Patent Application
20250012511
The invention relates to a heat exchanger, in particular a shell-and-tube heat exchanger, for use with a rotor having an axis of rotation, comprising:
The invention further relates to a rotor, in particular a rotary heat pump, comprising:
Finally, the invention relates to a method for exchanging heat between a first heat-exchange medium, in particular a liquid, and a second heat-exchange medium, in particular a gas, preferably a noble gas, inside a rotor, comprising the steps of:
A rotary heat pump is known from WO2015/103656, in which the centrifugal acceleration of the rotor is used to generate different pressure or temperature levels. Here, high temperature heat is withdrawn from the compressed working medium and comparatively low temperature heat is fed to the expanded working medium. To this end, the rotary heat pump comprises inner heat exchangers and outer heat exchangers, which are arranged substantially parallel to the axis of rotation of the rotor. The inner heat exchangers are configured for heat exchange at a lower temperature and the outer heat exchangers are configured for heat exchange at a higher temperature.
In addition, in stationary applications, shell-and-tube heat exchangers are often used, in which the working medium flows through a bundle of tubes arranged within a cylindrical housing shell. The heat-exchange medium flows through the shell space in loops formed by baffle plates. This type of heat exchanger promises particularly good heat transfer between the two media. In stationary applications of such shell-and-tube heat exchangers, the entering flow of the working medium is split up symmetrically to the main direction of flow in order to distribute the working medium accordingly between the individual tubes.
However, when trying to use the known shell-and-tube heat exchangers with a rotor, in particular with a rotary heat pump, it has been shown that the heat transfer between the media falls significantly short of expectations.
The general state of the art is further illustrated by GB 1 383 690 A and CH 576 615 A5.
Thus, the object of the present invention is to alleviate or eliminate the drawbacks of the state of the art. The aim of the invention is preferably to provide a heat exchanger, which comprises a high efficiency when used in a rotor.
This object is achieved by a heat exchanger according to claim 1, a rotor according to claim 8 and a method according to claim 13. Preferred embodiments are given in the dependent claims.
According to the invention, a device for homogenising the flow through the second heat-exchange channels is provided. This device comprises a throttle member, which is designed for throttling, to different extents, an inner flow of the second heat-exchange medium that passes through the inner one of the second heat-exchange channels, and an outer flow of the second heat-exchange medium that passes through the outer one of the second heat-exchange channels between the entry opening in the distribution element and the exit opening in the merger element.
For the purposes of this disclosure, the location and direction indications refer to the intended use of the heat exchanger as part of a rotor. “Upstream” and “downstream” refer to the direction of flow of the second heat-exchange medium. “Radial” and “axial” refer to the axis of rotation of the rotor. “On the inside” means closer to the axis of rotation of the rotor. “On the outside” means further away from the axis of rotation. The distances refer to the radial distances from the axis of rotation.
Thus, the invention is based on the surprising finding that the heat exchanger cannot be operated effectively under the effect of centrifugal acceleration by uniformly distributing the second heat-exchange medium. The invention solves this problem in that the different pressure differences of the side flows of the second heat-exchange medium flowing at different distances from between the axis of rotation the entry opening in the distribution element and the exit opening in the merger element are at least partially, preferably substantially completely, compensated.
Advantageously, this way it can be achieved that the flow through the second heat-exchange channels is substantially uniform.
Comprehensive flow analyses have shown that the main cause of the different pressure differences of the side flows is that the outer flow in the distribution element first flows outwards and is compressed due to the centrifugal force before the outer flow along the outer one of the second heat-exchange channels exchanges heat with the first heat-exchange medium and then flows inwards in the merger element towards the exit opening and inner is thereby expanded; for the flow, the sequence is reversed since the inner flow in the distribution element first flows inwards and is expanded due to the centrifugal force, then exchanges heat with the first heat-exchange medium along the inner one of the second heat-exchange channels before the inner flow in the merger element is guided outwards towards the exit opening and is thereby compressed.
When the second heat-exchange medium in the second heat-exchange channels gives off heat to the first heat-exchange medium, the pressure difference is created by first compressing at low density before the heat exchange, namely from the collected inflow of the second heat-exchange medium via the entry opening to the inflow opening in the outer heat-exchange channel, then heat dissipation takes place in the outer heat-exchange channel, whereby the temperature of the second heat-exchange medium decreases and thus—in the case of a substantially isobaric heat exchange—the density increases; then the second heat-exchange medium expands again with comparatively high density, namely from the outflow opening in the outer heat-exchange channel to the collection of the second heat-exchange medium at the exit opening. Because the second heat-exchange medium compresses at low density (low pressure difference) and expands at high density (higher pressure difference), an additional pressure difference remains when this flow thread is considered, which is required when flowing through the outer heat-exchange channel. This would result in the second heat-exchange medium favouring the inner one of the second heat-exchange channels. When heat is supplied to the second heat-exchange medium by the first heat-exchange medium, it is the other way around. Then, the second heat-exchange medium would favour the outer one of the second heat-exchange channels.
