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Mechanically expanded technology is applied since long time for manufacturing of condensers for air conditioning applications. Typical geometry consists of round copper or aluminum tubes, and flat aluminum fins. This common solution limits the global performance, specially heat rejection, so that to have more performance it is necessary to advance the brazed technology, serpentine or parallel flow type condensers. The application of oval-flat tubes with ratio between major axis/minor axis, ratio indicated as a/b, greater than 3.0 to the radiators for engine cooling systems has relaunched the mechanically expanded technology, providing performance comparable to those of brazed technology. Until today the application of the oval-flat tube to the condenser has been considered not possible owing to the heavy work conditions on the tube side, specially in terms of pressure.

The use of oval flat tubes in the Mechanically Assembled Radiators (MAR) has extended the application field of this technology, covering wide range of brazed radiator applications. This second generation of Mechanical Radiators is characterized by oval tubes with a/b ratio greater than 3.0, which allows to approach to the brazed radiator tube shape. To approach to the flat tube geometry a new mechanically assembled aluminium radiator with real flat tubes has been developed and realized. The purpose of this paper is to present the development results of a radiator with real flat tubes of mechanical assembled type, named SIRIO, the effect of flat shape on the performances and comparison with relevant oval flat tubes.

Mechanically Assembled Heat Exchangers (MAHE) find wide applications in Automotive field, specially for Air Conditioning and Engine Cooling Systems. To improve the performance of MAHE with round tubes, new types of tubes with straight internal fins have been designed and realized, along with a new expansion tooling which allows to expand these types of tubes without destroying the internal fins. The purpose of this paper is to present a MAHE, developed for automotive use, with aluminum round tube internally finned, the technique of assembling tube-fin, the effects of the finned tube on the performances and its possible applications.