Heat Transfer With Vaporization of a Liquid by Direct Contact in Another Immiscible Liquid: Experimental and Numerical Study

An experimental setup was designed to study direct-contact evaporators using a liquid dispersed in another immiscible liquid. The study was carried out on an n-pentane–water system to determine the influence of different parameters on these systems, and consequently to construct a model for this type of evaporator. An optical probe was used to measure the local void fraction. At different column abscissas along a selected diameter, the local void fraction variations were determined. The shape of the curves can be attributed to the different processes occurring in the spray column. A one-dimensional heat transfer model in the spray column was established. Simplifying assumptions were used to establish and resolve the set of equations governing heat transfer and two-phase flow. The vaporization process induces a volumetric expansion of the two-phase mixture. A theoretical model was used, in which the coalescence between the spherical fluid particles is taken into account. Different coalescence laws dependent on particle density were introduced into the theoretical model and then tested. The numerical results are discussed and compared with the experimental data obtained for the n-pentane–water system.