ACR 132 Final
If the wet-bulb and dry-bulb temperature are both 80^F, what is the humidity?
100%
What is the relative humidity if the dry bulb temperature is 100^F and the wetbulb temperature is 65^F?
13%
If the dry-bulb temperature is 93^F and the wet bulb temperature is 60^F, what is the specific volume of the air
14.0 ft3/lb
pure water boils at a temperature of 212'F at which of the following standard conditions ?
14.967 PSI
If an R-12 refrigeration system has its air-cooled condensing unit on a 100°F roof and the condenser outlet temperature (refrigerant) is 115°F, with how much sub-cooling is the condenser operating
15^F
if 22 oz. of refrigerant are to be added to a refrigeration system and the supply cylinder weighs 24 lb. 12 oz. before any is added, what will be the supply cylinder weight after the system has been charged?
23 lb 6 oz (NOT an answer choice, write in)
if 30 oz. of refrigerant are to be added to a refrigeration system and the supply cylinder weighs 26 lb. 4 oz. before any is added. what will the supply cylinder weigh after the system has been charged?
24 lb 6 oz
If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 psig, what is the pressure at the inlet of the evaporator?
25 psig
A ton of refrigeration is equal to
288,000 Btu/24 hr
The standard atmospheric pressure at sea level is _____
29.92" Hg
One watt of electrical energy is equal to
3.413 Btu
A typical evaporator operating temperature in an air-conditioning system is
40^ F
What is the dew-point temperature if the wet-bulb temperature is 65^F and the dry-bulb temperature is 100^F?
40^F
The density of water is
62.3 lb/ft3
The factory charge in a split system, using R-22, shows 6 lb. 8 oz. in the outdoor condensing unit and 2 oz. in the evaporator. The 3/8" liquid line contains 0.48 oz. per foot and the 7/8" suction line contains 0.10 oz. per foot. The refrigerant lines are 30' long. What is the correct refrigerant charge for this system?
7 lb 11 oz
A typical superheat for an evaporator operating under normal conditions would be
8 to 12^F
Reciprocating compressors have _____
A piston and a cylinder
When charging a refrigeration system with a near-azeotropic mixture, what must be done to prevent liquid from entering the system?
Charge as a liquid through the low side using a restrictor
The _____ are used to change the vapor to a liquid and the liquid form back into a vapor the refrigeration cycle.
Condenser and evaporator
As heat is applied to a closed container containing a gas, the pressure inside the container will decrease
FALSE
Both sensible heat and latent heat transfers can be read with a thermometer.
FALSE
If a cylinder of R-22 is moved from a 100^F truck body into an 80^F shop, the quantity of liquid refrigerant in the cylinder will remain the same.
FALSE
Temperature difference does not affect heat transfer rate
FALSE
The all-aluminum coil has a higher heat transfer rate than the standard copper tube-aluminum fin coil.
FALSE
The only location where the refrigerant vapor is superheated is in the evaporator
FALSE
Vapor is more dense than liquid and as the liquid refrgerant boils, it has a tendency to sink.
FALSE
On a package air conditioning system, which refrigerant lines must be field installed?
NO lines need to be installed
Which of the following refrigerants has the lowest boiling temperatures at atmospheric pressure?
R-502
A dirty condenser coil can lead to
Reduced efficiency
A manufacturer's charging chart may be used when available to determining the correct charge for a system.
TRUE
An expansion valve is the pressure reducing device that controls the flow of liquid refrigerant into the evaporator.
TRUE
Equipment will perform at it's best efficiency when running at full load.
TRUE
Heat is a form of energy because of the motion of molecules
TRUE
If a residential split air conditioning system has a compressor equipped with a start capacitor and relay, it is probably using a thermostatic expansion valve as a metering device.
TRUE
Low suction pressures, iced coils, short- cycling, and inefficient cooling can also result from low head pressures.
TRUE
One good feature of an electronic charging scale is that it counts upward as refrigerant is removed, to tell the technician how much refrigerant was used.
TRUE
The refrigeration evaporator is a component that absorbs head from the conditioned space into the refrigeration system
TRUE
To check the performance of a dry-type evaporator, the service technician would first make sure the refrigerant coil is operating with enough liquid inside.
TRUE
What happens when room temperature soda is poured into a glass of ice?
The ice melts because it is absorbing heat from the soda.
