WO1989012748A1

WO1989012748A1 - Process and apparatus for conversion of low value thermal energy in mechanical energy by thermal expansion of an expansion medium

Info

Publication number: WO1989012748A1
Application number: PCT/NL1989/000051
Authority: WO
Inventors: Gerard Willem Ackers; Jeichienus Adriaan Van Der Werff
Original assignee: Torus Rotary Systems B.V.
Priority date: 1988-06-21
Filing date: 1989-06-19
Publication date: 1989-12-28
Also published as: AU3844889A; NL8801578A

Abstract

Process for conversion of low value thermal energy into mechanical energy by thermal expansion of an inert liquid expansion medium, which in a relatively low temperature range of not higher than 80°C has a relatively high expansion coefficient, which medium is contained in pressure tubes (3) included in a regeneration cylinder (1), which pressure tubes are stepwise heated or cooled by a thermal medium circulating in the cylinder without parts of the thermal medium with different temperatures being intermingled. Examples of the expansion medium are paraffins.

Description

Process and apparatus for conversion of low value thermal energy in mechanical energy by thermal expansion of an expansion medium.

The present invention relates to a process and apparatus for conversion of low value thermal energy in mechanical energy by thermal expansion of an expansion medium, which expansion is converted into mechanical energy, for instance by a pressure exerted on a piston transferred to a hydraulic motor. Generally the invention is directed to a process and apparatus capable of converting low-temperature-energy in mechanical energy, as suitable for driving of motors and so on.

Up to now these conversions are mainly based on the thermal expansion of gas according to the well known gas law, wherein the efficiency is proportional with the temperature difference. For a high efficiency high temperatures are necessary. There is, however, a surplus of low-temperature-energy on earth, like geo heat, wasted heat and sun energy, which generally can be indicated as low-temperature-energy. Up to now there are problems to utilize such cheap low-temperature-energy and thus there is a need for a process and apparatus permitting to utilize low-temperature-energy in an efficient way, such as for driving of motors and so on.

The invention has as an object to use other media than gases with which this mainly happened up to now and to use in stead of gas mainly liquids, wherein by a special designed, staged thermal regeneration the process and apparatus according to the invention are applicable in a profitable way.

It has already been proposed to utilize the expansion of water, such as described in an article by J.F.J. Malone (Journal of The Royal Society of Arts. June 12, 1931, pages 680-603). He worked with the expansion of water at a temperature between 20 and 270°C and pressures of about 700 bar, wherein a yield of 25% should have been reached. This liquid motor of Malone is discussed in a report of the Longman Group Limited 1972. pages 78 and 90. It is to be understood that a major objection of this apparatus is its gigantic extent, due to the low expansion coefficient of water, wherein also very high pressures of about 700 atm were necessary. Such constructions give rise to sealing problems because the high pressure is acting directly on to the motor. Also heat regeneration takes place under pressure. In the Longman article, page 90 , it is said that in thermodynamics this variation is completely overlooked and not further developed. As far as applicant is aware there are no further developments reported in this field. If one considers the above mentioned disadvantages of this variation it is clear that there was not much incentive to pursue the research and to try to find an alternative for the normal and in the cause of time perfected explosion motor. It is thus a main object of the invention to provide a process and apparatus for conversion of low value energy in mechanical energy, utilizing the expansion of specific materials, especially liquids, for such a conversion. It has been found that one is able by applying certain liquids, especially hydrocarbons, such as paraffines and derivatives thereof, as expansion media at relatively low temperatures , high pressures can be generated which are suitable a for driving purposes, while the efficiency by/specifically staged heat regeneration carried out at atmospheric pressure can be brought to a suitable value. Thus the invention relates to a process for the conversion of low value energy in mechanical energy by thermal expansion of an expansion medium, which expansion is converted in mechanical pressure, for instance a pressure exerted on a piston, which medium is cooled and heated in a cyclewith a thermal medium, characterized in that the heating and cooling are carried out by stage-wise heating and cooling an expansion medium in a plurality of steps without parts of the thermal medium with different temperatures being intermingled, which treatment is carried out in a cycle. Further the invention comprises an apparatus for carrying out this process, which hereafter will be called a hydrothermal generator.

