Transcript New Turbulence Models for Indoor Airflow Simulation

Sustainable Buildings for China
Professors Leon Glicksman1, Yi Jiang2, and
Qingyan (Yan) Chen1
1Massachusetts
Institute of Technology, USA
2Tsinghua University, Beijing, China
January 7, 1999
Background
Increased purchasing power due to
economy growth
 Demand for improved living standards
Winter heating
Summer cooling
Larger floor area per person
 Largest producer of air conditioners

Background
Winter Heating:
 130 million tons standard coal for urban heating
 248-260 million tons standard coal for rural
heating
 30% of Chinese total energy consumption
 Heating region is expanded to Shanghai and
Wuhan (below Yangtze River)
Background
Summer Cooling:
 35% of residential buildings in Beijing
 65% of residential buildings in Shanghai
 50% of residential buildings in Guangzhou
 20%-25% annual increase in sales
Problems
High
demand for electricity in summer
Heat and noise pollution in micro-climate
Effect on the environment
Future growth (American level?)
U.S. Buildings
1/3
of total energy
1/2 of electricity
90% of time spent indoors
Major health problems: indoor climate
Basic Deficiencies
Very poor windows, single glazed, poorly fitted
 Little or no insulation
 Absence of summer shading
 Poor maintenance
 Rapid deterioration

Current Chinese Housing Policy
Will turn to market system in 1999
 Will encourage the housing industry to
absorb public savings
 Will maintain economic growth
Consequences:
High speed growth in housing industry
Demand for high quality housing

Current Proposed Strategies for Energy
Conservation in Chinese Housing
Insulation of building fabrics
 Improvement of windows to reduce
infiltration
 Improvement of district heating systems
 Metering system for heating
 Improvement of lighting systems

Problems Remaining in
Chinese Housing
Little consideration for summer cooling
 Little consideration of natural ventilation
 Little consideration of building forms
 Little consideration of indoor air quality
 No alternative for room air-conditioners

An Example of Current Design:
A 30 cm (12 inch) concrete wall
Identify and Develop Solutions
for Urban Buildings in China
Energy efficient
 Simple and generic
 Appropriate for local area
 Cost effective
 Acceptable by local people
 Use of local material and labor

Environmental Impacts of 1m2 Brick Wall
over 40 years, for Beijing Climate
coal fired district heating
% of zero insulation case
embodied in wall structure and insulation
no insulation
28823
2812
5cm of insulation
18093
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
MJ
Energy
Energy
CO2eq.
SO2eq.
Global
Acid
Global
Acid
Warming
Rain
Warming
Rain
37cm
10cm of insulation
10355
1017
6123
MJ
CO2eq.
SO2eq.
Energy
Global
Acid
Energy
Global
Acid
[MJ]
Warming
Rain
Warming
Rain
[kg CO2 equiv.] [kg SO2 equiv.]
5cm 37cm
100
90
80
70
60
50
40
30
20
10
0
7068
695
3979
MJ
Energy
Energy
CO2eq.
Global SO2eq.
Acid
Global
Acid
Warming
Rain
Warming
Rain
10cm
37cm
Building Insulation and Heat Pump
(1m2 of Block Wall, for Beijing Climate)
Heating Costs, heat-pump COP 3, electricity from coal,
total of 40 years, discount-rate 7%
150
US$
100
50
0
106
0
Investment Costs for
Power Generation
150
US$
20
36
11
37
Initial
Investment in
Insulation
20
25
Net Savings
56
62
13
7
Generation
Capacity
Savings
100
50
0
69
Global Warming from Heating
kg CO2 equiv. over 40 years
5,000
4,000
3,000
2,000
1,000
0
Key Point:
Provide healthy and
comfortable living space with
little or no energy consumption
in summer
The Team


