单项选择题
A.admit only enough fresh outside air to provide proper ventilation
B.reduce the air reheating system load
C.lower the compressor head pressure
D.operate the purge recovery unit continuously
单项选择题 To add refrigerant to the low side of an air conditioning system, the refrigerant should be introduced through the （）
单项选择题 Which of the fluids listed is normally used to condense the primary refrigerant in a shipboard central air conditioning system?（）
单项选择题 The effective temperature of air is dependent upon（） Ⅰ.relative humidity Ⅱ.air velocity