FUNNELLING WINDOW: EXPERIMENTAL STUDY OF VENTILATION PERFORMANCE

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1 FUNNELLING WINDOW: EXPERIMENTAL STUDY OF VENTILATION PERFORMANCE Adolfo Gomez-Amador - Universidad de Colima Marcos Gonzalez-Trevizo - Universidad Michoacana de San Nicolas de Hidalgo Gonzalo Bojorquez-Morales - Universidad Autonoma de Baja California Jesus Komaba Quezada - Instituto Tecnologico de Chihuahua II José Francisco Armendariz Lopez Funnelling windows at the experimental setup. WHICH ARE YOUR ARCHITECTURAL (R)SOLUTIONS TO THE SOCIAL, ENVIRONMENTAL AND ECONOMIC CHALLENGES OF TODAY? Research Summary In order to improve the conditions of habitability in architectural spaces, especially in state-subsidized housing, devices with a low economic cost and low power consumption are recently studied. Under conditions of sub-humid warm climate; as the existing ones in Colima city (19º15 N; 103º44 W and 450m a.s.l.), the best passive design strategy to avoid electrical air conditioning is the natural ventilation. Due to this, there are some expectations to improve thermal comfort conditions in inhabited spaces through the use of design patterns in facade window that increases wind speed based on Venturi effect. This research reports on the operation of three devices with different design configurations to increase the wind speed, based on different inlet-outlet size ratio in the window. The cooling effect of the natural ventilation was estimated with the Szokolay s model dt=6vxv2. The study period was carried out from February to March, since this is the season when prevailing wind direction remains perpendicular to test modules where devices were installed. When air inlet reduction were 25%, 50% and 75% regarding the outlet size, the wind speed increases from 1.06 m/s to 1.33 m/s (25%), from 0.94 m/s to 1.28 m/s (37%) and from 0.90 m/s to 1.40 m/s (56%). This represents a potential decrease in temperature of about 0.28 C, 1.29 C y 1.86 C respectively, in compliance with Szokolay and mean speed values recorded in the inlet side of the window. Improving performance KEYWORDS: Natural Ventilation, Venturi effect, Window, Passive design. 205

2 FUNNELLING WINDOW: EXPERIMENTAL STUDY OF VENTILATION PERFORMANCE Fig 1: Funnelling windows at the experimental setup. WHICH ARE YOUR ARCHITECTURAL (R)SOLUTIONS TO THE SOCIAL, ENVIRONMENTAL AND ECONOMIC CHALLENGES OF TODAY? Research summary In order to improve the conditions of habitability in architectural spaces, especially in state-subsidized housing, devices with a low economic cost and low power consumption are recently studied. Under conditions of sub-humid warm climate; as the existing ones in Colima city (19º15'N; 103º44'W and 450m a.s.l.), the best passive design strategy to avoid electrical air conditioning is the natural ventilation. Due to this, there are some expectations to improve thermal comfort conditions in inhabited spaces through the use of design patterns in facade window that increases wind speed based on Venturi effect. This research reports on the operation of three devices with different design configurations to increase the wind speed, based on different inlet-outlet size ratio in the window. The cooling effect of the natural ventilation was estimated with the Szokolay s model dt=6vxv2. The study period was carried out from February to March, since this is the season when prevailing wind direction remains perpendicular to test modules where devices were installed. When air inlet reduction were 25%, 50% and 75% regarding the outlet size, the wind speed increases from 1.06 m/s to 1.33 m/s (25%), from 0.94 m/s to 1.28 m/s (37%) and from 0.90 m/s to 1.40 m/s (56%). This represents a potential decrease in temperature of about 0.28 C, 1.29 C y 1.86 C respectively, in compliance with Szokolay and mean speed values recorded in the inlet side of the window. Keywords: Natural Ventilation, Venturi effect, Window, Passive design.

3 1. Introduction Nowadays, there is an increasing concern for environmental issues, depletion of energy resources and the consequent difficulty for their supply. Therefore, devices that favor reducing energy consumption are indispensable in building design. The window, as architectural element is an opening for environmental control with multiple functions related to the indooroutdoor conditions. Despite the fact that building codes demand a wall-window size ratio, they not always possess a bioclimatic purpose. However, these openings have specific traits in each building and important differences in relation to the occupants. In Colima, sub-humid warm climate is predominant according to Köppen-Garcia s climate classification system, due to this, it is convenient to induce air movement, since it will improve thermal comfort of inhabitants by reducing humidity and cooling indoor areas. Climate conditions conform high and low air movement seasons; for this reason, it is essential to control indoor ventilation rates during throughout different strategies. This could be increased with the adequate design of windows based on Venturi effect; as well as changing prevailing wind direction to fulfill building comfort requirements. Fig 2: Colima: geographical location. 2. Research objectives This experimental study analyses the operation of three devices with different design configurations to increase the wind speed, based on different inlet-outlet size ratio on the window. Within the framework studies, Rivero (1988) considered important to take into consideration dimensional features of outside walls since these can have either a positive or a negative influence in capturing air during the times of high and low air movement. Gomez Amador, et al (2006) demonstrated that a window registers different air movement speeds at different heights, since warmer air will move toward the top of the opening, while García (2007), for his part, analysed ventilation performance with different materials used to build triangular shape lattices. The results showed that the lattices of adobe (hollow space 40x20 cms), decreased only 4% the wind speed at speeds of 2.13 m/s and by about 64% when speeds of 4.45 m/s were reached. Olgyay (1963) pointed out in his initial studies that it was better to introduce wind at 90 from the exposed surface (perpendicular). Since speed (V) depends on the relationship between inward and outward areas (r) and size of the inward opening (A); as far as the flow (Q) and the angle of incidence are constant as shown equation 1. V=Q/r*A*SenƟ (1) Szokolay (1990) proposed to use wind to offset higher temperature with an equation in order to evaluate ventilation efficiency at the moment of being induced to inhabitant spaces. DT=6V-V 2 (2) The equation above, calculates the equivalent reduction (DT) from the outdoor air temperature expressed in deegres Celcius using the wind speed (V) in metres per second. This is useful to estimate the wind speed required to improve thermal confort for people in a natural surrounding in indoor spaces where cross ventilation is inhibited by building common designs.

