STEADY-STATE TRANSITION BOILING ON THIN WIRES IN LIQUID-NITROGEN - THE ROLE OF TAYLOR WAVELENGTH

Transition boiling on a thin wire in liquid nitrogen is investigated. Results presented in the form of a classical boiling curve exhibit som e discontinuous branches in the mixed boiling region, located between the negative slope area and the firm boiling regime. A model is propos ed in order to explain this new feature. It is based on steady coexist ence of two areas, one in nucleate and one in film boiling. The main h ypothesis concerns the wire length covered with film bailing which is supposed to be a multiple of the Taylor wavelength, this last quantity being commonly regarded as the interval separating two neighbouring v apour pockets in the film boiling regime. The temperature of each area is allowed to vary in a range compatible with the respective regime. The comparison with experimental results shows that some branches deve lop with a constant proportion of each regime. Furthermore, this model shows that no steady branch is observed when the wire length covered with film boiling is less than one Taylor wavelength. The only experim ental points occurring in this case are those located in the negative slope area. (C) 1998 Elsevier Science Ltd. All rights reserved.