Abstract: Disclosed herein is a heat exchanger with a housing casing, a first base and a second base with openings, pipes as a first flow channel for conducting a first fluid, the ends thereof being arranged in or on the openings of the first and second bases, the pipes and the first and/or the second base are arranged within the housing so that a second flow channel for conducting a second fluid is designed between the housing and the pipes, a first inlet opening for the first fluid, a first outlet opening for the first fluid, a second inlet opening for the second fluid, a second outlet opening for the second fluid, a first diffusor for directing the first fluid into the pipes, a second diffuser for directing the first fluid out of the pipes, which heat exchanger should be simple and cost-effective to produce and ensure reliable operation.