A heat transfer system, as the system for transferring heat between a first fluid and a second fluid, which has an arrangement composed of pipe elements (3, 3a, 3b, 3c) for passing through the first fluid, one or more pipe bottoms having a through opening, and one or more sealing elements having a through opening, wherein the pipe elements (3, 3a, 3b, 3c) are formed of a flat pipe having a first region having a first height X and a depth W and one or more second regions having a support surface arranged on one end portion of the pipe elements (3, 3a, 3b, 3c) and having a second height Y, respectively, wherein the sealing element is arranged between the edge of the through opening of the pipe bottom, and having a wall thickness G, respectively, wherein the pipe elements (3, 3a, 3b, 3c) having a wide side are aligned in a state aligned parallel to each other and at an interval F with respect to each other in the first region, respectively, wherein a web having a height H is provided between the through openings arranged adjacent to each other of the pipe bottom, respectively, wherein when viewing in a height direction c, an extension part inside the first region of the pipe elements (3, 3a, 3b, 3c) appeared from a value obtained by adding a first height X of the pipe elements (3, 3a, 3b, 3c) to the interval F corresponds to an extension part inside the second region of the pipe elements (3, 3a, 3b, 3c) appeared from a value obtained by adding a second height Y of the pipe elements (3, 3a, 3b, 3c) to the height H of the web of the pipe bottom and two times the wall thickness G of the sealing element, and wherein CM = F - H = Y - X + 2·G, the CM in the equation refers to the deformation degree of the end portion of the pipe elements (3, 3a, 3b, 3c) in the height direction c, is placed within a range between the maximum value CM max and the minimum value CM min, and the CM min appears as CM min = 2·G when the heights X, Y of the pipe elements (3, 3a, 3b, 3c) are the same, characterized in that the pipe bottom has a ring element for locally reducing the opened lateral cross section of the through opening for receiving the sealing element and the pipe elements (3, 3a, 3b, 3c) in the region of the web in order to locally increase the compression of the sealing element in the region. as the system for transferring heat between a first fluid and a second fluid, which has an arrangement composed of pipe elements (3, 3a, 3b, 3c) for passing through the first fluid, one or more pipe bottoms having a through opening, and one or more sealing elements having a through opening, wherein the pipe elements (3, 3a, 3b, 3c) are formed of a flat pipe having a first region having a first height X and a depth W and one or more second regions having a support surface arranged on one end portion of the pipe elements (3, 3a, 3b, 3c) and having a second height Y, respectively, wherein the sealing element is arranged between the edge of the through opening of the pipe bottom, and having a wall thickness G, respectively, wherein the pipe elements (3, 3a, 3b, 3c) having a wide side are aligned in a state aligned parallel to each other and at an interval F with respect to each other in the first region, respectively, wherein a web having a height H is provided between the through openings arranged adjacent to each other of the pipe bottom, respectively, wherein when viewing in a height direction c, an extension part inside the first region of the pipe elements (3, 3a, 3b, 3c) appeared from a value obtained by adding a first height X of the pipe elements (3, 3a, 3b, 3c) to the interval F corresponds to an extension part inside the second region of the pipe elements (3, 3a, 3b, 3c) appeared from a value obtained by adding a second height Y of the pipe elements (3, 3a, 3b, 3c) to the height H of the web of the pipe bottom and two times the wall thickness G of the sealing element, and wherein CM = F - H = Y - X + 2·G, the CM in the equation refers to the deformation degree of the end portion of the pipe elements (3, 3a, 3b, 3c) in the height direction c, is placed within a range between the maximum value CM max and the minimum value CM min, and the CM min appears as CM min = 2·G when the heights X, Y of the pipe elements (3, 3a, 3b, 3c) are the same, characterized in that the pipe bottom has a ring element for locally reducing the opened lateral cross section of the through opening for receiving the sealing element and the pipe elements (3, 3a, 3b, 3c) in the region of the web in order to locally increase the compression of the sealing element in the region.