Abstract: Disclosed is a heat exchanger, and a method for heating a working fluid. The heat exchanger includes a burner, a combustion section, and a condenser section positioned below the combustion section such that exhaust from the burner passes through the spiral coils and to the condenser. In an example of this disclosure, the combustion section includes a plurality of spiral coils radially spaced apart relative to one another, and the condenser section includes a plurality of U-bend coils.
Abstract: Disclosed is an economizer including a plurality of coil stacks. Each coil stack includes a tube coiled such that adjacent layers of the tube contact one another in a radial direction. Further, the coil stacks are axially spaced from one another to allow exhaust to flow between adjacent coil stacks.