These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

With summers getting warmer and warmer every year, urban climate thermal management is getting critical in order to avoid extreme temperatures in urban city environments, which can lead to discomfort, health issues or even death, especially for elderly persons. During summer, ambient temperatures rise significantly, with solar radiation from the sun playing a major role in intensifying urban heat. This solar energy heats concrete buildings, asphalt roads, and even pedestrians, exacerbating the urban temperature. Infrastructures heat easily, due to their high solar radiation absorption coefficients. They cooldown however very slowly due to their high mass and specific heat. This can make the pavement temperatures go much higher than the ambient temperature and reach temperatures exceeding 70°C. These elevated surface temperatures will in turn increase the local air temperatures, leading to discomfort for humans. This study demonstrates how the urban climate can be predicted around buildings or urban environments over long durations. A CFD solver that simulates the wind and convection can be coupled to a thermal radiation/conduction simulation tool. The thermal tool is able to simulate the incoming solar from early mornings to evening, so with a moving sun, without using large simulation time or computational resources. Convection from CFD is imported at given times or linearly interpolated with respect to windspeed and direction, which then allows temperature predictions over days, months or even a year. It will be shown how certain design choices can influence local temperatures. An illustration of this is the application of solar reflective glass windows on buildings, so that the building does not absorb the incoming radiation. Other examples are the addition of trees in the streets. They create shadow and don'™t heat-up as much as concrete. Another one is the use of green roofs, which facilitate evaporation through plant transpiration, but also provide an insulation layer for the building. Such design changes lower the temperature in and around buildings, improve the comfort and reduce the energy demand that is required for active cooling systems like air conditioning.