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Auto HVAC. Frank Faulkenberg David Giles Jimmy Huser Eric Bussh John Snodgrass. 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 m 3 /s
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Auto HVAC Frank Faulkenberg David Giles Jimmy Huser Eric Bussh John Snodgrass
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 @ 25 degrees C
Minimize pressure losses Equalize flow rates through the three ducts or paths Minimize cost Design Goals
Theory Bernoulli’s modified equation [1] Losses are reduced by lower velocities Use largest cross sectional areas possible to reduce velocities
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 = .45and r1/do = .45 [1]
Specification Requirements cont’d • Design requires circle to square change with K=.14 [2] • Each Path has a couple with K=.096 [2]
Specification Requirements cont’d • Vent foil, K=.13 [2]
Assumptions • Stagnation pressure source with three equal outputs • Smooth wall for ABS plastic • 1.66 x10-5 < f < 4.3 x 10-5 is smooth up to (Re < 106) [3] • Re ~ 104 • Discharge to 1 atm • $1/kg
Designs 1.000046atm stag. Two Basic Designs 1 atm stat.
Designs Cont’d • Smooth elbows, 7.78cm ID • Higher speed • Lower elbow K values • Miter elbows with fairings, 9.0cm ID • Lower speed • Higher K values
Designs Cont’d • Miter Bends , 9.0cm ID • Smooth Bends, 7.78cm ID
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
References • Local Losses, Toksoy • Handbook of Hydraulic Resistance. Idelchek • www.matweb.com • www.engineeringtoolbox.com