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108 Cards in this Set
- Front
- Back
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Refrigeration |
Removal of heat by fluid or mechanical means, transporting that he somewhere unobjectionable |
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Refrigerant |
Any fluid which boils and absorbs heat |
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Energy |
The ability to do work, can be converted, but not created or destroyed |
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Force |
Applied to a body at rest, causes it to move |
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Work |
Force x distance = ft/lb |
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Power |
Is the time rate of doing work. Power = w/t = (f x d)/t |
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Q1 AC coils should be above freezing and what temperature |
40°F |
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What is the temperature drop between the supply and return air |
17-21°F |
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What does CFM stand for? |
Cubic feet per minute |
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How many CFM does one ton of cooling required? |
400 CFM |
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Ambient temperature is the temperature of the air around what? |
The condenser coil, motor, or other device in question |
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Condensing temperature is |
Ambient temperature + 30°F |
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Evaporator temperature is |
Box - 10°F |
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Liquid can boil only at or above what? |
Its evaporation temperature |
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Saturation temperature |
Boiling / condensing temperature at a certain pressure |
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What is superheat |
Degrees above saturation temperature (a vapor) |
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What is subcool |
Degrees below saturation temperature (a liquid) |
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What does the Accumulator do? |
Protects the compressor from liquid refrigerant |
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Which devices are attached to both lilo and high side of a system? |
The compressor and metering device |
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What are the seven metering devices |
TeV, AeV, capillary tube, fixed orifice or piston, Eev, LSF, HSF |
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What is a TEV |
Thermostatic expansion valve |
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What is an AEV |
Automatic expansion valve |
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What is an EEV |
Electronic expansion valve |
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What is a LSF |
Low side float |
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What is a HSF |
High side float |
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What was used for refrigeration in the 18th century |
Ice |
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Specific gravity |
(relative density) - comparison of a fluid to an equal amount of water |
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Enthalpy |
The measure of the energy content of a substance |
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Density |
A substance is mass per unit of volume |
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What are the three states of matter |
Solid, liquid, gas |
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What method does most matter use to change its physical state |
Addition or removal of heat |
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Temperature |
Is an indication of the degree of warmth |
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Q1 Heat always moves from where to where |
Warm to cold |
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What is the formula to convert Celsius to Fahrenheit |
F=9/5 x C + 32 |
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What is the formula to Fahrenheit to Celsius |
C=(F-32) X 5/9 |
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Q1 Sensible heat |
Heat required to change the temperature of a substance |
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Q1 Latent heat |
Heat required to change the state of a substance with no change in temperature |
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Degrees |
Measures intensity of heat |
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BTUs |
Measure of the quantity of heat |
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BTU is what |
The heat required to change the temperature of 1 pound of water 1°F |
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Specific heat capacity |
The heat required to change one pound of a substance by 1°F |
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One ton of refrigeration represents the heat energy absorbed when 1 ton of ice melts in |
1 24 hour day |
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One ton of refrigeration equals |
12000 BTUH cooling capacity |
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Kinetic energy is |
Energy of motion (energy doing work) |
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Atmospheric pressure is what at sea level |
14.7 psia |
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What does psia stand for |
Pounds per square inch absolute |
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What does psig stand for |
Pounds per square inch gauge |
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What are the reference points for psig and psia |
Psig is atmospheric, psia is a perfect vacuum |
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Barometric pressure equals atmospheric pressure measured in |
Inches of mercury (in hg) |
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Q1 What is the first law of thermodynamics |
Energy cannot be created or destroyed it can only be converted |
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Q1 What is the second law of thermodynamics |
Heat flows from warm bodies to colder bodies |
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What is a perfect vacuum in inches of mercury |
29.921 |
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How deep of a vacuum must be pulled in inches of mercury |
29.9 |
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What are the methods of heat |
Radiation, conduction, convection |
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How is heat transferred in radiation |
Heat is transferred by infrared rays |
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How is heat transferred by conduction |
Flow of heat by molecular vibration or heat transfer within the same body by physical contact |
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How is heat transferred by convection |
Heat transfer by way of fluid or air or gases, I can be forced or pumped or natural |
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Co2 exists in two states and changes state from solid to gas by means of |
Sublimation |
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What is an example of an insulator |
Glass |
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What is an example of a conductor |
Copper |
