Method and apparatus for producing electrical power and for the simultaneous heating of fluid, utilizing a magnetohydrodynamic generator

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force or by means of a pump. The liquid is then further

METHOD AND APPARATUS FOR PRODUCING directed to the heater to be reheated. ELECTRICAL POWER AND FOR THE As it can be appreciated, this system must utilize a SIMULTANEOUS HEATING OF FLUID, source of high temperature in order to heat up the liquid UTLIZNG AMAGNETOHYDRODYNAMIC 5 metal to its boiling point to form the driving bubbles GENERATOR and, also, through the MHD-generator there is passed, at low velocity, only a single-phase medium.

This application is a continuation-in-part of applica While the prior art systems are capable of producing tion Ser. No. 78,786, filed Sept. 28, 1979, now aban electric currents by the conversion of thermal energy doned. 10 into electricity utilizing an MHD-generator, they are BRIEF DESCRIPTION OF THE PRIOR ART able to operate only at high temperature which is very costly to produce. It is, therefore, a broad object of the

The present invention relates to a method and appara present invention to provide an MHD thermal electric tus for simultaneous heating of fluid and production of power conversion system operating in relatively low electric power. More particularly, the invention is con S temperatures and a specific object to provide such a cerned with a method and apparatus for simultaneously system utilizing solar energy.

heating fluid and producing electric power by means of a magnetohydrodynamic (MHD) generator. SUMMARY OF THE INVENTION Heretofore, there have been suggested various sys According to the present invention, there is provided tems for utilizing MHD generators, for the production 20 a method for producing electrical power by means of a of electricity in general and, for the production of elec magnetohydrodynamic (MHD) generator, comprising: tricity by means of thermal electric power conversion, providing heating means for heating a mixture of in particular. In a number of older systems, fuel was liquid metal and an organic liquid to form a two-phase used to drive liquid metal through the MHD-generator liquid metal-vapor flow;

by means of plasma produced from fuel combustion, 25 directing said two-phase metal-vapor through an wherein the operating temperatures were relatively MHD-generator to generate electricity; high, e.g., above 800 C. condensing the vapor phase from said two-phase In a more recent development disclosed in the U.S. liquid metal to form liquid metal carrying organic liquid Pat. No. 3,453,462 there is described an MHD-genera droplets; and tor in which a nonconductive gas is heated, for example, 30 recycling said liquid metal and organic liquid droplets by means of a nuclear reactor, to produce gas of high to be reheated by said heating means. kinetic energy to drive liquid metal mist from a mixing The invention also provides an MHD apparatus for chamber to a MHD-generator in such proportions that producing electrical power comprising: the liquid metal coalesces into slugs of metal. The slugs of metal are separated by pockets of the nonconductive metal and anduct 35 a closed system containing a mixture of liquid organic liquid;

gas whose kinetic energy aids in the movement of the slugs through the MHD-generator to generate electric system; a heating means for heating the mixture in said closed

current. After leaving the generator, the slugs are sepa rated from the nonconductive gas. The liquid metal and a magnetohydrodynamic (MHD) generator located the gas are recirculated by means of pumps through along the flow path of a two-phase liquid metal-vapor heat exchangers to increase their respective kinetic flow formed by the heated mixture;

