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 discussing the function and efficiency of a thermostat as a mixing valve in a cooling system.
| Identifier | ExFiles\Box 156\1\ scan0100 | |
| Date | 20th May 1935 guessed | |
| - 3 - Messrs. Rolls-Royce Ltd. is to act as a mixing valve for hot and cold water to produce in the final mixture as constant a temperature as possible. The efficiency of the operation of the instrument can be judged by the constancy of the mixture produced. It is, of course, a primary necessity that there shall be available for the thermostat a sufficient quantity of both hot and cold water, otherwise it clearly cannot regulate the final temperature. When an engine is first started from cold there is available an insufficient supply of hot water to enable the thermostat to perform its function; similarly if an engine is loaded, or if the cooling is reduced to such an extent that the temperature of the cooler water leaving the radiator is insufficiently cool, the thermostat again cannot perform its function The fact that a thermostat is full open within 7° or 11°C. of the temperature at which it commences to open, has nothing to do with the temperature control given, since for a constant water pump output the flow past the thermostat to the radiator is governed by the area and not by the lift. If the diameter of the valve head is kept large enough it will be found that the thermostat never reaches the full open position until the temperature of the cooled water leaving the radiator has risen abnormally. In such a condition the temperature of the cooling water would be above the temperature which the thermostat was required to maintain, even if a thermostat were not fitted. In our experience one of the most important features which concerns the closeness of the final temperature control is the area of the by-pass relative to the area of the water return from the base of the radiator to the suction of the pump. If we assume that at a certain engine speed | ||