A coupling device, a kit, and a heat transfer arrangement comprising the same

Abstract

The disclosure relates to a coupling device (300) for fluidly connecting a refrigerant recirculation loop (134) to a heat exchanger refrigerant port (210a, 210b), said coupling device axis (A) comprising: an attachment portion (320) and a distributing portion (330), wherein the distributing portion (330) is made, at least in part, of a porous material configured to allow fluid transport therethrough, wherein the coupling device (300) is structured and arranged such that, when mounted onto the heat exchanger (200), the coupling device (300) protrudes into the heat exchanger refrigerant port (210a, 210b) to form a clearance volume (350) between interior walls (211) of the heat exchanger refrigerant port (210a, 210b) and exterior surfaces (333) of the distributing portion (330) being not more than 20% of a port interior volume (240a, 240b) of the heat exchanger refrigerant port (210a, 210b).

Description

Field of the disclosure

[0001] The present disclosure relates to a coupling device for fluidly connecting a refrigerant recirculation loop to a heat exchanger refrigerant port of a heat exchanger in a heat pump. The disclosure further relates to a kit comprising a coupling device and a heat exchanger. The disclosure further relates to a heat transfer arrangement for heating and / or cooling a building which comprises a coupling device and / or a kit.Background art

[0002] Nearly all large, developed cities in the world have at least two types of energy grids incorporated in their infrastructures; one grid for providing electrical energy and one grid for providing space heating and hot tap water preparation. Today a common grid used for providing space heating and hot tap water preparation is a gas grid providing a burnable gas, typically a fossil fuel gas. The gas provided by the gas grid is locally burned for providing space heating and hot tap water. In order to reduce the carbon dioxide emissions there are plans to replace such gas grid with more "green" energy efficient energy systems.

[0003] One such energy efficient energy system is cold thermal grids. Cold thermal grids are an evolution of district heating and district cooling systems, where combined district heating and district cooling system with aid of using heat pumps for heating and cooling can provide both cooling, heating and tap water preparation to buildings.

[0004] In order to succeed with the replacement of gas grids, where the respective gas burner is replaced by a heat pump, the heat pumps used need to be smaller, less costly, easier to control and with lower technical complexity, e.g., with fewer and / or less complex sensors for measuring the space heat and tap water energy consumption than presently used heat pumps. Refrigerants are required in heat pumps and the high efficiency (COP) for heat pumps is dependent of efficient refrigerants. Many efficient refrigerants have large GWP (Global warming potential values) and there is consequently an incitement to use refrigerants with low GWP. Some refrigerants have low GWP but other unwanted characteristics, which in turn has forced authorities to set requirements on the maximum amount of GWP allowed in one heat pump in order to be allowed to be placed in certain zones such as an unventilated area in a building. A small amount of refrigerant will inevitably limit the COP and thereby the maximum power for the heat pump. An example of such a refrigerant is R290, and the amount of allowed R290 in a heat pump is currently 152 g when being placed in an unventilated area.

[0005] There is thus a need in the art of making heat pumps more efficient, in particular with regards to the refrigerant utilization therein, in order to be able to provide adequate heating within the limits set forth by authorities.Summary

[0006] It is an object to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination. These and other objects are at least partly met by the invention as defined in the independent claims. Preferred embodiments are set out in the dependent claims.

[0007] According to a first aspect there is provided a coupling device for fluidly connecting a refrigerant recirculation loop to a heat exchanger refrigerant port of a heat exchanger in a heat pump, wherein said heat exchanger refrigerant port defines a port interior volume which extends into the heat exchanger from a refrigerant port opening end towards a refrigerant port bottom end and fluidly connects to internal heat exchange channels of the heat exchanger, said coupling device having an extension along a coupling device axis and comprising: an attachment portion structured and arranged to be attachable to the heat exchanger at the refrigerant port opening end, said attachment portion having a connecting port for connecting to a fluid conduit system of the refrigerant recirculation loop and an inner conduit line in fluid communication with the connecting port, and a distributing portion which has an elongated extension along the coupling device axis from a first end to a second end, opposite to the first end, wherein the distributing portion is made, at least in part, of a porous material configured to allow fluid transport therethrough, wherein the coupling device is structured and arranged such that, when mounted onto the heat exchanger, the attachment portion is connected to the distributing portion at its first end to allow fluid communication between the inner conduit line and the distributing portion, and such that the coupling device protrudes into the heat exchanger refrigerant port from the refrigerant port opening end towards the refrigerant port bottom end to form a clearance volume between interior walls of the heat exchanger refrigerant port and exterior surfaces of the distributing portion which is not more than 20% of the port interior volume.

[0008] The coupling device according to the first aspect may be advantageous as it allows reducing the amount of refrigerant which for different reasons is not contributing to heat transfer in the refrigerant recirculation loop of the heat pump. This is achieved by means of reducing unnecessary volumes in the fluid conduit system housing the refrigerant recirculation loop and by enhancing mixing. By minimizing such unnecessary volumes, the total amount of refrigerant in the system may be decreased. Moreover, many of these unnecessary volumes are shaped such that refrigerant accumulates there thereby never contributing to the heat transfer process.

[0009] One part of the refrigerant recirculation loop which is particularly prone to this problem is the inlet and / or outlet of the heat exchanger(s). A heat pump has two heat exchangers acting, at one time, as evaporator and condenser respectively. The refrigerant must pass both of these heat exchangers during a refrigerant cycle. This means that refrigerant must enter two times and exit two times making altogether four passages through inlets and outlets of the heat exchangers. The reason for these passages being extra prone to the above-mentioned problem is that heat exchangers typically have relatively large inlet and outlet port volumes. Here, the refrigerant, especially at passages where the refrigerant is in a liquid form, may accumulate due to wake and turbulence and thereby not actively contributing to the heat transfer process within the heat pump.

[0010] The coupling device may be advantageous as it minimizes the problem by actively reducing the effective volume of the heat exchanger ports by its shape. By allowing the coupling device to protrude into the heat exchanger refrigerant port and effectively leave not more than 20% of the port interior volume between the interior walls of the heat exchanger refrigerant port and the exterior surfaces of the distributing portion (termed herein: the clearance volume), the effective "free volume" of the heat exchanger refrigerant port which the refrigerant may use can be considerably reduced. By providing a distributing portion made, at least in part, of a porous material, the refrigerant which enters the distributing portion via the inner conduit line of the attachment portion will be allowed to distribute three-dimensionally within the porous material to eventually leave the distributing portions through its exterior surfaces. This may enhance mixing in the clearance volume, hence further reducing the risk of refrigerant accumulating therein. Once the refrigerant has left the coupling device, it may directly enter the internal heat exchange channels of the heat exchanger.

[0011] For embodiments where the clearance volume is non-zero, the clearance volume effectively defines a flow channel between the exterior surfaces of the distributing portion and the interior walls of the heat exchanger refrigerant port. The coupling device may thus be structured and arranged such that, when mounted onto the heat exchanger, a flow channel interconnecting the coupling device with the internal heat exchange channels of the heat exchanger is formed, or defined, between exterior surfaces of the distributing portion and interior walls of the heat exchanger refrigerant port. This flow channel further fluidly interconnects the internal heat exchange channels of the heat exchanger and thus further allows to distribute the refrigerant. By design choice, the volume and shape of this flow channel may be chosen to further reduce the risk of any refrigerant accumulating. If some refrigerant nevertheless accumulates, the amount of such refrigerant is expected to be considerably reduced when compared to the prior art solution, as a result from the considerably reduced effective volume of the heat exchanger refrigerant port as detailed hereinabove.

[0012] As readily appreciated by the person skilled in the art, the provision of the flow channel is not essential. Thus, other embodiments may have a tight fit between the coupling device and the heat exchanger refrigerant port thus providing a very small, or even negligible, clearance volume for defining a flow channel. For such embodiments the distribution of refrigerant to the respective internal heat exchange channels of the heat exchanger is effectively achieved internally within the porous material of the distributing portion. For such embodiments, the coupling device may substantially encompass, or fill, the entire port interior volume.

