Strain Augmented Thermodynamic Power Cycle

Abstract

Strain augmented power cycle is disclosed. This power cycle is a thermodynamic power cycle that contains a strain energy device to increase the thermodynamic efficiency above what is possible from a conventional Rankine power cycle. Strain augmented power cycle comprises an assembly of components including a working fluid, a pump, an evaporator, a strain energy device, an expander and a condenser.

Claims

1. A system for generating power from heat, the system comprising: A. a working fluid; B. a working fluid condenser in receiving communication with said working fluid, comprising a working fluid inlet, a working fluid outlet and a means for transferring heat from said working fluid to a low temperature environment; C. a working fluid pump in working fluid receiving communication with said working fluid outlet of said working fluid condenser; D. a source of heat energy; E. a working fluid heat exchanger (i) in working fluid receiving communication with said working fluid pump and (ii) in heat energy receiving communication with said source of heat energy; F. one or more strain energy device(s) with each said strain energy device comprising a working fluid inlet valve, a working fluid outlet valve, one or more elastomeric wall (s) that enclose an expandable working fluid cavity (i) each said working fluid inlet valve of one or more said strain energy device(s) is in working fluid receiving communication with said working fluid heat exchanger; G. a working fluid expander comprising (i) a working fluid inlet in working fluid receiving communication with at least one of said outlet valve(s) of one or more said strain energy device(s), (ii) a rotating mechanical power output shaft and (iii) a working fluid outlet in working fluid sending communication with working fluid inlet of said working fluid condenser; wherein said system for generating power from heat is configured to: a. cool said working fluid from a saturated vapor working fluid to a saturated liquid working fluid in said working fluid condenser; b. pressurize said saturated liquid working fluid to a compressed liquid working fluid in said working fluid pump; c. heat said compressed liquid working fluid to a high temperature and pressure vapor working fluid via said working fluid heat exchanger utilizing said source of heat energy; d. charge said expandable working fluid cavity of said one or more strain energy device (s), wherein said charging causes the working fluid cavity to expand from a first position to a second position and imposes strain energy in said one or more elastomeric wall(s), of said one or more strain energy device(s) with said high temperature and pressure vapor through said working fluid inlet valve, while said working fluid outlet valve is in a closed position; e. discharge said high temperature and pressure vapor from said expandable working fluid cavity, wherein said discharging causes the expandable working fluid cavity to contract from said second position to said first position and causes said strain energy contained in said elastomeric walls to be transferred to said high temperature and pressure vapor, through said outlet valve of said one or more strain energy device(s) into said working fluid inlet of said working fluid expander; f. expand said high temperature and pressure vapor working fluid to said saturated vapor working fluid in said expander to generate mechanical power at said rotating mechanical power output shaft; g. cool said saturated vapor working fluid to said saturated liquid working fluid in said working condenser;.

2. The system of claim 1 wherein said one or more strain energy device(s) comprised of said one or more elastomeric wall(s) that encloses an expandable cavity that is substantially cylindrically shaped.

3. The system of claim 1 wherein said one or more strain energy device(s) comprised of said one or more elastomeric wall(s) encloses an expandable cavity that is substantially spherically shaped.

4. The system of claim 1 wherein said high temperature and pressure vapor is expanded to a mixture of saturated liquid and saturated vapor in said expander.

5. The system of claim 1 wherein a liquid transfer fluid is contained within said working fluid cavity(s) wherein the high temperature and pressure vapor working fluid causes the cavity(s) of said one or more strain energy device(s) to be charged by said liquid transfer fluid.

6. The system of claim 1 wherein said rotating mechanical power output shaft is in mechanical power output delivery communication with at least one of any of an electrical generator, a prime mover, a pump, a combustion engine, a fan, a turbine or a compressor.

