Abstract: An integrated system and the process of its manufacture for the absorption of solar energy and for the release of that energy for utilization as required using modular elements that are pre-cast out of low-cost building materials and which can be designed for use with others of the like kind to form structural components of buildings, patios and walkways, and other areas of human activity. Each of the modules has labyrinthine integral passageways cast therein through which a fluid is circulated for the transfer of absorbed energy therefrom. The modules can be combined into a system forming walls of a building in which the outer elements act to absorb solar energy which is transferred to intermediate elements for thermal storage with means being provided to transfer stored energy on demand into interior elements for release of the energy into the interior of the building.

Abstract: A system having a tube-in-tube heat exchanger comprising three coaxial tubular members fitted one within the other with manifolding at each longitudinal end of the exchanger for the circulation of fluid through the outside tubular member in a counterflow direction to fluid passing through the inside tubular member such that heat is exchanged therebetween. A fluid is provided in the intermediate tubular member such that a leak in either the outer or inner tubular members can be detected. Each of the tubular members has integral radially inwardly projecting fins in its bore, the fins of the outer member being in good thermal contact with the intermediate member whose fins, in turn, are in good thermal contact with the inner member such that an effective heat flow path therebetween is provided.