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 generally parallel to a horizontal plane; a refrigerant distributor connected to the refrigerant inlet and disposed within the shell, the refrigerant distributor having at least one liquid refrigerant distribution opening that distributes liquid refrigerant and a refrigerant vapor distribution outlet opening longitudinally spaced from the shell refrigerant vapor outlet, and a heat transferring unit disposed inside of the shell below the refrigerant distributor so that the liquid refrigerant discharged from the refrigerant distributor is supplied to the heat transferring unit, wherein the refrigerant distributor extends longitudinally within the shell and includes a first inner distributor casing (21; 62) and a second outer distributor casing (22; 24), the first inner distributor casing (21; 62) is disposed within the second outer distributor casing (22; 24), the first inner distributor casing (21; 62) is connected to the refrigerant inlet, and the first inner distributor casing (21; 62) distributes refrigerant into an interior space of the second outer distributor casing (22; 24) along a longitudinal length of the second outer distributor casing (22; 24), and the second outer distributor casing (22; 24) has the at least one liquid refrigerant distribution opening that distributes liquid refrigerant and the refrigerant vapor distribution outlet opening, wherein the second outer distributor casing (22; 24) includes a first tray part extending longitudinally along the first inner distributor casing (21; 62), and a second canopy part extending longitudinally along the first inner distributor casing (21; 62), characterized in that the first tray part and the second canopy part are connected to each other on lateral sides of the refrigerant distributor in a sealed manner, wherein the second canopy part has a longitudinal length shorter than a longitudinal length of the first tray part to form the refrigerant vapor distribution outlet opening. 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 generally parallel to a horizontal plane; a refrigerant distributor connected to the refrigerant inlet and disposed within the shell, the refrigerant distributor having at least one liquid refrigerant distribution opening that distributes liquid refrigerant and a refrigerant vapor distribution outlet opening longitudinally spaced from the shell refrigerant vapor outlet, and a heat transferring unit disposed inside of the shell below the refrigerant distributor so that the liquid refrigerant discharged from the refrigerant distributor is supplied to the heat transferring unit, wherein the refrigerant distributor extends longitudinally within the shell and includes a first inner distributor casing (21; 62) and a second outer distributor casing (22; 24), the first inner distributor casing (21; 62) is disposed within the second outer distributor casing (22; 24), the first inner distributor casing (21; 62) is connected to the refrigerant inlet, and the first inner distributor casing (21; 62) distributes refrigerant into an interior space of the second outer distributor casing (22; 24) along a longitudinal length of the second outer distributor casing (22; 24), and the second outer distributor casing (22; 24) has the at least one liquid refrigerant distribution opening that distributes liquid refrigerant and the refrigerant vapor distribution outlet opening, wherein the second outer distributor casing (22; 24) includes a first tray part extending longitudinally along the first inner distributor casing (21; 62), and a second canopy part extending longitudinally along the first inner distributor casing (21; 62), characterized in that the first tray part and the second canopy part are connected to each other on lateral sides of the refrigerant distributor in a sealed manner, wherein the second canopy part has a longitudinal length shorter than a longitudinal length of the first tray part to form the refrigerant vapor distribution outlet opening.