The invention now sets out to compensate for the additional pressure difference by means of the throttle member, which throttles, to different extents, the outer and the inner flow in a portion between the entry opening in the distribution element and the outflow opening in the merger element, i.e. causes different flow resistances.
If a heat dissipation from the second heat-exchange medium to the first heat-exchange medium in the second heat-exchange channels takes place, the throttle member is configured to throttle the inner flow to a greater extent than the outer flow.
If a heat supply from the first heat-exchange medium to the second heat-exchange medium in the second heat-exchange channels takes place, the throttle member is configured to throttle the outer flow to a greater extent than the inner flow.
Thus, the throttle member is configured for asymmetrically throttling the flow of the second heat-exchange medium with respect to the centre or symmetry axis of the heat exchanger. With the aid of the throttle member, the second heat-exchange medium is subjected to essentially the same pressure differences as it flows through the heat exchanger from the entry to the exit opening. Advantageously, this way it can be achieved that the flow through the second heat-exchange channels is substantially uniform, so that the second heat-exchange medium along the second heat-exchange channels in each case comprises substantially the same average flow velocity or substantially the same volumetric flow rate (provided that the second flow channels, as preferred, have the same flow cross-section).
In a preferred embodiment, the heat exchanger is designed as a shell-and-tube heat exchanger. The shell-and-tube heat exchanger comprises a tube bundle having a plurality of tubes, preferably each having a substantially circular cross-section, which enclose the second heat-exchange channels. The tubes preferably extend parallel to one another. The tube bundle can be arranged within a preferably cylindrical housing. The first heat-exchange medium is guided through first heat-exchange channels, which extend inside the housing. Deflection elements for the first heat-exchange medium are preferably provided within the housing. The deflection elements are preferably arranged substantially perpendicular to the tubes. Preferably, the deflection elements inside the housing leave recesses for the first heat-exchange medium, wherein the recesses are preferably arranged alternately on opposite sides. As a result, the first heat-exchange medium is guided in a loop through the interior of the housing, with the first heat-exchange medium flowing in portions transversely to the tubes having the second heat-exchange channels.
In a first preferred embodiment, the throttle device comprises a throttle orifice plate having throttle openings, wherein a throttle opening, which is further away from the axis of rotation, and a throttle opening, which is closer to the axis of rotation, are of different sizes. The throttle orifice plate can be arranged upstream of the inflow openings, in particular directly upstream of the inflow openings, or downstream of the outflow openings, in particular directly downstream of the outflow openings. In one embodiment for dissipating heat from the second heat-exchange medium, the throttle opening, which is further away from the axis of rotation, is larger than the throttle opening, which is closer to the axis of rotation. In one embodiment for supplying heat to the second heat-exchange medium, the throttle opening, which is further away from the axis of rotation, is smaller than the throttle opening, which is closer to the axis of rotation. The advantage of this embodiment of the throttle member is the simple constructive implementation. Furthermore, the heat exchanger can be set to a specific operating point by simply replacing the throttle orifice plate.
The throttle orifice plate is preferably arranged upstream of the second heat-exchange channels such that the second heat-exchange medium is fed via the throttle openings to exactly one of the second heat-exchange channels, respectively. Alternatively, the throttle orifice plate may be arranged downstream of the second heat-exchange channels such that the second heat-exchange medium is discharged from each second heat-exchange channels through exactly one throttle opening.
Below, preferred embodiments of the throttle orifice plate will be described with reference to an embodiment for dissipating heat from the second heat-exchange medium along the second heat-exchange channels. Accordingly, the principle can be transferred to the case of supplying heat to the second heat-exchange medium if throttling to a greater extent, in this case by means of smaller throttle openings, is provided by the distance from the axis of rotation outwards.
The throttle orifice plate preferably comprises at least one first throttle opening at a first distance from the axis of rotation and at least one second throttle opening at a second distance from the axis of rotation of the rotor, the second distance being larger than the first distance and the second throttle opening being larger than the first throttle opening.
