Porous cordierite (Mg₂Al₄Si₅O₁₈) ceramics with oriented through hole pores were prepared by an extrusion method. A paste for the extrusion was prepared by mixing cordierite powder and nylon fibers as pore formers with cellulose binder and water, and extruded by a piston extruder. After drying, the extruded rods (400 mm×60 mm^φ) were heated at 1250^oC for 4 h. The resulting porous ceramics had an apparent porosity of 46.6%, water absorption of 34.9% and bulk density of 1.34 g/cm³ (relative density of 53.4%). The microstructure shows orientation of cylindrical pores parallel to the extruded direction. The ceramics showed water pump-up ability of about 1 h for 400 mm height (h) by the capillary force. The possible pump-up height estimated from the pump-up rate (h=61.3t^0.438) is about 900 mm by 8 h and the pump-up height as high as 800 mm was confirmed by stacking of two pieces of ceramics rods. The wet ceramic rod pump-upped water showed 8.7^oC lowering of the surface temperature compared with dry ceramics when its surface temperature is 38^oC.

The sensible heat flux emitted from an urban block is considered to be one cause of urban heat island formation and can be quantified by an index: the heat island potential (HIP). Two evaporative cooling strategies to reduce the sensible heat flux by lowering the urban surface temperature are focused in this paper. One strategy is to use a pavement with a capability of water-holding, and the other is to use a water system for sprinkling the building surfaces which are coated with super-hydrophilic photocatalyst (TiO₂). Four urban blocks with different land use are selected for quantitatively analyzing the mitigating effect of the two strategies on the HIP. As a result, it was found that the reduction effect of the HIP is influenced by spatial configurations (shadow distribution), etc. The analysis was carried out based on the numerical simulations using a thermal simulation tool developed by the authors. The results from the present study can provide useful findings for making an effective use of the two strategies in the urban/built environment design.

This study implements a numerical analysis on the effects that the watering system to the photocatalyst-coated external surfaces of buildings have on the outdoor thermal environment. The heat transfer model that could predict heat and water balance on the photocatalyst-coated surface with water membrane is introduced into the outdoor heat balance simulation model developed by the authors. Substantial urban blocks in the downtown of Tokyo are selected for the analysis. The simulation results quantify the potential impacts of the cooling system on the outdoor thermal environment improvement in terms of surface temperature distributions, Mean Radiant Temperature (MRT), and the Heat Island Potential (HIP).

We have been studying the importance of rainwater cycle for heat and hydrological environment in urban area. A permeable pavement consists of some layers that have high porosity materials and has the advantages of fulfilling a function of regenerating rainwater cycle in urban area. In this paper, we conducted some experiments on the effect of a permeable pavement on the thermal environment using the full-scale model constructed as actual carriageway. The results show that a rainwater storage facility of a permeable pavement produces evaporation from a pavement all day long which decreases the temperature of the pavement surface in comparison with a conventional asphalt pavement. We are planning to spread permeable pavements to prevent heat island with control of flood and underground water by making use of rainwater infiltration and cycle.