Synopsis Measurements of heat fluxes to boiling helium from the surface of normal metal in the simulated cooling channel of superconducting pancake coil have been made. Critical heat fluxes Qn and Qf are presented as a function of gap width d for both horizontal and vertical channels. In the vertical channel Qn is independent of d down to 0.05mm unlike the other results of narrow channel experiments. Additive vapor experiments shows that the Qn for downward surface is greatly affected by extra vapor in the liquid.