Abstract: A heat exchanger apparatus has a center pipe and an outer pipe formed with spiralling grooves attached to the outside of the center pipe. The outer pipe grooves are pressed against the center pipe to form a spiralling passageway around the center pipe between the center pipe and outer pipe. The center pipe has spiralling grooves co-acting with the outer pipe spiralling grooves so that a portion of the outer pipe grooves fit in the center pipe's grooves. Fluid passing through the center pipe has a predetermined turbulence created therein. Cooling fins are mounted in the grooves of the outer pipe in contact with the groove walls to remove heat from both the center pipe and the outer pipe. Special end couplers are provided for connecting the end of the heat exchanger to a liquid input or output for both the center pipe and the outer pipe separately. A coupler for connecting abutting heat exchange units connects the center and outer pipes separately to make longer lengths.

Abstract: A solar heating panel apparatus has a supporting base with a plurality of elongated heat exchanger members mounted to the base. Each heat exchanger is operatively connected to one end of an adjacent heat exchanger to provide a continuous path through the heat exchangers from a fluid input to a fluid output. Each heat exchanger has a hollow center core having a passageway running spirally around the center core and uses the center core as one wall of the spiralling passageway. The fluid flows through the spiralling passageway, and may flow through the center core, although the center core may also be used to enclose heating elements so that the solar panel can be used without benefit of a conventional hot water heater.