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What color absorbs more heat |
Dark colors |
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What colors and services absorb less heat |
Light colors and reflective surfaces |
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Refrigerant should be operated at temperatures ________ their critical temperatures |
Below |
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Static pressure |
Pressure in an enclosed space affected by temperature. |
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What is the maximum allowable temperature in a refrigerator. |
40°F |
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What is the maximum allowable temperature of a freezer? |
0°F |
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Is it acceptable to mix refrigerants? |
No, never. |
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What percentage of fill is considered a full cylinder? |
80% |
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The two main classifications of energy are |
Potential and kinetic |
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The law of conservation of energy states that |
Energy can be changed from one form to another, energy cannot be created, energy cannot be destroyed |
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_________ is the rate at which work is performed |
Power |
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Temperature measured on the _______ scale can be converted to Fahrenheit temperatures by subtracting 460 degrees |
Rankine |
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The _______ of a substance is the amount of heat editorially to change the temperature of 1 pound of a substance by 1° Fahrenheit or one kilogram of the substance by 1 Kelvin |
Specific heat capacity |
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Enthalpy is _________ |
The total amount of heat in a substance, calculated from an accepted reference temperature |
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_________ is the method by which heat is transferred from one substance to another through the circulating medium, such as air or water |
Convection |
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A gas is any physical substance that has __________ |
No definite volume or shape and expands to fill its container |
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Heat energy can be categorized as latent heat and __________ heat |
Sensible |
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Latent heat is heat added to a substance that _______ |
Causes the substance to change state |
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According to Pascal's law, if a piston applies pressure to fluid in a sealed cylinder, ________ |
The pressure will be applied equally and undiminished to all services of the cylinder |
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Critical pressure is _________ |
The minimum pressure at which a gas at its critical temperature can condense |
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According to the combined gas law, if the pressure of a gas is held constant as its temperature is increased, then the volume of the gas ________ |
Increases |
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Condensate will be produced in a saturated vapor if _______ |
The pressure of the vapor is increased and the temperature is decreased |
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The density of a substance is defined as the mass of the substance ________ |
Divided by its volume |
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The weight of a substance is defined as _________ |
The force of gravity acting on the substance |
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If a substance has a specific gravity less than 1.0, it means that the substance __________. |
Is less dense than water |
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The cooling effect can be generated through __________. |
Air exchange, pressure change, state change |
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A ton of refrigeration effect is defined as the __________ |
Amount of heat energy absorbed when a ton of ice melts during one 24 hour day |
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_________ Refrigerant is like a dry sponge that has the ability to soak up a lot of water |
Low pressure vapor |
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_________ Refrigerant is like a soaking wet sponge that cannot absorb more water |
High pressure vapor |
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From the metering device through the evaporator to the compressor cylinder is the ________ side of the system |
Low |
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From the compressor exhaust to the metering device is the _______ side of the system |
High |
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Using suction, a compressor drawers in refrigerant by creating _________ in the evaporator |
Low pressure |
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Using the process of compression, a compressor increases refrigerant _________ |
Pressure and heat content |
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Commonly use in refrigeration compressors, __________ compressors use a back and forth or up and down motion |
Reciprocating |
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Hey heat-exchanging device designed to expel or reject heat is a(n) _________ |
Condenser |
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A condenser that uses a fan to remove heat more quickly is called a ___________ condenser |
Forced air |
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Heat flow can best be described as _________ |
Flowing from hot areas to cold areas |
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A storage tank for liquid refrigerant on the high side of the system is a(n) __________ |
Liquid receiver |
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A refrigeration system with a(n) ____________ metering device does NOT use a liquid receiver |
Capillary tube |
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Into which tank can a technician pump a refrigeration systems entire refrigerant charge to perform service |
Liquid receiver |
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The high pressure line is sometimes called the _________ line |
Liquid |
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To protect a system from dirt, moisture, metal, and other degrees, install a(n) __________ |
Filter drier |
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A heat exchanging device designed to absorb heat is a(n) _________ |
Evaporator |
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The instantaneous evaporation of liquid refrigerant in an evaporator is called __________ |
Flash gas |
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A storage tank that traps liquid refrigerant on the low side of the system is a(n) _________ |
Accumulator |
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Accumulator will function best with its inlet positioned ____________ the tank |
At the top of |
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An accumulator will function best with an outlet position ___________ the tank |
At the top of |
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The low-pressure line is sometimes called the _________ line |
Suction |