Technology Development, Design, Evaluation, and Training
 MIT, USA
 Tsinghua University, China
 Tongji University, China
Construction (Demonstration projects)
 Beijing: Vanke Property Development Co.
万科房地产发展公司
 5-floor luxury housing
 12-floor affordable housing
 30-32 floor middle-class housing
 Shanghai (To be identified)
Technologies to Improve
Building Design
Ventilation
Natural ventilation
Night cooling and thermal storage walls
Advanced mechanical ventilation systems
 Shading devices and passive solar
 Heat pumps
 Desiccants dehumidification

Possible Solutions
Natural ventilation to replace air conditioning
 Thermal mass and night cooling
 Ground coupled heating and cooling systems
 Centralized energy systems
 Improved windows
 Application of vernacular technologies
 Overall building design
 Incentives for adoption of energy efficient
designs

Improvement of Windows
Double glazing
 New types of frame
 Better insulation
 Lower infiltration with acceptable indoor
air quality

Improvement of District Heating
High efficiency by CHP
 Large scale network with multi-heat sources
 High reliability by loop network combined with
computer added fault detection system
 Special control policy to make buildings being
heated equally
 Energy reduced from 50 W/m2K to 30 W/m2K

Metering System for Heating
Largest potential saving in heating
 25% - 40% savings in test buildings
 Difficulties:
Strongly related to the housing reform
Indoor system has to be changed
High cost for installation

Energy Savings
30% of energy saving by improving the
fabric
 Additional 20% of energy saving by better
control of the district heating system
 Additional 20% of energy saving by use of
metering systems for heating

A Study in Beijing:
Results from 83 apartments

Measurements of the room air
temperatures over a two-month period
Shading by device
Shading by vegetation
Ventilation
Building layout
Low and Middle Rise Housing
High Rise Housing
Thermal Environment
kitchen
North
Bedroom
Entrance
Living room
Door
Window
WC
RHLog
Bedroom
Bedroom
Balcony
Shading Comparison
Shading Comparison
31. 5
31. 0
30. 5
T emperat ure( degree C)
30. 0
29. 5
29. 0
28. 5
28. 0
27. 5
NoWitshading
h Sunshi ne
Wi t hout Sunchi ne
Shaded
27. 0
26. 5
26. 0
T i me
Vegetation Comparison
Vegetation Comparison
31. 0
30. 5
30. 0
T emper at ur e( degr ee C)
29. 5
29. 0
28. 5
28. 0
27. 5
27. 0
26. 5
26. 0
25. 5
Vi rescence
Little Low
vegetation
Lots of
vegetation
Hi gh
Vi rescence
25. 0
24. 5
24. 0
T
i me
Use of Vegetation
Reduction on solar radiation
Direct radiation on the building surfaces
Reflection from the ground
 Improvement in building micro climate
Reduction of outdoor air temperature
Change of air movement
Improvement on air quality
Decrease of noise

Comparison between Mechanical
and Natural Ventilation
Balcony
Other’s room
Bed room
North
Entrance
Living room
Bed room
WC
Kitchen
Comparison between Mechanical
and Natural Ventilation
32. 0
31. 5
31. 0
T emperat ure( degree C)
30. 5
30. 0
29. 5
29. 0
28. 5
28. 0
27. 5
27. 0
Nat ure Vent i l at i on
Natural
Mechani cal Vent i l at i on
Mechanical
26. 5
26. 0
T i me
Different Natural
Ventilation Designs
33. 0
32. 5
T emperat ure( degree C)
32. 0
31. 5
31. 0
30. 5
30. 0
29. 5
29. 0
28. 5
28. 0
27. 5
27. 0
Baddesign
Vent i l at i on
Bad
Good
design
Good Vent
i l at i on
26. 5
26. 0
25. 5
25. 0
T i me
Comparison of Different
Apartment Layouts

Different apartments in the same flat can
result in 300% difference in cooling load

