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).
Page from a report discussing the efficiency gain from using an evaporative engine cooling system.
| Identifier | ExFiles\Box 178\1\ img041 | |
| Date | 15th February 1926 guessed | |
| - 25 - longer deal with all the steam generated, a relief valve allows steam to escape from the top of the radiator. (ii) Maximum gain in efficiency. Evaporative cooling cannot be looked upon as a solution to all boiling troubles. The facts are actually these. The engine is imparting exactly the same quantity of heat to the cooling water as in a normal system. The radiator is capable of dissipating the same quantity of heat as previously. The only real difference is that the heat has been transmitted from one place to the other by means of a vapour instead of a liquid. When the car is on the point of boiling with water in the radiator in a normal system, the water at the bottom of the radiator will probably be about 90°C, so that the mean temperature of the radiator will be 90 + 100 / 2 = 95°C. When the radiator of an evaporatively cooled car can no longer cope with the supply of steam, the whole radiator is at 100°C. In other words, when the car is on the point of overheating with an evaporative system, the difference between the mean radiator temperature and the atmosphere will be some 5°C, higher than were a normal system fitted to the same car. This with a Silver Ghost car, means an increase in efficiency of some 6.5% or about half that obtained by running a normal system under a pressure of 6 lbs/sq.in. Therefore the actual increase in efficiency will be about on a par with that obtained at present by opening the bonnet shutters. contd. | ||