Individually Controlled Environment
Design of Indoor Environment
Arsen K. Melikov
October 21 2010, CTU in Prague
International Centre for Indoor Environment and Energy
Department of Civil Engineering, Technical University of Denmark
www.ie.dtu.dk
1
Individual Differences
• Clothing insulation: 0.4 – 1.2 clo
• Metabolic rate: 1 – 2 met
• Preferred temperature: 10°C
• Preferred velocity: 4 times
2
1
Total volume ventilation
• Clean air is supplied
far from occupants
• Uniform environment
• Limited control
Personalized ventilation
• Clean air is supplied
to the breathing zone
• Individual control &
Preferred environment
3
Personalized Ventilation
• Preferred environment
• More satisfied occupants
• Increased productivity
• Energy savings
4
2
Personalized Ventilation
5
Inhaled Air Quality
Veff ≈ 1
Veff ≈ 1.4 (6)
PERSONALIZED
VENTILATION
Veff ≈ 2 – 100 (∞)
6
3
Perceived Air Quality
Ventilation effectiveness
is defined as the
concentration of pollution
in exhaust air divided by
the concentration of
pollution in inhaled air.
Percentage dissatisfied (%)
35
23degC
Power (23degC)
30
Mixing
ventilation
25
20
Displacement
ventilation
15
PV
10
5
0
0
2
4
6
8
10 12
Ventilation effectiveness 7
Personalized Ventilation: Design Strategies
8
4
Individually Controlled Environment
9
Design of Personalised Ventilation
• Occupants’ comfort & health
• Energy use
• Implementation in practice
10
5
Design of Personalised Ventilation
Occupants’ comfort & health
• high inhaled air quality
• preferred thermal comfort
• transport of contaminant
Interaction of
flows around
human body
• minimised cross-infection
11
Airflows at Workplaces
1. Ventilation flow
1
5
4
2
3
2. Personalized flow
3. Free convection flow
4. Respiration flow
5. Thermal flows
Complex Airflow Interaction!
12
6
Personalized Flow
• Free (impinging) jet or wall type jet
• Development depends on initial conditions including:
initial velocity and turbulence intensity, shape of nozzle,
isothermal or non-isothermal, relative humidity, etc.
• Less mixing of the supplied clean and cool air with
the surrounding warm and polluted air is important
13
Personalized Flow
D
• Re < 300 – creep flow
• 300 < Re <1000 – laminar flow
H
D
H
D im en s io n le ss V elo city U /U o
• Re > 3000 – turbulent flow
1,2
D=0,2 m
H=0,05 m, L=0,63 m
1
0,8
0,6
0,4
0,2
0
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 1 1,2 1,4 1,6 1,8 2
Distance (m)
Uo – mean velocity at exit (m/s); U – mean velocity along axis (m/s)
14
x – distance from nozzle along jet axis (m)
7
Free Convection Flow
Depends on:
• difference in temperature of
body surface and room air
Mean Velocity [m/s]
• body posture
0,2
Lower Chest
0,16
Face
0,12
0,08
0,04
0
0
50
100
150
200
Distance [mm]
Homma 1989
250
300
15
Thermal Plum above Human Body
Thermal
Plume
Impact of:
Shape
Clothing design & insulation
Chair design
16
8
Thermal Plume above Human Body
For nude manikin:
Enthalpy flux: Q = 31 W; Volume flux: V = 0.0961 m3/s
Momentum flux: I = 0.0150 N; Buoyancy flux: P = 0.0065 N/m
140
Cylinder
Rectangular box
Dummy
120
40%
100
%
80
60
40
20
0
Q
V
1
I
P
17
Zukowska et al. 2007
Flow of Exhalation
Exhalation: nose
Inhalation: mouth
Exhalation: mouth
Inhalation: nose
0.7 m/s
0.4 m/s
1.2 m/s
1.4 m/s
0.7 m/s
0.4 m/s
18
9
Airflow Interaction
Interaction of
Personalized Flow
Convection Flow
19
Convection Flow & Personalized Flow
Thermal comfort and inhaled air quality depends on
the penetration of the free convection flow by the
personalized flow
Personalized flow:
• direction
Inhaled
• air temperature
Air
• mean velocity
Quality
• turbulence intensity
• frequency of velocity fluctuation
Thermal
Sensation
Distance between air supply device and body 20
10
Convection Flow & Personalized Flow
Impact of Airflow Direction on Thermal Comfort
Transverse flows Assisting flows Opposing flows
21
Convection Flow & Personalized Flow
Impact of Airflow Direction & Velocity: Heat Transfer
Assisting
Flows
Opposing
Flows
22
Mayer & Schwab 1988
11
Personalized Ventilation
Personal exposure effectiveness:
Ci without PV – Ci with PV
PEE =
Ci without PV
23
Free Convection Flow & Personalized Flow
Inhaled Air Quality
100
Personal Exposure
Effectiveness [%]
Transverse
Flow
Transverse
Flow
80
60
40
20
23/20°C
26/20°C
0
0
2,5
5
7,5
10
12,5
15
Flow rate [l/s]
Assisting
Flow
100
Personal Exposure
Effectiveness [%]
Assisting
Flow
80
60
40
26/20°C
20
0
0
2,5
5
7,5
10
Flow Rate [L/s]
12,5
15
24
12
Interaction of
Ventilation Flow
Convection Flow
25
Ventilation Flow & Convection Flows
26
13
Ventilation Flow & Convection Flow
Volume fluxc < Volume Fluxm
2,0
1,5
24% difference in stratification
height
2,5
due to use of simplified
body shape!
2,0
Cylinders
1,0
0,5
0,0
Height above floor [m]
Height above floor [m]
2,5
1,5
Manikins
1,0
0,5
0,0
0%
50%
100%
150%
200%
CO2 concentration ratio (C-Cs)/(Ce-Cs)
0%
50%
100%
150%
200%
CO2 concentration ratio (C-Cs)/(Ce-Cs)
27
Zukowska et al. 2008
Interaction of
Exhalation Flow
Convection Flow
Ventilation Flow
28
14
Airflow Interaction
G.Settels, Penstate Univ., USA
Free Convection flow & Exhalation Flow
Background
Exhalation flow flow & Personalized Flow
Ventilation Flow
29
Airflow Interaction
Convection flow & Exhalation Flow &Ventilation Flow
RMP
VDG
Exposed
Polluting
N 2O
SF 6
CO 2
MV
DV
texhaust = 26°C; tPV = 20°C
VPV = 15 L/s; Vtotal = 80 l/s
30
Melikov et al. 2003
15
Airflow Interaction
The results show how many times PV in conjunction with MV or DV
decreased contaminants in inhaled air in comparison with MV alone
RMP
VDG
CO2 – floor pollution 30.3
N2O – bioefluents
SF6 – exhaled air
24.0
19.1
MV
DV
11.9
Melikov et al. 2003
10.5
7.0
1.0 1.0 1.0
no PV
5.5 6.2
2.9 3.0 2.8
1.1
VDG
RMP
Mixing ventilation (MV)
no PV
3.1 2.7 3.1
VDG
RMP
31
Displacement ventilation (DV)
Thank you!
32
16