Thermodynamic optimisation of the herringbone corrugation of a brazed plate heat exchanger (BPHE) in two-phase heat transfer

This paper presents the thermodynamic optimisation of the corrugated surface of a herringbone-type Brazed Plate Heat Exchanger (BPHE) for refrigerant boiling and condensation. The optimisation was performed by coupling the Entropy Generation Minimisation (EGM) method with theoretical models for predicting heat transfer coefficients (HTCs) and pressure drops on both the refrigerant and water sides. The optimisation refers to boiling and condensation of the natural refrigerants R290 (Propane) and R600a (Isobutane) and the low-GWP refrigerant R513A within a small commercial BPHE in the typical operating range for air-conditioning and heat pump applications. The optimisation procedure identifies the optimal values of the inclination angle β and the corrugation depth e: the optimal β angle is in the range 52–58° for boiling and 36–58° for condensation, while the optimal corrugation depth e varies in the range 0.8–1.0 mm for boiling and 0.8–1.2 for condensation. The optimal β angle and corrugation depth e are 10–40 % and 40–60 % lower than the values applied in current series production, respectively.