EP4675202A1

EP4675202A1 - Heat pump with integrated heat exchanger and method of heating a heat sink fluid

Info

Publication number: EP4675202A1
Application number: EP24186538.5A
Authority: EP
Inventors: Johan Hedvall
Original assignee: Vanga Kyl & Vaermepumps Industri AB
Current assignee: Vanga Kyl & Vaermepumps Industri AB
Priority date: 2024-07-04
Filing date: 2024-07-04
Publication date: 2026-01-07
Also published as: WO2026008718A1

Abstract

There is provided a heat pump for heating a heat sink fluid by circulating a refrigerant, the heat pump comprising: a heat absorption stage configured to allow the refrigerant to absorb heat; a compressor configured to compress the refrigerant; a heat dissipation stage configured to dissipate heat from the refrigerant to the heat sink fluid; and a multi-pipe heat exchanger configured to provide heat transfer from refrigerant in the heat dissipation stage to refrigerant the heat absorption stage and to the heat sink fluid, wherein the multi-pipe heat exchanger comprises a first pipe and a second pipe, wherein the first pipe is arranged inside the second pipe such that the first and second pipes form an inner channel and a surrounding channel, wherein refrigerant in the heat absorption stage is configured to flow through the inner channel and refrigerant in the heat dissipation stage is configured to flow through the surrounding channel.

Description

TECHNICAL FIELD

The present invention relates to a heat pump, and in particular to a heat pump with a multi-pipe heat exchanger for facilitating heat transfer in the heat pump, and systems and methods for with the same.

BACKGROUND

Heat pumps are devices that transfer heat from a colder area to a warmer area and are widely used for heating and cooling applications in various industries and residential settings. These systems typically operate by circulating a refrigerant through a closed-loop refrigeration circuit where the refrigerant absorbs heat from a low-temperature source (e.g. the outside environment) and releases it to a high-temperature sink (e.g. inside the building), thereby providing heating or cooling as required.
Traditional heat pumps consist of four main components: an evaporator, a condenser, a compressor, and an expansion valve. These components work together to transfer heat from the heat source to the heat sink. Furthermore, heat pumps typically include one or more heat exchangers. The performance and structure of the heat exchanger(s) can significantly affect the efficiency and compactness of a heat pump system. The heat exchanger(s) facilitates the transfer of heat in the operating cycle of the heat pump. However, conventional heat exchangers are often bulky and require significant space for installation. Furthermore, the design and construction of these traditional heat exchangers can result in inefficiencies due to pressure drops, inadequate heat transfer rates, and difficulty in maintenance.
In recent years, various efforts have been made to improve the design and efficiency of heat exchangers within heat pump systems. Innovations have included the development of microchannel heat exchangers, which use multiple small channels to increase heat transfer surface area while minimizing material usage and reducing overall size. Despite these advancements, there remain significant challenges in optimizing the performance and efficiency of heat pumps, particularly in achieving a balance between compact size and high thermal efficiency.
There is, therefore, a need for an efficient heat pump system of compact size that addresses these challenges while enhancing overall system performance and reliability. Embodiments of the present invention thus seek to provide enhanced heat pumps, methods and other implementations that improve the scope and efficiency of heat pumps as well as providing new functionality and methods.

