Unit 24 Test and Quiz Review
C
A TXV with a ______________ charge bulb, sometimes referred to as a critical charge bulb, is often called a maximum operating pressure (MOP) valve A. liquid cross B. liquid C. vapor D. vapor cross
C
A TXV with a liquid charged bulb is usually limited to ___________________________ A. systems that operate below atmospheric pressure B. high temperature applications C. applications that have a narrow operating range D. applications where the ambient air temperatures stays above freezing
C
A capillary tube metering device controls refrigerant flow by A. using superheat B. using a stepper motor C. pressure drop D. temperature drop
A
An AXV tries to maintain a constant ____________________ in the evaporator A. pressure B. superheat C. subcooling D. frost line
D
An EEV uses a ________________ to control the valve's port, which in turn controls evaporator superheat A. sensing bulb and transmission line B. capillary tube C. spring D. stepper motor
A
An automatic expansion valve (AXV) is designed to maintain a constant __________________ in the evaporator A. pressure B. oil level C. superheat D. liquid level
True
An external-equalized TXV must always be installed when a refrigerant distributor is used because of the distributor's large pressure drop True or False
B
Conditions such as large varying head pressures, widely varying evaporator loads, and very low liquid-line temperatures can be controlled by a (n) _________________ TXV A. maximum operating pressure (MOP) B. balanced-port C. pressure-limiting D. internally equalized
B
How does the automatic expansion valve respond to a load increase? A. It opens, decreasing the refrigerant flow B. It closes, decreasing the refrigerant flow C. It opens, increasing the refrigerant flow D. It closes, increasing the refrigerant flow
D
If a system with a capillary tube metering device is properly charged, when it nears the desired box temperature it will have a superheat of approximately __________. A. 2 degrees F to 5 degrees F B. 15 degrees F to 20 degrees F C. 10 degrees F to 15 degrees F D. 8 degrees F to 12 degrees F
A
Liquid, vapor, cross liquid, and cross vapor are all types of ____________. A. TXV bulb charges B. AXV bulb charges C. pistons D. capillary tube bores
A
On a PID controller, the difference between the superheat set point of the controller and the actual superheat is called _____________ A. offset B. proportion C. integral D. derivative
A
On a ____________________ TXV, the liquid pressure is cancelled out because it acts on equal areas but in opposite directions A. balanced-port B. pressure-limiting C. cross vapor D. cross liquid
C
The TXV responds to an increased heat load by _______________. A. decreasing refrigerant flow B. keeping refrigerant flow constant C. increasing refrigerant flow D. not reacting to changing heat loads
B
The TXV tries to maintain a constant ________________ in the evaporator A. pressure B. superheat C. subcooling D. brass
C
The ____________ on a TXV is used to compensate for pressure drops from the inlet to the outlet of the evaporator A. sensing bulb and transmission line B. needle and seat C. external equalizer D. internal equalizer
C
The _______________ is located inside the valve body and moves the needle in and out of the seat in response to system load changes A. transmission line B. external equalizer C. diaphragm D. sensing bulb
A
The __________________ does not control superheat, is a fixed-bore device with no moving parts and cannot adjust to load changes A. capillary tube B. automatic expansion valve C. thermostatic expansion valve D. electronic expansion valve
B
The ____________________ charge bulb is usually limited to applications that have narrow operating ranges or to special functions like desuperheating on the high side of the system A. vapor B. liquid C. cross vapor D. cross liquid
D
The bulb of the TXV is mounted on the ___________________ A. compressor inlet B. compressor outlet C. evaporator inlet D. evaporator outlet
C
The controls of a (n) ____________________ use algorithms, a set of electronic instructions, and a proportional integral derivative (PID) controller A. automatic expansion valve (AXV) B. crankcase heater (CCH) C. electronic expansion valve (EEV) D. thermostatic expansion valve (TXV)
False
The external equalizer line should always be piped to the suction line before the expansion valve sensing bulb True or False
C
The needle and seat of a TXV are normally made of A. copper B. aluminum C. stainless steel D. brass
D
The spring tension on a TXV is factory set for a predetermined superheat of ___________ degrees F A. 12-15 B. 6-8 C. 6-10 D. 8-12
D
The three factors that determine the capacity of a TXV are: evaporator temperature, liquid temperature entering the valve, and _______________________ A. number of evaporator circuits B. evaporator pressure C. length of the sensing bulb transmission line D. pressure drop across the valve
D
The three pressures that act to open or close a thermostatic expansion valve (TXV) are __________________ pressure A. bulb, compressor, and evaporator B. spring, bulb, and orifice C. compressor, condenser, evaporator D. evaporator, bulb, and spring
A
The two factors that determine how much liquid will pass through a capillary tube at any given pressure drop are the _____________________ A. length and diameter B. type of refrigerant and oil C. evaporator and suction-line size D. spring and bulb pressure
B
To prevent an overloaded compressor during a hot pulldown on a low-temperature cooler, a _________________ expansion valve can be used A. balanced-port B. pressure-limiting C. cross vapor D. cross liquid
B
When should an externally equalized TXV be used? A. When the system is a low-or medium-temperature application B. When there is excessive pressure drop through the evaporator C. When the TXV is used in a low ambient condition on a single-circuit evaporator D. When the system is equipped with a semihermetic compressor
A
Which is not a pressure or force acting on a TXV diaphragm? A. Head pressure B. Evaporator pressure C. Spring pressure D. Bulb pressure
