The objective of this study was to analyze the heat transfer and fluid flow within a closed cavity, which usually enhance by application of Nanofluids. The movement of the Nanofluids within the enclosure were governed by Buoyancy force and Gravitational force. Different kinds of Nanofluids were employed for purpose of examining the motion of heat flow and the stream line formation, within the close cavity. The closed cavity considered for this study comprised of a flush mounted heater on the left wall, the right wall was maintained at a constant temperature throughout the investigation and the top & bottom wall were kept insulated. In this study, MATLAB was used for performing the simulation and solving the fundamentals of Computational Fluid Dynamics (CFD), namely the Energy equation and the Momentum equation. The analysis to estimate the heat transfer and fluid flow in a closed cavity by the use of different Nanofluids have been presented in terms of several parameters such as Rayleigh number, Nusselt number, Aspect ratio and Volume fraction respectively.