RANKINE CYCLE WITH MULTIPLE CONFIGURATION OF VORTEX

Abstract

A method and system for improving the efficiency of a Rankine cycle. The system comprises an accumulator that stores a working fluid, a feed pump that pumps the working fluid from the accumulator into a boiler for heating the working fluid to form a dry saturated vapor. The system includes a turbine that expands the dry saturated vapor for generating power and condensing the dry saturated vapor into a volume of wet vapor, at least one vortex tube separating the wet vapor into a higher temperature component (TH) at hot side and a lower temperature component (TC) at cold side. The system further includes at least one heat exchanger for exchanging heat from the higher to lower temperature components. The vortex tube is adaptable to function in multiple configurations to increase the change in higher and lower temperature components by reducing the quantitative value of the lower temperature component.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the provisional application No.: 61/147,421 filed on Jan. 26, 2009.

FEDERALLY SPONSORED RESEARCH

Not Applicable

SEQUENCE LISTING OR PROGRAM

Not Applicable

STATEMENT REGARDING COPYRIGHTED MATERIAL

Portions of the disclosure of this patent document contain material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office file or records, but otherwise reserves all copyright rights whatsoever.

BACKGROUND

The present invention relates in general to thermodynamic cycles, and more particularly, to a method and system for improving the efficiency of the Rankine cycle.

The Rankine cycle, which is a standard thermodynamic cycle, is proposed and developed today for an ever-widening variety of applications, including electric power generation and other refrigeration applications. In the Rankine cycle, the working fluid is vaporized using an available heat source and the vapor may expand across the turbine to release energy to perform work. Thereafter, the vapor is condensed using an available cooling medium and recirculated in the closed system.

There are a variety of known methods for improving the efficiency of the Rankine cycle. A method of intensifying heat in a reversed Rankine cycle and a reversed Rankine cycle apparatus for conducting the heat has been proposed in U.S. Pat. No. 4,646,524 issued to Kawashima (A reversed Rankine cycle system wherein a vortex tube is disposed between the compressor and the condenser in a reversed Rankine cycle). The superheated vapors of coolant at a high pressure discharged from the compressor are taken out while separating them by the vortex tube into higher and lower temperature components through energy separation. This method was to render most of the portion thereof into superheated vapors of coolant at a higher temperature and the remaining portions into vapors of coolant at a lower temperature, respectively. The superheated vapors of coolant separated into the higher temperature side are introduced into the circuit on the higher temperature side of the condenser and condensated therein, while the vapors of coolant separated into the lower temperature side are recycled to the system. Heat may be supplied from atmospheric air, or from the compressor, to vapors of coolant from the lower temperature side of the vortex tube; alternatively, in the case where the temperature of the coolant on the lower temperature side is high, excess heat may be recovered therefrom by a heat exchanger for heat absorption.

U.S. Pat. No. 4,841,721 issued to Patton, discloses an improved thermal efficiency power plant for converting fuel energy to shaft horsepower. The conventional combustor of a gas turbine power plant is replaced by a direct contact steam boiler, modified to produce a mixture of superheated steam and combustion gases. Combustion takes place preferably at stoichiometric conditions. The maximum thermal efficiency of the disclosed plant is achievable at much higher pressures than conventional gas turbines. Uses of multi-stage compression turbines with intercooling and regeneration is utilized along with a vapor bottoming cycle to achieve a thermal efficiency greater than 60% with a maximum drive turbine inlet temperature of 160° degrees Fahrenheit.

U.S. Pat. No. 6,230,480, issued to Tagawa, discloses a system and method for increasing the specific output of a combined cycle power plant and providing flexibility in the power plant rating, both without a commensurate increase in the plant heat rate. The present invention demonstrates that the process of upgrading thermal efficiencies of combined cycles can often be accomplished through the strategic use of additional fuel and/or heat input. In particular, gas turbines that exhaust into HRSGs can be supplementally fired to obtain much higher steam turbine outputs and greater overall plant ratings, but without a penalty on efficiency. This system and method by in large defines a high efficiency combined cycle power plant that is predominantly a Rankine (bottoming) cycle. Exemplary embodiments of the present invention include a load driven by a topping cycle engine (TCE), powered by a topping cycle fluid (TCF) which exhausts into a heat recovery device (HRD). The HRD is fired with a supplementary fuel, or provided an additional heat source, to produce more energetic and/or larger quantity of the bottoming cycle fluid (BCF) which is used to power a bottoming cycle engine, (BCE) which drives a load (potentially the same load as the topping cycle engine). Energy contained in either the TCF or BCF is used to power the TCE and BCE respectively, but these fluids, and/or their respective engine exhausts, may also be used to support a wide variety of cogeneration applications.

