International Research Journal of Advanced Engineering and Science ISSN (Online): 2455-9024 316 Hauna Ansar, Ajith Kumar Arumugham-Achari, and Jobin Johnson, ―Parametric study on the effect of a domestic wind catcher-solar chimney system for arid regions,‖ International Research Journal of Advanced Engineering and Science, Volume 2, Issue 2, pp. 316-322, 2017. Parametric Study on the Effect of a Domestic Wind Catcher-Solar Chimney System for Arid Regions Hauna Ansar 1 , Ajith Kumar Arumugham-Achari 2 , Jobin Johnson 3 1, 3 Department of Civil Engineering, Ilahiya College of Engineering and Technology, Muvattupuzha, India-686673 2 Department of Mechanical Engineering, Rajagiri School of Engineering and Technology, Ernakulam, India-682039 Abstract— To reduce dependence on non renewable energy resources for domestic cooling systems, and thereby reducing global warming, one can think of adopting passive cooling systems in combination with one another. Wind towers or wind catchers are stand alone systems widely used in hot, hot dry and (or) hot humid climates. These tall towers installed on the roof-tops capture wind for cooling the interior dwelling spaces. On the other hand, a solar chimney is a natural way of improving ventilation by virtue of thermal buoyancy effects on air. Within the regions of a room where the circulatory wind speed is low, a solar chimney can be installed in combination with a wind catcher in order to improve the efficiency of the system. We have performed various simulations on such a combinatorial windcatcher-solar chimney system for a closed dwelling space (no windows or other infiltration regions), in order to understand the parametric effects (i.e., dependence on incident (solar) heat flux, E on absorber; ambient wind speed, U ∞ and width of air gap in chimney, e) of such a system on the convective air current within the dwelling space. It became evident that substantial air motion can be attained within the closed region with such a combination. The solar chimney in such a system is found to be most effective (incremental improvement in air current) for moderate heat flux on the absorber and lower ambient air speeds (almost 60% increase in room inlet air velocity is observed for such a system with E = 500 W/m 2 , U ∞ =3m/s), while at higher wind ambient wind velocities (U ∞ =5m/s), the main contribution for air current within the room is due to the windcatcher (an increase of nearly 5 times when ambient air speed changes from 1m/s to 5m/s with E = 500 W/m 2 ). Also, a change in windcatcher geometry may not always adversely affect the room air entry velocities if proper blending and smoothing of possible corners and edges are provided. However, frictional losses and thus reduction in flow velocity within the windcatcher cannot be completely avoided since the sudden bends are deliberately provided inorder to settle dust and sand particles carried by dry air in arid geographical regions where such systems are in use. A test case of such a combinatorial system applied for specific geographical location (Jaipur, Rajastan) is also presented. Keywords— Passive cooling systems, solar chimney, wind catcher, solar irradiation, solar calculator, CFD. I. INTRODUCTION Passive cooling systems for dwelling spaces can reduce the consumption of non-renewable natural resources, thereby effectively reduce global warming and check the dependence on fossil fuels. Wind towers, also called as ‗wind catchers‘, are used for passive ventilation and cooling of buildings in the hot and arid regions around the world. These tall towers provided with several vents to capture wind for cooling the interior spaces and installed on the roof tops of buildings, are particularly popular in Iran and other Arab countries. Such wind catchers can have different shapes and structures depending on the geographical location, and they can save a lot of electrical energy in providing thermal comfort during the hot months of a year, while ensuring sustainability. The wind catcher openings are usually positioned facing the wind direction based on the geographical location. Knowledge of the wind flow pattern for a specific region can be of use here, while additional wind towers can be installed in several positions if the wind is accessible from several directions. Some designs for wind catchers even involve rotatable structure to face the direction of the maximum wind speed. Thus, windcatchers admit ambient air from outside and channel them into the dwelling space of a building, before which the dust (or sand) carried along is allowed to settle in a mid chamber. Hence due to these unavoidable frictional effects, the velocity of air entering the room will be much lower than the windy ambient air conditions. Some designs for windcatcher allow the air to pass through narrow sections, thereby increasing air velocity in accordance with Bernoulli‘s principle. This in turn can improve convective heat transfer and result in effective cooling. Some windcatchers attempt to improve the relative humidity of admitted air by passing it over water reservoirs within the room. Thus the air entering the dwelling space will be much cooler in comparison. Usually mud walls for partition and replenishable ponds as water sources are incorporated in a wind catcher design, as improvements over standard design. A solar chimney works on the principle of natural convection by virtue of thermal buoyancy of a heated air column. Such a mechanism can improve natural ventilation in the house. Usually a solar chimney consists of a glazing surface (also called the ‗collector‘) made of glass which transmits solar radiation and traps thermal energy, a solar radiation ‗absorber plate‘ (painted black, or coated HDPE on one side and insulated on the other) which reradiates heat energy into the air column within, and a vertical hollow shaft through which the heated gases move up. During the day, as the chimney and enclosed air are heated by solar energy, the resulting updraft in the chimney creates suction at the bottom of the chimney. This suction can mobilize air in the room, thereby ventilating the house. Generally, there are a number of studies separately carried out in the installation of different types and shapes of wind catchers and solar chimneys for various types of buildings. We initially carried out a review of the past research works conducted by various researchers in the field of installation of wind catchers and solar chimneys in the buildings. Bahadori is a pioneer in research on wind towers, and has worked on wind