单项选择题
A.cause of salt contamination
B.location of salt water contamination
C.chemical makeup of feed-water
D.level of alkalinity in condensate
单项选择题 An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
单项选择题 Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
单项选择题 The general purpose of a heat exchanger is to （）.