US20100263392A1

US20100263392A1 - Refrigerator

Info

Publication number: US20100263392A1
Application number: US12/681,489
Authority: US
Inventors: Jürgen K. Misselhorn
Original assignee: Maschinenwerk Misselhorn MWM GmbH
Current assignee: Maschinenwerk Misselhorn MWM GmbH
Priority date: 2007-10-05
Filing date: 2008-10-06
Publication date: 2010-10-21
Also published as: EP2212627A1; WO2009046953A1; DE102007047642B4; DE102007047642A1

Abstract

A refrigerator is disclosed that consists in contrast to conventional refrigerators of a number of heat exchangers that are separated into halves, in which the same refrigeration cycle process takes place simultaneously but chronologically displaced, and wherein all heat exchangers are driven the same compressor. A cold medium flows about one half of the heat exchanger (evaporator) at certain time periods, a hot medium flows about the other half of the heat exchanger (condenser).

The refrigeration cycle process consists of six changes of state: isochoric heat input, isothermal expansion, isobaric condensation, isochoric heat extraction, isothermal compression and isobaric evaporation.

In the disclosed embodiment, the compressor is a double acting piston compressor establishing a connection to the heat exchangers via valves on both sides of the piston at predefined points in time within a cycle period. The piston is driven by a linear motor or by a crank shaft and a piston rod. While the working gas is compressed on one side of the piston, the working gas is sucked out of a different heat exchanger on the other side. It should be noted, that other types of compressors may also be employed.

Due to the six changes of state that are put into effect by this machine, a new cycle process is established which realizes a higher degree of efficiency (coefficient of performance) than conventional refrigerators or heat pumps.

Description

TECHNICAL FIELD

The present invention relates to a refrigerator that functions according to the principle of a cyclic process having six changes of state: two isochors, two isobars, two isotherms.
In this refrigerator several of the above mentioned refrigeration processes take place simultaneously but chronologically displaced. The changes of state, expansion and compression of the individual cycles are effected by a common refrigeration compressor.

BACKGROUND ART

For cooling purposes and as heat pumps different refrigerating processes are applied, which are briefly described in the following:

Cold Air Machine (Reversed Joule Process)

In this process air at ambient temperature is drawn in and isentropically compressed. Afterwards the adiabatically heated air is cooled isobarically and is subsequently expanded isentropically. Eventually the air is heated isobarically. This process is predominantly applied in aircraft air conditioning as well as in mining ventilation.

Philips Gas Refrigerator (Reversed Stirling Process)

This closed process is predominantly applied in the condensation of air and other gases. The theoretical process consists of the following changes of state:

- isothermal compression in compression chamber
- isochoric heat dissipation in regenerator
- isothermal expansion in expansion chamber
- isochoric heat addition in regenerator

Vapor Refrigerator (Plank Process)

This process is applied in different variants in the general refrigeration technology of refrigerators, refrigeration chambers, cold water generation etc. The theoretical process consists in general of the following changes in state:

- isentropic compression via a compressor
- isobaric (as well as isothermal) heat dissipation in a condenser
- isenthalpic expansion via throttling by an expansion valve or a capillary tube
- isobaric (as well as isothermal) heat addition in an evaporator

