Heat-Transfer Devices

An alternative to the sand bath is a heat-transfer system that employs copper tube plates or aluminum metal blocks drilled to accommodate the different re- www]K action vials and flasks (Chapter 3W, Fig. 3.3W). 

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Gas-Heated Reforming. Gas-heated reforming is an extension of the combined reforming concept where the primary reformer is replaced by a heat-transfer device in which heat for the primary reforming reaction is recovered from the secondary reformer effluent. Various mechanical designs have been proposed which are variants of a shell-and-tube heat exchanger (12,13). 

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. 

Equipment commonly employed for the diying of sohds is described both in this subsection in Sec. 12, where indirect heat transfer devices are discussed, and in Sec. 17 where fluidized beds are covered. Diyer control is discussed in Sec. 8. Excluding fluid beds this subsection contains mainly descriptions of direct-heat-transfer equipment. It also includes some indirect units e.g., vacuum diyers, furnaces, steam-tube diyers, and rotaiy calciners. 

Heat transfer is normally much more demanding on a large scale. The introduction of hehcal coils, vertical tubes, or other heat-transfer devices causes an increased tendency for areas of low recirculation to exist. 

Crystalline scales and other minerals may form deposits that reduce the effectiveness of the boiler as a heat transfer device or cause fouling that can impede the flow of water and cause overheating by reducing the level of furnace cooling below design specifications. The presence of process contaminants also leads to fouling. 

Any of a number of steel tubes used simultaneously as heat transfer devices for both steam generation and boiler furnace cooling. Boiler tubes may be straight or bent. 

Boilers are heat-transfer devices, wherein water, in the form of either liquid water or gaseous steam, is commonly employed as a medium for the transport of heat to some distant point of use. Although other heat-transfer mediums are sometimes utilized, water is particularly suitable because of its relative abundance, low cost, and high heat capacity. It is generally the medium of choice in most boiler applications, whether for domestic, commercial, institutional, or industrial purposes. 

The design of two-phase heat transfer devices requires a knowledge of the hydrodynamics so that the pressure drop, holdup, phase velocities, and interfacial areas can be determined. In this discussion Phase I will generally refer to the less-dense phase, and Phase II to the more-dense phase. The holdup of Phase I has been conventionally defined as... 

Passive Solar A system in which solar energy (heat from sunlight) alone is used for the transfer of thermal energy. Heat transfer devices that depend on energy other than solar are not used. A good example is a passive solar water heater on the roof of a building. 

The adiabatic temperature change ATa helps to evaluate the importance of heat effects in a design of a chemical reactor, even if the reactor itself is not an adiabatic one. Table 2.10 presents some useful heuristics. The use of an inert to remove or add heat is the most employed in low-cost adiabatic reactors. Considering heat-transfer devices is more expensive, but better for energy integration. 

Conventional heat pipes (Fig. 12) are convenient as heat transfer devices for sorption bed layer thermal control [15]. 

S. N. Lodwig, The Use of Solid Aluminum Heat Transfer Devices in Organic... 

Most acid plant heat transfer devices are provided with bypass capability, Fig. 22.2. 

Aerospace and Technologies Corporation use carbon fiber to improve the weight and size of other more bulky heat transfer devices, while maintaining suitable thermal conductivity. Insulated carbon fiber can also be shaped and bent to fit the area involved while meeting the heat transfer requirements. 

FIG. 11-61 Performance of tubed, blender heat-transfer device. 

DLC films can also be used as dielectric layers for thermal management systems. In this case, the DLC film is coated on copper inserts used as heat transfer devices in multichip... 

Experimental results confirmed that propane (R290) is beneficial as a working fluid for low temperature heat pipes, thermosyphons, sorbers of chemical heat pumps, chillers of electronic components and for other evaporative heat transfer devices. The experimental data at the saturated condition Ts = 20°C (ps=8.4 bar, pr = p/pcr=0.197) are obtained in this series of experiments. 

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