Refrigeration Unit
Using R22 refrigerant what is the temperature at 160 psig of pressure?
116 degrees farenheit
At sea level atmospheric pressure is how much pressure at psia?
14.7
0 psig is the same as ____________ psia.
14.7 psia = 0 psig
How many BTU's does it take to transfer 32 degrees of ice to 32 degrees of water
144 BTU's
How many BTU's does it take to transfer 0 degrees of ice to 32 degrees of ice
16 BTU's
How many BTU's does it take to transfer 32 degree of water to 212 degrees of water
180 BTU's
How many BTU's is it to change one pound of 32 degree water to one pound of 212 degrees of water?
180 BTU's
On a refrigeration system, the ambient temperature at the condenser is 65 degrees fahrenheit. What pressure would you expect to see on the high side of the system? (get your
218 psig
What is the maximum compressor discharge pressure that we do not want to exceed?
250 degrees f
A perfect vacuum is _________ inches of mercury?
29.92
Using R410a what is the temperature at 101 psig of pressure?
32 degrees fareheit
What is the temperature of absolute zero
460 degrees
Manufacturers recommend that we evacuate refrigeration systems, (pull a vacuum) down to ___________ microns.
500
How many BTU's does it take to transfer 212 degree's of water to 212 degrees of steam
970 BTU's
How many BTU's is it to change one pound off 212 degree water to one pound of 212 degree steam?
970 BTU's
What is the definition of Hermetic Compressor
A compressor that is sealed and welded shut
What is the definition of Scroll compressor
A compressor that reduces the volume of gas by a fixed scroll and an orbiting scroll moving the gas gradually
What is the basic premise of Charles law
A law stating that the volume of an ideal gas at constant pressure is directly proportional to the absolute temperature.
Is superheat below or above the saturation point?
Above
Moisture in a refrigeration system can cause ____________ formation?
Acid
Does Superheat add or remove sensible heat to the refridgerent?
Add
What are the two different types of condensers?
Air cooled, Water cooled.
What is the definition of Accumulator
Allows liquid in suction line to be collected and boiled off so that liquid doesn't need compressor. Used with fixed meters
What is the definition of Temperature Difference (TD)
Ambient air temp minus coil temp
What is absolute zero? What happens at that temperature?
At this temperature the molecules do not move, and there is no heat.
How do we measure the quantity of heat?
BTU's
Why does compressed refrigerant leave the compressor at such a high temperature?
Because high pressure vapor has a direct relationship with high temperature
Is subcooling below or above the saturation point
Below
What color is a compound refrigerant gauge?
Blue
What happens if we exceed the maximum test pressure with the compressor in the system?
Can damage metering device
What does it mean when a unit is considered critically charged?
Charged to exact specifications , evacuated and weighed in.
If air is accidentally introduced into a refrigeration system, where will it migrate to?
Condenser
What component in a refrigeration system is typically larger, the evaporator or condenser?
Condenser?
Heat is transferred by what three ways?
Conduction, Convection, and Radiation
What components does a reciprocating compressor use to compress refrigerant?
Connecting rod and crankshaft move pistons up against the valve plare
What is the liquid receiver?
Cylinder connected to condenser outlet for storage of liquid refrigerant in the system.
What is the definition of Pressure Temperature Relationship
Direct and predictable relationship between pressure and temperature.
What is the first thermodynamic law concerning heat as energy?
Energy can not be destroyed only transferred
How does heat transfer
From hot to cold
How do we calculate subcooling?
Gauge - Line
What is the definition of Sight Glass
Glass window in the refrigeration system that shows the amount of oil in the system
What is the definition of open compressor
Has a separate motor or a fire component
What is heat of compression?
Heat added to a vapor by the work done in the compressor.
Define latent heat.
Heat change that occurs when a substance changes state.
Define sensible heat.
Heat that can be measured.
What is the second thermodynamic law concerning how heat moves?
Heat transfers from hot to cold.
What is the state of refrigerant leaving the condenser?
Hp Ht Liquid
What is the state of refrigerant leaving the compressor?
Hp Ht Vapor
What is the state of refrigerant leaving the liquid receiver?
