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Thermosiphons, or natural circulation loops, are circuits in which a flow pattern is driven by buoyancy forces originated from density differences, a consequence of temperature gradient. In this study, an evaporation section was evaluated by numerical simulations, in order to determine heat flux conditions for a pilot-scale thermosiphon. A two-fluid Eulerian-Eulerian model was used to represent multiphase fluid dynamic, including heat transfer and phase change effects. The results showed that a 1000 W rate is enough to generate a nucleate boiling regime. Rates up to 2000 W produce a mean vapor volume fraction greater than 0.30 at boiling region. As a result, the pilot-scale thermosiphon was designed with four 500 W electrical resistances.

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