  The present study investigates the effect of inclination on the buoyancy
driven systems. A cavity, Natural Circulation Loop (NCL) and Coupled Natural
Circulation Loop (CNCL) have been used to represent the possible classes of
buoyancy driven systems. There are extensive studies on the cavity systems
which exhibit a heat transfer coefficient jump upon the change in the
inclination as the system moves from one steady state to another. The primary
objective of the present study is to investigate if a similar behavior occurs
in natural circulation systems such as an NCL and a CNCL, using a 2-D CFD
study. The study identifies a combination of flow pattern rearrangement and
flow direction reversal as the phenomena responsible for the jump in the heat
transfer coefficient. A 3-D CFD study is also conducted to demonstrate the
universality of the phenomena. The CFD study is validated thoroughly with the
numerical and experimental data available in the literature. A parametric study
is also conducted to examine the effects of the aspect ratio, Rayleigh number,
Prandtl number and the inclination with the plane of the NCL system.
