Experimental study on heat transfer of horizontal-tube falling-film flow in deviated columnar mode

Abstract

Column flow is the most widely used flow pattern in horizontal-tube falling-film evaporators. Ideally, the liquid column is in the center plane of horizontal tube. In the actual falling-film evaporator, the installation deviation of nozzles, the steam sweep, as well as the disturbance caused by flash evaporation make the liquid column deviate from the center plane. The heat transfer characteristics of deviated columnar flow and its influencing factors were experimentally studied and analyzed in this paper. The results are as follows: The vertex of heat transfer coefficient curve shifts to the negative angle interval as the deviation distance increases. Meanwhile, the maximum value decreases with the increase of liquid column deviation distance. The heat transfer coefficients in the negative angle interval are greater than those at corresponding position in the positive angle interval. The heat transfer coefficients increase with the increase of evaporation temperature, spray density, and tube spacing, respectively.