Patent Publication Number: US-2010115949-A1

Title: Condensing equipment

Description:
TECHNICAL FIELD 
     The present invention relates to a condensing equipment or facility that converts discharge steam after driving a steam turbine in a nuclear power plant or the like into condensate, and more particularly, to a condensing equipment in which a plurality of condensers are arranged in series. 
     BACKGROUND TECHNOLOGY 
     For example, a nuclear power plant employs a recirculation system in which steam generated in a nuclear reactor is supplied to a steam turbine to drive a power generator so as to generate power, the steam that has served to generate power is subsequently converted into condensate by a condensing equipment, and the condensate is thereafter supplied again as cooling water to the nuclear reactor. 
     Normally, at a nuclear power plant with a large capacity having a power generation output in the 1000 MW class, steam turbines that rotate a power generator include high pressure turbines which are driven by steam that is generated at a nuclear reactor, and low pressure turbines which are driven by the steam that has served to drive the high pressure turbines. 
     Two or three turbines are installed as the low pressure turbines, and the steam discharged after serving to drive the plurality of low pressure turbines is guided to a condensing equipment including a plurality of condensers, in which the steam is converted into condensate. 
     A condensing equipment of a nuclear power plant will be described hereunder with reference to  FIG. 4 . As shown in  FIG. 4 , steam S 1  generated in a nuclear reactor  100  and fed to a high pressure turbine  102  via steam piping  101  becomes a low pressure steam S 2  and is fed via turbine piping  103  to a plurality of low pressure turbines, for example, three low pressure turbines  10 ,  11  and  12 , and serves to drive a power generator  104 . A discharge steam (S 3 ) that is discharged from the low pressure turbines  10 ,  11  and  12  is supplied to, for example, three shell-type condensers  1 ,  2  and  3  provided with three condenser shells. 
     Cooling tubes  4 ,  5  and  6  are arranged within the shells  1   a ,  2   a  and  3   a  of the condensers  1 ,  2  and  3 , respectively. Cooling waters w 1 , w 2  and w 3  are supplied into these cooling tubes  4 ,  5  and  6 , respectively, from a cooling water supply line  104 . Steam S 3  that has been discharged after driving the three low pressure turbines  10 ,  11  and  12  and guided to the condensers  1 ,  2  and  3  passes outside the cooling tubes  4 ,  5  and  6  provided inside the shells  1   a ,  2   a  and  3   a . At that time, the steam S 3  exchanges heat with the cooling water w 1 , w 2  and w 3  that flow through the inside of the cooling tubes  4 ,  5  and  6 , respectively, and is then condensed to thereby form condensates  19 ,  20  and  21 . The condensates  19 ,  20  and  21  are collected in hot wells  16 ,  17  and  18  provided below the respective condensers  1 ,  2  and  3 . 
     The condensates  19 ,  20  and  21  collected in the hot wells  16 ,  17  and  18  are discharged to a condensate pipe  105  by a condensate pump  22  that is provided in the vicinity of the condensers  1 ,  2  and  3 . Further, the condensates  19 ,  20  and  21  are pressurized by a reactor feed water pump  23  and guided to a nuclear reactor  100 . 
     In this connection, in some cases, the condensate pump  22  may be referred to as a low pressure condensate pump. In that case, a pump referred to as a high pressure condensate pump may be further provided in some cases at a position on the downstream side thereof. 
     With respect to the cooling waters w 1 , w 2  and w 3  flowing through the inside of the cooling tubes  4 ,  5  and  6 , in some cases, the cooling waters w 1 , w 2  and w 3  are introduced in parallel to the respective condensers  1 ,  2  and  3  as shown in  FIG. 4 , and in some cases, the cooling waters w 1 , w 2  and w 3  are introduced in series using a serial piping configuration as shown in  FIG. 5 . 
     As shown in  FIG. 4 , when the cooling waters w 1 , w 2  and w 3  are introduced in parallel, the cooling waters of the same temperature and the same flow rate are introduced into the plurality of condensers  1 ,  2  and  3 . Accordingly, heat exchanges with the steams S 3  that are guided to the condensers  1 ,  2  and  3  after serving to drive the low pressure turbines  10 ,  11  and  12  and being discharged therefrom are performed under the same conditions at the respective condensers  1 ,  2  and  3 . 
