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1、HVAC TermsABSOLUTE HUMIDITY The weight of water vapor in a given amount of air. Grains per cubic foot or lbs water per cubic foot airABSOLUTE PRESSUREPressure measured with a base of zero.ABSOLUTE TEMPERATURE A temperature scale expressed in degrees F0 or C0 using absolute zero as a base. Referred t
2、o as the Rankin or Kelvin scale.ABSOLUTE ZERO The temperature at which molecular activity theoretically ceases. -456.69 F0 or -273.16 C0AIR CONDITIONING The process of controlling the temperature, humidity, cleanliness and distribution of the air.AIRFLOWThe distribution or movement of air.AIR HANDLI
3、NG UNIT (AHU)Equipment with a heating element and/or cooling coil and other components in a cabinet or casing.AIR BALANCINGAdjusting an air conditioning system so that the right amount of air is delivered to the right places in your home in order to achieve the right heating or cooling effect.AIR BA
4、LANCE TESTA test used to measure airflow across a tower or air handler system.AIR, STANDARD CONDITIONSConditions at which BTU ratings for summer air conditioning equipment is rated. 95 F0 dry bulb, 75 F0wet bulb at the condenser inlet and 80 F0 dry bulb, 67 F0 wet bulb at the evaporator inlet.AMPThe
5、 practical meter-kilogram-second unit of electric current that is equivalent to a flow of one coulomb per second or to the steady current produced by one volt applied across a resistance of one ohm.AMBIENT Refers to the temperature surrounding a body or unit under test.ARIAir Conditioning and Refrig
6、eration InstituteATMOSPHERIC PRESSUREThe weight of a 1 square inch column of the earths atmosphere. At sea level this pressure is 14.696 pounds per square inch.BIMETALTwo metals with different rates of expansion fastened together. When heated or cooled they will warp and can be made to open or close
7、 a switch or valve.BOILING POINTThe temperature at which the addition of any heat will begin a change of state from a liquid to a vapor.BRITISH THERMAL UNIT (BTU)The amount of heat necessary to change the temperature of 1 pound of pure water 1 degree Fahrenheit (oF).Btuh: British thermal units per h
8、our.MBH: 1000 British thermal units/hourCAPILLARY TUBEA refrigerant control consisting of a small diameter tube which controls flow by restriction. They are carefully sized by inside diameter and length for each particular application.CENTIGRADEA temperature scale with the freezing point of water 00
9、 and the boiling point 1000 at sea level.CENTRAL AIR CONDITIONING SYSTEMSystem in which air is treated at a central location and distributed to and from rooms by one or more fans and a series of ducts.CFMStands for Cubic Feet per Minute. This measurement indicates how many cubic feet of air pass by
10、a stationary point in one minute. The higher the number, the more air is being moved through the ductwork by the system.CHECK VALVEA valve designed to permit flow in one direction only.CHILLED WATERChill water is the water in the closed loop (closed to the atmosphere) or evaporator system of the chi
11、ller.COMPRESSIONThe reduction of volume of a vapor or gas by mechanical means.COMPRESSION RATIOThe ratio determined by dividing the discharge pressure, in PSI, by the suction pressure in PSI.COMPRESSOR A mechanical device used to compress gases. Three main types are: reciprocating, centrifugal and r
12、otary.CONDENSATION POINT The temperature at which the removal of any heat will begin a change of state from a vapor to a liquid.CONDENSING MEDIUM The substance, usually air or water, to which the heat in a condenser is transferred.CONDENSING UNITThe portion of a refrigeration system where the compre
13、ssion and condensation of refrigerant is accomplished. Sometimes referred to as the high side.CONDUCTIONThe transfer of heat from molecule to molecule within a substance.CONTACTORAn electromagnetic actuated relay. Usually used to refer to the relay which closes the circuit to a compressor.CONVECTION
14、The transfer of heat by a moving fluid.COOLING ANTICIPATOR A resistance heater (usually not adjustable) in parallel with the cooling circuit. It is on when the current is off, adding heat to shorten the off cycle.COP Ratio of work performed or accomplished as compared to the energy used.COIL A heati
15、ng or cooling element made of pipe or tubing, usually with plates or fins.CRANKCASE HEATERElectric heating element that is used to heat the compressor crankcase to prevent migrating refrigerant from condensing and diluting the crankcase oil during the off-cycle.CUBIC FEET PER MINUTEA common means of
16、 assigning quantitative values to volumes of air in transit, usually abbreviated CFM.CYCLEThe complete course of operation of a refrigerant back to a selected starting point in a system. Also used to describe alternating current through 360 space degrees.DAMPERA movable plate, located in the ductwork, that regulates airflow. Dampers are used to direct air to the areas that need it most. Typically used in a zoning application.dBA decibel is a unit used to measure the relative in
