Modern Chap 21: Review questions Flashcards
The simplest type of the following metering devices is
a) thermostatic expansion valve
b) automatic expansion valve
c) low-side float
d) capillary tube
d) capillary tube
_____________ metering devices automatically change their orifice sizes to account for changes in load
a) adsorption
b) equalizer
c) fixed
d) modulating
d) modulating
Which of the following statements regarding capillary tubes is not true?
a) it equalized pressure between the high and low side during the off cycle
b) it works with the suction line as a heat exchanger for improved system efficiency
c) having a proper refrigerant charge is less critical in a system with a capillary tube than it is in a system with a thermostatic expansion valve
d) it’s performance is determined by its inside diameter, its length, and the number of turns
c) having proper refrigerant charge is less critical in a system with a cap tube than it is in a system with a thermostatic expansion valve
A ________ is a fixed-orifice metering device that consists of a fitting with a hole between the fittings inlet and outlet
a) metering orifice
b) electronic expansion valve
c) heat exchanger
d) equalizer
a) metering orifice
The top of a thermostatic expansion valves diaphragm is exposed to ________, which works to close to the valve
a) atmospheric pressure
b) high side pressure
c) low side pressure
d) sensing bulb pressure
d) sensing bulb pressure
The purpose of a bleed valve or bleed port in a thermostatic expansion valve is to
a) ensure that the underside of the diaphragm is exposed to the same pressure as the evap outlet
b) equalize low-side and high-side pressure during the off cycle
c) reduce valve hunting during operation
d) vent refrigerant to the atmosphere if high-side pressure becomes excessive
b) equalize low-side and high-side pressure during the off cycle
Which of the following types of sensing bulbs are charged with the same type of refrigerant used in the system;
a) gas-charged and adsorption gas cross-charged
b) gas-charged and gas cross-charged
c) liquid-charged and gas-charged
d) liquid-charged and liquid cross-charged
c) liquid-charged and gas-charged
A mechanical pressure limiter or a __________ can be used to limit the maximum operating pressure (MOP) of a thermostatic expansion valve
a) liquid charged sensing bulb
b) liquid cross-charged sensing bulb
c) gas-charged sensing bulb
d) all of the above
c) gas-charged sensing bulb
Which of the following statements regarding automatic expansion valves is not true?
a) An AXV closes as evaporator pressure rises and opens as evaporate pressure drops
b) automatic expansion valves must be adjusted for atmospheric pressure
c) the evaporator of a system equipped with a properly operating automatic expansion valve will not become entirely filled with liquid refrigerant
d) sensing bulb pressure acts to close the valve and low-side pressure acts to open the valve
d) sensing bulb pressure acts to close the valve and low-side pressure acts to open the valve
Which of the following statements regarding stepper motor EEV’s is not true?
a) it’s controller will occasionally fully close the valve by sending the stepper motor more step signals than it can use
b) a stepper motor can rotate in small, precise, and repeatable increments
c) a stepper motor EEV has a gear train and threaded piston they convert the motors rotation into linear movement of the valve
d) a stepper motor regulates flow as it responds to a PWM signal by opening and closing rapidly
d) a stepper motor regulates flow as it responds to a PWM signal my opening and closing rapidly
A ________ varies refrigerant flow by varying the speeds at which a solenoid-operated valve opens and closes
a) dual-pressure EEV
b) float-operated EEV
c) pulse-width modulating EEV
d) variable-frequency solenoid EEV
c) pulse width modulating EEV
Which of the following statements regarding a low-side float system is not true?
a) the evaporator has a large receiver that holds liquid refrigerant
b) the float can be a sealed ball or an open pan
c) the high-side and low-side pressures balance during the Off cycle
d) these systems are often referred to as flooded systems
c) the high-side and low-side pressures balance during the off cycle
Which device is used to reduce pressure drop across a large evaporator?
a) bleeder or bypass
b) distributor
c) heat exchanger
d) pressure limiter
b) distributor
In heat pump systems, which metering device uses a moveable piston that allows full flow in one direction and causes a pressure drop for flow on the other direction?
a) automatic expansion valve
b) capillary tube
c) metering orifice
d) thermostatic expansion valve
c) metering orifice
A high-side float is a float-type metering device that regulates refrigerant flow into the evaporator based on the _________ of liquid refrigerant in the high-side receiver
a) pressure
b) sub cooling
c) temperature
d) volume
d) volume
