Question: Which Formula One car besides the Tyrrell P34 was one of the most radical entries ever to succeed in F1 competition, that used flat panel heat exchangers? 

Context paragraphs:
Covini C6W: C6W is an Italian 2-seat 2-door sports coupé with a removable roof section.  Inspiration for the car was taken from the 1976 Tyrrell P34, which had two pairs of smaller front wheels, a principle applied to the C6W.  The project was started in 1974 but abandoned shortly after, and left dormant into the 1980s due to the lack of availability of low-profile tires at the time.  In 2003 the project was revived and in 2004 the C6W was shown in prototype form.  In 2005 a slightly revised version debuted at the Salon International de l'Auto, featuring new wheels, new roof structure and a refreshed interior, and went into limited production of 6-8 cars per year, as a result of a tie-up between PMI and Covini Engineering.  The car features a rear, 4200 cc 8-cylinder engine and has a top speed of 186 mi/h .

Tyrrell 026: The Tyrrell 026 was the car with which the Tyrrell Formula One team competed in the 1998 Formula One season, and the last Tyrrell car to compete in F1.  It was driven by Ricardo Rosset and rookie Toranosuke Takagi.

Tyrrell 003: The Tyrrell 003 is a Formula One racing car which was designed for the 1971 Formula One season by Tyrrell's Chief Designer, Derek Gardner.  It was effectively the same car as Tyrrell 001, with a redesigned nose section, longer wheelbase and narrower monocoque.  Tyrrell 003 was a one-off design, its type number also serving as its Tyrrell chassis number.  François Cevert drove the Tyrrell 002.

Micro heat exchanger: Micro heat exchangers, Micro-scale heat exchangers, or microstructured heat exchangers are heat exchangers in which (at least one) fluid flows in lateral confinements with typical dimensions below 1 mm.  The most typical such confinement are microchannels, which are channels with a hydraulic diameter below 1 mm.  Microchannel heat exchangers can be made from metal, ceramic, and even low-cost plastic.  Microchannel heat exchangers can be used for many applications including:

Plate heat exchanger: A plate heat exchanger is a type of heat exchanger that uses metal plates to transfer heat between two fluids.  This has a major advantage over a conventional heat exchanger in that the fluids are exposed to a much larger surface area because the fluids spread out over the plates.  This facilitates the transfer of heat, and greatly increases the speed of the temperature change.  Plate heat exchangers are now common and very small brazed versions are used in the hot-water sections of millions of combination boilers.  The high heat transfer efficiency for such a small physical size has increased the domestic hot water (DHW) flowrate of combination boilers.  The small plate heat exchanger has made a great impact in domestic heating and hot-water.  Larger commercial versions use gaskets between the plates, whereas smaller versions tend to be brazed.

Tyrrell 006: The Tyrrell 006 was a Formula One car designed and built by the Tyrrell Racing Organisation.  It was introduced towards the end of .  In the hands of Jackie Stewart it won the Drivers' Championship for the Formula One season, Stewart's third and final title.  The car was first raced at the 1972 Canadian Grand Prix with Stewart's team-mate and protégé François Cevert at the wheel.  The 006 was a very slightly reworked version of the preceding Tyrrell 005 car, but in contrast it was the first Tyrrell-built chassis to be replicated, the number 006 becoming a model- rather than chassis-number; previous Tyrrells were one-off constructions.  In total there were three Tyrrell 006 models built: 006; 006/2; and 006/3.  The 006 model was gradually phased out in the early part of the 1974 Formula One season as Tyrrell constructed the succeeding Tyrrell 007.

NTU method: The Number of Transfer Units (NTU) Method is used to calculate the rate of heat transfer in heat exchangers (especially counter current exchangers) when there is insufficient information to calculate the Log-Mean Temperature Difference (LMTD).  In heat exchanger analysis, if the fluid inlet and outlet temperatures are specified or can be determined by simple energy balance, the LMTD method can be used; but when these temperatures are not available The NTU or The Effectiveness method is used.

Tyrrell P34: The Tyrrell P34 (Project 34), commonly known as the "six-wheeler", was a Formula One (F1) race car designed by Derek Gardner, Tyrrell's chief designer.  The car used four specially manufactured 10-inch-diameter (254 mm) wheels and tyres at the front, with two ordinary-sized wheels at the back.  Along with the Brabham BT46B "fancar" developed in , the six-wheeled Tyrrell was one of the most radical entries ever to succeed in F1 competition, and has been called the most recognizable design in the history of world motorsports.

Marine heat exchangers: Marine heat exchangers are no different than non-marine heat exchangers except for the simple fact that they are found aboard ships.  Heat exchangers can be used for a wide variety of uses.  As the name implies, these can be used for heating as well as cooling.  The two primary types of marine heat exchangers used aboard vessels in the maritime industry are: plate, and shell and tube.  Maintenance for heat exchangers prevents fouling and galvanic corrosion from dis-similar metals.

Brabham BT46: The Brabham BT46 is a Formula One racing car designed by Gordon Murray for the Brabham team, owned by Bernie Ecclestone, for the 1978 Formula One season.  The car featured several radical design elements, one of which was the use of flat panel heat exchangers on the bodywork of the car to replace conventional water and oil radiators.  This concept did not work in practice and was removed before the car’s race debut, never to be seen again.  The cars, however, powered by a flat-12 Alfa Romeo engine, raced competitively with modified nose-mounted radiators for most of the year, driven by Niki Lauda and John Watson, winning one race in this form and scoring sufficient points for the team to finish third in the constructors championship.

Supporting paragraphs: Tyrrell P34 Brabham BT46
Answer: The Brabham BT46