GBI Decoupled Ventilation Systems - mgbc.org.my€¦ · Modulating Valve By-pass Damper F.A Filter...

25/9/14

Prof Chandra Sekhar, National University of Singapore, ASHRAE DL, Oct 2014 1

Professor Chandra Sekhar PhD, Fellow ASHRAE, Fellow ISIAQ

Department of Building, School of Design and Environment

ASHRAE Distinguished Lecturer Talk

GBI PROFESSIONAL SERIES ON IEQ 2014 Kuala Lumpur

10 October 2014

Dedicated Outdoor Air

Systems or

Decoupled Ventilation Systems

Outdoor Air

DEMAND VENTILATION

Recirculated Air

DEMAND COOLING

IAQ - Exposure Control

Professor Chandra Sekhar

25/9/14


Dedicated Outdoor Air System (DOAS)


DOAS1

CHWS=6-‐7 °C

CHWS=20 °C

Outdoor Air (O/A) condiDon: •  Full dehumidifica?on by DOAS to required Dew Point Temperature

•  Insulated duct

O/A O/A O/A

O/A O/A O/A

O/A O/A O/A

O/A O/A O/A

O/A O/A O/A

O/A O/A O/A

O/A O/A O/A

O/A O/A O/A

Outdoor Air

Two Chillers are needed due to different CHWS temp requirements

What is Dedicated Outdoor Air System (DOAS)?

DOAS with Chilled Ceiling

Chilled Ceiling Panels Decoupling Ven-la-on From Cooling

DEMAND VENTILATION & DEMAND COOLING at the Independent zone level Achieved in the case of DOAS with Chilled Ceiling

DOAS2 OR

DOAS1 – Chilled water coil AHU

DOAS2 – Desiccant Dehumidifica?on System


25/9/14


DEMAND VENTILATION & DEMAND COOLING at the Independent zone level NOT ACHIEVED in the case of DOAS with Secondary AHU

DOAS

CHWS=6-‐7 °C

CHWS=7-‐9 °C

Outdoor Air (O/A) condiDon: •  Par?ally dehumidified by DOAS – addi?onal dehumidifica?on done by secondary AHU OR

•  Full dehumidifica?on by DOAS to required Dew Point Temperature

•  Insulated Duct

S/A S/A S/A Secondary AHU

Outdoor Air

One Chiller can provide the required CHWS Temp for DOAS as well as Secondary AHU (For eg: Sequen?al feed)

What is Dedicated Outdoor Air System (DOAS)?

DOAS with Secondary AHU

Decoupling Ven-la-on From Cooling


Single Coil Twin Fan (SCTF) Air-conditioning & Air distribution system

Sekhar, S.C., Uma Maheswaran, C.R., Tham, K.W, and Cheong K.W, 2004. Development of energy efficient single coil twin fan air-conditioning system with zonal ventilation control, ASHRAE Transactions, 2004, Vol. 110, Pt 2, pp 204-217 (Paper presented in Nashville, June 2004).

Cheyyar, R U M, S C Sekhar, K W Tham and K W Cheong, "Single coil twin fan air-conditioning and air distribution system - Towards the development of a mathematical model of the compartmented coil". HVAC&R RESEARCH - International Journal of Heating, Ventilating, Air-conditioning and Refrigerating Research, 12, no. 3c, pp 825-842 (Special Issue) (October 2006).


25/9/14


Fan

CHWS=6-‐8 °C

UncondiDoned Outdoor Air (O/A) •  Uninsulated duct if O/A from roof-‐top

•  Alterna?vely, O/A can be drawn at each level

S/A S/A S/A SCTF AHU with Compartmented Coil

Outdoor Air

One Chiller can provide the required CHWS Temp for the SCTF System

Outdoor Air – Zone level Demand Ven?la?on

Recirculated Air – Zone level Demand Cooling

Single Coil Twin Fan (SCTF) System – A form of DOAS

Decoupling Ven-la-on From Cooling

DEMAND VENTILATION & DEMAND COOLING at the Independent zone level Achieved in the case of SCTF System

SCTF System with Compartmented Cooling Coil


F/A VAV Box

R/A VAV Box

Mixing Box

CO2 T

To other VAV Boxes In Other Zones

R/A S/A

Typical Zone VAV Box

ΔP

ΔP

F/A VAV Fan

R/A

F/A

CHWS

CHWR Modulating Valve

By-pass Damper

F.A Filter F/A Comp Coil

R/A Filter

R/A Comp Coil

R/A VAV Fan

SCTF Air-conditioning and Air Distribution System (US and PCO Patents)


