Refrigeration Flashcards
Gas plant refrigeration uses what type of refrigerant
Propane
Industrial liquid over feed systems use what type of refrigerant
Ammonia
Matter is made up of what three molecules
Gasses
Liquids
And solids
Define radiation
Radiation is a vaccume a heat transfer by electro magnetic waves
Warm objects radiate more heat than colder ones with the overall effect that cold objects gain more heat by radiation than warm objects
Convection is
Heat transfer by moving matter.
When heated a fluid decreases in density, and the warm fluid that is high density pushes the warm fluid upwards
Define latent heat
It is added or removed heat that pulls the molecule apart (ie ice melting)
At what point does water turn into steam
Once it reaches 100c (212f)
What are the two types of heat
Latent heat
Sensible heat
Define sensible heat
can be measured and is the measure of vibration rate of molecules
Define energy
The capacity to do work and may consist as
potential
Or
Kinetic
Potential energy means what
Means that it is at rest and capable of doing work
What are the typo main types of energy conversion
Electrical converted to mechanical
Mechanical converted to heat
A liquid does what as it boils
Obsorbs heat
A vapour does what as it condensates
Releases heat
The quality of heat required to completely vapourize one Kilo of liquid(at boiling temp is called
Latent heat of vaporization
Reverse the process and you have
Latent heat of condensation
What temperature does propane boil at
-42*c under the pressure of one atmosphere
What temperature does pure ammonia boil at
-33*c under the pressure of one atmosphere
The low pressure side of a refrigeration cycle starts where
From the outlet of the metering device and continues as the refrigerant flows to the inlet of the compressor
The high pressure side of a refrigeration cycle stats where
From the outlet of the compressor and continues as the refrigerant flows to the inlet of the metering device
Circulating refrigerant has four major processes
They are. in this order
Condensation
expansion
evaporation
compression
What is the main purpose of the compressor in the refrigeration system
The compressor circulates and maintains a low pressure in the evaporator
Simultaneously it maintains a high pressure in the condenser
What is the most common compressor in refrigeration
Reciprocating compressor
What is the main purpose of the condenser in the refrigeration system
Reject heat from the circuit
What is the main purpose of the metering device in the refrigeration system
Throttles and regulates the flow of refrigerant, also maintains the pressure difference between evaporator and condenser
Aside from oil what is another substance that compressors should never pump
Liquid refrigerant as it resists compression
What two reciprocating compressors are generally used in refrigeration
Screw
Centrifugal
The temperature above the condensing or boiling temperature of the refrigerant is called
Supper heat
What heat transfers by moving matter, separating one from the other hirer on too colder on the bottom
Convection
What transfer is caused by physical contact
Conduction
The greatest heat transfer in a refrigeration system occurs in the
Evaporator
Or
Condenser
Evaporator takes in mor BTUs than condenser can give off
Liquid overfeed at the evaporator results in a mixture of liquid and gaseous refrigerant leaving the evaporator. What is used to prevent the liquid from entering the compressor suction
A low pressure receiver
Liquid settles on the bottom while compressor suction suck the vapour from the top
What effect does lowering the boiling point have on a liquid
Lowers the boiling point
Why is it important refrigerant has a low boiling point
Lower boiling point means it can reach a lower pressure
in the flooded system, the brine tubes are immersed
liquid refrigerant
what does liquid-feed mean?
low pressure refrigerant is stored in a tank where is can be pumped where it can be pumped through evaporators again without having to go through an entire compression cycle
why is liquid overfeed system commonly used in industrial applications
It can have multiple evaporators for one system
what insulation category does Cellular glass fall into
Cryogenic
what insulation category does fiberglass, rock-wool, and Vermiculite fall into
Thermal
what insulation category do bricks and Gunnite mixture fall into
Refaractory
ammonia flooded systems require an oil separator because
the oil does not return to the compressor
liquid levels in a liquid overfeed low pressure receiver is monitored/controlled by
float switch
lithium bromide (absorption) refrigerant uses ___________energy to produce the refrigerant effect
Heat
what is used as the refrigerant in the lithium bromide absorption system
water
what shut down cycle must a chiller run through to prevent crystallization
dilution cycle
in an abortion system the heat ex changer serves what vital function
heats diluted solution and cools the concentrated solution
the metering device on a compression refrigeration system can be what three devices
capillary tube, fixed orifice, or a thermostatically controlled expansion valve.
boiling temp of a liquid, and condensing temp of a vapour can be at the same temperature as long as
pressure exerted on the fluid is the same
as refrigerant turns into a vapor it absorbs what kind of heat
latent heat of vaporization
when refrigerant condenses into a liquid the vapor rejects what type of heat
latent heat of condensation
1 BTU = The amount of heat required to
raise 1 LB of H2O 1*F
The lower pressure side of a metering device =
95%liquid 5% gas
if pressure on water was lowered water would boil at a higher or lower temperature
lower temperature
condenser pressure is controlled by
condensing capacity
what is a heat exchange that draws heat into the vapor compression cycle
the Evaporator draws heat into the vapor compression cycle
systems are designed to minimize or illuminate pressure through the
evaporator
what is the purpose of the liquid line dryer system
removes small dirt particles, moisture, and acid
what two things must a refrigerant do in low pressure, low temperature
absorb heat, evaporate (boil),
in a refrigeration system, pressure on the low side is controlled by
compressor capacity
in a refrigeration system, pressure on the high side is controlled by
condenser capacity
name a heat exchange used in vapor compression refrigeration systems
shell and tube
in which component is thermal energy absorbed by the refrigerant
evaporator
what is the name for heat energy that causes temperature change
sensible heat
in which component is refrigerant de-super heated, condensed and sub-cooled?
conensor
what effect does the compressor have on the boiling/condensing temperature of the refrigerant
raises the boiling point
what is the refrigerant used in lithium bromide Chillers
water
what effect does the pressure decrease have on the boiling point of a liquid
it Decreases
what id the purpose of a compressor in a refrigeration system
create low pressure in the evaporator, high pressure in the confessor
why must pressure be raised before sending refrigerant to the condenser
to raise the condensing point so gas can become liquid
what happens to refrigerant in the evaporator
heat energy is absorbed and it changes into a gas
what is an auto purge used for
to vent non condescension gas from a refrigeration system
what is a liquid overfeed system
an excess of liquid is supplied to the evaporator
what type of condenser uses air flow and water evaporation
evaporator
what is a hermetically sealed compressor
its a non serviceable vessel that holds the compressor, compressor driver, oil and refrigerant, and requires no shaft seal for compressor
what is the upside to liquid over feed
they can use multiple evaporators for multiple different temperature applications
