A heat exchanger for indirect heat exchange between a first and a second medium is provided with a shell space for receiving the first medium, and a tube bundle arranged in the shell space and for receiving the second medium. The tubes are helically wound in a number of tube layers onto a core tube. The tube bundle includes a first tube layer which is positioned further outward in the radial direction of the tube bundle from an adjacent second tube layer. The heat exchanger includes at least one spacer and the first tube bundle is supported against the second tube bundle via the at least one spacer. The at least one spacer has a flow-directing region designed to deflect part of the first medium flowing along a tube of the first tube layer in the direction of the second tube layer situated further inwards in the radical direction.