In our previous post, we discussed the need for, and ubiquity of temperature control measures in commercial wine making. In this post, we will take a closer look at the options available in the industry for vessels with cooling capability.

It should be noted that although historically different materials have been used in the construction of tanks in wineries. In modern times, by far the most common material of construction is stainless steel.

The most common types of tank jackets and their attributes are discussed below.

1. Double Wall or conventional jacket
   1. This is considered the simplest style of construction. Essentially, a second shell is installed over the main shell of the vessel. The annular space between the two is used to circulate cooling or heating media.
   2. This style typically has the thickest shell wall, making it the heaviest. These tanks also tend to be expensive. In process industries, they tend to be used when heat transfer occurs by condensation, such as using steam.Fig 1: Double Wall Jacketed Tank
2. Half pipe or Limpet coil jacket
   1. In this style of tanks, coils of “half pipes” are welded to the external surface of the tank forming channels outside the shell where cooling or heating media circulates. In some cases, rectangular channels instead of round pipes are used.
   2. This style of construction adds rigidity to the tank shell which allows shell thickness to be reduced and therefore reduces material usage and weight. The reduced shell thickness provides larger heat transfer rates. The channels have lower resistance to flow permitting higher flow rates than dimpled jackets resulting in reduced pumping power. Since the channels of flow are wider than those in a dimpled jacket, they are less susceptible to sediment blockages.
   3. These tanks are generally more expensive than dimpled jackets and are more common in chemical, petrochemical and power industries than in wineries.Fig 2: Half Pipe Jacketed Tank
3. Dimple jacket
   1. In this style of tank, a thin metal sheet is welded at various points on to the outer shell of the main tank. After the cover is welded, the space between the cover sheet and tank shell is pressurized which causes the metal sheet to expand causing pockets to be formed around the individual spot welds. This creates a characteristic dimple around the spot welds which also forms a space around individual dimples. The heating or cooling media circulates in this space. This type of tank is the most common in commercial wineries.
   2. These jackets typically have a lower working pressure rating than the other types. They have higher resistance to flow hence, require more pumping power.
   3. The weld procedure may employ plug welding or spot welding. When weighing the decision between the two, it is important to do a proper analysis of pressure, flow and heat transfer implications and how it affects the overall integration of the system.Fig 3: Dimple Jacket Tank
4. Internal coils
   1. When corrosivity, cleanability and accidental mixing of the two media are not critical factors coupled with high heat transfer rate, then immersed internal coils are economic options.Fig 4: Tank with Internal Coil