Heat burden

Table 6.22 summarises the main characteristics of APCI-MS. Sometimes the heat burden of the APCI interface causes thermal decomposition, which is unwelcome if the requested information is only the molecular weight. On the other hand, studying the thermal fragmentation can provide additional data about the sample. Since the thermal and collisional (CID) fragmentation do not necessarily follow the same pathway, the two methods do complement each other. Therefore, even good use can be made of the thermal decomposition for structure elucidation during APCI experiments [145],... 

Figure 10 is a pictorial diagram of the relationship between these various parameters. The ability to control the heat exposure and cooling period greatly reduces the heat burden on samples. The time scale is most impressive because it means that sample exposures can be attained in seconds not hours or days. The ability to have all samples ready for analysis at the same time eliminates any question... 

Dichroic filters, a special category of interference filter, have the unique ability to both reflect and transmit incident radiation. In this particular instance separating heat and light. These lamps generally reflect about 90% of the energy they do not transmit. Their first major application was in reducing the heat burdens produced by projector (PAR) lamps. 

At least one instrument manufacturer has incorporated such a filter into an instrument to reduce the heat burden on the sample surface area. 

Next step in the design process is drawing the functional requirements specification (FRS), also called the physical requirements specification. The FRS documents elaborated demands for connections, heat burden, floor load, acoustic demands, specifications of the walls, HVAC etc. 

The heat burden (amount of heat generated by apparatus and humans)... 

The ventilation factor and the room pressure determine the volume of air that has to be let in and thus the dimensions of the air duct, the number of inlet grids and the position of the metering valve of the involved supply channel or the area of the involved overflow grid. The heat burden and the admitted airflow rate furthermore determine the maximum inlet air temperature or the required capacity of any after-hearing radiator. 

The starting point for the intact circuit assessment is immediately following the ehangeover from steam generator cooling, when the decay heat burden on the normal residual heat removal system is at its maximum. The analysis assumes the worst case availability of safety measures permitted by the Technical Specifications for any intact circuit shutdown mode (see Chapter 16 of Reference 5.6) ... 

The use of chemical agents in battie imposes a significant burden on troops because of the cumbersome nature of the protective clothing and the attendant heat load in hot climate situations. This factor alone imposes a burden on potential target personnel, lowering their effectiveness. U.S. troops in the 1991 Mideast war Desert Storm were provided with protective gear that did not deter them with regard to the outcome of the action. 

However, many costs cannot be directly charged to an individual produc t. These so-called indirect, burden, or overhead costs range From the lighting and heating required for the plant and offices to the cafeteria and medical facihties provided. When several products are made in a plant, it becomes increasingly difficult to allocate overheads correctly among the various products. 

Because heat-transfer equipment for solids is generally an adaptation of a primarily material-handhng device, the area of heat transfer is often small in relation to the overall size of the equipment. Also pecuhar to sohds heat transfer is that the At varies for the different heat-transfer mechanisms. With a knowledge of these mechanisms, the At term generally is readily estimated from temperature hmita-tions imposed by the burden characteristics and/or the construc tion. 

Conauctive Heat Transfer Heat-transfer equipment in which heat is transferred by conduction is so constructed that the solids load (burden) is separated from the heating medium by a wall. 

Contactive (Direct) Heat Transfer Contactive heat-transfer equipment is so constructed that the particulate burden in solid phase is directly exposed to and permeated by the heating or cooling medium (Sec. 20). The carrier may either heat or cool the solids. A large amount of the industrial heat processing of sohds is effected by this mechanism. Physically, these can be classified into packed beds and various degrees of agitated beds from dilute to dense fluidized beds. 

Radiative Heat Transfer Heat-transfer equipment using the radiative mechanism for divided solids is constructed as a table which is stationary, as with trays, or moving, as with a belt, and/or agitated, as with a vibrated pan, to distribute and expose the burden in a plane parallel to (but not in contacl with) the plane of the radiant-heat sources. Presence of air is not necessary (see Sec. 12 for vacuum-shelf dryers and Sec. 22 for resubhmation). In fact, if air in the intervening space has a high humidity or CO9 content, it acts as an energy absorber, thereby depressing the performance. 

When radiating and receiving surfaces are not in parallel, as in rotary-ldln devices, and the sohds burden bed may be only intermittently exposed and/or agitated, the calculation and procedures become veiy complex, with photometric methods of optics requiring consideration. The following equation for heat transfer, which allows for convective effects, is commonly used by designers of high-temperature furnaces ... 

This section describes equipment for heat transfer to or from solids by the indirect mode. Such equipment is so constructed that the solids load (burden) is separated from the heat-carrier medium by a wall the two phases are never in direct contact. Heat transfer is by conduction based on diffusion laws. Equipment in which the phases are in direct contact is covered in other sections of this Handbook, principally in Sec. 20. 

Some of the devices covered here handle the solids burden in a static or laminar-flowing bed. Other devices can be considered as continuously agitated kettles in their heat-transfer aspect. For the latter, unit-area performance rates are higher. 

The thermal duty here is the opposite of solidification operations. The indirect heat-transfer equipment suitable for one operation is not suitable for the other because of the material-handling rather than the thermal aspects. Whether the temperature of transformation is a definite or a ranging one is of little importance in the selection of equipment for fusion. The burden is much agitated, but the beds are deep. 

The small-spiral-large-sbaft type (Fig. ll-60b) is inserted in a solids-product line as pipe banks are in a fluid line, solely as a heat-transfer device. It features a thin burden ring carried at a high rotative speed and subjected to two-sided conductance to yield an estimated heat-transfer coefficient of 285 W/(m °C) [50 Btu/(h fU °F)], thereby ranking thermally next to the sheU-fluidizer type. This device for powdered solids is comparable with the Votator ol the fluid field. 

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