Docsity
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Docsity AI
Docsity AI
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search for your university

Find the specific documents for your university's exams

Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

Room Distribution Basics, Diffusers, Supply and Return Duct Sizing | ARE 346N, Study notes of Architecture

The University of Texas at AustinArchitecture
Prof. Jeffrey A. Siegel

Material Type: Notes; Professor: Siegel; Class: BUILDING ENVIRONMENTAL SYSTEMS; Subject: Architectural Engineering; University: University of Texas - Austin; Term: Spring 2009;

Typology: Study notes

Pre 2010

Uploaded on 08/26/2009

koofers-user-npc
koofers-user-npc 🇺🇸

10 documents

1 / 13

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Objectives
• Describe room
distribution basics
• Select diffusers
• Supply and return
duct sizing
Designing Room Airflow
• Very complex problem
• Pumped flow, bouyant flow (or mixed flow)
• What non-dimensional parameters govern each
regime?
• Archimedes number = Ar = gβLΔT/V2
L = characteristic length (m, ft)
g = acceleration due to gravity (m/s2, ft/min2)
T = absolute temperature (K, °R)
β = 1/T (1/K, 1/ °R)
V = air velocity (m/s, ft/min)
pf3
pf4
pf5
pf8
pf9
pfa
pfd

Partial preview of the text

Download Room Distribution Basics, Diffusers, Supply and Return Duct Sizing | ARE 346N and more Study notes Architecture in PDF only on Docsity!

Objectives

  • Describe room distribution basics
  • Select diffusers
  • Supply and return duct sizing

Designing Room Airflow

  • Very complex problem
  • Pumped flow, bouyant flow (or mixed flow)
  • What non-dimensional parameters govern each regime?
  • Archimedes number = Ar = gβLΔT / V^2 L = characteristic length (m, ft) g = acceleration due to gravity (m/s^2 , ft/min^2 ) T = absolute temperature (K, °R) β = 1/T (1/K, 1/ °R) V = air velocity (m/s, ft/min)

Colorful Fluid Dynamics

Diffuser Selection Procedure

  • Select and locate diffusers, divide airflow amongst diffusers V = maximum volumetric flow rate (m^3 /s, ft^3 /min) Qtot = total design load (W, BTU/hr) Qsen = sensible design load (W, BTU/hr) ρ = air density (kg/m^3 , lbm/ft^3 ) Δt = temperature difference between supply and return air (°C, °F) Δh = enthalpy difference between supply and return air (J/kg, BTU/lbm)

Find Characteristic Length

Diversion

  • ADPI = air distribution performance index
  • Fraction of locations that meet criteria:
    • -3 °F < EDT < 2 °F
    • Where, EDT = effective draft temperature
      • Function of V and Δt (Eqn 18.1)

Ideal and Reasonable Throws

Pressures

  • Static pressure – pressure not due to velocity
  • Velocity pressure – pressure due to velocity
  • Total pressure – sum of above Relationship Between Static and Total Pressure
  • Total and static pressure drops are proportional to square of velocity
  • Plot of pressure drop vs. volumetric flow rate (or velocity) is called system characteristic

Duct Design

System Characteristic

Non-circular Ducts

  • Parallel concept to wetted perimeter

Dynamic losses

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

Loss Coefficients

ΔPt = CoPv,

Summary

  • 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
  • Next class: fans, duct layout, other equipment