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Evaluation of design criteria for squirrel-cage fans used in public transport HVAC systems

This article completes a thorough review of the leading squirrel-cage fans, currently used for HVAC urban transport units, in terms of geometry and both aerodynamic and noise performance. Based on a twin-impeller, forward-curved centrifugal configuration, benchmarking with up to 15 different commercial units from several manufacturers has been carried out in this study, ranging the most significant geometrical and operational parameters for comparison. Experimental data concerning best efficiency points, overall efficiency range, noise generation, and performance have been obtained in a test facility built according to standardized industrial normative. The analysis of the obtained results is applied to select the best alternatives among those analyzed, focusing on energy efficiency and minimum noise generation criteria. In this way, the most important design criteria are established in order to get more efficient and less noisy ventilation systems.