7. A method for generating power from heat, the method comprising : A. a working fluid means; B. a working fluid condenser means comprising a working fluid inlet means and a working fluid outlet means; C. a working fluid pump means in working fluid receiving communication with said working fluid outlet means of said working fluid condenser means; D. a source of heat energy means; E. a working fluid heat exchanger means(i) in working fluid receiving communication with said working fluid pump means and (ii) in heat energy receiving communication with said source of heat energy means; F. one or more strain energy device means with each said strain energy device means comprising a working fluid inlet valve means, a working fluid outlet valve means, one or more elastomeric wall means that encloses an expandable working fluid cavity G. means (i) each said working fluid inlet valve means of one or more said strain energy device means in working fluid receiving communication with said working fluid heat exchanger means; H. a working fluid expander means comprising (i) a working fluid inlet means in working fluid receiving communication with at least one of said outlet valve(s) means of one or more said strain energy device(s) means, (ii) a rotating mechanical power output shaft means and (iii) a working fluid outlet means in working fluid sending communication with working fluid inlet means of said working fluid condenser means; wherein said method for generating power from heat is configured to: h. cool said working fluid means from a saturated vapor working fluid means to a saturated liquid working fluid means in said working fluid condenser means; i. pressurize said saturate liquid working fluid means to a compressed liquid working fluid means in said working fluid pump means; j. heat said compressed liquid working fluid means to a high temperature and pressure vapor working fluid means via said working fluid heat exchanger means utilizing said source of heat energy means; k. charge said expandable working fluid cavity means, wherein said charging causes the working fluid cavity means to expand from a first position to a second position and imposes strain energy in said elastomeric wall means, of said one or more strain energy device(s) means with said high temperature and pressure vapor means through said one or more working fluid inlet valves means, while said working fluid exit valve means is in a closed position; l. discharge said high temperature and pressure vapor means from expandable working fluid cavity means, wherein said discharging causes the expandable working fluid cavity means to contract from said second position to said first position and causes said strain energy contained in said elastomeric wall means to be transferred to said high temperature and pressure vapor means, through said outlet valve means of said one or more strain energy device(s) means into said working fluid inlet means of said working fluid expander means; m. expand said high temperature and pressure vapor working fluid means to said saturated vapor working fluid means in said expander to generate mechanic power at said rotating mechanical power output shaft means; n. cool said saturated vapor working fluid means to said saturated liquid working fluid in said working condenser means.

8. The method of claim 7 wherein said one or more strain energy device means comprised of said elastomeric wall means encloses an expandable cavity means that is substantially cylindrically shaped.

9. The method of claim 7 wherein said one or more strain energy devices means comprised of said elastomeric wall means encloses an expandable cavity means that is substantially spherically shaped.

10. The method of claim 7 wherein said high temperature and pressure vapor means is expanded to a mixture of saturated liquid means and saturated vapor means in said expander means.

11. The method of claim 7 wherein a liquid transfer fluid means is contained within said working fluid cavity(s) means wherein the high temperature and pressure vapor working fluid means causes the cavity(s) of said one or more strain energy device(s) means to be charged by said liquid transfer fluid means.

12. The method of claim 7 wherein said rotating mechanical power output shaft means is in mechanical power output delivery communication means with at least one of any of an electrical generator means, a prime mover means, a pump means, a combustion engine means, a fan means, a turbine means or a compressor means.

Description

DRAWINGS—FIGURES

[0042] FIGS. 1A and 1B shows various aspects of a prior art Rankine cycle.

[0043] FIGS. 2A to 2C shows various aspects of a strain augmented power cycle.

[0044] FIGS. 3A and 3B shows various aspects of a control volume that surrounds the strain energy device and the evaporator of a strain augmented power cycle.

[0045] FIGS. 4A and 4B shows various aspects of a control volume that surrounds the strain energy device and expander of a strain augmented power cycle.

[0046] FIGS. 5A and 5B shows various aspects of control volumes that surrounds the condenser and the pump of a strain augmented power cycle.

