the initial total pressure was varied from 1500 (10.4 MPa) to 2500 (17.3 MPa) psig. The heat-up rate was about 12 to 20°C/min, thus requiring a total heat-up time of about 20-25 minutes. 

The steps in the ASE process are shown in Figure 3.8. The sample is loaded into the extraction cell, and then the solvent is pumped in. Then the cell is heated to the desired temperature and pressure. The heat-up time can be 5 to 9 minutes (for up to 200° C). This is referred to as the prefill method. Alternatively, the sample can be heated before adding the solvent, which is known as the preheat method. However, the preheat method is prone to the loss of volatile analytes. Therefore, the prefill approach is generally preferred [46],... 

As noted under the discussion of the coustant reflux ratio case, the boil-up rate of an existing distillation system should be well known, so use of that boil-up rate with the vapor quantity just calculated will yield the time required for the separation of the new system. Note that this value of time refere only to the distillation itself charging time, heat-up time, cooling time and clean-out time are not included. 

The virgin bitumen is vaporized only partially at normal cracking temperatures and obtaining reproducible catalyst-bitumen contact presents a significant problem. Two modes of operation were used—semibatch and batch. In the semibatch mode, the catalyst and feed were preheated separately before contact was made in a downflow fixed-bed reactor. Preheat of the feed was held to 350°C to minimize thermal-cracking reactions prior to contact. This reactor had contact between bitumen and catalyst at reaction temperature, but it did not achieve uniform contact and meaningful cat-to-oil ratios. The batch mode provided ultimate contact with the bitumen but it had longer heat-up times... 

The study of catalytic reactions using a batch autoclave reactor has been criticized for long heat-up times and nonsteady-state catalyst activity. This catalyst-comparison study was carried out by injecting coal tar into a preheated autoclave containing precoked catalyst and hydrogen in order to eliminate long heat-up times. Nevertheless, the inherent differences in results between an autoclave and a trickle-bed reactor, which is widely used for hydrorefining of heavy liquids, exist still (5). 

Overall CoefBcient and Heat-Up Time for a Water Batch Jacket... 

The heat transfer coefficients under laminar conditions are very low and heat-up times are so large as to be impractical. One would need to pump the batch contents through a well designed heat exchanger in a recycle loop to achieve reasonable heatup times. 

The electric furnaces, in which this reaction is carried out, are ca. 15 3 3 m- in size and are lined with refractory material. Electrodes at opposite ends are connected to a graphite core. The furnace is filled round this core with the reaction mixture and electrically heated to 2200 to 2400°C. The heating up time is ca. 18 h and the reaction time a further ca. 18 h. After cooling, the sides of the furnaces are removed and the unreacted material on the edges removed. The silicon carbide, which has formed round the graphite core, is broken up and separated into different qualities. 

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