20.1 Building DescriptionB u i l d i n g t y p e :Auditorium20.1.1 S i t e and l o c a t i o nB u i l d i n g A d d r e s s :Polytechnic AuditoriumC.so Duca degli Ahruszi n 2410129 TORINOITALY+9-11-5646666TorinoItalyThis enclosure is a university auditorium located in the Politecnico of Torino, one of the largest engineering school in ltaly. The room lies in a building structure built in the early fifties, and it has been recently equipped with a GOz-controlled mechanical ventilation plant (DCV system) in order to provide a satisfactory IAQ. This auditorium is one of the largest auditoria of the Polytechnic of Torino and it is widely employed during the first two-years classes. Sometimes it is also used as an exhibition hall for little concerts and shows. The enclosure was included in the annex 26 case-study buildings in order to verify analysis tools and measurement techniques. The auditorium was selected as annex 26 building especially to test CFD-calculations and to point out qualities of different measurement procedures used to evaluate ventilation plant performances. An experimental campaign was developed, mainly using tracer gas techniques. The measured parameters were compared with the predicted ones; the theoretical results were obtained using both commercial CFD codes and simplified engineering models.20.1.2 Building formDimensions of t h e enclosure: Description of building type The Auditorium has a capacity21.8 m x 16 m x 5.5 m of about 350 seats arranged along 17 rows divided in two groupsVolume: by a longitudinal main passage. The room has a stepwise floor1750 m3 sloping down from the main entry to the teachers desk. All themural boundary surfaces are made of brick. The ceiling is arrangedfollowing large steps and, with a small portion of the two lateralwalls, is the only boundary surface that is directly connected tothe outdoor. All the other walls divide the auditorium from otherconfined spaces such as corridors, other auditoria and technicalrooms. A total of ten windows, covered by heavy curtains, areplaced in the upper part of the two lateral walls.20.1.3 Building servicesDegree of Conditioning:heat and cool onlyHeat transfer medium:30 kWInternal temperature:W i n t e r S u m m e r20 OC variableInternal relative humidity:not controlledExternal Temperature:Fresh air supply ventilation rate:variable depending on COz content(10400 m3/h maximum nominal, design, value)Total air change ventilation rate:about 6 ach.T y p e of Ventilation The ventilation system is mechanical andit is a constant air flow rate with a COz-controlled recirculationrate (DCV system). During the winter time, when necessary, thesupply air is heated by means of hot water (80 OC); an enthalpieheat recovery unit allows some energy savings and also performs acertain degree of humidification of the inlet air. During the summertime the supply air is cooled by means of well-water, and, since itstemperature is constant at about 15 OC, the control of the thermohygrometric conditions of the air is limited in range. Two series offilters ensure a solid particle uptake.Additional details of ducted system The ventilation and airconditioning system is placed in a technical room below the auditorium; the air treatment is centralized. There are two fans, onefor the supply air and one for the exhaust air, that generates abalanced and constant volume flow rate . A system of conjugatedampers allows the adjustment of the recirculation rate. The recirculation control is based on the occupancy load, i. e. measuringthe COz content with a sensor located in the exhaust duct.Location of t h e supply and extract grilles The supply air isdistributed by means of 8 circular inlet grilles located about 1meterbelow the ceiling. These diffusersare of the variable geometry type,with 6 helicoidal blades generating a turbulent flow. The jet shape(i.e. penetration length, opening angle, swirl...) is set changingthe angle of attack of the blades; its regulation is based on thetemperature difference between the supply air and the exhaust air.The polluted air is exhausted by two grilles located in the lowerpart of the auditorium, sideways the teachers desk.Control strategy It is a simple single zone control system