SUMMARY

The invention is defined by the appended independent claims. Additional features and advantages of the concepts disclosed herein are set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the described technologies. The features and advantages of the concepts may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the described technologies will become more fully apparent from the following description and appended claims, or may be learned by the practice of the disclosed concepts as set forth herein.
In a first aspect, there is provided a heat pump for heating a heat sink fluid by circulating a refrigerant, the heat pump comprising: a heat absorption stage configured to allow the refrigerant to absorb heat; a compressor configured to compress the refrigerant; a heat dissipation stage configured to dissipate heat from the refrigerant to the heat sink fluid; and a multi-pipe heat exchanger configured to provide heat transfer from refrigerant in the heat dissipation stage to refrigerant the heat absorption stage and to the heat sink fluid, wherein the multi-pipe heat exchanger comprises a first pipe and a second pipe, wherein the first pipe is arranged inside the second pipe such that the first and second pipes form an inner channel and a surrounding channel, wherein refrigerant in the heat absorption stage is configured to flow through the inner channel and refrigerant in the heat dissipation stage is configured to flow through the surrounding channel.
The heat transfer from the heat dissipation stage to the heat absorption stage increases the efficiency of the heat pump. This is achieved by the compact multi-pipe heat exchanger, thus reducing the size of the heat pump system, while also achieving efficient heat transfer to both the refrigerant in the heat absorption stage and to the heat sink fluid. Hence, the heat pump offers an efficient compact system while enhancing overall system performance and reliability
Optionally, the multi-pipe heat exchanger is configured to perform simultaneous heat transfer from the heat dissipation stage to the heat absorption stage and to the heat sink fluid.
Optionally, the multi-pipe heat exchanger is arranged to transfer heat to the heat sink fluid through a surface of the second pipe, optionally wherein the outer surface of the second pipe is configured to be surrounded by the heat sink fluid.
Optionally, the first and second pipes are concentric pipes such that the inner channel is a central channel, and the outer channel is an annular channel.
Optionally, the multi-pipe heat exchanger comprises a plurality of first pipes arranged inside the second pipe so as to form a plurality of inner channels.
Optionally, the multi-pipe heat exchanger is arranged in a tank configured to hold the heat sink fluid, such that the multi-pipe heat exchanger is submerged in heat sink fluid when the tank holds the heat sink fluid.
Optionally, the multi-pipe heat exchanger further comprises a third pipe arranged outside the second pipe so as to form a second surrounding channel, wherein the heat sink fluid is configured to flow through the second surrounding channel.
Optionally, the heat dissipation stage comprises an additional heat exchanger configured to provide heat transfer from the heat dissipation stage to the heat sink fluid, wherein the additional heat exchanger is arranged before the multi-pipe heat exchanger.
Optionally, the additional heat exchanger comprises a pipe configured to provide a refrigerant flow from the compressor to the multi-pipe heat exchanger, wherein the pipe of the additional heat exchanger is arranged in the tank so as to allow heat transfer from the refrigerant to the heat sink fluid.
In a second aspect, there is provided a heat pump system for heating a fluid, the system comprising: a heat pump according to the first aspect, and a tank configured to hold the heat sink fluid, wherein the multi-pipe heat exchanger of the heat pump is arranged in the tank and configured to be submerged in the fluid when the tank holds the heat sink fluid.
Optionally, the heat pump system further comprises: an additional tank for holding the heat sink fluid, wherein the additional tank comprises means for heating the heat sink fluid by solar power, a connecting circuit for circulating the heat sink fluid between the tank and the additional tank, and at least one valve arrangement for selectively allowing a heated fluid to flow from the tank and/or the additional tank to a fluid outlet.
Optionally, the heated fluid is the heat sink fluid.
Optionally, the heat pump system further comprises a tap water circuit comprising: a first tap water heat exchanger arranged in the tank, a second tap water heat exchanger arranged in the additional tank, and a fluid flow connection between an outlet of the second tap water heat exchanger and an inlet of the first tap water heat exchanger, wherein the valve arrangement is arranged to selectively allow heated tap water to flow from the tank and/or the additional tank to the fluid outlet.
Optionally, the system further comprises a control unit configured to: in dependence on a temperature of the fluid in the additional tank being below a threshold, allow the fluid to flow from the additional tank to the tank, and from the tank to the fluid outlet, and/or in dependence on the temperature of the fluid in the additional tank being above the threshold, allow the fluid from the additional tank to flow to the fluid outlet.
In a third aspect, there is provided a method of heating a heat sink fluid, the method comprising: compressing a refrigerant in a compressor of a heat pump; absorbing heat, in a heat absorption stage of the heat pump, to the refrigerant; transferring heat from refrigerant in a heat dissipation stage to refrigerant in the heat absorption stage and to the heat sink fluid, wherein the heat is transferred by a multi-pipe heat exchanger, wherein the refrigerant in the heat absorption stage flows through an inner channel of the multi-pipe heat exchanger and refrigerant in the heat dissipation stage flows through a surrounding channel of the multi-pipe heat exchanger. The heat pump may be a heat pump according to the first aspect.
In a fourth aspect, there is provided a heat pump system for heating a fluid, the system comprising: a first tank configured to hold heat sink fluid, a heat pump for heating the heat sink fluid in the first tank, a second tank for holding the heat sink fluid, means for heating the heat sink fluid in the second tank by solar power, a connecting circuit for allowing the fluid to flow from the second tank to the first tank, and at least one valve arrangement for selectively allowing the fluid to flow from the first tank and/or the second tank to a fluid outlet. The heat pump may be a heat pump according to the first aspect or any other suitable heat pump.
Optionally, the system further comprises a control unit configured to: in dependence on a temperature of the fluid in the second tank being below a threshold, allow the fluid to flow from the second tank to the first tank, and from the first tank to the fluid outlet, and/or in dependence on the temperature of the fluid in the second tank being above the threshold, allow the fluid from the second tank to flow to the fluid outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to best describe the manner in which the above-described embodiments are implemented, as well as define other advantages and features of the disclosure, a more particular description is provided below and is illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the invention and are not therefore to be considered to be limiting in scope, the examples will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

Fig. 1a: shows a schematic view of a heat pump according to embodiments;
Fig. 1b: shows a schematic view of a heat pump according to embodiments;
Fig. 2: shows a temperature-entropy diagram of an operating cycle of a heat pump according to embodiments;
Fig. 3a: shows a perspective view of a multi-pipe heat exchanger according to embodiments;
Fig. 3b: shows a cross-section of a multi-pipe heat exchanger according to embodiments;
Fig. 4: shows a schematic view of a heat pump system according to embodiments;
Fig. 5a: shows a perspective view of a multi-pipe heat exchanger according to embodiments;
Fig. 5b: shows a cross-section of a multi-pipe heat exchanger according to embodiments;
Fig. 6: shows a flowchart of a method of operating a heat pump according to embodiments; and
Fig. 7: shows a schematic view of a heat pump system according to embodiments.

Further, in the figures like reference characters designate like or corresponding parts throughout the several figures. The first digit in the reference character denotes the first figure in which the corresponding element or part appears.

