Modeling of urban canyon: analytical and experimental remarks

The urban climate of high-density areas is often affected by an increase of the air temperature known as Urban Heat Island (UHI) phenomenon. UHI is strongly influenced by the solar reflectance of conventional materials used for building envelope and urban coatings, i.e. streets and square pavings. The present work proposes an original method to predict the temperature of both facades and local air mass on urban scenarios. The effect of changes on coatings may also be estimated. The proposed method is based on an Experimental Facility (EF) and a Theoretical Model (TM) which are jointly taken into account for UHI predictions. EF is located at the University of Perugia which is composed of two separate metal rails incorporating several insulating frames, resembling a urban canyon, positioned at different mutual height/distance ratios (i.e. H/D = 0.5, 1.0, 2.0). Each frame can be equipped with particular reflective films (e.g. cool roofs coatings) in order to assess variation of radiative exchanges as a function of geometry, meteorological conditions, and radiative properties of walls. The monitoring system is equipped with temperature sensors, a pyranometer and an anemometer. A weather station is located nearby. EF may be used directly to estimate UHI by a mechanical analogy which however introduces strong limitation on real scenario dimensions and operative conditions. By validating the TM via EF the range of real scenario may be studied and predicted is widely extended and the proposed method may be applied virtually for any case. The preliminary calibration of the methodology using measured data is also presented.