Patent Grant
9003827
This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in International Patent Application No. PCT/DK2010/000177 filed on Dec. 16, 2010 and Danish Patent Application No. PA 2009 01350 filed Dec. 18, 2009.
The present invention relates to an expansion device unit for a vapour compression system, such as a refrigeration system, an air condition system or a heat pump, the vapour compression system comprising an evaporator with at least two evaporator paths. The expansion device unit of the invention is capable of delivering fluid medium to the evaporator in such a manner that the pressure of fluid medium received in one evaporator path is distinct from the pressure of fluid medium received in at least one of the other evaporator paths.
In vapour compression systems fluid medium, such as refrigerant, is circulated along a refrigerant path wherein the components of the vapour compression system are arranged. The fluid medium is compressed in a compressor. The compressed fluid medium is then fed to a condenser, where the compressed fluid medium is condensed, the fluid medium leaving the condenser thereby being substantially in a liquid state. The fluid medium is then fed to an expansion device, where it is expanded before entering an evaporator. In the evaporator the fluid medium is evaporated before once again entering the compressor, thereby completing the cycle.
As the fluid medium is evaporated in the evaporator, heat exchange takes place between the fluid medium and a secondary fluid flow across the evaporator, thereby cooling the fluid of the secondary fluid flow. This may be used for providing refrigeration to a closed volume, such as a room or a refrigeration entity, e.g. of the kind used in supermarkets. In the case that the difference between the temperature of the incoming secondary fluid flow and the desired outlet temperature is relatively large, it is necessary to control the operation of the vapour compression system in such a manner that the evaporator temperature, and thereby the pressure in the evaporator, is very low, in order to ensure a sufficiently high refrigeration capacity. This is undesirable, since it is very energy consuming, in particular because a relatively high amount of energy is consumed by the compressor in order to compress the low pressure fluid medium leaving the evaporator.
For instance, in the case that the vapour compression system is an air condition system, the fluid of the secondary fluid flow is air which is refrigerated, due to heat exchange with the fluid medium evaporating in the evaporator, in order to reduce the temperature inside an enclosure, such as a room. In some cases it may be required to reduce the temperature of air flowing across the evaporator from approximately 26° C. to approximately 10° C. in order to obtain a desired temperature of the enclosure. In this case the evaporator temperature must be maintained below 10° C.
U.S. Pat. No. 2,215,327 discloses an air condition system comprising an evaporator with two evaporator coils arranged fluidly in parallel in the refrigerant path. The evaporator coils are further arranged in series with respect to the path of the air circulated across the evaporator. One of the evaporator coils is maintained at a higher refrigerant pressure and surface temperature than the other evaporator coil. The evaporator coil with the higher surface temperature is used for lowering the temperature of the air passing over the evaporator, and the evaporator coil with the lower temperature is used for lowering the temperature of the air passing over the evaporator as well as for lowering the humidity of the air passing over the evaporator. In order to maintain the evaporator coils at different pressures, each evaporator coil is provided with a suction pressure control valve which controls the flow of refrigerant through the corresponding evaporator coil. The valves are of the same construction, but are adjusted to maintain different refrigerant pressures in the evaporator coils.
The suction pressure control valves are arranged fluidly between the evaporator coils and a common suction line being fluidly connected to the compressor. The suction pressure control valves reduce the pressure of the refrigerant leaving the evaporator coils, and the refrigerant pressure prevailing in the common suction line is therefore lower than the refrigerant pressure of the refrigerant leaving at least one of the evaporator coils. Accordingly, the energy consumed by the compressor in order to compress the refrigerant received via the common suction line is relatively high.
Furthermore, the system comprises expansion valves arranged fluidly in front of each of the evaporator coils, and the expansion valves are provided with thermostatic elements or bulbs respectively secured to the coils adjacent the outlets thereof. Accordingly, the expansion valves are operated independently of each other.
It is an object of embodiments of the invention to provide an expansion device unit being capable of delivering at least two fluid flows at distinct pressures, on the basis of measurements performed on only one of the fluid flows.
It is a further object of embodiments of the invention to provide an expansion device unit which allows a high refrigeration capacity with a low energy consumption in a vapour compression system having the expansion device unit arranged therein.
According to the invention there is provided an expansion device unit for a vapour compression system, the expansion device unit comprising:
In the present context the term ‘vapour compression system’ should be interpreted to mean any system in which a flow of fluid medium, such as refrigerant, circulates and is alternatingly compressed and expanded, thereby providing either refrigeration or heating of a volume. Thus, the vapour compression system may be a refrigeration system, an air condition system, a heat pump, etc.
