Environmental Fluid Mechanics

, Volume 16, Issue 2, pp 347–371 | Cite as

The role of materials selection in the urban heat island effect in dry mid-latitude climates

  • Androula Kakoniti
  • Gregoria Georgiou
  • Konstantinos Marakkos
  • Prashant Kumar
  • Marina K.-A. Neophytou
Original Article

Abstract

This work investigates the role of materials selected for different urban surfaces (e.g. on building walls, roofs and pavements) in the intensity of the urban heat island (UHI) phenomenon. Three archetypal street-canyon geometries are considered, reflecting two-dimensional canyon arrays with frontal packing densities (λf) of 0.5, 0.25 and 0.125 under direct solar radiation and ground heating. The impact of radiative heat transfer in the urban environment is examined for each of the different built packing densities. A number of extreme heat scenarios were modelled in order to mimic conditions often found at low- to mid-latitudes dry climates. The investigation involved a suite of different computational fluid dynamics (CFD) simulations using the Reynolds-Averaged Navier–Stokes equations for mass and momentum coupled with the energy equation as well as using the standard k-ε turbulence model. Results indicate that a higher rate of ventilation within the street canyon is observed in areas with sparser built packing density. However, such higher ventilation rates were not necessarily found to be linked with lower temperatures within the canyon; this is because such sparser geometries are associated with higher heat transfer from the wider surfaces of road material under the condition of direct solar radiation and ground heating. Sparser canyon arrays corresponding to wider asphalt street roads in particular, have been found to yield substantially higher air temperatures. Additional simulations indicated that replacing asphalt road surfaces in streets with concrete roads (of different albedo or emissivity characteristics) can lead up to a ~5 °C reduction in the canyon air temperature in dry climates. It is finally concluded that an optimized selection of materials in the urban infrastructure design can lead to a more effective mitigation of the UHI phenomenon than the optimisation of the built packing density.

Keywords

Heat transfer Urban microclimate Urban design Building design Road design CFD RANS simulations 

Abbreviation

Af

Windward (frontal) area of the building array

AT

Building lot area

cpm

Specific heat capacity (J kg−1 K−1)

d

Displacement height (m)

H

Street canyon height (m)

k

Turbulent kinetic energy per unit mass (m2 s−2)

K

Thermal conductivity (W m−1 K−1)

Kt

Turbulent thermal conductivity (W m−1 K−1)

Pr

Prandtl number (-)

Re

Reynolds number (-)

Ri

Richardson number (-)

TA

Ambient air temperature (K)

Tref

Ambient (inlet) reference air temperature (K)

TS, Thot

Street surface temperature (K)

Tth.comfort

Air temperature for thermal comfort (=298 K)

T

Computed temperature (K)

u*

Friction velocity (m s−1)

Uambient

Ambient air velocity magnitude (m s−1)

Ui

Mean streamwise and vertical velocity (m s−1)

U+

Dimensionless velocity magnitude (=U/Uambient)

W

Street canyon width (m)

zo

Surface roughness length (m)

δ

Boundary layer height (m)

ε

Emissivity (-)

ε

Dissipation rate of turbulent kinetic energy (m2 s−3)

κ

Von Karman constant (0.4)

λf

Frontal packing density (−)

ρ

Density (kg m−3)

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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Androula Kakoniti
    • 1
  • Gregoria Georgiou
    • 1
  • Konstantinos Marakkos
    • 1
    • 4
  • Prashant Kumar
    • 2
    • 3
  • Marina K.-A. Neophytou
    • 1
  1. 1.Environmental Fluid Mechanics Laboratory, Department of Civil and Environmental EngineeringUniversity of CyprusNicosiaCyprus
  2. 2.Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences (FEPS)University of SurreyGuildfordUK
  3. 3.Environmental Flow (EnFlo) Research Centre, FEPSUniversity of SurreyGuildfordUK
  4. 4.The Cyprus Institute, Energy and Environment and Water Research CenterNicosiaCyprus

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