Meredith effect
In 1936, F. W. Meredith pointed out that the waste heat energy of a piston engine which is transferred to the cooling-air flow in a radiator is not all lost; it produces a small thrust provided the pressure at the exhaust of the radiator tubes is higher than the free static pressure of flight.[1] This phenomenon became known as the "Meredith effect."
Its mechanism was something of a mystery to many engineers of that period.[2] A common fallacious notion was that the radial engine, because its fins were hotter than usual radiator temperatures of liquid-cooled engines, would enjoy greater benefits. (This mistaken notion still existed as late as 1949 and is stated by Schlaifer to constitute an "inherent advantage of the radial engine".) The Meredith effect was so small at 1936 airspeeds that it could conveniently be neglected in performance estimates both by those who did not understand it and by those who doubted that such an effect really existed.
The concept was devised by Fredrick Meredith at the Royal Aircraft Establishment (RAE), Farnborough, prior to World War II, and incorporated into a radiator-duct design that produced thrust, helping to offset the drag produced by the radiator.
One of the first aircraft to incorporate a radiator designed to make the use of the effect was the Supermarine Spitfire. The North American P-51 Mustang is also noted for using this effect. {{citation}}: Empty citation (help)
References
- ^ Meredith, F. W: "Cooling of Aircraft Engines. With Special Reference To Ethylene Glycol Radiators Enclosed In Ducts", Aeronautical Research Council R&M 1683, 1936.
- ^ http://www.hq.nasa.gov/pao/History/SP-445/ch5-5.htm THE HIGH SPEED FRONTIER Chapter 5: High-speed Cowlings, Air Inlets and Outlets, and Internal-Flow Systems; The Ramjet Investigation
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