Ocean thermal energy conversion net power maximization for the optimization of plate heat exchanger geometry

Abstract

Ocean Thermal Energy Conversion is a steady source of renewable energy that uses the natural temperature gradient within the ocean but requires large and expensive heat exchangers, considerably contributing to the overall cost. Thus, this study focuses on finding optimum herringbone plate heat exchangers geometry leading to the highest net power output to heat transfer area ratio $\left(w_{net}\right)$. A method to assess and maximize $w_{net}$ is developed, applied to a heat exchanger geometry from the literature, before being used to find optimum geometries , which resulted in a 33.8% increase in $w_{net}$ compared with the geometry used as reference, at chevron angles of 48.7° and 30°, mean channel spacing of 3.7 and 1.5 mm, corrugation pitches of 15 and 6.0 mm, and width to length ratios of 0.6 and 1 for the evaporator and condenser, respectively. The effect of each parameter is also analyzed showing a high impact of evaporator mean channel spacing and corrugation pitch and identified possible geometries for further studies. A sensitivity analysis revealed a design gross power with, granted a sufficient pipe diameter, negligible effect on optimum geometries, while the heat source temperature difference yielded two possible optimum for the condenser and a potential single one for the evaporator.