A vertical rod baffle heat exchanger comprising: a shell; a tube-sheet; a tube bundle having a plurality of heat exchange tubes extending in an axial direction, wherein the tube bundle is a U-tube bundle comprising a U-bend in the plurality of heat exchange tubes; six or more longitudinal partition plates extending within the tube bundle in a radial direction of the shell along a longitudinal direction of the shell, wherein at least one longitudinal partition plate is a notched longitudinal partition plate that has a notched end at a vertical distance (D n) from the shell; and a plurality of rod baffle rings (111, 112, 113, 114) provided along an axial length of the plurality of heat exchange tubes, wherein the plurality of rod baffle rings (111, 112, 113, 114) have lateral rod baffles (111a, 113a) extending in an X axis in the radial direction and longitudinal rod baffles (112a, 114a) extending in an Y axis in the radial direction, wherein the lateral rod baffles (111a, 113a) and the longitudinal rod baffles (112a, 114a) pass through gaps (116a, 116b) between every two adjacent tubes of the plurality of heat exchange tubes, and the lateral rod baffles (111a, 113a) pass through openings in the notched longitudinal partition plate, and wherein the at least one notched longitudinal partition plate extends a minimum length in the longitudinal direction that is greater than a lowest point at which a tube of the plurality of heat exchange tubes is provided in the U-tube bundle, and wherein the at least one notched longitudinal partition plate extends a length in the radial direction to have the notched end within the tube bundle. a shell; a tube-sheet; a tube bundle having a plurality of heat exchange tubes extending in an axial direction, wherein the tube bundle is a U-tube bundle comprising a U-bend in the plurality of heat exchange tubes; six or more longitudinal partition plates extending within the tube bundle in a radial direction of the shell along a longitudinal direction of the shell, wherein at least one longitudinal partition plate is a notched longitudinal partition plate that has a notched end at a vertical distance (D n) from the shell; and a plurality of rod baffle rings (111, 112, 113, 114) provided along an axial length of the plurality of heat exchange tubes, wherein the plurality of rod baffle rings (111, 112, 113, 114) have lateral rod baffles (111a, 113a) extending in an X axis in the radial direction and longitudinal rod baffles (112a, 114a) extending in an Y axis in the radial direction, wherein the lateral rod baffles (111a, 113a) and the longitudinal rod baffles (112a, 114a) pass through gaps (116a, 116b) between every two adjacent tubes of the plurality of heat exchange tubes, and the lateral rod baffles (111a, 113a) pass through openings in the notched longitudinal partition plate, and wherein the at least one notched longitudinal partition plate extends a minimum length in the longitudinal direction that is greater than a lowest point at which a tube of the plurality of heat exchange tubes is provided in the U-tube bundle, and wherein the at least one notched longitudinal partition plate extends a length in the radial direction to have the notched end within the tube bundle.