25/9/14


R/A plen

um

R/A Filte

r

R/A Co

il Co

mpa

rtmen

t R/A Drain Pa

n

R/A Fan

R/A

Filter

Compa

rtmen

t Ac

cess doo

r

R/A

Fan

Co

mpa

rtmen

t Ac

cess doo

r

F/A plen

um

F/A Filte

r

F/A Co

il Co

mpa

rtmen

t

F/A Drain Pa

n

F/A Fan

F/A

Filter

Compa

rtmen

t Ac

cess doo

r

F/A

Fan

Co

mpa

rtmen

t Ac

cess doo

r Single Coil Twin Fan AHU & FCU


SCTF system for independent conditioning of fresh air and return air streams – A Psychrometric Performance

Return Air R/A : ON Coil VAV System 2 : Coil Condition Curve R/A : OFF Coil

Outside Air O/A : ON Coil VAV System 1 : Coil Condition Curve O/A : OFF Coil

Space Condition

10-15% energy savings


25/9/14


Comparison of Energy Consumption

02468

101214

Conventional SCTF

Type of System

Coo

ling

Cap

acity

(kW

)SCTF Prototype Findings

12% Co

oling (a

ir-cond

itionin

g) ener

gy savin

gs


Field Trial – A Test-Bedding Project

The Enterprise Challenge (TEC) Grant

DESIGN DATA F/A = 5,400 cmh R/A = 60,000 cmh Coil Cap = 86 kW (F/A) 233 kW (R/A)

Bldg TOP = June 2005 SCTF Installed = June 2005

Air-conditioned = 2,750m2 Floor Area for SCTF system


25/9/14


Conference Room

Meeting Room

SCTF AHU

Core

Return-duct mountedT & CO2 sensors

Staircase

OpenPlan Space

Individual Offices

F/AR/A

12

3

4

5

Conference Room

Meeting Room

SCTF AHU

Core

Return-duct mountedT & CO2 sensors

Staircase

OpenPlan Space

Individual Offices

F/AR/A

12

3

4

5

Field Trial – A Test-Bedding Project

The Enterprise Challenge (TEC) Grant Professor Chandra Sekhar


25/9/14


Fiel

d Tr

ial –

A

Test

-Bed

ding

Pro

ject

9 ppm


Temperature (Level 3)

182022242628

06/26/06

06/26/06

06/27/06

06/28/06

06/28/06

06/29/06

06/30/06

06/30/06

2006-7-1

2006-7-2

2006-7-2

Time

T(C)

point 1

point 2

point 3

point 4

point 5

Relative Humidity (Level 3)

40455055606570

06/26/06

06/26/06

06/27/06

06/27/06

06/28/06

06/28/06

06/29/06

06/30/06

06/30/06

2006-7-1

2006-7-1

2006-7-2

Time

RH(%)

point 1

point 2

point 3

point 4

point 5

Fiel

d Tr

ial –

A

Test

-Bed

ding

Pro

ject

Indo

or te

mpe

ratu

re

rang

e : 2

1.8

- 23.

8 °C

Av

erag

e =

23 °C

Indo

or re

lativ

e hu

mid

ity

rang

e : 4

7 - 5

4 %

RH

Av

erag

e =

50 %

RH


25/9/14


Dynamic Response Characteristics of the

SCTF System

Prof Chandra SEKHAR, NUS Professor Chandra Sekhar

Continuous plot of CO2 levels in various sampling points in the occupied zones in Level 3 (CO2 set point = 1000 ppm)

Time Occ

Density VSD FA Fan(Hz)

VSD RA Fan(Hz)

9:00 75 27.3 32.1 9:30 75 27.4 31.9

10:00 82 27.3 31.9 10:30 75 27.3 31.9 11:00 77 27.4 31.9 11:30 78 27.3 31.9 12:00 70 27.1 31.9 12:30 79 27.1 31.7 13:00 15 27.1 31.5 13:30 30 27 31.2 14:00 48 27 31 14:30 74 27.4 31.9 15:00 74 27.3 31.9 15:30 74 27.4 32.1 16:00 74 27.3 31.9 16:30 78 27.3 32.2 17:00 75 27.2 31.9 17:30 76 27.2 31.5 18:00 71 27 31.4 18:30 35 26.5 31.2 19:00 5 26.2 31

CO2 Set-point = 1000 ppm

TLV

Sunny Day


25/9/14


Continuous plot of CO2 levels in various sampling points in the occupied zones in Level 3 (CO2 set point = 500 ppm)

Time Occupant Density

VSD FA Fan(Hz)

VSD RA Fan(Hz)

