Abstract: A tube-and-fin heat exchanger comprising tubes (1) for the flow of a heat carrier at some temperature, said tubes being installed in broached holes (9) provided in a stack of fins (2,3). The tubes (1) are installed so that adjacent fins (2,3) form a multiplicity of ducts for the flow of another heat carrier at a different temperature. Each fins (2,3) is provided with projections (4) and depressions (5) which form in the ducts symmetrical divergent-convergent portions for setting up turbulence in the heat carrier flow layer at the wall. The fins (2 and 3) have rectilinear portions (8) located between the divergent-convergent portions and situated opposite each other on adjacent fins (2 and 3).