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This work intended to model the cryogenic nitrogen spray under supercritical conditions using tabulated real-gas fluid properties. To investigate the effects of various equations of states (EoSs), four tables were generated using different EoSs such as the idea gas (IG), Peng-Robinson (PR), Soave-Redlich-Kwong (SRK), and Redlich-Kwong-Peng-Robinson (RKPR). For validations, the tabulated fluid properties using the CoolProp library were taken as the baseline case. The modelling results demonstrated that all the real-gas EoSs predicted similar spray features except for the IG EoS, which significantly underpredicted the density gradient and led to less intense jet diffusion and shorter penetration length. Of the four EoSs, the PR EoS exhibited the best agreement with the baseline case. Furthermore, the effect of ambient pressure on the spray development was also examined, ranging from the subcritical to the supercritical conditions. A highly diffusive and longer jet was observed under supercritical conditions (4 and 5 MPa). Thereafter, the effect of ambient temperature was also evaluated. It was found that the higher chamber temperature led to a more rapid decrease in density due to the better evaporation process, which resulted in a longer jet breakup length.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2006. / Cooling tower spray nozzle performance characteristics such as the water distribution onto the fill material, air side pressure drop, pump head, drop size distribution and heat transfer in the spray zone were investigated experimentally and theoretically. The aim was to evaluate and simulate the performance characteristics of new and existing types of cooling tower spray nozzles with emphasis on the spray zone. Two medium and two low pressure type spray nozzles were tested and the results analysed. Single nozzle water distribution data obtained from tests was used to predict the water distribution obtained from four evenly spaced nozzles by superposition. The results were compared to data obtained from corresponding four nozzle tests. Computer codes and CFD models were developed to predict the drop trajectories, water distribution, total heat transfer and pressure drop for single nozzles and four nozzle grids. This was compared to correlated data found in literature. The performance characteristics expected from an ideal nozzle was discussed and compared to actual nozzle performance characteristics.