energies. . . . . means for condensing the two-phase flow to form a In addition to the fact that such slugs disintegrate and single phase of metal liquid containing organic liquid the metal adheres to the walls of the carrying duct, this droplets flow; and system also suffers from the drawback that in order to 45 means for propelling said single-phase flow to be circulate the separated gas, it is necessary to provide the reheated by said heating means. In accordance with a further embodiment of this circulating pump with a substantial amount of energy which, of course, greatly detracts from the efficiency of invention, it is proposed to fully utilize the available this system to the point of rendering the same uneco heat energy by providing a combined installation for nomical. 50 both, converting relatively low energy, e.g., solar en It should also be mentioned that due to the fact that ergy into electricity and for heating a fluid, for any use, through the MHD-generator there are passed slugs by means of the heat given off when the two-phase separated by pockets of gas, the generated electricity is mixture flow is condensed into a single-phase flow. in the form of a pulsating or intermittent D.C. and Such a system may have a total efficiency greater than moreover, the electrical currents which is produced is 55 50%. - discontinuous, irregular and non-predictable. Yet, in another aspect of the present invention, there The U.S. Pat. No. 3,443,129 discloses a vapor-liquid is provided apparatus for converting solar energy into cycle MHD power conversion system in which con electricity and for heating a fluid comprising: trary to the prior teachings, its stated general object is a closed system containing a mixture of an electrically to provide an MHD thermal electric power conversion conductive liquid and of a low boiling temperature system by the use of fluids at low fluid velocities. In one propelling liquid;

of the disclosed embodiments, it is suggested to drive, in solar energy absorbing means for heating said mixture a single loop system, a single substance, namely, an to form a two-phase flow;

electrically conductive liquid by heating the same at a magnetohydrodynamic (MHD) generator located one point along the loop, to form bubbles of the same 65 along the path of the two-phase flow; substance, which bubbles will drive the liquid to a con a condensing and heat-exchanging means for con denser. When condensed, the driven liquid continues to densing said two-phase flow into a single-phase mixture flow through an MHD-generator either by a gravity of the electrically conductive liquid containing droplets

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of the propelling liquid and for heating a fluid circulat the MHD-generator, thereby producing electricity. ing in said heat-exchanger; and The expansion of the vapor bubbles in the conduit is means for propelling said single-phase mixture to be almost isothermal since the heat capacity of the liquid reheated by said solar energy absorbing means. metal is manyfold higher than that of the vapor. The BRIEF DESCRIPTION OF THE DRAWINGS direct contact heat exchanger and the two-phase flow acceleration at constant temperature provides an effi

While the invention will now be described in connec cient Rankine-type thermodynamic cycle. tion with certain preferred embodiments with reference After leaving the MHD-generator, the void fraction to the following illustrative figures so that it may be is not separated, as it is usually done in other MHD more fully understood, it is stressed that the particulars O systems, but rather, it is condensed in condenser 10, into shown and described are by way of example and for droplets of organic liquid forming a mixture 20 of liquid purposes of illustrative discussion only and are pres metal and droplets of organic liquid and thus the desired ented in the cause of providing what is believed to be features of retaining throughout the cycle a homogene the most useful and readily understood description of ous mixture and the recirculation of liquid rather than a the principles and conceptual aspects of the invention. 15 gas, is kept.

In this regard no attempt is made to show structural The liquid metal carrying the droplets of the organic details of the apparatus and their elements in more detail liquid and being in direct-contact heat-exchange there than is necessary for a fundamental understanding of the with is then recycled back to the solar heater to be invention, the description taken with the drawings mak reheated. This can be achieved by means of the shown ing apparent to those skilled in the art how the several 20 MHD pump 14, which pump may use a small part of the forms of the invention may be embodied in practice. electric current produced in the MHD-generator. Be In the drawings: fore entering the heat absorber 4, the flow 20 is advanta FIG. 1 is a schematic illustration of an MHD system geously passed through a mixer or a dispenser 16 where embodying the present invention; the droplets of the organic liquid are atomized and FIG. 2 is a schematic illustration of a modification of 25 dispersed more homogeneously in the liquid metal. the system of FIG. 1; and A modification of the system of FIG. 1 is illustrated FIG. 3 is a schematic illustration of a further embodi in FIG. 2 wherein the same reference numbers are used ment of an MHD system according to the present in to identify components having the same function and vention. operation. As it can be seen, the instant system is sub DETAILED DESCRIPTION 30 stantially identical to the previously described one, except for the condenser which, in the present embodi

