Core determination of present work is to analyze the influence of nanoparticle of Copper (H) oxide within the base fluid (water) enclosed in a partially heated rhombus shaped cavity. A square cylinder is fixed at the center of rhombus and kept fix with the uniform heat. For thermal management of enclosed nano fluid, various conditions are adjusted at the walls of rhombus in such a way that bottom side is heated and upper mean side is adiabatic, while rest of the portion is kept cold. Effective thermal conductivity and viscosity of nanofluid is used in term of static and Brownian via KKL approach. The governing partial differential equations are first converted into the dimensionless form using the variable transformation. Then numerical solution of the model is obtained using Finite Element Method (FEM). Simulation is performed for different heated portion of bottom length (L), Rayleigh number (Ra), nanoparticle volume fraction (phi) and three kind of heat conditions (cold, adiabatic and hot) at the surface of inner square cylinder. In order to check the rate of heat transfer within the entire cavity, various heated lengths are considered for rhombus. Performance of temperature and velocities (along x and y-directions) is computed at the mean position of the cavity. Significant influence of inner heated square cylinder is found and it is determined that cold square cylinder resist the influence of heat transfer in the entire domain of the cavity. (C) 2017 Elsevier Ltd. All rights reserved.