Abstract
We analyzed theoretically and experimentally the performance of the 19 different ornamental caps of the individual chimneys located on the terrace of Palau Güell (Barcelona, Spain) designed by Antoni Gaudí. This set of chimney caps has wide range of external geometries and different number and shapes of openings. Models of the chimney caps were obtained using photogrammetry and 3D printing. Wind tunnel measurements of the pressure inside the stack pipe connected to the cap were performed for different external and stack flow velocities. Two distinct orientations of the external flow with respect to the chimneys were considered. We derived a simple theoretical model, based on the potential flow theory, to relate the non-dimensional pressure reduction in the stack (chimney draft) with the ratio between the external and stack flow velocities. It has been found that the behavior of the chimneys caps predicted by this model is in agreement with the measurements. It has been found that the performance of the chimneys depends mainly on the number of supports of the conical cover of the cap and it is essentially independent on the shape of the cap and on the number and geometry of the openings located on the cap. These conclusions obtained for this particular set of chimneys can be useful for the design of caps for ornamental or general use.
Highlights
IntroductionChimneys have been widely used to conduct combustion and flue gases and other contaminants from animal housing and domestic and industrial sources to the atmosphere
Chimneys have been widely used to conduct combustion and flue gases and other contaminants from animal housing and domestic and industrial sources to the atmosphere. They are an essential part of many natural ventilation systems [1, 2]. In these systems the outlet flow rate is governed by three effects: (1) the difference in air density between the inside and the outside of the building due to temperature and/or composition of the air, (2) the aerodynamic effects due to the wind flowing around the building and (3) the location and the geometry of the ventilation elements
Smoke released in the external flow revealed that the external flow mainly entered the chimney cap through the openings between the supports located in the pressure side and left the chimney together with the stack flow through the openings located in the wake side
Summary
Chimneys have been widely used to conduct combustion and flue gases and other contaminants from animal housing and domestic and industrial sources to the atmosphere. Wind tunnel measurements, using scale models, are convenient to evaluate the wind induced ventilation inside buildings [11,12,13] and the performance of individual ventilation elements under well controlled flow conditions [14,15,16] These experiments are relatively costly, they provide local reliable data using pressure and velocity probes and spatial flow information using Particle Image Velocimetry [17] and flow visualization techniques. Numerical simulations of the flow inside historic buildings and museums can be used to predict the airflow and its potential effects on the art works, as the temperature or humidity uniformity or the particle deposition rates. This information can be useful to help in the conservation management. Examples of application of CFD tools to predict airflows in heritage buildings and historical sites can be found in [21,22,23,24,25,26,27,28]
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