An experimental study of radiative and total heat transfer between a high temperature fluidized bed and an array of immersed tubes.

摘要

Experimental data are reported for the time-averaged local radiative and total heat transfer coefficients for both an array of horizontal tubes as well as a single horizontal tube immersed in a large-particle fluidized bed at elevated temperatures. Spatial-averaged heat transfer coefficients computed from the local values, using a simple trapezoidal rule integration, are reported.; An instrumented tube was used to measure both the radiative and total heat transfer rates simultaneously. Three different window materials, silicon, sapphire, and quartz, have been tested in order to examine some key design decisions made in the development of the radiation detector. It is concluded that the radiation detector employing silicon as the window material is most suitable to achieve accurate measurements of the radiative heat transfer between a fluidized bed and immersed surfaces.; Experiments were conducted at the Oregon State University high temperature fluidized bed facility employing ione grain as the bed material. Measurements were made for two particle sizes (2.14 mm and 3.23 mm) and at three different bed temperatures (812 K, 925 K, and 1000 K).; The radiative heat transfer results for tube arrays are believed to be the first of their kind. In comparing these results with those for a single tube, it was found that the radiative heat transfer coefficient decreases with increases in both bed temperature and particle size due to the presence of neighboring "cool" tubes in a hot bed and the greater "see through" effect of the larger particles. Radiation contributions for a bubbling bed were calculated for various test conditions.; The effects of superficial velocity, bed temperature, particle size, and adjacent "cool" tubes on both the radiative and total heat transfer performance are described with comparisons made between the results of this study and available literature data or correlations.