What is refrigeration - Answer-Refrigeration is the removing of heat from an object or mass and then dissipating that same heat in a place where it's presence will not be objectionable. "Refrigeration systems move heat"
The refrigeration process is made possible by - Answer-Boiling a refrigerant...
Refrigeration Machine Operator Course
– Turner Exam Questions with Correct
Answers
What is refrigeration - Answer-Refrigeration is the removing of heat from an object or
mass and then dissipating that same heat in a place where it's presence will not be
objectionable. "Refrigeration systems move heat"
The refrigeration process is made possible by - Answer-Boiling a refrigerant
BTU "British Thermal Unit" - Answer-A BTU is the quantity of heat needed to raise one
pound of water one degree Fahrenheit.
Specific Heat - Answer-The specific heat of a substance is the number of BTU's
required to raise the temperature of one pound of that substance 1 degree Fahrenheit.
Temperature - Answer-Temperature is the intensity of heat.
Fahrenheit to Centigrade - Answer-F = (1.8 x C) +32
Changes of state are accompanied by - Answer-The removal of heat
Sensible Heat - Answer-Heat which is associated with a change in temperature
Latent Heat - Answer-Heat which is associated with a change in state.
Latent heat of fusion - Answer-Heat energy needed to change the state of a substance
without a change in temperature from a liquid to a solid or a solid to a liquid. In the case
of water, from a solid, ice to water or vice-versa.
Latent heat of vaporization - Answer-Heat energy added to change the state of a
substance without a change in temperature from a liquid to a vapor, or in the case of
water, from a liquid to steam (vapor). In the case of refrigerants, it is a change from
liquid to gas (in the evaporator).
Latent heat of condensation - Answer-heat energy removed to change the state of a
substance without a change in temperature from a vapor to a liquid.
Superheat - Answer-Superheat is heat added to steam or refrigerant gas (vapor), to
raise the temperature above its boiling point. Each additional degree above the boiling
temperature is a degree of superheat.
,Sublimation - Answer-Sublimation is a process whereby a substance changes from a
solid to a vapor without passing through the liquid state. Ex: Dry ice.
Conduction - Answer-Conduction is heat transfer by contact.
Convection - Answer-Convection is heat transfer by the movement of a fluid, usually
water or air.
Radiation - Answer-Radiation is heat movement through space by shining, just as light
is radiated. Ex: The sun.
One Ton - Answer-2000lbs
2000 lbs x 144 btu/lbs - Answer-288,000 BTUs
One ton of refrigeration - Answer-based on the cooling capacity produced by a 2000
block of ice.
144 BTUs - Answer-must be removed from one lb of water (at 32F) to form one lb of ice.
One Ton of refrigeration - Answer-capable of moving 288,000 BTUs/Day (24hrs)
Pressure - Answer-The force exerted by a fluid (liquid or vapor) which has been
uniformly distributed over a surface and is measured per unit area.
p=f/a - Answer-Pressure
Barometer - Answer-A device for predicting weather changes.
29.92 - Answer-The earth's pressure at sea level.
29.92 converted to "pounds per square inch" - Answer-14.7 psi
PSIG - Answer-Pounds per square inch gauge.
Pressure Gauge - PSIG - Answer-Indicates values of pressure above atmospheric
pressure. Value starts at 0.
HG - Answer-Inches of Mercury
,Vacuum Gauge - HG - Answer-Indicates values of pressure below atmospheric
pressure. The values of pressure on a vacuum gauge descend down to 29.92Hg,
indicating that virtually no pressure is exerted (perfect vacuum)
PSIA - Answer-Pounds per square inch absolute - Absolute pressure values are based
on a perfect vacuum.
Pressure Gauge - 0 Psig-300Psig above atm - Answer-Installed on the discharge side
of a compressor
Compound Gauge - 30 hg - 100 psig - Answer-psig above atm & vacuum below atm,
Installed on the suction side of a compressor.
Gauge Manifold - Answer-Makes it possible for a service mechanic or operating
engineer to determine both the high and low side operating pressures in a system that
is not equipped with permanently installed pressure gauges. Used while adding or
removing refrigerant from a system.
Gauge Size - Answer-Generally, the more accurate gauges are larger and more costly.
Gauge Case and Housing - Answer-Stainless steel, black, ABS, painted steel, brass
and fiberglass reinforced thermoplastic are standard case materials. Stainless, brass or
ABS cases are recommended for outdoor service.
Psig to psia - Answer-Psia = psig + 14.7
Psia to Psig - Answer-Psig = psia - 14.7
Vacuum pressure to Psia - Answer-Psia = (30-Hg)/2
Barometric Pressure to Psia - Answer-Psia - = Hg x .491
Charles Law - Answer-There is a direct relationship between the pressure, temperature
and volume of a vapor or gas.
Dalton's Law of partial pressures - Answer-Dalton's law states that more than one gas
placed in a container will exert a pressure that is an accumulation of the pressures that
each gas exerts.
Refrigerants - Answer-Are the working fluid used to transfer heat through refrigeration
systems.
Desirable properties of refrigerants - Answer-Each refrigerant has desirable properties
that distinguish it from all others.
, Favorable properties of refrigerants - Answer-There is no one refrigerant that
demonstrates only favorable properties.
Refrigerants should produce maximum refrigeration per cubic foot of vapor pumped. -
Answer-A compressor, depending on it's size can only pump a given amount of
refrigerant vapor. The refrigerant used should absorb the greatest amount of btu's
allowed for that particular size.
Refrigerants should have condensing pressure suitable for the type of compressor
used. - Answer-The compressor raises the pressure of a vapor to increase the
temperature it can be condensed into a liquid at.
Refrigerants should have an evaporating pressure suitable for the type of compressor
used. - Answer-A systems compressor and metering device must maintain the pressure
inside of the evaporator. This pressure determines the boiling point of the refrigerant in
the evaporator.
Refrigerants should be stable. - Answer-Refrigerants are made up of chemical mixtures.
Above a certain temperature, they will separate into the elements. It is necessary that
refrigerants breakdown temperatures be well above the operating temperatures of the
system.
Refrigerants should have no effect on metal. - Answer-Refrigerants must not corrode or
react with the metals used in the refrigeration system.
Refrigerants should have no effect on oil. - Answer-The refrigerant must have no
harmful effect on the selected lubricating oils. Besides possible sludge formation there
is also the danger of refrigerants mixing with and thinning the oil.
Refrigerants critical temperature should be well above the condensing temperature. -
Answer-The critical temperature is the temperature above which it is impossible to
condense a vapor regardless of the pressure applied.
Refrigerants should be non-poisonous and nonirritating (non-toxic). - Answer-A
poisonous or highly irritating refrigerant could create a hazard in case of leakage from
the system.
Refrigerants should be non-flammable. - Answer-A flammable refrigerant could create
an even greater danger in case of leakage, due to the possibility of fire or explosion.
Refrigerants should be available at reasonable prices. - Answer-There has recently ben
an attempt to regulate refrigerants that are threats to the environment. Operators of
systems that use CFCs must take great care in handling these refrigerants since
replacing it would be difficult and expensive.
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