DETAILED DESCRIPTION

Various embodiments of the disclosed methods and arrangements are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components, configurations, and steps may be used without parting from the spirit and scope of the claimed invention.
Hereinafter, certain embodiments will be described more fully with reference to the accompanying drawings. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the inventive concept. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice disclosed herein. It is to be understood that elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed or omitted, certain features may be utilized independently, and embodiments or features of embodiments may be combined, all as would be apparent to the skilled person in the art.
The embodiments herein are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept, and that the claims be construed as encompassing all modifications, equivalents and alternatives of the present inventive concept which are apparent to those skilled in the art to which the inventive concept pertains. If nothing else is stated, different embodiments may be combined with each other.
Although reference may be made to directions (e.g. left, right, up, down, upper, lower) as shown in the figures, it will be appreciated that these references are purely for illustrative purposes, and that embodiments are not limited to such directions.
Figs. 1 and 2 show a heat pump 100 according to embodiments. Figs. 1a and 1b show schematic views of heat pumps 100 according to embodiments, while Fig. 2 shows a temperature-entropy diagram of the heat pump 100. In Fig. 2, the thick solid line indicates the operating cycle of the heat pump 100 while the thin, solid line indicates the saturation line for the refrigerant. Furthermore, the numbers 1 to 4 in Figs. 1 and 2 indicate corresponding locations in the heat pump cycle.
The heat pump 100 may be a heat pump for a residential building such as a house or apartment. The heat pump 100 may thus be configured to heat the building and/or to heat water (e.g. tap water) for use in said building.
The heat pump 100 may be defined as a device that uses work to transfer heat (i.e. thermal energy) to a heat sink 102 (such as a warm fluid used to heat the building) using a closed-loop refrigeration circuit.
To achieve the required transfer, a refrigerant is used which is circulated through the refrigeration circuit. The refrigerant is a fluid with appropriate thermodynamic properties allowing the heat pump 100 to have a net output of thermal energy. The refrigerant may also be referred to as a working fluid of the heat pump 100 and/or refrigeration circuit. Hence, the heat pump 100 may also be referred to as a vapor-compression refrigeration system.
The refrigerant may be a hydrocarbon refrigerant. For example, the refrigerant may comprise difluoromethane, propane and/or isobutane (C₄H₁₀). In particular, the refrigerant may comprise R32 refrigerant, R600a refrigerant and/or R290 refrigerant.
Similarly to known heat pumps, the heat pump 100 according to embodiments comprises a compressor stage 103, a heat dissipation stage 104, a throttle stage 105, and a heat absorption stage 106. The compressor stage 103, heat dissipation stage 104, throttle stage 105, and heat absorption stage 106 typically form part of a closed-loop refrigeration circuit or cycle.
The compressor stage 103, the heat dissipation stage 104, the throttle stage 105, and the heat absorption stage 106 are connected in series. That is, the components of the heat pump 100 are arranged such that, in the flow direction, the heat absorption stage 106 is connected after the throttle stage 105, which in turn is connected after the heat dissipation stage 104 which in turn is connected after the compressor stage 103 which in turn is connected after the heat absorption stage 106.
In particular, an outlet of the compressor stage 103 may be connected (i.e. fluidly connected) to an inlet of the heat dissipation stage 104 (at point 2). An outlet of the heat dissipation stage 104 may be connected to an inlet of the throttle stage 105 (at point 3). An outlet of the throttle stage 105 may be connected to an inlet of the heat absorption stage 106 (at point 4). An outlet of the heat absorption stage 106 may be connected to an inlet of the compressor stage 101 (at point 1).
It will be appreciated that the terms "connected" and/or "fluidly connected" may include, but are not limited to, a direct connection. In other words, the terms "connected" and/or "fluidly connected" may or may not encompass connections which include some form of connecting means and/or intermediate device or structure, such as one or more pipes or other components provided between the two connected components.
In the heat absorption stage 106, the refrigerant is configured to absorb heat, e.g. from the heat source 101 as indicated by the arrow denoted Q in Fig. 1. In other words, heat (i.e. thermal energy) is transferred to the refrigerant, e.g. from the heat source 101. The heat absorption may be substantially isobaric.
The heat absorption includes an enthalpy increase of the refrigerant, for example the heat absorption may cause a vaporisation and/or temperature of the refrigerant to increase. The heat absorption stage 106 may thus form or include an evaporator. That is, the heat absorption stage 106 may be configured to at least partially evaporate the refrigerant. It is however noted that the heat absorption does not necessarily include a temperature increase of the refrigerant, as the absorbed heat may instead be "used" to at least partially vaporise the refrigerant. Accordingly, at least part of the heat absorption may be performed at substantially constant temperature (as shown in Fig. 2).
The heat absorption stage 106 may be configured to absorb heat from the heat source 101 which may be formed by ambient air. Air is available almost everywhere, it is inexpensive, and heat can be extracted from it using a conventional outside unit of a heat pump. Hence, embodiments may include an outside unit (e.g. a conventional outside unit) forming part of the heat pump 100, and in particular the heat absorption stage 106 that is configured to transfer heat from the ambient air to the heat absorption stage. Alternatively, or additionally, the heat transfer from the heat source 101 to the refrigerant in the heat absorption stage 106 may be performed using any suitable means, mechanism, structure, device, or the like, that allows heat transfer between the refrigeration circuit and the heat source and/or heat sink respectively. For example, there may be provided one or more heat exchangers 110 for performing said heat transfer, for instance one or more co-flow and/or counter-flow heat exchangers. It will be understood that an outside unit may be part of or form the heat exchanger 110.
The heat absorption stage 106 may alternatively or additionally be configured to absorb heat from the high-temperature refrigerant in the heat dissipation stage 104. Hence, the heat pump 100 may include an integrated heat exchanger 108 for transferring heat from the heat dissipation stage 104 to the heat absorption stage 106.
Embodiments may include both the integrated heat exchanger 108 for absorption of heat from the heat dissipation stage 104 and the heat exchanger 110 (e.g. an outside unit) for absorption of heat from ambient air or other heat source 101, as shown in Fig. 1a. However, the heat exchanger 110 may be optional as indicated by the dashed line in Fig. 1b. Hence, the heat absorption stage may only include the integrated heat exchanger 108. In such case, the integrated heat exchanger 108 may be directly connected to throttle stage 105 on both the high-pressure and low-pressure side.
Although the heat exchanger 110 is shown in Fig. 1a to be arranged before the integrated heat exchanger 108, embodiments include a heat exchanger 110 that is alternatively or additionally arranged after the integrated heat exchanger 108, e.g. between the integrated heat exchanger 108 and the compressor stage 103.
