Heat transfer device, in particular for an exhaust gas cooler, having - a substantially fluid-tight housing for conducting a first material flow, in particular of a coolant, and - at least one heat-permeable tube extending in the housing for conducting a second material flow, in particular a combustion exhaust gas, - wherein the housing and outer surfaces (12, 13, 14, 15) of the at least one tube form parallel flow paths for the first material flow, which are on the end face side delimited by a base, in which the at least one tube is held, - a connection, via which the first material flow in the region of the base can be guided into the housing, - wherein an outer surface (12, 13, 14, 15) of the at least one tube has a protuberance (16, 17, 18) formed such that the first material flow after entrance into the housing disperses evenly in the region of the base and is substantially evenly distributed onto the flow paths, wherein the tube comprises a metal sheet, which has the outer surface (12, 13, 14, 15), and the protuberance (16, 17, 18) is formed, in particular imprinted in the metal sheet, characterised in - that a porosity factor F of the respective flow paths lies between 60 % and 90 % wherein the porosity factor F is defined as follows F = A _ KM 1 − A _ KM 2 / A _ KM 2 with: A_KM1: coolant-side surface, which is to be attributed to one of the tubes with protuberances/corrugations (as partial surface of the entire cross-section surface) A_KM2: coolant-side surface, which is to be attributed to one of the tubes, but which is blocked with protuberances/corrugations (A-KM1-A_KM2) remaining open surface, through which coolant can still flow, - that the porosity factor F lies in the region of 20 %, in the case of tubes distanced from hotspots, via F approximately 80 %, in the case of tubes situated nearer to hotspots, up to F = 100 %, in the case of tubes situated directly adjoining hotspots, wherein 100 % means a complete pervasiveness without protuberances /corrugations (17, 18), - the porosity factor F in the case of the heat transfer device at the tubes increases starting from the connection from top to bottom. - a substantially fluid-tight housing for conducting a first material flow, in particular of a coolant, and - at least one heat-permeable tube extending in the housing for conducting a second material flow, in particular a combustion exhaust gas, - wherein the housing and outer surfaces (12, 13, 14, 15) of the at least one tube form parallel flow paths for the first material flow, which are on the end face side delimited by a base, in which the at least one tube is held, - a connection, via which the first material flow in the region of the base can be guided into the housing, - wherein an outer surface (12, 13, 14, 15) of the at least one tube has a protuberance (16, 17, 18) formed such that the first material flow after entrance into the housing disperses evenly in the region of the base and is substantially evenly distributed onto the flow paths, wherein the tube comprises a metal sheet, which has the outer surface (12, 13, 14, 15), and the protuberance (16, 17, 18) is formed, in particular imprinted in the metal sheet, characterised in - that a porosity factor F of the respective flow paths lies between 60 % and 90 % wherein the porosity factor F is defined as follows F = A _ KM 1 − A _ KM 2 / A _ KM 2 with: A_KM1: coolant-side surface, which is to be attributed to one of the tubes with protuberances/corrugations (as partial surface of the entire cross-section surface) A_KM2: coolant-side surface, which is to be attributed to one of the tubes, but which is blocked with protuberances/corrugations (A-KM1-A_KM2) remaining open surface, through which coolant can still flow, A_KM1: coolant-side surface, which is to be attributed to one of the tubes with protuberances/corrugations (as partial surface of the entire cross-section surface) A_KM2: coolant-side surface, which is to be attributed to one of the tubes, but which is blocked with protuberances/corrugations (A-KM1-A_KM2) remaining open surface, through which coolant can still flow, - that the porosity factor F lies in the region of 20 %, in the case of tubes distanced from hotspots, via F approximately 80 %, in the case of tubes situated nearer to hotspots, up to F = 100 %, in the case of tubes situated directly adjoining hotspots, wherein 100 % means a complete pervasiveness without protuberances /corrugations (17, 18), - the porosity factor F in the case of the heat transfer device at the tubes increases starting from the connection from top to bottom.