单项选择题
A vacuum is initially created in a flash type distilling plant by（）.
A.the flashing of the feed water B.the condensation of the saltwater feed C.air ejectors, eductors, or a separate vacuum pump D.condensation of the distillate
单项选择题 A refrigeration unit will tend to short cycle when operating （）.
单项选择题 Which of the following problems could cause air to blow out through the inlet air filter of a running compressor?（）
单项选择题 In which of the listed hydraulic systems will the installation of an oil cooler be necessary?（）