     In contrast, as shown in  FIG. 5 , when the cooling water w is introduced in series, since the cooling water w is introduced in sequence into the plurality of condensers  1 ,  2  and  3 , the temperature of the cooling water at the condenser  1  to which the cooling water w is introduced first is low, and the temperature of the cooling water w rises at the condensers  2  and  3  to which the cooling water w is introduced thereafter. Accordingly, the heat exchange with the steam S 3  that is guided to the condensers  1 ,  2  and  3  after serving to drive the low pressure turbines  10 ,  11  and  12  and being discharged therefrom is performed under respectively different conditions at the respective condensers  1 ,  2  and  3 . 
     Since the steams S 3  become saturated state at the time of being condensed into condensate on the outside of the cooling tubes  4 ,  5  and  6 , if the temperatures of the cooling water w 1 , w 2  and w 3  are different in the respective condensers  1 ,  2  and  3 , the pressures on the outside of the cooling tubes  4 ,  5  and  6  will also become different. In general, the condensers in which internal pressures differ with respect to a plurality of shells in a manner such as described above are referred to as “multiple pressure condensers”. In the case of the multiple pressure condensers, since the respective internal pressures differ in the condensers  1 ,  2  and  3 , in some cases, the sizes of the condensers  1 ,  2  and  3  are changed in consideration of balancing the heat exchange amounts and the like. 
       FIG. 6  is a view that shows the configuration of the shells  1   a ,  2   a  and  3   a  of the condensers  1 ,  2  and  3  shown in  FIG. 5  as a plan view. As shown in  FIG. 6 , in the case of the multiple pressure condensers comprising three shells, in some cases, the sizes of the condensers may be made so as to gradually increase along the steam supply direction, with the sizes set to condenser  1 &lt;condenser  2 &lt;condenser  3 . 
     However, it is usual to make the sizes of the plurality of low pressure turbines  10 ,  11  and  12  the same even when the sizes of the condensers  1 ,  2  and  3  are changed in this manner. Thus, since the plurality of low pressure turbines  10 ,  11  and  12  have the same rotational axis, it is common that the plurality of condensers  1 ,  2  and  3  disposed thereunder are also arranged on the same center line O as shown in  FIG. 6 , in which reference numerals  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33  and  34  denote circulation water pipes, respectively, which guide the cooling water to the condensers  1 ,  2  and  3 , respectively. 
     In the configuration shown in  FIG. 6 , the cooling water w is first guided to the condenser  1  by a circulation water pipe  27  on the upstream side. After the temperature of the cooling water “w” flowing inside the cooling tubes  4  is raised by the heat exchange with the steam that passes the outside of the cooling tubes  4 , the cooling water “w” is discharged from the condenser  1 , passes through the circulation water pipes  28 ,  29  and  30 , and is then guided to the condenser  2  at the next stage. The cooling water “w” that is guided to the condenser  2  flows through the inside of the cooling tubes  5 . After the temperature of the cooling water w is raised by the heat exchange with the steam that passes the outside of the cooling tubes  5 , the cooling water w is discharged from the condenser  2 , passes through the circulation water pipes  31 ,  32  and  33 , and is then guided to the condenser  3 . The cooling water w that is guided to the condenser  3  flows through the inside of the cooling tubes  6 . After the temperature of the cooling water w is raised by the heat exchange with the steam that passes the outside of the cooling tubes  6 , the cooling water w is discharged from the condenser  3 , passes through the circulation water pipe  34  and is then discharged. 
     Furthermore, as mentioned above, the steam that is discharged after serving to drive the low pressure turbines and is guided to the condensers is condensed into condensate from the steam obtained through the heat exchange with the cooling water w flowing through the inside of the cooling tubes  4 ,  5  and  6  when the steam passes the outside of the cooling tubes  4 ,  5  and  6 , and the condensate is collected in a hot well below the condenser. In the case of the multiple pressure condensers, the condensates collected in the hot wells below the condensers are fed from the hot well of the low-pressure side condenser to the hot well of the high-pressure side condenser in the order of the condenser  1 , the condenser  2  and the condenser  3 , and are then finally discharged by the condensate pump  22  disposed in the vicinity of the condenser  3 . 
