Patent ID: 7440280

Claim:
An apparatus comprising: a heat exchange structure comprising a plurality of elongated air ducts, the heat exchange structure having an exterior heat exchange surface and interior heat exchange surfaces, the interior surfaces being in the elongated air ducts; and a plurality of heat generators that are distributed on the exterior heat exchange surface along an elongated direction of the air ducts, such that in operation of the heat generators, air flowing in the air duct is heated successively by heat from the heat generators, the air flow in the air duct being enhanced by buoyancy of heated air, wherein the heat exchange structure comprises a structural section and a thin layer of ceramic material attached to a surface of the structural section, the thin layer of material having a thickness less than 100 microns, and the thin layer of ceramic material comprises a first sub-layer that is substantially impermeable to air molecules and a second sub-layer that is at least partially permeable to air molecules.