A working mechanism device in a heat engine and, if the device is substantially arranged for reversed functions, in a heat pump is described, the working mechanism including at least one variable-volume chamber defined by a displacement device and provided with at least one working- fluid inlet, and at least one heat exchanger which is in thermal contact with the variable-volume chamber by way of at least one heat- exchanger surface .

A method for heat exchange in a heat engine and, when the method is substantially reversed, in a heat pump is described as well, the heat engine including a working-fluid circuit, a thermo fluid circuit and at least one working mechanism.

There are many heat-engine technologies that utilize heat supplied from an external heat source, so-called external - heat engines, as opposed to internal -combustion engines, in which heat is supplied in consequence of the internal combustion of a fuel. All heat engines utilize a working fluid, and in an external-heat engine the heat is supplied to the working fluid through a heat exchanger. An example of an external-heat engine is the Stirling engine.

Precisely because all the heat that is converted in an external -heat engine is to be transferred by means of one or more heat exchangers, the design thereof is one of the most important factors to achieve an efficient construction. To bring about good heat exchange in a heat engine, it is important to achieve a high heat transmission coefficient between the working fluid and the heat exchanger. Similarly, it is important to achieve a high heat transmission

coefficient between the heat transmission fluid, called the thermo fluid hereinafter, and the heat exchanger, so that the total heat transmission coefficient between the thermo fluid and the working fluid will be high. The thermo fluid is the fluid that transports the heat between the heat engine and an external heat or cold reservoir and may, in the simplest case, be air, water or exhaust gas. As a rule, the heat exchanger will separate the two fluids from each other, as the heat exchanger generally forms a mechanical barrier between the two.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art .

The object is achieved through features which are specified in the description below and in the claims that follow.

To achieve high heat transmission it is important, among other things, that the working fluid has access, at all times, to a largest possible portion of the internal surface of the heat exchanger, that is to say the side that is in thermal contact with the variable-volume chamber, typically a cylinder chamber. In many existing Stirling engines, for example, it is not possible to have a constantly large heat- exchanger surface, as it is precisely the cylinder walls that also function as a heat -exchanger surface and, as it is known, the cylinder is periodically covered by the piston, which oscillates inside the cylinder. To circumvent this current problem, it is possible to have an oblong piston, for example, so that it may still displace the working fluid in nearly the entire volume of the cylinder, but in addition, a diametrical narrowing or widening may be made in a portion of the piston or cylinder wall,

respectively, so that a gap is formed, within which the working fluid may still flow in towards the entire heat- exchanger surface at all times. Figure la shows a way of implementing this, in which the radius of the piston is restricted in the upper portion thereof, so that a gap is formed between the piston and the cylinder, and fluid

communication between the working- fluid inlet and the heat- exchanger surface is maintained at all times. In this way it is ensured that the entire heat -exchanger surface is always accessible during the injection of working fluid and, thus, maximum heat transmission can therefore be achieved at all times .

In order further to provide for a largest possible portion of the injected working fluid to immediately get into contact with a largest possible portion of the heat -exchanger

surface, the working fluid may be injected simultaneously in several places, for example by several discharge points for working fluid being provided on the working- fluid inlet. This is shown in figures 4b and 5b.

In order to increase further the portions of working fluid that are simultaneously brought into contact with the heat- exchanger surface, several working- fluid inlets may be arranged in the variable-volume chamber. Figures 2a-2e, 3a- 3e, and 4a and 5a show embodiments with several working- fluid inlets, shown as pipes placed axially within the cylinder, cavities having been made in the piston to accommodate them without them creating much dead volume, that is volume that cannot be displaced by the piston.

To increase the heat-exchanger surfaces further, a further internal heat exchanger may be arranged in addition to a first internal heat exchanger. The figures 3a-3e show an implementation of a working mechanism with two internal heat exchangers. A first heat exchanger surrounds the cylinder chamber, whereas a second heat exchanger is surrounded by the cylinder chamber. There may also be more heat exchangers. In this example, the piston is formed with displacement

elements, in addition to gaps for working- fluid inlet, so that the dead volume is minimized, and a largest possible portion of the cylinder volume may still be displaced during operation, in spite of the presence of the second heat exchanger .

The direction of injection of the working fluid can also be controlled by inclining the directions of the discharge points of the working- fluid inlets, so that a cyclonic flow motion may be created as the working fluid is injected. This is shown in figures 4a and 4b. Other directions of flow may also be encouraged as required, by manipulating the

directions and the geometries of the discharge points.