The throttle orifice plate preferably comprises at least one third throttle opening at a third distance from the axis of rotation, which is larger than the second distance, the at least one third throttle opening being larger than the at least one second throttle opening. The throttle orifice plate preferably comprises at least one fourth throttle opening at a fourth distance from the axis of rotation, which is larger than the third distance, the at least one fourth throttle opening being larger than the at least one third throttle opening. Of course, the throttle orifice plate may comprise further throttle openings at further distances from the axis of rotation of the rotor, wherein throttle openings, which are further away from the axis of rotation, are in each case larger than throttle openings, which are closer to the axis of rotation.
In a preferred embodiment, the heat exchanger comprises a plurality of rows of second heat-exchange channels, the second heat-exchange channels of each row each comprising substantially the same distance from the axis of rotation of the rotor. Correspondingly, the throttle orifice plate preferably comprises a plurality of rows each having a plurality of throttle openings, wherein a row, which is further away from the axis of rotation, and a row, which is closer to the axis of rotation, comprise throttle openings of different sizes. In the case of dissipating heat, the row of throttle openings, which is further away from the axis of rotation, comprises larger throttle openings than the row of throttle openings, which is closer to the axis of rotation.
Thus, a first row of first throttle openings, each substantially at a first distance from the axis of rotation, and a second row of second throttle openings, each substantially at a second distance from the axis of rotation, preferably also a third row of third throttle openings, each substantially at a third distance from the axis of rotation, preferably also a fourth row of fourth throttle openings, each substantially at a fourth distance from the axis of rotation, preferably also at least one further row of further throttle openings, each at a further distance from the axis of rotation, may be provided.
In order to enable the second heat-exchange medium to be fed into the individual second heat-exchange channels, the distribution element is arranged upstream of the second heat-exchange channels (in the direction of flow of the second heat-exchange medium), the distribution element being expanded, i.e. formed with an increasing cross-section in the direction of flow of the second heat-exchange medium. The distribution element enables the distribution of the flow of the second heat-exchange medium at the entry of the heat exchanger into the individual flows within the second heat-exchange channels. Preferably, the distribution element is conically expanded.
In a second preferred embodiment, a flow grid is arranged within the distribution element, the flow grid comprising individual distribution channels, which expand in the direction of flow, the distribution channels each comprising an initial portion and an end portion.
In a second embodiment of the throttle member, the initial and/or end portion of a distribution channel, which is further away from the axis of rotation, and the initial and/or end portion of a distribution channel, which is closer to the axis of rotation, comprise different flow cross-sections. The advantage of this embodiment is that the flow grid is generally useful for good distribution and flow guidance in order to keep pressure losses as low as possible. Advantageously, this flow grid can now also be designed as a throttle member, with which an asymmetrical cross-section expansion is achieved in order to compensate for the different pressure differences depending on the distance from the axis of rotation. The initial portion connects to the entry in the heat exchanger. The end portion guides the second heat-exchange medium to the inflow opening in the second heat-exchange channel. In the case of dissipating heat from the second heat-exchange medium to the first heat-exchange medium, the initial and/or end portion of the distribution channel, which is further away from the axis of rotation, comprises a larger flow cross-section than the initial and/or end portion of the distribution channel, which is closer to the axis of rotation.
The flow grid preferably comprises exactly one distribution channel per second heat-exchange channel, so that the second heat-exchange medium is fed via each distribution channel to exactly one of the second heat-exchange channels. The distribution channels are separated from one another by individual wall parts, wherein preferably standing and lying wall parts are provided. The standing wall parts serve, on the one hand, to ensure uniform distribution in the tangential direction (whereby the above-described problem of different pressures does not occur here), but also have the advantage that the lying wall parts, which are provided for the radial distribution of the flow, are supported against deflection under the effect of centrifugal force.
Below, preferred embodiments of the flow grid will be described with reference to one embodiment for dissipating heat from the second heat-exchange medium along heat-exchange channels. Accordingly, the principle can be transferred to the case of supplying heat, if throttling to a greater extent is provided with the distance from the axis of rotation outwards.
The flow grid preferably comprises at least one first distribution channel at a first distance from the axis of rotation, and at least one second distribution channel at a second distance from the axis of rotation of the rotor, the second distance being larger than the first distance, and the initial and/or end portion having a larger flow cross-section than the initial and/or end portion of the first distribution channel. Preferably, the flow grid comprises at least one third distribution channel at a third distance from the axis of rotation, the third distance being larger than the second distance, and the initial and/or the end portion of the third distribution channel having a larger flow cross-section than the initial and/or end portion of the second distribution channel. Preferably, the flow grid comprises at least one fourth distribution channel at a fourth distance from the axis of rotation, the fourth distance being larger than the third distance, and the initial and/or the end portion of the fourth distribution channel having a larger flow cross-section than the initial and/or end portion of the third distribution channel. Of course, the flow grid may comprise further distribution channels at further distances from the axis of rotation, wherein the flow cross-section of the initial and/or of the end portion increases with the distance from the axis of rotation.
