Analysis of Available Efficiency and Performance Data for Axial Flow Agricultural Ventilation Fans

Abstract.

The current ASABE Engineering Practice titled Guidelines for Selection of Energy Efficient Agricultural Ventilation Fans (ASAE EP566.2, ASABE, 2012) provides criteria for selection of energy efficient fans (VER-0.10 = cfm/W at ΔP = 0.10 in of water) and an index to evaluate the flatness of the fan curve (Airflow Ratio). The current engineering practice does not include selection recommendations for small fans (less than 18 inches in diameter), and many large diameter fans that are currently available. In addition, no discussion or reference is provided in the engineering practice to explain the basis for the current recommendations. A statistical analysis was performed using all of the axial flow fan data available (8 to 61 inches in diameter) for the airflow rate (Q-0.10), efficiency (VER-0.10), and airflow ratio (AFR). Comparisons were made to determine the impact of the use of discharge cones on Q-0.10, VER-0.10, and AFR. Use of a discharge cone significantly increased airflow for fans with a diameter of 10 in or larger and significantly improved efficiency for fans with diameters of 16 in and larger. Discharge cones did not provide a consistent improvement in AFR. Instead, AFR was found to correlate negatively with respect to increased fan diameter, and the negative correlation was strongest for fans with discharge cones (R = - 0.822). The results, from the analysis and pooled standard deviations of fan diameter groups were used to develop recommendations for fan selection based on VER-0.10 and AFR, and are provided in Tables 6 and 7.