Energy and exergy analysis for cocurrent gas spray cooling systems based on the results of mathematical modeling and simulation

The present study provides a descriptive mathematical model for energy and exergy analysis for a cocurrent gas spray cooling system. Conservation laws of mass, energy and momentum are used to predict the variation of temperature and enthalpy of gas and liquid streams along the tower length. The same procedure is also used to calculate the energy and exergy efficiencies. The validity of the model for predicting variations in gas and liquid characteristics along the tower length was examined against some operating data measured in a commercial cement plant. The results show that in spite of high energy efficiency, the gas spray cooling systems have relatively low exergy efficiency. This was due to thermodynamic irreversibilities and entropy production during heat and mass transfer processes. Also the effect of some operating parameters, including tower diameter, tower length, liquid drop size distribution and water flow rate was investigated, on the amount of exergy destruction. This study also concluded that the exergy of water is not completely absorbed by gas and a remarkable portion of exergy is destroyed. Results of such investigations may provide us with the true energy potential carried by fluids.