TABLE-US-00003 Drawings-Reference Numerals 10 saturated liquid 12 compressed liquid 14 High temperature and 16 saturated vapor pressure vapor 20 saturation dome 21 critical point 22 saturated liquid transition 24 compressed liquid region 25 saturated fluid region 26 saturated vapor transition 28 superheated vapor region 30 Pump 35 pumping process 40 evaporator 45 constant pressure process 50 expander 55 constant entropy process 56 alternate constant entropy process 60 Condenser 65 condensation process 70 inlet valve 72 exit valve 74 Cavity 75 strain energy device 77 elastomeric walls 100 input thermal energy 120 input work 150 waste thermal energy 200 output work 310 evaporator control volume 320 expander control volume 330 condenser control volume 340 pump control volume 500 prior art Rankine cycle 600 strain augmented power cycle

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] The following provides a detailed description of the present invention with respect to a few preferred embodiments. This description provides a thorough understanding of the present invention through discussion of specific details of these preferred embodiments. To those skilled in the current art, it will be apparent that the present invention can be practiced with variations to the preferred embodiments, with or without some or all of these specific details. Well known processes, steps, and/or elements have not been described in order to focus on, and not obscure, those elements of the present invention.

Strain Augmented Power Cycle FIG. 2A, FIG. 2B and FIG. 2C

[0048] FIG. 2A shows a preferred embodiment of a strain augmented power cycle 600. At the beginning of the cycle, the working fluid starts as a saturated liquid 10. Pump 30 then pressurizes saturated liquid 10 to a high-pressure compressed liquid 12 by input work 120. After leaving pump 30, compressed liquid 12 enters evaporator 40. High temperature input thermal energy 100 enters evaporator 40 and is transfers to compressed liquid 12 to produce high temperature and pressure vapor 14 at constant pressure. Compressed liquid 12, and high temperature and pressure vapor 14 exist at the same high pressure. High pressure and temperature vapor 14 exits evaporator 40, and flows into and inflates strain energy device 75. No additional heat or energy is transferred to or from high temperature and pressure vapor 14 during inflation of strain energy device 75. Strain energy device 75 is comprised of elastomeric walls 77, inlet valve 70 and exit valve 72. FIG. 2B shows a cross section of strain energy device 75 in an uninflated condition with inlet valve 70 in an open position and exit valve 72 in closed position. High temperature and pressure vapor 14 flows through inlet valve 70 into cavity 74 of strain energy device 75. As high temperature and pressure vapor 14 flows into cavity 74 of strain energy device 75, elastomeric walls 77 stretch until strain energy device reaches an inflated condition. In the inflated condition, the energy contained within strain energy device 75 is the sum of the total enthalpy contained within cavity 74 plus the strain energy contained within elastomeric walls 77. When strain energy device 75 reaches the inflated condition, inlet valve 70 switches to a closed position and exit valve switches to an open position. FIG. 2C shows a cross section of strain energy device 75 in an inflated condition with inlet valve 70 in a closed position and exit valve 72 in an open position. High pressure and temperature working fluid 14 flows from cavity 74 of strain energy device 75 until strain energy device 75 returns to the uninflated condition. During deflation of strain energy device 75, the strain energy contained within elastomeric walls 77 transfers to high pressure and temperature working fluid 14. The total energy flow from strain energy device 75 during deflation is the sum of the strain energy in elastomeric walls 77 plus the total enthalpy of high temperature and pressure vapor 14.

[0049] Elastomeric walls 77 of uninflated strain energy device 75, as shown in FIG. 2B, are much thicker than the walls 77 of inflated strain energy device 75 as show FIG. 2C. This is because the elastomeric material is incompressible and as result, the elastomeric material does not change in volume. The volume of inflated cavity 74 is much larger than uninflated cavity 74. As a result, elastomeric walls 77 must stretch in order to enclose inflated cavity 74. This means that the stretched elastomeric walls 77 must be much thinner than the walls 77 of an uninflated strain energy device 75.

[0050] For a hollow sphere, the distance from the center to the inside surface (i.e. inside radius) of the sphere is I and the distance from the center to the outside surface (i.e. outside radius) of the sphere is O. The ratio of the O divided by I is equal to φ described below as

[00002]$\varphi =\frac{0}{I}$

where φ is the ratio of O divided by I. The volume of the hollow sphere is described below as

[00003]$V=\frac{4}{3}.Math.{\pi .Math.I}^3\left({\varphi }^3-1\right)$

where V is the volume of the hollow sphere wall. If strain energy device 75 is spherically shaped then the volume of elastomeric walls 77 can be described by the above expression for the volume of a hollow sphere.

