Experimental investigation and modelling of condensation in micro-structured plate heat exchangers

With a micro-structured plate heat exchanger with mixed angles, the heat transfer and pressure drop of pure refrigerants and their mixtures during condensation is presented and investigated. For this purpose, a test rig of a vapor compression refrigeration system and a test bench of visualization were developed and built in the institute of Thermodynamics at the Gottfried Wilhelm Leibniz University of Hannover. Based on the visualization results, the influence of flow patterns on heat transfer and pressure drop is thermodynamically investigated, a new heat transfer model based on flow patterns is developed. The micro-structure improves heat transfer during condensation, new correlations are established for the prediction of quasi-local heat transfer coefficients and two-phase frictional pressure drop, by considering the specific properties of fluids and geometry. The course of the mixtures, together with the results from the literature, confirms that the model for pure refrigerants enables good prediction for azeotropic and near-azeotropic mixtures.