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Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion design

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Page 1: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Improved Thermal Comfort

& Energy Efficiency with

low-pressure VAV diffusion

design

Page 2: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Technical Paper

“A guide to the design of an effective low pressure

VAV air distribution system”

By Noel de Villiers Pr. Eng. BSc. Eng (Mech)

Page 3: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Traditional Building

AC AHU \ FCU matched with a High

Pressure Air Distribution System

Excessive fan power

Potential noise issues

Common in many buildings

VAV Box design used

Energy

Efficiency

Meter

Page 4: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Current Building Trend

EC AHU \ FCU mis-matched with a High

Pressure Air Distribution System

EC Technology is used to be more energy efficient

Not a matched solution

Moderate improvements

VAV Box design used

Energy

Efficiency

Meter

Page 5: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Future Buildings

EC AHU \ FCU matched with an energy

efficient Low Pressure Air Distribution System

Matched solution for optimal energy efficiency

Significantly lower fan power required

Up to 68% on a well designed system

Capable of precise air delivery to every room

VAV Diffuser design used

Energy

Efficiency

Meter

Page 6: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

High Pressure System

Advantages

High pressures and

velocities allow the duct

size to be reduced

Cost effective when a large

number of outlets are used

Disadvantages

Excessive fan power

required

Higher noise levels can

require attenuation

Lack of flexibility

Risk of cold air dumping &

hot air stratification

Costly for individual room

comfort applications

Pressure Independent System

Page 7: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Low Pressure System

Advantages

Lower fan pressure =

reduced energy consumption

Lower noise levels

Flexibility greatly improved

Variable and constant grille

on the same duct

No risk of cold air dumping

or hot air stratification

Cost effective for individual

room comfort applications

Disadvantages

Duct sizes need to be

larger to allow lower

velocities

Attention to duct design

and pressures needed

during design

Pressure Dependent System

Page 8: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

So what is a VAV Diffuser?

Variable Geometry

Coanda Mixing

Effect

Page 9: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

VAV Diffuser Benefits

Individual Thermal Comfort

Energy Efficiency

Flexibility – easy to change zones

Ease of Commissioning

Confirmation of Airflow

Building Tuning Simplified

Simpler Complaint Resolution

Fewer BMS points (on board controls & sensors)

Simulator

Page 10: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Good Duct Design Principles

• Three main diffuser take-off problem areas:

T-Junction

Flex length

Flex Bend at neck of the diffuser

Page 11: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Managing T-junction losses

12 17 5 Pa Difference

Page 12: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Managing T-junction losses

0 Pa Difference6 6

Page 13: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Managing Flex losses

10 PaDifference

1 11

Maximum Length Recommended at 1.5m

Page 14: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Managing Flex Bend losses

3 Pa Difference0 3

Use the bracket to ensure

a smooth 90° elbow

Page 15: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Traditional VAV Box Design

FILTERCOIL

AHU

T

MULTIPLE FIXED APERTURE DIFFUSER OUTLETS

THERMOSTAT

120Pa

VAV BOX VAV BOX

RETURN

AIR

FAN WITH VARIABLE

FREQUENCY DRIVE

S

T

THERMOSTAT

Page 16: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Traditional VAV Box Design

Volume control upstream of diffusers

Air diffusion works well at 100% flow rate

After flow reduction upstream

Increased Dumping of Cold air

Increased Stratification of Hot air

Reduced Induction – reduced air change effectiveness

System Flexibility Compromised

Individual diffuser control costly

“Dumping takes place

at reduced volumes”

B A

Page 17: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Low Pressure VAV Diffusion Design

“Due to variable geometry dumping does

not take place at reduced volumes”

Page 18: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Simple VAV Diffuser Duct Design

VAV Diffusers will function well with duct pressures at -10% to +20% design levels

Pressure sensors needs need to be placed 2/3 down the length of the duct

Design ducting with a relative even pressure profile

Page 19: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Advanced VAV Diffuser Duct Design

Page 20: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Intermission Trivia

Page 21: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Designing with Equal Friction

Most common method of duct design

This method has duct sized for a constant static

pressure loss due to friction per unit length

This method can be used with VAV Diffusion if;

