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)

Objectives Finish with Duct Design Learn about Fans

Example A C B Size the ducts and calculate pressure drop from - A to C - B to C A a c C b B Tabulated calculation: ……..

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

Conversion Between Methods

Duct design concepts Equal friction method Static pressure regain method

Equal friction method (the example)

Static pressure regain method

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

Relevant Fan Parameters Total pressure rise Static pressure rise Power requirement Efficiency Note ηtot does not account for motor efficiency

Balance Point

Fan Performance

Centrifugal fans

Axial Fans

Fan Laws “Approximate relationships” Given two aerodynamically similar fans, can extrapolate performance data Be very careful