Development and validation of physical based model of heat exchangers for an ORC power plant

Development and validation of a physical based model of heat exchangers for an Organic Rankine Cycle power plant, with R245fa as operating fluid. The main goal was to recreate a virtual model of a specific brazed plate heat exchanger, modelling its geometry and the heat exchange between the hot side and the cold side, using the simulation software GT-Power. In order to effect this, it was necessary to study the heat flow of these types of exchangers, to learn the fundamental variables and how these influence the constitutive equations, with the aim of being able to correctly develop a model that would describe the reality of the exchange. Once a first geometric model has been developed, the primary necessity was to implement the countercurrent exchange. After this, it has been concentrated on the main coefficients that affect the heat exchange, by setting a calibration parameter of the equation that models the heat transfer between the heat exchangers’ plates, called Heat Transfer Multiplier, to obtain a model that better recreates the experimental quantities. After having implemented the previous map-based exchangers with the new physical-based ones, the complete ORC power plant model was validated using a multi-objective multi-object optimization, minimizing the relative percentage error of some quantities of the physical based model, calculated using the correspondent experimental quantities, in different operating conditions. The methodology proved to be effective, reducing the error between the quantities, not only in the operating conditions chosen in the optimization, but also in those not used.