Heat exchanger system for Rankine cycles

Abstract

Heat exchanger system for cooling the exhaust steam of a turbine during the production of electrical energy, which consists of a regenerator (12) for pre-cooling the exhaust steam and pre-heating the condensate and a condenser (13) for liquefying the steam by means of a coolant, the regenerator (12) and the condenser (13) are located in a common cylindrical shell (1) facing the environment, the regenerator (12) and the condenser (13) lie radially with part or in whole over the same section of the longitudinal axis (10) of the vessel and the steam inlet nozzle (2) is located between the two ends of the cylindrical shell (1), characterized in that the regenerator (12) consists of two parts, so that the steam (20) flowing into the shell (1) splits radially to the longitudinal axis (10) of the vessel, flows around the condenser (13) and flows into it on the opposite side.

Description

The invention describes a heat exchanger system which cools and condenses the expanded exhaust steam downstream of a turbine in plants for power generation. The invention relates to the connection, the structure and the arrangement of the two functional units "regenerator" and "condenser" necessary for cooling and for condensation.ApplicationFor converting thermal energy into electrical energy, a liquid working medium is evaporated in so-called Rankine processes, expanded over a turbine and then condensed. The condensate is then fed again to the evaporation via a pump (feed pump). In most working media, the expanded steam after the turbine has not yet cooled to the condensation temperature. The heat contained in this superheating can be used for preheating the liquid working medium from the condenser (condensate) downstream of the feed pump. The heat exchanger used for this purpose is referred to here as a regenerator.The regenerator and condenser are connected in series on the steam side downstream of the turbine (series connection). The expanded steam from the turbine is first passed through the regenerator, cooled here to near the condensation temperature and then liquefied in the condenser. The pressure loss caused by the heat exchangers and the efficiency of the regenerator are decisive for the efficiency of the entire system. In particular in small, compact installations, the design, the arrangement and connection of the two heat exchangers determine the costs of the overall installation.Prior ArtThe published patent application CA 2 589 781 A1 discloses a heat exchanger system for cooling the exhaust steam of a turbine during the production of electrical energy, which system comprises a regenerator for precooling the exhaust steam and preheating the condensate and a condenser for liquefying the exhaust steam by means of coolant. For this purpose, two heat exchangers are located in a common cylindrical shell to the environment, both heat exchangers lie radially with part or all over the same section of a container axis, and an inlet opening for the steam is located between the two ends of the cylindrical shell.Patent EP 1 426 565 A1 again describes a system in which the condenser and regenerator are arranged in a common shell. The shell is in the form of a cylinder. The steam is fed to the system via an axially aligned stub at the head or end of this cylinder. The regenerator is located as a unit above or below the condenser. The steam flows in parallel to the container axis. It is deflected by 90°, conducted to the inlet of the regenerator and, after it has passed straight through, conducted into the condenser. The condensate obtained is conducted out of the container.SUMMARY OF THE INVENTIONThe invention describes a regenerator and condenser system which is of substantially more compact construction than the known prior art. The structural volume and weight of the heat exchanger system and thus the costs are reduced.At the same time, despite the more compact construction, the efficiency of the heat transfer is increased and the pressure losses are reduced. The efficiency and thus the benefit of the entire plant are thus increased.Brief Description of the DrawingsThe attached schematic drawings illustrate the invention, its advantages, differentiation from the prior art and variants of the embodiment. FIG. 1 ) shows the known prior art as a representation of the system cross section shown in the patent EP 1 426 565 A1 / 6. FIG. 2 ) serves, on the basis of a similar cross section through a variant of the system described in the invention, to show advantages and a delimitation from the prior art. FIGS. 3-6 ) illustrate the function of a variant of the invention on the basis of different representation methods.FIGS. 10 ) show cross-sections of various variations of the invention. FIG. 11 ) illustrates in a longitudinal section in more detail the internal structure of the novel heat exchanger system.DESCRIPTION OF THE INVENTIONThe two heat exchanger units regenerator (12) and condenser (13) are located in a common cylindrical shell (1). The expanded exhaust steam of a turbine is conducted via a connecting piece (2) into the casing (1) at right angles to a parallel of the container axis (10). It is distributed uniformly to the container axis (10) in a provided space (11) and passed through the regenerator. After that, it flows into the condenser and is liquefied. The condensate is discharged from the container at a suitable point. For the purpose of flow guidance and insulation, regenerator and condenser are surrounded by a casing (14, 18).As in the prior art shown in FIG. 1 ), regenerator ( 12) and condenser ( 13) are located in a common shell ( 1). In contrast to FIG. 1, in the invention FIG. 2 ) the regenerator ( 12) is constructed such that the steam ( 20) flowing through describes a curved path around the condenser ( 13) lying parallel to the same axis. In contrast to FIG. 1 ), the steam feed ( 2) is expediently located on the radial side of the common cylindrical container ( 1).In a variant of the invention according to FIG. 2 ), the same sizes were chosen for the heat exchangers ( 12) and ( 13) lying in the common shell ( 1) as in the prior art according to FIG. 1 ). The comparison of FIGS. 1 ) and 2 ) reveals the