Two-Phase Flow Simulations within Plate Heat Exchangers

Plate heat exchangers are widely adopted in many industrial applications, such as ventilation, air conditioning, heat transfer processes, heat pumps and cooling of hydrodynamic circuits in engines. They provide higher heat transfer performance, compactness and flexibility as well as lower pressure drops compared to conventional tubular heat exchangers and are thus also used in various electronics cooling systems. Thus, they are also excellent units to use, for instance, as water-cooled condensers in electronics thermosyphon two-phase cooling systems. The current paper presents a novel inhouse simulation code for accurately rating and designing, under steady-state conditions, of single-and multi-passage plate heat exchangers. The basis of the code is a local one dimensional effectiveness-NTU approach coupled with the best proven methods for heat transfer coefficients and frictional pressure drops from literature; it has been implemented to model single-phase, evaporating and condensing flows over a wide range of operating test conditions, plate geometries and working fluids. The first part of the paper presents an overview of the modeling scheme and the associated flow chart. After that, the simulation results are validated against a diversified experimental database demonstrating a good agreement in terms of two-phase refrigerant side heat transfer coefficients and frictional pressure drops. Next, a simulation case study is provided to compare the local thermal-hydraulic performance between parallel-and counter-flow configurations. Finally, a sensitivity analysis is performed to analyze in detail the effects of the chevron angle and corrugation aspect ratio through the definition of the plate heat exchanger performance index that includes both overall heat duty and total pressure drop.