Although, the refrigerant is shown as superheated when leaving the heat absorption stage 106 in Fig. 2, it will be appreciated that the refrigerant must not be superheated. For example, the refrigerant may instead be saturated gas when leaving the heat absorption stage 106.
After leaving the heat absorption stage 106, the gaseous refrigerant is compressed in the compressor stage 103 so as to increase the pressure (and temperature) of the refrigerant. Hence, the compressor stage 103 may comprise one or more compressors configured to compress the refrigerant. Accordingly, an energy input (i.e. a work input) to the refrigerant is provided by the compressor stage 103, as indicated by the arrow denoted W in Fig. 1. The compression in the compressor stage 103 may be close to isentropic.
After the refrigerant has been compressed in the compressor stage 103, the refrigerant enters the heat dissipation stage 104. The heat dissipation stage 104 is configured to dissipate heat from the refrigerant, e.g. by transferring heat from the refrigerant to the heat sink 102. In other words, heat (i.e. thermal energy) is transferred from the refrigerant to the heat sink 102. The heat dissipation may be substantially isobaric.
The heat dissipation includes an enthalpy decrease of the refrigerant, for example the heat dissipation may cause the refrigerant to at least partially condense and/or cause a temperature of the refrigerant to decrease. The heat dissipation stage 104 may thus form or include a condenser. It is however noted that at least part of the heat dissipation does not necessarily cause a temperature decrease of the refrigerant, as the dissipation of heat may instead be "used" to at least partially condense the refrigerant. Accordingly, at least part of the heat dissipation may be performed at substantially constant temperature (as shown in Fig. 2).
The heat transfer from the refrigerant in the heat dissipation stage 104 to the heat sink 102 may be performed using any suitable means, mechanism, structure, device, or the like, that allows heat transfer between the refrigeration circuit and the heat source and/or heat sink respectively. For example, there may be provided one or more heat exchangers (e.g. co-flow and/or counter-flow heat exchangers) for performing said heat transfer, for instance an integrated heat exchanger 108 as will be described later and/or a supplementary heat exchanger 111 (which may be in the form of a conventional heat exchanger).
The heat sink 102 may comprise a fluid (e.g. liquid and/or gas) to be heated, such as water. The fluid to be heated may thus be referred to as a heat sink fluid 107. Hence, the heat dissipation stage 104 is configured to heat the heat sink fluid 107. For example, the heat pump 100 may be connected to a tank 109 configured to hold the heat sink fluid 107. Once the heat sink fluid 107 has been heated, the heated fluid may be used in various applications, for example, the heat sink fluid 107 may be used for central or communal heating (e.g. in radiators) and/or hot water supply (e.g. tap water).
Once the refrigerant has been condensed and/or cooled in the heat dissipation stage 104, the refrigerant enters the throttle stage 105 which is configured to reduce the pressure of the refrigerant, e.g. by expanding the refrigerant. Accordingly, the throttle stage 105 may comprise pressure reducing means and/or refrigerant expansion means. In particular, the throttle stage 105 may include one or more throttles, expansion valves, orifices, constrictions, or any other suitable means for reducing the pressure of the refrigerant.
The pressure reduction typically also causes a temperature of the refrigerant to be reduced. The pressure reduction may be substantially isenthalpic. Accordingly, the refrigerant is throttled, expanded, and cooled when flowing through the throttle stage 105.
Once a pressure of the refrigerant has been reduced in the throttle stage 105, the refrigerant flows into the heat absorption stage 106 and the above-described cycle or process is repeated.
In addition to the above-described components, the heat pump further comprises an integrated heat exchanger 108 configured to provide heat exchange between the heat dissipation stage 104 and the heat absorption stage 106. In particular, the integrated heat exchanger 108 may facilitate heat transfer from the high-pressure, high-temperature refrigerant in the heat dissipation stage 104 to the low-pressure, low-temperature refrigerant in the heat absorption stage 106.
Preferably, the integrated heat exchanger 108 is arranged to provide (i) said heat transfer from the heat dissipation stage 104 to the heat absorption stage 106, and (ii) heat transfer from the heat dissipation stage 104 to the heat sink 102. In other words, the integrated heat exchanger 108 may be configured to provide heat transfer from the heat dissipation stage 104 to both the heat absorption stage 106 and the heat sink 102. The heat transfer from the heat dissipation stage 104 to both the heat absorption stage 106 and the heat sink 102 may be simultaneous. This may be achieved, for example, with an integrated heat exchanger 108 in the form of a multi-pipe heat exchanger as described in relation to Figs. 3 to 5.
The integrated heat exchanger 108 may cause the refrigerant in the heat absorption stage 106 to superheat, that is to be heated above its saturation temperature. For example, the low-pressure refrigerant entering the integrated heat exchanger 108 may be saturated (i.e. the refrigerant has been fully vaporized by absorption of heat from the heat source 101) such that the heat transfer from the heat dissipation stage 104 which is facilitated by the integrated heat exchanger 108 increases the temperature of the refrigerant above the saturation temperature.
By superheating the refrigerant, it can be ensured that no liquid refrigerant enters the compressor stage 103, thus ensuring that the performance of the compressor is not impacted by liquid droplets. Furthermore, the superheating increases the efficiency of the heat pump 100.
Alternatively, or additionally, the integrated heat exchanger 108 may contribute to the evaporation or vaporization of the refrigerant. In other words, the refrigerant entering the integrated heat exchanger 108 may not be fully vaporized.
Although there is shown in Fig. 1a, a supplementary heat exchanger 111 arranged before the integrated heat exchanger 108, it will be appreciated that embodiments are not limited to a heat pump 100 with such a supplementary heat exchanger 111. For example, embodiments include heat pumps 100 without a supplementary heat exchanger 111 where the heat transfer to the heat sink 102 is fully performed by the integrated heat exchanger 108. As another example, embodiments also include heat pumps 100 where the supplementary heat exchanger 111 is arranged after the integrated heat exchanger 108.
The refrigerant in the heat dissipation stage 104 may be at a pressure of about 10 to 35 bar, optionally about 13 to 30 bar, optionally about 15 to 25 bar, optionally about 18 to 22 bar. The refrigerant in the heat absorption stage 106 may be at a pressure of about 2 to 20 bar, optionally about 4 to 16 bar, optionally about 6 to 14 bar, optionally about 8 to 12 bar.
Figs. 3a to 3d show embodiments of the integrated heat exchanger 108 where the integrated heat exchanger 108 is a multi-pipe heat exchanger. In particular, Figs. 3a and 3b show a first embodiment of the multi-pipe heat exchanger in perspective view and end (or cross-sectional) view respectively, while Figs. 3c to 3d show a second embodiment of the multi-pipe heat exchanger in perspective view and end (or cross-sectional) view respectively.
