Entropy generation minimization analysis in a fluidized bed heat exchanger

This work presents an experimental study of the entropy generation in a fluidized bed heat exchanger used for heat recovering from sand particles discharged by an incinerator at about 750 degrees C. This heat exchanger is characterized by presenting two fluids (air for fluidization and water flowing inside an immersed tube) that recover energy from solid particles (sand). The objective was to analyze the influence of the factors affecting the heat exchanger performance. The analysis of data was made from 2(3) factorial experiments planning with three central points. The studied factors were: heat transfer area (A), number of baffles immersed in the fluidized bed, and heat capacity ratio of solid material and water (C). First reply variable analyzed was the number of units of entropy generation (N-S). The following reply variables were also, analyzed: exergetic efficiency (N-exe), and heat exchanger effectiveness (is an element of). The effectiveness was an interesting but insufficient indicator for the system analysis. When the analysis is combined with exergetic analysis and entropy generation minimization method, the criteria of optimization and all adequate operation of the system can be reached.