时间：2011-03-11 23:13来源：蓝天飞行翻译 作者：admin 点击：次
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dry adiabatic lapse rate (meteorology). The rate of decrease of temperature with altitude when unsaturated air is lifted adiabatically — that is, lifted without the addition to, or loss of, any heat energy. The dry adiabatic lapse rate is 3°C (5.4°F) per thousand feet. dry air (standard atmosphere). Air that contains no water vapor. Dry air is used as an atmospheric standard. Dry air weighs 0.07651 pound per cubic foot under standard sealevel conditions of 59°F (15°C) and a barometric pressure of 14.69 pounds per square inch or 29.92 inches of mercury. dry air pump. See dry-type air pump. dry-bulb temperature. Temperature measured by a thermometer not affected by the evaporation of water. Relative humidity is measured by finding the difference between wet-bulb and dry-bulb temperature. The thermometer that measures wet-bulb temperature has a wick around its sensitive end. This wick is saturated with water, and air blown across it evaporates the water. The evaporation causes the wet-bulb temperature to be lower than the dry-bulb temperature, and the amount lower is determined by the humidity, or the amount of water vapor in the air. dry-cell battery. A common term used for a single cell of a carbon-zinc battery. A dry cell is not totally dry. Its electrolyte is a moist paste, and it is sealed to retain its moisture. dry-charged battery. A lead-acid storage battery that has been fully charged by the manufacturer. Before the battery is shipped, all the electrolyte is drained out of it, and the cells are all sealed. Before the battery is placed in service, it is filled with electrolyte having the proper specific gravity, and the battery is given a freshening charge (a charge that brings its voltage up to the proper value). dry-chemical fire extinguisher. A type of hand-held fire extinguisher which uses a dry chemical, such as sodium bicarbonate, as the extinguishing agent. The dry chemical is normally forced out of the extinguisher by compressed nitrogen. dry ice. Solidified carbon dioxide. Dry ice sublimates, or changes from a solid directly into a gas, at a temperature of –110°F (–78.5°C). without passing through the liquid state. Dry ice is used as a refrigerant and as a means of chilling mechanical parts when they are being assembled with an interference fit. drying oil. An oil used in paints and varnishes. The oil, usually cottonseed or linseed oil, is mixed in the paint or varnish. When it is exposed to air, the oil oxidizes and forms a hard, dry film. dry rot. A type of decay found in seasoned wood. Dry rot is caused by fungi in the wood which change the normal fibers into a soft material that becomes a powder. Wood with dry rot has no structural strength. dry-sump engine. An engine in which the lubricating oil supply is carried in a reservoir, or tank, that is not part of the engine. Both gas turbine and reciprocating engines can have dry-sump lubricating systems. dry-type air pump (engine accessory). An engine-driven air pump that uses carbon vanes, rather than steel vanes. |