Other refrigeration cycles that are not based on mechanical work such as that of the absorption chiller are not relevant for comparison with the object of the present invention.
The object of the present invention is to provide a refrigerating process having improved efficiency as well as a refrigerator, which applies said process.
According to the present invention this object is achieved by a process, in which six changes of state of an enclosed working gas take place between two temperature levels in a cycle according to the following sequence: isochoric heat absorption, isothermal compression, isobaric condensation, isochoric heat dissipation, isothermal expansion, isobaric vaporization.
In this refrigerating process compression and expansion are preferably carried out simultaneously by a compressor.
Preferably the refrigeration process takes place simultaneously but chronologically displaced in several heat exchangers. Thereby a higher degree of efficiency may be achieved.
The refrigeration process preferably takes place in at least three heat exchangers. It is particularly advantageous if the refrigeration process takes place in six heat exchangers. The advantage being that every step of the process is executed simultaneously in a heat exchanger.
Furthermore, the object of the invention is accomplished by a refrigerator comprising at least one heat exchanger having two sections, which are fluidly interconnected with each other by a closing device in such a way, that the working fluid may flow in a gaseous or liquid state from one half to the other and may spread evenly. A warm medium flows about one section of the heat exchanger and a cold medium flows about the other section. Means for turning the heat exchangers are provided allowing liquid fluid to pass from one section of the heat exchangers to the other section. A working cylinder is provided, wherein said working cylinder is selectively connected by a connecting pipe and a valve with one section of the heat exchangers, when the valve is in its open position, and wherein said working cylinder is separated from the heat exchanger, when the valve is in its closed position. Furthermore an actuator is provided, which actuates the valves and the closing device selectively, in order to execute the above described steps of the refrigeration process.
Preferably, in the refrigerator the two sections of the heat exchanger are thermally isolated from each other by insulation. In the process the warm and the cold medium may be gaseous or liquid.
Preferably, in the refrigerator the connection between the heated and the cooled half may be closed temporarily by the closing device.
It is preferred, that the refrigerator comprises at least three heat exchangers. It is especially preferred that the refrigerator comprises six heat exchangers. The advantage being that every step of the process is executed simultaneously in a heat exchanger.
A refrigerator is preferred, in which the heat exchangers are arranged in a star shaped manner around the longitudinal axis of the working cylinder and the connecting pipes are connected alternately to either side of the working cylinder. The heat exchangers are rigidly connected to the working cylinder and are suspended with the working cylinder being rotatable around the common longitudinal axis. Further a motor for rotating the heat exchangers and the working cylinder is provided, and directing means are provided, which direct the hot and the cold medium in such a manner that each heat exchanger is moved through the cold medium for half of one rotation, whereas each heat exchanger is moved in the hot medium during the other half of the rotation.
It is preferred that the working cylinder in the refrigerator is a double-acting working cylinder, in which the compressions and expansions take place not only on one side but on both sides of the piston.
Preferably, the actuator for actuating the valves is a cam disk.
The refrigerator may preferably be used as a heat pump for generating heat which may be delivered to a heating installation or a different process, by extracting said heat from a colder gaseous or fluid medium.
In the refrigerator, radiation heat may preferably be used for purposes of heating and evaporation, and for purposes of cooling and condensation heat may be dissipated by radiation instead of dissipating the heat to a gaseous or fluid medium.
Special advantages may result from a refrigerator arrangement consisting of several refrigerators according to one of the preceding claims which are arranged in series in the hot and the cold medium, wherein the warm medium flows in a cascade manner successively through the different refrigerators and wherein the temperature increases when flowing through the heat exchangers of the different refrigerators. The cold medium flows through the same refrigerators in a reverse order in a cascade manner in the opposite direction, wherein the temperature of the cold medium decreases when flowing through the heat exchangers of the different refrigerators und wherein the temperature difference between the warm and the cold medium remains constant. The aim is to achieve a very extensive cooling and heating, respectively.
The present invention is concerned with a refrigerator which achieves a high coefficient of performance (COP) by means of six changes in state. With this refrigerator, which may also be used as a heat pump, a heat exchange between two media is to be caused via external work, wherein the heat flow occurs from the medium with the lower temperature to the medium with the higher temperature.
Basically, there is a number of heat exchangers in which evaporation and condensation take place and that are all, but not at the same time, connected to a compressor. For convenience this is assumed to be the case in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show:

FIG. 1 a schematic diagram of a model of a refrigerator, in which essential components and their relationships to each other are shown to describe the implementation of the refrigeration cycle;

FIG. 2 the valve control embodied as cam disk having cam-actuated valves;

FIG. 3 a schematic diagram of a rotor of a refrigerator having six heat exchangers;

FIG. 4A a description of the symbols used in FIGS. 4B and 4C;

FIG. 4B a graph of strokes 1 to 4 of the refrigeration cycle;

FIG. 4C a graph of

strokes

5 and 6 of the refrigeration cycle;

FIG. 5 a pressure-enthalpy-graph of C₂H₂F₂, refrigerant R134a, a working fluid;

