The thermal behaviors of a solar chimney incorporating with organic phase change material (PCM) RT-42 unit under different heat fluxes are studied in this paper. For the numerical model, effective heat capacity method is employed to analyze the performance of RT-42, while the average thermo-physical property approach is used to describe the PCM/fins component. The PCM behaviors during its melting and solidification processes, absorber surface temperature, mass flow rate, and inlet and outlet air temperature difference have been investigated. The numerical results give good agreements with the experimental results. The comprehensive investigations under various heat fluxes from 100 to 800 W/m(2) are carried out by using the verified model. The numerical results show that the performance of the system deteriorates sharply once the heat flux is or lower than 500 W/m(2), but not big improvement if the heat flux is higher than 700 W/m(2). Therefore, the performance of the system is highly dependent on the solar radiation. The application of high effective thermal conductivity enhancers can further improve the performance of the chimney under lower solar radiation. (C) 2014 Elsevier B.V. All rights reserved.