The multi-pipe heat exchanger 108 comprises at least two pipes or tubes, i.e. at least a first pipe 301 and a second pipe 302. The two pipes may be arranged such that the first pipe 301, which has a smaller diameter, is inside and extends through the second pipe 302. The first pipe 301 may thus be referred to as an inner pipe, and the second pipe 302 may thus be referred to as a surrounding pipe. Hence, the two pipes form two separate channels for fluid flow, namely an inner channel 303 within the first pipe 301 and a surrounding channel 304 (or outer channel) between the two pipes (i.e. in a space outside the first pipe 301 but inside the second pipe 302).
The first and second pipes may be concentric pipes, as shown in Figs. 3a and 3b. In other words, the multi-pipe heat exchanger may comprise two or more concentric pipes. Hence, the inner channel 303 may be a central channel and the surrounding channel 304 may be an annular channel.
The multi-pipe heat exchanger may alternatively or additionally comprise a plurality of inner pipes 301, as can be seen in Figs. 3c and 3d. For example, the multi-pipe heat exchanger may comprise 2, 3, 4, or more inner pipes 301. Each inner pipe may define or form a respective inner channel 303.
Although reference will hereafter be made generally to a multi-pipe heat exchanger, it is appreciated that embodiments are not limited to such a multi-pipe heat exchanger but can include any suitable integrated heat exchanger 108.
The multi-pipe heat exchanger 108 may be arranged in the heat pump 100 such that the inner channel 303 (or the plurality of inner channels 303) forms part of the heat absorption stage 106 and the surrounding channel 304 forms part of the heat dissipation stage 104. In other words, the multi-pipe heat exchanger 108 is arranged such that refrigerant in the heat absorption stage 106 is configured to flow through the inner channel 303 and refrigerant in the heat dissipation stage 104 is configured to flow through the surrounding channel 304. Hence, the inner channel 303 may be connected between the outlet of the throttle stage 105 and the inlet of the compressor stage 103, while the surrounding channel 304 may be connected between the outlet of the compressor stage 103 and the inlet of the throttle stage 105.
The first pipe 301 (i.e. the inner pipe) is made from a material that is thermally conductive so as to allow heat transfer from the refrigerant flowing through the surrounding channel 304 to the refrigerant flowing through the inner channel 303. For example, the first pipe 301 may be made from metal such as copper. Hence, the multi-pipe heat exchanger 108 facilitates heat transfer from the refrigerant in the heat dissipation stage 104 to the refrigerant in the heat absorption stage 106.
The multi-pipe heat exchanger 108 may be connected such that the refrigerant flowing through the inner channel 303 and the refrigerant flowing through the surrounding channel 304 is in counterflow. Alternatively, the flow may be co-directional flow.
The second pipe 302 is configured to be surrounded by the heat sink fluid 107 so as to facilitate heat transfer from the refrigerant flowing through the surrounding channel 304 to the heat sink fluid 107 surrounding the second pipe 302. Hence, the second pipe 302 (i.e. the pipe around the surrounding channel 304) is preferably also made from a material that is thermally conductive so as to allow heat transfer from the refrigerant flowing through the surrounding channel 304 to the heat sink surroundings. For example, the second pipe 302 may be made from metal such as copper.
Preferably, at least a portion of the outer surface of the second pipe 302 is configured to be in direct contact with the heat sink fluid 107. For instance, the outer surface of the second pipe 302 may, in use, be completely covered or submerged in heat sink fluid 107.
Accordingly, the multi-pipe heat exchanger 108 can provide simultaneous heat transfer from the heat dissipation stage 104 to both the heat absorption stage 106 and the heat sink fluid 107.
Fig. 4 shows a heat pump system 400 according to embodiments. The heat pump system 400 comprises a heat pump 100 as previously described with a multi-pipe heat exchanger 108 as previously described. Furthermore, the heat pump system 400 comprises one or more tanks 109 for holding the heat sink fluid 107 that is to be heated by the heat pump 100.
The multi-pipe heat exchanger 108 is arranged in the tank 109 such that, when the tank 109 is filled with heat sink fluid 107, the multi-pipe heat exchanger 108 (and in particular the outer surface of the second pipe 302) is at least partially, and preferably fully, submerged in the heat sink fluid 107. Hence, the heat sink fluid 107 can be heated by the high-temperature refrigerant flowing through the surrounding channel 304 of the multi-pipe heat exchanger 108. The pipes of the multi-pipe heat exchanger 108 may be arranged in a winding manner, e.g. to form bent tubes, a zig-zag shape, a rectangular wave-shape, a spiral shape, or the like, to increase the surface area through which heat transfer can occur. Although the surrounding channel 304 and the inner channel 303 are shown as counterflow in Fig. 4, it will be appreciated that embodiments also include a multi-pipe heat exchanger 108 with co-flow between the surrounding channel 304 and inner channel 303.
In addition to the multi-pipe heat exchanger 108 there may be provided a supplementary heat exchanger 111 as part of the heat dissipation stage 104 of the heat pump 100. The supplementary heat exchanger 111 may also be arranged in the tank 109, e.g. before and/or above the multi-pipe heat exchanger 108.
The supplementary heat exchanger 111 may be formed of one or more pipes through which the refrigerant in the heat dissipation stage 104 flows. The one or more pipes may be arranged in a winding manner, e.g. to form bent tubes, a zig-zag shape, a rectangular wave-shape, a spiral shape, or the like, to increase the surface area through which heat transfer can occur.
A connection means may be provided between the pipe of the supplementary heat exchanger 111 and the pipes of the multi-pipe heat exchanger 108. In particular, the connection means may be configured to connect the pipe of the supplementary heat exchanger 111 with the surrounding channel 304 of the multi-pipe heat exchanger 108 such that the refrigerant in the heat dissipation stage 104 can flow from the supplementary heat exchanger 111 to the surrounding channel 304. Furthermore, the connection means may connect the inner channel 303 of the multi-pipe heat exchanger 108 to the heat absorption stage 106 of the heat pump 100.
Although it is shown in Fig. 4 that an input to the inner channel 303 is connected to the throttle stage 105, it will be appreciated that this connection may be via one or more heat exchangers 110 configured to transfer heat from the heat source 101 (e.g. in an outside unit of the heat pump 100).
The heat dissipation stage 104 may have an inlet provided at or near the top of the tank 109 and an outlet provided at or near the bottom of the tank 109, such that the refrigerant flows through the heat dissipation stage 104 generally downwards in the tank 109. Thus, the hottest refrigerant (i.e. before any heat has been dissipated from it) comes into contact with heat sink fluid 107 near the top of the tank 109 where the heat sink fluid 107 is generally the warmest (due to density differences due to the temperature of the heat sink fluid 107) thus increasing the efficiency of the heat transfer. Hence, a supplementary heat exchanger 111 arranged before the multi-pipe heat exchanger 108 is generally located above the multi-pipe heat exchanger 108 in the tank 109.
Accordingly, the heat dissipation stage 104 of the heat pump 100 is generally arranged in the tank 109, while the remaining stages of the heat pump 100 may be arranged outside of the tank 109 (and are therefore not shown in Fig. 4).
The heat pump system 400 may be connected to one or more circuits for utilizing the heated heat sink fluid 107. For example, the heat pump system 400 may be connected to a radiator circuit 403 and/or a tap water circuit 404.
