DEVELOPMENT OF A NEW CALIBRATION WIND TUNNEL WITHIN LOW AIR VELOCITY RANGE : 0.05 UP TO 2 m / s
Isabelle Care
Abstract:
Industrial needs for measurements of low air velocity can be classified in three categories : - Evaluation of comfort in private or collective building (houses, offices, hospitals, schools, stores, libraries, …) and in vehicles (cars, trucks, trains, planes, …). Actually, the fundamental parameters to qualify comfort are air velocity, temperature and humidity. - Control of products quality in industrial processes (clean rooms for microelectronics industries, climatic chambers for aging tests, drying chambers for food industries, …) - Control of equipment to ensure safety of people in hospitals, in pharmaceutical industries, in painting processes, … These applications require a minimum uncertainty in air velocity measurements which lead to the following evolution in air velocity metrology : - A calibration facility which ensure the smallest calibration uncertainty as possible : The reduction of this calibration uncertainty will lead to reduce the global measurement uncertainty of process and allow to qualify industrial applications conforming to European and American standards such as EN ISO Standard 7730 « Specifications for thermal comfort conditions », 1995), ASHRAE Standard 55 (« Thermal environmental conditions for human occupancy », 1992), Federal Standard 209E (« Airborne particulate cleanliness in clean rooms and clean zones ») - A calibration facility which can work at different temperatures, different relative humidities and with different direction of flow. Currently, anemometers calibrations are carried out at ambient conditions (around atmospheric pressure, 20°C and ambient humidity) in a horizontal flow. Depending on their working principle, anemometers can be very sensitive to the air flow temperature in which they are supposed to measure velocity, especially at low velocity. As working laws are complex, it is often difficult to take into account the real temperature influence on sensors in view to correct the measured value. It would be far more easy to be able to calibrate anemometers at their working temperature.
