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 characteristics and challenges of glycol and pressure cooling systems.
| Identifier | ExFiles\Box 149a\3\ scan0233 | |
| Date | 16th November 1938 | |
| -2- (9) Great care must be taken with all joints, since glycol creeps badly, and will find the smallest leak. (10) Owing to low heat transfer coefficient of glycol compared with water, glycol necessitates, approx., a 10% larger radiator when compared with water operating at same temperature and coolant flow. (B) PRESSURE COOLING. (1) Average operating temperature - 100 to 101°, zero pressure. (2) Max. operating temperature - 121°C - 15 lbs/sq.inch pressure (above atmos.) (3) Leak from pressure valve provided to enable system to rid itself of air- therefore steam-tightness of same is not very important. This would not apply on chassis work, since continuous operation under pressure might occur - in aero practice, machine only operates pressure cooled for 5 minutes or so on climb - under level flight conditions pressure is zero approximately. Further, ratio of coolant capacity of cooling system to minimum practicable size of leak hole is much greater on aircraft than on chassis work. (4) Pressure water connections have to be very sound, of course, and the aero people have developed a pressure coupling for this purpose. (5) A very good water pump seal gland is obviously necessary - the aero people are not entirely satisfied with their glands on either water, glycol, or pressure cooled engines. We have hopes, however, on the chassis side that the Vauxhall or 'Packless' type gland, with which we are at present experimenting, will prove satisfactory for either glycol or pressure cooling. (6) No trouble has been experienced in flight with radiator reliability, which is attributable to pressure in the cooling system - actually the main cause of aero radiator trouble is vibration (soldered round tube (hex. ends) radiators are used). | ||