In addition to the above-mentioned measures to increase the heat transmission, provisions may be made for the heat engine to work under the two-phase principle, wherein the working fluid alternates between the liquid phase and the gas phase, as, for example, in a steam engine, that is to say. Because the heat transmission between an evaporating fluid and a heat-exchanger wall will normally be considerably higher than the heat transmission between a pure gas and a heat

exchanger, it may be an advantage in heat engines in general precisely to make use of the two-phase principle. This, in turn, may be instrumental in increasing the heat transmission in the engine .

In a first aspect, the invention relates, more specifically, to a working mechanism device in a heat engine and, if the device is substantially arranged for reversed functions, in a heat pump, the working mechanism including at least one variable-volume chamber defined by a displacement device and being provided with at least one working-fluid inlet and at least one heat exchanger which is in thermal contact with the variable-volume chamber, characterized by the at least one heat exchanger completely or partially surrounding or being surrounded by the variable -volume chamber, and by one or more of the elements taken from the group consisting of the displacement device, a work housing and a heat exchanger, which surrounds or is surrounded by a portion of the

variable-volume chamber, being provided with means forming fluid flow passages in the form of gaps, recesses and/or cavities arranged to provide fluid communication between each and all of the at least one heat exchanger, the working- fluid inlet and the variable -volume chamber in every one of the positions of the displacement device in the variable-volume chamber .

The working mechanism may be provided with one or more fluid passages formed by at least a narrowing in an upper portion of the displacement device, the fluid passage enclosing or being enclosed by a substantial part of the axial extent of the at least one heat exchanger when the displacement device is at a top dead centre, in order thereby to provide thermal contact between the working fluid and substantially the entire heat -exchanger surface of the at least one heat exchanger .

The working- fluid inlet may be provided with one or more discharge openings. The working- fluid inlet may be formed by at least one fluid inlet pipe extending in the direction of translatory movement of the displacement device.

The discharge opening (s) may be arranged orthogonally to the longitudinal direction of the at least one fluid inlet pipe.

The discharge openings may be distributed over one or more columns in the longitudinal direction of the at least one fluid inlet pipe.

The discharge openings may be arranged to provide a direction of outflow for the working fluid substantially tangentially to the heat -exchanger surface of an adjacent heat exchanger.

The displacement device may be provided with one or more recesses which are arranged to accommodate a portion of a fluid inlet pipe.

The displacement device may be provided with a cavity which is arranged to accommodate at least a portion of the second heat exchanger.

In a second aspect, the invention relates more specifically to a method for heat exchange in a heat engine and, when the method is substantially reversed, in a heat pump, the heat engine including a working-fluid circuit, a thermo fluid circuit and at least one working mechanism, the working mechanism including at least one variable-volume chamber defined by a displacement device, and the variable -volume chamber being provided with at least one working- fluid inlet, each including at least one discharge opening; and at least one heat exchanger being provided with at least one heat- exchanger surface which is in thermal contact with the variable-volume chamber, characterized by the method

including the following steps: a) passing a fluid flow of a thermo fluid through at least one heat exchanger;

b) passing, at the same time, a working fluid into the variable-volume chamber via the at least one discharge opening;

c) bringing the working fluid into thermal contact with the entire heat-exchanger surface of the heat exchanger that is exposed towards the variable-volume chamber, fluid

communication between each and all of the heat exchanger, the working-fluid inlet and the variable-volume chamber being maintained in every one of the work phases of the working mechanism; and

d) letting the thermo fluid give off heat to the working fluid through the heat exchanger.

The at least one heat exchanger may be arranged in a volume surrounding or being surrounded by the variable -volume chamber, the heat exchanger surrounding or being surrounded by at least a portion of the variable-volume chamber as well.

The working fluid may be carried into the variable-volume chamber through at least one fluid inlet pipe.

The working fluid may be carried into the variable-volume chamber through at least one fluid discharge opening in the at least one fluid inlet pipe.

The working fluid may be carried into the variable-volume chamber through several discharge openings distributed across a substantial portion of the longitudinal extent of the at least one fluid inlet pipe.

The direction of outflow of the working fluid from the at least one discharge opening may bring about a fluid flow substantially orthogonally to the axial direction of the variable-volume chamber and substantially tangentially to the surface of the heat exchanger.

The working fluid may alternate between the liquid and gas phases .

