cooling

Cooling ceilings are more and more proposed, in order to eliminate excess heat in office buildings without consuming much energy in air transport. On the other hand, piston ventilation is proposed to efficiently eliminate contaminants. These two systems may however interact and experiments were planned to look at these interactions. Measurements of the age of air and air change efficiency were performed, together with more classical temperature and air velocity measurements, on various ventilation systems installed in the test chamber of Sulzer Infra, in Winterthur.

This paper shows the extensive influence of humidity on comfort, cooling load and refrigeration capacity. Modern computer programs allow an effective consideration of humidity in systems.

The efficiency of removing excess heat by employing mixing ventilation is based on the properties of jets. Therefore the behaviour of jets in enclosures is important. A correct supply design is essential otherwise the jet will separate from theceiling and drop into the occupied zone. This will give rise to unacceptable high velocities. the basic properties of jets in ideal situations like an infinite space are well known. However, in a room the jet interacts with the room air and the room surfaces.

For thermal comfort and energy conservation reasons, displacement ventilation and radiative cooling systems are increasingly used. Simulation programs are generally not able to correctly simulate such systems because of their one node approach for the air temperature. A procedure for creating DOE-2 inputs to simulate both system types each alone or in combination - without program code change - was developed, based on a more detailed new TRNSYS-Type, and validated against existing experimental data sets.

A new ventilation and cooling system called OKOMAIR has been developed and investigated. The main idea is to separate carrying off cooling loads and providing fresh air to the occupants without mixing it with the return air. Return air is cooled by fan coil devices. The undiluted outside air is provided directly to the working zone and cooled by a cold waterstorage. This storage is charged by cool outside air during night. Use of the new system leads to high comfort for the occupants and reduces cooling energy.

For several years the technology of chilled ceilings has been a favourite issue among HVAC technicians and underwent a boom in the past few years. According to the survey of a German technical journal, on March the first 1993, a total of 308,490 m² of chilled ceilings had been installed in German buildings, out of which 69 per cent had been installed in new buildings and 31 per cent in modernized projects. Cooling ceiling systems are the ideal.application where high demands are placed on comfort requirements and where the energy loads are very high compared to material loads.

In urban non-residential buildings air-conditioning systems are generally required to achieve acceptable air quality. To reduce the energy demand of HVAC-plants free cooling is proposed. The present study deals with free cooling by outdoor air (untreated or additionally cooled by evaporation) during the night. Therefore a sufficient building mass (about 600 to 800 kg/m²) is necessary which stores the heat produced in daytime and which is cooled down at night. In most conventional non-residential buildings, however, the building mass is at about 400 to 600 kg/m².