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).
Comparison of engine and oil cooler performance, including road test observations.
| Identifier | ExFiles\Box 179b\3\ img312 | |
| Date | 18th March 1933 | |
| -3- He/StL/KT.18.3.33. Again for a given engine speed the road speed of Benaport is about 33% greater than Peregrine. We are measuring the actual heat to the oil on Benaport, naturally with the aluminium crankcase and timing case the radiation on this unit is greater than on Peregrine. On the road we also believe that the timing case being in front acts as a very appreciable oil cooler as it gets a considerable quantity of air, and the gears produce maximum oil turbulence on the exposed surfaces. We are conducting road tests to prove this point. SUBSIDIARY OIL COOLER. The tube type of cooler through which the water from the bottom of the radiator is passed has been fully reported on in He/Std. 1/KT.17.2.33. It will be noted that a matrix only 4" x 3" x 3 will dissipate 100 B.Th.U's/min under the conditions likely to exist on the car. Actually the ribbon type of radiator matrix we have on Peregrine will give us a top water temperature of 75°C. only, with an atmospheric temp. of 30°C. 100 B.Th.U's to the water will cause no trouble as it is only 3% of the engine heat. The advantage of heating up the oil in cold weather must be considerable. The weight of this cooler when properly designed should not be more than 8 lbs. Of air heaters of the cellular type we have no experience. Assuming that we get a heat transfer coefficient of .65/sq.ft/oC we shall require a matrix having a frontal area of 3 sq.ins. for each 100 B.Th.U's to be dissipated at 70 m.p.h. the tubes being 4" deep. Air Temp. 30°C. It will be observed that the volumes of the matrices of these two coolers/100 B.Th.U's are almost identical, and therefore their weights will be about the same. One feature in connection with cellular coolers that should not be missed is the advantage of high oil velocity in improving the efficiency thereof. The report mentioned above gives curves illustrating this and we also give figures supplied on the Petts oil cooler indicating similar characteristics - (He.980). | ||