In what follows, an example of a preferred embodiment is described, which is visualized in the accompanying drawings, in which:

Figure 1 shows, in a side view, a principle drawing of a

working mechanism according to the invention, in which a fluid communication between a fluid inlet, a variable-volume chamber and a heat exchanger is maintained by a gap being formed between a piston and the heat exchanger by an upper portion of the piston being radially narrowed;

Figure 2a shows, in a side view, a principle drawing of an alternative exemplary embodiment of the working mechanism, in which fluid communication between the fluid inlet, the variable-volume chamber and the heat exchanger is maintained by said gap between the piston and the heat exchanger being formed by the upper portion of the piston being radially narrowed, and in which the fluid inlet is formed by pipes arranged axially at the cylinder wall of the variable-volume chamber, and in which corresponding recesses are formed in the side wall of the piston to accommodate the pipes;

Figure 2b shows a plan of the piston according to figure 2a;

Figure 2c shows, in a side view, a principle drawing of the working mechanism according to figure 2a with the piston in an upper position; Figure 2d shows a radial section through a portion of the variable-volume chamber with the piston and the fluid inlet pipes in the working mechanism according to figure 2a;

Figure 2e shows the piston and parts of the fluid inlet pipes as in figure 2a, seen from the side;

Figure 3a shows a principle exemplary embodiment of the

invention, in which fluid communication between the fluid inlet, the variable-volume chamber and first and second heat exchangers is maintained by a gap between the piston and the heat exchangers being formed by the upper portion of the piston being narrowed radially, the fluid inlet being formed by four pipes installed axially and recesses having been formed in the piston to accommodate the pipes in an operating state, and by a larger cavity having been formed in the upper end surface of the piston to accommodate the second heat exchanger;

Figure 3b shows a plan of the piston of figure 3a;

Figure 3c shows a side view of the working mechanism

according to figure 3a with the piston in an upper position;

Figure 3d shows a radial section of the piston and the fluid inlet pipes of figure 3a; gure 3e shows a side view of the piston and parts of the fluid inlet pipes of figure 3a;

Figure 4a shows, on a larger scale, a radial section through a portion of the variable-volume chamber with the piston and the fluid inlet pipes corresponding to the configuration of figure 2a, discharge openings being arranged to provide a flow direction of the working fluid along the periphery of the piston, and all the discharge openings having the same direction;

Figure 4b shows a side view of a fluid inlet pipe according to figure 4a, in which a row of discharge points arranged in the axial direction of the fluid inlet pipe is shown;

Figure 5a shows a radial section through a portion of the

variable-volume chamber with the piston and the fluid inlet pipes corresponding to the

configuration of figure 3a, the discharge points being arranged and distributed to provide an even flow of working fluid towards a largest possible portion of the heat-exchanger surfaces;

Figure 5b shows a side view of a fluid inlet pipe according to figure 5a, in which two rows of discharge points arranged in the axial direction of the fluid inlet pipe are shown; and

Figure 6 shows a fluid inlet pipe with only one discharge point .

What is described below may also be applicable to a heat pump, in which the processes that have been described are substantially the opposite of what applies to a working mechanism 1. If nothing else is mentioned, the concept of "heat engine" also covers a heat pump according to the invention .

In the figures, the reference numeral 1 indicates a working mechanism including a work housing 100, shown here as a cylinder, which, together with a displacement device 200, also called a piston, forms a variable-volume chamber 150, also called a working chamber. A translational movement carried out by the piston 200 is converted via an associated connecting rod 60 into a rotational motion on a crank shaft 50. At a lower portion 202, the piston 200 is provided with piston seals 205 which provide the necessary fluid seal between the piston 200 and the work housing 100 during operation, for example ordinary piston springs.

In the schematic principle drawings in figures 1, 2a, 2c, 3a and 3c, the symbol "m" indicates an amount of working fluid circulating in the working mechanism 1, whereas Q _v , Q _v i and Qv2 represent the heat which is being supplied to a heat exchanger 300 or first and second heat exchangers 300a, 300b by a thermo fluid giving off heat. The heat exchangers 300, 300a and 300b provide for heat supply to the working fluid during expansion or heat removal from the working fluid during compression, the heat exchangers 300, 300a, 300b being provided with one or more heat-exchanger surfaces 301 which are exposed towards the variable-volume chamber 150.