     At a power plant, there are various heat exchange apparatus such as a feed water heater and a moisture separator heater, and drainage discharged from those apparatus is generally recovered in a condenser. When the condenser is a type having three shells, there is almost no space to connect a pipe that recovers drainage to the condenser  2  disposed in the center, so that, as shown by drainage pipes  35 ,  36 ,  37  and  38  in  FIG. 6 , normally, there is adopted a configuration in which drainage recovery pipes are mainly connected to the condenser  1  and the condenser  3  and are not connected to the condenser  2 . 
     Further, Patent Document 1 (Japanese Patent Laid Open No. 8-21205) as a published literature discloses technology in which there are different degrees of vacuum in a plurality of condensers and the mean degree of vacuum thereof is equivalent or greater than a single degree of vacuum. However, Patent Document 1 does not mention anything in particular regarding a method of arranging a plurality of shells of different sizes or the like. 
     In a planar arrangement of the conventional common multiple pressure condenser such as shown in  FIG. 6 , when the plurality of condensers  1 ,  2  and  3  are arranged on the same center line O, the lengths of the shells gradually increase in the order of condenser  1 ,  2  and  3 . Hence, in the configuration, the positions of the cooling water outlets and the cooling water inlets are out of alignment. More specifically, in  FIG. 6 , when a length  11  of the outlet circulation water pipe  28  of the condenser  1  is compared with a length  12  of the inlet circulation water pipe  30  of the condenser  2 , the circulation water pipe  28  becomes longer even when the length  11  is made to have the shortest length, thus being inconvenient. Similarly, the piping positions of the outlet circulation water pipe  31  of the condenser  2  and the inlet circulation water pipe  33  of the condenser  3  are out of alignment, so that even if the circulation water pipe  33  is made to have the shortest length, when a length  13  of the outlet circulation water pipe  31  of the condenser  2  and a length  14  of the inlet circulation water pipe  33  of the condenser  3  are compared, it is found that the circulation water pipe  31  becomes longer even when the length  13  is made to have the shortest length. More specifically, a problem arises such that the piping loss increases by the amount that the circulation water pipe  28  and the circulation water pipe  31  become longer. 
     Further, in an arrangement in which the condensers  1 ,  2  and  3  are disposed on the same center line, the positions of the cooling water inlets and outlets of the condensers  1 ,  2  and  3  deviate little by little, respectively, from the condenser center line. Therefore, it is necessary for the condensate pumps  22  to be arranged at sufficiently separated positions (lower portion of the illustration in  FIG. 6 ) so as not to interfere with the circulation water pipes  27  to  34  into or from which the condensers  1 ,  2  and  3  are inserted or withdrawn. 
     Furthermore, regarding drainage recovery pipes that are connected to the condensers from various heat exchange apparatus such as a feed water heater and a moisture separator heater, since there is almost no space for connecting the drainage recovery pipe to the condenser  2  which is disposed in the center, the number of drainage recovery pipe connections to the condensers  1  and  3  increases, and therefore, the drainage recovery piping is complex, thus providing a problem. Moreover, since there is a shortage of space for connecting the drainage recovery pipes to the condensers  1  and  3 , the condensers  1  and  3  must be made larger, thus also providing a problem. 
     DISCLOSURE OF THE INVENTION 
     The present invention has been made in consideration of the above circumstances, and it is an object of the invention to provide a condensing equipment in which lengths of circulation pipes of respective condensers are made shorter and equal to thereby prevent an arrangement of a drainage recovery piping from being complex, and moreover, in which a space for connecting the drainage recovery pipings to the condensers can be secured without additionally increasing the size of condensers. 
     In a condensing equipment of the present invention provided for achieving the above object, a plurality of condensers having shells different lengths in longitudinal direction from each other are arranged in parallel with each other and connected in series by circulation water pipes, wherein the respective condensers have center positions different in level in the longitudinal direction of the shells, respectively, and an inlet side circulation water pipe of one condenser and an outlet side circulation pipe of the condenser adjacent to the above one condenser among the condensers are arranged so as to be made coincident in length with each other. 
     Further, in a condensing equipment of the present invention provided for achieving the above object, a steam generated at a power plant is supplied to a steam turbine to thereby drive a generator and a discharged steam is cooled into condensate by a plurality of condensers arranged in parallel with each other, wherein the plurality of condensers having shells different in lengths in longitudinal direction from each other are arranged in parallel with each other and connected in series by circulation water pipes, in which the respective condensers have center positions different in level in the longitudinal direction of the shells, respectively, and an inlet side circulation water pipe of one condenser and an outlet side circulation pipe of the condenser adjacent to the above one condenser among the condensers are arranged so as to be made coincident in length with each other. 
