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Highlights: 1. The full scale 1-D and 3-D simulation models of a 20m NDDCT was developed. 2. The ambient temperature and hot water inlet temperature effect had been investigated 3. The crosswind effect on the small NDDCT was analysed and discussed ABSTRACT: A Natural draft dry cooling tower (NDDCT) is a cost-effective cooling technology which can be utilized in most of the small renewable power plants. While a number of numerical studies have been done on NDDCTs in recent decades, experimental studies on full scale small cooling tower are very few. To fill this gap, Queensland Geothermal Energy Centre of Excellence (QGECE) has built a 20 m NDDCT. In this study, a 1-D analytical and a 3-D CFD models of this cooling tower were developed and the cooling performance was investigated at different ambient temperatures, inlet water temperatures and crosswind speeds. The results show that NDDCT in such a size is capable for a 2~3 MW CST power plant. The cooling performance of the NDDCT decreases with the increase in the ambient temperature and the decrease in the inlet water temperature. In terms of the crosswind, the heat rejection ratio decreases with the increase of the crosswind velocity at low crosswind speeds. However, when the crosswind speed becomes large enough, the heat dumped at the bottom of the tower can compensate some losses in cooling capacity caused by crosswind. The results found in the present study give reference for future tests.