Careful arrangement of the kitchen,
bathroom and corridor can greatly
reduce cooling demand
Use of Air Conditioners:
A survey over 300 apartments
Results from the Survey
Age
Sex
Like AC (%)
Neutral (%)
Dislike AC (%)
< 19
20-40
40-60
> 60
M
F
M
F
M
F
M
F
42.86 52.00 48.57 35.59 37.50 31.25 22.22 29.63
42.86 32.00 42.86 52.54 37.50 37.04 37.04 33.33
14.29 16.00 8.57 11.86 25.00 25.93 40.74 37.04
Why like AC:
Why dislike AC:
1. Cool 40%
2. Modern Technology 34%
3. Climate control 23%
4. Others 3%
1. Separated with the nature 47%
2. Draft and noise 26%
3. Energy and first costs 23%
4. Others 4%
Preliminary Understandings:
The survey results
Comfort does not mean a low air
temperature in summer
 Air-conditioning may not be necessary in
Beijing with acceptable comfort
 The use of air-conditioning can be
reduced greatly in southern China

Sustainable Housing for China
Be comfortable
 Be healthy
 Be energy efficient
 Be economic
 Be flexible and integral to the culture

Building Energy Distribution (Winter)
H e a ti n g L o s s e s in B e iji n g W in t e r
W indo w
C o nd uc tio n
27 %
W a lls
32%
R oof
7%
Infiltra tio n L o a d
3 4%
Current Building
Window and Wall Insulation (Winter)
Heating Energy Consumption Comparation
Beijing Winter
(KWH/m^2)
80
70
60
50
40
30
20
10
0
Brick Wall
37cm Brick
U=1.51W/m^2K
Insulation Wall
5cm Performed Mineral
Board,U=0.54W/m^2K
Sigle Glazing
Window
Sigle Glazing
Window
U=6.31W/m^2K
U=6.31W/m^2K
Insulation Wall
+Double Glazing
Window
U=2.79W/m^2K
Building Energy Distribution (Summer)
Cooling Load of Building in Beijing Summer
Latent Load of
Occupant
13%
Wall
9%
Roof
4%
Sensible Load of
Infiltration
1%
Sensible Load of
Internal Heat
23%
Window Solar
Radiation.
27%
Latent Load of
Infiltration.
22%
Window
Conduction.
1%
Window and Wall Insulation (Summer)
Cooling Energy Consumption Comparation
Beijing Summer
(KWH/m^2)
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00
Brick Wall
37cm Brick
U=1.51W/m^2K
Insulation Wall
5cm Performed Mineral
Board,U=0.54W/m^2K
Sigle Glazing
Window
Sigle Glazing
Window
U=6.31W/m^2K
U=6.31W/m^2K
Insulation Wall
+Double Glazing
Window
U=2.79W/m^2K
Natural Ventilation:
Building design
Natural Ventilation Design
Natural Ventilation
Natural ventilation:
Airflow at MIT campus
Comfort Hours with Natural Ventilation
C o m f o r t H o u r s B e ijin g
0
0
0
0
0
24
30
31
83
0
0
45
1028
51
197
584
h o u rs p e r mo n t h ( y e a r)
273
214
1083
244
C o m fo rt Z o n e s
f o r D e v e lo p e d
C o u n t r ie s
( B . G iv o n i)
503
142
H o t a n d /o r H u m id
744
672
744
213
720
699
637
C o m f o r t 2 m /s
C o m fo rt
744
B e lo w c o m f o r t
245
6062
451
ea
Y
em
ec
D
r
r
be
be
er
ct
O
m
S
ep
te
ug
A
ob
be
t
us
ly
Ju
ne
Ju
ay
M
il
pr
A
ar
M
ua
br
Fe
ch
ry
y
ar
nu
Ja
em
71
ov
66
27
135
N
186
r
148
r
418
Comfort Hours with Natural Ventilation
C o m fo r t H o u r s B e ijin g
0
0
0
0
0
10
21
15
33
110
121
0
0
554
107
111
677
h o u rs p e r m o nt h ( y e a r)
