A heat exchanger adapted to be used in a vapor compression system, the heat exchanger comprising: a shell having a refrigerant inlet that at least refrigerant with liquid refrigerant flows therethrough and a shell refrigerant vapor outlet, with a longitudinal center axis of the shell extending substantially parallel to a horizontal plane; a refrigerant distributor fluidly communicating with the refrigerant inlet and disposed within the shell, the refrigerant distributor having at least one liquid refrigerant distribution opening that distributes liquid refrigerant; a tube bundle disposed inside of the shell below the refrigerant distributor so that the liquid refrigerant discharged from the refrigerant distributor is supplied to the tube bundle, the tube bundle including a plurality of heat transfer tubes grouped together; and a first upper baffle vertically disposed at a top of the tube bundle, the first upper baffle extending laterally outwardly from the tube bundle toward a first lateral side of the shell, wherein the first upper baffle includes a first upper non-permeable inner portion laterally disposed adjacent to the tube bundle; and a first upper permeable outer portion laterally disposed outwardly of the first upper non-permeable inner portion, and being adjacent to the first lateral side of the shell, wherein the first upper baffle is formed of a non-permeable material with holes formed therein to form the first upper permeable portion, characterised in that the first upper baffle comprises a flange portion extending downwardly from the outer edge of the first upper permeable outer portion and wherein said flange portion abuts the lateral side of the shell. a shell having a refrigerant inlet that at least refrigerant with liquid refrigerant flows therethrough and a shell refrigerant vapor outlet, with a longitudinal center axis of the shell extending substantially parallel to a horizontal plane; a refrigerant distributor fluidly communicating with the refrigerant inlet and disposed within the shell, the refrigerant distributor having at least one liquid refrigerant distribution opening that distributes liquid refrigerant; a tube bundle disposed inside of the shell below the refrigerant distributor so that the liquid refrigerant discharged from the refrigerant distributor is supplied to the tube bundle, the tube bundle including a plurality of heat transfer tubes grouped together; and a first upper baffle vertically disposed at a top of the tube bundle, the first upper baffle extending laterally outwardly from the tube bundle toward a first lateral side of the shell, wherein the first upper baffle includes a first upper non-permeable inner portion laterally disposed adjacent to the tube bundle; and a first upper permeable outer portion laterally disposed outwardly of the first upper non-permeable inner portion, and being adjacent to the first lateral side of the shell, wherein the first upper baffle is formed of a non-permeable material with holes formed therein to form the first upper permeable portion, characterised in that the first upper baffle comprises a flange portion extending downwardly from the outer edge of the first upper permeable outer portion and wherein said flange portion abuts the lateral side of the shell. a first upper non-permeable inner portion laterally disposed adjacent to the tube bundle; and a first upper permeable outer portion laterally disposed outwardly of the first upper non-permeable inner portion, and being adjacent to the first lateral side of the shell, wherein the first upper baffle is formed of a non-permeable material with holes formed therein to form the first upper permeable portion, characterised in that the first upper baffle comprises a flange portion extending downwardly from the outer edge of the first upper permeable outer portion and wherein said flange portion abuts the lateral side of the shell.