Falling film evaporator

Heat exchanger (1,100,200) of horizontal tube falling film evaporator type, said heat exchanger (1,100,200) comprising

• a shell (10,110,210),
• at least one bundle (20,120,140,220,240) of heat exchanger tubes (21,121,141,221,241) that is arranged within the shell (10,110,210), said heat exchanger tubes (21,121, 141,221,241) having a tube length (Lt) defining a horizontal x-direction and said bundle (20,120,140,220,240) of heat exchanger tubes (21,121,141,221,241) having a vertical extension (Htb, Htb1, Htb2) defining a z-direction that is orthogonal to said x-direction, and
• at least one refrigerant distribution layer (30,130,150,230a,230b,250a,250b) located above at least one bundle (20,120,140,220,240) of heat exchanger tubes (21,121,141,221,241), said at least one refrigerant distribution layer (30,130,150,230a, 230b,250a,250b) comprising perforated pipes (31,131,151) which have holes (133a.1,133a.2,133a.3,133a.4,133a.5, 133a.6,133a.7) for emitting refrigerant towards the bundle (20,120,140,220,240) of heat exchanger tubes (21,121,141,221,241) above which said refrigerant distribution layer (30,130,150,230a,230b, 250a,250b) is located, characterized in that at least some of said perforated pipes (31,131,151) have a longitudinal axis defining a horizontal y-direction that is orthogonal to the x-direction defined by said heat exchanger tubes (21,121,141,221,241) and that perforations of the perforated pipes (31,131,151) are formed by holes (133a.1,133a.2,133a.3,133a.4,133a.5,133a.6,133a.7) that are arranged in sets (133a,133b,133c,133d), wherein each set (133a,133b,133c,133d) of holes is arranged on a circumference, which circumference is lying on a vertical xz-plane that passes through a heat exchanger tube (21,121,141,221,241) of the bundle (20,120,140,220,240) and wherein the holes of a given set (133a,133b,133c,133d) of holes are located above a respective heat exchanger tube (121a.1,121a.2,121b.1,121b.2, 141a.1,141a.2,141b.1, 141b.2) of said bundle (20,120,140,220,240) of heat exchanger tubes (21,121,141,221,241), so that refrigerant emitted from the holes of a given set (133a,133b,133c, 133d) of holes propagates towards this heat exchanger tube (121a.1,121a.2,121b.1,121b.2,141a.1,141a.2,141b.1,141b.2).