In the present context the term ‘expansion device unit’ should be interpreted to mean a part of the vapour compression system which is at least responsible for expanding fluid medium, such as refrigerant.
In the present context the term ‘fluid medium’ should be interpreted to mean a medium which is entirely in a liquid state, entirely in a gaseous state or in a mixed liquid and gaseous state.
The expansion device unit comprises an inlet opening and at least two outlet openings. Accordingly, during operation the expansion device unit receives a single flow of fluid medium, and at least two parallel flows of fluid are delivered from the expansion device unit. Thus, the fluid medium undergoes expansion and is divided into at least two parallel flow paths by the expansion device unit.
The expansion device unit comprises a main expanding section and a distributing section. The main expanding section is adapted to expand fluid medium received via the inlet opening before delivering the fluid medium to the outlet openings. It should be understood that expansion of the fluid medium takes part mainly or completely in the main expanding section.
The distribution section is arranged to split the fluid flow received via the inlet opening into the at least two flows of fluid which are to be delivered via the outlet openings. The distribution section may have a pure flow splitting function. As an alternative, some expansion of the fluid medium may take place in the distribution section.
The main expanding section and/or the distribution section is/are arranged to cause pressures in fluid delivered via at least two of the outlet openings to be distinct. Thus, fluid medium delivered from the expansion device unit via one outlet opening has a pressure which is significantly different from the pressure of fluid medium delivered from the expansion device unit via at least one other outlet opening. In the case that the expansion device unit is connected to an evaporator comprising at least two evaporator paths in such a manner that each outlet opening is connected to an inlet opening of an evaporator path, the fluid medium delivered to two different evaporator paths have distinct pressures. As a consequence, the evaporator temperatures in the evaporator paths will also be distinct. Thereby it is possible to allow a secondary fluid flow across the evaporator to be gradually cooled by successive evaporator paths. Thereby a desired target temperature can be reached, without requiring that all of the evaporator paths have a very low evaporator temperature. Thus, though some of the evaporator paths may have a very low temperature, this will only apply to part of the total mass flow, the remaining part of the mass flow having a higher temperature and thereby a higher suction pressure.
The main expanding section is operated on the basis of one or more parameters measured in the fluid flow delivered by one of the outlet openings. Thus, it is only necessary to arrange sensors in one of the fluid flows, and the expansion of fluid delivered by all of the outlet openings is operated on the basis of the measurements performed by these sensors. It should be noted that the one or more parameters measured in the fluid flow delivered by one of the outlet openings are not necessarily measured immediately after the fluid has been delivered from the outlet opening. It/they may alternatively be measured further downstream, e.g. after the fluid flow has passed through a separate evaporator path. However, the measurement(s) should be performed in a part of the system where the fluid flow delivered from the outlet opening is separate from the fluid flow(s) delivered from the other outlet opening(s). Thereby it is possible to obtain operation of expansion of fluid medium to all of the outlet openings using only one set of measurements, while it is still possible to keep the flow paths of fluid delivered from the outlet openings as separate flow paths. This is an advantage, since it is thereby possible to provide a vapour compression system having the expansion device unit arranged therein with separate suction lines interconnecting parallel evaporator paths directly with a compressor. Thereby some of the mass flow of fluid medium can be maintained at a relatively high pressure, and the total work to be delivered by the compressor in order to compress the fluid medium can be reduced.
Furthermore, appropriate control of expansion of fluid medium to each of the outlet openings can easily be obtained in the case that evaporator paths receiving fluid medium from the outlet openings are arranged in series along a flow direction of a secondary flow across the evaporator. In this case, when one evaporator path experiences a high load, the remaining evaporator paths will also experience a high load, and when one evaporator path experiences a low load, the remaining evaporator paths will also experience a low load. Accordingly, it is possible to estimate the load of one evaporator path on the basis of one or more control parameters related to one of the other evaporator paths, and appropriate control of expansion of fluid medium to all of the outlet openings can therefore be obtained on the basis of a single measurement.
The main expanding section may be fluidly connected between the inlet opening and the distribution section. According to this embodiment, the fluid flow received via the inlet opening is expanded by the main expanding section before it is divided into a number of parallel flow paths by the distribution section.
