THERMOSIPHON CIRCULATION IN SOLAR WATER HEATERS INCORPORATING EVACUATED TUBULAR COLLECTORS AND A NOVEL WATER-IN-GLASS MANIFOLD

A study is reported of thermosiphon circulation in solar water heaters incorporating glass tubular evacuated collectors and a water-in-glass manifold of extremely simple design. The manifold is characterized by the absence of partitioning of the inner volumes of the absorber tubes into inlet/outlet channels and buoyancy effects are utilized to convey heat to a header pipe at the open end of the tubes. Solar energy input to the tubes has been simulated by electric heating. Thermosiphon flow has been measured for a number of system designs and a wide range of operating conditions. The relative impedances of the system components has been evaluated allowing optimization of the system design.