Beer fermentation is a low temperature fermentation. The heat generated in the fermentation process must be discharged in time to reduce the fermentation broth to the required temperature. Despite the diversity of fermentation processes, there are four stages in the fermentation process:
　　1. After inoculation, the temperature rises to diacetyl reduction temperature. This period of hypoglycemia is intense. Some of the heat generated must be removed and the other part used for self-heating. One kg of sugar fermentation will produce 587 heat tolerance.
　　2. Constant temperature stage. The heat produced by lowering blood sugar needs to be removed completely.
　　3. After complete reduction of diacetyl, the temperature drops rapidly to the post-fermentation temperature. At this time, besides cooling blood sugar, cooling also requires a lot of energy. Specifically, diacetyl is reduced to 0.2 mg/L and to 1-2 C within 72 hours.
　　4. In the heat preservation stage of post-fermentation, a small amount of sugar needs to be decomposed to produce heat.
　　The maximum amount of cooling required per unit time in four sections is C. The cooling capacity and cooling area are usually calculated on the basis of this section, i.e. 72 hours. The refrigerants are mainly ammonia and ethanol water. Although ammonia direct evaporation has been widely used in beer fermentation tanks abroad, it has the advantages of reducing energy consumption and operating costs, but because of the difficulties in manufacturing and inspection and the corresponding control level, only a few well-funded factories in China have adopted ammonia direct evaporation, and most factories still choose ethanol water at 13-14 degrees Celsius as refrigerant. Because there is less hypoglycemia during the cooling process, that is to say, C02 bubble movement reduces the heat conductivity. For large diameter tanks, especially those with diameter greater than 5 m or volume greater than 300 m 3, it is very difficult to use ethanol water as refrigerant. In order to achieve higher heat conductivity, the flow rate of refrigerant in jacket should be increased, so energy consumption should be increased. Therefore, large beer fermenter using ethanol water as refrigerant should not be adopted.
　　According to the experience of using ethanol water as refrigerant, the cooling area is generally 80-120 M2 (130m2) cold wort. For ammonia, the refrigeration area is half. Fermentation technology requires faster cooling speed, larger cooling capacity and cooling area, and higher investment. Cooling mode usually uses 3-4 cooling sections, 2 or 3 sections of cylinder, 1 section of cone or no. The cooling area of each section accounts for 20% of the total cooling area, 25% of the middle section, 50% of the lower section and 5% of the cone.