The aim of the present study is to investigate convection heat transfer and fluid now in an insulated rectangular cavity, i.e., an indoor with the injection and suction ducts. Emphasis is placed on the effect of a vertical partition plate in the cavity on the thermal and velocity fields and local area heating-performance. The numerical method is based on the incompressible Navier-Stokes and energy equations. The fluid in the cavity in the absence of the vertical partition plate shows the large clockwise now Pattern and as time progresses, the fluid temperature is gradually increased and becomes uniformly over the whole region of the cavity. When the vertical plate is installed at the central location of the upper horizontal wall, the higher velocity field appears in the left area of the indoor and the corresponding fluid temperature is higher than that of the right area. By installing the partition plate, the temperature distribution in the indoor is controlled. In other words, only the desired space of the cavity is warmed, because the flow pattern is changed due to the presence of the plate. The optimum partition plate height is obtained based on the numerical and experimental results.