Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
58 Cards in this Set
- Front
- Back
|
Three ways in which heat can be transfered are ________, _________ and ________ .
|
convection, radiation and conduction.
|
|
|
The latent heat which changes liquid water into steam is called the latent heat of ________ .
|
latent heat of vaporization .
|
|
|
A Pitot tube test indicates a velocity pressure equal to one inch W.G., and based on standard air, the corresponding velocity is _______ ft./min.
|
4005 ft./min.
|
|
|
A u-tube manometer with one end opened to the atmosphere and the other end sealed and subjected to a perfect vacuum will measure the
A. atmospheric pressure. B. absolute pressure. C. gage pressure. |
A. atmospheric pressure.
|
|
|
|
|
|
A room is heated by circulating a supply of warm air, the air being introduced at a temperature of 95°F DB. If the room temperature is to be maintained at 75°F DB, 57°F WB, and under these conditions the room loses heat at the rate of 2,160 Btuh, how much supply in cfm's air is required? Answer ______ cfm .
|
|
|
|
Air flow through a cooling coil at the rate of 3,000 cfm, entering the coil at 80°F DB, 70°F WB, 34.0 Btu/lb total heat and leaving the coil at 56°F DB, 54°F WB, 22.7 Btu/lb total heat. The coil, therefore, removes sensible heat at the rate of ________ Btuh.
|
|
|
|
Absolute zero temperature is equal to ______°F & ______°C
|
|
|
|
|
|
|
A. incorrect and too low.
|
|
|
At normal atmospheric conditions at sea level, an absolute pressure of 14.7 psia is equal to a gage pressure of ______ psig.
|
0 psig
|
|
|
What size belt would be required if a belt driven fan had a 8" sheave ; 18" pulley, and a center to center measurement of 20"? ________
A. 40.22 B. 82.07 C. 80.84 D. 48.07 |
C. 80.84 Belt length
|
|
|
a fan operating at 762 rpm delivers 18,000 cfm against a 1.5" WC static pressure and draws 14.8 bhp. If the fan speed is increased to 1020 rpm; find the following:
cfm ______ Sp _______ Bhp ______ |
|
|
|
To measure relative humidity, you could use a
A. psychrometer. B. thermistor thermometer with flat probe. C. hydrant. D. thermocouple type electric thermometer. |
A. psychrometer.
|
|
|
Manufacturer's fan rating tables show values of air horsepower or brake horsepower.
A. brake horsepower B. air horsepower |
A. brake horsepower
|
|
|
The relative humidity of saturated air is _____ %
|
100 %
|
|
|
True or False,
A forward curve fan is non overloading. |
False
|
|
|
Pressure in air ducts are usually measured in units,
A. in. w.g. B. in. Hg. C. psi. D. mm. Hg. |
A. in. w.g.
|
|
|
A 28' column of water exerts ______ at its base.
|
Answer: 12.1 psi.
1 foot of water = 0.433 psi. .433 X 28 = 12.12 |
|
|
To measure a change in the total heat of air, you would measure ______ - bulb temperatures.
|
wet-bulb temperatures
|
|
|
Several common forms of energy are heat, chemical, electrical and mechanical. Write the appropriate form of energy in the blank space.
A. Oil burned in a boiler converts its ______ energy to ______ energy. B. An electric motor converts _______ energy to ______ and ______ forms of energy. |
A. Chemical energy to heat energy.
B. electrical energy to mechanical and heat forms of energy. |
|
|
Static pressure is equal to,
A. total pressure minus velosity pressure. B. total pressure less atmospheric pressure. C. total pressure plus velocity pressure. D. pressure as sensed by an impact tube. |
A. total pressure minus velosity pressure.
|
|
|
To measure a change in the sensible heat of air, you would measure _______ - bulb temperatures.
|
Dry-bulb temperatures.
|
|
|
You might get a incorrect reading of a glass-stem thermometer because of
A. radiation. B. liquid seperation. C. any of the above. D. parallax. |
C. any of the above.
|
|
|
Although B and 5L V belts have the same cross sectional dimensions they should not be interchanged because of their difference in __________.
