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).
Report page discussing tests on engine heating systems, including a data table showing the influence of water velocity on heat transfer.
| Identifier | WestWitteringFiles\O\2January1926-March1926\ Scan83 | |
| Date | 12th February 1926 guessed | |
| contd :- -3- During the same tests we recorded the inlet and outlet temperatures of the heating medium passing through the hot spot jacket - i.e. water, steam and exhaust gas for the three systems. We therefore found the average temperature of the heating medium supplying heat to the charge. Unfortunately, this, although at first sight looked promising, could not be used as a basis of comparison of the three systems because of the well known fact that the "thermal resistance" offered by the hot gas in contact with the hot spot walls (in the case of the exhaust heated system) is much higher - probably 40 or 50 times - than that offered by the water film in the case of the water heated system. (See Aircraft & Automobile engines, by Judge). Even when testing the water heated system it was found that the rate of water flow alone had considerable influence on the amount of heat passing from the water to the charge. Therefore not only does the character of the heating medium influence the heat transfer but also the velocity. The following figures show how the water velocity influences the heat supplied to the charge :- | R.P.M. | lbs/m.{Mr Moon / Mr Moore} of water. | Aver. hot spot temp. | B.T.U's/m.{Mr Moon / Mr Moore} to charge. | Temp. diffce. between hot spot & charge. | |---|---|---|---|---| | 1500 | 1.4 | 66.3°C | 21.2 | 45.8°C | | 1500 | 3.7 | 68.7 * | 40.5 | 44.7 * | | 1500 | 7.3 ++ | 69.87 * | 50.0 | 44.87 * | ++ Average flow at this speed with the water heated system. After all, for any of the three systems on a car the criterion is the time which elapses before a driver can contd:- | ||