WO1982000858A1

WO1982000858A1 - A method and apparatus for compressing a gaseous medium

Info

Publication number: WO1982000858A1
Application number: PCT/SE1981/000245
Authority: WO
Inventors: B Frostenson
Original assignee: B Frostenson
Priority date: 1980-09-02
Filing date: 1981-09-01
Publication date: 1982-03-18
Also published as: SE8006128L; EP0065955A1

Abstract

Method of compressing a gaseous medium, and an apparatus for carrying out the method. The compression occurs spontaneously, in as far as no energy needs to be supplied, and is provided by utilization of means effective velocity differences arising in the molecules/ atoms of a gaseous medium in spaces (1) in gaseous communication. The velocity differences are caused by differences in energy gain at molecular/atomic level, which are provided by differences in surface nature and/or by arranging minor spaces (4) in or at preferably defining walls (4, 5) of the spaces. The differences in energy gain are utilized such that the velocity of the molecules/atoms will be higher where they enter the spaces (1) than where they exit from said spaces. A pressure gradient thereby arises, causing a now of the gaseous medium from a low pressure to a higher pressure. The apparatus comprises parallel, perforated or porous plates or laminae (5, 7) enclosed preferably in a cylinder (6) at right-angles to the longitudinal direction thereof or of cavitites or pores incorporated in porous plates between and preferably adjacent the plates (5, 7).

Description

A Method and Apparatus for Compressing a Gaseous Medium.

The present invention relates to a method of compressing a gaseous medium, by utilizing mean effective velocity differences occurring in the molecules/ atoms in a gaseous medium present in spaces in gaseous communication. The invention also relates to apparatus for carrying out the method.

The velocity differences mentioned, and the compression consequent thereon, occur spontaneously in as far as no energy needs to be supplied, e.g. signifying that by utilizing the pressure difference occur ing for generating mechanical energy, the conversion of thermal energy into macroscopic kinetic energy may be substantially completely enabled, irrespective of the degree of the thermal energy density.

The invention thus relates to a method of compressing a gaseous medium by utilizing the mean effective velocity differences occurring in the molecules/ atoms of a gaseous medium, to be found in spaces in gaseous communication, said spaces preferably being arranged in series, where said velocity differences are caused by the differences in energy gain at a molecular/ atomic level, more specifically, mainly differences in effect in respect of velocity and velocity distribution of the molecules/atoms in the gaseous medium between the latter and preferably the walls defining the spaces, said differences being in turn generated by the surface nature (such as porosity, molecular/atomic composition and their structure) of the defining walls being made different for different surfaces and/or by one or more minor spaces being arranged at preferably one or more of the defining walls. The method is distinguished in that the mean effective velocity of the molecules/atoms in the respective space is caused to become higher within the areas at or in the vicinity of the places where the molecules/ /atoms are caused to enter into the space than within the areas at and/or in the vicinity of the places where the molecules/atoms are caused to exit from the place and that this is provided by a difference in surface nature corresponding to the abovementioned being caused to occur between the surfaces within the former areas on the one hand, and the surfaces within the latter areas on the other hand, and/or by the abovementioned minor spaces being arranged within one or more of these areas and that the pressure gradient generated by said measures is caused to achieve a flow of the gaseous medium from a state of low pressure to one of higher pressure.

The invention also relates to an apparatus for compressing a gaseous medium, where the mean effective velocity differences are utilized, which occur in the molecules/atoms of a gaseous medium in gas-communicating spaces, preferably arranged in series, and where said differences are caused by differences in energy gain at a molecular/atomic level between the gaseous medium and preferably the defining walls of the chambers, and where different energy gains are intended to be provided by the surface nature (such as porosity, molecular/atomic composition, and structure) of the defining walls being made dissimilar for different surfaces and/or by one or more minor spaces being provided, preferably at one or more of said walls, and where the mean effective velocity of the molecules/atoms is intended to be higher in the respective space within the areas at and/or in the vicinity of the places where the molecules/atoms are intended to enter the chamber than within the areas at and/or in the vicinity of the places where the molecules/atoms are intended to exit from the space, and where this is intended to be provided by a difference in surface nature corresponding to those mentioned above, beingcaused to occur between the surfaces within the former areas on one hand, and the surfaces within the latter areas on the other, and/or by said minor spaces being arranged within one or more of these areas, and where the pressure gradient generated by said measures is intended to achieve a flow of the gaseous medium from a state of low pressure to one of higher pressure.

