HW4

1
HW4

• Problem 18.13
• (Use TITUS Square Ceiling MCD diffuser
• https//www.titus-hvac.com/Products/Diffusers)
• Problem 18.16
• (The building size is 100 ft x 60 ft use
  proportion to determine room sizes)
• Problem 18.19
• Problem 18.20
• Problem 18.27 (design problem)

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Objectives

• Finish with Duct Design
• Learn about Fans

3
Example
Size the ducts and calculate pressure drop from
- A to C - B to C
A
a
C
c
b
B
Tabulated calculation ..
4
Local Dynamic losses

• Losses associated with
• Changes in velocity
• Obstructions
• Bends
• Fittings and transitions
• Two methods
• Equivalent length and loss coefficients

5
Conversion Between Methods
6
Duct design concepts

• Equal friction method
• Static pressure regain method

7
Equal friction method(the example)
8
Static pressure regain method
9
Fans

• Driving force to move air in buildings
• Raise pressure and produce flow
• Two main types
• Centrifugal
• Axial

10
Relevant Fan Parameters

• Total pressure rise
• Static pressure rise
• Power requirement
• Efficiency
• Note ?tot does not account for motor efficiency

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Balance Point
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Fan Performance
13
Centrifugal fans
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Axial Fans
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Fan Laws

• Approximate relationships
• Given two aerodynamically similar fans, can
  extrapolate performance data
• Be very careful