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90 Cards in this Set
- Front
- Back
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How is energy lost in a duct system |
By turbulent air |
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Since it is not possible to measure the volume air in a duct system how is volume determined |
By measuring the air pressures |
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What are the 3 types of pressure in a duct system |
Static pressure, velocity pressure, and total pressure |
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How do you turn velocity (W.G.) pressure into A velocity (FPM) |
4005 x square root of velocity pressure (w.g.) |
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What does the inner tube of a pitot tube Measure |
Total pressure |
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What is the outside tube Measure |
Static pressure |
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What size are the smaller holes on the outer tube |
.04 diameter |
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What are multiple readings across a duct known as |
Traverse |
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How many traverse readings are there across small ducts |
6 to 12 |
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How many traverse readings across very large ducts |
20 to 40 |
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What scale is used across the inclined manometer |
10 to 1 |
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Why must a specific liquid be used in a manometer |
Scale is calibrated for that fluid |
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What common gauges are used to measure the velocity at the supply and exhaust outlets |
A velometer and an anemometer |
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How does a velometer Take a reading |
Air passes through the left port moves a vane which actuates the indicator |
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What other readings can I the velometer take with proper fittings |
Static pressure total pressure and the velocity |
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What do the dials on an anemometer read |
Linear feet of air passing for a measure length of time |
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What is a sling psychrometer used to measure |
The relative humidity of the surrounding air |
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What is the thermometer with the cloth cover called |
Wet bulb |
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What is the thermometer without the cover |
Dry bulb |
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What guage is required to measure minute changes in pressure |
A manometer |
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How much pressure will 1PSI support |
A column of water 27.7" high |
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What are ducts and fan pressures quoted in |
Inches of water Gauge instead of pounds per square inch |
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What are the different names for fans |
Air moving device, blower, exhauster, and others |
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What are the 2 classifications of fans |
Axial and centrifugal |
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In what direction does an axial yo fan move air |
In a straight direction orParallel to the shaft |
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What are axial fans excellent for |
Large volume applications where high noise levels are not so important |
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What to ways can axial fans be driven |
Direct drive with the motor inside the casing or belt driven with the motor on the outside of the casing |
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What are the 3 types of axial fans |
Propeller, tube axial, Vane axial |
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What are tube axial fans more suited for |
Exhaust applications |
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What are vane axial fans suited for |
Ventilation applications |
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What are the advantages of the tube and vane axial fans |
Smallest size, lightweight, and straight through airflow often eliminates elbows in the duct work |
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What are the advantages of the tube and vane axial fans |
Smallest size, lightweight, and straight through airflow often eliminates elbows in the duct work |
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In what direction does centrifugal fans move air |
Perpendicular or right angle |
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In what application are centrifugal fans most often chosen for |
For Comfort applications Because it has a wide range of quiet efficient operations at comparatively High pressures |
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How can the airflow be varied to meet the air distribution requirements |
By Simple adjustments to the fan Drive |
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What three types of blades can the centrifugal fan be made with |
Forward curved, backward curved, or straight blades |
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How can you determine the direction of rotation of a centrifugal fan |
By observing the discharge from the motor side of the fan |
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How does centrifugal fan with forward curved blades move |
Slowly |
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What are fans with forward curved blades generally used for |
Producing High Volumes at low static pressures |
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What are forward curved blade not suitable for |
Material Handling because of its blade configuration |
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What can happen if the static pressure increase with forward curved blades |
The motor May overload |
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How fast do backward inclined fans travel |
About twice as fast as the forward curved fan |
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What is the backward Inclined fan Not designed for |
Material Handling |
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What does the tubular centrifugal fan permit |
Straight line duct installation |
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What are the two basic principles of refrigeration |
Heat transfer takes place from a warm object to a cooler object, And heat loss from the warmer object is gained by the cooler object It does not disappear |
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The btu is the measurement of the quantity of heat required to raise what |
One pound of water one degree Fahrenheit, 55 cubic feet of air one degree Fahrenheit Or one cubic foot of Air 55 degrees Fahrenheit |
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What gives the intensity of heat |
The degrees in Fahrenheit or Celsius |
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In what two ways can heat be described |