The distribution section may, in this case, comprise a number of parallel flow paths, each flow path being fluidly connected to an outlet opening, and at least one of the flow paths may have a flow restrictor arranged therein. A flow restrictor introduces a pressure drop in the fluid flow, and the pressure drop depends on the size of the flow restrictor. Thus, according to this embodiment, the fluid medium is initially expanded to a common pressure level by the main expanding section. The fluid flow is then divided into at least two parallel flow paths by the distribution section, and the fluid medium flowing in the parallel flow path(s) having a flow restrictor arranged therein undergo a further pressure drop, and thereby the pressure of fluid medium delivered via an outlet opening connected to a flow path with a flow restrictor is distinct from the pressure of fluid medium delivered via an outlet opening connected to a flow path which does not have a flow restrictor arranged therein. Thus, according to this embodiment, the distinct pressure levels are provided by the distribution section.
Alternatively, the distribution section may be fluidly connected between the inlet opening and the main expanding section. According to this embodiment, the fluid medium received via the inlet opening is initially divided into a number of parallel flow paths. Subsequently, the fluid medium is expanded separately in the parallel flow paths.
The main expanding section may, in this case, comprise a number of thermostatic expansion valves, the number of thermostatic expansion valves corresponding to the number of outlet openings. According to this embodiment, each of the parallel flow paths is provided with a separate thermostatic expansion valve. The expansion valves are designed to provide distinct pressure levels in at least two of the fluid flows. Thus, according to this embodiment, the distinct pressure levels are at least partly provided by the main expanding section. Furthermore, all of the expansion valves are controlled simultaneously and in dependence of each other in response to one or more parameters measured in the fluid flow delivered by one of the outlet openings.
The main expanding section may comprise an inner cylinder and an outer cylinder, the inner cylinder being arranged movably inside the outer cylinder and coaxially with the outer cylinder, the outer cylinder and the inner cylinder each being provided with a set of openings, wherein the mutual position of the set of openings of the inner cylinder and the set of openings of the outer cylinder determines the fluid flows towards the outlet openings.
According to this embodiment, the ‘opening degree’ of each of the flow paths through the cylinder device towards the outlet openings are controlled simultaneously by performing relative movements between the inner cylinder and the outer cylinder. Accordingly, such a main expanding section can very easily be operated on the basis of one or more parameters measured in the fluid flow delivered by one of the outlet openings, while ensuring that distinct pressure levels are obtained in the fluid flows delivered by the outlet openings. The relative movements between the inner cylinder and the outer cylinder may be rotational movements about the common axis and/or axial movements along the common axis. By selecting openings of various size, it can be obtained that the pressure levels in the fluid medium delivered from the outlet openings are distinct.
As an alternative, the main expanding section may comprise two disks being arranged movably with respect to each other, and each disk being provided with a set of openings. According to this embodiment, the two disks may be arranged rotatably with respect to each other in such a manner that the sizes of overlaps between the openings in one disk and corresponding openings in the other disk depend on the mutual rotational position of the disks. As an alternative, one disk may be provided with a set of openings, each of the openings being fluidly connected to an outlet opening, and the other disk may be provided with a set of valve elements, each being arranged to cooperate with a specific opening in the first disk to determine an ‘opening degree’ towards a given outlet opening. The fluid flow towards each of the outlet openings can thereby be controlled simultaneously an in dependence of each other by performing relative axial movements of the disks, i.e. moving the disks towards and away from each other, thereby simultaneously moving the openings and the valve elements relative to each other. In any event, by providing openings of various sizes, it can be obtained that the pressure levels of fluid medium delivered by the outlet openings are distinct.
As another alternative, the main expanding section and the distribution section may form an integral part. According to this embodiment, the fluid medium received via the inlet opening is simultaneously expanded and divided into a number of parallel flow paths, each flow path being connected to an outlet opening.
The main expanding section may comprise at least one thermostatic expansion valve. As an alternative, the main expanding section may be or comprise an orifice, a capillary tube or any other suitable kind of expansion device.
The invention further provides a vapour compression system comprising a compressor, a condenser, an expansion device unit according to the invention, and an evaporator comprising at least two evaporator paths arranged fluidly in parallel, wherein each of the outlet openings of the expansion device unit is fluidly connected to an evaporator path of the evaporator.
According to this aspect of the invention, the expansion device unit delivers fluid medium, such as refrigerant, to the at least two parallel evaporator paths of the evaporator.
The vapour compression system may be a refrigeration system, such as an air condition system or a heat pump.
According to one embodiment, each of the evaporator paths may be fluidly connected to the compressor via a separate suction line. This allows the distinct pressure levels of the separate flow paths to be maintained until the fluid medium is compressed in the compressor. Thereby a large temperature difference between an inlet temperature and an outlet temperature of a secondary fluid flow across the evaporator can be obtained, without requiring that the entire mass flow of fluid medium is compressed from a low pressure level in the compressor. Thereby the energy consumption of the compressor can be reduced.
