The transient critical heat fluxes (CHFs) were measured for water flowing in a small vertical tube with exponentially increasing heat inputs. A stainless steel tube (SUS 304) with an inner diameter of 1.0 mm and a length of 47.4 mm was used as a test tube, which was mounted vertically in the experimental water loop. In the experiment, the upward flow velocity ranged from 9.4 to 13.4 m/s and the inlet sub cooling ranged from 85 to 145 K. The heat generation rate was exponentially increased as a function of Q(0)exp(t/tau). The period of the heat generation rate was ranged from 82 ms to 30 s. Experimental results indicated that the CHFs increased with decreasing period of heat generation rates and increasing flow velocity. For shorter periods of the heat generation rate, the CHFs were significantly higher. The CHFs were affected by the period of the heat generation rate and flow velocities. The empirical correlations of the transient CHFs for the small tube were obtained based on the experimental data. (C) 2016 Elsevier Ltd. All rights reserved.