Fluid Flow and Heat Transfer of Natural Convection around Heated Horizontal Square Cylinder in Water

Abstract

Natural convection around heated horizontal square cylinders placed in water has been investigated experimentally. Main concerns were the flow and heat transfer characteristics of high-Rayleigh number flows. The square cylinders having side length from 10 to 300 mm were utilized as a test cylinder, and they were heated with uniform heat fluxes. The modified Rayleigh numbers based on the side length ranged as; Ra_d^* = 2×10⁵-2×10¹². The flow and the surface temperature were visualized with dye and liquid crystal thermometry, respectively. The results showed that the flow ascending along the side surface separates from the upper edges of the cylinder when the modified Rayleigh numbers exceed Ra_d^* = 2×10⁶. The local heat transfer coefficients along the periphery of the cylinder were also measured. The results showed that the coefficients from the upper surface are increased significantly when the above separation takes place.