A heat exchanger for a fluid having a vapor-phase and a liquid-phase, comprising: a first manifold; a second manifold; a plurality of parallel channels being in fluid communication with said first and second manifolds (18, 20); a first partition defined within said first manifold so that said plurality of parallel channels define a first pass in fluid communication with an inlet side of said first manifold and a second pass in fluid communication with an outlet side of said first manifold; a mixing device being configured to mix the fluid flowing into said first manifold so that the fluid is a substantially homogeneous two-phase mixture of the vapor and liquid phases; one or more baffles within said first manifold, said one or more baffles being configured to ensure that the fluid enters said plurality of parallel channels as the substantially homogeneous two-phase mixture; a second partition defined within said second manifold so that said first pass is in fluid communication with an inlet side of said second manifold and said second pass is in fluid communication with an outlet side of said second manifold, said inlet and outlet sides (32, 34) of said second manifold being in fluid communication; a collection insert within said inlet side of said second manifold, said collection insert configured to mix the fluid flowing from said inlet side of said second manifold to form the substantially homogeneous two-phase mixture; a second distribution insert within said outlet side of said second manifold, said second distribution insert being configured to mix the fluid flowing into said outlet side of said second manifold from said inlet side of said second manifold so that the fluid is the substantially homogeneous two-phase mixture; and one or more second baffles within said outlet side of said second manifold, said one or more baffles being configured to ensure that the fluid enters said plurality of parallel channels of said second pass as the substantially homogeneous two-phase mixture. a first manifold; a second manifold; a plurality of parallel channels being in fluid communication with said first and second manifolds (18, 20); a first partition defined within said first manifold so that said plurality of parallel channels define a first pass in fluid communication with an inlet side of said first manifold and a second pass in fluid communication with an outlet side of said first manifold; a mixing device being configured to mix the fluid flowing into said first manifold so that the fluid is a substantially homogeneous two-phase mixture of the vapor and liquid phases; one or more baffles within said first manifold, said one or more baffles being configured to ensure that the fluid enters said plurality of parallel channels as the substantially homogeneous two-phase mixture; a second partition defined within said second manifold so that said first pass is in fluid communication with an inlet side of said second manifold and said second pass is in fluid communication with an outlet side of said second manifold, said inlet and outlet sides (32, 34) of said second manifold being in fluid communication; a collection insert within said inlet side of said second manifold, said collection insert configured to mix the fluid flowing from said inlet side of said second manifold to form the substantially homogeneous two-phase mixture; a second distribution insert within said outlet side of said second manifold, said second distribution insert being configured to mix the fluid flowing into said outlet side of said second manifold from said inlet side of said second manifold so that the fluid is the substantially homogeneous two-phase mixture; and one or more second baffles within said outlet side of said second manifold, said one or more baffles being configured to ensure that the fluid enters said plurality of parallel channels of said second pass as the substantially homogeneous two-phase mixture.