An experimental investigation of combined convective heat transfer from a smooth, isothermal vertical cylinder to a surrounding gas medium is described. The study was motivated by the desire to predict the convective heat loss from the 10-MWe pilot plant solar receiver in Barstow, California. Hence emphasis is placed on the supercritical (Reynolds number Re greater than 105, turbulent (Rayleigh number RaL greater than 109) regime. The influences of the Reynolds number, the Rayleigh number, the Richardson number, and Tw/T—the ratio of the surface temperature, Tw to the ambient air temperature T—are deduced. Large ranges of these dimensionless parameters are covered with a single model by using a variable ambient temperature, cryogenic wind tunnel over the temperature range 80 K ≤ T ≤ 300 K. The cryogenic facility also enables the simultaneous generation of large Rayleigh numbers and large Reynolds numbers.

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