Correlation for Maximum Heat Transfer Between Fluidized Bed and Its Wall and Application to Solar Power Plants

Abstract

Heat transfer from and to fluidized beds is involved in many applications including chemical processes, power generation, solar collectors, etc. It is generally desired to operate in the range in which the heat transfer coefficient is maximum. Several good correlations have been developed for maximum heat transfer to objects immersed in fluidized beds. However, there is no correlation for maximum heat transfer between the fluidized bed and its enclosing wall. The present research was done to develop such a correlation. A correlation for maximum heat transfer to bed wall has been developed which is in satisfactory agreement with test data from published papers. The data include a wide variety of particles with diameters 70–900 µm, bed diameters 25–101 mm, particle density from 1800 to 3200 kg/m3, particle thermal conductivity 0.5–237 W/m/K, and bed temperature from 18 to 316 °C. A correlation for the optimum velocity was also developed based on the same data. The new heat transfer correlation was compared to published test data for fluidized beds made to flow into solar collector tubes by the application of pressure difference. A modification of it was developed which agrees well with available data.