well two heat exchangers are shown in fig2 and 3 with flat tubes 10 and flat tube ends 54 are formed as described it should be appreciated from these figures and the rest of the disclosure that a different configuration of flat tube ends 54 could be provided within the scope of the present invention moreover fig2 and 3 show heat exchangers having two rows of flat tubes 10 connected with one end 40 to opposite sides 20 a 20 b of the collecting tank 20 so that the already described flow of the heat transfer agent as indicated by the arrows is established in conjunction with the partition 22 in collecting tank 20 the tube lengths l increase continuously in those rows so that in two diagonally opposite corner regions of the heat exchanger the longest flat tubes 10 are provided and in the other two corner regions the shortest flat tubes 10 are present as both figures show as a result heat exchangers according to this feature of the present invention may be readily manufactured with a front surface having a configuration deviating from the usual rectangle or square for example a front surface configuration can be achieved in which the round or u shape of the opening fits into a fan hood as a result it is possible to provide heat exchangers which can be more simply adapted to different space requirements such as may be encountered in different vehicles the difference between fig2 and 3 is that the fig2 heat exchanger has a.