High-speed heating

Strykowski, P. J., A. Krothapalli, and D. Wishart. 1993. Enhancement of mixing in high-speed heated jets using a counterflowing nozzle. AAIA J. 31 2033-38. 

The essential result of the high-speed heat-transfer analysis is that heat-transfer rates may generally be calculated with the same relations used for low-speed incompressible flow when the average heat-transfer coefficient is redefined with the relation... 

The analogy between heat transfer and fluid friction [Eq. (5-56)] may also be used when the friction coefficient is known. Summarizing the relations used for high-speed heat-transfer calculations ... 

This Stanton number is then used in Eq. (5-125), (5-126), or (5-127) to calculate the heat-transfer coefficient. When calculating the enthalpies for use in the above relations, the total enthalpy must be used i.e., chemical energy of dissociation as well as internal thermal energy must be included. The reference-enthalpy method has proved successful for calculating high-speed heat transfer with an accuracy of better than 10 percent. 

How is the heat-transfer coefficient defined for high-speed heat-transfer calculations ... 

The porous nature of paper with air entrapped between the fibres acts as an insulator. This makes heat transfer more difficult, particularly on high-speed heat sealing equipment. 

Another type of direct dryer is the spray dryer [64] but there is no such installation in the United States for sludge treatment [65]. A recent patent of cyclonic dryer may be used in sludge drying [66]. In this cyclonic dryer, a high-speed heated air stream is introduced to the cylinder such that it rotates tangentially around a central axis immediately upon entry into the cylinder. The wet material such as sludge is fed to the dryer directly into the outer spiral air stream with turbulence generated by ramps on the wall of the... 

Spin Welding. Spin welding is an efficient technique for joining circular surfaces of similar materials. The matching surfaces are rotated at high speed relative to each other and then brought into contact. Frictional heat melts the interface and, when motion is stopped, the weld is allowed to soHdify under pressure. 

Some induction heating furnaces must operate at frequencies higher than the supply frequency. Formerly, rotating motor alternator frequency converters were used. Now the avadabdity of high speed, high power sdicon controlled rectifiers for use in frequency converters has made rotary converters obsolete. Modem units operate at higher efficiency, cost less, require less factory space, and coordinate readdy with process controls (2). 

Commonly used materials for cable insulation are poly(vinyl chloride) (PVC) compounds, polyamides, polyethylenes, polypropylenes, polyurethanes, and fluoropolymers. PVC compounds possess high dielectric and mechanical strength, flexibiUty, and resistance to flame, water, and abrasion. Polyethylene and polypropylene are used for high speed appHcations that require a low dielectric constant and low loss tangent. At low temperatures, these materials are stiff but bendable without breaking. They are also resistant to moisture, chemical attack, heat, and abrasion. Table 14 gives the mechanical and electrical properties of materials used for cable insulation. 

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