Large temperature gradient and local hot spot in solar receiver seriously impact the operation safety and thermal performance. To improve the temperature uniformity of porous foam absorber in a volumetric solar receiver, this work presents a receiver with an annular inner window to reshape the fluid field in the receiver. To examine the improvement effect of the proposed receiver, one numerical model is developed to analyze the coupled heat transfer in the receiver. The model takes the propagation of concentrated solar irradiation and thermal radiation in the consideration by using the Monte-Carlo ray tracing method. The effects of the inner window on the fluid flow and temperature distribution of the absorber as well as the efficiency of the receiver are analyzed. The results show that the standard difference of temperature in absorber of the proposed receiver is 35-158.6 K lower than that of the single windowed one, and the thermal efficiency is increased by 2.86%-7.18%, within the inner radius of the annular window range of 15-45 mm and flow rate of 4-7 g/s. It is demonstrated that installing an annular window is an effective approach to improve the uniformity of absorber temperature while increasing the thermal performance. (c) 2021 Elsevier Ltd. All rights reserved.