单项选择题 The design of for a flash type evaporator is of critical importance because it must provide an optimum feedwater spray pattern that facilitates the flashing process, and it must also maintain a pressure differential between successive stages（）

单项选择题 A flash-type evaporator discharges heated seawater into a chamber that is maintained at a pressure than the vapor pressure of the entering heated seawater, and subsequently the flashed water vapor thereby produced（）

单项选择题 Before the sludge in a purifier is ejected,（）