Permeate gap membrane distillation

A method comprising:

• receiving a feed stream comprising water in a hot medium compartment of a membrane distillation apparatus;
• receiving a cold medium stream in a cold medium compartment of the membrane distillation apparatus, wherein the membrane distillation apparatus comprises a permeate gap compartment intermediate of the hot medium compartment and the cold medium compartment;
• allowing, by a membrane disposed within the membrane distillation apparatus between the hot medium compartment and the permeate gap compartment, water vapor originating from the feed stream to pass from the hot medium compartment through the membrane to the permeate gap compartment while preventing liquid from passing through the membrane;
• rotating an impeller disposed within the permeate gap compartment, thereby resulting in mixing fluid within the permeate gap compartment, decreasing pressure on a side of the membrane facing the permeate gap compartment, and promoting heat and mass transfer within the permeate gap compartment;
• condensing, by a thermally conductive plate disposed within the membrane distillation apparatus between the cold medium compartment and the permeate gap compartment, the water vapor from the hot medium compartment that passed through the membrane to form a permeate stream having a water purity level greater than the feed stream;
• and
• discharging, by a permeate outlet of the permeate gap compartment, the permeate stream from the membrane distillation apparatus.

A membrane distillation system comprising:

• an apparatus comprising:
• a housing comprising:
• a first end;
• a second end opposite the first end;
• a hot medium compartment spanning from the first end to the second end, the hot medium compartment comprising a hot medium inlet and a hot medium outlet, the hot medium inlet disposed at the first end and configured to receive a hot medium stream comprising water;
• a cold medium compartment spanning from the first end to the second end, the cold medium compartment comprising a cold medium inlet and a cold medium outlet, the cold medium inlet disposed at the second end and configured to receive a cold medium stream;
• a permeate gap compartment spanning from the first end to the second end, the permeate gap compartment intermediate of the hot medium compartment and the cold medium compartment, the permeate gap compartment comprising a permeate outlet;
• a membrane spanning from the first end to the second end and disposed between the hot medium compartment and the permeate gap compartment, the membrane defining a plurality of pores sized to allow water vapor originating from the hot medium stream to pass from the hot medium compartment through the membrane to the permeate gap compartment;
• and
• a thermally conductive plate spanning from the first end to the second end and disposed between the permeate gap compartment and the cold medium compartment, the thermally conductive plate and the cold medium stream within the cold medium compartment cooperatively configured to condense the water vapor from the hot medium compartment that passed through the membrane, wherein the permeate outlet is configured to discharge the condensed water vapor from the permeate gap compartment;
• and
• an impeller disposed within the permeate gap compartment and connected to a rotatable shaft, wherein the impeller is configured to mix fluid within the permeate gap compartment in response to the rotatable shaft being rotated;
• and
• a motor coupled to the rotatable shaft, the motor configured to rotate the rotatable shaft in response to receiving power.