In the process as expansion medium preferably a material is used with a high expansion coefficient in a relatively low temperature range, which preferably comprises ambient temperature. As such a medium saturated hydrocarbons. which possibly contain inert substituents and derivates thereof are suitable, in particular paraffines which show expansion coefficients at atmospheric pressure and a temperature between ambient temperature and about 17-80°C of the order of 15%. The term paraffine comprises herein a mixture of solid hydrocarbons which are crystallized from higher boiling petroleum fractions. These major components are generally alkanes with linear chains. The paraffines as commercially available however contain also some parts of solid branched or cyclic hydrocarbons and sometimes also a small percentages liquid oil. For the invention paraffines as commercially available, like destillate paraffines, and wax types etc. are acceptable, as well as mixtures and combinations of these products. Also derivates thereof, of which the melt behaviour is not substantially changed and which for the purposes of the invention can be considered as inert, can be used. Also other heavy hydrocarbons obtained from the treatment of petroleum, like extractionresidues, tar materials etc. can be used at the condition that they are mainly liquid in the temperature range as mentioned. Furthermore long chain fatty acids, for instance with more than 10 carbon atoms, especially those which are liquid or semi solid in the temperature range under view, like stearic acid and mixtures of such fatty acids, especially saturated fatty acids, are very acceptable. See for instance Handbook of

Chemistry, 1954, page 2066 and 2067, wherein paraffine and tar are mentioned. It appears from the citation that the critical expansion coefficients of these materials are respectively 5,88 and 6,8 x 10^-4 Page 20 shows that for paraffines the linear thermal expansion coefficient at temperatures of 38-49°C is considerably higher than at temperatures of 16 to 38, respectively 0 to 16°C. The materials used can be solid in the low temperature range, and melting during the heating cycle. Preferably materials are used of which the greatest expansion is reached in a relatively low temperature range, especially a range which comprises ambient temperatures. It is evident that such a temperature range is most economical, while also waste heat as such best can be utilized.

During the expansion of the said media high pressures are generated. As is known liquid is non-compressible as a result of which in the present invention pressures can be reached of about 1000 bar. By using the expansion medium according to the invention it is therefore possible by combining this high pressure with a relatively high expansion at moderate temperatures to reach a relatively high potential energy (distance x pressure) and to use it. Thus these media are preferably contained in pressure pipes which have a relatively low diameter in comparison to their length to accomodate these pressures. The coupling with for instance a hydraulic motor can be made by the interaction of the pressure generated by the thermal expansion on a plunger which then will be displaced. Preferably the high pressures generated in the expansion medium are firstly converted in lower pressures, which last ones are for instance transferred to a hydraulic motor. For this one uses a piston which in comparison with the first plunger is substantially larger so that the pressures are reduced, which large piston is running in a oil cilinder and displacing a hydraulic medium. There is used a plurality of pressure groups, which are defined as a number of coacting regeneration cilinders, which cilinders separately comprise a number of pressure pipes with thermal medium, which arecyclicallyheated and cooled and which push the hydraulic medium through the large cilinder over a buffer to the hydraulic motor to be driven.

It is of a special interest for this arrangement that the heat is efficiently regenerated to have the process run efficiently. A thermal medium is defined as a medium, like water or another liquid, with which the pressure pipes in a regeneration cilinder are cooled and heated.

The hydrothermic generator according to the invention for carrying out the said process comprises one or more isolated regeneration cilinders. in which cilinder(s) a plurality of pressure pipes is mounted, in which pipes the expansion medium as earlier defined is present, which regeneration cilinder is coupled with a low pressure cilinder, in which regeneration cilinder a thermal medium for the regeneration of heat can be circulated, in the said regeneration cilinders separation pistons being present which prevent that during regeneration hot and cold thermal medium are intermixed. The apparatus preferably contains a number of regeneration cilinders which themselves contain a number of pressure pipes, for instance 3-10 or more, dependent of the construction. The number of regeneration cilinders and pressure pipes will be adjusted, dependent of the applications aimed at.

It is a special characteristic of the hydrothermal generator according to the invention that in the regeneration cilinders displaceble or floating separation pistons are present which are arranged in such a way that the contents of the separate regeneration cilinders. which have different temperatures, can not be intermingled. The generator is further characterized in that two or more groups regeneration cilinders are connected between hot and cold chambers wherein in the cold part a dosing pump with control means is present, which dosing pump has such a stroke that the displacement thereof is about somewhat larger or substantially equal to that of the regeneration cilinder in a pressure group, the one pair cilinders becoming cold and the other pair being warmed wherein by separation pistons present in the regeneration cilinders intermingling of thermal medium between regeneration cilinders is prevented. According to another characteristic the pressure pipes are proportionally long and thin, so that they can accomodate high pressures, while the wall thickness is as small as possible for a favourable heat transport.