FIG. 6 a P-v-diagram related to the P-h-graph shown in FIG. 5; and

FIG. 7 a T-s-diagram related to the P-h-graph shown in FIG. 5

As may be seen best in FIGS. 1 and 3, the refrigerator 100 comprises six heat exchangers 10, each of which consists of two halves. Each heat exchanger 10 is connected to a compression cylinder 20 by a connecting pipe 30. A valve 40 is located in the connecting pipe 30. The compression cylinder 20 comprises a double-acting piston 22.
As shown in FIG. 1, each heat exchanger 10 consists of two halves 11, 12 which are thermally insulated by an insulation 13. Each heat exchanger 10 comprises opposed pairs of pipes 14 (in the figure two pairs of pipes are shown for each heat exchanger 10), that are respectively connected to each other via a common closing device 16. When the closing device 16 is open, as is shown at “A” and “X”, the pipes of each pair of pipes 14 are connected to each other. When the closing device 16 is closed, the connection between both pipes of each pair of pipes are sealed in a gas-tight manner.
The individual pipes of the heat exchanger 10 may comprise fins 15, as shown, or may be smooth. The heat exchangers do not necessarily consist of pipes, but may also have any other shape that is pressure resistant. Both halves 11, 12 of the heat exchangers 10 may also differ from each other. The only important aspect is an appropriate heat exchange.
The closing device 16 is located between the two halves 11, 12 of the heat exchangers 10. In the present embodiment the closing device 16 is spring loaded towards a closed position. An actuation device 17 opens the closing device 16. In the present embodiment, said actuation device 17 consists of a roller 18 that rolls on a cam disk 19.
Only the main components of the refrigerant compressor are shown, i.e. the compression cylinder 20 and the piston 22. The piston 22 is double-acting. While compression takes place on one side of the piston 22 expansion or intake takes place on the other side. The piston 22 may be driven in different manners. For example, the piston 22 may be driven by a crank shaft and a piston rod or a connecting rod or also by an electrical linear motor. Thus the compressions and expansions may take place not only on one side but on both sides of the piston 22. While compression takes place on one side, expansion simultaneously takes places on the other side.
In the embodiment described herein, by means of the double action of the piston, the working gas is compressed into a heat exchanger 10 with every movement of the piston while the working gas is simultaneously sucked out of a different heat exchanger 10.
In the present embodiment the valves 40 between the heat exchangers 10 and the compression cylinder 20 are opened and closed mechanically. As best seen in FIG. 2, each of the valves 40 comprises a tappet 41 and a roller 42. The valves 40 are arranged in a star shaped manner around a cam disk 50. The cam disk 50 comprises cams 51 and a base circle 52. Other types of valve controls, such as solenoid or pneumatic valves, are also applicable. In the drawing, valve A is open, whereas valves B and C are closed. The valves 40 are located in the connecting pipe 30.
As best seen in FIG. 3, the heat exchangers 10 are arranged in a star shaped manner around the compression cylinder 20 and are firmly connected thereto. One half of the heat exchanger 10 is connected to the front side of the compression cylinder 20 and the other half is connected to the rear side. The heat exchangers 10 are shown as single pipes 14, but they may represent a gallery of pipes 14. In the middle the cam disk 50 shown in FIG. 2 is to be seen. A motor (not shown) is provided to rotate the complete arrangement of heat exchangers (heat exchanger block) around the central axis. The rotational direction is counter clockwise. A hot medium flows around one half 12 of the heat exchangers 10 which is connected to the connecting pipe 30 leading to the compression cylinder 20, whereas a cooling medium flows around the other half 11 of the heat exchangers 10.
The process of the refrigerator is executed as follows. In FIGS. 3, and 4A-4C the strokes of the refrigerator are shown successively. FIG. 4A-4C show a representation of the process sequence on the basis of the model, shown in FIG. 3. The respective movement of the piston, the position of the valve and the position of the closing device between the individual halves of the heat exchanger, and the progress of the individual heat exchangers within a rotation are shown schematically. The closing device 8 is shown as a circle having a bar between the heat exchanger halves 11, 12. If the bar is parallel to the longitudinal axis of the heat exchanger 10, the closing device 16 is open. If the bar is transverse to the longitudinal axis of the heat exchangers 10, the closing device 16 is closed.
Valves opened by tappets following the cam disk and closed via spring pressure are illustrated “from above”. The mode of operation corresponds to the representation in FIG. 2. This type of valves is most convenient with regard to the explanation, but any appropriate type of valve may be employed.
The heat exchangers 10 rotate around the central axis according to the displayed arrows. The areas in which the valves 40 are open and the closing devices are closed are shown in the figures. The compression cylinder 20 is seen from the front and is shown as a circle in FIG. 3. On the basis of this illustration the sequence of the refrigeration cycle process will be explained.
In FIG. 3, arrows show the direction of rotation. The separation of the individual changes of state of the working fluid is marked by the numbers on the outside of the rotor consisting of the heat exchangers 10 and the working cylinder 20. These numbers are also incorporated at the respective points in the thermodynamic graphs of FIG. 5 to 7.
The sequence of the individual changes of state are described as follows:

1-2 Isochoric Heat Input

In FIG. 3, the heat exchanger 10 has just left the cooling zone in position (1). The enclosed working fluid is fully evaporated. The closing device 16 is closed. As the rotation proceeds, the inner heat exchanger half 12 moves into the heating zone and is heated there. As the closing device 16 and the valve 40 are closed, the vapor of the working fluid is contained in a space of constant volume. The working fluid is heated in a constant volume to the temperature of the hot medium by the hot medium flowing around the heat exchanger. The pressure increases.
In FIG. 5 to 7 this process is shown as track (1)-(2).

2-3 Isothermal Compression

As soon as the heat exchanger 10 reaches position (2) in FIG. 3, valve 40 opens and additional vapor of the working fluid is pressed out of the compression cylinder 20 into the heat exchanger 10 by the piston 22. The pressure within the heat exchanger 10 increases. The adiabatic heat of the compression is extracted by the hot medium, so that an isothermal compression takes place. Since the pressure in the heat exchanger 10 is higher than the vapor pressure of the working fluid, the working fluid condenses. At position (3) the valve 40 closes.
In FIG. 5 to 7 this process is shown as track (2)-(3).

3-4 Isobaric Condensation

At the prevailing overpressure in the heat exchanger 10, the working fluid condenses until the vapor pressure of the working fluid at the temperature of the hot medium is reached. The condensation heat is extracted by the hot medium. The heat exchanger 10 is adapted in such a manner that this process is completed when position (4) has been reached.
In FIG. 5 to 7 this process is shown as track (3)-(4).

4-5 Isobaric Heat Extraction

At position (4) the closing device 16 is open. The condensate of the working fluid may now flow into the cooled half 11 of the heat exchanger 10 (condenser). By means of the heat exchange between the medium and the working fluid, the condensate is cooled to the lower temperature level of the cooling medium. Due to the lower vapor pressure of the working medium at this temperature, additional vapor is condensed until the vapor pressure of the working fluid at this temperature is reached. The total mass of the working fluid is cooled to the lower temperature level at position (5). Since the volume in the heat exchanger 10 is unchanged during the full track (valve 40 closed, closing device 16 open) cooling takes place at a constant volume.
In FIGS. 5 to 7 this process is shown as track (4)-(5).

5-6 Isothermal Expansion

The valve 40 is open at position (5). Working fluid is sucked out of the heat exchanger 10 by the compression cylinder 20 due a negative pressure. The pressure drops below the vapor pressure of the working fluid at the lower temperature. To obtain the vapor pressure, the working fluid evaporates. Since heat is constantly supplied by the cooling medium, this evaporation takes place at a constant temperature. Therefore an isothermal expansion and evaporation takes place. At position (6), the valve 40 closes.
In FIG. 5 to 7 this process is shown as track (5)-(6).

6-7 Isobaric Evaporation

The working fluid evaporates at negative pressure in the heat exchanger 10 until the vapor pressure of the working fluid at the lower temperature is reached. The evaporation heat is caused by the cooling medium. The heat exchangers 10 are constructed such that this process is completed when position (1) is reached again.
In FIG. 5 to 7 this process is shown as track (6)-(7).
In FIG. 4A to 4C, the alternating changes of the processes in the different heat exchangers and the relationship among each other and to the compression cylinder 20 can easily be understood. The rotation of the heat exchangers 10 has proceeded by 60° with every shown stroke. On the basis of the depicted process it may be observed, that the piston 3 changes its direction after every rotation by 60°, and three complete strokes (back and forth) are executed with every full rotation of the rotor consisting of the heat exchangers and the compression cylinder. With this construction the piston will execute as many cycles as heat exchangers are connected to one side of the compression cylinder 20.
It is considered that the number of heat exchangers in the refrigerator may be a multiple of three. Further it is an advantageous alternative that the number of heat exchangers is a multiple of six. Thus a correspondingly connected working cylinder may be selectively connected on its one side with a heat exchanger into which the working fluid is to be pumped, while at the same time a different heat exchanger may be connected with the opposite side of the working cylinder, out of which the working fluid is to be pumped.
The main difference of the present invention to the state of art is that several heat exchangers, consisting of evaporator and condenser, are operated at the same time, but the sequences of the refrigeration cycle process take place simultaneously but chronologically displaced, and the changes of state, expansion and compression are always effected in every heat exchanger by a common compressor.
The mode of operation of this invention differs from all conventional refrigeration cycles due to the six necessary changes of state. Conventional cycles essentially consist (refraining from overheating of the vapor of the working fluid or integrated intermediate cycles) of four changes of state.
This invention further distinguishes itself by a higher theoretical degree of efficiency than conventional refrigeration cycles.

