Experimental research of CFB ash deposition on helical finned tubes

In order to evaluate the influence of ash deposition on heat transfer, experiments focusing on the influence of ash deposition on heat transfer are carried out in a 75t/h CFB(circulating fluidized bed) boiler unit. The test bundles are made of helical finned tubes in staggered or in-line arrangement. The fouling factor ɛ and the overall heat transfer coefficient ratio ψ are employed to evaluate the influence of ash deposition. The fitting correlations of ɛ and ψ under different flue gas velocities are obtained respectively. The experiment reveals that the fouling factor decreases and the overall heat transfer coefficient ratio increases with the rising flue gas velocity. Compared with the in-line arrangement, the staggered arrangement helps to lighten ash deposition. The fouling factors obtained from the present experiments are one-order smaller in the magnitude than the recommended values that are widely used in China at present. And the present results are of the same order as those gained from cold test with sands instead of fly ash. Compared with the existing research, the present results are more suitable for application in practice.