The apparatus is distinguished in that the spaces are intended to be formed between, - with regard to the molecules/atoms of the gaseous material, - partially permeable plates or laminae, such as porous plates or perforated solid plates, and preferably a cylinder with its longitudinal extension perpendicular to the plane of the plates or laminae and in that a gaseous medium at a low pressure is intended to be supplied to the spaces at one end thereof, and a gaseous medium at a higher pressure removed from the spaces at the other end.

The effective mean velocity is equal to the mean velocity of that of the molecules/atoms which passes a given cross section during a given time.

The basis in physics on which the method and apparatus in accordance with the invention relies will now be stated, in the form of a discussion in conjunction with a couple of simple figures and calculations. After this discussion there follows a description of the invention. The discussion and description are carried out in conjunction with the appended drawings, where

Figures 1a and 1b illustrate a gaseous medium where there are greater velocity variations between the individual molecules/atoms in Figure 1a than in Figure 1b, Figure 2 is a section through a schematically illustrated apparatus in accordance with the invention, Figure 3 illustrates one inventive embodiment and Figures 4a - d illustrate different surface natures and minor spaces.

Velocity differences prevail between the individual molecules/atoms in a gaseous medium. If the maiority of molecule/atom collisions are allowed to occur in common between the molecules/atoms a particular velocity spread will be obtained. If, instead, the molecules/ /atoms are allowed to collide to a relatively large extent with a solid material, for example, a different velocity spread is obtained.

The relationship between the number of collisions in common and the number of collisions with the solid material is dependent on the relationship between the mean free path of the molecules/atoms and the dis- tance between the walls of the container enclosing the gaseous medium. The porosity of the solid material surface also affects the relationship, since a porous surface results in that for each contact with the surface the molecules/atoms collide on an average more than once with the solid material.

In the case of relatively many collisions with the solid material, the surface nature thereof noticeably affects the velocity distribution. If the velocity of the molecules/atoms is changed to a small extent at the individual collisions with the solid material, the statistic probability of great velocity differences between the individual molecules/atoms will be small, and vice versa.

In the study of the energy gain for a gaseous medium in contact with a solid surface it has been found expedient to define a coefficient a, the accommodation coefficient, according to where

T₀ = Gas temperature before contact or collision with the surface T₁ = Surface temperature

T₂ = Gas temperature after contact or collision with the surface.

See, for example, A.H.Beck, "Handbook of vacuum physics". Vol. 1, 3.1, p 280-281, (particularly: "It has been pointed out ....") and 3.8 - 3.9, p 292-297. a=0 corresponds to slight effect, i.e. T₂=T₀, and a=1 corresponds to great effect, i.e. T₂= T₁. For a given material and a given structure of its surface, a varies for different gases and for the temperatures T₀ and T₁ , and vice versa. In the following, the porosity of the surface structure is not included in a, however, i.e. with a is intended here the effect at each individual collision with the solid material, and not the collected effects of more than one collision. In consequence of the attraction forces between the solid material and the molecules/atomes, a=1 presumably gives rise to greater velocity spread than mutual collisions.

If a gaseous medium enclosed in a container is separated into two parts by means of a wall, and if the wall is provided with a hole, which is small in relation to the mean free path and the s i ze of the spaces, the pressure relationships between the spaces will depend on how, in the respective spacer, the mean effective velocities of the molecules/atoms at and/or in the vicinity of the hole compare with each other. Higher mean effective velocity gives higher pressure and vice versa.

The basis of this state of dependence is that, for a no-flow condition, the same number of molecules/ atomes must pass through the hole in one direction as in the other, and thereby collide with the walls just as many times in one space as in the other, which means that the pressure will be higher in the space with a higher mean effective velocity of the molecules/atoms at and/or in the vicinity of the hole.

In Figure 1a, alternate molecules/atoms which collide with the solid material have a velocity of 4y m/s, corresponding to a temperature of 16x Kelvin, the others having a velocity of 2y m/s, corresponding to a temperature of 4x Kelvin. The mean effective velocity is then 3y m/s, since the temperature lOx Kelvin of the solid material lies midway between the temperatures to which the velocities^'of the molecules/atoms correspond, temperature equilibrium prevails between the solid material and the gaseous medium in which the molecules/atoms are included.

