English

This study is a part of the Finnish contribution to the HYBVENT project (Annex 35 of IEA). Two 'hybrid' ventilation concepts designed for northern climates were evaluated for a 4300 m2 office building in Helsinki : one of them is low pressure mechanical exhaust with CO2-controlled air inlets ; the other uses mechanical air supply through coils and two parallel exhaust circuit with and without fan and heat recovery. They were compared with conventional systems in Finland (mechanical supply and exhaust with constant or variable air volume).

Experiments and calculations were operated to determine air flow distribution in a test room (9.9 m2) naturally ventilated through adjustable louvers overlooking outside. Air enters at the bottom (opening surgace 0.07 m2) and is exhausted at the top of the room (opening surface 0.12 m2). Air pressure and velocities across the opening allow to estimate wind pressure coefficients. Results show in particular the influence of wind on the internal air flow. Good agreement was found between measurements and calculations.

A two-dimensional particle image velocimetry (PIV) technique was used to measure velocity and turbulence of air flow around a heated manikin in a large room (volume about 80 m3). Measurements were operated in four horizontal and ten vertical planes. The article describes the PIV system and the type of results which were obtained.

Experimental results on the thermal conditions around a ventilated chair (with air supply openings in its base) are provided. They concern air velocities, temperatures and thermal comfort for a seated person. Results are commented compared to those obtained in a room with displacement ventilation with wall-mounted diffuser.

A thermal manikin with 16 independently heated sections has been used for measurements of thermal comfort with mixing and displacement ventilation. The thermal comfort is expressed at the location of the manikin as an equivalent homogeneous temperature (EHT).
Results lead to indications about the connection between EHT and the percentage of dissatisfied due to the vertical temperature gradient and draft rating.

Experimental results in a testing room with mixing ventilation were used to define two new ways of designing the inlet airflow in order to ensure comfort. The first way uses the assumption that air velocities are only a function of the Archimedes number, which provides curves showing air velocity in the occupied zone as function of inlet air temperature and velocity. The second way results from an analytical calculation of the penetration length of the air jet in the room and the distance where it enters the occupied zone.

Different geometries to simulate a person in an indoor environment numerical simulation have been evaluated with respect to local and global air flows, as well as convective heat transfer. Results show that the geometry of the computer simulated person influences only the local flow around it.

A simplified methodology for numerical simulation of air flows around and above ventilated chairs in a theater or auditorium has been developed. It uses a simplified method for describing the air diffuser geometry (N-point momentum model), a simplified turbulence model (zero-equation turbulence model) and an error pretreatment method. It has been applied to a room ventilated through air supply openings in the chair bases. Simulation results (air temperature and velocity distributions) show good agreement with experimental data.

A multizone air flows simulation code (IDA MAE) was used to evaluate a hybrid ventilation system (passive stack with assisting fans) in a Swedish school (9350 m2 - 20 classrooms), in the framework of the HYBVENT project (Annex 35 of IEA). Simulation was operated with 18 zones. Results show the sensitivity of air flows to changes in wind speed and direction.

Design process of buildings currently addresses indoor air quality through ventilation flow rates requirements. In some circumstances, this approach may be not sufficient and an alternative is to determine ventilation rates through contaminant-based design methods. The authors present several examples of such approach, especially using multizone modeling (CONTAMW model) in a two-story classroom/office building equipped with a CO2 demand-controlled ventilation.