单项选择题
A.shell and tube type
B.plate type
C.coil type
D.conical disc type
单项选择题 To avoid impingement attack, care must be taken with the water （） through the tubes of the heat exchangers.
单项选择题 A non-return valve in the air delivery line near to the compressor must be （）type similar to the compressor discharge valve.
单项选择题 A （） in the air delivery line near to each compressor is essential.