Second law analysis of heat transfer surfaces in circulating fluidized beds

The correct sizing of the heat transfer surfaces is important to ensure proper operation, load turndown, and optimization of circulating fluidized beds (CFBs). From this point of view, in this study, the thermodynamic second law analysis of heat transfer surfaces in CFBs is investigated theoretically in order to define the parameters that affect the system efficiency. Using a previously developed 2D CFB model which uses the particle-based approach and integrates and simultaneously predicts the hydrodynamics and combustion aspects, second law efficiency and entropy generation values are obtained at different height and volume ratios of the heat transfer surfaces for CFBs. Besides that, the influences of the water flow rates and heat exchanger tube diameters on the second law efficiency are investigated. Through this analysis, the dimensions, arrangement and type of the heat transfer surfaces which achieve maximum efficiency are obtained.