Present study, examines the phenomena of natural convection flow in a partially heated trapezoidal cavity loaded with the nanofluid in the presence of Single Wall Carbon Nanotubes (SWCNTs). A modified model for effective thermal conductivity of carbon nanotube is used to develop the governing partial differential equations. Thermal management within the cavity is controlled via two simultaneous features: one is to use the partially heated bottom wall and other is to use conductivity of Carbon particles. Most significant and physical conditions are adjusted at the inclined walls of the trapezoidal cavity to obtain the behavior of stream lines and heat management. The Gelerkin finite element method is implemented to solve the dimensionless form of PDEs. Simulations are performed for the different lengths of the heated portion (0.3 <= L <= 0.7), various choices of Raleigh number (10(4) <= Ra <= 10(7)) and volume fraction (0.0 <= phi <= 0.2). Flow field and thermal field are visualized through streamlines and isotherms. Moreover, results are obtained for Nusselt number over partially heated wall, temperature and velocity distribution over the mean position of the cavity. It is found that, by reducing the length of heated portion, flow filed is getting stronger but thermal depicts the opposite trend inside the cavity. Variation of Raleigh number also has significant influence on flow and thermal field. Conduction was dominant at low Ra but later on convection was found to be dominant for large choice. Fluid circulation was stronger and heat transfer rate was very slow at low viscous effects. From the graph it is clear that greater heat transfer will be occurred in the presence of nanofluid as compared to the based fluid water. Similarly velocity distribution of water is dominant as compare to the nanofluid. (C) 2017 Elsevier Ltd. All rights reserved.