An evaporator for the evaporation of a first fluid by means of the heat provided by a second fluid, the second fluid being a hot gas, wherein said evaporator comprises: a first plate and a second plate facing one another and arranged spaced from one another, defining an inner face, the face facing the other plate, and an outer face opposite the inner face; wherein each of the plates (1, 2) comprises a plurality of chambers (1.1, 2.1); an intake manifold of the first fluid and an exhaust manifold of the first fluid located in fluid communication with one another and with at least one different-chamber (1.1, 2.1) of any of -the plates (1, 2); a plurality of heat exchange tubes wherein each of the heat exchange tubes extends between a chamber (1.1) of the first plate and a chamber (2.1) of the second plate; wherein each chamber (1.1, 2.1) of a plate (1, 2) is in fluid communication with two or more chambers (1.1, 2.1) of the other plate (1, 2) by means of at least two heat exchange tubes, except the chambers (1.1, 2.1) in fluid communication with the intake manifold or the exhaust manifold; there being for each of the heat exchange tubes a path of fluid communication from the intake manifold to the exhaust manifold passing through the interior of said heat exchange tube; two side walls extending between the first plate and the second plate housing the plurality of heat exchange tubes and establishing between both a space for the passage of the second fluid, wherein the second fluid enters through an inlet (I 2) and exits through an outlet (O 2); wherein at least one of the chambers (1.1, 2.1) is a cavity which is open through the outer face and it is closed by means of a cap attached to said chamber (1.1, 2.1), characterized in that the inner walls (1.1.1, 2.1.1) of the chamber (1.1, 2.1) in which the cap is housed are perpendicular to the main plane of the plate (1, 2), and in that said cap has walls (7.1) attached to the inner walls (1.1.1, 2.1.1) of said chamber (1.1, 2.1). a first plate and a second plate facing one another and arranged spaced from one another, defining an inner face, the face facing the other plate, and an outer face opposite the inner face; wherein each of the plates (1, 2) comprises a plurality of chambers (1.1, 2.1); an intake manifold of the first fluid and an exhaust manifold of the first fluid located in fluid communication with one another and with at least one different-chamber (1.1, 2.1) of any of -the plates (1, 2); a plurality of heat exchange tubes wherein each of the heat exchange tubes extends between a chamber (1.1) of the first plate and a chamber (2.1) of the second plate; wherein each chamber (1.1, 2.1) of a plate (1, 2) is in fluid communication with two or more chambers (1.1, 2.1) of the other plate (1, 2) by means of at least two heat exchange tubes, except the chambers (1.1, 2.1) in fluid communication with the intake manifold or the exhaust manifold; there being for each of the heat exchange tubes a path of fluid communication from the intake manifold to the exhaust manifold passing through the interior of said heat exchange tube; two side walls extending between the first plate and the second plate housing the plurality of heat exchange tubes and establishing between both a space for the passage of the second fluid, wherein the second fluid enters through an inlet (I 2) and exits through an outlet (O 2); wherein at least one of the chambers (1.1, 2.1) is a cavity which is open through the outer face and it is closed by means of a cap attached to said chamber (1.1, 2.1), characterized in that the inner walls (1.1.1, 2.1.1) of the chamber (1.1, 2.1) in which the cap is housed are perpendicular to the main plane of the plate (1, 2), and in that said cap has walls (7.1) attached to the inner walls (1.1.1, 2.1.1) of said chamber (1.1, 2.1).