view similar to fig1 showing a system particularly intended as adapted for use in connection with geothermal wells and the like and employing an upright outer shell casing or tubing and an inner heat exchange tubing similar in many respects to what is shown in my application ser no 306 183 filed nov 14 1972 and in divisional application ser no 581 849 filed may 29 1975 fig1 separate flow paths for the hot aqueous fluid oil mixture and for the circulating coolant fluid are described as follows a hot aqueous fluid oil mixture any type of aqueous fluids containing dissolved solids only or both dissolved and entrained solids with or without entrained water vapor subject to precipitation of solids when cooled and or expanded to a lower pressure is suitable for this method of handling without formation of scale on contacting surfaces this aqueous fluid feed from source 1 is mixed with oil at oil entry zone 2 conveyed through fluorocarbon polymer lined feed conduit 3 to enter the outer heat exchanger shell 5 at inlet 4 the conduit 3 is fluorocarbon lined to prevent adherence of solid which form as the aqueous fluid loses temperature the oil aqueous fluid mixture flows in turbulent flow to maintain dispersion of the oil throughout the aqueous fluid through the annular space between the outer shell 5 and the inner fluorocarbon resin coated heat transfer tube 6 the tube 6 may be made of more than one tube joined.