So Flashcards
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Several common forms of energy are heat chemical electrical and mechanical. in the following right each blank space the appropriate form of energy
A - oil burned in a boiler converts it’s ( heat ) energy to. ( chemical ) energy
B - An electric motor converts ( electrical ) energy to ( mechanical ) and ( heat ) forms of energy
Temperature- is a measure of heat intensity or quantity ? while a BTU - is a measure of heat intensity or quantity?
Intensity quantity
Three states of matter are?
Solid Liquid and gas
Absolute zero ?
-460*
When circling water is chilled in a refrigeration machine, the sensible or latent heat of the water is changed ?
Sensible
Pressure exerted by the weight of liquid at rest is called ?
Hydrostatic pressure
The occupied zone in an air conditioned room extends from the floor upwards from the floor upwards a distance of ?
6’ ft
The velocity of air to which occupants of air conditioning space are exposed is called local velocity or residual velocity for human comfort this philosophy should be in the range of ?
35 - 75 ft./min.
Smudging of ceiling around a ceiling diffuser is probably caused by ?
Dirty secondary air
Air distribution system increases comfort of the occupants by controlling?
Humidity temperature air motion
Human beings can dissipate excess heat from their skin a current of air passing over the skin and removing more heat than the skin would normally dissipate is called a?
Draft or gross air
In a terminal reheat system temperature or volume or both, temperature and volume is/are automatically veried ?
Both temperature and volume
A group of rooms all supplied by air of the same temperature and having windows facing West can, as related to an air distribution system, be referred to as a?
Zone
2 methods of static pressure control located at the supply fan are?
VFD and inlet guide veins
Dry contacts
separate control voltage, alarms, pressure switch, building automation, cts
Wet contacts
In line (powered), line voltage thermostat
The relationship of total pressure in the duct to the static pressure and the velocity pressure is?
Sum of static and velocity pressure
On impact tube with open and facing into the airstream will sense?
Total pressure
A velocity pressure of 1” in wc is indictative of a duck velocity very close to?
4000 ft./min.
Given a rate of air flow of 2225 CFM in a. having a cross-section of 18” by 18”, the duck velocity should be?
3860 ft./min. V×AREA××CFM
The fractional resistance of a duck system is indicated by ?
Static pressure
The resistance to air flow presented by cooling coil is 0.30” in wc when 2000 CFM pass through the coil the resistance will become_______ “ wc if the air quantity is increased to 3000 cfm
0.45” wc
To determine on the job the direction in which a centrifugal fan is rotating you should look at the fan?
From the side on which the drive pulley and belt are located
A fan delivers 2000 CFM when rotating at the speed of 1000 rpm if the fan is increased to 1200 RPM the fan will handle ?
2400 CFM
You have a sheet of graph paper on which have been drawn a fan performance curve for the speed at which the fan is actually operating and a system curve from this information how can you determine the actual CFM and static pressure?
The point of intersection of the fan performance curve with a system curve indicates the actual CFM and static pressure
The fractional resistance of a duck requires point 0.25” wc static pressure to cause air to flow in the duct at a rate of 2500 CFM. For flow in the same duct to be increased to 3500 CFM the static pressure will have to be?
0.49” wc.
Sp2
You Have a blowthru type of airhandling unit, you are to determine the amount of sensible heat the cooling coil is removing from the air. Assuming you have already determined the air quantity in CFM you should then measure?
DB temperatures entering and leaving the coil
Manufacturers fan rating tables show values of air horse power or break horse power?
Break horsepower
If a centrifugal fan is rotating backwards?
Air will flow into the fan inlet and out of the fan discharge
A type of the tachometer that combines a revolution counter in a stopwatch in one instrument is called a?
Chronometric tachometer
A type of tachometer that uses light to obtain an indication of RPM is called a?
Is strobescope
3 effects of access belt tension are
- Early belt failure
- Excessive wear on shaft bearings
- Possible overload of a drive motor
Any slack and a fan belt will cause?
- Slippage
- Loss of power
- Excessive belt wear
Several V vaults of smaller Cross-sectional area are used instead of 1B belt of large Cross-sectional area to reduce the?
Size of the drive
A belt drive on a motor driven fan has a drive sheet of 3” pitched diameter on the motor the pulley on the fat and shaft has a pitched diameter of 5”. When the motor speed is 1720 RPM what is the fan speed it’s the fan speed? Hes a little one where’s a little 1 at hes a little basketball well you don’t just kick that 1 hillies look that little basketball the blue 1 no grab the blue 10K blue 10K use that 1 that whatever whatever whatever
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