An evaporator includes a cylindrical barrier wall and a cap that fits at an end of the cylindrical barrier wall. The cylindrical barrier wall defines a central axial opening and an outer cylindrical surface. The cap includes an outer surface that is external to the central axial opening and an inner surface that abuts the central axial opening. A portion of the outer cylindrical surface is configured to define a liquid port extending through the outer cylindrical surface of the cylindrical barrier wall.