The invention will now be illustrated by means of the drawing, wherein the figures have the following meanings:

Figure 1 is a graph of the expansion coefficient of two kinds of paraffines A and B in de temperature area of 20 to 60°C, wherein the values are determined of 70 cm³ paraffine.

Figure 2 is a cross section of a hydrothermal generator according to the invention, wherein two regeneration cilinders, containing pressure pipes with expansion medium, as well as the connection to the working cilinders are indicated. Figure 3 is a cross section along the line A-B of figure 2. which shows the mutual arrangement of the regeneration cilinders. of which five are drawn, with seven pressure pipes in each regeneration cilinder.

Figures 4a, 4b and 4c illustrate a schematic representation of the courseof the thermal regeneration in the regeneration cilinder, wherein for simplification purposes the regeneration cilinders in the drawing are placed one after the other in line.

Figure 5 shows a schematic cross section according to figure 3, wherein the two positions of the valves in the cycle indicated in figures 4a, 4b and 4c are shown.

Figure G shows schematically the arrangement of the driving part of the low pressure cilinder of the hydrothermal generator, wherein for purposes of simplicity the regeneration cilinders are omitted. In figure 1 a graph of the expansion of two kinds of paraffines A and B in relation to the temperature is illustrated. On the abscis the temperature is indicated in °C and on the ordinate the expansion in cm³. The curvesare determined by starting from 70 cm³ paraffine which in the course of 24 minutes is heated from the solid condition. Paraffine A has a melting point of 42-44°C and paraffine B of about 55°C, which in the graph is shown with a cross. Both curves show a strong rise of the expansion over the melting point, wherein curve A is shifted to lower temperatures. From the graph it appears that the paraffines need not be liquid in the total temperature range wherein one wishes to be operative. It is however particularly preferred that the medium in the critical temperature range exclusively is present in liquid form. The graph further shows that a considerable expansion can be reached which for instance for paraffine B at 1 bar pressure in the range of 35 to 60°C amounts to about 16%.

In figure 2 a cross section of the hydrothermal generator with the regeneration cilinders and the connection to the (not shown) hydraulic motor is shown, wherein the principle of the invention is used. The high pressure part consists of an isolating regeneration cilinder 1, wherein parallel pressure pipes 3 are present, wherein the expansion medium 4 according to the invention like paraffine, is present. Preferably the amount of thermal medium for an efficient regeneration is of the same order as the amount expansion medium in the regeneration medium. The thermal medium, for instance water, is Indicated by 2. The pressure pipes 3 are connected through a branch pipe 5, a coupling 6 with isolation 7, through a plunger cilinder 8 wherein plunger 9 is present, to plunger cilinder

13. Plunger 9 is coupled to a piston 12 which is movable in cilinder 13. The plunger cilinder is fixed with a locking bolt 22 in an intermediate plate 18 and behind the locking bolt 11 labyrinth sealing rings are indicated. Cilinder 13 is connected to intermediate plates 18 and 19 by draw bolts. The cilinder 13 is in connection with an oil pipe 20. In the regeneration cilinder 20 also an input and output of thermal medium are present, which may be exchanged. 14 indicates the displacement piston or separation piston, which is slidable in the Isolating regeneration cilinder. This piston prevents that the amounts displaced thermal medium during run from the one to the other regeneration cilinder mutually could be intermingled. 23 indicates a differential which is controlling in turn the cycle valves 36 and 37.

Figure 3 shows the mutual arrangement of the regeneration cilinders in the cross section A-B of figure 2. The valve 36 is centrally present in the drawing, of which the position further will be illustrated in figure 5.

The action of the regeneration cycle will now be illustrated by figures 4a, 4b and 4c. In these figures cold water and hot water chambers are indicated with K and W, if water as thermal medium is used. At cold water chamber K dosiig pump 33 is arranged, which conveys by means of excentre 35 constantly water to the regeneration cilinder to be cooled with pressure pipes. The dosing pump is adjusted in such a way that it has in one stroke transported medium a volume that is substantially equal to or slightly more than the volume of the separate regeneration cilinders, of which five are drawn. 39 indicates a switch valve which reverses the flow direction of warm to cold and vice versa. With 34 recoil valves are shown.

