Temperature and velocity measurements on a diffuser for displacement ventilation with whole field methods.

In this study the instantaneous temperatures and velocities close to a diffuser for displacement ventilation have been recorded by using whole-field measuring techniques. The air temperatures were measured indirectly by the use of a low thermal mass screen in conjunction with infrared thermography. The measuring screen was mounted parallel to the airflow, acting as a target screen. By using the thermal images the size of the near zone was also calculated. To determine air movements a whole field method called particle streak velocimetry (PSV) was used. Images of tracks created by small, low-density particles, suspended in the air, were analysed using computerised image processing to obtain the velocities. The experiment took place in a climate chamber in which the wall and air temperatures were controlled. The diffuser was located in the centre of one of the walls. The tests were conducted for a supply flow of 15 l/s and a temperature difference between the inlet air and the room air of 4 °C and of 6 °C. This paper deals with the results obtained from the two whole-field measurement methods. The results show that the two whole-field measurement methods can be good tools for visualising and measuring air velocities and temperatures in rooms. These techniques could be used in the work of improving the indoor climate.