In some methods, reducing the super-heated vapors for the improvement of the Rankine process can be done by spraying water. Such type of arrangement is utilized only in relatively large power plants. A major problem within the conventional system and the method for improvement of Rankine cycle is low efficiency. The main reason for low efficiencies was that heat must be transferred in all four processes through gas films on heat transfer surfaces. Since gas films offer relatively high resistance to heat transfer, the mean cycle temperatures was very much lower than the theoretical temperature. The resulting low thermal efficiency together with high maintenance problems and high engine bulk led to the disuse of these engines.

In some methods, the Rankine cycle is limited by the working fluid used and small temperature change between the higher and lower temperature components. Thus, the system has to increase the turbine inlet temperature and dump the excess heat to the environment at 30° C.

It is therefore, an object of the present invention is to provide a method and a system for improving the efficiency of the Rankine cycle utilizing vortex tubes in multiple configurations. Another object of the invention is to increase the change in temperature by reducing the quantitative value of the lower temperature components utilizing vortex tubes in multiple configurations. Other objects of the present invention will become better understood with reference to appended Summary, Description and Claims.

SUMMARY

The present invention is a method and system for improving the efficiency of a Rankine cycle. The system comprises an accumulator defined to form a reservoir for storing a working fluid, a feed pump designed to pump the working fluid from the accumulator, a boiler for heating the working fluid pumped by the feed pump to form a dry saturated vapor. The system includes a turbine adapted to expand the dry saturated vapor for generating power and condensing the dry saturated vapor into a volume of wet vapor, at least one vortex tube having a hot side and a cold side for separating a wet vapor into a higher temperature component (T_H) and a lower temperature component (T_C). The system further includes at least one heat exchanger for exchanging heat from the higher temperature component and the lower temperature component. A mixer that is adapted to combine the higher temperature component and the lower temperature component. The vortex tube is adaptable to function in multiple configurations for reducing the quantitative value of the lower temperature component (T_C).

The refrigerant liquid or the working fluid is pumped from the accumulator to the at least one vortex tube. The heat exchanger warms and the higher temperature component from the hot side of the vortex will be cooled. Similarly, the mixed gas in the mixer is cooled from the cold side of the vortex tube. The resultant wet vapor flowing into the accumulator may be below 75° F. at the controlled pressure of 93 psia and may condense into liquid that is pumped by the feed pump into the hot heat exchanger and into the pump. This configuration is able to conserve much of the heat produced by the boiler and thereby increase efficiency. Since the feed pump requires energy and there is a system of heat loss to the environment, expected efficiency is in the 30% range. The system further includes an oil separator arranged proximate the turbine which deposits oil into the feed pump for the regeneration of the dry saturated vapor. An improvement to a Rankine cycle, in which a vortex tube in multiple configurations is expressed in degrees Kelvin, for example η=1-303.15° K(30° C.)/838.15° K(565° C.)=63.8%.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flow diagram of the basic construction of the present invention.

FIG. 2 is a flow chart illustrating an improvement to Rankine cycle.

FIG. 3 is a flow diagram of another embodiment of the present invention, illustrating another configuration of the vortex tube.

FIG. 4 is a flow diagram of yet another embodiment of the present invention, illustrating still another configuration of the vortex tube.

FIG. 5 is a graphical representation of the Carnot efficiency as a function of T_C/T_H wherein the temperature is constant at 90° C.

REFERENCE NUMERALS

10 . . . Diagrammatic representation of a method according to the present invention

12 . . . Accumulator

14 . . . Feed pump

16 . . . Boiler

18 . . . Turbine

20 . . . At least one vortex tube

22 . . . Hot side of the vortex

24 . . . Cold side of the vortex

26 . . . At least one heat exchanger

28 . . . Mixer

30 . . . Oil separator

40 . . . Flow chart illustrating an improvement to Rankine cycle

42 . . . Pumping working fluid from an accumulator

44 . . . Heating working fluid to form a dry saturated vapor

46 . . . Expanding the dry saturated vapor to form wet vapor

48 . . . Introducing wet vapor into at least one vortex tube and separating of wet vapor

