Experiments of boiling heat transfer to liquid helium is described. Variation of critical heat flux q_c with gap width and distance from inlet of cooling channel was measured. The gap widths of vertical channels, of rectangular cross section, were 1, 2, 3, 4, 5mm and open. The lengths of the channels were 5, 10, 20 and 40cm. Comparison of our experimental results with the data obtained by Wilson and Lehongre showed good agreement. By using simple assumptions, mechanism of heat transfer in channels was analysed qualitatively.
Also the results in the case of inclined channel are presented.