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).
Radiator efficiency, heat dissipation, and a comparison of different radiator tube types.
| Identifier | ExFiles\Box 15\1\ Scan379 | |
| Date | 24th September 1930 | |
| -3- we dissipate about 19 1/2 H.P. per sq. foot of frontal area /100° F.{Mr Friese} difference in temperature between the mean radiator temperature and the atmospheric temperature, which corresponds to the figure obtained both by Dalby and the Bureau of Standards on the same type of radiator at an air velocity through the matrix of about 38 M.P.H. Furthermore, this speed is approximately confirmed by taking the temp. rise of the air across the radiator and from it calculating the quantity of air that must be passing to dissipate the heat lost from the cooling water. We have included a curve 'C' in the graph of radiator core efficiencies which corresponds most nearly to the projected 6 m.m. square tube radiator from which it will be observed that from the Bureau of Standards' results we should expect an increase of radiator efficiency at car speeds of 80 M.P.H. and upwards of over 20% with the new radiator. It will be observed that the square tube radiator maintains its efficiency well at the higher air speeds due to the fact that it has almost 30% direct cooling. SIZE OF TUBE. From our tests with the four types of radiator we have available we have the following results :- The 6A/7 tube radiator is 5% more efficient than the 6/7A. It actually has less cooling surface than the 6/7A matrix, less direct cooling, and less free air area. Therefore from all calculations we are surprised at the result and can only conclude that at the low air speeds at which we work, the small tube in some way promotes greater turbulence. | ||