The vapor pressure of a substance（）.

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  A . Ball float B . Thermostatic C . Bimetallic D . Impulse

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• On the approach of a warm front the barometric pressure usually（）.

  A . falls B . rises C . is steady D . is unreliable

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• The pressure head of a pump is given in the unit of （）.

  A . kg B . MPa C . meter fluid column D . None of the above is true

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• The evaporating pressure in R22 vapor compression refrigeration plant should be （） atmospheric.

  A . below B . above C . equal to D . much larger tha

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• The atmosphere in the vicinity of a high pressure area is called a(n)（）.

  A . anticyclone B . cold front C . occluded front D . cyclone

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• In a refrigeration system, the refrigerant absorbs the latent heat of vaporization in the（）.

  A . compressor B . condenser C . receiver D . evaporator

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  A . Pressure-reducing valve B . Unloading valve C . Counterbalance valve D . Pressure-relief valve

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• The effect of high vapor superheat in a refrigeration system, is a/an （）.

  A . increased capacity of the compressor B . more efficient operation of the thermal expansion valve C . decreased capacity of the compressor D . loss of receiver capacity

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• Small droplets of water entrained in the flashed vapor produced in a flash-type evaporator, are removed by the （）

  A . spray pipes B . demisters C . condensers D . splash baffle

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• Which of the listed components is considered to separate the high pressure side of a refrigeration cycle from the low pressure side of the cycle?（）

  A . The condenser and the expansion valve B . The king valve and the solenoid valve C . The compressor and the expansion valve D . The condenser and the solenoid valve

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• A barometer showing falling pressure indicates the approach of a（）.

  A . high pressure system B . low pressure system C . high dew point D . low dew point

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• The component of a refrigerating system in which the refrigerant vaporizes and absorbs heat is known as the （）.

  A . condenser B . vapor generator C . accumulator D . evaporator

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• The tendency of a flammable liquid to vaporize is indicated by its （）.

  A . ignition temperature B . flash point C . flammable range D . convection index

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• The vapor pressure of a gas is the pressure necessary to keep it in a(n)（）.

  A . soluble state B . solid state C . liquefied state D . inert state

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• What is the substance called which can readily be converted from a liquid into a vapor, and also from a vapor into liquid with a reasonably narrow range of pressure?（）

  A . Refrigerator B . Refrigerant C . Cooling medium D . Brine

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• The （） discharge a nearly constant amount of liquid regardless of pressure.

  A . mixed-flow pump B . axial-flow pump C . centrifugal pump D . displacement pum

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• The explosive range of a mixture of flammable vapors is specified as a percentage of （）.

  A . flammable vapor by volume in air B . oxygen present to support combustion C . the temperature of the flash point D . the lower limit of explosibility of the mixture

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• The minimum concentration of a vapor in air which can form an explosive mixture is called the（）.

  A . auto-ignition point B . flash point C . lower explosive limit (LEL) D . threshold limit value (TLV)

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• When the relief valve opens it discharges high pressure refrigerant vapor to the （）.

  A . liquid strainer B . refrigerant inlet of the condenser C . inlet side of the evaporator D . suction side of the compressor

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• The pressure head of a water pump is given in the unit of （）.

  A . kg B . MPa C . mH20 D . None of the above

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• In a vapor compression refrigeration the evaporating pressure is maintained constant by the action of the （）, which removes vapor from the evaporator at the same rate at which it is formed.

  A . evaporator B . compressor C . condenser D . none of the above

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• The purpose of the ashing step in graphite-furnace atomic-absorption spectroscopy is to（) A．vapor

  The purpose of the ashing step in graphite-furnace atomic-absorption spectroscopy is to( ) A．vaporize metal atoms to be analyzed B．cause the metal species to form carbides which are more volatile C．convert the graphite furnace to ash to avoid carbide formation D．burn off organic species that would interfere with the eletnental analysls

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• The values of the vapor pressure lowering,boiling point elevation, freezing point depression of nonelectrolyte depend on（）

  A．the volume of the solution B．the nature of the solute C．the molality of the solute in the solution D．the temperature of the solution

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• Which of the following would lead to an increase in the vapor pressure of a liquid I. Increasing the temperature II. Adding a nonvolatile

  A．I only B．II only C．Both I and II D．Neither I nor II

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