Which of the listed types steam traps operates on the principle that hot water flashes to steam when its vapor pressure is rapidly reduced?（）
On the approach of a warm front the barometric pressure usually（）.
The pressure head of a pump is given in the unit of （）.
The evaporating pressure in R22 vapor compression refrigeration plant should be （） atmospheric.
The atmosphere in the vicinity of a high pressure area is called a(n)（）.
In a refrigeration system, the refrigerant absorbs the latent heat of vaporization in the（）.
Which of the listed pressure control valves would be used to establish the maximum operating pressure of a hydraulic system?（）
The effect of high vapor superheat in a refrigeration system, is a/an （）.
Small droplets of water entrained in the flashed vapor produced in a flash-type evaporator, are removed by the （）
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 barometer showing falling pressure indicates the approach of a（）.
The component of a refrigerating system in which the refrigerant vaporizes and absorbs heat is known as the （）.
The tendency of a flammable liquid to vaporize is indicated by its （）.
The vapor pressure of a substance（）.
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?（）
The （） discharge a nearly constant amount of liquid regardless of pressure.
The explosive range of a mixture of flammable vapors is specified as a percentage of （）.
The minimum concentration of a vapor in air which can form an explosive mixture is called the（）.
When the relief valve opens it discharges high pressure refrigerant vapor to the （）.
The pressure head of a water pump is given in the unit of （）.
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.
The purpose of the ashing step in graphite-furnace atomic-absorption spectroscopy is to（) A．vapor
The values of the vapor pressure lowering,boiling point elevation, freezing point depression of nonelectrolyte depend on（）
Which of the following would lead to an increase in the vapor pressure of a liquid I. Increasing the temperature II. Adding a nonvolatile
