US3702534A - Power fluids for rankine cycle engines - Google Patents

Power fluids for rankine cycle engines Download PDF

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Publication number
US3702534A
US3702534A US113293A US3702534DA US3702534A US 3702534 A US3702534 A US 3702534A US 113293 A US113293 A US 113293A US 3702534D A US3702534D A US 3702534DA US 3702534 A US3702534 A US 3702534A
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Prior art keywords
rankine cycle
working substance
fluids
boiler
employed
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US113293A
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English (en)
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Max F Bechtold
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EIDP Inc
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EI Du Pont de Nemours and Co
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B3/00—Other methods of steam generation; Steam boilers not provided for in other groups of this subclass
    • F22B3/02—Other methods of steam generation; Steam boilers not provided for in other groups of this subclass involving the use of working media other than water
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K11/00—Plants characterised by the engines being structurally combined with boilers or condensers
    • F01K11/04—Plants characterised by the engines being structurally combined with boilers or condensers the boilers or condensers being rotated in use
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
    • F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours

Definitions

  • BACKGROUND OF THE iNvEN'noN is an inexpensive and readily available power fluid, it is not without disadvantages such as expansion upon freezing. Also, because of the nature of the temperature entropy diagram, it is generally necessary to use superheated steam at high pressure and temperature in order to obtain acceptable efficiency and to avoid wet vapor upon expansion. Further, when turbines are employed it is necessary to employ multiple stages. For these reasons, steam engines operating on the Rankine cycle are generally large stationary engines such as those employed for the production of electric power.
  • the present invention is, therefore, directed to providing novel fluids useful in Rankine cycle engines and particularly in small portable engines with efficient air-cooled condensers.
  • the present invention can be defined as a method of generating power in which, a working substance is heated and vaporized, does work in a prime mover, and after doing said work is condensed and recycled, wherein said working substance consists essentially of at least one perhalogenated benzene having the formula in which x is from to 2 y is from 0 to 4 z is from 2 to 4 and 1.5x y 2.5 to 4 inclusive.
  • the substances of the present invention are suited to use in Rankine cycle engines wherein the working substance is subjected to centrifugal force during the steps of heating and condensation and is recycled by centrifugal force.
  • the working fluids employed in the present invention thus include preferred to the pure isomers since such mixtures have lower melting points.
  • FIG. 1 is a diagram showing the various stages of a Rankine cycle including an optional regeneration step to optimize the efficiency.
  • FIG. 2 is a temperature-entropy diagram for trichlorotrifluorobenzene.
  • This boiler can be any conventional form of boiler. Boilers of the rotating type wherein the liquid is distributed over a large surface by centrifugal force are particularly efficient thermally and produce high quality vapor. Such boilers are preferred for use with the working substances of the present invention.
  • the vapor then passes to a prime mover such as a turbine 2 where it expands in the turbine nozzles and is employed to run an impulse turbine.
  • the vapor can then be passed to a condenser 3 where it is condensed back to the liquid phase.
  • the liquid is then pumped back to the boiler l by pump 4 and thus recycled.
  • small air-cooled condensers of high efficiency can be employed. It is, therefore, desirable to employ a condenser of smaller diameter attached to and rotating with the boiler.
  • the liquid can then be pumped from the condenser to the boiler by centrifugal force.
  • Expansion of the vapor in the prime mover is essentially isentropic.
  • the vapors of the working substances of this invention become superheated upon expansion.
  • the efficiency of the cycle can, therefore, be improved by passing the exhaust from the turbine employed as a prime mover through a regenerator 5 wherein the excess heat is removed from the vapor and transferred to the boiler feed as taught by US. Pat. No. 3,040,528.
  • FIG. 2 there is shown the temperature-entropy diagram for trichlorotrifluorobenzene, one of the working'fluids of the present invention.
  • Power is generated by the expansion of the trichlorotrifluorobenzene from vapor at a pressure of 149.7 p.s.i.a. and temperature 620F., point 11 on the diagram, in a turbine. Expansion is essentially isentropic and the working fluid, therefore, is cooled following the line from 11 to 12 to a temperature of 463F. at the condensing pressure of 3.07 p.s.i.a.
  • the vapor is cooled from 463 to 299F., preferably in a regenerator but optionally in the condenser, to point 13 on the diagram.
  • the vapor is then condensed to liquid at 299F. and 3.07 p.s.i.a. following the path 13 to 14 in the figure.
  • the liquid at point 14 is pumped to 149.7 p.s.i.a. and heated by the boiler, and also by regeneration, if that is employed, to point 15 and thereafter evaporated to vapor at 620F. and 149.7 p.s.i.a. to point 11 thereby completing the cycle.
  • this Rankine cycle thermal efficiency is about 20 percent. For 70 percent regeneration, the efficiency is about 24 percent.
  • a preferred range of boiling points is from l75-225 C.
  • a number of other properties are highly desirable for working fluids in Rankine cycle engines. These properties are: I THERMAL STABILITY DURING ENGINE OPERA- TlON This is necessary to permit prolonged operation in a closed system. In particular, any decomposition generating noncondensible gases would blanket and inactivate the condenser or require a constant purging device. Further, decomposition of the working fluid should not produce insulating solid deposits in valves, nozzles, seals or on heat exchanging surfaces.
  • the working fluids are preferably such that inhalation of vapors from accidental breakage or spills should not be damaging to health.
  • LOW FLAMMABILITY The flammability of the fluids should be as low as possible to minimize the risks of fire.
  • LOW CORROSIVITY The liquids should not attack metals employed for engine construction.
  • High MOLECULAR WEIGHT High molecular weight is particularly beneficial in the construction of low horsepower (i.e., 1000 hp.) turbine engines, since it permits operation with a single stage turbine at reasonable speeds.
  • the molecular weight should be at least 150.
  • the liquids employed in the present invention all have molecular weight greater than 235.
  • rotary boilers in which the working substance is maintained in the liquid state on an extended cylindrical surface by centrifugal force are particularly useful for small Rankine cycle engines.
  • Rotary condensers which have a smaller diameter than the boiler and rotate therewith can be employed with advantage, and the centrifugal force employed to pump the liquid (optionally through a regenerator) from the condenser to the boiler.
  • the greater the liquid density of the working substance the smaller the diameter of the boiler (and consequently the smaller engine) which is required at a given speed of rotation or conversely, for a given size of boiler and condenser the slower the rate of rotation required to achieve efiicient operation.
  • the freezing point of fluids employed in Rankine cycle engines must be well below the operating condenser temperature. Even more preferably, the fluids should be liquid at ambient temperatures, although, in contrast to water, freezing of organic fluids, which contract on freezing, will not cause breakage of condenser tubes, etc.
  • the perhalobenzenes of the present invention are surprisingly stable thermally, particularly in the presence of aluminum, aluminum-alloys, 0r aluminized steel which are desirable materials of engine construction, at temperatures in excess of about C.
  • the compounds are essentially nontoxic. Further, the compounds do not support combustion.
  • the various position isomers of a given perhalobenzene also boil within about i 2C. of each other so that mixed isomers can be employed with advantage. Such mixtures have a lower freezing point than the pure isomers.
  • the density of the liquids about (1.7 to 2.3) is also suited for use with rotating boilers and condensers.
  • the compounds of the present invention can be made by a variety of techniques known in the art.
  • the chlorofluorobenzenes can be made by heating hexachlorobenzene with potassium fluoride, preferably in a polar medium such as sulfolane, dimethylsulfone, dimethylformamide, N-methylpyrrolidone and the like. This process ordinarily produces a mixture of compositions and isomers thereof, the predominant composition being determined both by the relative amounts of potassium fluoride and hexachlorobenzene employed and the length of time the reactants are held at elevated temperatures.
  • the product boiling in the vicinity of 198 consisted largely of a mixture of position isomers of C,Cl F A minor amount of hydrogen containing impurities were present, which could be removed by further careful fractionation.
  • the mixture of compounds is suitable for use as the working substance in Rankine cycle engines.
  • Bromofluorobenzenes can be made by brornination of partially fluorinated benzene with bromine in oleum as described in British Pat. No. 996,496.
  • the bromine atoms of the bromofluorobenzenes can be partially or wholly replaced by reaction with chlorine to obtain bromochlorofluorobenzene or chlorofluorobenzene.
  • chlorine gas is passed at the rate of 100 cc/minute through 100 cc of 1,3- dibromotetrafluorobenzene illuminated with a 25 watt electric light bulb. After 45 minutes a 5 3 percent yield of l-bromo-3-chlorotetrafluorobenzene is obtained which can be isolated by distillation.
  • C BrCl BJ3 and C Br ClF can be obtained by passing 6 by distillation.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US113293A 1971-02-08 1971-02-08 Power fluids for rankine cycle engines Expired - Lifetime US3702534A (en)