Temperature can be thought of as ______
a description of the level of heat
Charging a refrigeration system refers to____
adding refrigerant to a system
Comfort can be described as the gentle balance between _____.
air cleanliness, air movement, temperature, and humidity
A vapor material exerts a pressure or force
all directions
Condensing temperature in an air-cooled condensing unit can be reduced by
all of the above
Ice melts in iceboxes because
all of the above
The primary function of an expansion device is to
all of the above
The purpose of a capillary tube is to
all of the above
Which of the following can be used to maintain the head pressure of a system with an air-cooled condenser?
all of the above
a graduated cylinder charging device is a device that _____
all of the above
If a thermostatic expansion valve's thermal bulb came loose from the suction line at the outlet of the evaporator, which of the following could result?
all of the above are correct
High temperature refrigeration is that produced by ____
an air-conditioning system
Infiltration is the term used when referring to the air entering a structure
around doors and windows
The _____ of the liquid refrigerant determins the coil operating temperature.
boiling temperature
Liquid entering the compression chamber of a reciprocating compressor can lead to ____.
both a and b
When charging a system with vapor refrigerant from a refrigerant cylinder, the cylinder will become ______
cold
The purpose of an externally equalized thermostatic expansion valve is to___.
compensate for the excessive evaporator pressure drop
A popular material combination used in air conditioning evaporators and condensers is
copper tube-aluminum fin
If the temperature remains constant and the volume that a gas occupies increases, the pressure will
decrease
If the application requires a coil design to operate below freezing, there must be provision for
defrost
In rotary type motor-compressor assemblies, the motor is cooled by _____.
discharge gas from the compressor
A direct expansion-type evaporator is also called a
dry-type evaporator
.Of the heat produced in the human body, which is by perspiration?
evaporation
The ____ in a refrigeration system is responsible for absorbing head into the system from whatever medium is to be cooled.
evaporator
The boiling temperature and its relationship to the system exist in the
evaporator
A thermostatic expansion valve controls refrigerant flow to the evaporator based on ____
evaporator suction line superheat
Evaporators that are operated full of liquid and are equipped with a device to keep the liquid refrigerant from passing to the compressor are known as ____.
flooded evaporators
high efficiency condensers
have more surface area than standard condensers
The total heat content of infiltrated air of the same dry-bulb temperature may vary from one part of the country to another because of difference in _____.
humidity
If a critically charged refrigeration system is over charged, which of the following is a likely result?
increased operating pressures
When the load on the evaporator increases, the TXV
increases the flow of refrigerant
On a split air conditioning system with a remote condensing unit, which refrigerant lines must be field installed?
liquid and suction
Refrigerant in liquid form is normally put into the system through the _____
liquid line
When a refrigerant enters the compressor, it is a _____ and when it leaves the compressor is is a ____
low pressure low temperature superheated vapor, high pressure high temperature superheated vapor
The package air-conditioning system is ____ than the split system because it is completely factory assembled and charge with refrigerant.
more efficient
The TXV sensing bulb is mounted _____
on the suction line between the evaporator and the compressor
A fresh air intake is necessary to keep the indoor air from becoming
oxygen starved and stagnant
PSIG indicates
pounds per square inch absolute gauge
A Bourdon tube is often found in a(n)
pressure gauge
The compressor in a refrigeration system_____
pumps the refrigerant throughout the system
In a water-cooled condenser, a regulating valve is used to control the
refrigerant condensing temperature
The process of removing heat from a place where it is not wanted and transferring that head to a place where it makes little or no difference is known as ____
refrigeration
The refrigerant in a condenser in a refrigeration system ____.
rejects heat
The condenser ____
rejects the heat from the refrigerant
Rotary compressors are used primarily in ____.
residential air conditioning
The dry-bulb temperature is the
sensible heat level of the air
Fractionation occurs when
some of a blended refrigerant evaporates or condenses before the rest of the blend
In reciprocating and scroll type motor-compressor assemblies, the motor is cooled by
suction gas returning to the compressor
Refrigerant in vapor form is normally put into the system through the _____
suction line
_____ is the best method of checking to see when a refrigerant coil has a proper level of refrigerant
superheat
Most of the heat energy in the suction vapor entering the compressor is
superheated from the evaporator
The wet-bulb temperature
takes into account the moisture content of the air
The dew-point temperature is the _____
temperature at which moisture begins to condense out of the air.
The ___ relationship correlates the vapor pressure and the boiling point of water and is the basis for controlling the cooling system's temperatures.
temperature/pressure
The wet-bulb depression is
the difference between the dry and wet bulb temperatures
Refrigeration can be described as ____
the process of removing heat from a place where it is not wanted to a place where it makes little or no difference
As the temperature of a material increases, the molecules in the material _____
travel faster
when charging liquid refrigerant from a single valve supply cylinder, the cylinder is placed
upside down
The temperature of the compressed gas leaving the compressor can best be described as
very warm
The clearance volume of a compressor cylinder is the ____.
volume of the space between the bottom of the valve plate and the top of the piston at the top of the stroke
If the compression ratio of a system with a reciprocating compressor decreases, the amount of refrigerant pumped by the compressor ____.
will increase
