The evaporation characteristics of n-heptane droplets with varying concentrations of aluminum (Al) nanoparticles (NPs) hanging at a silicon carbide fiber were studied experimentally at different environmental temperatures (100-600 degrees C) under normal gravity. The evaporation of pure and stabilized heptane droplets has been also examined for comparison. The characteristics of the shell formation due to evaporation of the NPs suspensions and its effects on evaporation rate were also investigated. The results show that the evaporation of suspended heptane droplets containing Al NPs follows the classical d(2)-law at all temperatures. The phenomenon of bubble formation in stabilized heptane droplets is reduced with the addition of Al NPs. For all Al NPs suspensions; regardless of their concentrations, the evaporation rate obtained was lower than pure heptane droplets from 100 to 300 degrees C, but it monotonically increased and became higher than the evaporation rate of pure heptane droplets above 400 degrees C. However for 2.5% (by weight) Al NPs suspension, the increasing trend in evaporation rate is exponential above 400 degrees C. At relatively low temperatures the formation of large agglomerates results in a compact shell development which suppresses the evaporation. On the other hand, at high temperatures a highly porous shell was formed by small agglomerates so that Al NPs lead to evaporation enhancement. Maximum reduction of similar to 15.5% in the evaporation rate at 200 degrees C with 5% Al NPs and maximum increase of similar to 50% in the evaporation rate at 600 degrees C with 2.5% Al NPs suspension was observed. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.