Heat collapse

Heat Exhaustion (Heat Collapse Heat Prostration Heat Stress)... 

An elevated body temperature due to failed thermoregulation. It is usually defined as a temperature greater than 37.5°C to 38.3°C (100°F to 101°F). Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate. When the elevated body temperatures are sufficiently high, hyperthermia is a medical emergency and reqnires immediate treatment to prevent disability and death. See also Heat Exhaustion (Heat Collapse Heat Prostration Heat Stress). 

In heat collapse (fainting), the brain does not receive enough oxygen because blood pools in the extranities. As a result, the exposed individual may lose consciousness. This reaction is similar to that of heat exhaustion and does not affect the body s heat balance. However, the onset of heat... 

Fig. 19. Heulandite. Projection along [001], displaying the larger A channel confined by ten tetrahedra and the B channel confined by 8-membered rings, (a) Natural sample, (b) sample partially dehydrated, and (c) heat-collapsed structure [91 Al].

Heat syncope, or heat collapse, is fainting caused by the reduction of cerebral blood flow and circulation. Often, the fainting is preceded by skin pallor, vision blurring, dizziness, and nausea. Mild dehydration contributes to heat syncope. 

Figure C2.5.6. Thennodynamic functions computed for the sequence whose native state is shown in figure C2.5.7. (a) Specific heat (dotted curve) and derivative of the radius of gyration with respect to temperature dR /dT (broken curve) as a function of temperature. The collapse temperature Tg is detennined from the peak of and found to be 0.83. Tf, is very close to the temperature at which d (R )/d T becomes maximum (0.86). This illustrates...

The density of LDPE for film ranges from <0.92 to approximately 0.93 g/cm. The resin is melted in a heated extmder and converted to film by extmding through a circular die. The resulting tube is collapsed and sHt into film ranging in gauge from less than 0.25 mm to greater than 0.75 mm. Some... 

Extmsion of polyethylene and some polypropylenes is usually through a circular die into a tubular form, which is cut and collapsed into flat film. Extmsion through a linear slot onto chilled rollers is called casting and is often used for polypropylene, polyester, and other resins. Cast, as well as some blown, films may be further heated and stretched in the machine or in transverse directions to orient the polymer within the film and improve physical properties such as tensile strength, stiffness, and low temperature resistance. 

In the modified chemical vapor deposition (MCVD) technique, the reactants are deposited on the inside of a rotating siUca tube. The hoUow tube is heated from the outside by a moving oxyhydrogen torch. The oxide soot condenses onto the tube walls ahead of the burner, and the soot is then sintered into a glassy layer as the burner passes over it. When deposition is complete, the tube and its contents are collapsed to form a soHd preform rod. 

Type T is the spiraf-spiral flow pattern. It is used for all heating and cooling seiwices and can accommodate temperature crosses such as lean/rich seiwices in one unit. The removable covers on each end allow access to one side at a time to perform maintenance on that fluid side. Never remove a cover with one side under pressure as the unit will telescope out hke a collapsible cup. 

Damage will be confined to the bubble-collapse region, usually immediately downstream of the low-pressure zone. Components exposed to high velocity or turbulent flow, such as pump impellers and valves, are subject. The suction side of pumps (Case History 12.3) and the discharge side of regulating valves (Fig. 12.6 and Case History 12.4) are frequently affected. Tube ends, tube sheets, and shell outlets in heat exchanger equipment have been affected, as have cylinder liners in diesel engines (Case History 12.1). 

Effects of Water Hammer. Water hammer has a tremendous and dangerous force that can collapse floats and thermostatic elements, overstress gauges, bend mechanisms, crack trap bodies, rupture fittings and heat exchange equipment, and even expand piping. Over a period of time, this repeated stress on the pipe will weaken it to the point of rupture. 

Thermal shock In biphase systems, steam bubbles may become trapped in pools of condensate in a flooded main, branch, or tracer line, as well as in heat exchanger tubing and pumped condensate lines. Since condensate temperature is almost always below saturation, the steam will immediately collapse. 

The lift pipe design was tapered to a larger diameter at the top. This minimized the effects of erosion and catalyst attrition, and also prevented the instantaneous total collapse of circulations when the saltation concentration, or velocity, of solids is experienced (i.e. the slump veloeity-that velocity helow which particles drop out of the flowing gas stream). In a typical operation, 2 % to 4 % eoke can he deposited on the catalyst in the reactor and burned in the regenerator. Catalyst circulation is generally not sufficient to remove all the heat of eombustion. This facilitated the need for steam or pressurized water coils to be located in the regeneration zone to remove exeess heat. 

Heat stroke A serious acute condition caused by the elevation of the body temperature above the danger level. Symptoms can include redness of the face, reduced sweating, erratic behavior, confusion, dizziness, collapse, or unconsciousness. 

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