Patent Publication Number: US-4255934-A

Title: Closed loop power system

Description:
SUMMARY OF THE INVENTION 
     This invention relates to a power system using a refrigerant fluid, such as Freon, or another suitable working fluid, operating in a closed loop which includes heat exchangers and a fluid motor. 
     Preferably, the present system is used in conjunction with a conventional steam power plant in which waste hot water is produced by one or more steam turbines and cooling water is provided by a cooling tower. Heat exchangers in the present closed loop power system are operated by these sources of hot water and cooling water in the steam power plant. 
     The present system has an upper heat exchanger for receiving the working fluid from the outlet of the fluid motor and for cooling the working fluid down to the temperature which is still well above the ambient temperature and at a pressure well above atmospheric pressure. One or more lower heat exchangers are connected to receive the pressurized working fluid in a liquid state from the upper heat exchanger through respective check valves. Each lower heat exchanger, after receiving the working fluid, first is cooled by the cooling water and then is heated by the hot water to establish a pressure in the respective lower heat exchanger substantially above the pressure in the upper heat exchanger. The heated, pressurized working fluid is discharged from the lower heat exchangers, one at a time, into the fluid motor, and the working fluid is recovered from the motor outlet and is passed back into the upper heat exchanger, completing the system loop. Preferably, the cooling, heating and discharge phases of operation of the lower heat exchangers are staggered as to provide a continuous pressurized liquid input to the fluid motor. For example, while one lower heat exchanger is being cooled, a second lower heat exchanger may be heated, and a third lower heat exchanger may be discharging the heated, pressurized working fluid into the fluid motor. 
     A principal object of this invention is to provide a novel and improved closed loop power system. 
     Another object of this invention is to provide such a power system which may be advantageously associated with a conventional steam power plant to make use of hot water and cooling water which would otherwise be wasted there. 
     Another object of this invention is to provide a novel closed loop power system containing one or more heat exchangers in which pressurized working fluid is first cooled and then heated to a substantially higher pressure while remaining in a liquid state, and then is discharged in a liquid state into a fluid motor. 
     Further objects and advantages of this invention will be apparent from the following detailed description of a presently-preferred embodiment which is shown schematically in the single Figure of the accompanying drawing. 
    
