Abstract: A heat exchanger has a shell formed of several sections placed side by side and each defining an intermediate baffle forming part of a spiral surface. The adjacent sections define together a spiral path extending through the shell in the direction of its axis. Tubes extend in this axial direction through aligned holes provided in each shell section. The tubes communicate between end spaces comprising an inlet and outlet for the first fluid. The use of shell sections provides a convenient construction method for the heat exchanger while the spiral path for the second fluid gives better flow characteristics.