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).
The relative amounts of heat rejected to cooling water in engines.
| Identifier | Morton\M3.4\ img018 | |
| Date | 1st September 1924 | |
| B.R. 493A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. REF. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}/LGS.9.24. RELATIVE AMOUNTS OF HEAT LIKELY TO BE REJECTED TO COOLING WATER. 40/50 & EAG. Ricardo states that in a well designed engine of compression ratio 5 : 1, 28% of the total available heat is carried away by the cooling water. This 28% he has found to be made up as follows :- (a) 15% from the exhaust during the exhaust stroke. (b) 7% during expansion. (c) 6% during combustion. From these figures it will be seen that the most potent factor in determining the heat lost to the cooling water is the temperature of the exhaust. Now we know that if we raise the compression ratio of an engine, we increase its explosion temperature, but decrease its exhaust temperature. Are we justified in assuming that the reduction in the heat lost to the cooling water due to the lower temperature of the exhaust, will more than compensate for the gain in heat lost during the explosion and expansion due to the higher maximum temperature? According to Ricardo's tests, which he asserts were carried out with great accuracy, we are. He ran his variable compression engine during some tests first at a ratio of 3.8 : 1, then at 5.45 : 1, on a sample of Petrol A.{Mr Adams} At 1500 r.p.m. it will be observed that with the higher compression ratio, 1.5% less of the total heat available is transmitted to the cooling water. contd :- | ||