Auto HVAC

1
Auto HVAC

• Frank Faulkenberg
• David Giles
• Jimmy Huser
• Eric Bussh
• John Snodgrass

2
Design Specifications

• One 8 cm circular entrance (yellow)
• Three 10cm x 10cm available paths (red)
• Two 4cm x 3 cm exits (blue)
• One 4cm x 4 cm exit (blue)
• Volumetric flow rate of 5.0 m3/s
• Air _at_ 25 degrees C

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Design Goals

• Minimize pressure losses
• Equalize flow rates through the three ducts or
  paths
• Minimize cost

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Design Path
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Theory

• Bernoullis modified equation
  1
• Losses are reduced by lower velocities
• Use largest cross sectional areas possible to
  reduce velocities

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Specification Requirements

• Smooth bend requires r/d 1
• With a clearance of 0.5cm the largest OD is
  8.28cm leading to an ID of 7.78 cm
• Using miter bends and fairings
• With a clearance of 0.5 cm the largest HID 9.0cm
• K 0.5 with ro/do .45 and r1/do .45 1

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Specification Requirements contd

• Design requires circle to square change with
  K.14 2
• Each Path has a couple with K.096 2

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Specification Requirements contd

• Vent foil, K.13
  2

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Assumptions

• Stagnation pressure source with three equal
  outputs
• Smooth wall for ABS plastic
• 1.66 x10-5 lt f lt 4.3 x 10-5 is smooth up to (Re lt
  106) 3
• Re 104
• Discharge to 1 atm
• 1/kg

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Designs
1.000046 atm stag.
1 atm stat.

• Two Basic Designs

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Designs Contd

• Smooth elbows, 7.78cm ID
• Higher speed
• Lower elbow K values
• Miter elbows with fairings, 9.0cm ID
• Lower speed
• Higher K values

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Designs Contd

• Miter Bends , 9.0cm ID
• Smooth Bends, 7.78cm ID

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Design Conclusion

• Using Pro-Engineer, ABS density of plastic
  1.25g/cm3 4
• Smooth bends, 7.78cm ID
• Mass of 2.99 Kg
• Cost of materials 2.99
• Miter bends, 9.0cm ID
• Mass of 2.71 Kg
• Cost of materials 2.71

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References

• Local Losses, Toksoy
• Handbook of Hydraulic Resistance. Idelchek
• www.matweb.com
• www.engineeringtoolbox.com