The flow grid preferably comprises at least one first row with a plurality of individual, i.e. separate, first distribution channels substantially at a first distance from the axis of rotation, and a second row with a plurality of second distribution channels substantially at a second distance from the axis of rotation, preferably also a third row a with plurality of third distribution channels substantially at a third distance from the axis of rotation, preferably also a fourth row with a plurality of fourth distribution channels substantially at a fourth distance from the axis of rotation, preferably also further rows each with a plurality of further distribution channels.
In a first variant, the initial portion of the distribution channel, which is further away from the axis of rotation, comprises a larger flow cross-section than the initial portion of the distribution channel, which is closer to the axis of rotation, wherein the end portion of the distribution channel, which is further away from the axis of rotation, comprises substantially the same flow cross-section as the end portion of the distribution channel, which is closer to the axis of rotation. This embodiment is particularly advantageous for constructive reasons if the second heat-exchange channels have the same flow cross-sections. Thus, in this variant, the second heat-exchange medium can flow asymmetrically into the flow grid, wherein during the inflow the flow cross-section increases with the distance from the axis of rotation. The outflow from the flow grid, on the other hand, can take place symmetrically, i.e. with essentially the same flow cross-section.
In a second variant, the end portion of the distribution channel, which is further away from the axis of rotation, comprises a larger flow cross-section than the end portion of the distribution channel, which is closer to the axis of rotation, wherein the initial portion of the distribution channel, which is further away from the axis of rotation, comprises substantially the same flow cross-section as the initial portion of the distribution channel, which is closer to the axis of rotation. This embodiment is particularly simple in terms of construction. Thus, in this variant, the inflow into the flow grid can be symmetrical, but the outflow from the flow grid can be asymmetrical.
In a third variant, the initial portion and the end portion of the distribution channel, which is further away from the axis of rotation, each comprise a larger flow cross-section than the initial portion and the end portion of the distribution channel, which is closer to the axis of rotation. Thus, in this variant, both the inflow into the flow grid and the outflow from the flow grid can take place asymmetrically, i.e. with a larger flow cross-section with increasing distance from the axis of rotation.
The asymmetrical distribution of the second heat-exchange medium by means of the flow grid has the result that an axially close flow of the second heat-exchange medium from entering the heat exchanger until exiting the heat exchanger flows in portions through a smaller flow cross-section than an axially distant flow of the second heat-exchange medium, as a result of which the axially close flow is subjected to a higher pressure loss than the axially distant flow. As a result, the pressure difference between the axially close second heat-exchange channel and the axially distant second heat-exchange channel is at least partially, preferably substantially completely, compensated.
Furthermore, a flow grid may be arranged within the merger element, the flow grid comprising within the merger element individual merger channels tapering in the direction of flow, the merger channels each comprising an initial portion (on the side of the outflow openings in the second heat-exchange channels) and an end portion (on the side facing away from the outflow openings). In order to form the throttle member, the initial and/or end portion of a merger channel, which is further away from the axis of rotation, and the initial and/or end portion of a merger channel, which is closer to the axis of rotation comprise different flow cross-sections.
In a third preferred embodiment, the device for homogenising the flow through the second heat-exchange channels comprises turbulators, in particular spiral turbulators, within the second heat-exchange channels, wherein a turbulator, which is further away from the axis of rotation, and a turbulator, which is closer to the axis of rotation, cause different pressure losses. In the case of dissipating heat from the second heat-exchange medium along the second heat-exchange channels, the turbulator, which is further away from the axis of rotation, causes a lower pressure loss than the turbulator, which is closer to the axis of rotation.
To this end, the turbulator, which is further away from the axis of rotation, and the turbulator, which is closer to the axis of rotation, may comprise different spiral lengths. In the case of dissipating heat from the second heat-exchange medium along the second heat-exchange channels, the turbulator, which is further away from the axis of rotation, may comprise a greater slope than the turbulator, which is closer to the axis of rotation.
The advantage of the turbulators over the previously described embodiments of the throttle device is that not only can the pressure loss in the second heat-exchange channels be adjusted, to different extents, with different distances from the axis of rotation in order to achieve a uniform flow through the second flow channels, but also the heat transfer is increased by increased turbulence during heat transfer.
