Another heat exchanger used for small systems is the coil-in-tank. (Figure 2-23) In
this type, a coil is immersed in the storage tank itself. Heated solar fluid is pumped
through the coil. The tank water surrounding the coil is continually heated and rises
by natural convection.
Tanks fitted with heat exchangers are made with both double and single wall
exchangers. Be sure to use a non-toxic solar fluid whenever the heat exchanger is
Most coil-in-tank units feature a finned outer surface to improve heat transfer. In
many cases, the inside of the coil is textured to further improve performance.
2.7 COMPONENT OPERATION