[0013] Another advantage of the coupling device is that the porous material of the distributing portion provides natural filtering. In prior art systems the filtering is usually carried out in a separate filtering device which is connected in series to the refrigerant recirculation loop. In order to be able to house a filter, such as a mesh filter, with an active area large enough to provide acceptable pressure losses in the refrigerant recirculation loop, the filter units typically also define unnecessary large interior volumes which tend to create further volumes within the refrigerant recirculation loop where refrigerant can accumulate thus not contributing to heat transfer. By the provision of the porous distributing portion, the refrigerant which passes the inner conduit line of the attachment portion will be allowed to pass the distributing portion within the heat exchanger refrigerant port to be filtered on its way towards the internal heat exchange channels of the heat exchanger where heat transfer subsequently takes place.

[0014] As stated hereinabove, the coupling device protrudes into the heat exchanger refrigerant port from the refrigerant port opening end towards the refrigerant port bottom end to form a clearance volume between interior walls of the heat exchanger refrigerant port and exterior surfaces of the distributing portion being not more than 20% of the port interior volume. For an embodiment of the distributing portion which has a homogeneous inner structure without internal voids or cavities, the coupling device will occupy at least 80% of the port interior volume. Alternative embodiments of the distributing portion having inner voids and / or cavities may however occupy less than 80% of the port interior volume since the inner voids and / or cavities will take up a fraction of the total volume. It is stressed here that the important parameter to control is the clearance volume formed between the heat exchanger and the coupling device inside the heat exchanger refrigerant port. If this clearance volume becomes too large, the risk of refrigerant accumulating due to wake and turbulence increases.

[0015] The coupling device may protrude into the heat exchanger refrigerant port from the refrigerant port opening end towards the refrigerant port bottom end to form a clearance volume between interior walls of the heat exchanger refrigerant port and exterior surfaces of the distributing portion being not more than 18%, or 16%, or 14%, or 10% or 8% or 6% or 4%, or 2% of the port interior volume.

[0016] It is however also conceivable to have a larger clearance volume. As an example, the coupling device may protrude into the heat exchanger refrigerant port from the refrigerant port opening end towards the refrigerant port bottom end to form a clearance volume between interior walls of the heat exchanger refrigerant port and exterior surfaces of the distributing portion being not more than 50%, or 45%, or 40%, or 35% or 30% or 25% of the port interior volume. Naturally, the risk of creating volumes of refrigerant which for different reasons is not contributing to heat transfer in the refrigerant recirculation loop of the heat pump may increase for increasing relative clearance volume. However, it is foreseen that some embodiments may need to have a somewhat larger clearance volume than other embodiments for example because of manufacturing constraints and / or costs.

[0017] In preferred embodiments, it is the distributing portion which protrudes into the heat exchanger refrigerant port, whereas the attachment portion remains just outside thereof. However, it is also conceivable that the attachment portion protrudes, at least partly, into the heat exchanger refrigerant port.

[0018] The second end of the distributing portion may be disposed in a vicinity of the refrigerant port bottom end. For some embodiments, the second end of the distributing portion may be in abutment with the refrigerant port bottom end. For alternative embodiments, the second end of the distributing portion may be separated from the refrigerant port bottom end by the clearance volume.

[0019] The connecting port and the inner conduit line of the attachment portion may together form a through-bore, or through-hole. The connecting port and the inner conduit line of the attachment portion may be aligned substantially in parallel with the coupling device axis A.

[0020] With the term "refrigerant recirculation loop" is herein meant a closed circuit through which a constant volume of refrigerant is circulated. The refrigerant recirculation loop comprises a first heat exchanger unit and a second heat exchanger unit as well as a compressor, and an expander. The aforementioned units are connected to each other in series by means of a fluid conduit system to define the refrigerant recirculation loop. The fluid conduit system comprises tubing. The tubing is typically made of a metal, such as cupper.

[0021] With the term "port interior volume" is herein meant the total volume of the heat exchanger refrigerant port as defined extending into the heat exchanger from the refrigerant port opening end towards the refrigerant port bottom end. Naturally, an "effective volume" available for refrigerant within the heat exchanger refrigerant port will be smaller than the port interior volume if any further element or object is present within the heat exchanger refrigerant port, such as for example the coupling device.

[0022] The coupling device axis may be aligned substantially in parallel with the extension of the heat exchanger refrigerant port from the refrigerant port opening end towards the refrigerant port bottom end.

[0023] According to some embodiments, a cross sectional area of the distributing portion as seen transverse to its elongated extension is substantially constant along the elongated extension.

[0024] According to some embodiments, a cross-sectional area of the distributing portion as seen transverse to its elongated extension is at least 95% of a cross-sectional area of the heat exchanger refrigerant port, as seen transverse to the coupling device axis.

[0025] The distributing portion may have a cross-sectional area being at least 90% or at least 92%, or at least 94% or at least 96% or at least 98% of a cross-sectional area of the heat exchanger refrigerant port, as seen transverse to the coupling device axis.

[0026] For some embodiments the distributing portion may alternatively have a cross-sectional area being at least 70%, or at least 75%, or at least 80%, or at least 85% of a cross-sectional area of the heat exchanger refrigerant port, as seen transverse to the coupling device axis.

[0027] This may be advantageous as it allows the clearance volume formed between the exterior surfaces of the distributing portion and the interior walls of the heat exchanger refrigerant port to act as a flow channel. The provision of a flow channel may provide a good compromise between achieving a refrigerant flow with an acceptable pressure drop, and a considerably reduced overall volume for reducing the degree of stationary, passive, refrigerant in the refrigerant recirculation loop. Further, it may aid in providing a more uniform flow rate into the individual internal heat exchange channels of the heat exchanger.

[0028] As used herein, the term "cross-sectional area" should be construed as the total cross-sectional area defined by the element or part. Thus, a cross-sectional area of a hollow cylinder should be construed as the area of the circle defined by the enveloped surface, not by the area of the annular ring which may be defined for such a hollow cylinder.

[0029] According to some embodiments, the elongated extension of the distributing portion is at least 95% of a longitudinal extension of the clearance volume. The elongated extension of the distributing portion may alternatively be at least 90% or at least 92%, or at least 94% or at least 96% or at least 98% of a longitudinal extension of the clearance volume.

[0030] For some embodiments the elongated extension of the distributing portion may alternatively have a cross-sectional area being at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85% of a longitudinal extension of the clearance volume.

[0031] This may be advantageous as it provides a good compromise between achieving enough clearance for the coupling device during mounting thereof to the heat exchanger, and a considerably reduced overall volume for reducing the degree of stationary, passive, refrigerant in the refrigerant recirculation loop.

[0032] The longitudinal extension of the clearance volume may be equal to an extension of the port interior volume into the heat exchanger from the refrigerant port opening end to the refrigerant port bottom end. Alternatively, the longitudinal extension of the clearance volume may be smaller than the extension of the port interior volume. The latter may occur e.g. for embodiments where the attachment portion protrudes into the heat exchanger refrigerant port thereby occupying a portion of the port interior volume.

[0033] As used herein, the longitudinal extension of the clearance volume is defined as being parallel to the elongated extension of the distributing portion. Consequently, the longitudinal extension of the clearance volume is also parallel to the coupling device axis.

[0034] According to some embodiments, the attachment portion is integrally formed by one material.

[0035] This may be advantageous as it can make the attachment portion easier to manufacture. Alternatively, the attachment portion may be made of two or more elements which are attached to each other. The attachment portion may be made of a metal, such as e.g., brass, stainless steel, or cupper.

[0036] According to some embodiments, the distributing portion is integrally formed by one material.

[0037] This may be advantageous as it can makes the distributing portion easier to manufacture. Alternatively, the distributing portion may be made of two or more elements which are attached to each other.

[0038] According to some embodiments, the distributing portion is made of a porous sintered metal, such as stainless steel, bronze, or nickel.

[0039] The attachment portion and the distributing portion are connected to each other to form the coupling device. The connection may be realised in different ways. The attachment portion and the distributing portion may be non-releasably attached to each other. As a non-limiting example, the attachment portion and the distributing portion may be separate elements which are attached to each other, e.g. by soldering, gluing or welding. The attachment portion and the distributing portion may alternatively be releasably attached to each other. As a non-limiting example, the attachment portion and the distributing portion may be attached to each other by screwing or clamping. Alternatively, the attachment portion and the distributing portion may be made from one element.

