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).
Analysis of radiator cooling performance, comparing revisions of the EAC.8 radiator with different tube dimensions.
| Identifier | ExFiles\Box 24\5\ Scan136 | |
| Date | 17th February 1925 | |
| -2- The increases on the original EAC.8. are due to the matrix going further below the top of the frame, and also due to the construction doing away with the side plates not in contact with water. We understand however from experimental reports that increased cooling resulting from increase of face area is not exactly in proportion, due to the limited size of fan. It is also reported from London, but needs confirmation, that EAC.8. shewed signs of being better cooled than std., and it was attributed to the fan being much closer to the radiator matrix. As regards the length of the tubes. In 1924 reported that reducing the length from 4.75 to 4.4 (same number of tubes) lowered the efficiency 4% at 30 m.p.h. In the following table, which gives proportional figures only, for total cooling area in radiator it will be seen that using the same dia. tubes as now, EAC.8. revised still has a gain over W. series, and if it were thought possible to reduce the dia. of the tubes so that instead of being 7 mm. expanded to 8 mm. at the ends, the short tubes were made 6.25 mm. expanded to 7 mm. at the ends, a very considerable gain in area results :- CAR. | Total area in radiator. | Increase over V.series. | Increase over W.series V.series Phantom. | 4750 | --- | --- W.series " | 4970 | 4.63% | --- Existing EAC.8. | 5265 | 10.85% | 5.95% EAC.8. revised - 8/7 mm. tubes 4.5 long. | 5190 | 9.27% | 4.43% EAC.8. revised - 7/6.25 mm. tubes 4.5 long. | 6025 | 26.9% | 21.25% Assuming that a certain quantity of air is required for cooling, as far as we can calculate from frictional resistance, velocity-head, etc. the radiator with 6.25 mm. tubes appears to offer considerably less resistance to the passage of this given quantity of air than with the 7 mm. tubes, and this combined with its increase area seems to offer a chance of it being a better cooling agent. DA.{Bernard Day - Chassis Design} | ||