In this paper, the effects of inlet temperature and rib height on the fluid flow and heat transfer performances of the ribbed channel inside the high temperature heat exchanger are presented. The inlet temperature varies from 850 K to 1250 K and the ratio of rib height to channel height varies from 0.083 to 0.333. The results indicate that increasing the rib height can enhance the flow disturbance and hence improve the heat transfer performance. The inlet temperature has little effect on the basic structure of fluid flow and the heat transfer is enhanced due to the increased velocity. Compared to increasing the rib height, more heat can be transferred by increasing the inlet temperature with less pressure drop. The high pressure drop is more serious as the inlet temperature increases. It is proposed to use the compact heat transfer structure at the low temperature region and replace it by loose heat transfer structure at the high temperature region. It also demonstrates that the Nusselt number and friction factor are unsuitable to compare the heat transfer and pressure drop performances among different temperature conditions because the physical properties of fluid change with temperature variation. (C) 2012 Elsevier Ltd. All rights reserved.