[0040] The disclosure should not be construed as limited to the attachment portion and the distributing portion being connected to each other prior to being mounted inside the heat exchanger. For some embodiments, the attachment portion and the distributing portion may be individual elements which may be inserted one by one in the heat exchanger and connected to each other first during assembly. As a non-limiting example, the distributing portion may first be inserted to rest at its second end against the interior walls of the heat exchanger refrigerant port at its refrigerant port bottom end. In a second step, the attachment portion may be inserted on top of the distributing portion and, when being attached to the heat exchanger at the refrigerant port opening end, the attachment portion may be configured to exert a force onto the distributing portion thereby clamping the distributor portion between the interior walls at the refrigerant port opening end of the heat exchanger refrigerant port and the attachment portion.

[0041] According to some embodiments, the connecting port is structured and arranged to receive tubing of the fluid conduit system of the refrigerant recirculation loop, wherein a cross-sectional area of the connecting port is larger than the cross-sectional area of the inner conduit line. The cross-sectional areas are seen transverse to the coupling device axis.

[0042] This may be advantageous as it allows to provide a relatively uniform transition between the tubing and the inner conduit line, thus further aiding in minimizing the risk of creating stationary, or passive, refrigerant in the refrigerant recirculation loop.

[0043] According to some embodiments, the attachment portion has a threaded portion structured and arranged to be threadedly engageable with an associated threaded portion of the heat exchanger when attaching the coupling device thereto.

[0044] This may be advantageous as it provides an efficient and secure attachment between the coupling device and the heat exchanger and further allows an easier replacement of the coupling device. However, other attachment means are also conceivable. Alternatively, the attachment may be achieved by soldering or by gluing. For such attachments, the attachment portion may not have a threaded portion.

[0045] According to some embodiments, the distributing portion has a shape which is geometrically complementary to the port interior volume of the heat exchanger refrigerant port of the heat exchanger.

[0046] The term "geometrically complementary" should in this context be construed to include a tolerance between the distributing portion and the heat exchanger refrigerant port, since a physical body may be challenging to insert into a physical opening having the exact same dimensions without risking jamming.

[0047] According to some embodiments, the distributing portion has a strictly convex shape.

[0048] The term "strictly convex shape" implies that any line segment joining two points on or in the distributing portion will lie entirely within the shape. As such, the distributing portion may have no holes, indentations, recesses, or inner cavities. An example of such a strictly convex shape is a cylinder without any internal cavities. The person skilled in the art realises that the above definitions are used for the macroscopic geometry / shape of the distributing portion. Naturally, the microscopic geometry will have cavities since the material is at least in part porous.

[0049] According to some embodiments, the coupling device has an axisymmetric geometry about the coupling device axis. The heat exchanger refrigerant port may be substantially cylindrically shaped. This implies that the flow channel which is formed between exterior surfaces of the distributing portion and interior walls of the heat exchanger refrigerant port may substantially have the shape of a hollow cylinder. Other shapes are however conceivable.

[0050] According to some embodiments, the coupling device further comprises an expansion valve in direct attachment with the attachment portion. The expansion valve may be an electronic expansion valve, or a thermal expansion valve. The expansion valve may be attached to the attachment portion by soldering.

[0051] This may be advantageous as it allows further reducing unnecessary volumes in the fluid conduit system of the refrigerant recirculation loop. Moreover, it may simplify assembly of a heat pump including such a coupling device.

[0052] According to some embodiments, the distributing portion has an internal cavity which meets and mouths into the inner conduit line of the attachment portion to provide direct fluid communication between the internal cavity and the inner conduit line.

[0053] The internal cavity may extend at least 70% of the elongated extension of the distributing portion. The internal cavity may include a plurality of internal cavity portions which are fluidly connected to each other. The internal cavity may be beneficial to reduce the pressure drop through the distributing portion. In some embodiments, the internal cavity may extend at least 30%, or at least 40% or at least 50% or at least 60% or at least 80% or at least 90% of the elongated extension of the distributing portion.

[0054] According to a second aspect there is provided a kit for a heat pump comprising: a heat exchanger which comprises first and second heat exchanger refrigerant ports for fluidly connecting the heat exchanger to a refrigerant recirculation loop of the heat pump, wherein each of said first and second heat exchanger refrigerant ports defines a respective port interior volume which extends into the heat exchanger from a respective heat exchanger port opening end towards a respective heat exchanger port bottom end and fluidly connects to internal heat exchange channels of the heat exchanger, and a coupling device according to the first aspect being structured and arranged such that, when mounted onto the heat exchanger at one of said first and second heat exchanger refrigerant ports, the coupling device protrudes into said one of said first and second heat exchanger refrigerant ports from its respective heat exchanger port opening end towards its respective heat exchanger port bottom end to form a clearance volume between interior walls of the heat exchanger refrigerant port and exterior surfaces of the distributing portion being not more than 20% of the port interior volume.

[0055] According to a third aspect there is provided a heat transfer arrangement for heating and / or cooling a building comprising at least one heat pump, said heat transfer arrangement comprising: at least one coupling device according to the first aspect, and / or at least one kit according to the second aspect.

[0056] According to some embodiments, the at least one heat pump is at least one modular liquid-liquid heat pump, wherein each of the at least one modular liquid-liquid heat pump is structured and arranged to be individually detachable from the heat transfer arrangement.

[0057] According to some embodiments, the at least one modular liquid-liquid heat pump is a plurality of modular liquid-liquid heat pumps operating in parallel.

[0058] According to some embodiments, a total mass of refrigerant contained in each of the at least one modular liquid-liquid heat pump is below 400 g, or below 300 g, or below 200 g.

[0059] The amount allowed refrigerant in a refrigerant recirculation loop having the refrigerant R290 is for one type of heat pumps currently 152 g without requirements on that the zone should be a ventilated area. The amount allowed refrigerant in a refrigerant recirculation loop having the refrigerant R290 is for another type of heat pumps currently 334 g without requirements on that the zone should be a ventilated area. Other refrigerants may have different predetermined threshold-values.

[0060] The refrigerant may be chosen from the group consisting of R290, R32, R410A, R470C and R134A.

[0061] Effects and features of the second and third aspects are largely analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the second aspect and third aspects. It is further noted that the inventive concepts relate to all possible combinations of features unless explicitly stated otherwise.

[0062] A further scope of applicability of the present disclosure will become apparent from the detailed description given below. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the scope of the disclosure will become apparent to those skilled in the art from this detailed description.

[0063] Hence, it is to be understood that this disclosure is not limited to the particular component parts of the device described or steps of the methods described as such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", "including", "containing" and similar wordings does not exclude other elements or steps.Brief descriptions of the drawings

[0064] The disclosure will by way of example be described in more detail with reference to the appended [schematic] drawings, which shows presently preferred embodiments of the disclosure. Figure 1A illustrates a modular liquid-liquid heat transfer arrangement for heating and / or cooling and / or providing tap water to buildings or the like according to an example embodiment of the disclosure. Figure 1B illustrates the modular liquid-liquid heat transfer arrangement of Fig. 1A where one of the heat pump modules is detached from the arrangement. Figure 2A illustrates a heat exchanger according to an example embodiment of the disclosure in a perspective exploded view. Figure 2B illustrates the heat exchanger of Fig. 2A when mantled together. Figure 3 illustrates the heat exchanger of Figs 2A and B when connected to a refrigerant recirculation loop according to the prior art. Figure 4 illustrates the heat exchanger of Figs 2A and B when connected to the refrigerant recirculation loop by means of a coupling device according to an embodiment of the disclosure. Figure 5A is a perspective view of the coupling device of Fig. 4. Figure 5B is a side view of the coupling device of Fig. 4. Figure 5C is a cross-sectional view of the coupling device along a section taken along the line X1-X1 of Fig. 5B. Figure 5D is a cross-sectional view of the coupling device of Fig. 5A along a section taken along the line X2-X2 of Fig. 5C. Figure 5E is a cross-sectional view of the coupling device of Fig. 5A along a section taken along the line X3-X3 of Fig. 5C. Figure 5F is a cross-sectional view of the coupling device of Fig. 5A along a section taken along the line X4-X4 of Fig. 5C. Figure 6A is a side view of a coupling device according to another example embodiment of the disclosure. Figure 6B is a cross-sectional view of the coupling device of Fig. 6A along a section taken along the line X5-X5 of Fig. 6A. Figure 7A is a cross-sectional side view of a coupling device according to another example embodiment of the disclosure. Figure 7B is a cross-sectional view of the coupling device of Fig. 7A along a section taken along the line X6-X6 of Fig. 7A. Figure 8A is a cross-sectional side view of a coupling device according to another example embodiment of the disclosure. Figure 8B is a cross-sectional view of the coupling device of Fig. 8A along a section taken along the line X7-X7 of Fig. 8A. Figure 8C is a cross-sectional view of the coupling device of Fig. 8A along a section taken along the line X8-X8 of Fig. 8A. Detailed description

[0065] The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the disclosure to the skilled person.