considerable saving in space. It is also clear that the flow guidance is greatly improved.In the known arrangements of regenerator and condenser, the installation space present in the common shell of the condenser (13) and of the regenerator (12) is not optimally utilized. Furthermore, pressure losses arise as a result of repeated changes in the cross section and the direction along the path of the steam to the condenser.In the invention, the system consisting of regenerator and condenser is constructed in such a way that the installation space is used as well as possible and at the same time lower pressure losses are produced than in the known prior art. To achieve this, the regenerator (12) is curved about the longitudinal axis of the condenser. The steam can flow through the regenerator (12) into the condenser (13) at the maximum radius of steam inlet (20). For distributing the steam after entering the container (1) along the container axis (10), the space (11) is sufficient.FIG. 3 ) shows the view of a variant 1 of the novel heat exchanger system from the outside. The connection piece (2) for supplying steam, which is rotated through 90° with respect to the container axis (10) of the system casing (1), can be seen.FIG. 4 ) shows the basic internal structure and FIG. 5 ) shows the cross section of variant 1. The steam stream (20a), after entering the vessel, distributes itself in the space (11) before it flows (20b) around the tubes (12) of the register of the regenerator and then flows into the condenser. For this purpose, a part of the shell of the condenser ( 14) is opened and thus enables the entry of the vapor stream ( 20 c). In variant 1, the condensate is collected in the condenser shell (14) and flows out of the container (1) through a connection piece (7). The condensate flows in the tubes of the register (21) of the regenerator (12) from the inlet connection (8) counter to the direction of the steam flow (20), here in cross countercurrent, to the outlet connection. In FIG. 6 ), the cross section from FIG. 5 ) is abstracted and only the cross-sectional areas of the functional units are shown. Connections for additional discharge of condensate and inert gas are not shown.The principle of the invention described can now be modified according to requirements. This is illustrated by FIGS. 7 ) to 10 ). In variant 1, FIG. 6 ), the vapor inlet is parallel to the tangent of the container axis. The condenser is arranged in the upper part of the container. As a result, the condensate can escape at a high level when the container is oriented horizontally. In compact installations, the admission pressure of the downstream feed pump thus increases. However, additional measures must be taken to remove the condensate accumulating in the container jacket when the plant is at a standstill and when it is started up. A characteristic of this variant is the steam inlet below the condenser.In variant 2, FIG. 7 ), the steam is guided to the regenerator above the condenser and flows on the side or from below the condenser. The condensate flowing from the condenser is discharged from the jacket. The magnitude of the admission pressure of the downstream feed pump thus falls. However, no additional measures are necessary for the starting operation.In variant 3 in FIG. 8 ), the regenerator is arranged symmetrically about the condenser bundle. It corresponds to variant 1, but the structure of the register is simpler, since it is rotationally symmetrical. The condenser bundle is also located in the center.Variant 4 in FIG. 9 ) corresponds to variant 2, however, with a rotationally symmetrical register.Variant 5 in FIG. 10 ) differs from the preceding variants in that the vapor and liquid flow through the register ( 12) flows around the condenser ( 13) on both sides and enters the condenser on the opposite side. This allows the cross section of the entire system to be reduced.In FIG. 11 ), the structure of the system is shown in even more detail by a section along the container axis ( 10) of variant 5 in FIG. 10 ). The entry of steam into the condenser (17) can be seen. The fastening (15) and flow guidance through the register are also shown. In this variant, the register is also surrounded by an additional jacket (18) to the outer jacket (1) and to the capacitor jacket (14). As a result, thermal stresses in the casing are reduced and the capacitor space ( 13) is not unnecessarily heated. However, the additional outlay is only appropriate for large systems.List of reference charactersFIG. 1 ) shows the prior art according to patent EP 1 426 565 A1 FIG. 2 ) shows a cross section of a variant of the invention for delimiting from the prior art according to FIG. 1 ) FIG. 3 ) is an external view of the heat exchanger system of Variation 1 FIG. 4 ) Material stream 3D in the heat exchanger system variant 1 FIG. 5 ) shows a cross section of heat exchanger system variant 1 FIG. 6 ) is a cross section of the functional units in the system variant 1 FIG. 7 ) is a cross section of the functional units in the system variant 2 FIG. 8 ) shows a cross section of the functional units in the system variant 3 FIG. 9 ) shows a cross section of the functional units in the system variant 4 FIG. 10 ) shows a cross section of the functional units in the system variant 5 FIG. 11 ) is a longitudinal section of the heat exchanger system of variant 51 Outer shell 2 steam inlet connection 3 plug connection for tube bundles condenser 4 cover plate tube bundle condenser 5 connection for cooling water outlet condenser 6 connection for cooling water inlet condenser 7 connection for condensate outlet condenser 8 connection for condensate inlet regenerator 9 connection for condensate outlet regenerator 10 container axis 11 distribution space for steam 12 register regenerator (finned tubes) 13 tube bundle condenser (U tubes) 14 shell condenser 15 lateral fastening for regenerator tubes 16 support for regenerator tubes 17 steam inlet in condenser 18 baffle plates regenerator 19 deflection or tube connection of regenerator tubes 20 steam flow a) through inlet connection b) through register regenerator c) in condenser 21 cooling water flow in the tube bundle condenser 22 condensate flow in register regenerator