308
1750
131
319
345
744
672
744
720
H o t a n d /o r H u m id
C o m fo rt 2 m /s
C o m fo rt
B e lo w c o m fo rt
744
625
257
375
5623
331
331
333
152
ea
Y
be
em
ec
D
r
r
r
be
em
ov
N
O
ct
ob
be
te
ep
S
A
ug
m
us
ly
er
r
23
t
5
Ju
ne
Ju
ay
M
il
pr
A
ch
ar
M
Fe
br
ua
ar
y
ry
83
nu
(B . G iv o n i)
235
599
Ja
C o m fo r t Z o n e s
fo r D e v e lo p in g
C o u n tr ie s
Natural Ventilation:
Night cooling
32
30
E x te r n a l T e m p e r a t u r e ( ° C )
In te r n a l T e m p e r a t u r e ( ° C )
W a ll T e m p e r a t u r e ( ° C )
28
26
24
22
20
18
16
1
2
3
4
5
6
7
8
9
Night Time
Walls Release Heat
Maximum Ventilation
10
11
12
13
14
15
16
17
18
19
20
21
22
Day Time
Walls Absorb Heat Gains
Minimum Ventilation
23
24
ho u r
Shading Devices (Summer)
C o o lin g L o a d D u e to S o u th W in d o w s
(K W H /m ^ 2 )
S h an g h ai S um m er
1 40.0
1 20.0
S e p te m b e r
1 00.0
A ug e s t
J uly
80.0
J un e
60.0
40.0
20.0
0.0
F u l l S h a d in g fo r S o u t h
W in d o w s
N o S h a d in g fo r S o u th
W in d o w s
D iff e r e n t D e s ig n
Ground Temperature Changes
with Heat Pump
T e m p e ra tu re [C ]
0
2
4
6
8
10
Dense Rock
12
0 .0
k
r
Cp
a
5 0 .0
D e pth [m ]
1 0 0 .0
y ea r
W/mK
kg/m3
J/kg
m2/s
3.46
3204
836
1.3E-06
10
1 5 0 .0
50
10 0
2 0 0 .0
2 5 0 .0
3 0 0 .0
average heat extraction /year:
50MJ/m2
Desiccant System
Outdoor air
Outdoor
Desiccant
regeneration
Heat exchanger
sun
air
Cooling tower
Room
Cooling coil
Desiccant
adsorption
Operation of Desiccant System
Desiccant dehumidification + Cooling Tower
Small Chiller
Desiccant Cooling
R a tio o f e a c h o p e r a tio n
O p e r a tio n o f D e s ic c a n t S ys te m i n B e ij in g
w i th A S H R A E C o m f o rt Z o n e
1
0 .9
0 .8
0 .7
0 .6
0 .5
0 .4
0 .3
0 .2
0 .1
0
Jan
Feb
S o la r H e a t i n g
M ar
A pr
M ay
J un
Ju l
Aug
Sep
D e s i c c a n t + C o o li n g T o w e r
O ct
N ov
D ec
M o n th s
A d d i t i o n a l C o o li n g
Desiccant Cooling
O p e r a tio n o f D e s ic c a n t S y s te m
in S h a n g h a i
R a tio o f e a c h o p e ra t io n
1
0 .9
0 .8
0 .7
0 .6
0 .5
0 .4
0 .3
0 .2
0 .1
M o n th s
0
J an
Feb
M ar
S o la r H e a t i n g
Apr
May
Jun
Jul
A ug
Sep
D e s ic c a n t + C o o li n g T o w e r
O ct
N ov
D ec
A d d i t i o n a l C o o li n g
Support
MIT
Kann-Rasmussen Foundation
($200,000/year)
 Tsinghua University
National Natural Science Foundation
(RMB 1,000,000)

Objective
Identify energy efficient and sustainable
designs and technologies
 Use economic and appropriate solutions
for China
 Build demonstration buildings
 Publicize results to public, designers,
officials, and industry
 Prepare design guidelines
 Train designers and planners

Milestones
Background data, energy use of residential
buildings
 First order evaluation of promising systems
for energy efficiency
 In-depth study of several most promising
 Prototype design studies, model, evaluations
 Full-scale demonstrations
 Development of design guidelines
