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Questions and Answers
What is the primary purpose of refrigeration?
What is the primary purpose of refrigeration?
Which states of matter are involved in the refrigeration cycle?
Which states of matter are involved in the refrigeration cycle?
What is the equation for calculating the volume of a cylinder?
What is the equation for calculating the volume of a cylinder?
How does mass differ from weight?
How does mass differ from weight?
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What determines the density of a substance?
What determines the density of a substance?
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What is specific volume?
What is specific volume?
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Why does wood float on water?
Why does wood float on water?
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Who pioneered modern air conditioning?
Who pioneered modern air conditioning?
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What does a micron reading below 500 typically indicate in a vacuum system?
What does a micron reading below 500 typically indicate in a vacuum system?
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What characterizes the trans-critical point of a refrigerant?
What characterizes the trans-critical point of a refrigerant?
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At which temperature does CO2 achieve its triple point?
At which temperature does CO2 achieve its triple point?
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What is the significance of the critical point in relation to refrigerants?
What is the significance of the critical point in relation to refrigerants?
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Which statement best describes enthalpy in a fluid?
Which statement best describes enthalpy in a fluid?
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What does the principle of energy conservation state?
What does the principle of energy conservation state?
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Which form of energy is associated with the position of an object?
Which form of energy is associated with the position of an object?
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What measurement is equivalent to 1 inch of mercury (inHg) in microns?
What measurement is equivalent to 1 inch of mercury (inHg) in microns?
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What is the relationship between specific volume and density?
What is the relationship between specific volume and density?
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If the specific volume of air is 13.33 lbs/ft³, what is its density?
If the specific volume of air is 13.33 lbs/ft³, what is its density?
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What is the specific gravity of red brass if its density is 548 lb/ft³?
What is the specific gravity of red brass if its density is 548 lb/ft³?
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How much heat is required to melt 1 ton of ice (2000 lbs) in terms of BTUs?
How much heat is required to melt 1 ton of ice (2000 lbs) in terms of BTUs?
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What does PSI stand for in the context of pressure?
What does PSI stand for in the context of pressure?
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If a container is 12” x 12” and contains 1 cubic foot of water weighing 62.4 lbs, what is the pressure exerted per square inch?
If a container is 12” x 12” and contains 1 cubic foot of water weighing 62.4 lbs, what is the pressure exerted per square inch?
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What effect does increasing pressure have on the specific volume of a gas?
What effect does increasing pressure have on the specific volume of a gas?
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What does 1 ton of refrigeration equate to in terms of heat transfer rate?
What does 1 ton of refrigeration equate to in terms of heat transfer rate?
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Study Notes
Refrigeration Fundamentals
- Refrigeration is the process of removing heat from a space or objects and rejecting it where it has little or no difference.
- It is used to preserve and transport food.
- It also aids in manufacturing commercial products and medical research.
- The first closed vapor compression system was developed in 1834 by Jacob Perkins.
- Willis Carrier pioneered modern air conditioning in 1902.
Learning Outcomes
- Demonstrate knowledge of the fundamental concepts of refrigeration.
- Demonstrate knowledge of the refrigeration cycle.
States of Matter
- Matter is anything that has mass and occupies space. It is the substance that makes up all physical objects in the universe.
- The four states of matter are solid, liquid, gas, and plasma.
- Two states of matter—liquid and gas—are present in a refrigeration cycle.
- The heat content and pressure determine the state of matter in a substance.
Volume
- Volume is the amount of space a substance occupies.
- Volume is important in relation to gases because it's related to pressure, temperature, and the number of molecules.
- Volume is three-dimensional and calculated using three measurements.
- Volume of a rectangle: Volume = Length x Width x Height
- Volume of a cylinder: Volume = π x radius² x height
Mass and Weight
- Mass is the amount of matter in a substance.
- Mass is the property of matter that responds to gravity.
- Weight is the force that matter applies to a surface while at rest.
- Earth's gravitational force is stronger than the moon's; therefore, a brick weighs more on Earth than on the moon.
Density
- Density describes the mass-to-volume relationship of an object or substance.
- Density is the mass contained in a particular volume.