[0066] Figures 1 and 2 illustrates a modular liquid-liquid heat transfer arrangement 100 for heating and / or cooling and / or providing tap water to buildings or the like by way of example. Hereafter, the modular liquid-liquid heat transfer arrangement 100 may also be referred to as "heat transfer arrangement 100" or "arrangement 100".

[0067] The heat transfer arrangement 100 comprises a cold side and a hot side. The heat transfer arrangement 100 is configured to transfer thermal energy from the cold side to the hot side. The cold side comprises first inlet and outlet junction pipes 111, 112. The cold side is connected to a cold liquid side 101 via the first inlet and outlet junction pipes 111, 112 thereby forming a cold side liquid recirculation path 103. The hot side comprises second inlet and outlet junction pipes 122, 121. The hot side is connected to a hot liquid side 102 via the second inlet and outlet junction pipes 122, 121 thereby forming a hot side liquid recirculation path 104.

[0068] The first inlet junction pipe 111 is configured to supply a cold side liquid (often termed: a brine) from the cold liquid side 101 to the heat transfer arrangement 100. The first outlet junction pipe 112 is configured to return the cold side liquid from the heat transfer arrangement 100 to the cold liquid side 101, thereby forming the cold side liquid recirculation path 103. During heating, the cold side liquid has a higher temperature when supplied to the heat transfer arrangement 100 then when being returned therefrom to the cold liquid side 101.

[0069] The second outlet junction pipe 121 is configured to supply a hot side liquid (typically: water) from the heat transfer arrangement 100 to the hot liquid side 102. The second inlet junction pipe 122 is configured to return the hot side liquid from the hot liquid side 102 to the heat transfer arrangement 100 thereby forming the hot side recirculation path 104. During heating, the hot side liquid has a lower temperature when supplied to the heat transfer arrangement 100 then when being returned therefrom to the hot liquid side 101.

[0070] The liquid-liquid heat transfer arrangement 100 may be a liquid-liquid heat pump arrangement configured to provide heat to the hot side liquid for heating the same. The liquid-liquid heat transfer arrangement 100 may be a liquid-liquid cool pump arrangement configured to remove heat from the cold side liquid for cooling the same.

[0071] For typical heating applications of the arrangement 100, the cold liquid side 101 may be an evolution of district heating and district cooling systems, where combined district heating and district cooling system with aid of using heat pumps for heating and cooling can provide both cooling, heating and tap water preparation to buildings. The cold liquid side 101 may be coupled to a downhole heat exchanger, or borehole heat exchanger. For typical heating applications of the arrangement 100, the hot liquid side 102 may be a heating system, such as radiators or tap water systems, in the building. The hot liquid side 102 will be described in detail later.

[0072] The heat transfer arrangement 100 further comprises three heat pump modules 130a, 130b, 130c. It should however be noted that, although not illustrated, the heat transfer arrangement 100 may comprise less than three heat pump modules 130a, 130b, 130c or more than three heat pump modules 130a, 130b, 130c. Each heat pump module 130a, 130b, 130c comprises first inlet and outlet ports 131a, 131b and second inlet and outlet ports 132b, 132a. The first inlet and outlet ports 131a, 131b are connected to the first inlet and outlet junction pipes 111, 112, respectively. The second inlet and outlet ports 132b, 132a are connected to the second inlet and outlet junction pipes 122, 121, respectively.

[0073] When the heat transfer arrangement 100 is in use, the three heat pump modules 130a, 130b, 130c are connected in parallel to each other. This is achieved by their respective first inlet and outlet ports 131a, 131b which are connected to the first inlet and outlet junction pipes 111, 112, respectively, and by their respective second inlet and outlet ports 132b, 132a which are connected to the second inlet and outlet junction pipes 122, 121, respectively.

[0074] Each heat pump module 130a, 130b, 130c further comprises a refrigerant recirculation loop 134. The refrigerant recirculation loop 134 comprises a first heat exchanger unit 135 and a second heat exchanger unit 137 as well as a compressor 136, and an expander 138. The aforementioned units 135, 136, 137 and 138 are connected to each other in series by means of a fluid conduit system 133 to define the refrigerant recirculation loop 134. The fluid conduit system 133 comprises tubing 139, 139' (see Figs 3 and 4). The tubing 139, 139' is typically made of a metal, such as cupper. The expander 134 may be an expansion valve, such as an electronic expansion valve, or a thermal expansion valve. Such an example embodiment will be further described later. The first heat exchanger unit 135 is fluidly connected to the first inlet and outlet ports 131a, 131b. Thus, the first heat exchanger 135 is connected to the first inlet and outlet junction pipes 111, 112 via the first inlet and outlet ports 131a, 131b, respectively. The second heat exchanger unit 137 is fluidly connected to the second inlet and outlet ports 132b, 132a. Thus, the second heat exchanger unit 137 is connected to the second inlet and outlet junction pipes 122, 121 via the second inlet and outlet ports 132b, 132a, respectively.

[0075] The refrigerant circulation loop 134 circulates a refrigerant through the first heat exchanger unit 135, the compressor 136, the second heat exchanger unit 137 and the expander 138. In the first heat exchanger unit 135, the refrigerant which is then predominately in a liquid phase and the cold side liquid are configured to exchange thermal energy between each other such that a temperature of the refrigerant increases, the refrigerant is vaporised into a gaseous phase and a temperature of the cold side liquid thereby decreases. The first heat exchanger unit 135 is therefore often termed: the "evaporator". The refrigerant is circulated from the first heat exchanger unit 135 via its heat exchanger refrigerant port 110b to the compressor 136 which is configured to increase the pressure and thereby temperature of the refrigerant before supplying the refrigerant to the second heat exchanger unit 137 via its heat exchanger refrigerant port 110d. In the second heat exchanger unit 137, the refrigerant which is still in a gaseous phase and the hot side liquid is configured to exchange thermal energy between each other such that a temperature of the refrigerant decreases and the refrigerant condenses into a liquid phase transferring thermal heat to the hot side first liquid which temperature is thereby increased. The second heat exchanger unit 137 is therefore often termed: the "condenser". The refrigerant is then circulated from the second heat exchanger unit 137 via its heat exchanger refrigerant port 110c to the expander 138 which is configured to reduce the pressure of the refrigerant. As the pressure drops, refrigerant starts to evaporate and the heat of evaporation is taken from the refrigerant itself which causes its temperature to drop and the result is a low-temperature, low-pressure mix of liquid and vapour which is then circulated into the first heat exchanger unit 135 via its heat exchanger refrigerant port 110a where the cycle starts over again.

[0076] As readily appreciated by the person skilled in the art, the refrigerant cycle may be reversed such that the refrigerant recirculation loop 134 flows counterclockwise instead of clockwise in Fig. 1A. The option of reversing the refrigerant cycle allows for the heat pump to be used both for cooling and heating a particular area. To allow reversing the refrigerant cycle, a valve system (not shown) is required to allow switching the inputs and outputs to the compressor 136. Such valve systems are well known in the art and therefore not further described herein.

