Thermal management of fuel is very important for the cooling system of an advanced engine. In order to study the 3-D phenomena of fuel flow with cracking reaction in the cooling channels and their effect on the utilization of fuel heat sink, numerical models of cracking fuel flow in an asymmetrically heated rectangular tube are built on the basis of the real fuel thermophysical properties using commercial software and validated through experiments in a conversion range from 0% to 76%. The simulation results indicate that the velocity, temperature and conversion of fuel flow exhibit a clear nonuniformity in the cross-section of the rectangular tube, causing the nonuniformities of physical and chemical heat sinks. Compared to the situation without chemical reaction, due to the fact that chemical reaction can slightly reduce the nonuniformity of temperature field, the nonuniformity of physical heat sink resulting from the temperature field can be slightly reduced. However, the nonuniformity of total heat sink can be dramatically reduced by chemical reaction because the chemical heat sink is one of the major components of total heat sink, and unlike physical heat sink, chemical heat sink shows much less nonuniformity under the influence of both temperature and velocity. (C) 2014 Elsevier Ltd. All rights reserved.