Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.
The direct contact membrane distillation process is used for
water desalination. DCMD is a thermally driven separation
process, in which only vapor molecules transfer through a
microporous hydrophobic membrane. The driving force in the
DCMD process is the vapor pressure difference induced by the
temperature difference across the hydrophobic membrane.
In this study, the one-dimensional based model is developed
for predicting the performance of the seawater desalination to
produce fresh water for hollow fiber type DCMD module. The
mass, energy and momentum balance equations are coupled to
determine the concentration of NaCl, the temperature and
velocity distribution of the feed and permeate side along the
module length, and productivity of fresh water in the DCMD
process. The KMPT model is used to calculate the mass
transfer at the membrane surface. The mathematical and
kinetics models used in this study are validated in comparison
of the present simulation results with previous data given in the
literature. The simulation results are in good agreement with
the data in the literature. The performance of pure water
production rate with respect to the membrane distillation
coefficient is compared with the previously reported data.
The numerical analysis is performed on a DCMD module
using hollow fiber type PVDF membrane with a pore size of
0.22 μm. Feed solutions are aqueous NaCl solution. The values
of the parameters considered in this work are: feed temperature,
40-70 ; feed velocity, 0.472m/s to 0.55m/℃ s; mass fraction of
salt, 0.025-0.05; cold permeate temperature, 17-45℃ and the
velocity of the permeate side are 0.3 m/s. It is found that the
production rate of fresh water increases with feed temperature
and velocity, but decreases with feed concentration.
