Meredith Effect and the P-51

[drgondog]

No offense taken - excellent engineering reduction of the system.

 

[krieghund]

This is probably the best way to go to reduce the drag of the radiator.

 

[alejandro_]

Five hundred cubic feet of air raised 200 degrees F per second corresponds to 47 horsepower.

It has been a while but I would be interested in knowing how you found the volume and temperature raise. A few years ago I looked at this. North American claimed that the radiator created 300lb of thrust. I assumed this was at maximum speed (+700km/h) and after efficiency losses. Then I converted thrust into HP.

300lb of thrust = 136 kgf
[1 kgf = 2.20 pounds]

703km/h = ~195m/s

Power (W) = Thrust × velocity
Power (W) = 136kgf × 195m/s
Power (W) = 260000 watts = 260kW
260kW= 354HP

Some of the conversion rates might vary a bit. This method is applied for turbines but I don't know if it holds for propeller engines.

 

[Edgar Brooks]

Does anyone actually have a copy of this alleged material by Meredith? I say "alleged" because there is nothing substantial in our National Archives, apart from a few single papers, including original sketches, none of which mention radiators. His entire thrust (if you'll pardon the pun) concerned jet propulsion, and nothing else, with typically luke-warm reaction from senior officers in the Air Ministry.
A year later, together with another scientist, he came up with an idea on how to dispel boundary layer drag, using small holes in the wings' surfaces, through which air would be blown (forerunner of post-war ducts, presumably.) They got as far as taking out an initial patent, but delayed so long that others published similar information, and any lead was lost.

 

[Shortround6]

I think "alleged material" is a bit strong.

See: clark yh | air ministry | scientific research | 1936 | 2349 | Flight Archive

second report under technical literature.

apparently you could get a reprint of the 13 page report for 9 pence?

 

[Edgar Brooks]

One of the definitions of "allege" is to "cite or quote in a discussion," which is why I used it; thanks for the link, which means that I have a lot more digging to do, to find the original.
Interestingly, the Spitfire was ordered in December 1934, and this report was published several months later, so which came first, or was the shape of the Spitfire's radiator changed as a result of Meredith?
I've found the original tenders for the Hawker "High-Speed Monoplane" (never called, officially, the Fury Monoplane,) but, so far, not the Supermarine Type 300, so I know what my homework (in Kew) has to be, because both should be in there somewhere.

 

[Shortround6]

One of the definitions of "allege" is to "cite or quote in a discussion," which is why I used it;

Well, they do say that the Americans and the British are one people separated by a common language

Considering some of the multiple configurations some other aircraft went through for radiator design on prototypes after the first flight, the apparent "fact" that Meredith didn't "publish" or finish the report until Aug of 1935 doesn't really concern me that much except for historical accuracy. The Specification was changed in April to go from four guns to eight after all so the design wasn't cast in stone yet. I believe (from other sources?) that this report by Meredith was read at a conference first (??) before being "published"?

 

[Edgar Brooks]

I believe that I've found it (at least the file in Kew,) and that was entirely due to the reference/title of the report which you supplied, so thanks again for that; the difficulty seems to stem from the file having no mention of Meredith, himself, and there's a possible reason for that, but it will take more digging.
There are other references to him being investigated for being "involved in left-wing activity" some time up to the end of 1949, and he apparently confessed to being a Soviet agent before the war (he seems to have left the RAE in 1938.) There are 3 files, on that subject, which were closed until 2006, but I'm not sure that they'll be of any interest to aviation enthusiasts.

 

[Edgar Brooks]

Found it, and, after all that, there are two copies, in separate files. It consists of 20 pages, and I suspect you'll need a degree in maths to get the full gist of it. Due to the size, I won't make any attempt to put it on here, but if anyone would like a copy, let me know. In common with RAE practice, he notes any other source to which he referred, and there's only one:- "Further experiments on honeycomb radiators," by Harris Caygill, in November 1924.
Oddly, Meredith seems to have been more concerned with the temperature of the coolant, and its heat transfer to the airflow, than the design of the radiator housing, in fact he states that the radiator becomes more efficient as the aircraft's speed increases, with the optimum "changeover" from drag to thrust being around 300mph, in average U.K. ambient temperature conditions (in another publication, that I have, it states that experience showed it to be nearer 400 than 300.)
Meredith left the RAE in 1938, and worked at Smiths Industries from then; he remained "of interest" to the authorites until 1958 (when he would have been 63,) but was never imprisoned, arrested, or even charged, possibly because any information he'd passed on in the 1930s was common knowledge, and certainly because his work at Smiths was never of a sensitive nature. (It's possible, of course, that the invasion of Hungary, in 1956, made him think twice [as it did for so many communist sympathisers,] since all surveillance on him stopped in 1958, and no more is heard of him from that date.) The Intelligence files on him were closed to view until 2006, which means of course that he (and possible even his children) has died, so there's no chance of any stigma being attached to any relatives.
Mention is continually made of his brilliance, and there's a sneaking suspicion that the authorities were prepared to allow him a lot of leeway, for fear of losing him, if he decamped to Russia. As well as his jet propulsion and radiator papers, he also did innovative work on instrument capsules (papers which I haven't yet looked at,) so to say that he never invented anything is way wide of the mark.

 

[Bottlehead]

I am new to this forum as I am not an aeronautical engineer, However my Uncle Thomas Pitt de Paravicini
worked in the 30's after leaving university at the Aircraft Establishment at Farborough and was with Meredith before going to Rolls Royce Derby and had most of the patents on what he called Negative Drag. He was the youngest person to become a member of the Royal Aeronautical Society in the mid 30's.
A list of GB patents as follows, the first pair filed in September 1935 GB463303 an 463313 on cooling 471177 on exhaust discharge relating to V12 engines. 471371, 472334, 472555, 472820, 473340, 473341 and 484300 all relate to cooling of both radial and inline engines. He stated to our family many years ago that Rolls Royce exchanged many patents with the Germans before 1939, Hence the 109 copying it. He never derived any great fortune, as is usual practice that the company owned the rights. He then moved with 2 other engineer/ designers to Armstrong Siddely (Bristol Aircraft) in 1941 and had a further patent GB536189 Testing of Engines and Airscrews in a closed circuit system. If you google TP de Paravicini and Bloodhound there are references to his paper on in 1942 the Fan Bypass Jet engine.
I am trying to get his acknowledgements recognised. Merediths patent is only a single one relating directly to this.
Meredith patent GB454266 just proceeds TP de P and James Ellor by a few months but it was proceeded by Ellor in
GB447283.

 

[Bottlehead]

I must add correction, Should have been TP de Paravicini and Wolfhound and Stewart Tresillan.