Claims

Heat exchanger system for cooling the exhaust steam of a turbine during the production of electrical energy, which system consists of a regenerator (12) for precooling the exhaust steam and preheating the condensate and a condenser (13) for liquefying the steam by means of coolant, the regenerator (12) and the condenser (13) are located in a common cylindrical shell (1) to the environment, the regenerator (12) and the condenser (13) are located radially with a part or overall over the same section of the container longitudinal axis (10), and the steam inlet connection piece (2) is located between the two ends of the cylindrical shell (1), characterized in that the regenerator (12) consists of two parts, so that the steam (20) flowing into the shell (1) divides radially to the container longitudinal axis (10), The condenser (13) is surrounded by a flow of water and flows into the latter on the opposite side.Heat exchanger system according to Claim 1, characterized in that the regenerator (12) is curved about a longitudinal axis of the condenser (13), wherein the regenerator (12) engages around or encloses the condenser (13) at least partially following a peripheral line of the condenser (13).Heat exchanger system according to one of the preceding claims, characterized in that the steam inlet connection piece (2) is arranged at right angles to a parallel of the container longitudinal axis (10), wherein the steam (20) can flow at maximum radius from the steam inlet connection piece (2) through the regenerator (12) into the condenser (13).Heat exchanger system according to one of the preceding claims, characterized in that the condenser (13) is surrounded by a casing (14) which is at least partially open in order to allow the steam inlet (17) into the condenser (13).Heat exchanger system according to one of the preceding claims, characterized in that the condenser (13) is arranged in the container coaxially with respect to the container longitudinal axis (10).Use of a heat exchanger system according to one of the preceding claims in a plant for carrying out a Rankine cycle.

Images