Natural convection in a hemispherical enclosure heated from below

Natural convection in a hemisphere heated from below was studied experimentally. Correlation between heat transfer rate and Rayleigh number was obtained on a hemispherical surface over wide parameter ranges : 106 ⩽ Ra ⩽ 6 × 1010 and 6 ⩽ Pr ⩽ 13000. The exponent of Nu against Ra changes from 14 to 13 at about Ra ~ 109. Flow patterns in a hemisphere were observed for 2 × 105 ⩽ Ra ⩽ 2 × 109 and 6 ⩽ Pr ⩽ 13000. The patterns were classified into several flow regimes, i.e. steady circulating flow, flow with periodic thermal plumes, flow with irregular thermal plumes and turbulent flow regime. Experimental results show that fully turbulent flow regime occurs at Ra ~ 109.

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