单项选择题
A.Dehydrators must be used continuously in a refrigeration system
B.A 25 ton refrigeration system has the same cooling effect as melting 25 tons of ice in 24 hours
C.A thermostatic expansion valve is used to control refrigerated space temperature
D.The liquid receiver functions to collect and remove non- condensable gases
单项选择题 By which of the following means is force efficiently provided to vary the pitch of the blades on a modem controllable pitch propeller?（）
单项选择题 Which of the following statements concerning energy is correct?（）
单项选择题 In a compression refrigeration cycle, the temperature of the liquid refrigerant experiences its greatest decrease in the（）.