The radiator circuit 403 is configured to distribute the heated heat sink fluid 107 to one or more radiators 405, underfloor heating systems, and/or other heating elements of a building. The radiator circuit 403 may be connected directly to the tank 109 such that it can draw heated heat sink fluid 107 from the tank 109 and return cooled-down heat sink fluid 107 to the tank 109. In other words, the radiator fluid used in the radiator circuit 403 may be the heat sink fluid 107.
The tap water circuit 404 is configured to distribute warm or hot tap water in the building, e.g. to water taps, showers, appliances requiring hot water, or the like (not shown). The tap water circuit 404 may be isolated from the radiator circuit 403 and/or the heat sink fluid 107. That is, the water in the tap water circuit 404 may not come into direct contact with the fluid in the radiator circuit 403 and/or the heat sink fluid 107. Therefore, the tap water circuit 404 may comprise a tap water heat exchanger 406 arranged in the tank 109 (or otherwise configured to transfer heat from the heat sink fluid 107 to the tap water) such that the tap water is indirectly heated by the heat sink fluid 107. In other words, the heat pump 100 is configured to heat the heat sink fluid 107 which in turn heats the water in the tap water circuit 404. The tap water heat exchanger 406 may be any conventional heat exchanger, for example comprising one or more pipes arranged in the tank 109, e.g. in a winding manner as shown in Fig. 4.
It will be appreciated that the radiator circuit 403 and/or the tap water circuit 404 may comprise one or more pumps or other conventional components typically used in such circuits, as will be within the capabilities of the person skilled in the art.
The heat pump system 400 may further comprise a control unit (not shown) for operation of the heat pump 100, the radiator circuit 403 and/or the tap water circuit 404. Additionally, or alternatively, the heat pump system 400 may comprise one or more temperature sensors (e.g. arranged in the tank 109, in the radiator circuit 403 and/or the tap water circuit 404) configured to measure a fluid temperature (e.g. of the heat sink fluid 107, the fluid in the radiator circuit 403 and/or the water in the tap water circuit 404), so as to inform the control unit and/or a user of said temperature.
Fig. 5 shows an alternative embodiment of the multi-pipe heat exchanger 108 in which the multi-pipe heat exchanger 108 comprises a further surrounding pipe 501.
The two inner pipes 301, 302 of the multi-pipe heat exchanger 108 are substantially similar or identical to the previous multi-pipe heat exchanger 108 described in relation to Fig. 3. In addition to these two pipes 301, 302, the multi-pipe heat exchanger 108 may comprise a third (outer) pipe 501 arranged outside the first and second pipes 301, 302. The third pipe 501 may be concentric with the first and second pipes 301, 302. Accordingly, a second (or outer) surrounding channel 502 is formed between the second pipe 302 and third pipe 501. In the case of concentric third pipe 501, the second surrounding channel 502 may also be referred to as a second annular channel.
Although the third pipe 501 is shown in Fig. 5 in combination with the concentric first and second pipes of Figs. 3a and 3b, it will be appreciated that embodiments may equally combine the third pipe 501 with the plurality of first pipes and the surrounding second pipe as shown in Figs. 3c and 3d.
The outer surrounding channel 502 is configured to facilitate a flow of heat sink fluid 107. That is, heat sink fluid 107 is intended to flow through the outer surrounding channel 502 and thus completely cover the outside surface of the second pipe 302. Hence, heat may be transferred from the refrigerant in the inner surrounding channel 304 to the heat sink fluid 107 flowing through the outer surrounding channel 502. Such an arrangement may be advantageous if the heat pump system 400 does not comprise a tank 109 for holding the heat sink fluid 107 and/or if the multi-pipe heat exchanger 108 cannot be arranged in the tank 109 so as to be submerged in the heat sink fluid 107.
The three-pipe multi-pipe heat exchanger 108 may be arranged in a winding manner, e.g. to form bent tubes, a zig-zag shape, a rectangular wave-shape, a spiral shape, or the like, to increase the surface area through which heat transfer can occur.
Fig. 6 shows a method of operating a heat pump 100 according to embodiments. The heat pump 100 may be a heat pump 100 as previously described.
In step 601, the refrigerant is compressed. The compression may be performed by a compressor stage 103 of the heat pump 100.
In step 603, the refrigerant absorbs heat. The heat absorption may be preformed in a heat absorption stage 106 of the heat pump 100, e.g. via one or more heat exchangers. The heat exchange may be performed at least partially by a multi-pipe heat exchanger 108.
In step 605, heat is dissipated from refrigerant in the heat dissipation stage 104 to both refrigerant in the heat absorption stage 106 and to the heat sink fluid 107. Preferably, at least part of the heat transfer to both refrigerant in the heat absorption stage 106 and to the heat sink fluid 107 is simultaneous, i.e. happening at the same time. The heat may be transferred by an integrated heat exchanger 108, such as a multi-pipe heat exchanger 108. In the multi-pipe heat exchanger 108, the refrigerant in the heat absorption stage 106 may be configured to flow through an inner channel 303 and refrigerant in the heat dissipation stage 104 may be configured to flow through a surrounding channel 304.
The method may further comprise dissipating heat from the refrigerant in the heat dissipating stage 104 to the heat sink fluid 107 by one or more supplementary heat exchangers 111.
Fig. 7 shows another embodiment of a heat pump system 400 according to embodiments. The heat pump system 400 may be a heat pump system 400 as described in relation to Fig. 4, but further comprising at least one additional tank for holding heat sink fluid 107. In other words, the heat pump system 400 may comprise a first tank 109 (corresponding to the previously described tank 109) and a second tank 701.
The heat sink fluid 107 in the second tank 701 may be heated from solar power. In particular, the heat sink fluid 107 in the second tank 701 may be indirectly heated from solar power. For example, the heat pump system 400 may comprise one or more solar collectors 702 configured to actively heat a fluid circulating in an intermediate circuit 703. The heated fluid may then flow through a heat exchanger 704 (e.g. arranged in the second tank 701) where heat is transferred to the heat sink fluid 107 in the second tank 701. As another example, the heat sink fluid 107 in the second tank 701 may be heated by one or more electrically powered heating elements that are powered by solar generated electricity. In such a case, the heat pump system 400 may comprise one or more solar panels for generating said electricity.
Alternatively, the heat sink fluid 107 in the second tank 701 may be directly heated from solar power. For example, the heat sink fluid 107may be circulated through the one or more solar collectors 702.
The second tank 701 may be connected to the first tank 109 by one or more fluid circuits and/or valve arrangements.
In particular, there may be provided a connecting circuit for circulating heat sink fluid 107 between the first tank 109 and the second tank 701. The connecting circuit may comprise a feed line 705 (optionally provided with a pump 706) for pumping heat sink fluid 107 from the first tank 109 to the second tank 701, and a return line 707 for allowing a flow of heat sink fluid 107 from the second tank 701 back to the first tank 109.
