Transport through single-hole baffles in industry hydrothermal autoclaves with three-dimensional flows

Hydrothermal growth is the industrial preference to obtain high quality piezoelectric crystals. The industry growth process is carried out in autoclaves, cylindrical containers filled with an aqueous solution. The solution flows in industry autoclaves during growth are usually three-dimensional. A baffle is normally used to partition an autoclave into two chambers and reduce flow strength. In this paper transport through single-hole baffles of various area openings in the three-dimensional flow is investigated systematically. It was found that a single-hole baffle is effective in controlling the fluid exchange and heat transfer between the two chambers. A smaller baffle opening leads to a more uniform thermal environment for growth. Flow structure and heat transfer data show that there is a pair of steady flow streams between the two chambers. However the heat exchange carried by this pair of streams, as well as heat exchange through molecular diffusion, is negligibly small. Transport through baffle opening is dominated by turbulence diffusion. Heat transfer analysis shows that heat flow rate depends on both the baffle opening area and the area of the chamber walls.