Reference is first made to figure 1, in which a working mechanism 1 is provided with one heat exchanger 300 which is in thermal contact with the working chamber 150 as it

surrounds a portion of the working chamber 150. An upper portion 203 of the piston 200 has a reduced diameter, forming an annulus- shaped gap 110 enabling working- fluid passage between the piston 200 and the internal wall surface of the work housing 100, the heat-exchanger surface 301 of the heat exchanger 300, that is, which leads to improved heat exchange between the working fluid and the heat exchanger 300

surrounding the upper part of the working chamber 150 when the piston 200 is in a position completely or partially surrounded by the heat exchanger 300.

Reference is then made to figures 2a-2e, in which the upper piston portion 203 also includes several piston recesses 210 in the periphery of the piston 200. Each of the piston recesses 210 is arranged to accommodate a fluid inlet pipe

401 extending downwards from an upper portion 151 of the working chamber 150, forming the working- fluid inlet 400.

Each fluid inlet pipe 401 may be provided with one or more discharge openings 402 (see figures 4a-6) which are

positioned in such a way that a favourable direction of flow into the working chamber 150 is achieved. Figures 4a and 4b show an embodiment in which a number of discharge openings

402 arranged in the longitudinal direction of the fluid inlet pipe 401 direct the working- fluid flow in a circumferential direction along the wall surface of the work housing 100. In the figures 5a and 5b several rows of discharge openings 402 are shown. In figure 6 a fluid inlet pipe 401 with only one discharge opening 402 is shown.

In an alternative embodiment, as it is shown in the figures 3a-3e, the working mechanism 1 is provided with first and second heat exchangers 300a, 300b, the first heat exchanger 300a corresponding to the heat exchanger 300 described above. The piston 200 is provided with a piston cavity 211 extending downwards towards the lower piston portion 202. Together with the piston recesses 210 arranged to accommodate the fluid inlet pipes 400, the piston cavity 211 forms displacement elements 201 extending up from the periphery of the lower portion 202 of the piston 200.

The piston cavity 211 is arranged to accommodate and surround a second heat exchanger 300b projecting downwards from the upper portion 151 of the working chamber 150. The second heat exchanger 300b may have a cylindrical shape, for example, or consist of sections projecting freely downwards. A wide variety of other shapes is also relevant and is not limiting to the invention.

In this embodiment, fluid communication is maintained between both heat exchangers 300a, 300b, the fluid inlet pipe 401 of the working-fluid inlet 400 and the working chamber 150, independently of the work position of the piston 200. In figure 3a, the gap 110 is formed by the upper portion of the piston 200 having external and internal diameters

respectively different from the external diameter of,

respectively, the working chamber 150 and the second heat exchanger 300b, so that clearances are formed, in which the working fluid may flow.

In an operating state, the working fluid will be injected through the working-fluid inlet 400 which, for the exemplary embodiments shown in figures 2a-3e, is constituted by the fluid inlet pipes 401 and, according to the figures 4a-6, is constituted by the discharge openings 402 of the fluid inlet pipes 401, from the piston 200 is approximately in its top position and while it is moving down towards the bottom position. Because of the gap 110, the working fluid may freely enter the working chamber 150 and, at the same time, get into contact with the entire heat-exchanger surfaces 301 of the heat exchangers 300, 300a, 300b, independently of where the piston 200 is within the cylinder 100. As it is shown in figure 5a, the discharge openings 402 are directed towards both the first and second heat exchangers 300a, 300b, so that a largest possible portion of the working fluid is distributed across a largest possible heat-exchanger surface at all times during injection.

The piston 200 is surrounded by the first heat exchanger 300a when the piston 200 is in an upper position; see for example figures 2c and 3c. The fluid inlet pipe 401 of the working- fluid inlet 400 is substantially surrounded by the piston 200 when the piston 200 is in an upper position; see figures 2d and 2e. In addition, figure 3c shows how the second heat exchanger 300b is surrounded by the piston 200.

When the working mechanism 1 is in function, the following is carried out :

a) In a first process, a thermo fluid flow is conveyed

through at least one internal heat exchanger 300, 300a, 300b which is in thermal contact with the variable- volume chamber 150.

b) In a second, concurrent process, a working fluid is

carried into the variable-volume chamber 150 via the working- fluid inlet 400 and is brought into thermal contact with the entire internal surface of the heat exchanger (s) 300, 300a, 300b, as fluid communication is maintained between the heat exchanger (s) , the working- fluid inlet 400 and the variable-volume chamber 150 in all positions of the piston 200.

c) In a third, concurrent process the thermo fluid lets heat be given off to the working fluid through the heat exchanger (s) 300, 300a, 300b.