In an air-cooled graphite channel in which heat is being generated by oxidation, the length of channel cooled is a function of the heat transfer coefficient. No diameter effect other than that accounted for by the heat transfer coefficient was observed. Cooling rates and temperature differences (between the graphite and air) vary very slowly in the cooled section of the channel. Temperature changes vary rapidly with time in the section of channel in which more heat is generated than is removed by the air stream. These changes do not affect the cooled section of channel.