In FIG. 1 there is shown a closed loop or duct system ment, is a heat exchange-condenser 22 having an inlet 2 for converting heat from a relatively low-temperature pipe 24 and an outlet pipe 26, respectively supplying to heating means, e.g., solar energy, into electrical current. the heat exchanger cold fluid, e.g., water, and extract The system comprises a solar absorber 4, which may be 35 ing therefrom fluid heated by means of the heat energy of any known type as, for example, of the flat collector which is given off by the condensation of the vapor type or of the more elaborate solar energy concentrator bubbles into liquid droplets. The total efficiency of this type. The interior of the solar absorber 4 is in fluid system, simultaneously producing electricity and heat, communication with a conduit 6 leading via an MHD is about 50% even when plane or flat collectors are generator 8 to a condenser 10. The interior of the con used.

denser 10 is in fluid communication with a conduit 12 Turning now to FIG. 3, there is illustrated still a leading to the absorber 4 via a pump 14, e.g., an MHD further embodiment of the present invention. Here pump. Optionally, between the pump 14 and the ab again identical reference numbers are used to identify sorber 4, there is installed a fluid mixer or dispersing similar components. According to this embodiment, means 16, which disperser may be constituted by a set of 45 there is interposed, between the absorber 4 and the screens or by a plurality of vanes inside the conduit 12. conduits 6 and 12, a heat exchanger 28 so that the mix The operation of the apparatus is as follows: a liquid ture of liquid metal and organic liquid is heated by the metal electrically conductive liquid, e.g., Nak alloy solar energy via the heat exchanger 28 and the heat eutectic, mercury, gallium or tin and a low boiling tem absorbed in the absorber 4 is transferred to the heat perature propelling liquid, e.g., neohexane (for Nak) or 50 exchanger by means of a liquid 30 circulating between freon or water (for mercury, gallium or tin) is intro the absorber and the heat exchanger in a closed loop, duced in the system forming a mixture of liquid metal whereby said recycled liquid metal and organic liquid and organic liquid. For avoiding phase separation and droplets are indirectly reheated by the energy collected for the promoting of foaming, surfactant additives, e.g., by said solar energy absorber rather than directly as in carbon black, sulfur, selenium for Nak or magnesia for 55 the previously illustrated embodiments. mercury, could optionally also be used. Advantageously, the heat carrying liquid from the As the mixture of liquid metal and organic liquid is absorber to heat exchanger may be constituted by a heated up by means of, for example, the solar energy liquid metal, thus forming a highly effective liquid met absorber, when a plane collector or collectors are used, al-liquid metal heat exchanger. Due to the high thermal where it is expected that the mixture of liquid metal and conductivity and low vapor pressure of liquid metals, it organic liquid will heat up to about 110-120' C., or is possible to increase the temperatures commonly when a concentrating collector, for example, concen achieved in solar absorbers and, consequently, to obtain trating mirrors or a parabolic collector, is used, where it a more efficient electricity and hot liquid producing is expected that the mixture will heat up to about system.

300-400 C., the organic liquid is brought to its boiling 65 Also, the optional use of permanent magnets in the temperature and a two-phase liquid metal-vapor 18, is MHD-generator and/or in the MHD-pump is of advan produced. The thusly formed vapor bubbles expand and tage since there is no need for energy of the excitation accelerate the two-phase flow in the conduit 6 through of the necessary magnetic fields.

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While particular embodiments of the invention have 7. A magnetohydrodynamic (MHD) apparatus for been described, it will be evident to those skilled in the producing electrical power, comprising art that the present invention may be embodied in other (a) a closed duct system containing a mixture of liquid specific forms without departing from the essential metal and a low boiling temperature propelling characteristics thereof. The present embodiments are, 5 liquid;

therefore, to be considered in all respects as illustrative (b) heating means for heating the mixture in said and not restrictive, the scope of the invention being closed system to produce a two-phase liquid metal indicated by the appended claims rather than by the vapor flow, the heating temperature being such as foregoing description, and all changes which come to effect substantially isothermal expansion of the within the meaning and range of equivalency of the 10 vapor bubbles, thereby to accelerate the two-phase claims are, therefore, intended to be embraced therein. flow;

