The effect of Dixon rings on direct contact evaporative heat transfer performance

Abstract

Experimental study was conducted to investigate the effect of packing on performance of direct contact evaporative heat transfer for n-pentane and water operated in a bubble column with concurrent upward flow. The optimal column height and volumetric heat transfer coefficient with and without Dixon rings were examined and compared under the conditions of different flow velocity ratios of n-pentane to water, temperature differences between water and n-pentane and distributor apertures. It is found that packing enables optimal column height to decrease significantly. Optimal column height considerably reduces maximally by 25% under temperature difference less than 8 °C and flow velocity ratio 0.265. Volumetric heat transfer coefficient is 100–450 kW/(m3 °C) with packing while 40–150 kW/(m3 °C) without packing. Especially when the flow velocity ratio is 0.265 and 0.192, volumetric heat transfer coefficient with packing is nearly twice as much as that in bubble column without packing at the temperature difference below 8 °C. The effect of packing at temperature difference below 8 °C is more pronounced. Besides, backmixing observed in the experiment was demonstrated, and its significant influence on evaporative heat transfer performance was also analyzed.