A SOLAR COLLECTOR WITH ABSORBER COMPRISING A PLURALITY OF SPIRALLY COILED TUBES DEFINING NON-COINCIDENT SURFACES

A solar collector includes an absorber comprising a bundle of parallel or series connected coiled tubes (10, 11, 13), each tube being spray coiled so as to define a rotational surface, at least the surfaces relative to two tubes being non-coincident, preferably the coils of two tubes being axially offset to each other. Preferably the tube coils are partially inserted between each other. The collector comprises a preferably double wall envelope (18), with a vacuum gap and possibly containing a reflecting screen (17). Preferred materials for the outer envelope are polycarbonate or methymetacrylate; for the coiled tubes (10, 11, 13) a heat stabilized technopolymer with a colour absorbing the solar rays. The envelope (18) may comprise two coaxial bells (18 min , 18 sec ) connected by interfitting flanges. A fluid, generally a liquid, may circulate within the tubes of the bundle, while an air circulation (inlet 25, outlet 26) may be provided in the space between said tubes (10, 11, 13) and envelope (18), so as to provide a hot air output.