Condenser in vertical design with nonexchangeable straight-tube bundle. The bundle tubes can be cleaned easily after the disassembly of the heads. The interior of the shell is not accessible everywhere and can only inspected through the connection nozzles. The bundle tubes are attached by expanding or shrink-welding or both (depending on the operating conditions). The supercooling of condensate is possible. The heat exchanger is controlled by condensate accumulation. With the corresponding tube routing the condensate may accumulate up to 100%, even due to operating conditions such as downtimes or zero load. The wet conservation of the heat exchanger in case of long-term service interruption is possible. Depending on the operating conditions a compensator may be required to compensate the thermal expansion.