4 In a previous study, Gómez and Armendáriz (2008) analyzed the effect of increasing the ventilation rate by modifying the window frame planes in a house located in the city of Colima. In this study, the air outlet size was reduced by about 50% changing the inclinations of frame planes and with this, wind mean speed was increased by 40%. 3. Method In order to test the potential of a device which takes advantage of the prevailing wind conditions in seasons with low air movement, an experimental scenario was arranged using three modules in the testing field of the University of Colima. The design features of them simulates a building facade oriented due to northwest to capture prevailing wind gusts. Test modules are 1.22 m, 1.22 m and 2.54 m (length depth height). They have a front opening, it is 1.00 m by 1.10 m to provide the necessary air inlet to enable an inhibited crossventilation state and were built with materials traditionally used in Colima, clay brick parapet walls with a continuos reinforced concrete lintel and cement boards wich conform the three different wind concentrator configurations of each window. (Fig. 2). The device design consisted in different geometric features to conform a wind concentraror within the window opening; wind concentrator is defined as the plane with a 45 inclination angle fixed vertically or horizontally to reduce the air outlet section size of the window in up to 25%. As seen in figure 3, a different setup was used with its corresponding inlet-outlet ratio reduction ; at the beginning with one concentrator plane (25% size reduction), then with two concentrators (50% size reduction) up to the final version which consist on a complete funneling window that employs four concentrator surfaces (75% size reduction). Fig 3: Test module basic frame. Fig 4: Different window configurations. In this region, the annual prevailing winds come from the southeast and southwest. However, the study period was conducted during the months of February, March and the early dys of April, when the prevailing winds come from the north and therefore exert a direct impact on the experimental scenario compared to other seasons.

5 3.1 Data logging equipment The instruments used to capture and record weather information detect wind and temperature variations with a high degree of sensitivity. These were located in each air outlet plane geometric centre respectively, to see the ventilation changes generated by the window configuration proposed. The Skywatch unidirectional propeller anemometer-thermometer with dry-bulb temperature DBT sensor range from -40 C to 80 C, speed wind of 0.0~40.0 m/s, ±3.0% accuracy was used. significant potential of apparent temperature of 1.29 C. Finally, in the third configuration of the funnelling window, where the window has four planes and the reduction was 75%, the mean wind speed recorded achieved was 0.90 m/s in the inlet while 1.40 m/s at the outlet, which represents an average increase of 37% and a significant potential of apparent temperature of 1.86 C. As expected, the more the inlet-outlet reduction ratio increases, the more the wind speed recorded at the outlet point was higher. As seen in figure 6, the linear behaviour in wind speed is constant in compliance with the acceleration due to the opening reductions in window designs. Fig 5: Data logging equipment: anemometer 4. Results In the first test module, where the lowest inletoutlet reduction ratio (25%) was arranged in the window through the use of one concentrator plane, the mean wind speed recorded achieved was 1.06 m/s in the inlet and 1.33 m/s at the outlet point, which represents a temperature decreasing of 0.28 C according to Szokolay s equation. In the second configuration, where the window was modified using two planes and the reduction was 50%, the mean wind speed recorded achieved was 0.94 m/s in the inlet and 1.28 m/s at the outlet, which means that increasing on mean wind speed of 37% and a Fig 6: Data logging equipment: anemometer 5. Conclusions To identify the behavior of an air-concentrating window is more complex than just recording wind velocity. Any measurement system applied to a building will show limitations when trying to profile the behavior of the window, since wind direction and wind velocity are dynamic. However, considering the variation of the angle of wind incidence during the velocity recording process and having into account the assessment of velocity records with the calculated ones, the window behavior is favourable for a sensitive increment on indoor wind velocity. It is convenient to do further research that allow to estimate the behaviour of this kind of devices when wind

6 speeds are higher or when different uptaking angles of prevail winds are involved. 6. References Fuentes Freixanet, V. (2004). Natural ventilation: basic calculations for architecture. México, D.F.: Metropolitan Autonomous University. (in spanish) García Solórzano, L. A. (2007). The lattice in subhumid tropic traditional building techniques. The jarana as environmental control device. Master's degree thesis, University of Colima, Faculty of architecture and design. (in spanish) Gómez Amador, A., Alcántara Lomelí, A., y Alvarado Cabral, E. A. (2006). Window in sub-humid tropic building tradition. Palapa, 1, Second period (in spanish) Gómez-Amador, A., & Armendáriz-López, F. (2008). Ventilation performance in a funneling window. 25th Conference on Passive and Low Energy Architecture, Dublin. University College Dublin. Olgyay, V. (1963). Design with climate. Princeton, New Jersey: Princeton University Press. Rivero, R. (1988). Architecture and climate: thermal natural conditioning for northern hemisphere. México: UNAM. (in spanish) Santamouris, M., (2006). Ventilation for Comfort and Cooling: The state of the art. En Santamouris, M., y Wouters P. (Eds.), Building ventilation: The state of the art. (pp. 221). London.: Earthscan James & James. Szokolay, S. (2004). Introduction to Architectural Science: the basis of sustainable design. Oxford: Pergamon. Szokolay, S. (1990). House design for overheated environments. Memoria I National congress for design and environment (pages ). Colima: University of Colima-Federal Electricity Commission. (in spanish).