In figure 4a water flows from the .hot water chamber 32 to the lower row of cilinders through the switch valve 39 to the cold water chamber 31. During the upwards movement of the plungerof the dosing of pump 33 (arrow 38) a fixed amount/liquid, in this case water, is transported through the recoil valve 34 to the upper row of cilinders. This amount is adjusted in such a way that the separation pistons 14 move from the upper position to the lower position respectively the lower position to the upper position, and thus this fixed amount of water is proceeded one regeneration cilinder. The same procedure is carried out in the reverse direction in the lowermost high pressure tank. In figure 4b. which shows the condition after termination of the step as indicated in figure 4a. wherein the valves 36 and 37 are exchanged as concerns position, the dosing pump is moving downwards (arrow 38) by which the same amount of water, such as in figure 4e. is displaced which now flows through the lowermost recoil valve 34 in the valve 39 in a reverse direction compared with figure 4a. After termination of the step the separation pistons are now in the same position as in figure 4a.

In figure 4c the same original position as in figure 4 is reached on the understanding that now the switch valve 39 is displaced, as indicated, by means of which the flow directions of the cold and warm water are reversed so that now the lower group becomes cold en de upper warm. The amount of water displaced by the dosing pump 33 now runs stepwise into the lower series of regeneration cilinders to the warm water chamber 32, while in the upper one the flow direction also is reversed and this group of cilinders is being heated. The reversion of the flow direction by displacement of the tact valve 39 may take place by electrical or mechanical means or other means, for instance by means of a signal released by the excentre.

The number of dosing strokes in each cycle is adjustable to be dependent on the situation as present, but it is understood that by

"stepwise" transfer of cold and warm medium between two extreme temperatures more dosing strokes are necessary. Good results are already reached with seven strokes before the other flow direction is switched on. The connections of the regeneration cilinders to the hydraulic engine in figures 4a, 4b and 4c are for the sake of clearness not indicated. In figure 5 the two positions of the valves 36 and 37 are shown in plan view. The positions of the valves 36 and 37 are always different, i.e. when valve 36 is switched over at the same time valve 37 Is switched over by means of differential 23.

In figure 6 finally the connection of the cilinders driven by the regeneration cilinders to the hydraulic engine are indicated. At two sides five cilinders act on the hydraulic chamber, by means of lines provided with valves 53, that on the one part are connected with a buffer 54, which works as a hydropneumatical accumulator and on the other part with lines 51 which are connected to the hydraulic engine through a valve 52. The pistons in the five cilinders are each drawn in a different position belonging to the temperature values in the separate cilinders, as agrees with the illustration for figures 4a, 4b and 4c. In the drawing further a reservoir 55 and a. by-pass-valve 56 are shown. Engine 50 which for example is the torus engine according to American Patent Specification 4,636,157 or any other hydraulic engine is driven into the direction of the arrow by a hydraulic medium.

In the table that follows as example the temperature course when five regeneration cilinders are thermally regenerated in seven strokes is shown. The cold water reservoir then has a temperature of 20°C and the hot water reservoir of 80°C. In the upper series heating takes place wherein always the adjusted amount of water in the upper series is displaced. One starts from the condition in equilibrium wherein the first cilinder calculated starting from the hot water reservoir has a temperature of 51,5°C and the last cilinder of 20,2°C. In the following occurring stroke water of 80°C is introduced in the cilinder with 51,5°C, water of 51,5°C is introduced in the second cilinder with 38°C etc. The temperature which is reached in each following cilinder is the medium value of the original temperature and the temperature of the amount of introduced water. In the preferred embodiment the contents of the expansion medium and the thermal medium in the regeneration cilinder are namely chosen as substantially equal. After seven days one then reaches the temperature equilibrium as indicated in the lower series. From this condition the flow direction is reversed and cooling takes place analoguously as mentioned for the heating. It follows clearly from this table that no unnecessary heat is lost by mixing of cold with very hot liquid. Indeed now final temperature of 80°C for all cilinders is reached but this is for a good operation of the generator not necessary. As follows from figure 6 the driving pistons of the hydraulic medium all take another endposition wherein equilibration takes place by the presence of the buffer medium.

TABLE.

Temperature course in regeneration cilinder (5, see figure 3). Warm: 80°C - Strokes: 7 - Cold: 20°C.