The invention will now be described in further detail with reference to the accompanying drawings in which
The expansion device unit 4 comprises an expansion valve 6 and a distributor 7. The distributor 7 splits a fluid flow received from the expansion valve 6 into a number of parallel fluid flows, three of which are shown, each fluid flow being supplied to an evaporator path 5a, 5b, 5c. Two of the shown parallel flow paths of the distributor 7 have a flow restrictor 8 arranged therein. Thereby the mass flow delivered to evaporator path 5a is larger than the mass flows delivered to evaporator paths 5b and 5c. It should be noted that the flow restrictors 8 may not be identical, and that the mass flow delivered to evaporator path 5b may therefore differ from the mass flow delivered to evaporator path 5c.
Each of the evaporator paths 5a, 5b, 5c is fluidly connected directly to the compressor 2 via a separate suction line 9a, 9b, 9c.
The expansion valve 6 is controlled on the basis of measurements performed in the fluid flowing in suction line 9a by means of sensor 10. The sensor 10 may advantageously measure one or more parameters being indicative of the superheat of the fluid flowing in suction line 9a, and it may, e.g., be or comprise a thermostatic element or a bulb.
The vapour compression system 1 of
The fluid medium is then evaporated in the evaporator paths 5a, 5b, 5c. Since the pressure of the fluid medium delivered to one evaporator path 5a, 5b, 5c is distinct from the pressure of the fluid medium delivered to at least one of the other evaporator paths 5a, 5b, 5c, the evaporating temperatures of the evaporator paths are also distinct, and the suction pressures in the suction lines 9a, 9b, 9c are consequently also distinct. Accordingly, the pressures in the parallel flow paths are distinct throughout the entire path from the distributor 7 to the compressor 2. This allows the evaporator temperature of evaporator path 5a to be higher than the evaporator temperature of evaporator path 5b, which is higher than the evaporator temperature of evaporator path 5c. Thereby a secondary air flow across the evaporator 5, illustrated by arrows 11, can be gradually cooled by heat exchange with the evaporator 5.
From point 13 to point 14a the fluid medium is expanded in the expansion valve 6. The pressure is decreased while the enthalpy remains constant. The pressure level at point 14a can be regarded as a common intermediate pressure level which is reached by the entire fluid flow when passing through the expansion valve 6. Furthermore, the pressure level at point 14a is the pressure level of the fluid medium which is supplied to evaporator path 5a.
From point 14a to point 14b a part of the fluid medium passes through flow restrictor 8 in the flow path leading to evaporator path 5b. When the fluid medium passes through the flow restrictor, an additional pressure drop is introduced, and the pressure level at point 14b is therefore lower than the pressure level at point 14a. Accordingly, the pressure of the fluid medium supplied to evaporator path 5b is lower than the pressure of the fluid medium supplied to evaporator path 5a.
Similarly, from point 14a to point 14c a part of the fluid medium passes through flow restrictor 8 in the flow path leading to evaporator path 5c. As described above, this introduces an additional pressure drop in the fluid medium. It is clear from
From point 14a to point 15a fluid medium passes through evaporator path 5a, from point 14b to point 15b fluid medium passes through evaporator path 5b, and from point 14c to point 15c fluid medium passes through evaporator path 5c. It is clear that the pressure levels in the three evaporator paths 5a, 5b, 5c are distinct. It is also clear that the enthalpy of fluid medium leaving evaporator path 5a is higher than the enthalpy of fluid medium leaving evaporator path 5b, which is in turn higher than the enthalpy of fluid medium leaving evaporator path 5c.
From point 15a to point 12 fluid medium which is supplied to the compressor 2 via suction line 9a is compressed by the compressor 2. Similarly, from point 15b to point 12 fluid medium which is supplied to the compressor 2 via suction line 9b is compressed by the compressor 2, and from point 15c to point 12 fluid medium which is supplied to the compressor 2 via suction line 9c is compressed by the compressor 2. The enthalpy increase for each of these compressing steps is indicated by arrows 16a, 16b and 16c, respectively. It is clear from
In the embodiment of
Each of the evaporator paths 5a, 5b, 5c is fluidly connected to the compressor 2 via a separate suction line 9a, 9b, 9c as it is the case in the vapour compression system 1 of
The expansion valves 6a, 6b, 6c constitute ‘flow restrictions’ in the respective flow paths, the size of each flow restriction depending on the opening degree of the expansion valve 6a, 6b, 6c. The simultaneous and mutually dependent operation of the expansion valves 6a, 6b, 6c ensures that the expansion valves 6a, 6b, 6c are operated in such a manner that a predetermined ratio in ‘flow restriction’ among the expansion valves 6a, 6b, 6c is obtained. The ratio may advantageously be selected in a manner which follows a load pattern which is determined by the evaporator paths 5a, 5b, 5c.
