Which of the following techniques releases a stuck check valve?
A) switching cycles to create or release pressure on the valve
B) adding refrigerant to shift the position of the valve
C) moving a magnet along the middle or end of the valve
D) purging the system to shift the position of the valve
C
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Liquid ethanol is a flammable fluid and can release vapors that form explosive mixtures at temperatures above its flash point at 16.6°C. In a chemical plant, liquid ethanol (cp = 2.44 kJ/kg•K,?? = 789 kg/ m3) is being transported in a pipe with an inside diameter of 5 cm. The pipe is located in a hot area with the presence of an ignition source, where an estimated 20 kW of heat is added to the ethanol. Your task as an engineer is to design a pumping system to transport the ethanol safely and to prevent fire hazard. If the inlet temperature of the ethanol is 10°C, determine the volume flow rate that is necessary to keep the temperature of the ethanol in the pipe below its flash point.
When an evaporator coil gets dirty:
A) The static pressure drop across the coil increases. B) The static pressure drop across the coil decreases. C) The temperature drop across the coil decreases. D) The thermostatic expansion valve feeds more refrigerant to compensate.
The stems on manual stem service valves should be turned with:
A) A refrigeration service valve wrench only. B) Either an adjustable jaw wrench or a pair of pliers. C) Either a refrigeration service valve wrench or a pair of pliers. D) Either a refrigeration service valve wrench or an adjustable jaw wrench.
The output of a digital-to-analog converter is
A) a clock pulse. B) a binary number. C) a voltage level. D) any of these