The invention relates to an assembly of two housings, a first housing comprising a first cooling circuit portion and a second housing comprising a second cooling circuit portion, said of this cooling circuit portions being configured to form a cooling circuit with a fluid, each housing comprising a flat face comprising an opening of a respective cooling circuit portion and defining an interface of said cooling circuit, said cooling circuit portions being configured to be fluidically connected by plane-plane contact between said flat faces, said openings being arranged substantially opposite each other.

A holding support for a v-shaped heat exchanger having a flat base plate, which on a plate edge forms a spreading finger holder with holding fingers for holding flat tubes of the v-shaped heat exchanger and on a further plate edge forms a support for supporting the holding support. In a v-shaped heat exchanger two holding supports may be used to support the v-shaped heat exchanger on a surface.

An apparatus is provided for an aircraft powerplant. This apparatus includes a heat exchanger. The heat exchanger includes a frame, a plurality of heat exchanger cores, a first flowpath and a second flowpath. The frame extends circumferentially about an axis. The frame includes a plurality of receptacles within an interior of the frame. Each of the heat exchanger cores is housed within a respective one of the receptacles. The first flowpath extends in a first direction across the heat exchanger and through the plurality of heat exchanger cores. The second flowpath extends in a second direction across the heat exchanger and through the plurality of heat exchanger cores.

A heat exchanger is having: a housing having a first housing inlet, a second housing inlet, a first housing outlet, and a second housing outlet; and a core assembly disposed within the housing and removably connected to the housing, the core assembly comprises: a first fluid passage fluidly connecting the first housing inlet to the first housing outlet and a second fluid passage fluidly connecting the second housing inlet to the second housing outlet. The first fluid passage is thermally connected to the second fluid passage.