     In the above condensing equipment, it may be desired that the plurality of condensers are arranged such that a cooling water outlet of one condenser and a cooling water inlet of another condenser adjacent to the above one condenser are aligned in positions thereof to thereby create a space in a vicinity of the condenser and a condensate pump is disposed in the space. 
     In the above condensing equipment, it may be desired that three condensers having different sizes are arranged such that a cooling water outlet of one condenser and a cooling water inlet of another condenser adjacent to the above one condenser are aligned in positions thereof to thereby create a space in a vicinity of a central condenser, and a drainage recovery pipe is connected in the space. 
     According to the present invention, the lengths of circulation pipes of respective condensers can be made shorter and equal to thereby prevent drainage recovery piping from being complex, and moreover, it becomes possible to secure a space for connecting drainage recovery pipes to the condensers without additionally increasing the size of condensers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a diagram representing a configuration of a condenser according to a first embodiment of the present invention. 
         FIG. 2  shows a diagram representing a configuration of a condenser according to a second embodiment of the present invention. 
         FIG. 3  shows a diagram representing a configuration of a condenser according to a third embodiment of the present invention. 
         FIG. 4  shows a diagram representing a configuration of a condenser according to a conventional example. 
         FIG. 5  shows a diagram representing a configuration of a condenser according to a conventional example. 
         FIG. 6  shows a diagram representing a configuration of a condenser according to a conventional example. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereunder, embodiments of the condensing equipment according to the present invention will be described with reference to the accompanying drawings. 
     First Embodiment (FIG.  1 ) 
       FIG. 1  is a plan view illustrating a condensing equipment according to the first embodiment of the present invention. As shown in  FIG. 1 , the condensing equipment according to the present embodiment is provided with circulation water pipes  27  to  34  that guide cooling water “w” to three condensers  1 ,  2  and  3 . That is, cooling tubes  4 ,  5  and  6  are disposed within shells  1   a ,  2   a  and  3   a  of the condensers  1 ,  2  and  3 , respectively, and cooling water “w” is supplied from a cooling water supply line into the cooling tubes  4 ,  5  and  6 . Steam that is guided to the condensers  1 ,  2  and  3  passes the outside of the cooling tubes  4 ,  5  and  6  disposed within the shells  1   a ,  2   a  and  3   a . At that time, the steam is condensed through heat exchanging operation with the cooling water “w” flowing inside the cooling tubes  4 ,  5  and  6 , respectively, so that the steam is converted into condensate and collected in hot wells  16 ,  17  and  18  provided below the condensers  1 ,  2  and  3 . 
     The condensate collected in the hot wells  16 ,  17  and  18  is discharged to a circulation pipe by condensate pumps, not shown, installed in the vicinity of the condensers  1 ,  2  and  3 , and the condensate is pressurized and guided to a nuclear reactor. The cooling water “w” flowing through the inside of the cooling tubes  4 ,  5  and  6  is introduced in series to the plurality of condensers  1 ,  2  and  3  using a serial piping configuration. 
     In  FIG. 1 , the configuration of the shells  1   a ,  2   a  and  3   a  of the condensers  1 ,  2  and  3  is shown as a plan view. As shown in  FIG. 1 , in the case of a multiple pressure condenser provided with three shells, the sizes increase gradually along the steam supply direction, with the sizes being set to condenser  1 &lt;condenser  2 &lt;condenser  3 . The configuration is such that center lines O 1 , O 2  and O 3  of the respective condensers  1 ,  2  and  3  are out of alignment in the axial direction of the shells. More specifically, the condensing equipment comprises a plurality of condensers with shells of different lengths that are arranged in parallel, and these condensers  1 ,  2  and  3  are serially connected by circulation water pipes  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33  and  34 . The center positions in the shell length direction of the condensers  1 ,  2  and  3  differ in the length direction in question, and the lengths of an inlet side circulation water pipe and an outlet side circulation pipe of neighboring condensers among the condensers  1 ,  2  and  3  are made coincident with each other. 