By its quantity or its intensity |
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In what three ways does heat transfer occur |
Conduction, convection, and radiation |
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What is conduction |
Heat transfer through a substance by the transfer of heat energy from particle to particle |
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What is convection |
Heat transfer due to the movement of the heated body |
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What is radiation |
Radiation is heat transferred through space Even through a vacuum |
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How does radiant heat travel |
In a straight line and may pass through a vacuum, air, some gases, some liquids, and a few solids such as glass And quartz |
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In what two ways are heat energy classified |
Sensible heat and latent heat |
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What is sensible heat |
Any heat that raises the temperature of a substance without changing its state |
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What is latent heat |
Heat the cause of the change of state not a change in temperature |
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How can latent heat change |
From a solid to a liquid, a liquid to a solid, a liquid to a vapour, and a vapour to a liquid |
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What is latent heat of fusion |
Heat required to change a solid into a liquid without a change in temperature |
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What is a latent heat of vaporization |
The heat required to change a liquid into a vapour without increasing the temperature of the fluid |
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Any liquids used in refrigeration boil at what temperature |
0 degrees Fahrenheit under ordinary atmospheric pressure |
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What is relative humidity |
Ratio of actual water vapour to the maximum amount that the air can hold under the same conditions |
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How is relative humidity expressed |
As a percentage and measured in grains |
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What is dew point |
When the temperature of the air drops to a point when they absorb water must leave |
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At what humidity is the effective temperature and the actual temperature the same |
50% relative humidity |
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At what rate Will 1 ton of ice absorbs heat at per hour |
12000 BTU per hour |
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How many BTUs does it take to melt 1 lb of water |
144 BTU |
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What is the capacity of a refrigeration system that can remove 12000 BTU per hour |
A 1 ton capacity |
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At what rate can a 5-ton Air conditioning unit absorb heat at per hour |
60000 BTU per hour |
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In what other ways can cooling be produced |
To allow liquid refrigerant to vaporize inside a coil |
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What are the Terms And components of mechanical Refrigeration units |
Mechanical Refrigeration, refrigerant, evaporator, compressor, condenser, and metering device |
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What is mechanical Refrigeration |
Mechanical refrigeration system uses a compressor Remove the refrigerant in the evaporator to the condenser |
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Where is the Evaporator or cooling unit Located |
On the low pressure side |
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Where is the compressor located |
On the high pressure side |
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Where are heat pumps effective |
In Both warm and cold climates |
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How does a heat pump operate in warm climates |
Mostly be in cooling mode with some time spent in the heating mode |
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What is a reversing valve |
Changes the direction of the refrigerant For a heat pump to Supply heating or Cooling |
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How does a reversing valve in heating Mode work |
The condenser coil is in the Air Duct Heating the home |
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How does a reversing valve in cooling Mode work |
The evaporator coil is in the air duct cooling the home |
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In a split system heat pump where are the coils located |
1 coil is located in the air handling system within the home and the other coil mounted in a louvered container Outdoors |
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What is the refrigerant path called |
A circuit |
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What are circuit classified according to |
The type of heat source and heat sink |
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What is a heatsink |
Where heat is dissipated to |
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What is air-to-air |
Uses air as both the heat source and the heat sink |
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What is an earth to air circuit |
Has one coil embedded in the Earth as a heat Source or sink And the other coil in the duct system to supply the conditioned space with warm or cool air |
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What is a water-to-air circuit |
Uses water as a heat source And are to transmit or remove heat from the conditioned space |
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What is a water to water circuit |
Use water as both the heat source and the heat sink |
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On a water to water circuit How can Heating and Cooling be achieved |
By reversing the refrigerant flow or by switching the water path instead |
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What are the components on the high side of Cooling equipment |
The condenser coil, condenser fan and compressor |
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What are the components on the low side of a cooling system |
The evaporator coil and metering device |
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What is the cycle of refrigerant |
Refrigerant from evaporator to the compressor , Compressor increases pressure And pumps it to the condenser , increase pressure raising the temperature of the refrigerant And surrounds condenser , loss of heat causes refrigerant to change to a liquid, Metering device opens As pressure is built up in the condenser , liquid passes through Metering device To the evaporator , lower pressure in evaporator causes refrigerant to change to a vapour , Refrigerant absorbs heat In principle of heat of vaporization Resulting in the refrigerant cycle , compressor pumps the refrigerant vapour How did the evaporator And the cycle is repeated |