[0077] Although not illustrated, it should be noted that the arrangement 100 may comprise one or more sensors, such as temperature sensors and / or pressure sensors, one or more control valves, such as check valves, one or more flow rate controllers, such as pumps etc. This is however also well known in the art and is therefore excluded from the figures in this context.

[0078] In addition to what have been discussed in connection with figure 1A, and as best illustrated in figure 1B, each of the heat pump modules 130a, 130b, 130c are removably arranged in the arrangement 100, or put differently, they may be detachable from the arrangement 100. Thus, as illustrated in Fig. 1B, it is possible to disconnect the heat pump module 130c from the first inlet and outlet junction pipes 111, 112 and from the second inlet and outlet junction pipes 122, 121 such that the heat pump module 130c may be removed from the arrangement 100. In this way, it is possible to remove or replace the heat pump module 130c if needed. Although not illustrated in Fig. 1B, all heat pump modules 130a, 130b, 130c of the arrangement may be removably arranged in the arrangement 100 or be detachable from the arrangement 100. The at least one modular liquid-liquid heat pump 130a, 130b, 130c may be a plurality of modular liquid-liquid heat pumps 130a, 130b, 130c operating in parallel.

[0079] Figures 2A and 2B illustrates a heat exchanger 200 according to an example embodiment of the disclosure. The heat exchanger 200 is suitable for use within the previously described heat transfer arrangement 100, within each of the heat pump modules 130a, 130b, 130c. Specifically, any one of the first heat exchanger units 135 and the second heat exchanger units 137 may be a heat exchanger 200. The heat exchanger 200 comprises a first heat exchanger refrigerant port 210a and a second heat exchanger refrigerant port 210b for fluidly connecting the heat exchanger 200 to a refrigerant recirculation loop 134 of the heat pump 130a, 130b, 130c. Each of the first and second heat exchanger refrigerant ports 210a, 210b has a respective interior volume 240a, 240b which extends into the heat exchanger 200 from a respective heat exchanger port opening end 212 towards a respective heat exchanger port bottom end 214 and fluidly connects to internal heat exchange channels 220 of the heat exchanger 200. This is illustrated schematically in Fig. 2B and in more detail in Figs 3 and 4.

[0080] The heat exchanger 200 is of a kind often termed plate heat exchanger and is constructed from a plurality of plate members 202a, 202b which are stacked on top of each other and then sealed with respect to each other, typically by brazing or by the provision of sealing members, such as gaskets, between adjacent plate members 202a, 202b. Each plate member 202a, 202b is provided with four port holes 204 and, optionally, a surface shape pattern 250 provided, e.g., by corrugation. Between each plate member 202a and an adjacent plate member 202b, a fluid channel 220, 221 will be formed. By designing the plate members 202a differently from the plate members 202b and stacking them in an alternating manner, or by designing the gaskets differently and providing these gaskets in an alternating manner, heat channels 220 and 221 will be provided in an alternating manner when the plurality of plate members 202a, 202b has been assembled. Heat channels 220, thus formed, will allow fluid communication between heat exchanger refrigerant port 210a and heat exchanger refrigerant port 210b. In the same manner, heat channels 221, thus formed, will allow fluid communication between heat exchanger secondary fluid port 215a having interior volume 245a and heat exchanger secondary fluid port 215b having interior volume 245b. The heat exchanger is provided with external connectors 230a and 230b for connecting the heat exchanger 200 to the refrigerant recirculation loop 134, and external connectors 235a and 235b for connecting the heat exchanger 200 to a secondary fluid, such as e.g., brine on the cold side or water on the hot side. The fluid motion within the heat exchanger 200 is illustrated schematically in Fig. 2A where black solid lines illustrate the motion of the secondary fluid through internal heat exchange channels 221, and the dotted lines illustrate the motion of the refrigerant through internal heat exchange channels 220. As readily appreciated by the person skilled in the art, the assembling in the stacked manner as described hereinabove will result in a plurality of overlapping port holes 204 at each corner of the heat exchanger 200. It is these overlapping port holes 204 which together defines the shape of a heat exchanger port, such as the heat exchanger refrigerant ports 210a and 210b.

[0081] It should be understood that the heat exchanger 200 is provided herein as an example, out of many, of a heat exchanger according to the disclosure. There are many alternative example embodiments of a heat exchanger than the one described with reference to Figs 2A and B which may have a heat exchanger refrigerant port 210a, 210b which extends into the heat exchanger from a refrigerant port opening end 212 towards a refrigerant port bottom end 214 and fluidly connects to internal heat exchange channels 220 of the heat exchanger, and the coupling device according to the disclosure is equally well applicable to any such alternative example embodiment of a heat exchanger.

[0082] A problem with heat exchangers such as the heat exchanger 200 of Figs 2A and B, is that the total volume of the heat exchanger refrigerant ports 210a, 210b tend to become quite large due to constructional constraints when manufacturing the heat exchanger 200. As can be seen in Fig. 2B, the heat exchanger refrigerant ports 210a, 210b may extend from one side to another opposite side of the heat exchanger. Moreover, the diameter of the port holes 204 may be quite large, typically 1.5-5 cm. The relatively large volumes of the heat exchanger refrigerant ports 210a, 210b may risk creating unnecessary volumes in the fluid conduit system which defines the refrigerant recirculation loop 134, hence requiring a larger total weight of refrigerant in order to completely fill the fluid conduit system 133 of the refrigerant recirculation loop 134. Moreover, the unnecessary volumes are shaped such that refrigerant may tend to accumulate there, thereby never effectively contributing to the heat transfer process. This is especially a problem where a narrower portion of the fluid conduit system of the refrigerant recirculation loop 134 mouths into a wider / larger volume.

[0083] To better appreciate this problem, Fig. 3 illustrates the heat exchanger refrigerant port 210a of the heat exchanger 200 connected to a refrigerant recirculation loop 134' according to the prior art (only a part of the refrigerant recirculation loop 134' is shown in Fig. 3). The refrigerant first passes a filter unit 340' in order to remove unwanted material, such as particles or the like, by mesh filter 342'. As clearly illustrated in Fig. 3, the filter unit 340' of the prior art has a substantially larger cross-sectional area as seen transverse to the refrigerant flow direction L than do the tubing 139' used to convey the refrigerant to the filter unit 140'. Apart from creating an unnecessarily large overall volume of the fluid conduit system 133' which defines the refrigerant recirculation loop 134', it also defines pockets where refrigerant may accumulate, thus providing pockets of stationary refrigerant which never contributes to the heat transfer process. This is schematically illustrated in Fig. 3 by stationary refrigerant pocket 30. Downstream of the filter unit 340', the refrigerant recirculation loop 134' comprises tubing 139' connecting to the heat exchanger refrigerant port 210a of the heat exchanger 200 via external connector 230a'. In a similar manner, the considerably larger cross-sectional area of the heat exchanger refrigerant port 210a, as seen transverse to the refrigerant flow direction L, than that of the tubing 139' used to convey the refrigerant thereto, results in yet another pocket of stationary refrigerant 32 at a bottom of the port interior volume 240a, which is defined herein as the entire interior volume of the heat exchanger refrigerant port 210a defined from the refrigerant port opening end 212 to the refrigerant port bottom end 214 and by the interior walls 211. Please note that the areas 30 and 32 in Fig. 3 are intended to mark volumes of stationary refrigerant. The white areas above areas 30 and 32 are also filled with refrigerant but this volume of refrigerant predominately flows through the system as indicated by the arrows and are thus are never accumulated. In a typical refrigerant recirculation loop of a heat pump filled with R290 as refrigerant, this stationary, and thereby passive, refrigerant, may be 15-20 gram, which may amount to as much as 10-15% of the total mass of the refrigerant in the refrigerant recirculation loop. The highest fractions are typically encountered for heat pumps, or heat pump modules, located in unventilated areas where the amount of allowed R290 currently is 152 g.

[0084] In order to reduce this problem, a coupling device is provided. This coupling device will be described in detail with reference to Figs 4 and 5A to 5F which illustrate one example embodiment: The coupling device 300.

