The effect of air-passage length on the optimum fin spacing for maximum cooling
This is a 1938 NACA technical report from the NASA Technical Reports Server, a research memorandum on engine cooling written for aeronautical engineers and aircraft designers. Its pictures are plain line graphs and engineering sketches: temperature curves plotted against angle around a cylinder, cross-sections of cylinder fins and baffles, and airflow diagrams with streamlines. A designer might take from them the clean, labelled chart style and the simple line-drawn method of showing airflow around round forms.
