JPS631441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to working fluids used in heat engines.

A conventional system that attempts to utilize waste heat is a two-fluid coupled turbine based on the Rankine cycle. In order to dispose of the swelling waste gas at the end of the exhaust gas caused by the saturation pressure of water vapor being too low, it has been proposed to use gases such as freon, ammonia, helium, and hydrocarbons as working fluids. Freon is used.

There is also an idea to utilize the superior efficiency of carbon dioxide gas at temperatures above 200°C as a Rankine cycle engine.

However, these working fluids are in the gas phase at normal temperature and pressure, and their purpose of use is different, so they cannot be used in heat engines. In addition, two-fluid cycle turbines are being considered that use liquids and metals such as mercury, sodium, potassium, and rubidium as working fluids because of their advantageous critical temperature as a high-temperature turbine.In actual engines, mercury is used, but mercury Corrosion of various metals due to this has become a serious problem.

In addition, heat pipes are being researched to measure heat superconductivity. However, the organic and inorganic working fluid used in the heat pipe is not a working fluid for creating pressure as in the present invention. A closed system engine using acetone H ₃ COCH ₃ as a heating medium has been invented for the purpose of solar power generation, but acetone has a temperature of 2797.3 mmHg at 100°C, so it is difficult to think of it as suitable as a heating medium for obtaining pressure. . Therefore, the physical properties of the working fluid must be (1) high pressure can be obtained with little heat absorption, (2) rapid condensation at normal temperature and pressure, (3) difficulty in ignition, and (4) corrosivity. (5) There is little generation of wet steam.

Next, we will consider the molecular weight of molecules that are promising as working fluids suitable for combined cycle engines. hydrogen
The molecular weight of _H2 is 2.016, nitrogen _N2 is 28.01, oxygen _O2 is
32.00, methyl alcohol CH ₃ OH 32.04, ethyl ether C ₂ H ₅ OC ₂ H ₅ 74.12, ammonia NH ₃
17.03, water _H2O is 18. First, water, which consists of two hydrogen atoms and one oxygen atom, is a stable and inert molecule with strong chemical bonds. It is difficult to decompose into oxygen and hydrogen without going through the process of hot water molecules at 100 to 1000 degrees Celsius. Thermal dissociation of water is 0.027% at 1000℃ and 0.6 at 1800℃
%, 1.8% at 2000℃, and about 15% at 2800℃.
On the other hand, the molecular weight of ammonia consisting of 3 hydrogen atoms, which is considered to be active with respect to 1 nitrogen atom, is 17.03, which is not much different from water, which has a molecular weight of 18. Ammonia can be easily liquefied by applying 8.46 atm at room temperature of 20°C, and has already decomposed into nitrogen and hydrogen at room temperature of 1 atm. This means that ammonia swells to a large extent due to a small amount of heat absorption relative to water, creating a large gas pressure. As is well known, ammonia is alkaline. This means that part of the ammonia NH ₃ dissolved in water combines with water to form ammonia hydroxide NH ₃ + H ₂ O.
It becomes NH ₄ OH, and ammonium hydroxide ionizes and releases hydroxide ions as shown below. NH ₄ OHNH ₄ ⁺ +OH ^- This results in aqueous ammonia, which has a somewhat lower boiling point than water, but has a much higher boiling point than ammonia, although it has a lower molecular weight than water. When heated as a working fluid (compound), ammonia molecules, which are considered to be active, are pushed out from water molecules and easily obtained as a high-pressure gas.When the temperature is low, the properties of water prevail and it condenses quickly, creating a working fluid with good physical properties. Become. However, ammonia is corrosive to copper alloys in a mixed gas phase of carbon dioxide gas, water vapor, and ammonia, and copper alloys with free machining properties exhibit hydrogen embrittlement along crystalline fault lines, so copper alloys used in heat engines are Some parts must be changed to iron. Next, the boiling point of methyl alcohol is
64.65℃, showing a pressure of 2598mmHg at 100℃.
Although it is a working fluid as a solvent that is not corrosive and can be used at room temperature, it is flammable, so the amount of water to be added must be determined in consideration of the conditions of the engine in which it will be used. Next, ethyl ether has a boiling point of 34.5℃ and 4855 at 100℃
mmHg and has a slightly lower boiling point as a working fluid, so alcohols (such as methyl alcohol)
Although it must be used in combination with other materials, it is not corrosive to metals and is a good working fluid. However, since it is highly flammable, consideration must be given to adding water.
Next, a melt of methyl alcohol with 10 to 20% ammonia added has a boiling point of around 50°C depending on the physical properties of each molecule, and if this is used as the working fluid, the highest pressure can be obtained. However, it is flammable, so it is necessary to add some water, and corrosion to metal must also be taken into consideration. It continues to develop based on the theories of S Clausius, Sadej Carnot, etc. and the physical properties of water.
Among heat engines, Rankine cycle engines still tend to use working fluids at high pressures and at sky-high temperatures. However, if you think about it simply, what is needed for a heat engine is not temperature but pressure, and all that is needed is a working fluid that exhibits a liquid phase at room temperature and pressure (below 50 degrees Celsius at 1 atm) and can obtain high pressure by absorbing a small amount of heat. become. Therefore, if the working fluid of the present invention developed based on this idea is used in an Otto-Rankine combined cycle engine, a highly efficient hot air flow that cannot be obtained with water will be obtained.

