The heat transfer characteristics of industrial air-cooled heat exchangers (ACHEs) are dependent on the ability of the fan system to deliver sufficient cooling air. However, under normal operating conditions, variable flow direction and strength often subject peripheral fans to distorted inlet conditions with an attendant reduction in overall volumetric flow rate and cooling capacity. In this paper, a design methodology for single-rotor axial flow fans, appropriate for use in large industrial ACHE’s is presented. The primary motivation for this work was to address the issues of robust off-design performance, in particular, distorted inlet flow tolerance. Using this methodology, two 8-bladed prototype fans (B1 and B2) were designed, built and tested in accordance with BS 848 (Type A) standards. The two B-fans have a hub-tip ratio of xh = 0.4 and employ the Clark Y and NASA LS airfoil profiles respectively. Measured performance characteristics were compared to commercial fan designs (V-, DL- and L-fan) used in existing ACHEs. Results indicate that the B-fans have a higher design point operating efficiency. The B-fans also show a steeper fan static pressure rise characteristic compared to the commercial fans, except for the DL-fan, implying a greater tolerance to pressure fluctuations caused by distorted inflows.

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