Heat Transfer in Solar Water Heaters Pipes

This work introduces the development of formulas for heat transfer in solar water heater pipes to allow calculations of energy losses in pipes. Solar legislation in Israel requires the installation of solar water heaters in new buildings up to 9 floors from the roof. The legislation from the year 1980 is based on the technology of the late 70s. This publication compares the old types of installation (steel pipes) with the current common practice (2017) in Israel. Thermosyphonic systems are installed up to 4 floors below the roof, based on old beliefs regarding waste of time waiting for hot water, waste of water and energy losses in long pipes. This work analyzes the possibility of the installation of thermosyphonic systems on lower floors than the 4th floor under the roof. The results are energy losses, waste of time waiting for hot water and waste of water, depending on the pipe's length and distance to the apartment. This publication may be helpful for the techno-economic evaluation of water heating options and the determination of the optimum solutions. It also contains a large number of useful formulas, data and information and can serve as basic material for solar water heaters calculations.