From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Comparison of radiator tube designs, including round, square, and hexagon shapes, for efficiency and surface area.
| Identifier | ExFiles\Box 24\5\ Scan334 | |
| Date | 1st January 1938 | |
| -4- Again, from surface, free air area, and direct cooling we should expect the square tube radiator to equal the S/Hm{Capt. W. Hallam - Head Repairs},m.{Mr Moon / Mr Moore} radiator in efficiency. The results show, however, that the round tube, which is smaller than the square tube, has in a matrix of similar frontal area some 6% greater efficiency. On the other hand, the water flow in the square tube radiator is not quite similar to that in the round tube radiator which may have some bearing on the subject. SHAPE OF TUBE. The round tube gives least surface for a given frontal area and a given minimum gap between the tubes. The hexagon tube gives 10% more surface for the same frontal area and the same size of water gap, it also gives the same type of water flow. The square tube waisted in the same way as the round tube and without vertical strips gives a further increase in surface over the hexagon. The Anderton Brown tube is an adaptation of the hexagon arranged so that the hydraulic resistance of the two diagonal passages equals the hydraulic resistance of the single passage into which they run. The Anderton Brown tubes that we are at present using on aircraft radiators are .005 thick 14.0" long and .5" across the largest dia. THICKNESS OF TUBE. Our ordinary round tubes are .007" thick. The St/7m.m tubes were made .0085" thick to take the large draw required. | ||