SIMULATION STUDIES OF THE POSITION OF THE AUXILIARY HEATER IN THERMOSIPHON SOLAR WATER-HEATING SYSTEMS

This paper investigates the effect of the physical location of the aux iliary source of energy in thermosyphon solar water heaters and shows that the performance of the system can be optimised with respect to th e geometry of the system components. The investigation has been based on a domestic thermosyphon solar water heating system, which was simul ated using the TRNSYS programme. The annual solar fraction of the syst em, at the weather and socioeconomic conditions of Cyprus, is, at best , approximately 77% with an in-tank auxiliary heater configuration and 86% with an external auxiliary heater. It is demonstrated that the ar rangement with the external auxiliary unit has a higher collector effi ciency and results in a higher annual solar fraction. In the case of i n-tank auxiliary, the system performance increases with the height of the auxiliary position from the bottom of the storage tank; with the a uxiliary at the bottom of the storage tank the annual solar fraction i s approximately 59%, compared to 77% when the auxiliary is located at the top of the tank. The system performance also depends on the height of the collector return from the bottom of the tank. Copyright (C) 19 96 Elsevier Science Ltd.