Energy and Exergy Analysis of a Co-Current Gas Cooling Tower Based on Mathematical Modeling and Simulation Results

Beginning with a discussion of energy and exergy analysis definitions, the presented study provides a descriptive mathematical model for energy and exergy analysis for a co-current gas cooling tower. For this purpose using conservation laws of mass, energy and momentum, the variation of temperature and enthalpy of gas and liquid streams are predicted along the tower length and are used in order to calculate the energy and exergy efficiencies. The model validity in prediction of gas and liquid characteristics changing along the tower length was examined against some operating data measured in a commercial cement plant. As a result, it was concluded that in spite of high energy efficiency, the cooling tower has a relatively low exergic efficiency which is because of thermodynamic irreversibilities and entropy production during heat and mass transfers. Also, the effect of some operating parameters including tower diameter, tower length, liquid drops size distribution and water flow rate was investigated on amount of exergy destruction. In all cases the results showed that the exergy of water does not completely absorbed by gas and a notable portion of the exergy is destructed. The result of these investigations may be employed to inform about the true energy potential caring by fluids.