A new theoretical method for predicating the part-load performance of natural draft dry cooling towers

A new theoretical model is proposed to predict thermal performance of natural draft dry cooling tower (NDDCT) under various ambient conditions. When evaluating the effect of ambient temperature, heat rejection of the NDDCT is converted to the form that is proportional to the power function of initial temperature difference of the tower, using the theory of similar triangles. Heat rejection of the NDDCT Under windy condition is simply calculated based on the outlet air velocity obtained by a proposed algorithm. Although this theoretical model is inappropriate at crosswind velocity higher than the critical wind velocity, it's still meaningful for thermal performance prediction of the NDDCT, because this critical wind velocity is usually large and uncommon in the practical operation of the tower. Testing work for a 600MWth and other two NDDCTs is conducted using this theoretical model flexibly, and the predictions agree well with practical measurement data or results available in the existing literatures. In addition, analysis of the 600MWth NDDCT shows that under a lager initial temperature difference, the tower has larger resistance to crosswind and cooling efficiency declines more slowly, Moreover, heat rejection of the tower increases more rapidly with initial temperature difference under a smaller crosswind velocity. (C) 2015 Elsevier Ltd. All rights reserved.