The starting velocity is less than 5 m/s in the duct

The duct run is short enough so that the pressure drop from

beginning to end fails within -10% to +20% range that the

VAV Diffusers can accommodate

Good duct principles are used, ie short Flex

Page 22: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Designing with Equal Friction

Typically used where short duct runs are required

This method yields;

Excellent individual thermal comfort

Excellent levels of room control

Improved energy efficiency saving v’s traditional high

pressure VAV Box

Page 23: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Designing with Static Regain

This method has duct sized to obtain the same

pressure throughout the duct run

Using static regain method of duct design, the

increase in static pressure at each branch offsets

the friction loss in the succeeding section of the duct

The static pressure should then be the same before

each VAV Diffuser and at each branch

The design does not need to be perfect, remember

the diffusers can manage -10% to +20% pressure

drop

Page 24: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Designing with Static Regain

Due to lower design velocities, the duct dimensions

are typically slightly larger than when using the

Equal Friction duct design method

The increase in duct cost is offset by;

Lower operating cost

Less ducting since more than one zone can be on the

same duct run

Savings in system balancing time

Page 25: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Designing with Static Regain

Typically used with long duct runs and\or when

optimal energy efficiency is required

This method yields;

Excellent individual thermal comfort

Excellent levels of room control

Maximum energy efficiency saving

Page 26: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

VAV Box Duct Design Example

Equal Friction Design

More ducting required

More branches required

Less comfort control

No flexibility

Page 27: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

VAV Diffuser Duct Design Example

Static Regain Design

Less ducting required

Simpler ducting design

Large ducting at start

More individual comfort

control

Excellent flexibility

Port Side

Example

Page 28: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Product Walk Through

Diffusers

Ceiling, Linear, Wall

Page 29: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Product Walk Through

Master Room Controllers

Wall Thermostats

On Board

Page 30: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Product Walk Through

Power Module

15 Diffusers to one

PSU

1 to 15 Master

Diffusers

Can be Standalone

Page 31: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Product Walk Through

BMS Connectivity

60 Diffusers to

one access point

(IP Address)

BACnet IP

BACnet ms\tp

LonWorks

Page 32: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Product Walk Through

Cables

All supplied

Plug and Play connection

Page 33: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Product Walk Through

Air Flow Sensors

Measures neck pressure and calculates airflow

Electronic commissioning

Precise air flow control to every diffuser

No air flow hood measurements required

Easy building tuning for the life of the building

Page 34: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Product Walk Through

Light Switching

Occupancy sensing

Switch Diffuser and \ or Lighting off

Saves HVAC energy & Lighting bills

Page 35: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Product Walk Through

Commissioning Tool

MLM Tool8 Application

Page 36: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Office Building

Aldi Head Office - Sydney

42 Electronic Linear Wall Diffusers

Meeting and Office Rooms

VLN15001/2 and Airflow sensors

CLN15004/2

BACnet IP BMS Integration

Page 37: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

University Building

Queensland University of Technology

107 Electronic VAV Wall Diffusers

Wall Thermostats with Occupancy Sensors

Green Star Building

BACnet TCP\IP BMS Integration

Page 38: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Shopping Centre

Grand Plaza – Stage 2 Queensland

Large Shopping Centre, Multiple small shops

94 Electronic VAV Square Diffusers

BACnet MS\TP BMS Integration

Page 39: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Country Hospital

Echuca, Victoria

400 Electronic VAV Square Diffusers

182 Wall Thermostats

Variable AHU, static regain, ERV, 100% fresh Air,

no attenuation required

Designed around the Rickard Diffusers

Presented at NEBB conference

BACnet IP BMS Integration

Won 2014 AIRAH Innovation Award!

Page 40: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Major Hospital

Sunshine Coast University Hospital, QLD

4,000 Electronic VAV Circular Diffusers

Airflow Sensors on all Diffusers

BACnet IP BMS Integration

Advanced simple electronic commissioning

- No air flow hood measurements required

Page 41: Improved Thermal Comfort & Energy Efficiency with … · Improved Thermal Comfort & Energy Efficiency with low-pressure VAV diffusion ... Designing with Equal Friction Most common

Take Home Points

EC AHU \ FCU matched with an energy efficient low

pressure air distribution system provides optimum

energy efficiency

Improved individual room comfort & control

Simplified Building tuning that can be conducted

remotely

Flexibility for tenant fitouts changes

Precise air flow delivery