Mechanical Air Movement And Control Flashcards
What are two groups or classes of fans ?
Axial (propeller)
Centrifugal (radial)
What are three types of axial flow fans ?
Propeller
Tubeaxial
Vaneaxial
Can propeller fans handle larger volumes of air ?
Yes at low static pressure
Can you connect ductwork to a tube axial disc fan ? If yes explain
Yes but the air is discharged in a spiral motion producing high losses in the duct system
What is cubic feet per minute ?
Measure of volume of air moved by fan per minute
What are the two general groups of fans
Axial (propeller)
Centrifugal (radial)
What are four types of fan blades
Forward curved
Backward inclined
Airfoil
Radial
What type of fan has low noise emmison and are suitable for resturants exhaust or wgere air contains moisture or dust ?
Backward inclined
How is the location of the motor of discharged determined ?
By facing the drive side
What is the difference between a tube axial fan and a vane axial fan ?
Vaneaxial has a guide vanes behind the wheel to improve efficiency by straightening the flow of air
What is another name for a centrifugal fan ?
Squirrel cage
What are the uses and applications for a forward curved fan ?
Used for low pressure heating ventilating and air conditioning systems ranging from room air conditioners to residential furnaces
What are the uses and applications for a forward curved fan ?
Used for low pressure heating ventilating and air conditioning systems ranging from room air conditioners to residential furnaces
What are the uses and applications for a radial blade fan ?
For material handling high pressure industrial applications like saw dust
What does cwbhd stand for ?
Clock wise bottom horizontal
How is motor location determined ?
Facing drive side of the fan and designating the positions by letters w x y or z
How much straight duct is required to achieve 100% effective duct length for systems with an airflow of 2500fpm or less ?
2.5 duct diameters
What items would cause system resistance or pressure loss in an hvac system ?
Fittings coils dampers
List 5 peices of info that can be found on a fan performance chart ?
Horse power
Volume
Static pressure
Rpm
System curves
What damper is installed in branch fittings ?
Splitter dampers
When would air extractors be used ?
When there is not adequate room to mount a splitter damper
List 3 important functions of multi blade dampers ?
Control and mix outside air with return ,
Bypass heat transfer equitment ,control air qualities
Name two styles of multi blade dampers ?
Parellel or opposed blade
A 1000cfm of air is to be moved through a duct system with a total pressure of 0.4” wc which type of fan is best for this installations ?
Forward curved blade centrifugal fan
Propeller disc fans are designed to ?
Have no duct at all
The backward inclined airfoil fan is a refinement of the flat blades backward inclined centrifugal fan in what respect ?
It has better static efficiency
It is quieter
What type of fan blade arrangement is ussally used in air pollution control applications with high particulate loadings ?
Radial blades
Which fan should never be used in a ductless system ?
Forward curved blade centrifugal fan
In most cases what is the best fan to use on a blow pipe system for a sawmill ?
Radial bladed centrifugal fan
Most upflow residential heating equitment uses a centrifugal fan in what position configuration?
Ccwubd
The most accurate volume control of air is obtained by using a ?
Opposed blade damper
An accepted method of determining the length of a splitter damper is ?
1.5 times the width of the small duct
Which damper is generally used in locations where it is either fully open or fully closed ?
Pareellel blade damper
These fans provide right angle airflow in a rectangular shape and are useful in applications such as air curtains over doorways ?
Cross flow fans
Inlet box dampers supplied with parallel blades offer performance characteristics similar to inlet vane dampers
(True or false )
True
Parallel blade dampers are the best for modulating air flow ?
(True or false)
False
Either fully opened or fully closed
Forward curved fans are common in wheel diameters up to ??
24”
What type of fan has low noise emission and are suitable for restaurant exhaust systems or where air contains moisture or dust ?
Backward inclined blades