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 comparing the performance of hexagonal and round radiator tubes, including heat dissipation and water flow.
| Identifier | ExFiles\Box 27a\3\ Scan143 | |
| Date | 29th September 1930 guessed | |
| - 2 - For 7 x 120 m.m. tubes of my type (hexagonal bodies differentially spaced) there was a gain of 4½% in heat dissipation as compared with normal round tubes of the same dimensions, but in this case there was no central bulge. It may be noted in passing that the 10 x 320 m.m. tubes to my normal specification collapsed only under an external pressure of 28 to 30 lbs per sq. in. As regards improvement in water flow, the hydraulic resistance of an average radiator may be constituted thus:- Resistance of Branches, including shock losses and outlet energy, etc. 50 - 70% Tube Block................... 50 - 30% so that for an improvement in the tube block to be appreciated the other losses must be reduced, for example, between the outlet header and the pump impeller. For differential spacing, which I have used chiefly with hexagonal tubes, a definite improvement in radiator test waterflow with a given loss of head has been proved, for instance, taking sample radiators with Branches increased to 2½" dia. with tube blocks 12" square, so that the influence of the branches is slight, and testing with a fairly free supply at 7 ft. head above the inlet the following results were obtained:- Type of Tube Block. Gallons per min. 10 x 120 m.m. Round Tubes with 1 m.m. waterways (equally pitched).......... 60 Ditto with hex. tubes....................... 57 10 x 120 m.m. A.B. Patent tubes (hex). Waterways 1.5 m.m. vertical and .875 m.m. inclined...................... 74 Ditto 7 x 120 m.m......................... 77 Contd.... | ||