[0085] The coupling device 300 is provided here for fluidly connecting a refrigerant recirculation loop of a heat pump to a heat exchanger refrigerant port of a heat exchanger. In the present example embodiment, the coupling device 300 is used to connect refrigerant recirculation loop 134 to heat exchanger refrigerant port 210a of heat exchanger 200 in any one of the heat pumps 130a, 130b and 130c. As mentioned earlier, the heat exchanger refrigerant port 210a defines a port interior volume 240a which extends into the heat exchanger 200 from a refrigerant port opening end 212 towards a refrigerant port bottom end 214 and fluidly connects to internal heat exchange channels 220 of the heat exchanger 200.

[0086] The coupling device 300 comprises a main body 310 which has an extension along a coupling device axis A. The coupling device 300 preferably has an axisymmetric geometry, such as e.g. a cylindrical geometry.

[0087] The main body 310 comprises an attachment portion 320 structured and arranged to be attachable to the heat exchanger 200 at the refrigerant port opening end 212. As can be seen in Fig. 4, the attachment portion 320 is for the example embodiment attached to external connector 230a of the heat exchanger refrigerant port 210a. The attachment may be achieved in many alternative ways. As a non-limiting example, the attachment may be realised by threaded engagement, which is the case for the example embodiment of Fig. 4 and Figs 5A to 5F. To this end, the attachment portion 320 has a threaded portion 324 (see Figs 5A and 5B) structured and arranged to be threadedly engageable with an associated threaded portion 213 (see Fig. 2B) of the heat exchanger 200 when attaching the coupling device 200 thereto. The attachment portion 230 further has a connecting port 322 for connecting to a fluid conduit system 133 of the refrigerant recirculation loop 134. The connecting port 322 is fluidly connected to an inner conduit line 312 provided within the attachment portion 320 for allowing fluid communication between the connecting port 322 and the distributing portion 330, which will be described in the next section. The connecting port 322 and the inner conduit line 312 may together form a through-bore, or through-hole. The connecting port 322 and the inner conduit line 312 may be aligned substantially in parallel with the coupling device axis A. The connecting port 322 is structured and arranged to receive tubing 139 of the fluid conduit system 133 of the refrigerant recirculation loop 134. A cross-sectional area A4 (see Fig. 5F) of the connecting port 322 is preferably larger than the cross-sectional area A1 (see Fig. 5E) of the inner conduit line 312. In a preferred embodiment, the cross-sectional area A4 of the connecting port 322 is dimensioned such that the cross-sectional area A1 of the inner conduit line 312 will match the cross-sectional area of fluid channel within the tubing 139 (see Fig. 4). The connecting port 322 may be manufactured e.g. by drilling. By providing a connecting port 322 having a diameter being only slightly larger than the diameter of the tubing 139, the tubing 139 may be attached to the connecting port 322 by soldering in a manner well known known in the art. For the example embodiment, the attachment portion 320 is integrally formed from one material. The attachment portion 320 can be made of a metal, such as e.g., steel, brass, stainless steel, or cupper.

[0088] The main body 310 further comprises a distributing portion 330 which has an elongated extension E1 from a first end 331 where it is configured to connect to the attachment portion 320, and a second end 332, opposite to the first end 331. The distributing portion 330 is made, at least in part, of a porous material configured to allow fluid transport therethrough. The distributing portion 330 may be made of a porous sintered metal, such as stainless steel, bronze, or nickel. As best illustrated in Fig. 4, when mounted in the heat exchanger 200, the inner conduit line 312 of the attachment portion 320 mouths at the first end 331 of the distributing portion 330 and thereby fluidly connects the refrigerant recirculation loop 134 to the distributing portion 330. As refrigerant is supplied to the distributing portion 330, it enters its porous material and is distributed within the same. The refrigerant subsequently leaves the distributing portion 330 via its exterior surfaces 333 and enters the clearance volume 350 which encloses the distributing portion 330. Once the refrigerant reaches the clearance volume 350, it will be able to flow within the same to subsequently enter the internal heat exchange channels 220 of the heat exchanger 200 which mouths into the clearance volume 350.

[0089] By providing a distributing portion 330 made, at least in part, of a porous material, the refrigerant which enters the distributing portion 330 via the inner conduit line 312 of the attachment portion 320 will be allowed to distribute three-dimensionally within the porous material to eventually leave the distributing portion 330 through its exterior surfaces 333. This may enhance mixing in the clearance volume 350, hence further reducing the risk of refrigerant accumulating therein.

[0090] For the coupling device 300, the clearance volume 350 is clearly indicated as non-zero, i.e. A2 < A3. For this reason, the clearance volume 350 effectively defines a flow channel between the exterior surfaces 333 of the distributing portion 330 and the interior walls 211 of the heat exchanger refrigerant port 210a. By design choice, the volume and shape of the clearance volume 350 may be chosen to further reduce the risk of any refrigerant accumulating. If some refrigerant nevertheless accumulates, the amount of such refrigerant is expected to be considerably reduced when compared to the prior art solution, as a result from the considerably reduced effective volume of the heat exchanger refrigerant port 210 as detailed hereinabove.

[0091] As readily appreciated by the person skilled in the art, the provision of the flow channel is not essential. In other words, the clearance volume 350 may be close to zero, or even zero. Thus, other not shown embodiments of the coupling device 300 may have a tight fit between the coupling device 300 and the heat exchanger refrigerant port 210a thus providing a very small, or even negligible, clearance volume 350 for defining a flow channel. For such embodiments the distribution of refrigerant to the respective internal heat exchange channels 220 of the heat exchanger 200 is effectively achieved internally within the porous material of the distributing portion 330.

[0092] Another advantage of the coupling device 300 is that the porous material of the distributing portion 330 provides natural filtering. In prior art systems, the filtering is usually carried out in a separate filtering device which is connected in series to the refrigerant recirculation loop, as described earlier. By the provision of the porous distributing portion 330, the refrigerant which passes the inner conduit line 312 of the attachment portion 320 will be allowed to pass the distributing portion 330 within the heat exchanger refrigerant port 210a to be filtered on its way towards the internal heat exchange channels 220 of the heat exchanger 200 where heat transfer subsequently takes place. Thus, a separate filtering device may not be required, thus providing a simplified and more cost effective solution.

[0093] The attachment portion 320 and the distributing portion 330 are connected to each other when mounted in the heat exchanger 200. The connection may be realised in different ways. The attachment portion 320 and the distributing portion 330 may be releasably attached to each other. As a non-limiting example, the attachment portion 320 and the distributing portion 330 may be separate elements which are attached to each other prior to being mounted in the heat exchanger 200, e.g. by soldering, gluing or welding. The attachment portion 320 and the distributing portion 330 may alternatively be non-releasably attached to each other. As a non-limiting example, the attachment portion 320 and the distributing portion 330 may be attached to each other prior to being mounted in the heat exchanger 200 by screwing or clamping (not shown). Alternatively, the attachment portion 320 and the distributing portion 330 may be made from one element.

[0094] The coupling device 300 of the disclosure should however not be construed as limited to the attachment portion 320 and the distributing portion 330 being connected to each other prior to being mounted inside the heat exchanger 200. For some embodiments, the attachment portion 320 and the distributing portion 330 are individual elements which are inserted one by one in the heat exchanger 200 and connected to each other first during assembly. As a non-limiting example, the distributing portion 330 may first be inserted to rest at its second end 332 against the interior walls 211 at the refrigerant port bottom end 214 of the heat exchanger refrigerant port 210a, 210b. In a second step, the attachment portion 320 may be inserted on top of the distributing portion 330 and, when being attached to the heat exchanger 200 at the refrigerant port opening end 212, the attachment portion 320 may be configured to exert a force onto the distributing portion 330 thereby clamping the distributor portion 330 between the interior walls 211 at the refrigerant port bottom end 214 of the heat exchanger refrigerant port 210a, 210b, and the attachment portion 320.

[0095] The heat exchanger refrigerant port 210a may be substantially cylindrically shaped. This implies that the flow channel which is formed between exterior surfaces 333 of the distributing portion 330 and interior walls 211 of the heat exchanger refrigerant port 210a may, at least in part, have the shape of a hollow cylinder. Other shapes are however conceivable. This flow channel is referred to herein as the clearance volume 350.

