Objectives
This presentation is the property of its rightful owner.
Sponsored Links
1 / 30

Objectives PowerPoint PPT Presentation


  • 51 Views
  • Uploaded on
  • Presentation posted in: General

Objectives. Finish with Duct Design Review the design procedure and explain the theoretical background Diffuser Selection. Frictional Losses. Dynamic losses. Losses associated with Changes in velocity Obstructions Bends Fittings and transitions. Air Distribution System Design.

Download Presentation

Objectives

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Objectives

  • Finish with Duct Design

    • Review the design procedure and explain the theoretical background

  • Diffuser Selection


Frictional Losses


Dynamic losses

  • Losses associated with

    • Changes in velocity

    • Obstructions

    • Bends

    • Fittings and transitions


Air Distribution System Design

  • Describe room distribution basics

  • Select diffusers

  • Supply and return duct sizing


Forced driven air flowDiffusers

  • Grill (side wall)

  • diffusers

  • Linear diffusers

  • Vertical

  • Horizontal one side


Diffusers types

  • Valve diffuser

  • swirl diffusers

  • ceiling diffuser

  • wall or ceiling

  • floor


Diffusers

  • Perforated ceiling diffuser

  • Jet nozzle diffuser

  • Round conical ceiling diffuser

  • Square conical ceiling diffuser

  • Wall diffuser unit

  • Swirl diffuser

  • Floor diffuser

  • Auditorium diffuser

  • Linear slot diffuser

  • DV diffuser

  • External louvre

  • Smoke damper

  • http://www.titus-hvac.com/techzone/

  • http://www.halton.com/halton/cms.nsf/www/diffusers


Low mixing Diffusers Displacement ventilation


V = maximum volumetric flow rate (m3/s, ft3/min)

Qtot = total design load (W, BTU/hr)

Qsen = sensible design load (W,BTU/hr)

ρ = air density (kg/m3, lbm/ft3)

Δt = temperature difference between supply and return air (°C, °F)

Δh = enthalpy difference between supply and return air (J/kg, BTU/lbm)

Diffuser Selection Procedure

  • Select and locate diffusers, divide airflow amongst diffusers


Find Characteristic Length (L)


Indicator of Air DistributionQuality

  • ADPI = air distribution performance index

  • Fraction of locations that meet criteria:

    • -3 °F < EDT < 2 °F or -1.5 °C < EDT < 1 °C

    • Where, EDT = effective draft temperature

      • Function of V and Δt (Eqn 18.1)

      • EDT=(tlocal-taverage)-M(Vlocal-Vaverage) , M=7 °C/(m/s)

        ADPI considers ONLY thermal comfort (not IAQ)


Ideal and Reasonable Throws


Diffuser testing


ADPI


Select Register

  • Pick throw, volumetric flow from register catalog

  • Check noise, pressure drop

http://www.titus-hvac.com/ecatalog/subcategory.aspx?refid=186

http://www.nailor.com/

http://www.price-hvac.com/


Summary of Diffuser Design Procedure

  • Find Q sensible total for the space

  • Select type and number of diffusers

  • Find V for each diffuser

  • Find characteristic length

  • Select the diffuser from the manufacturer data


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


  • Login