沼气池内PEX螺旋盘管换热性能实验研究

EXPERIMENT STUDY ON HEAT TRANSFER CHARACTERISTICS OF PEX COIL HEAT EXCHANGER IN BIOGAS DIGESTER

建立PEX螺旋盘管加热沼气池的实验平台,对影响盘管换热的运行参数(热媒入口温度、平均流速)和设计参数(螺旋管直径、螺距)进行实验研究。对比分析不同因素对沼气池内温度变化、盘管换热量和传热系数等参数的影响。结果表明:入口水温对螺旋盘管换热性能的影响大于管内平均流速,提高螺旋盘管入口水温可显著缩短沼气池的预热时间,将入口水温由40℃升至70℃后,对应的预热时间由15 h以上缩至5.4 h;螺旋盘管的平均传热系数随螺旋直径的增大、螺距的减小而减小;改变螺旋直径对水平方向上的沼液温度分布影响较小。

The influence of operating parameters(heat medium inlet temperature and average flow velocity)and design parameters(screw diameter and pitch)on heat transfer characteristics of coil heat exchanger in biogas digester is studied through experiment. The effects of different factors on the slurry temperature change,coil heat flux and heat transfer coefficient are analyzed. The results show that the inlet water temperature of coil heat exchanger has more influence on its heat transfer performance than of the flow velocity. To increase the inlet water temperature can significantly reduce the preheating time of biogas digester. The inlet heat medium temperature is increased from 40 ℃ to 70 ℃,then the corresponding preheating time is reduced from 15 h to 5.4 h. The average heat transfer coefficient decreases with the coil diameter increased and the pitch decreased,the coil diameter change has little influence on the temperature distribution of the slurry in the horizontal direction.