What is claimed is: (c) a magnetohydrodynamic (MHD) generator lo 1. A method for producing electrical power by means cated along the flow path of the two-phase liquid of a magnetohydrodynamic (MHD) generator, com metal-vapor flow formed by the heated mixture; prising 15 (d) means for condensing the two-phase flow to form (a) heating a mixture of liquid metal and a low boiling a single phase flow of metal liquid containing pro temperature propelling liquid at a relatively low pelling liquid droplets; and temperature to form a two-phase liquid metal (e) means for propelling said single-phase flow for vapor flow, the heating temperature being such as 20 reheating by said heating means. to effect substantially isothermal expansion of the meansThe8. apparatus according to claim 7, wherein said for condensing the two-phase flow comprises a vapor bubbles, thereby to accelerate the two-phase flow; condenser-heat exchanger, and further wherein the heat (b) directing said two-phase metal-vapor flow that is given off by the condensation of the vapor-phase through an MHD-generator to generate electricity; is utilized to heat a fluid circulating in said heat ex (c) condensing the vapor phase from said two-phase 25 changer. 9. The apparatus according to claim 7, wherein said liquid metal to form liquid metal carrying propel mixture of metal liquid and propelling liquid are heated ling liquid droplets; and via a heat-exchanger located between, and being in fluid (d) recycling and reheating said liquid metal and said propelling liquid droplets to again form the two 30 communication closed duct with, said heating means and said system.

phase liquid metal-vapor flow. 10. The apparatus according to claim 7, wherein said 2. The method according to claim 1, wherein said means for propelling the single-phase flow to be re vapor-phase from said two-phase liquid metal-vapor is heated by the heating means includes a MHD pump. condensed by means of a condenser-heat exchanger, 11. The apparatus according to claim 7, and further and further including the step of circulating a fluid in 35 comprising means for dispersing said propelling liquid said condenser-heat exchanger to effect the heating of in the liquid metal prior to the heating thereof by the said fluid by means of the heat given off by the conden heating means.

sation of the vapor-phase. 12. The apparatus according to claim 7, wherein said 3. The method according to claim 1, and further heating means includes a solar energy absorber in fluid including the step of providing an MHD pump along 40 communication with the interior of the closed duct the flow path of the liquid metal and propelling liquid system.

droplets, and propelling the liquid metal and liquid 13. The apparatus according to claim 12, wherein said droplets from said generator for subsequent recycling solar energy absorber contains liquid metal to be heated and reheating to the two-phase condition. and, in turn, heat the mixture flowing in a heat 4. The method according to claim 1, and further 45 exchanger located between, and in fluid communication comprising the step of homogeneously dispersing said with, said solar energy absorber.

propelling liquid in the liquid metal prior to heating the 14. Apparatus for converting solar energy into elec mixture to the two-phase condition. tricity and for heating a fluid comprising 5. The method according to claim 1, wherein said (a) a closed system containing a mixture of an electri heating is performed in a solar energy absorber, and 50 cally conductive liquid and of a low boiling tem further wherein said liquid metal and propelling liquid perature propelling liquid; droplets are recycled through said solar energy ab (b) solar energy absorbing means for heating said sorber to be reheated therein. mixture to form a two-phase flow; 6. The method according to claim 5, and further (c) a magnetohydrodynamic (MHD) generator lo comprising the steps of 55 cated along the path of the two-phase flow; (e) providing a heat exchanger between said solar (d) a condensing and heat-exchanging means for con energy absorber and the closed loop fluid flow densing said two-phase flow into a single-phase path; mixture of the electrically conductive liquid con (f) providing a liquid metal for absorbing the solar taining droplets of the propelling liquid and for energy in said solar absorber; and 60 heating a fluid circulating in said heat-exchanger; (g) circulating said liquid metal in a closed loop be and tween said absorber and said heat-exchanger to (e) means for propelling said single-phase mixture to effect the heating of said mixture of liquid metal be reheated by said solar energy absorbing means. and propelling liquid. : :