A partially hydrophilic fluoro-carbon composite membrane was tested for sea water desalination. The permeate flux increases with an increase in flow rate of brine and/or cooling water, as well as with an increase in temperature differences between brine and cooling water. The thermal efficiency also increases as the temperature difference increases. Comparison of the fluoro-carbon membrane with the silicone membrane revealed that the permeability and thermal efficiency of the fluoro-carbon membrane were superior to those of the silicone membrane.