Imagen a pulse jet, optimised for heat production, blowing down wards through the throat of a venturi tube, witch also has a large volume of 'hot' seawater pumped into it.
The volume of water being controlled such that the temperature down steam of the venturi is a little over 100 degrees centigrade.
At the throat of the venturi the pressure is less than atmospheric pressure, and the temperature is hot enough to boil that volume of water even at atmospheric pressure, so all of the water flash boils.
This venturi would need to have a very much larger down stream cross sectional area than its up stream cross section.
As the resulting steam moves passed the narrowest part of the venturi the now suspended salt will condense water on to itself to form a salty saturated steam.
This steam is passed quickly into a large cyclonic separator (think of a Dyson vacuum cleaner ) the salt water will easily separate and run out at the bottom.
Steam is very much lighter then air ( clouds float in the sky, even though they contain hundreds of tones of water ) so with careful design most of the air and exhaust gasses from the venturi can be remove at this stage also.
The resulting clean steam can by condensed and the heat used to produce hot sea water.
Because the salt 'forms in mid air' and then quickly dissolves in boiling water there will be little or no scaling, the killer of most desalination systems.
Give the large difference between the pulse jet temperature and the roughly 100 degrees as the exhaust leaves the system something thermally efficient is happening.