单项选择题
A double suction centrifugal pump impeller has been installed in the reverse direction, and will （）.
A.have a greater head capacity
B.operate with increased impeller efficiency
C.discharge through the suction side of the pump casing
D.require more power to run the shaft
单项选择题 Hydraulic machinery failures are commonly caused by misalignment of the system components and by （）.
单项选择题 Air compressor receivers should be “blown down” at least （）.
单项选择题 A thermostatic expansion valve is properly controlling evaporator superheatAdjusting this valve to lower the superheat will result in a/an （）.