单项选择题
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
A.remain constant along the tubes length B.be greatest in a single pass counter flow heat exchanger C.remain constant throughout the heat exchanger D.vary from section to section through out the heat exchanger
单项选择题 If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
单项选择题 A salinity indicator is used to determine the （）.
单项选择题 If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