50 . . . Transferring of a higher temperature component

52 . . . Transferring of a lower temperature component

54 . . . Condensing the components into a saturated liquid

56 . . . Repeating the steps in blocks 48, 50 and 52

60 . . . Flow diagram of another embodiment of the present invention

70 . . . Flow diagram of yet another embodiment of the present invention

80 . . . Graphical representation of the Carnot efficiency

DETAILED DESCRIPTION

Referring to the drawings, a preferred embodiment illustrates a method and a system for improving the efficiency of a Rankine cycle and generally indicated in FIGS. 1 through 4. Referring to FIG. 1, the major components that facilitate the method for improving the efficiency of a Rankine cycle are shown in a diagrammatic illustration 10. The system comprises an accumulator 12 defined to form a reservoir for storing a working fluid, a feed pump 14 designed to pump the working fluid from the accumulator 12, a boiler 16 for heating the working fluid pumped by the feed pump to form a dry saturated vapor. The system includes a turbine 18 adapted to expand the dry saturated vapor for generating power and condensing the dry saturated vapor into a volume of wet vapor, at least one vortex tube 20 having a hot side 22 and a cold side 24 for separating a wet vapor into a higher temperature component (T_H) and a lower temperature component (T_C). The system further includes at least one heat exchanger 26 for exchanging heat from the higher temperature component to the lower temperature component. A mixer 28 that is adapted to combine the higher temperature component and the lower temperature component. The vortex tube 20 is adaptable to function in multiple configurations for reducing the quantitative value of the lower temperature component (T_C). The accumulator 12 maintains a high efficient operation of the feed pump 14. The temperature of the system may be 90° C. or below.

With reference to FIG. 1, the refrigerant liquid or the working fluid is pumped from the accumulator 12 to the at least one vortex tube 20. The heat exchanger warms, and the higher temperature component from the hot side of the vortex 22 will be cooled. Similarly, the mixed gas in the mixer 28 is cooled from the cold side of the vortex tube 24. The resultant wet vapor flowing into the accumulator 12 may be below 75° F. at the controlled pressure of 93 psia and may condense into liquid that is pumped by the feed pump 14 into the hot heat exchanger and into the pump 14. This configuration is able to conserve much of the heat produced by the boiler 16 and thereby increase efficiency. Since the feed pump 14 requires energy and there is a system of heat loss to the environment, expected efficiency is in the 30% range. The system further includes an oil separator 30 arranged proximate the turbine 18 which deposits oil into the feed pump 14 for the regeneration of the dry saturated vapor.

The dry saturated vapor then turns the turbine 18, generating power and resulting in the condensation of the dry saturated vapor into the wet vapor. Due to choked flow, the pressure to the inlet of the vortex tube 20 is 233 psia and the temperature due to the reduced pressure is 137° F. The output of the vortex tube 20 is the higher temperature component (hot side) and the lower temperature component (cold side), respectively, depending on the multiple configurations of the vortex tubes 20.

FIG. 2 is a flow chart illustrating an improvement to a Rankine cycle 40. Initially, an accumulator pumps working fluid through a feed pump into a boiler at high pressure as indicated at block 42. The boiler heats the working fluid at a constant pressure to convert the working fluid into a dry saturated vapor as indicated at block 44. The boiler is heated to a temperature of 180° F. and results in a pressure of 400.28 psia. The turbine expands the dry saturated vapor for generating power and results in the condensation of the dry saturated vapor into wet vapor as indicated at block 46. The wet vapor is introduced into at least one vortex tube having a hot side and a cold side, then the wet vapor is separated into a higher temperature component at the hot side and a lower temperature component at the cold side by the vortex tube as indicated at block 48. Then, the higher temperature component is introduced to a heat exchanger, wherein a specific volume of the higher temperature component is transferred to the boiler and another specific volume of the higher temperature component in transferred to a mixer as indicated at block 50. The lower temperature component is introduced to another heat exchanger, wherein a specific volume of the lower temperature component is transferred to an accumulator and another specific volume of the lower temperature component is transferred to the mixer as indicated at block 52. The higher temperature component is condensed into a saturated liquid and the saturated liquid is collected in the accumulator 12 as indicated at block 54. The above steps indicated in the blocks 48, 50, and 52 are repeated for increasing the change in higher and lower temperature components (T_H-T_C) by reducing the quantitative value of the lower temperature component (T_C). An improvement to a Rankine cycle in which a vortex tube in multiple configurations is expressed in degrees Kelvin, for example η=1-303.15° K(30° C.)/838.15° K(565° C.)=63.8%.

