Air-coolers for high power vacuum tubes

High power air-cooled tubes require well designed coolers of the extented surface type. Moreover, it is essential to carry these heat transfer design considerations in parallel with the electronic design so that a tube evolves which will operate at its "electronic" rather than its "heat transfer" rating. The objectives of this paper are to present the factors relating to the heat transfer design of an annular air-cooler of the axial-flow type, it which the extended surface consists of a large number of radial fins. Performance equation derived from basic heat transfer and fluid flow theory are presented; application of the theory is illustrated by a specific design; and the validity of the design method in demonstrated by results of test. Some problems requiring further analysis and experimental work are also considered briefly.