The paper investigates the flow through a representative tall solar chimney with seven sets of internal bracing wheels with radial spokes. The paper presents experimental data measured in a 0.63 m diameter laboratory scale chimney model with and without bracing wheels. A fan at one end of the chimney model either sucked or blew the flow through it. The measured friction pressure drop was higher than theoretical values for smooth walls, and swirling, blown flow increased it by another 12%. The seven bracing wheels, each had twelve spokes, each spoke consisting of a pair of rectangular section bars, caused order of magnitude larger pressure drops than wall friction. For the sucked-through flow the forced, swirling, disturbed flow increased the pressure drop by up to 36%. Bracing wheels also increased the exit kinetic energy coefficient to 1.26 with the last wheel at the chimney exit. This effect could in combination with the bracing wheel drag reduce flow through the chimney. Designers of large chimneys should take care to minimise the number of bracing wheels, and possibly to streamline spoke sections. If possible, the top bracing wheel should be far enough from the exit for the flow to reattach to the wall after passing over the spoke attachment rim at the wall.

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