Field study on pressure differential mechanisms under static and dynamic disturbances in non-isobaric building zones

Deviation of pressure differential from design under static conditions and delayed convergency of pressure fluctuation after dynamic disturbances are widely reported problems associated with pressure differential control in non-isobaric buildings. This study performed field measurements to investigate the pressure differential mechanisms under static and dynamic disturbance in several non-isobaric pharmaceutical factory zones served by either constant air volume or variable air volume (VAV) ventilation systems. Four typical dynamic disturbances including door motion (the process of door opening or closing for 1 s, 2 s, and 3 s), personnel entry and exit, indoor personnel movement, and continuous door opening were considered. The results showed that static pressure differentials deviated significantly from the design requirements, and some of the pressure differentials were even reversed in direction. Depending on the location of the sensor, it took 3–13 s and 3–10 s to detect and stabilize the pressure differential within the zone during door openings and door closings, respectively. Personnel entry and exit induced inevitable brief but intense disturbances in the pressure differential evolution. Ceiling-mounted pressure sensors could not detect fluctuations caused by indoor personnel movement, thus preventing erroneous responses from proportional-integral-derivative (PID)-based VAV valves. However, the VAV valve exhibited slow response and ineffectiveness during door motion and continuous door opening due to unsuitable PID parameters and low-accuracy pressure sensors. To improve the control strategy, exponential models based on the pressure differential evolution during door motion were proposed. The findings provide useful information for real-time and accurate pressure differential monitoring and for developing effective VAV ventilation strategies.