Comparative analysis of droplet characteristics generated in the outer cavity of RPB for two packings

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The RPBs may differ in the orientation of the rotating packing, its dimensions, and the type of the packing. In this work, the influence of the last issue is analysed. The diameter of droplets formed on the outer surface of the packing is used to compare two packings (both with dimensions ID150/OD300/H30 mm). The metal foam packing RCM-NCX1116.10 had a porosity of 92 % and a specific surface of 1000 m2/m3 and the stainless steel wire mesh packing had a porosity of 82 % and a specific surface of 874 m2/m3. A high-speed camera FASTCAM SA-Z with a 180mm f/2.8 lens was used in the backlight illumination. Droplets dimensions were analysed using a LoG filter in an in-house MATLAB® code. The liquid was supplied by six plain orifice atomizers with a jet velocity of 1.25, 1.8, 3 and 4.3 m/s. The rotational speeds of the packings were 410, 614, 819 and 1229 rpm. It was observed that on the surface of the metal foam, liquid accumulated in the pores and hence liquid ligaments were generated. The number of these ligaments was found to increase with the higher liquid flow rate. On the other hand, no ligaments were found on the surface of the wire mesh packing. A possible explanation is that for the lower porosity packing, liquid travels in the form of droplets and liquid bridges between layers of the packing, and hence droplets are generated on each wire. The bimodal distribution of droplet diameters was found for both packings; however, it was more significant for the metal foam packing. Furthermore, the liquid flow rate did not influence dimensions of the droplets and with the higher packing speed, the droplet sizes systematically decreased.

The RPBs may differ in the orientation of the rotating packing, its dimensions, and the type of the packing. In this work, the influence of the last issue is analysed. The diameter of droplets formed on the outer surface of the packing is used to compare two packings (both with dimensions ID150/OD300/H30 mm). The metal foam packing RCM-NCX1116.10 had a porosity of 92 % and a specific surface of 1000 m2/m3 and the stainless steel wire mesh packing had a porosity of 82 % and a specific surface of 874 m2/m3. A high-speed camera FASTCAM SA-Z with a 180mm f/2.8 lens was used in the backlight illumination. Droplets dimensions were analysed using a LoG filter in an in-house MATLAB® code. The liquid was supplied by six plain orifice atomizers with a jet velocity of 1.25, 1.8, 3 and 4.3 m/s. The rotational speeds of the packings were 410, 614, 819 and 1229 rpm. It was observed that on the surface of the metal foam, liquid accumulated in the pores and hence liquid ligaments were generated. The number of these ligaments was found to increase with the higher liquid flow rate. On the other hand, no ligaments were found on the surface of the wire mesh packing. A possible explanation is that for the lower porosity packing, liquid travels in the form of droplets and liquid bridges between layers of the packing, and hence droplets are generated on each wire. The bimodal distribution of droplet diameters was found for both packings; however, it was more significant for the metal foam packing. Furthermore, the liquid flow rate did not influence dimensions of the droplets and with the higher packing speed, the droplet sizes systematically decreased.

Rotating packed bed, droplet characteristics, outer cavity, high-speed visualization

19.10.2023

Ilass Asia 2023

Jeju

207–208

2