An Intrigued Analysis to Quantify the Causes for Urban Heat Island by the Revised ArchitectureUrbanS

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An Intrigued Analysis to Quantify the Causes for
Urban Heat Island by the Revised
Architecture-Urban-Soil Simultaneous Simulation
Model, AUSSSMPart.1 Theoretical Background and
Model Frame showing with a Result of Standard
Solution

• Aya Hagishima, Jun Tanimoto
• and Tadahisa Katayama
• Kyushu University, Japan

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What is the main factors of Urban Heat Island?

• alteration of land usage
• ground covering materials
• geometric urban configuration
• increase of anthropogenic heat
• physical properties of building envelop
• mechanical performance of air-conditioning system
  etc...

• We focuses on analyzing the effects of many
  factors on the Urban Heat Island quantitatively.

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Procedures to express the heat transfer of the
urban surface in meso-scale model

• Surface-layer scheme
• albedo, evaporative efficiency, heat capacity
  etc..
• Simplest!!
• Single-layer model
• Vertical distributions of air temp. and wind
  velocity are disregarded.
• The aerodynamic and thermal impact of buildings
  are approximately considered.
• Multi-layer model Kondo(1998), Ashie(1997)
  ...
• The aerodynamic and thermal impact of buildings
  can be considered more precisely.

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Strategy for clarifying the quantitative effects
on Urban heat island

• Systematic numerical experiments using the Urban
  Canopy Model (UCM)
• What is the qualification of UCM ?
• appropriate accuracy for considering the thermal
  process among the urban canopy layer
• green covering ratio, shape of building,
  performance of air-conditioning system,solar
  reflectivity of urban surfaces, roof garden
  etc...
• Light-computational load
• for systematic large numerical experiments

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Then, we propose Architecture-Urban-Soil
Simultaneous Simulation ModelAUSSSM

• AUSSSM 1998
• Single-layer model
• It was defined as an independent simulation
  frame.
• Revised-AUSSSM 2002
• Multi-layer model
• Each sub-Model are revised more precisely!!

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Schematic frame of the revised-AUSSSM
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The grid pattern assumed in the revised-AUSSSM
Same size buildings are arrayed homogeneously
and regularly.
Normal Street Pattern
Staggered Pattern
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Urban Atmospheric Sub-Model

• 1D canopy model Kondo(1998)

G fluid volume density - aratio of wall
surface area to fluid volume m-1 G1-rr
(Maruyama,1991)
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Gambo(1978)
WatanabeKondo(1990)
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Soil Sub-Model

• 3 types of land surface are assumed
• soil, lawn and asphalt pavement
• 1D heat conductive equation
• The boundary condition
• The temperature at 50cm under the ground is
  defined as constant.
• Simplified method for identifying dynamic
  evaporation efficiency of land coverings
• bare soil, lawn vegetation and pavement

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Method for estimating the evaporation from the
soil
re,GD and C are identified by the numerical
simulation data based on the Simultaneous
Hygrothermal Transfer Equation (SHTE).
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Method for estimating the evapotranspiration
from lawn surface
Evaporation from soil

• SRLRCDCVEVL0
• k and ETR are obtained
• from experimental data.

Equivalent Thermal Resistance
Relationship between k and f (Kagawa, 1998)
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Method for estimating the evaporation from
artificial surfaces after precipitation
f?fmax
It is very similar to the method for estimating
the evaporation from soil surface. re(f/fmax)
and fmax are identified by our measurement data.
EVA
f
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Architectural Sub-Model

• Its based on the dynamic calculation theory for
  building thermal load
• Building thermal load
• Anthropogenic heat from building

Convective heat transfer
Internal heat generation
Ventilation load
Building thermal load
Total mechanical performance of HVAC system
COP and rat vary with the type of HVAC system.
(14 types are presumed!)
Ratio of sensible heat disposal to total at
exterior air-conditioning equipment
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Assumed HVAC system
HST Heat Storage Tank, DHC District Heating
Cooling Ratio of sensible to total heat disposal
at air-conditioning exterior equipment
HPair100, TR 12.5, AR 11.3
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Basic assumption used in the Standard Solution
Time series data
Based on the the investigation at the area of the
most representative office districts in Japan
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Boundary Condition

• Boundary condition at the top of SBL is based on
  the statistical measurement data during hot
  summer in Tokyo.
• Amount of precipitation is 20mm/day that occurs
  once 7 days in the early morning before sunrise.
• One simulation running continues 21 days to
  obtained a so-called periodic steady-state
  solution.

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Results of the Standard Solution
Building height

• Vertical distribution of
• air temperature and wind velocity

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Results of the Standard Solution
Building height

• before rainfall(20th day) after
  rainfall(21st day)
• Vertical distribution of specific humidity

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Daily fluctuation of wall surface
temperature(21st day)
Anthropogenic heat from Hvac systemW/m2
Fluctuation of total anthropogenic heat released
from HVAC system and COP(21st day)
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Fluctuation of surface temperature
rainfall
Precipitation
rainfall
Fluctuation of Evaporation rate from land surfaces
rainfall
rainfall
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Conclusions

• The revised-AUSSSM is proposed, which is
  classified as a multi-layer model of UCM.
• It is composed of several 1D sub-models developed
  in the authors works.
• It is characterized by its light-computing load
  that still allows for relatively high accuracy
• A standard solution targeting the typical office
  district of Tokyo in hot summer was shown.
• Systematic large numerical experiments using
  revised-AUSSSM will presented in the next
  presentation.