    
     DESCRIPTION OF THE DRAWING 
     The single FIGURE of the drawing shows schematically the present closed loop power system connected to the cooling tower and a steam turbine in a conventional steam power plant. 
     Before explaining the disclosed embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawing, the present system comprises first heat exchanger with a water-cooled upper tank 10 for holding Freon or other suitable refrigerant fluid in a liquid state at a temperature and pressure substantially above the ambient temperature and pressure at the site. The upper tank has a hollow outer jacket with a cold water inlet 11 and a water outlet 12. Inside this water jacket the tank defines a refrigerant container with an inlet 13 for the refrigerant fluid and a bottom outlet 14 for the refrigerant fluid. 
     Three tanks 15, 15a and 15b are positioned below the upper tank 10 so that they can receive the refrigerant fluid by gravity flow from the outlet 14 in the bottom of the upper tank. Each of the lower tanks 15, 15a and 15b has a hollow water jacket surrounding an inner container. The inner container holds the refrigerant fluid, and cooling water and hot water are circulated through the outer jacket at different times during the operating cycle of the system, as explained hereinafter. 
     The upper tank 10 acts as a heat exchanger for cooling the refrigerant fluid with water, and each of the lower tanks 15, 15a and 15b acts as a heat exchanger for cooling and heating the refrigerant fluid with water at different times during the operating cycle. 
     Referring to the lower tank 15, its outer jacket has a water inlet 16 near the top and a water outlet 17 near the bottom, and its inner container has a refrigerant inlet 18 in the top and a refrigerant outlet 19 in the bottom. 
     Each of the other lower tanks 15a and 15b has similar water and refrigerant inlets and outlets, which are identified by the same reference numerals as those for the tank 15 but with a respective &#34;a&#34; or &#34;b&#34; suffix added to distinguish them. 
     An outlet pipe 20 extends down from the refrigerant outlet 14 in the upper tank 10 to three branch pipes 21, 21a and 21b, which lead down to the refrigerant inlets 18, 18a and 18b of the lower tanks 15, 15a and 15b, respectively. A one-way check valve 22 in branch pipe 21 permits the refrigerant liquid to flow by gravity down into the lower tank 15 but prevents reverse flow from the lower tank 15 back up into the upper tank 10. Similar check valves 22a and 22b are located in the respective branch pipes 21a and 21b leading to the lower tanks 15a and 15b, respectively. 
     The refrigerant outlet 19 at the bottom of tank 15 is connected to an outlet pipe 23 in which a shutoff valve 24 is located. Similarly, the refrigerant outlet 19a at the bottom of tank 15a is connected to an outlet pipe 23a in which a shutoff valve 24a is located, and the refrigerant outlet 19b in the bottom of tank 15b is connected to an outlet pipe 23b in which a shutoff valve 24b is located. At the outlet side of these valves the respective pipes 23, 23a and 23b are all connected to a pipe 25 which leads to the inlet 26 of a vane motor 27. The outlet 28 of the vane motor is connected to a return pipe 29 which extends up past a gate valve 30 to the refrigerant inlet 13 of the upper tank 10. 
     This system is adapted for use with a conventional power generating plant having one or more steam turbines 31 and a cooling tower 32, both of known design and both shown schematically as blocks in the drawing. Waste steam from the turbine 31 is a source of hot water which may be used to heat the refrigerant liquid in each of the lower tanks 15, 15a and 15b at various times during the cycle of operation of the present system, as described hereinafter. The cooling tower 32 is a source of cool water which may be used to cool the refrigerant liquid in each of the lower tanks 15, 15a and 15b at other times during the operating cycle of this system. 
     Alternatively, the cooling water may be provided by a well or other source. 
     The waste steam outlet of the steam turbine 31 is connected to a pipe 33, which has separate connections through valves 34, 34a and 34b, respectively, to the respective inlets 16, 16a and 16b of the water jackets of the lower tanks 15, 15a and 15b. Each of these valves has two separate inlets and a single outlet. The first inlet of each valve 34, 34a and 34b is connected to the waste steam outlet of the steam turbine 31. The outlet of each valve is connected to the water inlet 16, 16a and 16b of the respective tank 15, 15a or 15b. The cooling tower 32 has a cool water outlet which is connected to a pipe 35 leading to the second inlet of each valve 34, 34a and 34b. In one practical embodiment, the water coming from the cooling tower 32 has a temperature of about 75° F. and the hot water coming from the waste steam outlet of the turbine 31 is at a temperature of about 200° F. 
     The water supplied to the water jacket of the upper tank 10 at the inlet 11 is from any convenient source of cold water. 
     The system is filled with enough working fluid, such as Freon or other suitable refrigerant fluid to keep a suitable liquid level of the working fluid in the upper tank 10 while two of the three lower tanks 15, 15a and 15b are filled and the other lower tank is discharging the working fluid through the vane motor 27. 
     In the operation of this system, for purposes of discussion it will be assumed that the lower tanks 15, 15a and 15b are operated in that sequence. 
     First, the liquid refrigerant working fluid at a temperature of about 190° F. and a pressure of about 180 psi in the upper tank 10 is supplied by gravity flow down into tank 15. After tank 15 is filled, water at about 75° F. is supplied from the cooling tower 32 through valve 34 to the water jacket of tank 15 to cool the liquid refrigerant inside this tank to about 80° F. 
     Following this cooling step, valve 34 is actuated to disconnect the cooling tower 32 from the water inlet 16 of tank 15 and to connect the waste steam outlet of the steam turbine 31 to water inlet 16. Consequently, hot water at about 200° F. now is circulated through the water jacket of tank 15 until the liquid refrigerant in this tank is heated to a temperature of about 175° F. and reaches a pressure of about 300 psi. The check valve 22 prevents any return of the refrigerant liquid from tank 15 up into tank 10 at this time. 
     Next, valve 24 is opened to pass the heated, pressurized liquid refrigerant from tank 15 to the vane motor inlet 26. At this time, the pressurized refrigerant is still in a liquid state. The pressurized refrigerant drives the vane motor 27 (which is connected to an electric generator or other utilization device, not shown) and it passes through the vane motor outlet 28 to the return line 29, where some of all of the refrigerant expand to a gaseous state. The spent refrigerant goes back into the upper tank 10 through the latter&#39;s inlet 13. Any refrigerant that may be in a vapor state will be condensed in the tank 10 by the latter&#39;s water-cooled outer jacket. 
     The inlet valves 34, 34a and 34b to the respective lower tanks 15, 15a and 15b and their outlet valves 24, 24a and 24b are operated in a timed sequence such that while liquid refrigerant is being cooled in one of these lower tanks, the refrigerant is being heated in a second lower tank, and heated pressurized refrigerant is being discharged from the third lower tank into the vane motor 27. With this sequential operation of the inlet valves and the outlet valves, which may be done either manually under timed or other automatic control, the vane motor 27 is driven continuously. 
     To completely avoid or minimize fluctuations in the power output of the vane motor 27, more lower tanks than the three shown in the drawing may be provided, if desired. 
     Alternatively, just one or two lower tanks may be used in the system if intermittent or fluctuating operation of the vane motor 27 is acceptable. 
     It is to be understood that the vane motor 27 may be replaced by another type of hydraulic motor or by a hydraulic turbine, if desired. 
     Also, the sources of the cooling fluid and the heating fluid for the heat exchangers 10, 15, 15a and 15b may be different from the cooling tower 32 and the steam turbine or turbines 31 shown schematically in the drawing.