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Development of a control algorithm to optimize airflow ratesthrough variable size windowsM.N. Assimakopoulos a,* , A. Tsangrassoulis a , G. Mihalakakou a ,M. Santamouris a , Serge Jaure ´ ba Group of Building Environmental Physics, Building Physics 5, University Campus, University of Athens, 15784 Athens, Greeceb ARCHI.M.E.D.E.S, Architecture Microclimat Energies Douces Europe et Sud, 120 av. Des Deux Ponts, Cazilhac, F-34 190 Ganges, FranceReceived 7 July 2001; received in revised form 10 August 2001; accepted 15 August 2001AbstractThe present paper aims in investigating, in a systematic way, using both experimental and theoretical tools, the potential of naturalventilation control techniques when applied to full scale buildings. Experiments have been carried out in outdoor test cell and differentconfigurations have been tested for two window types (bottom hung and sliding) under various meteorological conditions. Based on theexperimental results, specific modeling activities have been undertaken and theoretical methods for calculating airflow rates through theabove-mentioned windows have been developed. The theoretical predictions are compared with the corresponding experimental data and avery satisfactory agreement has been observed. Following the data analysis an algorithm was developed for the control of the naturalventilation. # 2002 Elsevier Science B.V. All rights reserved.Keywords: Natural ventilation; Dynamic facades1. IntroductionThe use of natural ventilation can contribute to reducesignificantly the total energy consumption of buildings.Specific studies have shown that application of naturalventilation techniques may decrease dramatically the cool-ing load of buildings and they may improve indoor comfortand air quality. In reality, the phenomenon of air flowthrough large openings is of a random nature because ofthe wind characteristics. The pressure difference across theopenings is defined as a function of inertia and buoyancyforces and mainly of thewind speed and direction, as well asof the temperature difference between indoor and outdoorenvironment. Thus, experiments aiming to investigate thenatureofthesephenomenashouldbetterbecarriedoutunderrealistic conditions. Also, modeling of the phenomenashould take into account, and may be coupled with, allmajor parameters defining the performance of the system.Dascalaki et al. [2] have presented a methodology to esti-mate the air flow through openings and this methodologywas extended in order to cover obstructed openings withvarious shading systems [3].2. Experimental setupA series of experiments have been carried out in aPASSYS test cell (Wouters and Wandaele [6]). In particular,the experiments aimed at evaluating processes related to theair flow through the openings under single side ventilationconfigurations.The PASSYS test cell is a fully equipped, two-zone,outdoor facility for thermal monitoring. The south facadeof the cell is removable and allows installation and testing ofspecific building components. Experiments were carried outin the ‘‘test room’’ while the door connecting it to the‘‘service room’’ was kept closed and sealed. The test roomhas a height of 2.72 m and a volume of 35 m 3 .The major parameters defining the thermal performanceof the test room, was constantly measured. The air tem-perature of the room was also measured by an array ofseven PT100 sensors. The arrangement of the sensors(marked by X) is illustrated in Fig. 1. Ambient air tem-perature data were provided from a standard meteorolo-gical station next to the test cell. All indoor and outdoortemperature sensors were accurately calibrated in order toachieve the highest possible accuracy regarding the tem-perature difference between the indoor and outdoor envir-onment.Energy and Buildings 34 (2002) 363–368* Corresponding author.E-mail address: masim@cc.uoa.gr (M.N. Assimakopoulos).0378-7788/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved.PII: S0378-7788(01)00116-5