A heat exchanger comprising: at least one fluid tube configured to extend substantially orthogonally to a wind direction, the fluid tube having a first wall and a second wall, and the fluid tube comprising: - a first tube section and a second tube section each extending along the fluid tube, arranged such that each tube section is in fluid communication with a pair of manifolds (9, 10) and configured to contain a cooling fluid, wherein the first tube section is formed by the first wall, the second wall, a first outer wall and a first inner wall and the second tube section is formed by the first wall, the second wall, a second outer wall (8, 93) and a second inner wall, the first inner wall, the second inner wall, the first outer wall and the second outer wall (8, 93) extending substantially parallel along the fluid tube in fluid-tight contact with the first wall and the second wall, wherein the heat exchanger is configured to lead the cooling fluid in a first direction in the first tube section and in a second direction in the second tube section, the first direction being opposite to the second direction, wherein the cooling fluid is led through the second tube section before entering the first tube section and the first tube section is arranged upstream of the second tube section in relation to the wind direction so that a cooling air flowing in the wind direction cools the cooling fluid with the lowest temperature first, wherein the first inner wall and the second inner wall are spaced apart by at least one common area defined by the first inner wall and the second inner wall, the first inner wall and the second inner wall being arranged at a distance (d) from each other, and the at least one common area being arranged between the first tube section and the second tube section characterised in that the fluid tube is made from a first sheet defining the first wall and a second sheet defining the second wall, and the common area comprises at least one slot. - a first tube section and a second tube section each extending along the fluid tube, arranged such that each tube section is in fluid communication with a pair of manifolds (9, 10) and configured to contain a cooling fluid, wherein the first tube section is formed by the first wall, the second wall, a first outer wall and a first inner wall and the second tube section is formed by the first wall, the second wall, a second outer wall (8, 93) and a second inner wall, the first inner wall, the second inner wall, the first outer wall and the second outer wall (8, 93) extending substantially parallel along the fluid tube in fluid-tight contact with the first wall and the second wall, wherein the heat exchanger is configured to lead the cooling fluid in a first direction in the first tube section and in a second direction in the second tube section, the first direction being opposite to the second direction, wherein the cooling fluid is led through the second tube section before entering the first tube section and the first tube section is arranged upstream of the second tube section in relation to the wind direction so that a cooling air flowing in the wind direction cools the cooling fluid with the lowest temperature first, wherein the first inner wall and the second inner wall are spaced apart by at least one common area defined by the first inner wall and the second inner wall, the first inner wall and the second inner wall being arranged at a distance (d) from each other, and the at least one common area being arranged between the first tube section and the second tube section characterised in that the fluid tube is made from a first sheet defining the first wall and a second sheet defining the second wall, and the common area comprises at least one slot.