As mentioned above, the separate expansion valves 6a, 6b, 6c allow the fluid medium to be expanded to different pressure levels. The expansion valves 6a, 6b, 6c may be operated in such a manner that a predetermined ratio of the pressure levels is maintained. However, the ratio of the pressure levels may alternatively be allowed to vary, and the expansion valves 6a, 6b, 6c may instead be operated to obtain a predetermined ratio of ‘flow restriction’, opening degree or another relevant parameter.
In the expansion device unit 4 shown in
In
From point 14a to point 15a fluid medium passes through evaporator path 5a, from point 14b to point 15b fluid medium passes through evaporator path 5b, and from point 14c to point 15c fluid medium passes through evaporator path 5c. It is clear that the pressure levels in the three evaporator paths 5a, 5b, 5c are distinct. It is also clear that the enthalpy of fluid medium leaving evaporator path 5a is higher than the enthalpy of fluid medium leaving evaporator path 5b, which is in turn higher than the enthalpy of fluid medium leaving evaporator path 5c.
Similarly to the situation described above with reference to
It is an advantage of the embodiment illustrated in
The opening 19a is larger than the opening 19b. Therefore, at a given relative position of the first disk 20 and the second disk 21, the flow passage at opening 19a is larger than the flow passage at opening 19b. As a consequence, the pressure of the fluid medium leaving the expansion device unit 4 via outlet opening 18a is higher than the pressure of the fluid medium leaving the expansion device unit 4 via outlet opening 18b. Thus, in the embodiment shown in
In
In
In
In
In
In
In the embodiment illustrated by
The outer cylinder 28 is provided with four openings 30, each being fluidly connected to an outlet opening (not shown) of the expansion device unit. The opening 30a is larger than the opening 30b, which is larger than the opening 30c, which is larger than the opening 30d. The inner cylinder 29 is provided with four regions 31 having an increased cross sectional diameter. The regions 31 having an increased cross sectional diameter can be moved to a position where a partial or complete overlap between the regions 31 and the openings 30 of the outer cylinder 28 by moving the inner cylinder 29 along an axial direction relative to the outer cylinder 28.
Fluid medium is received in the distribution section 7 at inlet opening 17 and passes between the outer cylinder 28 and the inner cylinder 29 and through the openings 30 towards the outlet openings. The overlap between the regions 31 and the openings 30 defines an opening degree for each of the flow passages towards the outlet openings. Since the respective overlaps are changed by moving the inner cylinder 29, the opening degrees are controlled simultaneously and in dependence of each other. Accordingly, this embodiment is very suitable for being controlled on the basis of a single measured control parameter.
Furthermore, the different sizes of the openings 30 causes the pressure levels of the fluid medium leaving the distribution section 7 via the openings 30 to be distinct, similarly to the situation described above with reference to
Although the invention above has been described in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009 01350 | Dec 2009 | DK | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DK2010/000177 | 12/16/2010 | WO | 00 | 1/24/2013 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/072685 | 6/23/2011 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2144898 | Shrode | Jan 1939 | A |
| 2215327 | Karsten | Sep 1940 | A |
| 5341656 | Rust et al. | Aug 1994 | A |
| 5479784 | Dobmeier et al. | Jan 1996 | A |
| 20050198997 | Bush | Sep 2005 | A1 |
| 20100269527 | Thybo et al. | Oct 2010 | A1 |
| Number | Date | Country |
|---|---|---|
| 102007028564 | Dec 2008 | DE |
| 1975525 | Oct 2008 | EP |
| 1170463 | Nov 1969 | GB |
| 2006021071 | Mar 2006 | WO |
| 2008151630 | Dec 2008 | WO |
| 2008154919 | Dec 2008 | WO |
| 2009146704 | Dec 2009 | WO |
| Entry |
|---|
| The International Search Report for PCT/DK2010/000177 dated Mar. 4, 2011. |
| Number | Date | Country | |
|---|---|---|---|
| 20130111946 A1 | May 2013 | US |
