The heat flux and fluid flow conditions for a water cooled limiter tube are simulated with an electron beam heating apparatus, and the results are compared to empirical models based on existing heat transfer correlations. For the conditions of highly subcooled flow boiling in a horizontal tube subjected to a heat flux from only one side, two principal observations were noted. First, existing heat flux correlations, which were developed for use with uniform circumferential heat flux distributions, can be used to provide a good first approximation of the one-sided heat removal for the range of experimental conditions covered. Second, the peak heat flux at the tube surface predicts the onset of critical heat flux (burnout) better than the average heat flux.