top 68 inner frame arms 70 are located within loops 32 and are joined to outer frame arms 66 by fasteners 72 outer frame arms 66 and inner frame arms 70 surround lower heat exchanger section 46 and may be formed from heat conducting metal tubing identical to the tubing of upper heat exchanger section 44 frame 62 maintains the shape of coils 32 in lower heat exchanger section 46 if desired fame 62 may only extend around lower heat exchanger section 46 frame 62 may include only one set of frame arms 66 or 70 and include stainless steel or monel brand stainless metal alloy fasteners to secure portions of heat exchanger section 46 to frame 52 to maintain the shape of coils 32 frame 62 may be made of metal tubing and incorporated into upper heat exchanger section 44 the operation of heat exchanger assembly 10 will now be described tank 14 is filled with heat storage liquid 60 heat is transferred to and from liquid 60 through heat exchanger 12 heat rises in liquid 60 so that liquid at the top of tank 12 is hotter than liquid at he bottom of the tank to transfer heat energy into liquid 60 heat exchange liquid 58 is heated outside of tank 12 by solar energy combustion electricity or other means and flowed through line 54 and into heat exchanger 12 through first end.