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

• Optimal column height is obtained and analyzed in detail.
• The effect of packing on heat transfer performance is analyzed.
• The effect of packing under lower temperature difference is larger.
• Packing increases volumetric heat transfer coefficient.
• Packing decreases optimal column height.

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.

An experiment was conducted to investigate the effect of Dixon rings on direct contact evaporative heat transfer performance. N-pentane and water were selected and operated in a bubble column with concurrent upward flow. The optimal column height and volumetric heat transfer coefficient were obtained and compared with and without Dixon rings varying flow velocity ratio of n-pentane to water, temperature difference and distributor aperture. The influence of packing on volumetric heat transfer coefficient and optimal column height were analyzed specifically. And we also examined the effect of flow velocity ratio of n-pentane to water, temperature difference and distributor aperture on heat transfer performance. The mainly results show that packing can considerably increase the volumetric heat transfer coefficient and decrease optimal column height. Besides, backmixing occurred in the experiment was also discussed.Figure optionsDownload as PowerPoint slide