59130 - Evaluation of the 24 Ft. Diameter Fan Performance in the Minwatercsp Large Cooling Systems Test Facility 

S.J. van der Spuy, J. Muiyser, L. Tieghi, G. Delibra, A. Corsini,

F.G. Louw, A. Zapke, C.J. Meyer, D.N.J. Els 

The MinWaterCSP project was defined with the aim of reducing the cooling water consumption of concentrating solar power (CSP) plants by 75 to 95%, relative to wet cooled power plants, and to improve plant efficiency by 2 to 3 % relative to current dry-cooled systems. Similar to current Air-Cooled Condensers (ACCs), the intention was for the cooling system to make use of large diameter axial flow fans to drive air through the heat exchangers, thereby condensing the process fluid. A part of the improvement in plant efficiency was to be achieved by designing an axial flow fan for application in low-pressure, high flowrate air-cooled or hybrid condensers.

A new axial flow fan, the M-fan, was developed and manufactured for the 24 ft diameter, full scale MinWaterCSP test facility, located at Stellenbosch University. To confirm the design performance of the M-fan, a 1.5 m diameter prototype was manufactured, and its performance was measured in a standard ISO 5801, Type A fan test facility. However, previous investigations have shown that the small-scale performance of such an axial flow fan may deviate from its full-scale performance by underpredicting the efficiency of the larger fan. The lay-out of the ISO test facility is also markedly different from that of a full-scale installation.

A full-scale, 24 ft diameter model of the M-fan was subsequently installed in the MinWaterCSP cooling system test facility. The test facility was equipped with an in-line torque arm and speed transducer to measure the power transferred to the fan rotor, as well as a set of rotating vane anemometers upstream of the fan rotor to measure the air volume flow rate passing through the fan. The fan pressure rise values could not be measured. The measured results were compared to those obtained on the 1.5 m diameter ISO 5801 test facility using the fan scaling laws. The comparison showed that the fan power values correlated within 7% to those of the small-scale fan, but at a 1° higher blade setting angle.   

To investigate the deviation in fan shaft power results further, a CFD analysis of the 24 ft diameter fan installation was performed. The purpose of the CFD analysis was to investigate the possible effect of the fan installation inside the cooling system test facility on the observed performance of the fan by comparing the predicted fan static pressure rise values from the CFD analysis to those measured on the 1.5 m ISO test facility. As such, the simulation made use of an actuator disc model to represent the effect of the fan. The results showed that the predicted results for fan static pressure rise of the installed 24 ft diameter fan correlated closely to those of the 1.5 m diameter fan but, once again, at a 1° higher blade setting angle. 

The study concludes by emphasising the need for further testing of the installed fan’s performance, possibly by incorporating fan blade pressure measurements.