Heat exchanger comprising tubes with outer ribs and having the following features: 1.1. a face of the heat exchanger is an area penetrated by a flow in the incident flow direction (p), wherein a plurality of rows (R1, R2) of tubes are disposed one behind the other in the incident flow direction (p); 1.2. the rows (R1, R2) are transverse to the incident flow direction (p); 1.3. the tubes of the successive rows (R1, R2) are disposed displaced by a transverse offset parallel to the preceding row (R1, R2), wherein the transverse offset being unequal to a transverse separation distance transverse to the incident flow direction (p), wherein the transverse offset and the transverse separation distance from the centre of adjacent tubes are measured transversely to the incident flow direction (p), or 1.4. the tubes adjacent within a row (R1, R2) are offset from one another by a longitudinal offset running in the incident flow direction (p), wherein the longitudinal offset being smaller than a longitudinal separation distance of the tubes of the successive rows (R1, R2), wherein the longitudinal offset and the longitudinal separation distance from the centre of adjacent tubes are measured in the incident flow direction (p); 1.5. the tubes penetrate the ribs extending transversely to the tubes and are connected to the ribs via a collar on the ribs; 1.6. the transverse separation distance of the tubes of a row (R1, R2) is greater than the mean width of the ribs measured transversely to the face of the row (R1, R2), so that a gap is present between the ribs of adjacent tubes; 1.7. the ribs are rectangular and have winglets (6a, 6b), wherein a winglet (6a, 6b) is respectively disposed in the corner region of a rib, characterised in that 1.8. the tubes have an elliptical cross-section such that the gap has a width of 0.1- to 0.5-fold the mean width of the ribs and that the winglets (6a, 6b) are disposed at a distance from longitudinal sides and transverse sides of the ribs. 1.1. a face of the heat exchanger is an area penetrated by a flow in the incident flow direction (p), wherein a plurality of rows (R1, R2) of tubes are disposed one behind the other in the incident flow direction (p); 1.2. the rows (R1, R2) are transverse to the incident flow direction (p); 1.3. the tubes of the successive rows (R1, R2) are disposed displaced by a transverse offset parallel to the preceding row (R1, R2), wherein the transverse offset being unequal to a transverse separation distance transverse to the incident flow direction (p), wherein the transverse offset and the transverse separation distance from the centre of adjacent tubes are measured transversely to the incident flow direction (p), or 1.4. the tubes adjacent within a row (R1, R2) are offset from one another by a longitudinal offset running in the incident flow direction (p), wherein the longitudinal offset being smaller than a longitudinal separation distance of the tubes of the successive rows (R1, R2), wherein the longitudinal offset and the longitudinal separation distance from the centre of adjacent tubes are measured in the incident flow direction (p); 1.5. the tubes penetrate the ribs extending transversely to the tubes and are connected to the ribs via a collar on the ribs; 1.6. the transverse separation distance of the tubes of a row (R1, R2) is greater than the mean width of the ribs measured transversely to the face of the row (R1, R2), so that a gap is present between the ribs of adjacent tubes; 1.7. the ribs are rectangular and have winglets (6a, 6b), wherein a winglet (6a, 6b) is respectively disposed in the corner region of a rib, characterised in that 1.8. the tubes have an elliptical cross-section such that the gap has a width of 0.1- to 0.5-fold the mean width of the ribs and that the winglets (6a, 6b) are disposed at a distance from longitudinal sides and transverse sides of the ribs.