In a fourth embodiment, the outer and the inner one of the second heat-exchange channels for forming the throttle member comprise different flow cross-sections, different diameters in the case of tubes with circular cross-sections.
In a preferred application, a rotor, in particular a rotary heat pump, is provided with the heat exchanger in one of the embodiments previously described.
In a first preferred embodiment, a central axis or axis of symmetry of the heat exchanger is arranged at a radial distance, i.e. with an axial offset, from the axis of rotation.
In a second preferred embodiment, the central axis of the heat exchanger is arranged substantially in line with the axis of rotation. In this case, too, the second heat-exchange channels have different distances from the axis of rotation.
In the rotor, the second heat-exchange channels preferably extend substantially parallel to and at different radial distances from the axis of rotation. The first heat-exchange channels may extend in sections essentially perpendicular to the second heat-exchange channels, as is usual with shell-and-tube heat exchangers.
In one preferred embodiment, the rotor comprises a compressor unit, in which the second heat-exchange medium in order to increase pressure is guided away from the axis of rotation due to the centrifugal force, and an expansion unit, in which the second heat-exchange medium in order to reduce pressure is guided towards the axis of rotation due to the centrifugal force.
In this embodiment of the rotor, at least one inner heat exchanger, with respect to the axis of rotation, and at least one outer heat exchanger, with respect to the axis of rotation are preferably provided. Depending on the embodiment, the outer heat exchanger and/or the inner heat exchanger may be configured according to any one of the above embodiments of the heat exchanger.
The method according to the invention for exchanging heat between a first heat-exchange medium, in particular a liquid, and a second heat-exchange medium, in particular a gas, preferably a noble gas, inside a rotor, comprises the following steps:
In a preferred embodiment, a heat dissipation from the second to the first heat-exchange medium is performed along the second heat-exchange channels, wherein the inner flow of the second heat-exchange medium is throttled to a greater extent than the outer flow of the second heat-exchange medium.
The invention is explained below with reference to preferred exemplary embodiments, which are illustrated in the drawings.
In the shown embodiment, the heat exchanger 7 is designed as a shell-and-tube heat exchanger. The shell-and-tube heat exchanger comprises a cylindrical housing 10 in which a tube bundle is arranged. The tube bundle comprises elongated tubes 11 arranged parallel to one another and at distances in the radial direction and in the circumferential direction. Inside, the tubes 11 include second heat-exchange channels 12 for the second heat-exchange medium. The tubes 11 are each held at opposite ends in a tube sheet in the form of a bottom plate 11A (cf.
As can also be seen from
In principle, the embodiment of the heat exchanger 7 as a shell-and-tube heat exchanger is very advantageous for use with the rotor 1. However, it is essential that the flow through the second heat-exchange channels 12 is uniform in order to use the heat transfer surface effectively.
As can be seen from
Surprisingly, however, it has been shown that in the rotating state of the rotor 1 under high centrifugal acceleration, a number of phenomena occur that prevent a uniform flow by simply splitting up the entering flow of the second heat-exchange medium. As a reason, it was recognised that different densities occur during entering and exiting of the second heat-exchange medium, in this case the gas, at the different radial distances from the centre of rotation of the discrete second flow channels 12.
As can be seen from
In order to illustrate the technical effect, the following assumptions and simplifications are made for a model calculation:
If the flow of the gas assumed to be ideal, i.e. without taking into account real-gas characteristics, takes place only under the gravitational acceleration, and the heat exchanger is oriented such that the gravitational acceleration has the same direction as the centrifugal acceleration, then the pressure difference between the outermost flow channel and the innermost flow channel is 0.14 mbar and is not taken into account due to the minimal effect.
In this embodiment, a device 30 for homogenising the flow through the second heat-exchange channels 12 is provided, with which different pressure differences of the second heat-exchange medium are compensated, which are caused by the different radial distances of the second heat-exchange channels 12 from the axis of rotation 2 of the rotor 2.
In the embodiment shown, a throttle device for throttling, to different extents, the discrete second heat-exchange channels 12 is provided as the device 30 for homogenising the flow through the second heat-exchange channels 12. In this case, a flow of the second heat-exchange medium, which is closer to the axis of rotation 2, i.e. comprising a smaller radial distance, is throttled to a greater extent than a flow of the second heat-exchange medium, which is further away from the axis of rotation 2, i.e. comprising a larger radial distance.
In the embodiment according to
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In the embodiment according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 21216865.2 | Dec 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/087405 | 12/22/2022 | WO |