51,5 38,0 22,4 21,9 20,2

65,8 44,8 37,2 24,6 21,1

72,9 55,3 38,7 28,7 22,8

76,4 64,1 47,0 33,7 25,8

78,2 70,3 55,5 40,3 29,7 28,0

79,1 74,2 62,9 47,9 35,0

79,6 76,2 68,6 55,4 41,5

79,8 78,1 72,6 62,0 48,5

78,9 75,4 67,3 55,2 34,2

77,2 71,3 61,3 44,7 27,1

74,2 66,3 53,0 35,9 23,6 72,0 70,3 59,7 44,5 29,7 21,8

65,0 52,1 37,1 25,8 20,9

58,5 44,6 31,4 23,3 20,4 51,5 38,0 27,4 21,9 20,2

Claims

CLAIMS .

1. Process for conversion of thermal energy in mechanical energy by expansion of a non-gaseous medium which expansion is used for driving purposes or other purposes, which expansion medium is subjected to a temperature cycle, characterizes in that an inert, mainly liquid expansion medium is used which in a relatively low has temperature range of not higher than about 80°C an expansion | coefficient as high as possible of at least 5 vol.% which medium is contained in pressure pipes with such length-diameter ratio's that they can resist relatively high pressures. which pressure pipes are accomodated in a regeneration cilinder and which pressure pipes stepwise are heated or cooled by a thermal medium that circulates in the regeneration cilinder and between a cold reservoir and a hot reservoir without parts of the thermal medium with different temperatures mutually being intermingled.

2. Process according to claim 1, characterized in that the thermal medium stepwise is displaced in a dosed amount which is at least equal to the content of one regeneration cilinder from one regeneration cilinder to the other, wherein intermingling of thermal medium of different regeneration cilinders is prevented by providing separation pistons between the pressure pipes in the regeneration cilinder.

3. Process according to claims 1-2, characterized in that always two pressure groups with several regeneration cilinders stepwise are heated respectively cooled and after termination of one cycle the flow direction of the thermal medium is reversed.

4. Process according to claims 3, characterized in that at least five regeneration cilinders per group are present which each contain at least seven pressure pipes, which cilinders are connected in series in respect of the flow direction of the thermal medium.

5. Process according to claims 1-4, characterizes in that the regeneration cilinders with pressure pipes through an intermediary piston are connected parallel with respect to a buffer, which last is directly connected with the hydraulic motor to be driven or similar apparatus.

6. Process according to claims 1-5, characterized in that the amount of thermal medium in a regeneration cilinder at least is equal to the amount of expanding medium and preferably somewhat higher.

7. Process according to claims 1-6, characterized in that as expanding medium a long hydrocarbon which preferably is saturated, especially a paraffine, substituted products thereof, as well as fatty acids with at least ten carbon atoms and substituted products thereof, are used.

8. Process according to claim 7, characterized in that paraffines with expansion coefficients at atmospheric pressure of 10-20% in a temperature range of 20 to 80°C are used.

9. Hydrothermal generator for carrying out the process according to claims 1-8, characterized in that it comprises one or more pressure groups of regeneration cilinders (1) from isolating material, provided with several pressure pipes (3) filled with expanding medium (4), which pressure pipes (3) are surrounded by a thermal medium (2), which pressure pipes in the regeneration cilinder (1) are connected with a plunger cilinder (8) on which the pressure medium is acting, which plunger cilinder (8) further is connected to a driving mechanism, which regeneration cilinders (1) are connected in groups in series with respect to the flow direction of the thermal medium (2) but parallel with respect to the cold and hot reservoirs (31, 32), each regeneration cilinder (1) containing a separation piston (14) which prevents the intermingling of stepwise circulating thermal media with different temperatures, as well as a switch. valve (39) to revert the direction of the thermal cycle after each heating respectively cooling cycle.

10. Apparatus according to claim 9, characterized in that two or more pressure groups are connected in parallel between the hot and cold reservoirs but mutually are in series with respect to the circulating thermal medium by means of valve (39).

11. Apparatus according to claim 10, characterized in that five regeneration cilinders each containing seven pressure pipes are connected in the thermal cycle.

12. Apparatus according to claims 9-11, provided with a switch valve (39) and associated mechanism to reverse the cooling and heating cycles.

13. Apparatus according to claim 12, characterized in that two valves (36. 37) are provided which are connected in tact with a pump (33) and reverse the regeneration flow.

14. Apparatus according to claims 9-13, characterized in that the regeneration cilinder is arranged so that the amount of thermal medium is at least equal to or slightly higher than the amount of thermal medium present in the pressure pipes.