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).
Technical letter discussing the comparative performance of hexagonal and round radiator tubes for engine cooling systems.
| Identifier | ExFiles\Box 27a\3\ Scan144 | |
| Date | 14th October 1930 guessed | |
| - 3 - It is thus seen that, unless the advantage is lost by inefficiency of the outlet branch of the radiator and suction resistance of the circulating pump, there is an advantage in the differential spacing since the use of normal hexagon tubes reduces the flow 5%, while the particular differential spacing not only restores this but shows a total gain of 23% in flow, i.e. to get the same flow through the other tube block would involve a loss of 50% more head. It is worth noting that if the six sides of a hexagonal tube be considered in relation to its neighbours, the waterways are deliberately reduced on four sides and increased on the two vertical sides, resulting in a water capacity increased inappreciably over the hexagonal tube as normally spaced, and less than that of round tubes as normally spaced. The water flowing through the tube block is more-over maintained at an almost constant speed, whereas when the waterways are equal it is constantly being doubled and halved in speed. The use of hexagonal tubes instead of round ones increases the surface by 10%, the throughway area for the air by 10%, and the weight by the difference between the added brass and the subtracted water. There is, of course, no reason why differential spacing and intermediate bulging should not be used with round tubes, but aeroplane work does not lead to this develop-ment. May I now direct your attention to another of the features of my patent No. 219788, viz: tubes with a relatively large number of indentations or corrugations as for example Figs Nos. 11, 15 and 20 which may reasonably be expected to give greater cooling than plain tubes. Messrs. Rolls-Royce have no doubt a large amount of information on the limiting conditions for car radiators, and the airspeeds, water speeds and water temperature drop between radiator inlet and outlet, and would probably be prepared to experiment with types of tube with a view to attaining such improvements in both cooling, waterflow, etc. as may be possible. With kind regards, Yours sincerely, (Sgd) C. Anderton Brown. | ||