The drag of airplane radiators with special reference to air heating : comparison of theory and experiment
A 1939 NASA technical report, compiled from a German aeronautical study, on the drag of aircraft radiators and the effect of heating the air passing through them, comparing theory with experiment for engineers. Its pictures are dense technical charts of pressure drop and efficiency curves, plus a section diagram and heated tube notation sketch, with fanned families of curves and labelled axes that a designer could use as abstract line-graph textures or grid patterns.
