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Journal of Membrane Science, 1998
A method is proposed that permits to evaluate the net membrane distillation coef®cient. The metho... more A method is proposed that permits to evaluate the net membrane distillation coef®cient. The method, which completes and is based on a model previously reported, emphasizes the in¯uence of the unstirred boundary layers on the membrane distillation processes. The searched coef®cient is obtained from a set of measurements of thermally driven¯uxes, osmotically driven¯uxes, and thermally and osmotically driven¯uxes. The theory has been applied to the results obtained with two porous hydrophobic membranes, in different experimental conditions. The experiments show that the net coef®cient decreases with the mean temperature and permits to quantify the temperature polarization effects. In addition, the heat of vaporization of water may be estimated. # 1998 Elsevier Science B.V.
Journal of Membrane Science, 1996
A theoretical approach is presented that describes membrane distillation processes due to the sim... more A theoretical approach is presented that describes membrane distillation processes due to the simultaneous action (in a proactive or in a counteractive way) of temperature and concentration differences through porous hydrophobic membranes. The model developed emphasizes the importance of the boundary layers, shows the existence of a coupling term between the two thermodynamic forces acting on the system, and permits the definition and characterization of the so-called steady states. In order to check the model, two membranes have been studied in different experimental conditions. The influence of some relevant parameters, such as solution concentration, stirring rate, mean temperature and temperature difference has been considered and the theoretical predictions of the model have been applied to the obtained results. The accordance may be considered good.
Journal of Membrane Science, 1998
A method is proposed that permits to evaluate the net membrane distillation coef®cient. The metho... more A method is proposed that permits to evaluate the net membrane distillation coef®cient. The method, which completes and is based on a model previously reported, emphasizes the in¯uence of the unstirred boundary layers on the membrane distillation processes. The searched coef®cient is obtained from a set of measurements of thermally driven¯uxes, osmotically driven¯uxes, and thermally and osmotically driven¯uxes. The theory has been applied to the results obtained with two porous hydrophobic membranes, in different experimental conditions. The experiments show that the net coef®cient decreases with the mean temperature and permits to quantify the temperature polarization effects. In addition, the heat of vaporization of water may be estimated. # 1998 Elsevier Science B.V.
Journal of Membrane Science, 1996
A theoretical approach is presented that describes membrane distillation processes due to the sim... more A theoretical approach is presented that describes membrane distillation processes due to the simultaneous action (in a proactive or in a counteractive way) of temperature and concentration differences through porous hydrophobic membranes. The model developed emphasizes the importance of the boundary layers, shows the existence of a coupling term between the two thermodynamic forces acting on the system, and permits the definition and characterization of the so-called steady states. In order to check the model, two membranes have been studied in different experimental conditions. The influence of some relevant parameters, such as solution concentration, stirring rate, mean temperature and temperature difference has been considered and the theoretical predictions of the model have been applied to the obtained results. The accordance may be considered good.