Fundamentals of Refrigeration
0 PSIG is where gauges are calibrated to read to sea level?
True
It takes a lot more heat to produce a change of state than to produce a change of temperature?
True
Refrigerant can be found in the refrigeration system as a superheated gas, a saturated mixture, or a sub-cooled liquid?
True
Refrigerant can be found in the refrigeration system as a superheated gas, a saturated mixture. or a sub-cooled liquid?
True
Superheated gas is gas heated above it boiling or saturation point?
True
T or F Semi-hermetic compressors can be serviced in the field?
True
T or F The job of a TXV is to maintain super-heat.
True
The pressure and temperature of any saturated mixture will change together?
True
The pressure of a cylinder of saturated refrigerant with 5 pounds of refrigerant will have the same pressure as a cylinder with 15 pounds of refrigerant, if the same temperature?
True
The pressure of a cylinder of saturated refrigerant with 5 pounds of refrigerant will have the same pressure as a cylinder with 20 pounds of refrigerant, if they are both at the same temperature?
True
In air conditioning we use Mercury Columns to measure?
Vacuum
Pressure is force, and force is normally expressed as?
Weight
What is saturation point?
Where gas turns to liquid or liquid turns to gas.
What is the super-heat for a typical cycle as discussed in class
10°
Standard atmospheric pressure at sea level and a temperature of 59 degree is?
14.7
High pressure gauges are preset at "0" which represents?
14.7 PSIA
What is the static pressure for an r-22 unit @ 96°?
185 PSIG
What is the static pressure for a NU-22b unit @ 96°?
187 PSIG
How do we calculate Sub-cool?
1st convert discharge pressure into temperature using the PT chart. Then Condenser saturation temperature minus liquid line temperature.
How do we calculate Super-heat?
1st convert suction pressure into temp using PT chart. Then suction line temp minus the evaporator saturation temp.
Energy that can neither be created or destroyed is a good definition for?
1st law of thermodynamics
What is the TD of a 10 seer evaporator coil?
20°
What is the static pressure for an 410a unit @ 96°?
301 PSIG
What is the TD of a 10 seer condensing coil?
30°
In a typical cycle what is the evaporator saturation temp?
40°
What is the sub-cool for a typical cycle as discussed in class?
5°
What is the design return air temperature for evaporator coils?
70°-80°
A heat transfer process requires?
A heat source and a heat sink
A heat transfer process requires:
A heat source and heat sink
Heat flows from?
A higher to a lower temperature
What controls the flow of refrigerant to the evaporator?
A metering device
Compound gauges are used to measure pressures?
Above and below atmospheric pressure
Systems that use fans or pumps to increase convection are called?
Active
Systems that use fans to increase convection is:
Active
When using copper to absorb heat from the air, its heat transfer rate can be increased by?
Adding Fins to the tube
Absolute pressure is the pressure without regard to the current?
Atmospheric pressure
Barometric pressure is a term used for the current?
Atmospheric pressure
The gauges used in the HVAC/R field are used to measure pressure compared to?
Atmospheric pressure
What is the tank color for Nu-22b
Blue
Saturated means what?
Completely full
The word saturated means?
Completely full
Gases start giving off heat when they:
Condense to a liquid
In the conduction process the rate of heat transfer will depend on the ability of the material to?
Conduct heat
The heat transfer between the closely packed molecules of a substance, or between substances that are in good contact with one another describes?
Conduction
Heat transfer through a flowing medium is a description of?
Convection
What is the condenser split?
Difference between ambient air temp and out going condenser air temp.
If you double the surface area of an evaporator coil, you will also __________ the heat transfer rate.
Double
A manometer is used in the HVAC/R field to measure humidity?
False
A perfect vacuum using absolute measurement would be 24.7 PSIG?
False
Any pressure less than atmospheric pressure is called a pressure?
False
Heat travels to Heat. True or False
False
High pressure gauges can only indicate pressure below atmospheric pressure?
False
T or F Hermetic compressors are field serviceable:
False
T or F Two types of txv's are internal and top mount styles.
False
The higher the pressure of a saturated mixture the, the temperature will remain the same?
False
The operation of HVAC/R equipment depends on controlling system design?
False
Unstable refrigerant is when a liquid is cooled below its boiling, or saturation point?
False
The process of moving a fluid using mechanical means to increase heat transfer is called?
Forced Convection
Moving fluid using mechanical means to increase heat is:
Forced convection
How does heat travel?
From hot to cold
Thermodynamics is a science that deals with?
Heat and the movement of energy
Metals with what level of conductivity are used within the refrigeration system itself, because it is desirable that rapid heat transfer occur in both the evaporator and condenser?
High
What is the state of refrigerant in the suction line?
LPLTV
Heat that changes state but not temp is?
Latent heat
What is the tank color of R-22
Light Green
What is the tank color for R-410 a
Light Maroon
Higher temperature and higher relative humidity both produce?
Lower atmospheric pressure
The job of any refrigerant system is to:
Move heat
Radiant energy will heat.....
Objects
Radiant energy will heat?
Objects
Radiant heat energy heats?
Objects
Systems that rely entirely on natural convection are called?
Passive
What do we call systems that rely entirely on convection?
Passive
Absolute pressure is usually stated in?
Pounds per square inch Absolute
A Manometer is used in the HVAC/R field to measure?
Pressure
Pressures above atmospheric pressure are measured as a positive:
Pressure
The boiling point, or saturation temperature, of a refrigerant is controlled by?
Pressure
Heat transfer through waveforms is a description of?
Radiation
What type of compressor has clearance space?
Reciprocating
The condensing coils job is to?
Reject heat absorbed from inside the house.
What do the colored scales on you gauges read?
Sat. temps
The heat transfer process that caused a substance to change temperature, BUT not change state is called?
Sensible Heat Process
The heat transfer process that causes a substance to change temperature, but not change state is called?
Sensible Heat Process
Heat that can be felt or measured is called?
Sensible heat
Heat that can be felt or measured is?
Sensible heat
When you remove heat from a saturated gas?
Some of the gas changes to a liquid
When you add heat to a saturated liquid?
Some of the liquid changes to a gas
A factor that allows that technician to calculate the exact amount of heat required to produce a specific temperature rise in a substance is called?
Specific heat capacity
When a liquid is cooled below its boiling, or saturation point it is called?
Sub-Cooled Liquid
What are the 3 metering devices we covered
TXV/TEV, Cap tube, Fixed orifice
What is the evaporator split?
Temperature difference between the return and supply air temp.
What is super-heat?
The amount of heat added to a gas above its saturation point
What happens to a saturated mixture if enough heat is added to boil all the liquid to gas?
The gas temperature will rise.
What is Sub-cool
The heat removed from a liquid below its saturation point
The higher the temperature difference between two objects?
The more quickly heat will flow between them
The higher the temperature difference between two objects
The more quickly heat will flow between them.
HVAC technicians work with?
Thermal Energy
