Abstract: A heat exchanger includes a plurality of generally planar spiral flow channels in a stacked, generally parallel array for accommodating a first fluid. Each spiral flow channel terminates in an inner end at an axial core area of the heat exchanger. Flow channels are sandwiched between the spiral flow channels for accommodating a second fluid in heat exchange relationship with the first fluid. Relatively rotatable tubes extend axially of the core area and have radial openings in axial registry with the inner ends of the spiral flow channels. Relative rotation of the tubes vary the overlapping relationship of the tube openings and thereby vary the flow to the spiral flow channels.

Abstract: A heat exchanger is provided with a first conduit which utilizes a reverse spiral concept and a second fluid conduit which directs a fluid in thermal communication with the first conduit. One of the fluid conduits of the heat exchanger is formed with a generally S-shaped portion which creates a reverse spiral configuration and which permits a heat exchanger to take advantage of the spiral conduit design while avoiding the typical disadvantages that are generally experienced with spiral conduit configurations. The reverse spiral concept permits both ends of the reverse spiral tube to be easily accessible from a radially outward direction relative to the spiral configuration.