Influences for the Addition of Ethanol to the Absorption System on the Interfacial Disturbances and Mass Transfer Performance

To study the interfacial mass transfer phenomena of water vapor absorbed by TEG (triethylene glycol) and DEG (diethylene glycol) solutions, an absorption system was designed and tested in this study. The surface tensions of TEG and DEG solutions were varied by adding a liquid with lower surface tension to observe the interfacial disturbances and the mass transfer performance of the absorption system. In this study, ethanol was added to the absorbent solution. The traditional variable of driving force was replaced by the variable of surface tension times driving force to compare the variation of mass transfer coefficients of systems with and without ethanol added to the absorbent solution. The results showed that surface tension significantly affected the mass transfer performance in the gas−liquid interface. Both mass transfer coefficient and enhancement factors were calculated to analyze the effects of interfacial disturbance on mass transfer performance. The photographs showed that when ethanol was added to the surface of the TEG solution, the interfacial disturbance on the surface of the TEG solution was significant. The experimental results also demonstrated that the mass transfer coefficients were increased due to the addition of ethanol to the absorbent solution. The values of the defined enhancement factor were from 1.047 to 1.143 for the system with DEG solution and from 1.064 to 1.161 for the system with TEG solution. Both driving force and surface tension were important physical properties that affected the mass transfer phenomena of the absorption system. The interfacial disturbance resulting from the addition of ethanol to the absorbent solution can be used to enhance the mass transfer performance for absorption heat pump and absorption air-conditioning systems.