Hp Ht sub cooled liquid
What is the definition of Frost Line (Saturated Vapor Line)
Indication on refrigeration cylinder that there is still liquid refrigerant at the bottom of the cylinder
What types of metering devices are found on refrigeration systems?
LLSV, TXV/TEV
How do we calculate superheat?
Line - Gauge
A compressor cannot compress a _________?
Liquid
What is the definition of Liquid Slugging?
Liquid entering a reciprocating compressor at the suction part.
Storing ice cream would require a ____________ temperature application refrigeration system?
Low
What are three types of refrigerating applications?
Low, Medium, and High
What is the state of refrigerant leaving the metering device?
Lp Lt 75% Liquid 25% flash gas
What is the state of refrigerant leaving the evaporator?
Lp Lt super heated vapor
What is the biggest enemy for any refrigeration system?
Moisture and Air
When leak testing a system what is the maximum test pressure with the compressor in the system?
Never exceed the low side system pressure which is usually located on the evaporator
What types of inert gases are used to pressure test a system?
Nitrogen, Carbon Dioxide
Is it acceptable to use oxygen to leak test a refrigeration system?
No , it could cause an explosion
Where is the liquid receiver located?
Outside the condenser
What is the definition of Liquid Line
Refrigerant Line leaving the condenser and entering the metering device
What are the only two substances we want circulating in a refrigeration system?
Refrigeration and Oil
What is the definition of Discharge Line
Refrigeration line leaving the compressor and entering the condenser.
What is the definition of Suction Line?
Refrigeration line leaving the evaporator and entering the compressor
When changing from a vapor to a liquid refrigerants will ___________ heat.
Reject
Does subcooling add or remove sensible heat to the refridgerent?
Remove
Where does subcooling happen in a refrigeration system?
Right after the condenser. Before the metering device.
Where does superheat happen in a refrigeration system?
Right after the evaporator.
What is the definition of DOT 39 Containers
Seamless welded- service pressure not to exceed 80 % of test pressure. Highly pressurized gas cylinders.
Define subcooling.
Sensible Heat removed from the refrigerant that has been condensed in the condenser, but before it moves to the metering device.
Define superheat.
Sensible heat added to refrigerant after it has evaporated the evaporate.
Define the change of state of a substance.
Solid to liquid, Liquid to vapor
What are the three operation factors in a TXV
Spring, Bulb, and Evaporator pressure.
What is a BTU?
Stands for British Thermal Unit. It measuring the quantity of heat. It is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.
What is the definition of Critical Charge
System requires an exact amount of refrigerant (fixed metering device)
How do we measure the intensity of heat?
Temperature (Degrees Fahrenheit)
What two things affect heat transfer the most?
Temperature and surface area
What is the definition of Ambient temperature.
Temperature surrounding the device being worked on.
What is the definition of Latent heat of Condensation
The amount off heat needed to change a liquid to a vapor without a temp change
What is pump down
The controlled pumping of refrigerant in the high side to the low side to keep us from flooding the compressor.
What is a compound refrigerant gauge?
The low side gauge, which measures pressure and vacuum
What happens to the high side in a system that contains air?
The pressure increases
What is the definition of Atmospheric Pressure
The pressure normally present in the air
What is convection concerning heat transfer?
The transfer of heat by means of current or fluid.
What is radiation concerning heat transfer?
The transfer of heat by means of waves most commonly the sun.
What is conduction concerning heat transfer?
The transfer of heat through the touching of two objects.
What is the pressure temperature relationship with regard to temperature and boiling point?
There is a direct relationship between pressure temperature one goes up the other does.
What is the definition of Oil logging
To much oil getting stuck in the evaporator not making it back to the compressor.
What is the definition of Flooded coil
Too much refrigerant entering the coil
What is the definition of Flash Gas?
Vapor that is produced by the boiling point of liquid as it passes through the metering device
What is definition of sublimation
When a solid turns into a vapor and skips the liquid phase.
What is a saturated condition?
When the liquid and vapor exist together.
When changing from a liquid to a vapor, refrigerants will __________ heat?
absorb
What is the definition of Absolute pressure
gauge pressure (psig) + atmospheric pressure psia