9:00 72 40.5 35.3 9:30 76 41 35.6

10:00 74 41.1 35.6 10:30 73 41.2 35.6 11:00 76 41.2 35.5 11:30 71 41.2 35.6 12:00 78 41.5 35.5 12:30 70 41.3 35.1 13:00 20 41.1 34.9 13:30 23 40.2 34.6 14:00 42 40.5 34.6 14:30 72 41.2 35.1 15:00 74 41.6 35.3 15:30 74 41.6 35.6 16:00 72 41.6 35.6 16:30 68 41.5 35.6 17:00 69 41.2 35.7 17:30 71 41.2 35.6 18:00 68 32.8 34.8 18:30 17 27.4 33.8 19:00 5 27.2 32.2

CO2 Set-point = 500 ppm

TLV

Sunny Day


Zero Energy Building @ BCA Academy


25/9/14


0

2000

4000

6000

8000

10000

12000

14000

6:00 am

7:00 am

8:00 am

9:00 am

10:00 am

11:00 am

12:00 pm

1:00 pm

2:00 pm

3:00 pm

4:00 pm

5:00 pm

6:00 pm

7:00 pm

8:00 pm

Air

flo

w

[m3 /

h]

AHU 2-1 Recirculated Airflow

Fresh Airflow

SCTF Fresh Airflow

Actual F/A is independent

and controlled by CO2 sensors

IMPROVED FRESH AIR CONTROL

Reduced F/A during low occupancy hours

Slightly less F/A in afternoon during high

occupancy hours

Fresh air is a constant percentage

(20.6%)

Prof Chandra SEKHAR, NUS

Professor C

handra Sekhar

AHU 2-1

AHU 3-1

AHU 3-2

AHU 3-3

Baseline

cooling

[kW]

14300

7930

5600

4530

Actual

cooling

[kW]

12400

7530

3950

3890

Percent

difference *

[%]

13.28

5.05

29.46

14.13

IMPROVED FRESH AIR CONTROL = LESS ENERGY !!!

* SAVINGS FOR APRIL 2010.

Prof Chandra SEKHAR, NUS

Professor C

handra Sekhar

25/9/14


Personalized Ventilation (PV) system


Personalised Ventilation (PV) System

Deliver fresh air directly to the Occupant breathing zone

Potential to enhance •  Acceptability of ventilation •  Indoor Air Quality •  Thermal comfort


25/9/14


CHWR

SECONDARY AHU

CH

WS

CHWR

E/A

U/F Supply P/V

Sec S/A

(P/V + Sec) R/A

CHWS : Chilled water supply P/V : Personalised ventilation F/A : Fresh air CHWR : Chilled water return U/F Supply : Under floor supply R/A : Return air AHU : Air Handling Unit Sec S/A : Secondary supply air E/A : Exhaust air

R/A

CHWS

100% F/A

PRIMARY AHU

CHWS

CH

WR


Desk-mounted PV System integrated with

Ceiling Supply MV System

Gong, N, K W Tham, AK Melikov, DP Wyon, S C Sekhar and K W Cheong, "The acceptable air velocity range for local air movement in the Tropics". HVAC&R Research, International Journal of Heating, Ventilating and Air-Conditioning Engineers (ASHRAE), Vol 12, No. 4, pp 1065-1076, (October 2006). (United States).

Sekhar, S C, N Gong, K W Tham, K W Cheong, A.K. Melikov, D.P. Wyon and P.O. Fanger, "Findings of personalised ventilation studies in a hot and humid climate". International Journal of Heating, Ventilating, Air-conditioning and Refrigerating Research (HVAC&R Research), Vol 11, no. 4


25/9/14


•  Ambient and PV air temperatures

•  Thermal comfort parameters within the occupied zone

•  Breathing temperature in the occupant breathing zone

•  Concentration levels of various indoor pollutants

•  SF6 tracer gas measurements - ventilation effectiveness

•  Questionnaire responses

Experimental Protocol

52 Professor Chandra Sekhar

00.20.40.60.81

1.21.41.61.82

Vent

ilatio

n Ef

fect

iven

ess

26-23-15

26-26-15

26-20-7

26-23-7

26-0-15

Experimental conditions

• Higher the Better• Saves ENERGY

PV

WithoutPV


25/9/14


-1.00

-0.50

0.00

0.50

1.00

1 2 3 4 5 6 7 8 9 10 11

Ther

mal

com

fort

acce

ptab

ility

Subjects

With PV W/O PV

Mean responses of Thermal Comfort acceptability

Very Acceptable

Very Unacceptable


-1.00-0.80-0.60-0.40-0.200.000.200.400.600.801.00

1 2 3 4 5 6 7 8 9 10 11

IAQ

acc

epta

bilit

y

Subjects

with PV without PV

Mean responses of IAQ acceptability

Very Acceptable

Very Unacceptable


25/9/14


PV system Consistent trends of thermal comfort & IAQ ratings Observed – INCREASE with INCREASING PV flow rate And DECREASING with INCREASING PV temps at Ambient temp of 26° C

59 Professor Chandra Sekhar

•  A warmer space temperature, such as 26 °C, accompanied by a PV air temperature of 23 °C, implies that the space cooling load is reduced in comparison with a conventional air-conditioning system in which the space is typically maintained at 23 °C.

