1、化学英语证书考试（PEC）-化工技术术语解释Gas VolumeThe amount of air or gas intake in a particular time unitm3/min、CMM：gas volume per1 minutem3/h、CMH：gas volume per1 hourm3/min、CFM：gas volume per min = cubic feet (used often in America) 1f3/min0.0283m3/minNm3/min：gas volume under normal conditions (0, humidity 0%, int
2、ake absolute pressure 760mmHg)Convert into the gas temperature. Calculation is belowQt：converted gas temperature t gas volume QN：requested gas volume under normal conditionsStatic PressuremmAq：A unit shown in height when the water pumped in or up Aq=Aqua (water) abbreviation. Waterspout in millimete
3、rs (written as mmH2O) inH2O：If not in millimeters, written in inches. (used often in America)1 inch25.4mmPa：Pascal (International unit for measuring pressure)1mmAq9.80665Pakgf/m2：1kgf/m21mmAqbar：bar (European unit for measuring pressure)1bar10.197mAq、1mbar 10.197mmAqShaft PowerThe measure of power u
4、sed at the shaft of the fan. Shaft power is measured in kW.Revolution Speedrpm、 （R/M） 、 min-1：revolution per 1 minuteGas Specific Weightkg/m3：Weight per unit volume of gasGenerally1.2kg/m3 is most common under normal conditions (20, relative humidity 65%, and absolute pressures 760mmHg) The specific
5、 weight of the gas changes due to temperature variations.The change in the specific weight of the gas due to temperature is calculated as follows.：Specific weight of gas at temperature t of gas kg/m3：Specific weight of gas in 0 temperature of gas kg/m3Conversion affected in specific weight volume pe
6、rformanceAll the performance labels in the fan catalog (capacity chart) are displayed by the normal atmospheric conditions. Therefore, specific weight becomes 1.2kgf/m3.Usually under general atmospheric condition there is no problem but when specific weight of the gas differs by a large amount it is
7、 necessary to refer to the capacity range chart.This conversion is calculated as follows(1)Static PressureSSpThe actual static pressure found in a particular situation (static pressure required by the customer) mmAqSp： Static pressure as shown seen in capacity range chart mmAq：The specific weight of
8、 the gas used(2)Shaft PowerLB：Actual shaft power kWLB：Shaft power as shown in the capacity range chart：Specific weight of gas being used kg/m3Conversion affected in rotation speed performanceThe relation between the change in the blower rotational speed and the change in the gas volume, the static p
9、ressure, and the shaft power is proportional as follows.(1)Gas Volume(2)Static Pressure (3)Shaft PowerN1：Rotation speed before change rpmN2：Rotation speed after change rpmQ1：Gas volume before change in rotational speed m3/minQ2：Gas volume after change in rotational speed m3/minSp1：Static pressure be
10、fore change in rotational speed mmAqSp2：Static pressure after change in rotational speed mmAqLB1：Shaft power before change in rotational speed kWLB2：Shaft power after change in rotational speed kWNatural TypeNatural draught without using a blower.Forced Draft TypeA blower is installed at the air int
11、ake of the towerInduced Draft TypeA blower is installed at the air outlet of the towerClosed TypeAn indirect cooling method where water passes through a pipe and the air and spayed water flow outside of the pipe.Open TypeAir/water direct contact methodWhat is a cooling tower?An equipment that cools
12、circulating water with air. The principle of the cooling tower: the circulating water loses heat during evaporation thus lowering the temperature. CavitationCavitation is the forming and subsequent collapse of bubbles in a liquid when water at normal temperature is pumped up more than 10m and the sa
13、turated vapor pressure falls below the static pressure. Its a phenomenon that occurs when the static pressure drops below the saturated vapor pressure, evaporates or condenses the liquid, thus creates bubbles. When these bubbles collapse, it creates a shockwave, noise and vibration and reduces the e
14、fficiency of the machinery, such as screws or pumps. The erosion of the machinery could cause the machinery to be destroyed during cavitation.When the available NPSH is greater than the necessary NPSH, depending on the given conditions of pipe or pump installation, cavitation will not occur.Availabl
15、e NPSHThere is a need for a higher static head pressure when the total pressure at the impellor suction is equivalent or higher than the saturated vapor pressure, cavitation in the pump will not occur. This available NPSH (Net Positive Suction Head) can be calculated as follows.NPSHavHaHvpHshl Ha：wo
16、rking atmospheric pressure at suction surface (m) Hvp：Saturated vapor pressure at that water temperature (m) Hs：Suction Total Head (m) (when pumping in +, when pumping up - ) hl：Suction loss from all pipingDynamic SealIn the case of a vertical Molded pump: when the pump is in operation, the centrifu
17、gal force at the back of the impellor blade pushes the liquid to the casing, forming a liquid membrane. This effect at the rear of the blade prevents leakage.Hold UpHold up is the volume of liquid retained in the filling during operation.HOGAn indicator showing the performance of the filling. The lo
18、wer the indicator, the better the performance. It is varied according to the type and concentration of gas and, the type of filling and capacity of the cleaning fluid. FloodingWhen there is too much cleaning fluid being spayed it fills the airspace in the filling, causing the gas flow to be obstruct
19、ed. The gas then tries to force its way through, causing the fluid to burst into droplets passed outside with the gas. This phenomenon is called flooding.Biological Deodorizing TowerPorous ceramic is used in this deodorizing processing equipment where the carrier filled with living bacterias metabol
20、ize and decompose odors through oxidization. Activated Carbon Absorption TowerThis equipment removes odors with activated carbon.Cleaning Tower (Scrubber)When polluted gas enters the equipment, water or harmful elements are neutralized by a chemical solution within the tower. They are then absorbed into a cleaning fluid and further neutralized so that a clean gas may be discharged. This type or cleaning tower is known as a scrubber.
