Heat Transfer in Solar Water Heaters Pipes - Thermosyphonic Systems

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