The invention relates to a spiral heat exchanger including a central cylinder (5) and at least two spiral sheets (6, 7). The sheets extend from the cylinder to form a first spiral-shaped flow channel (8) for a first medium and a second spiral-shaped flow channel (9) for a second medium. The cylinder forms an inner space within the cylinder. The cylinder includes a first opening (11) communicating with the first flow channel and a second opening (12) communicating with the second flow channel. A pipe (14) extends into the inner space of the cylinder. A first communication channel, communicating with the first flow channel via the first opening, is formed within the pipe. A second communication channel, communicating with the second flow channel via the second opening, is formed in the inner space outside the pipe.