[0096] As best illustrated in Figs 4 and 5C, the coupling device 300 is structured and arranged such that, when mounted onto the heat exchanger 200, the coupling device 300 protrudes into the heat exchanger refrigerant port 210a from the refrigerant port opening end 212 towards the refrigerant port bottom end 214 such that the clearance volume 350 is not more than 20% of the port interior volume 240a. For the example embodiment, this will form a clearance volume 350 which may act as a flow channel for fluidly interconnecting the coupling device 300 with the internal heat exchange channels 200 of the heat exchanger 200. The clearance volume 350 will be formed, or defined, between exterior surfaces 333 of the distributing portion 330 and interior walls 211 of the heat exchanger refrigerant port 210a. As evident when comparing the prior art solution of Fig. 3 and the disclosed solution in Fig. 4, the clearance volume 350 will have a considerably smaller effective volume than the prior art solution in Fig. 3, since the latter corresponds to, at least nearly, the entire port interior volume 240a of the heat exchanger refrigerant port 210a. As illustrated in Fig 5C and 5D, the distributing portion 330 may have a cross-sectional area A2 being at least 95% of a cross-sectional area A3 of the heat exchanger refrigerant port 210a, as seen transverse to the coupling device axis A. The elongated extension E1 of the distributing portion 330 may be at least 95% of a longitudinal extension E2 of the clearance volume 350. As readily appreciated by the person skilled in the art, what has been detailed herein with reference to the heat exchanger refrigerant port 210a is equally applicable also for the heat exchanger refrigerant port 210b.

[0097] Figure 6A and 6B illustrate a coupling device 400 according to another example embodiment of the disclosure. The coupling device 400 is similar to the coupling device 300 already described in detail hereinabove, and like reference numbers marks like features and will not be further described here. The coupling device 400 differs from the coupling device 300 in that it further comprises an expansion valve 438 in direct attachment with the attachment portion 420. As can be seen in Fig. 6B, the connecting port 422 of the attachment portion 420 is shorter and structured and arranged to receive tubing 442. The connecting port 422 fluidly connects to inner conduit line 412. The expansion valve 438 is for the example embodiment an electrical expansion valve, but thermal expansion valves are also conceivable. The expansion valve 438 is only illustrated in part in Figs 6A and 6B. The person skilled in the art are well aware of how electrical expansion valves works, and expansion valve 438 is therefore only briefly described herein. The expansion valve 438 comprises a valve body 444 which is attached to the tubing 442 at the opposite end thereof. A displaceable shaft 448 is arranged axially within the valve body 444 and configured to be displaceable in order to control the size of the opening 450 formed between the expansion valve 438 and the tubing 442. Second tubing 446 is arranged in the valve body 444 to allow refrigerant to enter the expansion valve 438. The expansion valve 438 is directly attached to the attachment portion 420 by means of an attachment structure 440, in the example embodiment in the form of a steel ring. Attachment may be made by soldering, but other attachment means are also conceivable such as threaded attachments. As readily appreciated by the person skilled in the art, the coupling device 400 will constitute an integral component having both a filter and an expansion valve. This may simplify assembling of heat pumps since it reduces the number of individual components. Moreover, it may aid in further reducing unnecessary volumes in the fluid conduit system which houses the refrigerant recirculation loop. The person skilled in the art realises that for heat pumps having more than one coupling device, only one coupling device with integrated expansion valve may be needed per refrigerant recirculation loop 134.

[0098] Figure 7A and 7B illustrate a coupling device 300' according to another example embodiment of the disclosure. The coupling device 300' is similar to the coupling device 300 already described in detail with reference to Fig. 4 and Figs 5A to 5F, and like reference numbers marks like features and will not be further described here. The coupling device 300' differs from the coupling device 300 in that the distributing portion 330' further comprises an internal cavity 360 arranged concentrically within the distributing portion 330'. As illustrated in Fig. 7A, the internal cavity 360 meets and mouths into the inner conduit line 312 of the attachment portion 320 to provide direct fluid communication between the same. The internal cavity 360 extends along the coupling device axis A. The internal cavity may extend at least 70% of the elongated extension E1 of the distributing portion 330'. The internal cavity 360 may have a cross-sectional area A5 as seen transverse to the elongated extension E1 which is larger than the cross-sectional area A1 of the inner conduit line 312. The dimensions of the internal cavity 360 may however differ from what is described here.

[0099] Figure 8A to 8C illustrate a coupling device 300" according to another example embodiment of the disclosure. The coupling device 300" is similar to the coupling device 300' already described in detail with reference to Fig. 7A and 7B, and like reference numbers marks like features and will not be further described here. The coupling device 300" differs from the coupling device 300' in that the internal cavity 360" includes a plurality of internal cavity portions 362 which are fluidly connected to each other via central portion 361. An advantage of this embodiment may be to achieve an improved distribution of refrigerant within the distributing portion 330".

[0100] It is conceivable to provide a coupling device allowing for a smaller clearance volume. The coupling device 300, 400, 300', 300" may for example protrude into the heat exchanger refrigerant port 210a, 210b from the refrigerant port opening end 212 towards the refrigerant port bottom end 214 to form a clearance volume 350 between interior walls 211 of the heat exchanger refrigerant port 210a, 210b and exterior surfaces 333 of the distributing portion 330 being not more than 18%, or 16%, or 14%, or 10% or 8% or 6% or 4%, or 2% of the port interior volume 240a, 240b.

[0101] It is however also conceivable to have a larger clearance volume 350. As an example, the coupling device 300, 400, 300', 300" may protrude into the heat exchanger refrigerant port 210a, 210b from the refrigerant port opening end 212 towards the refrigerant port bottom end 214 to form a clearance volume 350 between interior walls 211 of the heat exchanger refrigerant port 210a, 210b and exterior surfaces 333 of the distributing portion 330 being not more than 50%, or 45%, or 40%, or 35% or 30% or 25% of the port interior volume 240a, 240b. Naturally, the risk of creating volumes of refrigerant which for different reasons is not contributing to heat transfer in the refrigerant recirculation loop 134 of the heat pump 130a, 130b, 130c may increase for increasing relative clearance volume 350. However, it is foreseen that some embodiments may need to have a somewhat larger clearance volume 350 than other embodiments for example because of manufacturing constraints and / or costs.

[0102] A coupling device of the disclosure may be provided together with a heat exchanger of the disclosure. Thus, for example, the coupling device 300 may be provided together with the heat exchanger 200. The two entities may be provided as a kit. This is illustrated in Fig. 4, which illustrate parts of the kit 500 which comprises heat exchanger 200 and coupling device 300. In other words, the kit 500 comprises a heat exchanger 200 which comprises first 210a and second 210b heat exchanger refrigerant ports for fluidly connecting the heat exchanger 200 to a refrigerant recirculation loop 134 of the heat pump 130a, 130b, 130c, wherein each of said first and second heat exchanger refrigerant ports 210a, 210b extends into the heat exchanger 200 from a respective heat exchanger port opening end 212 towards a respective heat exchanger port bottom end 214 and fluidly connects to internal heat exchange channels 220 of the heat exchanger 200, and a coupling device 300 being structured and arranged such that, when mounted onto the heat exchanger 200 at one of said first and second heat exchanger refrigerant ports 210a, 210b, the distributing portion 330 protrudes into said one of said first and second heat exchanger refrigerant ports 210a, 210b from its respective heat exchanger port opening end 212 towards its respective heat exchanger port bottom end 214 such that a clearance volume 350 interconnecting the inner conduit line 312 of the coupling device with the internal heat exchange channels 200 of the heat exchanger 200 is formed between exterior surfaces 333 of the distributing portion 330 and interior walls 211 of the heat exchanger refrigerant port 210a, 210b.

[0103] As readily appreciated by the person skilled in the art, the kit may comprise any heat exchanger unit and coupling device within the scope of the appended claims. For example, the kit may comprise the coupling device 400 together with the heat exchanger 200.

