A. De Lieto Vollaro

Analysis of thermal field within an urban canyon with variable thermophysical characteristics of the building's walls

In a typical urban configuration, a microclimatic analysis has been carried out. Using a CFD method, a N-S oriented urban street canyon, with a given H/W ratio, has been examined. The standard k-e turbulence model has been used to simulate a three-dimensional flow field and to calculate the thermo-fluid dynamics parameters that characterize the street canyon. In this study has been analyzed the thermal flow field when the walls of the building change the properties of solar radiation absorption, in particular for α=0.2 and α=0.8. Solar radiation considered is that of 21/07 in Milan in two different hours: at 11:00 a.m. and at 02:00 p.m. The study shows the importance of the thermophysical properties of a wall, in the development of the thermal field and flow field. This is a very important topic, in terms of improvement of wellbeing and the quality of the air within the cities, through the choice of materials and colors of the facades of buildings.

AN EXPERIMENT OF FIRE RISKS IN TUNNELS: AN APPLICATION OF THE NUMERICAL ANALYSIS

The paper assesses, through numerical analysis, the thermofluidynamic condition in underground railway and road tunnels following a fire. The purpose was to implement a mathematical model that could be used in the future to identify a security indicator associated with every tunnel. The mathematical model developed is capable of simulating fires of greater dimensions in which the thermal field and the temperature reach the limit value of the stability of the structures. An attempt was made to reproduce the natural ventilation conditions present within the tunnel and special attention was given to the discretitation grid to which an independent solution was obtained.

Turbulent Air Flow Characteristics in a Ventilated Hospital Railway Coach

Abstract The aim of this work is to investigate turbulent air flows, through measurements inside railway coaches employed for the transport of sick persons. In this kind of environment, assuring occupant comfort and eliminating potentially annoying draught is necessary for safeguarding patients inside the train. As it is known, air velocity is not uniform but, instead, it fluctuates. It is these fluctuations that are the origin of local discomfort. This can result in a draught, which is defined as a local undesired cooling of the body. Since draught is one of the most common causes of complaint in a ventilated or air-conditioned space, understanding the turbulent air flow in these spaces and the impact of this flow on the sensation of draught is very important. The characteristics of turbulent air flow have been investigated through experimental measurements inside a railway coach provided with stretchers. In particular, in order to characterise these air flows, some parameters have been used, including mean velocity, standard deviation of velocity, turbulence intensity, and energy spectrum, etc. These parameters have been introduced by making use of the statistical analysis of instantaneous velocity measurements performed at several points. These were taken to be representative of the whole space actually occupied. This analysis showed that micro-nozzle diffusers gave optimum comfort conditions for patients in this type of hospital train.