Objectives Finish with ducts and fans Define project

Objectives • Finish with ducts and fans • Define project topics

Two types of Duct design procedure • Equal friction - Covered in classes and book - keeps same pressure per unit of length P/L • Static regain - keeps the same static pressure at each branch

Two types of duct design problems • You design a duct and then select the fan • You have the AHU with the fan and you need to design a duct that will fit in

Fan Performance

Centrifugal fans

Axial Fans

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

Question • How does fan power consumption vary with volumetric air flow rate?

Controlling Air Flow

Dampers

Effect on Fan Curve

VAV Operation

Summary of Air Distribution Systems • Select diffuser based on ADPI • Given a layout of duct system • Calculate total pressure drop • Identify fittings contributing most to pressure drop • Deal with non-circular ducts • Use fitting loss coefficient or equal length method • Select the fan based on fan and duct curve

VAV Systems

DOAS configurations

Project topics (groups of 3) 1) VAV system design • • Fresh air requirements and recirculation rate calculation Selection of zonal and central HVAC components based on cooling and heating load components • • For zones: VAV boxes, reheater plumbing For whole system: AHU and components, chiller & cooling tower, boiler, and electric power requirement Control description – sequence of operation Heat recovery system and or economizers 2) DOAS system design • • Fresh air requirement and split between air and hydronic loads (sensible and latent cooling loads) Selection of zonal and central HVAC components based on cooling and heating load components • • For zones: fan coils and plumbing For whole system: AHU and components, chiller & cooling tower, boiler, and electric power requirement Control description – sequence of operation Heat recovery system and or economizers

Project topics 3) Duct Design (in Revit and Manually) • - Diffuser selection, design of local and central duct system components • - Spacing issues and difference between round and square ducts • - Difference between manual calculation and calculation by Revit (for a section of the duct system) • - Balancing and fan selection • - Life cycle analysis and optimization (fan power consumption vs. system cost)

Some graduate student project topics (group of 2) 1) Cooling systems and distribution • Air cooled condenser vs. water cooled condenser (energy performance analysis) • Design of plumbing systems for campus and pumping stations • Control of centralized system • … 2) Design of air-conditioned storage space • Specific load • Dehumidification is the major task • …. 3) Heat recovery systems • …. . 4) Your topic

Cooling and Heating Loads (For Project) » Fresh air requirement based on number of occupants:

Cooling Load Calculation • Mostly computer based • Handouts for manual calculation • http: //www. ce. utexas. edu/prof/Novoselac/classes/ARE 346 N/Handouts/heatloss_table_2008. doc • http: //www. ce. utexas. edu/prof/Novoselac/classes/ARE 346 N/Handouts/ASHRAE_%20 Gains_Calculation_Tables. doc