     As a result, the cooling water “w” is first guided to the condenser  1  by the circulation water pipe  27  on the upstream side, and after the temperature of the cooling water “w” flowing inside the cooling tubes  4  is raised by the heat exchange with the steam that passes the outside of the cooling tubes  4 , the cooling water “w” is discharged from the condenser  1 , passes through the circulation water pipes  28 ,  29  and  30  and is then guided to the condenser  2  at the next stage. The cooling water “w” that is guided to the condenser  2  flows through the inside of the cooling tubes  5 , and after the temperature of the cooling water “w” is raised by the heat exchange with the steam that passes the outside of the cooling tubes  5 , the cooling water “w” is discharged from the condenser  2 , passes through the circulation water pipes  31 ,  32  and  33  and is then guided to the condenser  3 . The cooling water “w” that is guided to the condenser  3  flows through the inside of the cooling tubes  6 , and after the temperature of the cooling water “w” is raised by the heat exchange with the steam that passes the outside of the cooling tubes  6 , the cooling water “w” is discharged from the condenser  3 , passes through the circulation water pipe  34  and is then discharged. 
     Further, the steam guided to the condensers  1 ,  2  and  3  is condensed into condensate through the heat exchange with the cooling water “w” flowing inside the cooling tubes  4 ,  5  and  6  when the steam passes the outside of the cooling tubes  4 ,  5  and  6 . The condensate is collected in hot wells below the condensers. The condensate collected in the hot wells below the condensers is fed from the hot well of the condenser on the low pressure side to the hot well of the condenser on the high pressure side in sequence from the condenser  1  to the condenser  2  to the condenser  3 , and is finally discharged by the operation of the condensate pump  22  provided in the vicinity of the condenser  3 . 
     Thus, according to the present embodiment, the condensers  1 ,  2  and  3  are not arranged on the same center line, but are arranged so that the positions of the cooling water outlet of the condenser  1  and the cooling water inlet of the condenser  2  align with each other. Further, the condensers  1 ,  2  and  3  are arranged so that the positions of the cooling water outlet of the condenser  2  and the cooling water inlet of the condenser  3  also align with each other. That is, the configuration, in which components (lines)  11  (l 1 ) and  12 , and  13  and  14  are made coincident with each other, is adopted. 
     As a result, when the circulation water pipe  30  of the condenser  2  is made the shortest length, the circulation water pipe  28  of the condenser  1  can likewise be made the shortest length. Similarly, when the circulation water pipe  33  is made the shortest length, the circulation water pipe  31  can likewise be made the shortest length. 
     According to the present embodiment, a piping loss can be reduced by the amount by which the circulation water pipe  28  and the circulation water pipe  31  are shortened. 
     Second Embodiment (FIG.  2 ) 
     The second embodiment of the present invention will be described hereunder with reference to  FIG. 2 . 
       FIG. 2  is a plan view illustrating an example showing configuration of condensers relating to claim  2  of the present invention. The components thereof are described hereunder. 
     In  FIG. 2 , reference numerals  27  to  34  denote circulation water pipes for guiding cooling water to the condensers  1 ,  2  and  3 . More specifically, the cooling water is first guided to the condenser  1  by the circulation water pipe  27 , and after the temperature of the cooling water flowing inside the cooling tubes  4  is raised by the heat exchange with the steam passing the outside of the cooling tubes  4 , the cooling water is discharged from the condenser  1 , passes through the circulation water pipes  28 ,  29  and  30  and is then guided to the condenser  2 . The cooling water “w” that is guided to the condenser  2  flows through the inside of the cooling tubes  5 , and after the temperature of the cooling water “w” is raised by the heat exchange with the steam passing the outside of the cooling tubes  5 , the cooling water “w” is discharged from the condenser  2 , passes through the circulation water pipes  31 ,  32  and  33  and is then guided to the condenser  3 . The cooling water that is guided to the condenser  3  flows through the inside of the cooling tubes  6 , and after the temperature of the cooling water is raised by the heat exchange with the steam passing the outside of the cooling tubes  6 , the cooling water is discharged from the condenser  3 , passes through the circulation water pipe  34  and is then discharged. 
