Heat and mass transfer evaluation of air-gap diffusion distillation by ε-NTU method

The effectiveness-number of transfer units (e-NTU) method was used to develop the heat and mass transfer model of air-gap diffusion distillation (AGDD). In this model, the latent heat transfer of vapor in air-gap was regarded as an equivalent convective heat transfer to make a relationship with NTU. Compared with the full numerical model developed in our previous work, the new model was simple and performing with dramatic high computational efficiency. The accuracy of the model was as well as the full numerical model. The influences of structure and operation parameters on the performances of AGDD system were discussed furtherly by employing the model. Results shown that the air-gap height, the inlet temperature and feed flow rate of hot stream could be regarded as the strong parameters effected significantly on the performances of the system in comparison with the air-gap thickness and inlet temperature and salt concentration of cold stream. Therefore, these strong parameters should be considered firstly for improving the heat and mass transfer of AGDD.