How Tank Geometry Affects Mixing
Posted on May 25, 2021 by Paige Pesko
When one thinks of the factors that go into a mixer’s efficiency, the focus often turns to the mixer itself. While considerations like a mixer’s power and speed are important, they are not the only elements at play. How the vessel is shaped also determines how efficiently a product is mixed. Understanding how tank geometry affects mixing will help you determine the best vessel shape for your company.
Cylinders are one of the most common shapes one finds for mixing tanks. This makes sense because they follow the circular pattern most mixers use and avoid any corners where solid particles can gather.
However, because of the tanks’ rounded shape, low-viscosity liquids can be prone to “vortexing” when mixed with a vertically mounted, centered mixer. This is when the entire contents of the tank move without mixing together. To avoid this phenomenon, engineers equip tanks with attachments called baffles. These metallic plates bolted to tank interiors help disrupt the flow of the liquid enough to prevent vortexing.
A Note on Mixing Strength
The caveat of using baffles to prevent vortexing is that they create greater resistance in the liquid. That means you may need to use a higher strength mixer to get the best results.
Rectangular tanks can seem counterintuitive at first glance. Particles often become caught in the corners of the tank when mixing liquids with solid suspensions. However, they often lend themselves well to low-viscosity liquids or operations that require blending instead of just mixing. That’s because the corners of the tank act as baffles, preventing vortexing.
Mixing tanks with cone bottoms are ideal for operations where 100 percent drainage is especially important or when a facility needs to mix high-solid content slurries. However, solid suspension is where this tank struggles.
Dished bottom tanks do not provide the same level of drainage as cone-bottom tanks do. However, they make up for this issue in their ability to support solid suspensions in mixing. Because the bottom has no angles, there are few opportunities for dead spaces where solids can gather.
Knowing how tank geometry impacts mixing can make all the difference when choosing a tank for your facility’s purposes. Fortunately, Cedarstone Industry has a variety of stainless steel storage tanks with the perfect shape for your product.