3. The Organic Rankine Cycle

By organic fluid or compost we mean any compost, not necessarily present in living organisms, containing a significant quantity of carbon.

A great deal of interesting information and anecdotes about unusual working fluids and much else can be found in “The Museum of Retro Technology”. Available at http://​www.​douglas-self.​com/​MUSEUM/​museum.​htm. (cited May 27, 2012)

The methyl alcohol, known also as methanol, is a well-known alcohol fuel. Its chemical formula is CH₃OH, its boiling point is 65 ^∘ C and at 25 ^∘ C it has a vapour pressure of 0.17  bar. The critical temperature is 239 ^∘ C and the critical pressure 81  bar.

Here, the term “binary” refers to the working fluid, obtained by mixing two compounds. In its modern usage, the term “binary” identifies an engine with two working fluids that are distinct and physically separate from each other, each operating at a different temperature.

The chemical formula for diethylether, which is extremely inflammable, is \(\mathrm{CH_{3}\mbox{ \textendash }CH_{2}\mbox{ \textendash }O\mbox{ \textendash }}\) \(\mathrm{CH_{2}\mbox{ \textendash }CH_{3}}\), and its boiling point is 34 ^∘ C; at a temperature of 25 ^∘ C, the vapour pressure is 0.71  bar. The critical temperature is 194 ^∘ C and the critical pressure 36.4  bar.

The term “naphtha” is generally used to identify mixtures of hydrocarbons. Naphtha is often used as a feedstock for the production of gasoline.

The methyl chloride, or chloromethane, with a chemical formula CH₃Cl, has a boiling point of -24.2 ^∘ C.

Chemical formula C₆H₅Cl, boiling point 131.76 ^∘ C, critical temperature 359.25 ^∘ C and critical pressure 45.2  bar

,1,2-trichloro-1,2.2-trifluoroethane, with boiling point of 47.7 ^∘ C

Toluene, or methylbenzene, with chemical formula \(\mathrm{C_{6}H_{5}CH_{3}}\). Boiling point at 110.4 ^∘ C, critical temperature 318.6 ^∘ C and critical pressure 41.08  bar

Dichlorodifluoromethane, CCl₂F₂. Boiling point -29.8 ^∘ C.

A solar pond is a vast area of salt water which, due to the favourable salt gradient, behaves as a large flat solar collector of thermal energy. A solar pond can be used for a variety of applications, amongst which is the generation of electricity.

Born in Florence in 1880 to parents originating from Trieste. Having graduated in Civil Engineering at Rome in 1904, he moved to Munich, where, in 1911, he obtained his doctorate in Thermal and Mechanical Science. Returning to Italy, in 1917 he obtained the professorship in Fluid Machinery at the Polytechnic of Milan, which he held until his retirement. (1951). He died on 12 November 1962.

Born in Naples on 1 June 1893, he was a professor at the University of Naples and headed the Institute of Thermal, Hydraulic and Agricultural Machinery until 1963. He died in Naples on 1 December 1967.

Ethyl chloride, or chloroethane, has the chemical formula \(\mathrm{CH_{3}\mbox{ \textendash }CH_{2}Cl}\), a boiling point of 12.35 ^∘ C, a critical temperature of 187.25 ^∘ C and a critical pressure of 52.7  bar.

In the newspaper The Deseret News—November 15, 1951 (the oldest daily newspaper published in the state of Utah, at Salt Lake City)—there can be read the following brief but curious note:

The Sun Could Supply Electricity, by A. De Montmorency New York, November 14—A new Italian invention will permit each house to generate its own electricity without any expense of fuel, simply by using the sun’s energy. A dispatch from Milan to informations of Madrid reported that Prof. Mario Dorning of that Lombardian city had built with the help of Daniel Gasperini, an engineer, a solar engine capable of producing 10 kilowatt-hours daily. Three such machines have been sent to Egypt for a tryout.

Born in Naples on 18 October 1938. He graduated with full honours in 1962, discussing his thesis on “Prestazioni degli effusori a spina nei propulsori a razzo”. In the same year that he graduated, he won an AGARD scholarship for a specialisation course in Experimental Aerodynamics at the Centre de Formation en Aérodynamique Expérimentale, Von Kármán Institute, in Belgium. In 1963 he was awarded his diploma with distinction and received the Theodore Von Kármán prize, which was reserved for the best student of each year. From 1973 to 2009 he was full-time professor in Machinery at the Polytechnic of Milan. He was director of the Machinery Section at the Department of Energy at the Polytechnic of Milan and, for many years, director of the research doctorate in Energy. He died on 9 May 2010.

Perchloroethylene, or tetrachloroethylene, Cl₂C=CCl₂ is an excellent solvent of organic substances, which is not particularly volatile and is non-inflammable. For these reasons, it is widely used these days in dry cleaning. It has a boiling point of 121.1 ^∘ C.

,2-Dichlorotetrafluoroethane, \(\mathrm{ClF_{2}C\mbox{ \textendash }CF_{2}Cl}\), boiling point 3.43 ^∘ C, critical temperature 145.75 ^∘ C, critical pressure 32.37  bar.

One with Flutec PP3, perfluoro-1,3-dimethylcyclohexane, C₈F₁₆, boiling point 102 ^∘ C, critical temperature 241.55 ^∘ C and vapour pressure 4.8  k Pa at 25 ^∘ C; the second with Flutec PP5, perfluorodecalin, or perfluoronaphtalene, C₁₀F₁₈, boiling point 142 ^∘ C, critical temperature 292 ^∘ C and vapour pressure 0.88  k Pa at 25 ^∘ C

,4-Dichlorobenzene, C₆H₄Cl₂, boiling point 174 ^∘ C

A notable exception was (and continues to be after 40 years) a small generator for generating energy in remote places, called the Remote Power Unit: made with power levels between 600  W and 4  k W, it is very widespread.

Ortho-, meta- and para-terphenyls (\(\mathrm{(C_{6}H_{5})_{2}C_{6}H_{4}}\)) in mixtures. A prototype of a commercial reactor, of 45.5  M Wt, was made anyway (under a project of 1956 and the reactor was operational from 1963 to 1966) in Ohio in the USA: the Piqua OMR plant [17].

The octamethyltrisiloxane (MDM) is a member of the family of methylsiloxanes fluids, attractive working fluids for organic fluid cycles due to their technical characteristics: they are not toxic, only moderately inflammable and reasonably stable up to 300–350 ^∘ C (see [19]).

Charcoal, obtained by pyrolysis of vegetable biomass, was the only secondary fuel used by pre-industrial societies. Coke, produced by the pyrolysis of coal, was used in England during the 1640s and replaced charcoal in iron smelting towards the middle of the 1700s, when its production costs had dropped sufficiently to make it competitive.

The dimensions of the heat exchangers depend on the thermal power but also on the transport properties of the fluids, which directly influence the heat exchange coefficients.