The passive containment cooling system (PCCS) is one of the main passive safety systems in the advanced pressurized water reactors and small modular reactors (SMRs). As per International Atomic Energy Agency (IAEA), SMRs are the advanced nuclear reactors that have capacity of up to 300 MW(e) per unit. PCCS utilizes natural phenomena to remove the residual heat released from the reactor to the containment during the accidents, for preventing the overpressure of the containment shell. The design pressure of the containment shell, vary from reactor to reactor, depending on the capacity and design of the reactor. The design pressure values for steel containments are higher than concrete containments and are generally greater than 5 bar. To maintain the pressure of the containment during accidental conditions it is important to have reliable PCCS. It is necessary to evaluate the PCCS performance with suitable numerical methods backed by experiments. This paper provides the details of the experimental test facility developed with an aim of providing an understanding of the containment cooling phenomenon and its capability of heat removal by the natural draft of air between the containment and chimney. The pre-test results are obtained from analytical model which is further benchmarked with the best estimate thermal-hydraulic code RELAP5/MOD3.2. The heat removal rate, air outlet temperature, air mass flow rate and overall heat transfer coefficient, obtained from analytical model and RELAP were found to deviate within 1.06%, 0.65%, 6.15% and 6.14% respectively. From the study, it was found that the heat transfer rate of 600 W from the containment, almost doubles by using chimney to 1.27 kW. The optimum value for the hydraulic diameter was found to be 0.825 m. The heat transfer rate was found to increase with increase in chimney height, containment wall temperature and with decrease in air inlet temperature.