FIG. 3 is a flow diagram of another embodiment of the present invention, illustrating another multiple configuration of the vortex tube as indicated at 60. The accumulator 12 is defined to form a reservoir for storing a working fluid. The stored working fluid is pumped through the feed pump 14 into the boiler 16. In the boiler 16, the working fluid is heated to form a dry saturated vapor. The turbine 18 included in the system expands the dry saturated vapor for generating power and condensing the dry saturated vapor into a volume of wet vapor. A vortex tube 20 is designed to separate the wet vapor into the higher temperature component and the lower temperature component. Then, a heat exchanger 26 exchanges the heat from the higher temperature to the lower temperature components. Thereafter, the above steps will continue until the change of the higher and lower temperature components is increased to achieve a reduction of the qualitative value of the lower temperature component T_C that result in higher efficiency of the Rankine cycle.

FIG. 4 is a flow diagram of yet another embodiment of the present invention, illustrating another multiple configuration of the vortex tube as indicated at 70. Additionally, the system includes a cold heat exchanger 32 with the multiple configuration of the vortex tube 20.

FIG. 5 is a graphical representation of the Carnot efficiency as a function of T_C/T_H wherein the temperature is constant at 90° C. as indicated at 80. The improved Rankine cycle for a turbine inlet temperature at 90° C. and a condenser temperature at 30° C. has a Carnot efficiency of 17.3%. If the cold side temperature can be lowered to 0° C., then the Carnot efficiency is raised to 25.5%. The difference is that the improved Rankine cycle can run off multiple heat sources and can store heat in a tank of water that allows the cycle to run 24 hours a day.

All features disclosed in this specification, including any accompanying claims, abstract, and drawings, may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

Any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. §112, paragraph 6. In particular, the use of “step of” in the claims herein is not intended to invoke the provisions of 35 U.S.C. §112, paragraph 6.

Although preferred embodiments of the present invention have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

Claims

1. A method for improving the efficiency of a Rankine cycle, the method comprising the steps of:

(a) pumping a working fluid from an accumulator through a feed pump into a boiler at high pressure;

(b) heating the working fluid in the boiler at a constant pressure to convert the working fluid into a dry saturated vapor;

(c) expanding the dry saturated vapor in a turbine for generating power and condensing the dry saturated vapor into a volume of wet vapor;

(d) introducing the wet vapor into at least one vortex tube having a hot side and a cold side for separating the wet vapor into a higher temperature component (TH) and a lower temperature component (TC);

(e) introducing the higher temperature component through the hot side to a heat exchanger, wherein a specific volume of the higher temperature component is transferred to the boiler and another specific volume of the higher temperature component is transferred to a mixer; and introducing the lower temperature component through the cold side to another heat exchanger, wherein a specific volume of the lower temperature component is transferred to an accumulator and another specific volume of the lower temperature component is transferred to the mixer;

(f) condensing the higher temperature component into a saturated liquid and collecting the saturated liquid in the accumulator; and

(g) repeating steps (d) through (f) for increasing the change in higher and lower temperature components (TH-TC) by reducing the quantitative value of the lower temperature component (TC).

2. The method of claim 1, wherein the working fluid is a liquid refrigerant.

3. The method of claim 1, wherein the boiler is heated to a temperature of 180° F. and in a pressure of 400.28 psia.

4. A system for improving the efficiency of a Rankine cycle utilizing at least one vortex tube in multiple configurations, the system comprising:

an accumulator defined to form a reservoir for storing a working fluid;

a feed pump designed to pump the working fluid from the accumulator;

a boiler for heating the working fluid pumped by the feed pump to form a dry saturated vapor;

a turbine adapted to expand the dry saturated vapor for generating power and condensing the dry saturated vapor into a volume of wet vapor;

at least one vortex tube having a hot side and a cold side for separating the wet vapor into a higher temperature component (TH) and a lower temperature component (TC);

at least one heat exchanger for exchanging heat from the higher temperature component to the lower temperature component; and

a mixer adapted to combine the higher temperature component and the lower temperature component;

whereby the vortex tube is adaptable to function in multiple configurations for reducing the quantitative value of the lower temperature component (TC).

5. The system of claim 4, wherein the working fluid is a liquid refrigerant.

6. The system of claim 4, wherein the boiler is heated to a temperature of 180° F. and in a pressure of 400.28 psia.

7. The system of claim 4, wherein the system further includes an oil separator arranged proximate the turbine which deposits oil into the feed pump for the regeneration of the dry saturated vapor.