In Figure 1b, all the corresponding molecules/ /atoms have the velocity 3,16y in/s, corresponding to the temperature of 10x Kelvin, which gives a mean effect- ive velocity of 3,16y m/s. Since the solid material has a temperature of 10x Kelvin, temperature equilibrium also prevails.

The mean effective velocity will thus be higher for uniform velocity distribution than for non-uniform velocity distribution.

In Figure 2, a cylinder is denoted by the numeral 6. It is filled with a gaseous medium and provided with a plurality of discs or laminar 5, permeable in relation to the molecules/atoms, said discs being disposed mutually parallel with a given spacing and at right-angles to the longitudinal extension of the cylinder. The discs 5 are either solid perforated plates or porous plates where the porosity corresponds to said perforations. Neither porosity nor holes are shown in the Figures. The left-hand and right-hand faces of the discs have mutually differing surface properties (not shown in the Figures) in respect of porosity and/or minor spaces.

In Figure 3 there is illustrated an embodiment of the inventive apparatus, where minor spaces 4 are formed between parallel discs or laminae 5 and 7 , discs 7 having greater permeability than discs 5, discs 5 and 7 being either solid, perforated plates or porous plates.

It is naturally not only the surfaces of the defining walls which may have different properties, but also other surfaces adjoining and/or in the vicinity of the holes.

In another embodiment, the gaps or spaces 1 between the plates 5 , as well as the minor spaces 4 between the plates 5 and 7 comprise communicating cavi ties or pores in greatly porous plates or laminae. The plates and the porous surface coating in this embodiment have, starting from the greatest, the following order in respect of the greatness of porosity: The spaces 1 between the plates 5, the minor spaces 4 between the plates 5 and 7, the porous surface coatings, plates 7 with greater permeability and plates 5 with less permeability.

The function of the different inventive embodiments is as follows. The method in accordance with the invention should also be apparent from this description. Since the surface properties of the defining walls of the spaces shown in Figure 2, for example, are such that the molecules/atoms leaving the right-hand faces of the walls have a greater mean velocity than the molecules/atoms leaving the left-hand faces thereof, and since at least a portion of the molecules/atoms collide with molecules/atoms coming from the opposite direction before they reach the opposite wall, the mean effective velocity will be higher for the molecules/ atoms at and in the vicinity of the right-hand faces of the walls and their associated holes than for those at, and in the vicinity of the left-hand faces of the walls, which, according to the previous discussion, results in that the gaseous medium exerts a higher pressure in the spaces to the right than in those to the left.

Providing that the higher pressure to the right of the spaces is not too high in relation to the low pressure to the left of the spaces, the pressure differences give rise to a flow of the gaseous medium from a state of low pressure to a state of higher pressure. It will be seen from Figures 4a - d how the velocity spread, and thereby the mean effective velocity differences may be varied with the aid of different surface properties and small spaces. The dots in Figures 4b - c indicate that there are relatively many mutual molecular/atomic collisions. In Figure 4a, the material with a=0 has a dominating effect on the velocity spread, which is thus small. In Figure 4b the mutual collisions have a dominating effect on the velocity spread, which is thus relatively large. In Figure 4c the material with a = 1 has a dominating effect on the velocity spread, which is thus large. In Figure 4d the material with a=1 has an even more dominating effect on the velocity spread, which is thus even greater. The porous surfaces and minor spaces give a a. dominating effect, since for each contact with the surface the individual molecules/atoms collide on an average more than once with the solid material.

The different surface properties and minor spaces may naturally be combined in a plurality of ways. As indicated in the introduction, the apparatus may be combined with a turbine or the like, in as much as the compressed gaseous medium is utilized to drive it. Accordingly, thermal energy may be converted to macroscopic kinetic energy. The gaseous medium cooled thereby may naturally be utilized for cooling purposes. The invention, as will have been understood, is not to be regarded as restricted to the above-mentioned embodiments, but may be varied within the scope of the appended claims without departing from the inventive concept.