•  An absolute reduction in the total fresh air quantity provided is possible, as it is now directly supplied as inhaled air to the occupant breathing zone.

Energy savings occur due to


25/9/14


Ceiling-Mounted PV System integrated with

Ceiling Supply MV System


YANG, B, Arsen Melikov and S C Sekhar, "Performance evaluation of ceiling mounted personalized ventilation system". ASHRAE Transactions 2009, Vol. 115, Part 2, pp 395-406. (United States).

Yang, B, S.C.Sekhar and Arsen Melikov, “Ceiling mounted personalized ventilation system integrated with a secondary air distribution system – A human response study in hot and humid climate”. Indoor Air – International Journal of Indoor Environment and Health (2010). Volume 20, no. 4 (2010): 309-319. (Denmark).

YANG, B, S C Sekhar and Melikov Arsen, "Ceiling mounted personalized ventilation system in hot and humid climate –An energy analysis". Energy and Buildings, (2010). (Switzerland).

Yang, B and S C Sekhar, "Three dimensional numerical simulations of a hybrid fresh air and recirculated air diffuser for decoupled ventilation strategy". Building and Environment, (2007), Vol.42, Issue 5, pp 1975-1982. (United Kingdom).

Ceiling mounted PV System integrated with ambient MV system


25/9/14


CFD simulation

more fresh air is supplied directly into the breathing zone without mixing with recirculated air and much better IAQ in the occupied zone can be realized.


◊ 23.5/21

□ 23.5/23.5

∆ 26/21

Χ 26/23.5

﹡ 26/26

0.0

0.1

0.1

0.2

0.2

0.3

0 4 8 12 16

PV airflow rate (L/s)

Inhaled air quality

Y-ax

is

-1 =

ver

y un

acce

ptab

le,

0 =

just

una

ccep

tabl

e/ac

cept

able

, +1

= v

ery

acce

ptab

le

Ceiling-mounted PV system in conjunction with ceiling supply mixing ventilation system


25/9/14


Desk-mounted PV System Integrated with UFAD System

Li Ruixin, S.C.Sekhar and Arsen Melikov, “Thermal comfort and IAQ assessment of under-floor air distribution system integrated with personalized ventilation in hot and humid climate”. Building and Environment journal, Vol 45 (2010): 1906-1913. (United Kingdom).

Li, Ruixin, S.C.Sekhar and A.K.Melikov, 2011. Thermal Comfort and Indoor Air Quality in rooms with Integrated Personalized Ventilation and Under-Floor Air Distribution Systems. HVAC&R Research, Volume 17, Number 5, pp 829-846 ,ASHRAE .


Field Environmental Chamber (FEC) experimental setup - Desk mounted PV with UFAD system


25/9/14


y = 1.4807x - 41.198 R² = 0.85823

y = -0.6024x + 84.891 R² = 0.68715

0

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

80

90

100

72 74 76 78 80 82 84 86 88

Perc

eive

d in

hale

d ai

r tem

pera

ture

Per

ceiv

ed in

hale

d ai

r fre

shne

ss

Acceptability of perceived air quality

inhaled air freshness

inhaled air temperature

Cold

Hot Fresh

Stuffy


Key Findings

•  The use of PV-UFAD improved subjects’ thermal sensation in

comparison with UFAD alone or mixing ventilation.

•  The “cold feet” complaint decreased when the temperature of the

air supplied from the UFAD was increased.

•  The use of the PV provided the subjects with the preferred slightly

cool thermal sensation at the head and face.

•  Local cooling of the head and face could be achieved by

decrease of the temperature of the personalized air or increase

of its flow rate, i.e. increase of the air velocity at the head and

face region. Professor Chandra Sekhar

25/9/14


Energy Efficient Healthy Buildings – Decoupled Ventilation Systems

Air-conditioning Systems

• Dedicated Outdoor Air System • Single Coil Twin Fan System

Final Words

Air Distribution Systems

• Single Coil Twin Fan • Personalized Ventilation with Mixing Ventilation • Personalized Ventilation with UFAD



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