Small urban water bodies, like ponds or canals, are often assumed to cool their surroundings during hot periods, when water bodies remain cooler than air during daytime. However, during the night they may be warmer. Sufficient fetch is required for thermal effects to reach a height of 1–2 m, relevant for humans. In the ‘Really cooling water bodies in cities’ (REALCOOL) project thermal effects of typical Dutch urban water bodies were explored, using ENVI-met 4.1.3. This model version enables users to specify intensity of turbulent mixing and light absorption of the water, offering improved water temperature simulations. Local thermal effects near individual water bodies were assessed as differences in air temperature and Physiological Equivalent Temperature (PET). The simulations suggest that local thermal effects of small water bodies can be considered negligible in design practice. Afternoon air temperatures in surrounding spaces were reduced by typically 0.2 °C and the maximum cooling effect was 0.6 °C. Typical PET reduction was 0.6 °C, with a maximum of 1.9 °C. Night-time warming effects are even smaller. However, the immediate surroundings of small water bodies can become cooler by means of shading from trees, fountains or water mists, and natural ventilation. Such interventions induce favorable changes in daytime PET.
This paper presents five design prototypes for cool urban water environments developed in the 'Really cooling water bodies in cities' (REALCOOL) project. The REALCOOL prototypes address an urgent need: urban water bodies, such as ponds or canals, are often assumed to cool down their surroundings during days with heat stress, whereas recent research shows that this is not always the case and that urban water bodies may actually have warming effects too. There are, however, indications that shading, vaporising water, and proper ventilation can keep water bodies and their surroundings cooler. Yet, it is necessary to explore how these strategies can be optimally combined and how the resulting design guidelines can be communicated to design professionals. The REALCOOL prototypes communicate the spatial layout and biometeorological effects of such combinations and assist design decisions dealing with urban water environments. The micrometeorological simulations with Envimet showed that the prototypes led to local reductions on daytime PET from 1 °C to 7 °C, upon introducing shade. Water mist and fountains were also cooling solutions. The important role of ventilation was confirmed. The paper discusses and concludes about the use of the prototypes as tools for urban design practice.
Turbine blade cooling has been a topic of significant interest, as increasing turbine entry temperatures result in higher cooling requirements. The present numerical method divides the blade into a finite number of elements in the span and peripheral directions and solves the heat transfer fundamental equations for convection and conduction in both directions. As inputs, the span and chord gas temperature and heat transfer coefficient distributions are required. The results include high resolution temperature prediction for the blade and coolant, at all span and chord positions. The advantages of the method include the capturing of blade temperature variation in all directions, while considering the thermal diffusion due to conduction. Mach number effects to the resulted blade and coolant temperature are highlighted, as local distribution of the gas static temperature can have a dominant role. The effect of averaging the input parameters to the predicted blade temperature is discussed and finally, different values for the material conductivity are simulated and the results are analysed.
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