     In  FIG. 2 , the condensers are not arranged on the same center line, but are arranged so that the positions of the cooling water outlet of the condenser  1  and the cooling water inlet of the condenser  2  align with each other. Further, the condensers are arranged so that the positions of the cooling water outlet of the condenser  2  and the cooling water inlet of the condenser  3  align with each other. That is, a configuration in which components (lines)  11  and  12 ,  13  and  14  are made coincident with each other, respectively. 
     In  FIG. 2 , a condensate pump  22  that discharges condensate from the hot well of the condenser  3  is disposed in the vicinity of the condenser  3  by utilizing a large space, which is created on the opposite side by adopting the alignment of the positions of the cooling water outlet of the condenser  2  and the cooling water inlet of the condenser  3 . 
     Consequently, since the positional relationship between the cooling water inlet of the condenser  2  and the cooling water outlet of the condenser  3  is out of alignment to a large degree, a space is created that allows the condensate pump  22  to be disposed in the vicinity of the condenser  3 . Therefore, a pipe connecting the condenser  3  and the condensate pump  22  can be shortened. That is, the piping loss can be decreased. 
     Third Embodiment (FIG.  3 ) 
     The third embodiment of the present invention will be described hereunder with reference to  FIG. 3 . 
       FIG. 3  is a plan view illustrating an example of a configuration of condensers relating to claim  3  of the present invention. Constructional elements or components thereof are described hereunder. In  FIG. 3 , reference numerals  27  to  34  denote circulation water pipes which guide the cooling water “w” to the respective condensers  1 ,  2  and  3 . More specifically, the cooling water “w” is first guided to the condenser  1  by the circulation water pipe  27 , and after the temperature of the cooling water “w” flowing inside the cooling tubes  4  is raised by the heat exchange with the steam passing the outside of the cooling tubes  4 , the cooling water “w” is discharged from the condenser  1 , passes through the circulation water pipes  28 ,  29  and  30  and is then guided to the condenser  2 . The cooling water “w” that is guided to the condenser  2  flows through the inside of the cooling tubes  5 , and after the temperature of the cooling water “w” is raised by the heat exchange with the steam passing the outside of the cooling tubes  5 , the cooling water “w” is discharged from the condenser  2 , passes through the circulation water pipes  31 ,  32  and  33  and is then guided to the condenser  3 . The cooling water that is guided to the condenser  3  flows through the inside of the cooling tubes  6 , and after the temperature of the cooling water is raised by the heat exchange with the steam passing the outside of the cooling tubes  6 , the cooling water is discharged from the condenser  3 , passes through the circulation water pipe  34  and is then discharged. 
     According to the present embodiment, as shown in  FIG. 3 , the condensers are not arranged on the same center line, but are arranged so that the positions of the cooling water outlet of the condenser  1  and the cooling water inlet of the condenser  2  align with each other. Further, the condensers are arranged so that the positions of the cooling water outlet of the condenser  2  and the cooling water inlet of the condenser  3  also align with each other. That is, a configuration in which the components (lines)  11  and  12 ,  13  and  14  are made coincident with each other, respectively. 
     Accordingly, as shown in  FIG. 3 , with respect to the drainage recovery pipes connected to the condenser from various heat exchange apparatus such as a feed water heater and a moisture separator heater, not only the drainage recovery pipe is connected to the condensers  1  and  3 , but also the drainage recovery pipe is connected to the condenser  2  disposed in the center and to the inner side of the condenser  3 . 
     That is, since the relative positions of the cooling water inlet of the condenser  1  and the cooling water outlet of the condenser  2  are out of alignment to a large degree, the space for connecting the drainage recovery pipe  39  to the condenser  2  can be created. Furthermore, since the relative positions of the cooling water inlet of the condenser  2  and the cooling water outlet of the condenser  3  are out of alignment to a large degree, the space for connecting the drainage recovery pipe  40  is created inside the condenser  3 . 
     According to the present embodiment, the drainage recovery pipe can be connected not only to the condensers  1  and  3  but also to the condenser  2  disposed in the center or to the inside of the condenser  3 . Accordingly, since the drainage recovery pipe are connected equally for each of the condensers, the present embodiment can solve the problem of arrangement of many drainage recovery pipe connections to the condensers  1  and  3 , complex arrangement of the drainage recovery piping is complex, insufficient space for connecting drainage recovery pipes to the condensers  1  and  3 , and increasing in sizes of the condensers  1  and  3 , thus being advantageous.