Claims

CLAIMS 1. A method of compressing a gaseous medium by utilizing the mean effective velocity differences occurring in the molecules/atoms of a gaseous medium, to be found in spaces in gaseous communication, said spaces preferably being arranged in series, where said velocity differences are caused by the differences in energy gain at a molecular/atomic level, more specifically, mainly differences in effect in respect of velocity and velocity distribution of the molecules/atoms in the gaseous medium between the. latter and preferably the walls defining the spaces, said differences being in turn generated by the surface nature (such as porosity, molecular/atomic composition and their structure) of the defining walls being made different for different surfaces and/or by one or more minor spaces being arranged at preferably one or more of the defining walls, c ha r a c t e r i z e d .in that the mean effective velocity of the molecules/atoms in the respective space (1) is caused to become higher within the areas at or in the vicinity of the places where the molecules/ atoms are caused to enter into the space (1 ) than within the areas at and/or in the vicinity of the places where the molecules/atoms are caused to exit from the space (1) and that this is provided by a difference in surface nature corresponding to the above-mentioned being caused to occur between the surfaces within the former areas on the one hand, and the surfaces within the latter areas on the other hand, and/or by the above- mentioned minor spaces (4) being arranged within one or more of these areas and that the pressure gradient generated by said measures is caused to achieve a flow of the gaseous medium from a state of low pressure to one of higher pressure.

2. Method as claimed in claim 1, c h a r a c t e r i z e d in that the spaces (1) are formed between plates or laminae (5) which are partially permeable in relation to the molecules/atoms of the gaseous medium, e.g. porous plates or perforated, solid plates, and preferably a cylinder, the longitudinal extension of which is at right-angles to the planes of the plates, in that a gaseous medium at low pressure is supplied to the spaces (1) at one end of said spaces, and in that a gaseous medium at a higher pressure is removed from the spaces (1) at the other end.

3. Method as claimed in claim 1 or 2, c h a r a c t e r i z e d in that said minor spaces (4) in respective space (1) are provided in that, in relation to the remaining space, one or more minor spaces (4) are partially partioned off from the remaining space by a wall (7), to a certain extent permeable to the molecules/atoms of the gaseous medium, being disposed parallel to, and in the vicinity of one or more of the defining walls (5), which contain the previously mentioned areas.

4. Method as claimed in claim 1, 2 or 3, c h a r a c t e r i z e d in that the spaces (1, 4) between the plates (5, 7) are caused to be constituted by cavities or pores incorporated in porous plates or laminae.

5. Apparatus for compressing a gaseous medium, where the mean effective velocity differences are utilized, which occur in the molecules/atoms of a gaseous medium in gas-communicating spaces, preferably arranged in series, and where said differences are caused by differences in energy gain at a molecular/atomic level between the gaseous medium and preferably the defining walls of the space, and where different energy gains are intended to be provided by the surface nature (such as porosity, molecular/atomic composition, and structure) of the defining walls being made dissimilar for different surfaces and/or by one or more minor spaces being provided, preferably at one or more of said walls, and where the mean effective velocity of the molecules/atoms is intended to be higher in the respective space within the areas at and/or in the vicinity of the places where the molecules/atoms are intended to enter the space than within the areas at and/or in the vicinity of the places where the molecules/atoms are intended to exit from the space, and where this is intended to be provided by a difference in surface nature corresponding to those mentioned above beingcaused to occur between the surfaces within the former areas on one hand, and the surfaces within the latter areas on the other, and/or by said minor spaces being arranged within one or more of these areas, and where the pressure gradient generated by said measures is intended to achieve a flow of the gaseous medium from a state of low pressure to one of higher pressure, c h a r a c t e r i z e d in that the spaces (1) are intended to be formed between, - with regard to the molecules/atoms of. the gaseous material, - partially permeable plates or laminae (5), such as porous plates or perforated solid plates, and preferably a cylinder (6) with its longitudinal extension perpendicular to the plane of the plates or laminae (5) and in that a gaseous medium at a low pressure is intended to be supplied to the spaces (1) at one end thereof, and a gaseous medium at a higher pressure removed from the spaces (1) at the other end.

6. Apparatus as claimed in claim 5, c h a r a c t e r i z e d in that said minor spaces (4) are intended to be formed between one or more of the defining walls (5) containing said areas, and walls (7) in the vicinity of these walls (5), parallel thereto and to a certain extent permeable with respect to the molecules/atoms of the gaseous medium, and preferably said cylinder (6) .

7. Apparatus as claimed in claim 5 or 6, c h a r a c t e r i z e d in that the spaces (1 , 4) between the laminae (5, 7) comprise pores or cavities in porous plates or laminae.