The radiator circuit 403 (as previously described in relation to Fig. 4) may be connected to both the first tank 109 and the second tank 701. Hence, hot radiator fluid (e.g. hot heat sink fluid 107) may be taken from either or both of the first and second tanks. The radiator circuit 403 may accordingly comprise a radiator circuit valve 708 for selecting if the hot radiator fluid is coming from the first tank 109 and/or the second tank 701. In particular, a first radiator feed line 709 may be provided from the first tank 109 to the radiator circuit valve 708, and a second radiator feed line 710 may be provided from the second tank 701 to the radiator circuit valve 708. The second radiator feed line 710 may further comprise a fork connected to the first tank 109 such that radiator fluid (e.g. heat sink fluid 107) can flow from the second tank 701 to the first tank 109. The fork may comprise a fork valve 711 for selecting whether to allow radiator fluid to flow from the second tank 701 to the first tank 109. The fork may be formed by the previously described return line 707 or be a separate flow line.
Hence, hot radiator fluid may be taken from the second tank 701 if it has been sufficiently heated by solar power, Thus, the energy required to operate the heat pump system 400 may be reduced as solar power is used to heat the radiator fluid rather than the heat pump 100 which requires work input.
However, if the heat sink fluid 107 in the second tank 701 is not sufficiently hot, it may be controlled to flow to the first tank 109 through the return line 707 for further heating by the heat pump 100, and the hot radiator fluid may accordingly be drawn from the first tank 109.
The control unit 717 may accordingly be configured to control the radiator circuit valve 708, the fork valve 711, and/or the pump 706 in dependence on one or more temperature sensor readings (e.g. from sensors arranged in the first tank 109, the second tank 701, and/or in the radiator circuit 403) to maximize the efficiency of the system.
Similarly, the tap water circuit 404 (as previously described in relation to Fig. 4) may be connected to both the first tank 109 and the second tank 701. In particular, there may be arranged a first tap water heat exchanger 406 in the first tank 109 and a second tap water heat exchanger 712 in the second tank 701 for heating of tap water by transferring heat from the heat sink fluid 107 in the first and second tanks respectively. Hence, the tap water used in a building may be heated from either or both of the first and second tanks.
The tap water circuit 404 may accordingly comprise a tap water circuit valve 713 for selecting if the hot tap water is coming from the first tank 109 and/or the second tank 701. In particular, a first tap water feed line 714 may be provided from the first tap water heat exchanger 406 in the first tank 109 to the tap water circuit valve 713, and a second tap water feed line 715 may be provided from the second tap water heat exchanger 712 in the second tank 701 to the tap water circuit valve 713. The second tap water feed line 715 may further comprise a fork with a connecting line 716 connected to an inlet of the first tap water heat exchanger 406 in the first tank 109 such that tap water can flow from the second tap water heat exchanger 712 to the first tap water heat exchanger 406.
Hence, hot tap water may be taken from the second tank 701 if the tap water has been sufficiently heated by the heat sink fluid 107 therein. Thus, the energy required to operate the heat pump system 400 may be reduced as solar power is used to heat the tap water rather than the heat pump 100 which requires work input.
However, if the tap water has not been sufficiently heated in the second tank 701, it may be controlled to flow to the first tank 109 for further heating by the heat pump 100, and the hot tap water may accordingly subsequently be drawn from the first tank 109. In other words, the tap water may be at least partially heated (indirectly by solar power) in the second tap water heat exchanger 712, after which it may (if it is not sufficiently hot) flow to the first tap water heat exchanger 406 where it is further heated by the heat pump 100.
The control unit 717 may thus be configured to control the tap water circuit valve 713 in dependence on one or more temperature sensor readings (e.g. from sensors arranged in the first tank 109, the second tank 701, and/or in the tap water circuit 404) to maximize the efficiency of the system.
In particular, the control unit may be configured to control the tap water circuit valve 713 and/or the radiator circuit valve 708 in dependence on a temperature of the tap water and/or the radiator fluid in the second tank or exiting the second tank.
For example, the control unit may be configured to, in dependence on said temperature being below a threshold, allow the tap water and/or radiator fluid to flow from the second tank to the first tank, and from the first tank to the fluid outlet (for use as hot tap water and/or hot radiator fluid). Additionally, or alternatively, the control unit may be configured to, in dependence on said temperature being above the threshold, allow the tap water and/or radiator fluid to flow from the second tank to the fluid outlet.
Although not shown in Figs. 4 and 7, the hot tap water may be mixed with cold tap water to achieve an appropriate temperature (e.g. if the temperature of the hot tap water is too high).
Although the second tank 701 has been generally described as a solar heated tank, it will be understood that the second tank 701 may alternatively be heated by any other means including by a heat pump, e.g. a second heat pump. The circuit and/or valve arrangements that have been described in relation to Fig. 7 are equally applicable to such a differently heated additional tank.
Although Fig. 7 shows a heat pump 100 comprising a multi-pipe heat exchanger 108, it will be appreciated that the heat pump system 400 of Fig. 7, and in particular the second tank 701 and one or more of the associated valve and circuit arrangements, can be used with any appropriate heat pump. For example, embodiments include the heat pump system shown in Fig. 7 but where the heat pump including the multi-pipe heat exchanger has been replaced by a conventional heat pump or any other suitable heat pump.
The various embodiments described above are provided by way of illustration only and should not be construed to limit the invention. Those skilled in the art will readily recognize various modifications and changes that may be made to the present invention without following the example embodiments and applications illustrated and described herein, and without departing from the scope of the present disclosure.
Throughout this specification, the word "may" is used in a permissive sense (i.e. meaning having the potential to), rather than in the mandatory sense (i.e. meaning must).
Throughout this specification, the words "comprise", "include", and variations of the words, such as "comprising" and "comprises", "including", "includes", do not exclude other elements or steps.
As used throughout this specification, the singular forms "a", "an", and "the", include plural referents unless explicitly indicated otherwise. Thus, for example, reference to "an" element includes a combination of two or more elements, notwithstanding use of other terms and phrases for one or more elements, such as "one or more" or "at least one".
The term "or" is, unless indicated otherwise, non-exclusive, i.e. encompassing both "and" and "or". For example, the feature "A or B" includes feature "A", feature "B" and feature "A and B".
Unless otherwise indicated, statements that one value or action is "based on", "in response to" and/or "in dependence on" another condition or value or action, encompass both instances in which the condition or value or action is the sole factor and instances where the condition or value or action is one factor among a plurality of factors.
Unless otherwise indicated, statements that "each" instance of some collection have some property should not be read to exclude cases where some otherwise identical or similar members of a larger collection do not have the property, i.e. each does not necessarily mean each and every.

