High altitude

Hydraulic and Heat-Transfer Fluids. HydrauHc fluids (qv) for high altitude supersonic aircraft and thermal exchange appHcations including solar panels employ fluids such as tetrakis(2-ethyIhexoxy)silane. These products have been marketed under the trade name Coolanol by Monsanto (see Heat-exchangetechnology). 

Because of tank heating, fuel volatiUty is also more critical in supersonic aircraft. For example, the Concorde tank is pressurized to prevent vapor losses which could be significant at high altitude where fuel vapor pressure may equal atmospheric pressure. The tank can reach 6.9 kPa (1 psi) at the end of a flight. The need to deoxygenate fuel for thermal stabiUty in the HSCT will doubdess require a similar pressurized system. 

Upon the advent of high performance jet-powered aircraft, the fire bomb became obsolete. When deUvered at speeds approaching Mach one (345 m/s), the design characteristics were often grossly exceeded and many units broke up or functioned while stiU on the aircraft. DeHvery from high altitude created craters and deposited most of the flame agent payload in those craters. 

Aceta2olamide, the best example of this class of diuretics (69,70), is rarely used as a diuretic since the introduction of the thia2ides. Its main use is for the treatment of glaucoma and some minor uses, eg, for the a1ka1ini2ation of the urine to accelerate the renal excretion of some weak acidic dmgs, and for the prevention of acute high altitude mountain sickness. 

The oxygen sensor closed loop system automatically compensates for changes in fuel content or air density. For instance, the stoichiometric air/fuel mixture is maintained even when the vehicle climbs from sea level to high altitudes where the air density is lower. 

The Montreal Protocol of July 1987 resulted in an international treaty in which the industrialized nations agreed to halt the production of most ozone-destroying chlorofluorocarbons by the year 2000. This deadline was hastily changed to 1996, in February 1992, after a U.S. National Aeronautics and Space Administration (NASA) satellite and high-altitude sampling aircraft found levels of chlorine monoxide over North America that were 5i % greater than that measured over Antarctica. 

The theoretical steam rate (sometimes referred to as the water rate) for stream turbines can be determined from Keenan and Keyes or Mollier charts following a constant entropy path. The theoretical steam rate is given as Ib/hr/kw which is easily converted to Ib/hr/hp. One word of caution—in using Keenan and Keyes, steam pressures are given in PSIG. Sea level is the basis. For low steam pressures at high altitudes appropriate coirections must be made. See the section on Pressure Drop Air-Cooled Air Side Heat Exchangers, in this handbook, for the equation to correct atmospheric pressure for altitude. 

Levels below 19.5% oxygen ean have detrimental effeets if the body is already under stress, e.g. at high altitudes. Exposures below 18% should not be permitted under any eireumstanee. Other ehemieals, e.g. earbon monoxide, result in toxie anoxia due to damage of the body s oxygen transport or utilization meehanism. 

A corresponding situation occurs at high altitude, where one-third of the sea-level power available has been lost due to low atmospheric pressure. This low air density also reduces aerodynamic drag, but rolling resistance is unaffected by altitude. As a result, power resei"ve is seen to suffer. In fact, at this altitude, the power available in fourth gear is insufficient to operate the vehicle on a 6 percent grade at any speed without downshifting. 

Figure 3-45. High altitude process vacuum system, NPSH requirements.

TEST CHAMBERS FOR HIGH-ALTITUDE RESEARCH STUDY... 

Conditions are frequently suitable for the formation of lee waves over the mountainous regions of the US, an effect that is routinely exploited by glider pilots to obtain exceptionally high altitudes. The combination of lee waves with strong winds that are sufficient to produce damage to structures is fortunately rare, but do occur in hazardous mountainous regions. 

Another example of the importance of the VI is the need for a high viscosity index hydraulic oil for military aircraft, since hydraulic control systems may be exposed to temperatures ranging from below — 65°F at high altitudes to over 100°F on the ground. For the proper operation of the hydraulic control system, the hydraulic fluid must have a sufficiently high VI to perform its functions at the extremes of the expected temperature range. 

Recent space-probe and earth-based spectroscopic studies of the planet Venus suggest how much remains to be learned about the other planets. Earlier estimates of the surface temperature of Venus placed it near 60°C. The more detailed studies show, however, that two characteristic temperatures can be identified, —40°C and 430°C. The lower temperature is attributed to light emitted front high altitude cloud tops. The higher temperature is likely to be the average surface temperature. 

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