A liquid evaporator includes a liquid reservoir (3) with a liquid to be evaporated, a heater (9) and an evaporator tube (12). The evaporator tube (12) has a first porous element (1) having a first porosity and with an area in contact with the liquid in the liquid reservoir (3) and a second porous element (2) with a second porosity and with an area present on an evaporator side (50) used to dispense the evaporated liquid, and an area outside the liquid reservoir heated by the heater (9) which is not directly in connection with the liquid. The first porous element and the second porous element are in contact in contact areas with the first porous element forming a wick delivering liquid from the reservoir to the contact area.