Analysis of heat transfer efficiency and rate inside fermentation tank with heating coil of biogas projects

Heating coil inside the tank is widely used in biogas projects at home and abroad. The various factors affecting the heating and heat transfer of the tank were analyzed from the heat transfer efficiency and rate based on the first and the second laws of thermodynamics. It was found that from the view of the overall heat transfer coefficient, the thermal conductivity and wall thickness were comprehensive considered and then the maximum heat transfer rate was obtained with low speed mixing method by choosing the thick wall with the value of thermal conductivity of above 15 W·m^-1·K^-1. Meanwhile, the energy consumption of transfer process was analyzed from the view of heat transfer efficiency. It can be obtained that an appropriate increase in the inlet temperature of cold material can reduce the irreversibility of heat transfer and increase the utilization ratio of limited energy for heat transfer process with countercurrent mixing. Therefore, the high-efficient, energy saving and rational theoretical guidance was provided for biogas project using tank heating to achieve the unity of transfer heat rate and efficiency.