Session: 10-01 Experimental Aerodynamics of Fans

Submission Number: 175241

Experimental Study on the Impact of Hub Configuration on the Performance of an Air-Cooled Condenser Fan 

Dry cooling technologies have been integrated in power plants in arid and semi-arid countries over the last few decades, as a measure to ensure sustainable water usage. More recently, countries with abundant water resources have also started to opt for the installation of dry cooling systems, with such decisions being motivated by long-term water conservation goals. Air-cooled condensers (ACCs) are a popular dry cooling technology option, which operate by forcing or drawing ambient air across heat exchanger banks using a multitude of large axial flow fans. In South Africa, the national utility operates four large thermal power plants with ACCs. Combined, these plants utilise 1200 ACC fans of 9-10 m diameter, each drawing 200-280 kW of power. Given the scale and continuous operation profile of these fans, optimal fan performance is of key importance and even minor efficiency improvements will have major benefits in terms of overall auxiliary power consumption and plant efficiency.

Secondary flow losses at the hub and tip of axial flow fans play a major role in their performance. A number of research studies have focussed on reducing tip losses on axial flow fans, but very few have considered their hub losses [1-4].

ACC fans are often analysed with smooth, rounded hubs to present best-case fan performance. However, rounded hubs raise fan manufacturing costs and are often impractical due to weight and space limitations at the full-scale fan’s size and installation position within the ACC. The intention of our work is therefore to assess the influence of hub configuration on ACC fan performance.

This study performs an experimental investigation into the effect of different hub configurations on the performance of a scale ACC fan. Five different hub configurations are designed, manufactured and individually tested by integrating the hub onto the scale fan. The five hub configurations considered are a disk hub, square hubs of small and large thickness, an elliptical hub, and a rounded hub. Fan performance with each hub configuration is compared to the other configurations.

Results reveal improved fan performance with a square hub compared to the disk hub, with differences between the two square hub configurations being within experimental uncertainty. As expected, rounded hubs perform best. Surprisingly, virtually identical fan performance is observed with an elliptical hub compared to a rounded hub across the complete range of flow rates tested. This finding indicates that implementing elliptical hubs in full-scale ACC fans may offer performance enhancements over conventional disk or square hub designs, while mitigating the spatial and economic constraints typically associated with rounded hub configurations.

 

References

[1]    Jang, C.M., Choi, S.M., and Kim, K.Y. (2008). “Effects of Inflow Distortion due to Hub Cap’s Shape on the Performance of Axial Flow Fan,” Journal of Fluid Science and Technology, 3(5), pp.598–609.

[2]    Wilkinson, M.B., van der Spuy, S.J., and von Backström, T.W. (2018). “Performance Testing of an Axial Flow Fan Designed for Air-Cooled Heat Exchanger Applications,” Proceedings of the ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, 1: Aircraft Engine; Fans and Blowers; Marine. Oslo, Norway. V001T09A005.

[3]    Jung, J.H. and Joo, W.G. (2019). “The effect of the entrance hub geometry on the efficiency in an axial flow fan,” International Journal of Refrigeration, 101, pp.90–97.

[4]     Meiring, Z. (2020). The effect of hub configuration on the performance of an air cooled steam condenser fan. Master’s thesis. Stellenbosch University.

Presenting Author: Sybrand J. Van Der Spuy Stellenbosch University

Presenting Author Biography: After spending a number of years working in industry, Prof Johan van der Spuy is currently the head of department at Mechanical and Mechatronic Engineering at Stellenbosch University in South Africa. He has a keen interest in turbomachinery, especially axial flow fans, and most of his research attention over his academic career has focused on this topic. He is looking forward to sharing this work with you.

Authors:

Johannes P. Pretorius Stellenbosch University
Sybrand J. Van Der Spuy Stellenbosch University
Mogammad Z. Mustapha Stellenbosch University