water header 30 in turn the headers 29 are fed through a main hot water distribution manifold 31 likewise all cold water headers 30 are connected to the main collector 32 the coils are again shown in fig2 this arrangement has various advantages 1 the thermal expansion problem of the plastic materials is completely eliminated because the free standing and particular configurations of the spring coils absorb the thermal elongations or contractions 2 because the fluid follows the circular pattern of the spring shape coils the turbulence is greater than when it flows in linear pipes thus this has a very significant effect on the overall heat transfer coefficient enabling to reduce the heat transfer surface 3 the height between the hot water and cold water headers is about 4 feet however the actual length of the coil can be about 50 feet this reduces the amount of connections between headers 29 30 and coil assembly 20 4 as the open circuit water flows down by gravity it tends to form a film over the coils and spins down washing off any adherences the pipe may have the invention also ran tests in a 34 cross flow tower 34 of the type shown in fig2 in that instance the coils used were of the design described in fig1 c the hard cores 22 layed on plastic racks 33 giving the coil freedom of movement for thermal expansion fig2 d shows the thin wall pipe in a collapsed position once the water has been drained fig2 a through 24c illustrate thin plastic film heat exchange panels incorporating the invention vacuum formed films high density thin films polyethylene 0 006 34 filmss were vacuum.