Claims

1. Refrigeration process, in which, in a cyclic process, six changes of state of an enclosed working gas between two temperature levels take place in the following sequence:

Isochoric heat input

Isothermal compression

Isobaric condensation

Isochoric heat extraction

Isothermal expansion

Isobaric evaporation.

2. Refrigeration process according to claim 1, wherein the compression and the expansion take place simultaneously by a compressor.

3. Refrigeration process according to claim 1, wherein the refrigeration process takes place simultaneously but chronologically displaced in several heat exchangers.

4. Refrigeration process according to claim 3, wherein the refrigeration process takes place in three heat exchangers.

5. Refrigeration process according to claim 3, wherein the refrigeration process takes place in six heat exchangers.

6. Refrigerator comprising the following:

at least one heat exchanger having two sections, which are interconnected with each other by a closing device such that the working fluid may flow in a gaseous and liquid state of aggregation from one section to the other and may distribute uniformly;

wherein a hot medium flows about one section of the heat exchangers whilst a cold medium flows about the other section;

means for transporting liquid fluid from one section of the heat exchanger to the other section;

a working cylinder that is selectively connected to one part of the heat exchanger by a connecting pipe and a valve, when the valve is in the open position, and that is disconnected from the heat exchanger, when the valve is in the closed position;

a controller that selectively actuates the valves and the closing device, in order to execute the steps of the refrigeration process according to claim 1.

7. Refrigerator according to claim 6, wherein the two sections of the heat exchangers are thermally insulated from each other.

8. Refrigerator according to claim 6, wherein the hot and the cold medium may either be gaseous or fluid.

9. Refrigerator according to claim 6, wherein the connection between the heated and the cooled half may temporarily be closed by the closing device.

10. Refrigerator according to claim 6 that comprises at least three heat exchangers.

11. Refrigerator according to claim 6 that comprises six heat exchangers.

12. Refrigerator according to claim 11, wherein the heat exchangers are arranged in a star shaped manner around the longitudinal axis of the working cylinder and the connecting pipes are alternately connected to both sides of the working cylinder,

wherein the heat exchangers are rigidly connected to the working cylinder and are suspended in such a manner that they are rotatable around the common longitudinal axis together with the working cylinder,

wherein a motor is comprised for rotating the heat exchangers and the working cylinder, and

wherein directing means are comprised for directing the hot and the cold medium in such a way, that the individual heat exchangers are moved through the cold medium for one half of one rotation and moved through the hot medium during the other half of the rotation.

13. Refrigerator according to claim 6, wherein the working cylinder is a double-acting working cylinder, in which the compressions and expansions do not only take place on one side but on both sides of the piston.

14. Refrigerator according to claim 6, wherein the controller is a cam disk.

15. Refrigerator according to claim 6, wherein the refrigerator is used as a heat pump for producing heat that may be delivered to a heating facility or a different process, by extracting said heat from a colder gaseous or liquid medium.

16. Refrigerator according to claim 6, wherein radiation heat is used for purposes of heating and evaporation, and wherein heat may be dissipated by radiation instead of dissipating the heat to a gaseous or liquid medium for purposes of cooling and condensation.

17. Refrigerator arrangement consisting of several single refrigerators according to one of the preceding claims that are arranged in series in the hot and the cold medium, wherein the warm medium flows in a cascade manner successively through the individual refrigerators and wherein the temperature increases when flowing through the heat exchangers of the different refrigerators, wherein the cold medium flows through the same refrigerators in a reverse order in a cascade manner in the opposite direction, wherein the temperature of the cold medium decreases when flowing through the heat exchangers of the different refrigerators und wherein the temperature difference between the warm and the cold medium remains constant, namely with the aim to achieve a very extensive cooling and heating, respectively.