Improvement of the Environmental and Economic Characteristics of Cooling Towers. Part I:Heat Rejection from Horizontal Tubes to Shallow Fluidized Beds.

摘要

As fluidized beds can increase the heat transfer from a surface,they can potentially be coupled with dry cooling towers. Existing heat transfer mechanism models for fluidized beds are discussed,and a new model presented. Heat transfer coefficients from a horizontal tube in a row of dummy tubes to a shallow fluidized bed were experimentally measured. The experimental data is compared to existing horizontal tube correlations and the new model. The RMS deviation of data from the model is less than 17%. The best correlation was obtained by modifying the Vreedenberg correlation to include a dependency on the bed particle fraction (RMS deviation: 13.8%). Economic optimizations were performed to compare fluidized bed dry towers to a finned tube tower. For a 1000Mw plant,heat exchanger costs are 13% lower for fluidized beds,but the cost for the power keeping the bed fluidized yields an incremental cost 16% higher than that for a finned surface. Incremental costs rapidly approach that of finned tubes as the particle size and depth are reduced.