Thermofluid Design and Performance Evaluation of a Natural Draft Air-Cooled Condenser Towards Annual Performance Modelling of Concentrated Solar Power Plants

This paper presents the sizing and performance evaluation of a natural draft air-cooled condenser with nominal heat rejection capacity of 75 MW_th for implementation at a concentrated solar power plant in the Northern Cape province, South Africa. Initial sizing and optimisation of the tower geometry is done with the aid of a one-dimensional thermofluid model at design conditions. An exhaustive search optimisation is used based on Latin hypercube sampling that covers the geometric design envelope, which is defined via the tower and heat exchanger heights, and the tower base and outlet diameters. Following this, the performance of the best-performing tower geometry is verified via detailed three-dimensional computational fluid dynamics (CFD), and the geometry adjusted slightly to achieve the desired heat rejection capacity. This process includes validation of the CFD model against previous work as well as performing grid convergence studies to ensure mesh independence. Finally, a methodology is presented to evaluate the performance of the system over the full range of ambient conditions encountered during an annual operating cycle. The methodology will be applied in further work to develop a reduced order surrogate model for application in annual performance studies.