[0051] The work required to inflate strain energy device can be described as

[00004]$\mathrm{WI}={\int }_0^V.Math.\mathrm{PdV}$

where WI is the work to inflate strain energy device 75, P is the pressure in cavity 74, V is the volume of cavity 74 and dV is the differential volume. Because inflation of strain energy device 75 is a constant pressure process, the WI can be describe as

WI=PV.

Because the inflation process occurs over a short period of time, there is no heat transfer into elastomeric walls 77. As a result, the inflation work and the strain energy are equivalent as described below

S=PV

where S is the strain energy contained within elastomeric walls 77 of strain energy device 75.

[0052] The strain energy for a thick-walled hollow elastomeric sphere can be described below as

[00005]$S=1.6875.Math.\frac{P^2.Math.V}{E}.Math.\frac{{\varphi }^3}{\left({\varphi }^3-1\right)}$

where E is the elastic modulus of the elastomeric materials in elastomeric walls 77. Combining the two expressions for S and rearranging results in an expression for φ described below as

[00006]$\varphi =\sqrt[3]{\frac{1}{\left(1-1.6875.Math.\frac{P}{E}\right)}}$

With the above equation for φ and representative values for the system pressure “P” and the elastic modulus “E” of elastomeric walls 77 a representative value of φ can be shown. As can be seen in FIG. 1B, once the entropy of saturated vapor is determined, and the temperature of input thermal energy 100 is known, the pressure of input thermal energy can be determined. A representative working fluid for Rankine cycle 500 and strain augmented power cycle 600 is water. A representative saturation temperature for water that is used in Rankine cycle 500 and strain augmented power cycle 600 is 39° C. This representative temperature allows the heat transfer of waste thermal energy 150 into the environment by condenser 60. At 39° C., the saturated vapor entropy for water is 8.275 kJ/kg° K. A representative temperature for high temperature vapor 14 is 400° C. The corresponding pressure for a superheated water vapor at 400° C. is P=0.178 MPa. A possible material for elastomeric walls 77 is an unfilled silicone rubber with an elastic modulus of E=1.2 MPa. Substituting the values for P and E into the expression for φ results in φ=1.10. This means that the thickness of elastomeric walls 77 is 10% of the inside radius of strain energy device 75 if strain energy device 75 was spherically shaped. In other words, strain energy device 75 requires elastomeric walls 77 that are at least 10% of “I” in thickness in order to produce optimum strain energy.

[0053] As strain energy device 75 deflates, high pressure and temperature vapor 14 flows into expander 50. The total energy flow into expander 50 is the sum of the strain energy plus the total enthalpy of high temperature and pressure vapor 14. The total energy that leaves the expander 50 is output work 200 plus the total enthalpy of saturated vapor working fluid 16. Saturated vapor 16 exits expander 50 and flows into condenser 60. Condenser 60 converts saturated vapor 16 to saturated liquid 10. The difference in total enthalpy between saturated vapor 16 and saturated liquid 10 is the energy rejected to the environment as waste thermal energy 150. Saturated vapor 16 working fluid flows from condenser 60 and into pump 30 to repeat the cycle.

[0054] Inflation and deflation of strain energy device 75 occurs quickly enough so that no heat transferred occurs into or out of elastomeric walls 77. In addition, the volume of elastomeric walls 77 does not change during inflation and deflation. No additional heat is added to high temperature and pressure vapor 14 during inflation of strain energy device 75, after leaving evaporator 40. The definition of a constant entropy process is one where there is no energy transferred into or out of a system and the volume of the system does not change. This means inflation and deflation of strain energy device 75 is a constant entropy processes.

