VAV terminal units of air conditioning systems

This paper presents the VAV terminal units and their airflow measuring technologies currently applied from the perspective of energy conservation. The 1st generation VAV terminal units use the Pitot-array probe to measure the amplified velocity pressure of VAV terminal units and output the digital signal to the controller through the differential pressure transmitter, which results in a significant loss of fans’ energy consumption due to the high airflow velocity through the damper. The 2nd generation VAV terminal units directly output the digital signal to the controller using electronic devices such as the propeller airflow sensor. Because of its low airflow velocity through the damper, the fan’s energy consumption is significantly reduced compared to the 1st generation VAV terminal units. The 3rd generation VAV terminal units replace the damper of traditional VAV terminal units with a fan, which further reduces the fan’s energy consumption compared to the 2nd generation VAV terminal units.