6.3. Cooling plaques or submerged coils

The coolant fluid flows through an exchanger (plaque or coil) submerged in the must/wine. The refrigeration is based on convection and conduction phenomena.

It is a very economical solution as it does not require special tanks and large accessory installations. It is applied in wine cellars of small and medium capacity that have tanks with volumes never exceeding 300 hl. As an advantage, the possibility of placing them in the zones of maximum thermal generation is at any level and from the beginning of fermentation.

Both plates and coils are constructed of stainless steel and are usually mobile structures that are moved from one tank to another by flexible conducts. Glycol water circulates in its interior at temperatures of 5–7�C or refrigerating fluids with similar evaporating temperature.

The refrigeration capacity generated is calculated in the same way as in the case of outer cooling jackets, taking into account that in this case the exchange surface is double as both sides are in contact with the must/wine (Eq. (27)):

$$Q\_t = \mathcal{U} \times \mathcal{S} \times \left( T\_{\text{inside\\_track}} - T\_{\text{circular\\_water}} \right)\_{\text{ml}} \tag{27}$$

taking U as the same values of those mentioned above.
