This work presents an analysis on heat transfer process occurred in the Trombe wall system with a new channel design in Yazd (Iran) on the coldest and warmest days of winter. The primary objective was to investigate the impact of heat transfer types, on the temperature variation of the Trombe wall back and absorber throughout the day. For this reason, the variations of Rayleigh number, convective heat transfer coefficient, and the rate of convection, conduction, and radiation heat transfer exchanged with the Trombe wall have been studied. The analysis of Rayleigh number variations for the channel inside revealed that there is a noticeable decrease in the early hours expressing a discernible decrease in the temperature difference between the absorber and the channel space. At night time, the absorber and channel temperatures drop approximately to the same value. Furthermore, the role of conduction transfer is more sensible than that of convection in the early and late hours. However, the convection dominates at the midday. It should be noted that due to new channel design, the radiation heat transfer rate is maximum in the early and late hours. The heat transfer is more significant on the coldest day because of higher temperature difference between the different parts of the Trombe wall system. (C) 2017 Elsevier Ltd. All rights reserved.