Evaporation heat exchanger, especially for a spacecraft

A heat exchanger for cooling a coolant in a cooling circuit in a spacecraft under gravity-free operating conditions and under different acceleration conditions, comprising a housing enclosing an evaporation space, a plurality of tube panels in said evaporation space, inlet valve means for introducing an evaporating medium into said evaporation space, vapor outlet means for discharging vapor from said housing, a plurality of cooling tubes forming said tube panels in said housing, short tube legs interconnecting said cooling tubes to form meandering tube loops forming part of said cooling circuit, said cooling tubes having long legs extending in parallel to one another and substantially perpendicularly to a main flow direction of said evaporating medium from said inlet valve means to said vapor outlet means, and wherein spacings (A, B, C, . . . ) between neighboring long tube legs differ from one another in said flow direction from said inlet valve means to said vapor outlet means for establishing a substantially constant flow speed of said evaporating medium, whereby contact between tubes is effectively increased while still permitting a substantially free flow of said evaporating medium through flow paths between neighboring tube panels for an efficient evaporation.