Claims

A heat pump for heating a heat sink fluid by circulating a refrigerant, the heat pump comprising:
a heat absorption stage configured to allow the refrigerant to absorb heat;

a compressor configured to compress the refrigerant;

a heat dissipation stage configured to dissipate heat from the refrigerant to the heat sink fluid; and

a multi-pipe heat exchanger configured to provide heat transfer from refrigerant in the heat dissipation stage to refrigerant the heat absorption stage and to the heat sink fluid,

wherein the multi-pipe heat exchanger comprises a first pipe and a second pipe, wherein the first pipe is arranged inside the second pipe such that the first and second pipes form an inner channel and a surrounding channel, wherein refrigerant in the heat absorption stage is configured to flow through the inner channel and refrigerant in the heat dissipation stage is configured to flow through the surrounding channel.
The heat pump according to any preceding claim, wherein the multi-pipe heat exchanger is configured to perform simultaneous heat transfer from the heat dissipation stage to the heat absorption stage and to the heat sink fluid.
The heat pump according to any preceding claim, wherein the multi-pipe heat exchanger is arranged to transfer heat to the heat sink fluid through a surface of the second pipe, optionally wherein the outer surface of the second pipe is configured to be surrounded by the heat sink fluid.
The heat pump according to any preceding claim, wherein the first and second pipes are concentric pipes such that the inner channel is a central channel, and the outer channel is an annular channel.
The heat pump according to any preceding claim, wherein the multi-pipe heat exchanger comprises a plurality of first pipes arranged inside the second pipe so as to form a plurality of inner channels.
The heat pump according to any preceding claim, wherein the multi-pipe heat exchanger is arranged in a tank configured to hold the heat sink fluid, such that the multi-pipe heat exchanger is submerged in heat sink fluid when the tank holds the heat sink fluid.
The heat pump according to any of claims 1 to 3, wherein the multi-pipe heat exchanger further comprises a third pipe arranged outside the second pipe so as to form a second surrounding channel, wherein the heat sink fluid is configured to flow through the second surrounding channel.
The heat pump according to any preceding claim, wherein the heat dissipation stage comprises an additional heat exchanger configured to provide heat transfer from the heat dissipation stage to the heat sink fluid, wherein the additional heat exchanger is arranged before the multi-pipe heat exchanger.
The heat pump according to claim 6, wherein the additional heat exchanger comprises a pipe configured to provide a refrigerant flow from the compressor to the multi-pipe heat exchanger, wherein the pipe of the additional heat exchanger is arranged in the tank so as to allow heat transfer from the refrigerant to the heat sink fluid.
A heat pump system for heating a fluid, the system comprising:
a heat pump according to any preceding claim, and

a tank configured to hold the heat sink fluid,

wherein the multi-pipe heat exchanger of the heat pump is arranged in the tank and configured to be submerged in the fluid when the tank holds the heat sink fluid.
The heat pump system according to claim 9, wherein the heat pump system further comprises:
an additional tank for holding the heat sink fluid, wherein the additional tank comprises means for heating the heat sink fluid by solar power,

a connecting circuit for circulating the heat sink fluid between the tank and the additional tank, and

at least one valve arrangement for selectively allowing a heated fluid to flow from the tank and/or the additional tank to a fluid outlet.
The heat pump system according to claim 10, wherein the heated fluid is the heat sink fluid.
The heat pump system according to claim 10 or 11, wherein the heat pump system further comprises a tap water circuit comprising:
a first tap water heat exchanger arranged in the tank,

a second tap water heat exchanger arranged in the additional tank, and

a fluid flow connection between an outlet of the second tap water heat exchanger and an inlet of the first tap water heat exchanger,

wherein the valve arrangement is arranged to selectively allow heated tap water to flow from the tank and/or the additional tank to the fluid outlet.
The heat pump system according to any of claims 11 to 13, wherein the system further comprises a control unit configured to:
in dependence on a temperature of the fluid in the additional tank being below a threshold, allow the fluid to flow from the additional tank to the tank, and from the tank to the fluid outlet, and/or

in dependence on the temperature of the fluid in the additional tank being above the threshold, allow the fluid from the additional tank to flow to the fluid outlet.
A method of heating a heat sink fluid, the method comprising:
compressing a refrigerant in a compressor of a heat pump;

absorbing heat, in a heat absorption stage of the heat pump, to the refrigerant;

transferring heat from refrigerant in a heat dissipation stage to refrigerant in the heat absorption stage and to the heat sink fluid, wherein the heat is transferred by a multi-pipe heat exchanger, wherein the refrigerant in the heat absorption stage flows through an inner channel of the multi-pipe heat exchanger and refrigerant in the heat dissipation stage flows through a surrounding channel of the multi-pipe heat exchanger.