A heat exchanger includes a shell, a refrigerant distributor, and a heat transferring unit. The shell has a refrigerant inlet through which at least refrigerant with liquid refrigerant flows and a shell refrigerant vapor outlet. A longitudinal center axis of the shell extends generally parallel to a horizontal plane. The refrigerant distributor is connected to the refrigerant inlet and disposed within the shell. The refrigerant distributor has 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. The heat transferring unit is 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.