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US11329371A 1971-02-08 1971-02-08

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US (1) US3702534A (https=)
CA (1) CA954310A (https=)
DE (1) DE2205924A1 (https=)
FR (1) FR2126752A5 (https=)
GB (1) GB1315105A (https=)
IT (1) IT947360B (https=)
NL (1) NL7201570A (https=)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3802185A (en) * 1972-06-14 1974-04-09 Du Pont Generation of power using trichlorobenzene in a rankine-cycle engine
JPS4995003A (https=) * 1973-01-18 1974-09-10
US4463567A (en) * 1982-02-16 1984-08-07 Transamerica Delaval Inc. Power production with two-phase expansion through vapor dome
US20120006022A1 (en) * 2010-07-09 2012-01-12 Purdue Research Foundation Organic rankine cycle with flooded expansion and internal regeneration
US20150362234A1 (en) * 2013-01-27 2015-12-17 Nanjing Reclaimer Environmental Teknik Co., Ltd Cold dynamic cycle refrigeration apparatus

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008116667A1 (en) * 2007-03-28 2008-10-02 John Butler An engine system

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3282048A (en) * 1965-06-04 1966-11-01 Allied Chem Power fluid

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3282048A (en) * 1965-06-04 1966-11-01 Allied Chem Power fluid

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3802185A (en) * 1972-06-14 1974-04-09 Du Pont Generation of power using trichlorobenzene in a rankine-cycle engine
JPS4995003A (https=) * 1973-01-18 1974-09-10
US4463567A (en) * 1982-02-16 1984-08-07 Transamerica Delaval Inc. Power production with two-phase expansion through vapor dome
US20120006022A1 (en) * 2010-07-09 2012-01-12 Purdue Research Foundation Organic rankine cycle with flooded expansion and internal regeneration
US8667797B2 (en) * 2010-07-09 2014-03-11 Purdue Research Foundation Organic rankine cycle with flooded expansion and internal regeneration
US20150362234A1 (en) * 2013-01-27 2015-12-17 Nanjing Reclaimer Environmental Teknik Co., Ltd Cold dynamic cycle refrigeration apparatus
US9823000B2 (en) * 2013-01-27 2017-11-21 Nanjing Reclaimer Environmental Teknik Co., Ltd Cold dynamic cycle refrigeration apparatus

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Publication number Publication date
DE2205924A1 (de) 1972-08-24
CA954310A (en) 1974-09-10
IT947360B (it) 1973-05-21
NL7201570A (https=) 1972-08-10
FR2126752A5 (https=) 1972-10-06
GB1315105A (en) 1973-04-26

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