- Comparing an object's weight per unit is finding the pounds per cubic foot (lbs./ft³).
- Water has a density of 62.4 lbs./ft³. Wood floats and iron sinks due to differences in density.
Specific Volume
- Specific volume is the volume that each pound of a specific gas occupies.
- Specific volume is different from total volume; the units are pounds per cubic foot (lbs./ft³), not cubic feet (ft³).
- The specific volume of air under standard conditions is 13.33 lbs./ft³.
- Specific volume and density are inverses of one another (specific volume = 1/density).
Specific Gravity
- Specific gravity is the density of a substance divided by the density of water.
- Water has a specific gravity of 1.
- If the specific gravity is greater than 1, the substance will sink in water.
1 Ton of Refrigeration
- 1 ton of refrigeration equals 12,000 BTU/hr.
- A ton of refrigeration melts 2,000 lbs. of ice at 32°F in 24 hours.
- Latent heat of fusion of ice is 144 BTU per pound.
Pressure
- Pressure is the force exerted by a gas or liquid per unit area on a surface.
- PSI (pounds per square inch).
- Pressure is force divided by area (Pressure = Force/Area).
- Example: Snowshoes spread weight out over a larger area, reducing pressure on the snow.
Pressure Calculations
- 1 cubic foot of water weighs 62.4 lbs. and exerts a downward pressure of 62.4 lbs. on a 1ft² (12" x 12") area.
- Pressure per square inch in a 12" x 12" container is 0.433 PSI.
- Pressure per square inch in a 24" x 24" container is 0.108 PSI.
Vacuum
- Vacuum is a condition in a closed system, relative to atmospheric pressure.
- Atmospheric pressure is 29.92 inches of mercury (inHg) at sea level.
- Lowering pressure below atmospheric pressure creates a vacuum.
- Industry typically measures vacuum in microns.
- 1 inHg = 25,400 microns.
- Atmospheric pressure is 759,168 microns.
Vacuum Applied
- Micron readings below 500 indicate a dry system.
- Final readings are taken after 30-minute decay tests with the pump off.
- Systems need to have low micron readings (e.g., 200 microns) for 30 minutes or more while the pump is on.
Critical Point
- The critical point is the highest temperature at which a gas can be condensed by pressure.
- It's a point on a pressure-enthalpy diagram defining critical temperature and pressure.
- No liquid refrigerant can be produced above a refrigerant's critical point.
Trans-critical Point
- Trans-critical refers to a process that occurs above a refrigerant's critical temperature.
- The refrigerant does not have a distinct liquid-to-gas phase transition.
- An example refrigerant is CO2, commonly operating above 88°F.
Triple Point
- A triple point is where a refrigerant exists as a solid, liquid, and gas simultaneously at the same time and temperature.
- CO2's triple point is -70°F and 75 PSIA.
- CO2 will often undergo sublimation (directly from solid to gas) below its triple point.
Enthalpy
- Enthalpy is referred to as "total heat content" in a fluid.
- Reference point for refrigerant enthalpy charts is -40°F.
- -40°F on the example chart equals 0 BTU/lb.
Energy
- Conservation of energy law states that energy cannot be created or destroyed, only transferred or converted.
- Energy is a fundamental force driving all physical processes and enabling work.
Types of Energy
- Kinetic energy is energy due to motion (e.g., a moving car).
- Potential energy is energy stored due to position (e.g., a stretched spring).
- Thermal energy is the total energy of particles in a substance, related to temperature (e.g., boiling water).
- Chemical energy is energy stored in the bonds of atoms (e.g., burning natural gas).
Work
- Work is equal to force multiplied by distance (Work = Force x Distance).
- Examples include lifting a weight or moving an object.
Power
- Power is the rate at which work is done.
- Power is typically expressed in horsepower (HP).
- One horsepower (HP) can lift 33,000 pounds one foot in one minute.
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Description
Explore the essential principles of refrigeration, including its historical development and significance in various industries. Understand the states of matter and how they interact within the refrigeration cycle to facilitate cooling. This quiz will enhance your knowledge in both refrigeration and basic physical science concepts.
