Forward curved fans

Forward curved fans

a) require larger size shafts than backward inclined fans
b) are desirable when air handling units have two or more fans mounted on a common shaft
c) operate at higher speeds than backward inclined fans
d) are quieter than backward inclined fans
e) are more desirable for large fans






Answer: B

Control of the static pressure and horsepower requirements at a given speed is obtained by using

Control of the static pressure and horsepower requirements at a given speed is obtained by using

a) direct drives
b) fluid drives
c) outlet damper control
d) variable inlet vane control
e) belt guards







Answer: D

Centrifugal fans are classified as

Centrifugal fans are classified as

a) backward inclined
b) straight
c) backward inclined with airfoil blades
d) forward curved
e) all of the above







Answer: E

When comparing the tube axial fan with the vane axial fan the main difference between the two is the

When comparing the tube axial fan with the vane axial fan the main difference between the two is the

a) noise output
b) location of the fans in the system
c) location of the fan bearings
d) size of the two units
e) motion of the discharge air






Answer: E

The group of fans which consist of a rotor or wheel having several radial blades, which is mounted on a shaft within the fan housings is

The group of fans which consist of a rotor or wheel having several radial blades, which is mounted on a shaft within the fan housings is

a) Axial flow
b) Centrifugal
c) Both Axial flow and Centrifugal
d) Archial flow
e) None of the above







Answer: B

Backward inclined centrifugal fans:

Backward inclined centrifugal fans:

a. Require more horsepower than the forward curved fans to deliver a specified volume of air
b. Are quieter than forward curved fans
c. Are less efficient than forward curved fans
d. Operate at lower speeds than forward curved fans
e. Are noisier than forward curved fans






Answer: B

Two fan wheels are rotating at the same speed. One wheel has forward curved blades and the other has backward inclined blades. The velocity of the air leaving the forward curved blades is considerably higher, because

Two fan wheels are rotating at the same speed. One wheel has forward curved blades and the other has backward inclined blades. The velocity of the air leaving the forward curved blades is considerably higher, because

a. The centrifugal force of the forward curved blades is higher.
b. The linear velocity of the forward curved blades is higher.
c. The air resistance of the backward inclined blades is much lower.
d. The velocity of the air leaving the fan blades, added to the linear velocity of the fan blades, is greater with the forward-inclined fan blades than backward-inclined fan blades.
e. Fans with forward curved blades must be constructed with larger diameter wheels to provide the same airflow as a fan with backward-inclined blades.

Answer: D

Which of the following statements about fan performance curves is false?

Which of the following statements about fan performance curves is false?

a. They are plotted from theoretical calculations
b. The curve is a plot of static pressure against air volume delivery
c. The curve is a plot of horse, power against air volume delivery
d. The curve is a plot of static efficiency against air volume delivery
e. The curve range is from shutoff to free delivery







Answer: A

The two general groups of fans are:

The two general groups of fans are:

a. Positive displacement and dynamic
b. High pressure and low pressure
c. High volume and low volume
d. Positive displacement and axial flow
e. Centrifugal and axial flow







Answer: E

When a fan outlet is fully open,

When a fan outlet is fully open, 

a. The horsepower requirements for vane axial fans are at their maximum
b. The pressure volume curve of a backward inclined fan increases
c. There is free air volume delivery
d. The power requirements of a forward curved fan are at their minimum
e. The fan discharge static pressure is at its maximum.







Answer: C

Axial flow fans are classified as:

Axial flow fans are classified as:

a. Centrifugal and propeller
b. Vane axial and centrifugal
c. Tube axial and rotary positive displacement
d. Vane axial, tube axial, and propeller
e. Centrifugal and turbine







Answer: D

The vane axial flow fan:

The vane axial flow fan:

a. Has a more spiral air flow than the tube axial fan
b. Has more turbulent air flow than the tube axial fan
c. Has lower efficiency than the tube axial fan
d. Has less spiral air flow, less friction, and better efficiency than the tube axial fan
e. Is not suitable for duct mounting







Answer: D

Backward inclined airfoil fans:

Backward inclined airfoil fans:

a. Are mostly used for low capacity, high pressure applications
b. Are mostly used for high capacity, low pressure applications
c. Are mostly used for high capacity, high pressure applications
d. Have a lower initial cost than the plain backward inclined fan
e. Are less efficient than the plain backward inclined fan







Answer: C

Axial flow fans:

Axial flow fans:

a. Have maximum horsepower requirements at maximum air delivery
b. Have minimum horsepower requirements at maximum air delivery
c. Are the logical choice to move large volumes of air at high static pressures
d. Are the least economical choice when large volumes of air must be moved at low pressures.
e. Are quieter than centrifugal fans







Answer: B

The tube axial flow fan:

The tube axial flow fan:

a. Has higher duct friction losses than centrifugal fans
b. Has lower friction losses in ducts than the centrifugal fan
c. Is quiet in operation
d. Produces lower pressure than the propeller fan
e. Is not suitable for duct mounting






Answer: A

The static pressure measured in an air duct is measured by connecting a:

The static pressure measured in an air duct is measured by connecting a:

a. Manometer to the side of an air duct
b. Bourdon tube to the air duct
c. Pressure gauge to the side of a duct, with a sensing tube extending inside of the duct directed toward the airflow
d. Manometer to the side of a duct, with a sensing tube extending inside of the duct directed toward the airflow
e. Manometer to the fan







Answer: A

To minimize fan vibration problems and premature fan belt wear, it is proper to use

To minimize fan vibration problems and premature fan belt wear, it is proper to use

a. Direct drive fans
b. Balanced Sheaves
c. V-Belt drives
d. Fluid drives
e. Outlet damper controls







Answer: B

Total pressure exerted by the air is the sum of:

Total pressure exerted by the air is the sum of:

a. Head pressure, suction pressure, and velocity pressure
b. Head pressure and suction pressure
c. Head pressure and velocity pressure
d. Static pressure and velocity pressure
e. Suction pressure and velocity pressure








Answer: D

Forward curved centrifugal fans:

Forward curved centrifugal fans:

a. Operate at a lower speed than backward inclined fans for the same air volume
b. Operate at a higher speed than backward inclined fans for the same air volume
c. Require less horsepower than backward inclined fans to deliver a specified air volume
d. Are more efficient than backward inclined fans
e. Are quieter than backward inclined fans






Answer: A

The propeller axial flow fan:

The propeller axial flow fan:

a. Produces low capacity, low pressure air movement
b. Finds application in unit heaters, air-cooled condensers, and as an exhaust fan for ventilation purposes
c. Is used in commercial air conditioning ducting
d. Requires the least power at minimum air delivery
e. Is used in ducted air distribution systems







Answer: B