Energy and Work Flow Control Volumes FIG. 3A through FIG. 5B

[0055] FIG. 3A shows evaporator control volume 310 surrounding evaporator 40 and strain energy device 75 in the uninflated condition. A control volume is an imaginary boundary that contains energy, working fluid and the relevant system components. In addition, energy and work can flow across the boundary. At an initial time, fluid flow, or energy is not crossing evaporator control volume 310. High temperature and pressure vapor 14 is blocked from flowing into strain energy device 75 by closed inlet valve 70. At the initial time, the strain energy in elastomeric walls 77 and the thermal energy in cavity 74 are set at zero.

[0056] FIG. 3B shows evaporator control volume 310, at a later time, when inlet valve 70 is in an open position and exit valve 72 is in a closed position. High temperature and pressure vapor 14 flows from evaporator 40 and inflates strain energy device 75. Strain augmented power cycle 600 input thermal energy 100 is the input energy that flows through evaporator 40 as described below

Q40=Q75−H12

where Q40 is input thermal energy 100 into evaporator 40, Q75 is the energy contained in strain energy device 75 and H12 is the total enthalpy of compressed liquid 12.

[0057] FIG. 4A shows expander control volume 320 that surrounds fully inflated strain energy device 75 and expander 50. There is no energy or work flowing into or out of control volume 320. Valves 70 and 72 are in their closed positions so that high temperature and pressure vapor 14 is retained in cavity 74. The total energy in inflated strain energy device 75 described below is

Q75=H14+S

where H14 is the total enthalpy of high temperature and pressure vapor 14 contained in cavity 74, and S is the strain energy in elastomeric walls 77.

[0058] FIG. 4B shows expander control volume 320, at a later time, when exit valve 72 is in the open position and high temperature and pressure vapor 14 flows from strain energy device 75 into expander 50. The energy that exits control volume 320, during deflation of strain energy device 75, includes output work 200 and saturated vapor 16. The total output work 200 produced by expander 50 after strain energy device is fully deflated is describe below as

WT=H14−H16+S

where WT is the output work 200 from expander 50 and H16 is the enthalpy of saturated vapor 16. The strain energy is substantially reversible and recovered by expander 50 during deflation of strain energy device 75.

[0059] FIG. 5A shows condenser control volume 330 that surrounds condenser 60 during flow of saturated working fluid 16 into condenser 60, and flow of saturated liquid 10 and waste heat 150 from condenser. Waste heat 150 is the thermal energy that flows from condenser 60 described below as

Q60=H16−H10

where Q60 is the waste thermal energy 150 and H10 is the enthalpy of saturated liquid 10.

[0060] FIG. 5B shows pump control volume 340 that surround pump 30. Saturated liquid 10 and input work 120 flows into pump 30 and compressed liquid 12 flows out of pump 30.

Input work 120 is the work required to pressurize saturated liquid 10 to compressed liquid 12 shown below as

WP=H12−H10

where WP is input work 120.

[0061] The efficiency of stain augmented power cycle 600 can be describe by the ratio of the total work produced divided by the input energy. The total work produced is the output work 200 minus the input work 120. The input energy is input thermal energy 100. Using the expressions for WT, WP and Q40 the efficiency is described as

[00007]$\eta .Math..Math.s=\frac{\mathrm{WT}-\mathrm{WP}}{Q.Math..Math.40}$

where ηs is the efficiency of strain augmented power cycle 600. Substituting the expressions for WT, WP, and Q40 in the expression for ηs results in

[00008]$\eta .Math..Math.s=\frac{\left(H.Math..Math.14-H.Math..Math.16\right)-\left(H.Math..Math.12-H.Math..Math.10\right)+S}{H.Math..Math.14-H.Math..Math.12+S}$

[0062] Using the expressions that describe Q60 and Q40, the waste thermal energy ratio for strain augmented power cycle is described below as

[00009]$\omega .Math..Math.s=\frac{Q.Math..Math.60}{Q.Math..Math.40}$

where ωs is the ratio of waste thermal energy. Substituting the expressions for Q60 and Q40 in the following expression for ηs.