A. size B. flexibility C. rotational direction D. circumference |
B. flexibility
|
|
|
A perfect vacuum would give a gage pressure of _______ in. Hg.
|
29.92 in. Hg.
|
|
|
The folllowing temperature readings have been obtained:
Dry-Bulb temperature = 95°F Wet-Bulb temperature = 80°F Dew Point temperature = 75°F Based on these temperatures, the Wet-Bulb depression is _______ °F. |
15°F
|
|
|
If a pitot tube is not faced squarely into the air stream
A. the reading will be incorrect only if the tip of the pitot tube has been bent or mashed. B. the pressure reading obtained will be less than the true pressure. C. errors in static pressure will cancel out so that the indicated pressure will still be correct. D. a falsely high reading will be obtained. |
B. the pressure reading obtained will be less than the true pressure.
|
|
|
(Reference Psychrometric Chart) Temperature readings show 90°F DB, 75°F WB, whch indicate that the relative humidity is ______ %.
|
50% humidity
|
|
|
(Reference Psychrometric Chart) Air is dehumidified from a DP temperature of 70°F to a DP temperature of 55°F. The moisture removed is equal to ______ grains of moisture per lb of dry air.
|
45 grains
|
|
|
Fan performance ratings are given in cfm or lb/min. of air and static or total pressure.
A. cfm, total B. cfm, static C. lb/min of air, static D. lb/min of air, total |
B. cfm, static
|
|
|
Possible ways recommended to eliminate liquid seperation in a glass-stem thermomter are:
A. Heat the thermometer bulb. B. Make the thermometer bulb very cold. C. Tap the Thermometer bulb gently against an solid object. D. Both A & B. |
D. Both A & B.
|
|
|
In using a dial thermometer of the rigid type, you might get an incorrect reading because of
A. incorrect length of stem immersion. B. any of the above. C. liquid seporation. D. incorrect dial calibration. |
D. incorrect dial calibration.
|
|
|
The frictional resistance of a duct system is indicated by
A. total pressure. B. velocity pressure. C. static pressure. |
C. static pressure.
|
|
|
A centrifugal fan has both an inlet duct and a discharge duct, and you want to measure the static pressure of the fan using a U-tube manometer. you should use
A. a static pressure tube in both inlet and discharge ducts. B. an impact tube in both inlet and discharge ducts. C. a static pressure tube in the discharge and a impact tube in the inlet duct. D. a static tube in the inlet and discharge duct. |
C. a static pressure tube in the discharge and a impact tube in the inlet duct.
|
|
|
The resistance to airflow presented by a cooling coil is 0.28" wc when 2200cfm passes through it. The resistance will become _____ "wc if the air quantity is increased to 3300cfm.
A. .63 B. .32 C. .44 D. 1.0 |
A. .63" wc
|
|
|
A rating vane aneometer must be used with a ________ instrument to determine velocity.
A. temperature B. pressure C. timing D. humidity |
C. timing
|
|
|
Of the various types of thermometers, the simplest and most reliable type, and not requiring any calibration is the
A. thermocouple type. B. liquid-in-glass type. C. electric resistance type. D. dial type. |
B. liquid-in-glass type.
|
|
|
When setting up a U-tube manometer to use in measuring a duct pressure, and while both legs of the monometer are open to the atmosphere, it is found that the level of the liquid in both legs is slightly below the zero of the manometer scale. In order to get a proper reading,
A. you may proceed without adjustment if you read the scale indication of both lquid levels. B. enough liquid must be added to bring the level to zero or any reading will be in error. C. all of the above are necessary. D. the scale must be set to a zero indication or you will be unable to read the pressure. |
A. you may proceed without adjustment if you read the scale indication of both lquid levels.
|
|
|
Tests of an air conditioning system made while the refrigeration sub-system was operating at full capacity show the supply fan motor to be drawing exactly rated current of 25.4 amperes. If the refrigeration system is turned off, the motor will.
