Reduced order model of heat and mass transfer in wet cooling tower fills

Application of the Proper Orthogonal Decomposition (POD) to produce a reduced model of heat and mass transfer model in a fill of a wet cooling tower is presented. The process of heat rejection in a vertical channel of the fill concerns convective heat exchange between air and water flowing in counter current accompanied by water evaporation. The process of simultaneous mass and heat transfer is described by a set of four first order ordinary differential equations with two points boundary conditions. The set is solved using Runge Kutta solver with automatic step adaptation for a sequence of input vectors. The components of these vectors are the crucial input data of the process: inlet mass fluxes and temperatures of water and air as well as the inlet humidity of the air. The solution yields a set of response vectors gathering the distribution of heat and mass sources along the channel. The relationship is then represented by Proper Orthogonal Decomposition (POD) and Radial Basis Functions network. In the process of constructing this network the correlation between the response vectors is accounted for leading to a low dimensional representation. The created POD model is then used in the CFD simulation of a natural draught wet-cooling tower, considerably reducing the computational time of the simulation without affecting the accuracy thereof.