In addition, when used in many prime movers that obtain heat absorption, it not only converts thermal energy efficiently through low-temperature combustion, but also reduces the amount of NOx produced in flue gas from boilers, etc. due to low-temperature combustion. It becomes less.

Here, the working fluid of the present invention and several other working fluids to be compared with this were tested for the pressures obtained by heat absorption using a gas pressure tester as shown below. Ta. The specifications are: working fluid tank 300 x 35φ x 4.0tmm made of iron, band heater inner diameter 35φ x 40b 200W x 4, thermometer 0~
400°C (manufactured by Shinko Denki) and a pressure gauge of 0 to 150 Kg/cm ² (manufactured by Tokyo Keiki). The curve obtained by water absorbing heat in the comparison diagram of working fluids in Figure 1, which was actually measured, is not derived from the steam table of the Japan Society of Mechanical Engineers, but is based on actually measured gauge pressure. Also, since this was a comparative test, gauge errors were not taken into consideration. The test results are shown in FIG. Among these, the properties of the working fluid of the present invention, which is a mixture of methanol and ammonia at 12%, were confirmed in a similar test conducted at the Hiroshima Prefectural Western Industrial Technology Center. (Guangxi Technology No.
1320) However, what should be noted here is that water (molecular weight
18) and ammonia water (molecular weight 17.884) consisting of 12% ammonia due to endothermic action, ammonia water, which has a lower molecular weight, shows a higher pressure than water.

The large difference in thermal expansion of gases is thought to be due to the atomic structure of the molecules of substances that easily become gases.

For example, one oxygen atom consisting of eight electrons,
Atomic bond between water, which consists of two hydrogen atoms each consisting of one electron, and ammonia, which consists of one nitrogen atom consisting of seven electrons, and three hydrogen atoms consisting of one electron. When comparing the (mutual attraction), it is clear that the mutual attraction exerted on two hydrogen atoms by the oxygen atom, which has more electrons, is stronger than that of ammonia.

In other words, water is more difficult to expand than ammonia.

It is thought that the difference in mutual attraction between molecular bonds caused by atomic bonds is the difference in thermal expansion obtained by endothermic absorption of each molecule.

[Brief explanation of the drawing]

FIG. 1 is an actual measurement curve diagram of pressure changes obtained by heat absorption in the working fluid and water of the present invention.

Claims (1)

[Claims] 1 The composition of the working fluid used in heat engines is methyl alcohol CH ₃ OH and some ammonia NH ₃
Working fluid with added.