One of the alternative sources of energy is solar energy which is available in abundance throughout
the world. The energy contained within the solar rays is capable of starting natural convection within
closed mechanical systems containing a suitable working fluid. One such system is commonly known
as a Thermo-syphon which transfers solar energy into internal energy of the working fluid, commonly
water. In the present study, an attempt has been made towards better understanding of the flow
structure within a thermo-syphon by analysing the natural convection phenomenon using
Computational Fluid Dynamics based techniques. A commercial CFD package has been used to
create a virtual domain of the working fluid within the thermo-syphon, operating under no-load
condition. The effects of the condenser volume, on the performance of the thermo-syphon, have been
critically analysed in this study. The results depict that as the condenser volume increases, the
average temperature of water within the condenser decreases. Hence, CFD can be used as a tool to
design, analyse and optimize the performance of a thermo-syphon with reasonable accurac