[0104] Turning yet again to Figs 1A and 1B, the features of the heat transfer arrangement 100 will be further described. As previously mentioned, the heat transfer arrangement 100 comprises at least one heat pump 130a, 130b, 130c, and one or more of said at least one heat pump 130a, 130b, 130c may comprise at least one coupling device 300 according to the disclosure. Put in other words, one or more of said at least one heat pump 130a, 130b, 130c may comprise at least one kit 500 according to the disclosure (Fig. 4). It is conceivable to provide a coupling device 300, 400 according to the disclosure for any one of the heat exchanger refrigerant ports 110a, 110b, 110c and 110d. However, the provision of the coupling device 300, 400 achieves the best effect when arranged at the side where the heat exchanger units 135, 137 are interconnected via the expander 138, i.e., at one or more of the heat exchanger refrigerant ports 110a and 110b. This is because the refrigerant is at least partly in liquid phase at this side of the refrigerant recirculation loop 134, and the benefit of reducing unnecessary volumes in the refrigerant recirculation loop 134 are therefore greater there than at the other side where the refrigerant is in in gaseous phase.

[0105] By the provision of the coupling device 200, 300, or the kit 500, a total volume of refrigerant contained in each of the at least one modular liquid-liquid heat pump 130a, 130b, 130c may be below 400 g, or below 300 g, or below 200 g. This may be beneficial because legislation puts restrictions to the amount allowed R290 refrigerant that may be used in one heat pump. Specifically, the amount allowed R290 refrigerant that may be used in a refrigerant recirculation loop is for one type of heat pumps currently 152 g without requirements on that the zone should be a ventilated area. The amount allowed R290 refrigerant in a refrigerant recirculation loop is for another type of heat pumps currently 334 g without requirements on that the zone should be a ventilated area. Other refrigerants may have different predetermined threshold-values.

[0106] The person skilled in the art realizes that the present disclosure by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed, from a study of the drawings, the disclosure, and the appended claims.

Claims

1. A coupling device (300, 400, 300', 300") for fluidly connecting a refrigerant recirculation loop (134) to a heat exchanger refrigerant port (210a, 210b) of a heat exchanger (200) in a heat pump (130a, 130b, 130c), wherein said heat exchanger refrigerant port (210a, 210b) defines a port interior volume (240a, 240b) which extends into the heat exchanger (200) from a refrigerant port opening end (212) towards a refrigerant port bottom end (214) and fluidly connects to internal heat exchange channels (220) of the heat exchanger (200), said coupling device having an extension along a coupling device axis (A) and comprising: an attachment portion (320) structured and arranged to be attachable to the heat exchanger (200) at the refrigerant port opening end (212), said attachment portion having a connecting port (322) for connecting to a fluid conduit system (133) of the refrigerant recirculation loop (134) and an inner conduit line (312) in fluid communication with the connecting port (322), and a distributing portion (330) which has an elongated extension (E1) along the coupling device axis (A) from a first end (331) to a second end (332), opposite to the first end (331), wherein the distributing portion (330) is made, at least in part, of a porous material configured to allow fluid transport therethrough, wherein the coupling device (300) is structured and arranged such that, when mounted onto the heat exchanger (200), the attachment portion (320) is connected to the distributing portion (330) at its first end (331) to allow fluid communication between the inner conduit line (312) and the distributing portion (330), and such that the coupling device (300) protrudes into the heat exchanger refrigerant port (210a, 210b) from the refrigerant port opening end (212) towards the refrigerant port bottom end (214) to form a clearance volume (350) between interior walls (211) of the heat exchanger refrigerant port (210a, 210b) and exterior surfaces (333) of the distributing portion (330) being not more than 20% of the port interior volume (240a, 240b).

2. The coupling device (300, 400, 300', 300") according to claim 1, wherein a cross sectional area (A2) of the distributing portion (330) as seen transverse to its elongated extension (E1) is substantially constant along the elongated extension (E1).

3. The coupling device (300, 400, 300', 300") according to claim 1 or 2, wherein a cross-sectional area (A2) of the distributing portion (330) as seen transverse to its elongated extension (E1) is at least 95% of a cross-sectional area (A3) of the heat exchanger refrigerant port (210a, 210b), as seen transverse to the coupling device axis (A).

4. The coupling device (300, 400, 300', 300") according to any one of claims 1 to 3, wherein the elongated extension (E1) of the distributing portion (330) is at least 95% of a longitudinal extension (E2) of the clearance volume (350).

5. The coupling device (300, 400, 300', 300") according to any one of claim 1 to 4, wherein the distributing portion (330) is made of a porous sintered metal, such as stainless steel, bronze, or nickel.

6. The coupling device (300, 400, 300', 300") according to any one of claim 1 to 5, wherein the connecting port (322) is structured and arranged to receive tubing (139) of the fluid conduit system (133) of the refrigerant recirculation loop (134), wherein a cross-sectional area (A4) of the connecting port is larger than the cross-sectional area (A1) of the inner conduit line (312).

7. The coupling device (300, 400, 300', 300") according to any one of claim 1 to 6, wherein the attachment portion (320) has a threaded portion (324) structured and arranged to be threadedly engageable with an associated threaded portion (213) of the heat exchanger (200) when attaching the coupling device thereto.

8. The coupling device (300, 400, 300', 300") according to any one of claim 1 to 7, wherein the distributing portion (330) has a shape which is geometrically complementary to the port interior volume (240a, 240b) of the heat exchanger refrigerant port (210a, 210b) of the heat exchanger (200).

9. The coupling device (400) according to any one of claim 1 to 8, wherein the coupling device further comprises an expansion valve (438) in direct attachment with the attachment portion (420).

10. The coupling device (300', 300") according to any one of claim 1 to 9, wherein the distributing portion has an internal cavity (360', 360") which meets and mouths into the inner conduit line (312) of the attachment portion (320) to provide direct fluid communication between the internal cavity (360', 360") and the inner conduit line (312).

11. A kit (500) for a heat pump (130a, 130b, 130c) comprising: a heat exchanger (200) which comprises first (210a) and second (210b) heat exchanger refrigerant ports for fluidly connecting the heat exchanger (200) to a refrigerant recirculation loop (134) of the heat pump (130a, 130b, 130c), wherein each of said first and second heat exchanger refrigerant ports (210a, 210b) defines a respective port interior volume (240a, 240b) which extends into the heat exchanger (200) from a respective heat exchanger port opening end (212) towards a respective heat exchanger port bottom end (214) and fluidly connects to internal heat exchange channels (220) of the heat exchanger (200), and a coupling device (300, 400, 300', 300") according to any one of the preceding claims being structured and arranged such that, when mounted onto the heat exchanger (200) at one of said first and second heat exchanger refrigerant ports (210a, 210b), the coupling device (300, 400) protrudes into said one of said first and second heat exchanger refrigerant ports (210a, 210b) from its respective heat exchanger port opening end (212) towards its respective heat exchanger port bottom end (214) to form a clearance volume (350) between interior walls (211) of the heat exchanger refrigerant port (210a, 210b) and exterior surfaces (333) of the distributing portion (330) being not more than 20% of the port interior volume (240a, 240b).

12. A heat transfer arrangement (100) for heating and / or cooling a building comprising at least one heat pump (130a, 130b, 130c), said heat transfer arrangement (100) comprising: at least one coupling device (300, 400, 300', 300") according to any one of claim 1 to 10, and / or at least one kit (500) according to claim 11.

13. The heat transfer arrangement (100) according to claim 12, wherein the at least one heat pump (130a, 130b, 130c) is at least one modular liquid-liquid heat pump (130a, 130b, 130c), wherein each of the at least one modular liquid-liquid heat pump (130a, 130b, 130c) is structured and arranged to be individually detachable from the heat transfer arrangement (100).

14. The heat transfer arrangement (100) according to claim 13, wherein the at least one modular liquid-liquid heat pump (130a, 130b, 130c) is a plurality of modular liquid-liquid heat pumps (130a, 130b, 130c) operating in parallel.

15. The heat transfer arrangement (100) according to claim 13 or 14, wherein a total mass of refrigerant contained in each of the at least one modular liquid-liquid heat pump (130a, 130b, 130c) is below 400 g, or below 300 g, or below 200 g.

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