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).
Choking issue in cooling systems by comparing the gap area and hydraulic mean depths of different series of tubes.
| Identifier | ExFiles\Box 24\5\ Scan200 | |
| Date | 24th August 1929 | |
| HS{Lord Ernest Hives - Chair}/RM.{William Robotham - Chief Engineer} FROM DA.{Bernard Day - Chassis Design} X/66 DA{Bernard Day - Chassis Design}2/M24.8.29. C. to BY.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer} COOLING SYSTEMS. X.7250. X.766. With reference to HS{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}2/MJ 21829. we think there is still something mysterious about the choking up: (1) The gap seems to have always been 1 mm. (2) Though the length of the gaps has been reduced the number of gaps has been increased owing to the reduced dia. of the swelled up ends. Since the length of enlarged end is the same on all the tubes we have been able to examine, the following comparative figures obtain: | | Area of one gap | No. of gaps from width of matrix. | Total Area sq. ins. | | :--- | :--- | :--- | :--- | | V.{VIENNA} series. | .0394 X 4.25 = .1674 | 77 | 12.81 | | F.2.B. | .0394 X 3.75 = .1476 | 88 | 13.00 | | SS.{S. Smith} 7/6 tubes. | .0394 X 3.50 = .1379 | 87 | 12.00 | = (81X100)/12.81 = 6.32% less than V.{VIENNA} series. | | SS.{S. Smith} 7/5¼" | .0591 X 3.5 = .207 | 87 | 18.00 | = 5.19/12.81 = 40.5% more than V.series. | So that though SS.{S. Smith} with 7/6 tubes has some 6% less area than V.{VIENNA} series, with 7/5¼ tubes the SS.{S. Smith}area is much more. Comparative hydraulic mean depths are: Hydraulic mean depth V.series .01925 F.{Mr Friese} 2. B. .01955 SS.{S. Smith} (7/6 tubes.) .0195 SS.{S. Smith} (7/5¼ tubes.) .0291 from which it would appear that while there is no appreciable difference in the first 3 radiators, the advantage is with SS.{S. Smith} The reference in para.1 of your memo. to the top tube space on SS.{S. Smith} being 25% less than on V.{VIENNA} series we cannot entirely understand The reduction in length is .750, and .750 / 4.25 = 17.65% If you refer to the rectangular hole made by the bottom of the top tank the difference in area is of the order of 29%. but | ||