渗透汽化膜过程乙醇水蒸气真空分馏热质传递

Mass transfer and heat transfer behavior of ethanol-water vapor in vacuum condensation dephlegmator during pervaporation membrane process

对透醇选择性渗透汽化膜下游的渗透蒸气进行分级冷凝,重点研究了真空冷凝分馏器的热-质传递行为,分析了进口渗透蒸气流速对真空冷凝分馏器传热系数与冷凝行为的影响.进口蒸气流速从3.09 m/s提高至8.05 m/s时,总传热系数由37.06 W/(m^(2)·K)提高至145.27 W/(m^(2)·K),渗透蒸气侧冷凝给热系数也由55.81 W/(m^(2)·K)提高至544.60 W/(m^(2)·K).不同流速下,传热过程各步骤热阻占比不同,3.09 m/s时,渗透蒸气侧热阻占比较大,高达82.99%;流速提高至8.05 m/s后,冷却介质侧热阻占比增大,达到65.66%.随进口蒸气流速的提高,真空冷凝分馏器中蒸气冷凝量在总渗透蒸气中的占比由41.82%提高至68.19%,乙醇质量分数由3.45%提高到10.66%.

Fractional condensation process was used to recover the permeate ethanol-water vapor downstream the pervaporation membrane under vacuum.The heat transfer and mass transfer behavior of the vacuum condensation dephlegmator was stressed.The effects of inlet vapor flow rate on the heat transfer coefficient and condensation behavior of the vacuum condensation dephlegmator were analyzed.When the inlet vapor flowing velocity was increased from 3.09 to 8.05 m/s,the heat transfer process was effectively intensified.The total heat transfer coefficient was increased from 37.06 to 145.27 W/(m^(2)·K),with the vapor side condensing heat transfer coefficient also increasing from 55.81 to 544.60 W/(m^(2)·K).At different flowing velocity,the proportion of thermal resistance in the heat transfer process varied.At low vapor flowing velocity,the vapor side thermal resistance was relatively high,reaching up to 82.99%.After the flow rate increased,the proportion of thermal resistance on the cooling medium side was increased,reaching up to 65.66%.With the increase in feed flowing velocity,the recovery proportion of ethanol-water vapor in the vacuum condensation dephlegmator was improved from 41.82%to 68.19%,with the ethanol recovery proportion increasing from 5.21%to 30.72%.The ethanol mass fraction in the first condensate was also increased from 3.45%to 10.66%.