單項選擇題A vacuum is initially established in the first and second stages of a low pressure evaporator by the use of （）

A.vacuum drag from the auxiliary condensate system
B.individual vacuum pumps
C.a single non-condensing air ejector
D.a two stage air ejector


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1.單項選擇題The heated feed-water entering any flash chamber of a flash-type evaporator will（）

A.vaporize, with the un-flashed water remaining at the temperature at which it entered the flash chamber
B.vaporize, with the un-flashed eater equalizing to the saturation conditions existing in the f lash chamber
C.vaporize, with the remaining water a t a temperature greater than it entered the flash chamber
D.boil, allowing steam bubbles to rise through the brine at the bottom of the flash chamber

2.單項選擇題On a multistage flash-type evaporator, the flash chamber is （）

A.combined as part of the salt water feed heater
B.the open area above the brine levels in the first and second stages
C.combined as part of the distillate cooler
D.another term used to describe the vapor feed heater

4.單項選擇題The second stage feed-water temperature and shell absolute pressure in a multistage, flash type, distilling plant is （）

A.higher than the first stage feed-water temperature and absolute shell pressure
B.lower than the first stage feed-water temperature and absolute shell pressure
C.the same as the first stage feed-water temperature and absolute shell pressure
D.not related to the feed-water temperature and absolute shell pressure

5.單項選擇題The efficiency of a flash type evaporator can be increased by（）

A.lowering brine discharge density
B.decreasing the absolute pressure of each stage
C.increasing the saltwater feed heater temperature
D.increasing the pressure at the spray pipe