Analysis of multi-region conduction-controlled rewetting of a hot surface with precursory cooling by variational integral method

• The effect of sputtering region and precursory cooling on rewetting velocity is discussed.
• Closed form expression is presented for temperature distribution and wet front velocity.
• Sputtering region and precursory cooling strongly influence the wet front velocity.
• Neglecting the precursory cooling in the model may under predict the rewetting velocity.
• Variational method solution exhibit good agreement with test data and available results.

An analytical model has been proposed to evaluate rewetting velocity by employing variational integral method. The model considers three distinct regions: a dry region ahead of wet front, the sputtering region immediately behind the wet front and a continuous film region further upstream. Two different models are considered in the sputtering region for the analysis. First model considers a constant heat transfer coefficient in the sputtering region; while the other one propose a variation in heat transfer coefficient in the sputtering region. Both the models consider a constant heat transfer coefficient in the wet region and exponentially varying heat transfer coefficient in the dry region ahead of wet front. For all the cases the closed form expression is obtained for temperature field along axial direction. Relationship between various rewetting parameters such as; Peclet number, Biot number, dry wall temperature, incipient boiling temperature, sputtering length, magnitude of precursory cooling and the extent of precursory cooling has been obtained from the analysis. Present prediction obtained by employing variational integral method exhibits an excellent agreement with the previous analytical results [1], [2], [3] and [4] and test data [5], [6] and [23].