A cooling unit comprising: (a) a cooling cartridge having: (i) two foils sealed to one another along a perimeter area delimiting an inner area of the cartridge where a liquid pathway is defined between both foils, the liquid pathway making a fluid communication between an inlet and an outlet of the cooling cartridge; (ii) a web or mesh of material provided between both foils in the inner area of the cooling cartridge in the liquid pathway, the web or mesh of material comprising contact zones configured to contact the foils of the cooling cartridge when the pressure reigning in the inner area equals ambient pressure; (b) a first cooling plate comprising a first surface and a second cooling plate comprising a second surface facing the first surface; (c) a cold source suitable for cooling said first and second surfaces, wherein the inner area of the cooling cartridge is positioned between both cooling surfaces; wherein the foils are not or only at distinct locations attached to the contact zones of the web or mesh material, the web or mesh of material comprises wall parts defining the contact zones between the web or mesh of material and the foils, the web or mesh of material disposed between both foils comprising a perimeterwall defining the perimeter of the cooling cartridge with both foils sealed to the perimeter wall, the web or mesh of material extending in the inner area defining a non-rectilinear trajectory of the liquid pathway between the foils, and wherein the part of the foils situated in the inner area is stretchable or has dimensions larger than the inner area, such as to allow that the foils are at least locally spaced apart from the wall parts in a direction perpendicular to the cooling surfaces when the inner volume of the liquid pathway is pressurized, thereby creating short-cuts in the trajectory of the liquid pathway. (a) a cooling cartridge having: (i) two foils sealed to one another along a perimeter area delimiting an inner area of the cartridge where a liquid pathway is defined between both foils, the liquid pathway making a fluid communication between an inlet and an outlet of the cooling cartridge; (ii) a web or mesh of material provided between both foils in the inner area of the cooling cartridge in the liquid pathway, the web or mesh of material comprising contact zones configured to contact the foils of the cooling cartridge when the pressure reigning in the inner area equals ambient pressure; (i) two foils sealed to one another along a perimeter area delimiting an inner area of the cartridge where a liquid pathway is defined between both foils, the liquid pathway making a fluid communication between an inlet and an outlet of the cooling cartridge; (ii) a web or mesh of material provided between both foils in the inner area of the cooling cartridge in the liquid pathway, the web or mesh of material comprising contact zones configured to contact the foils of the cooling cartridge when the pressure reigning in the inner area equals ambient pressure; (b) a first cooling plate comprising a first surface and a second cooling plate comprising a second surface facing the first surface; (c) a cold source suitable for cooling said first and second surfaces, wherein the inner area of the cooling cartridge is positioned between both cooling surfaces; wherein the foils are not or only at distinct locations attached to the contact zones of the web or mesh material, the web or mesh of material comprises wall parts defining the contact zones between the web or mesh of material and the foils, the web or mesh of material disposed between both foils comprising a perimeterwall defining the perimeter of the cooling cartridge with both foils sealed to the perimeter wall, the web or mesh of material extending in the inner area defining a non-rectilinear trajectory of the liquid pathway between the foils, and wherein the part of the foils situated in the inner area is stretchable or has dimensions larger than the inner area, such as to allow that the foils are at least locally spaced apart from the wall parts in a direction perpendicular to the cooling surfaces when the inner volume of the liquid pathway is pressurized, thereby creating short-cuts in the trajectory of the liquid pathway.