[00010]$\omega .Math..Math.s=\frac{H.Math..Math.16-H.Math..Math.10}{H.Math..Math.14-H.Math.12+S}$

[0063] In a closed power cycle including strain energy device 600 and prior art Rankine cycle 500, the sum of total work produced plus the waste thermal energy is equal to the total energy expelled from these cycles. The total energy expelled from the system is also equal to the total energy flow into the cycles. This means the sum of the efficiency and the waste thermal energy ratio is equal to one.

[0064] For strain augmented power cycle 600 that has the same high temperature and pressure vapor 14 and the same saturated vapor 16 working fluid states as that of prior art Rankine cycle 500, the temperature vs entropy diagram shown in FIG. 1B applies to both cycles. This means the same thermodynamic limitations apply to the strain augmented power cycle 600 and to prior art Rankine cycle 500.

[0065] As a result, a direct comparison can be made between the efficiencies of the two cycles. The efficiency of prior art Rankine cycle 500 can be described below as

[00011]$\eta .Math..Math.r=\frac{\left(H.Math..Math.14.Math.-H.Math..Math.16\right)-\left(H.Math..Math.12-H.Math..Math.10\right)}{H.Math..Math.14-H.Math..Math.12}$

where ηr is the efficiency of prior art Rankine cycle. The waste energy ratio of prior art Rankine cycle 500 can be described below as

[00012]$\omega .Math..Math.r=\frac{H.Math..Math.16-H.Math..Math.10}{H.Math..Math.14-H.Math..Math.12}$

where ωr is the waste heat ratio for prior art Rankine cycle.

[0066] Because the denominator includes the strain energy term, the waste energy ratio for strain augmented power cycle 600 is smaller than the waste energy ratio for prior art Rankine cycle 500. As a result, the efficiency of strain augmented power cycle 600 is greater than the efficiency of prior art Rankine cycle 500.

Advantages

[0067] From the description above, a number of advantages of some embodiments of my strain augmented power cycle become evident:

[0068] (a) With the use of a strain energy device constructed of a low elastic modulus elastomeric material, the stain augmented power cycle can be employed in systems that have lower temperature and pressure input energy heat sources. Compared to prior art

Rankine power cycles, the efficiencies of systems with strain energy devices are greater than what is possible with prior art power cycles that have the same input energy heat sources.

[0069] (b) With the use of a strain energy device constructed of an elastomeric material, the strain augmented power cycle can be employed in systems that have equivalent temperature and pressure inputs of prior art Rankine power cycles, with efficiencies that are greater than is possible with prior art power cycles.

[0070] (c) With the use of a strain energy device constructed of a compatible material, high temperature and pressure working fluids can come in direct contact with the strain energy device.

[0071] (d) The strain energy device can embody a cylindrical geometry.

[0072] (e) The strain energy device can embody a spherical geometry.

[0073] (f) For working fluid temperatures and pressures that are not compatible with the elastomeric material of the strain energy device, an intermediate fluid can be used to inflate the strain energy device, wherein the working fluid comes in direct contact with the intermediate fluid.

Conclusions, Ramifications, and Scope of Invention

[0074] Accordingly, the reader will see that the strain augmented power cycle can be used increase the thermodynamic efficiency of a power cycle. Thus, this invention can be used to recover a greater portion of the power cycle's input thermal energy and convert that energy into useful work. This increased efficiency results from the strain energy imposed in the elastomeric walls of the strain energy device. In the elastomeric walls, strain is substantially reversible and can be recovered as useful work in an expander. Furthermore, the strain augmented power cycle has the additional advantages in that: [0075] It can be employed in the low temperature and pressure heat sources of alternate energy source including but not limited to geothermal, solar thermal and biomass energy sources. [0076] It can be employed where the exhaust heat from an internal combustion engine is the input energy source. [0077] It can be employed using heat sources from the combustion of fossil fuels including but not limited to coal and natural gas. [0078] It can be employed where the energy source is nuclear fusion energy.

[0079] Although the description above contains many specificities these should not be construed as limiting the scope of the invention but merely providing illustrations of some of the presently preferred embodiments of this invention. For example, the strain energy device could be used in additional power cycles that include but not limited to: an Ericsson cycle, a Sterling cycle, a Brayton cycle, an Otto cycle, and a Diesel cycle. Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.