A. draw current less than 25.4 amperes. B. draw more than 25.4 amperes. C. none of the above. D. draw the same current, 25.4 amperes. |
B. draw more than 25.4 amperes.
|
|
|
You have a fan performance curve for the speed at which a fan is actually operating. You have plotted a system curve using measurements previously taken when the fan was operating at a different speed than it is now. From this information, how can you determine the current cfm and static pressure?
|
When plotted in the same sheet with the fan performance curve, the intersection of the two curves indicates the systems operating point.
|
|
|
An air distribution system accomplishes heat transfer by
A. radiation. B. conduction. C. convection. D. all of the above. |
C. convection.
|
|
|
A fan delivers 2,000 cfm when rotating at a speed of 1,000 rpm. If the fan speed is increased to 1,200 rpm, the fan will handle ______ cfm.
A. 1,600 B. 2,400 C. 2,200 D. 3,200 |
B. 2,400 cfm
|
|
|
If you wanted to measure a temperature of -50°F, you could use which of the following types of thermometers:
A. glass-stem mercury thermometer. B. pyrometer. C. hygrometer. D. thermistor type electrical instrument. |
D. thermistor type electrical instrument.
|
|
|
A U-tube manometer with one end connected to a source of pressure and the other end opened to the atmosphere will measure the
A. absolute pressure. B. gage pressure C. net pressure. D. atmospheric pressure. |
B. gage pressure
|
|
|
As related to air conditioning problems, another name for total heat is ____ .
|
enthalpy
|
|
|
Any slack in a fan belt will cause
A. loss of power. B. slippage. C. excessive belt wear. D. all of the above. |
D. all of the above.
|
|
|
Static pressure sensing elements
A. should face directly downstream. B. may be placed at any angle to the air stream if the holes are carefully made and are free of burrs. C. should be placed so their holes are at right angles to the direction of the air flow. D. should face directly up stream. |
C. should be placed so their holes are at right angles to the direction of the air flow.
|
|
|
Friction loses in elbows vary
A. as the square of velocity pressure. B. with static pressure. C. directly with the velocity. D. as the square of the velocity. |
D. as the square of the velocity.
|
|
|
Temperature is a measure of heat intensity or quantity while a Btu is a measure of heat intensity or quantity.
A. quantity, quantity B. intensity, quantity C. intensity, intensity D. quantity, intensity |
B. intensity, quantity
|
|
|
A belt drive on a motor driven fan has a drive sheave of three-inche pitch diameter on the motor.
the pulley on the fan shaft has a pitch diameter of five inches. When the motor speeds is 1,720 rpm, what is the fan speed? _____ rpm. A. 1032 B. 1820 C. 1023 D. 1281 |
A. 1032 rpm
|
|
|
Three states of matter are ________, ________ and ________.
|
Liquid, Solid and Vapor.
|
|
|
What is the term for a substance that changes state from a solid to a vapor without becoming a liquid?
|
Sublimation
|
|
|
When circulating water is chilled in a refrigeration machine, the sensible or latent heat of the water is changed.
A. sensible B. latent |
A. sensible
|
|
|
Several V belts of smaller cross sectional area used instead of one V belt of large cross sectional area to reduce the ___________ of the drive.
A. noise B. diameter C. temperature D. size |
D. size
|
|
|
A manometer contains oil having a specific gravity of 0.80. When a pressure being measured with the manometer is equal to one in. w.g. the actual distance between liquid levels on the manometer scale will be _______ ".
A. 1.00" B. 0.80" C. 0.125" D. 1.25" |
D. 1.25"
1.0" w.g. Divided by 0.8 s.g.=1.25 |
|
|
Name three effects of excessive belt tension are:
|
1. Early belt failure.
2. Excessive wear on shaft bearings. 3. Overload of drive motor. |
|
|
A 1765 rpm motor with a 6.4"ø sheave is turning an air handler fan at 806 rpm. What is the fan pulley size?
A. 14.75" B. 13.75" C. 12" D. 14" |
D. 14"
|
