Performance testing of a large, free-blowing propeller and a method for measuring flow rate

Performance of a large, free-blowing propeller of 4.3 m in diameter, known as a breeze ventilator, was evaluated in a test hall using air velocity field measurements under the ventilator, including velocity distributions in the near floor region. A force transducer was installed to measure the vertical force perpendicular to the propeller disc. The force was then used to calculate the airflow rate. The method of determining airflow rate based on the measured force is described and its application to the breeze ventilator presented and validated using velocity traversing. Power consumption and velocity measurements are presented. The average velocity in the downward direction 1 m below the propeller was 3.17 m s−1, and the average velocities in the horizontal direction 1.11 m s−1. The velocity-based airflow rate was 2.7% lower than the force-based measurement. Velocities were measured using two perpendicular cross-sections. One is referred to as the “gate-office” and another is referred to as the “wall-column” cross-section. The total velocity in the animal zone in the gate-office cross-section was 2.48 m s−1 (100%) at 10 V control signal falling to 2.10 m s−1 (85%) at 8 V and 1.77 m s−1 (71%) at 6 V. In the wall-column cross-section the velocities were lower at 1.76 m s−1 (100%), 1.47 m s−1 (84%) and 1.18 m s−1 (67%), respectively. Asymmetry in the profiles from the two sections may have been caused by the limited test space available.