METHOD THEREOF

Technical field

The present disclosure relates to a modular fluid-fluid heat transfer arrangement. The present disclosure further relates to a method for controlling a modular fluid-fluid heat transfer arrangement.

Background art

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.

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.

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 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.

Further, the heat pumps typically require a refrigerant in order to be able to operate as efficient as possible. A drawback with the refrigerants used today is that they have large global warming potential (GWP). A solution for this drawback is to use refrigerants having lower GWP which however have unwanted characteristics setting requirements on the maximum amount of refrigerant allowed in one heat pump in order to be allowed to be placed in certain zones, such as unventilated areas. However, using a small amount of refrigerant may limit the maximum input power, i.e. , the compressor capacity, of the heat pump, and so also the maximum output power achieved from the heat pump.

Thus, the conventional heating and/or cooling systems are associated with several drawbacks. There is thus a need in the art for an improvement in this area.

Summary

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 and solve at least the above mentioned problem.

It is an object of the disclosure to provide an efficient heat transfer arrangement for heating and/or cooling and/or providing tap water to different types of buildings.

Another object is to provide a flexible, but also adjustable, heat transfer arrangement.

Another object is to provide such a heat transfer arrangement which is environmentally friendly.

Another object is to provide such a heat transfer arrangement which is less time consuming to install and/or maintain.

It is also an object to provide a cost-efficient heat transfer arrangement. It is also an object to provide a compact heat transfer arrangement. According to a first aspect, there is provided a modular fluid-fluid heat transfer arrangement comprising: first inlet and outlet junction pipes for connecting the modular fluid-fluid heat transfer arrangement to a cold fluid side to form a cold side fluid recirculation path; second inlet and outlet junction pipes for connecting the modular fluidfluid heat transfer arrangement to a hot fluid side to form a hot side fluid recirculation path; and a plurality of heat pump modules, wherein each heat pump module comprises: first inlet and outlet ports; second inlet and outlet ports; control means for controlling the heat pump module; and a refrigerant circulation path which includes the following entities connected to one another in sequence: a first heat exchanger unit fluidly connected to said first inlet and outlet ports; a compressor; a second heat exchanger unit fluidly connected to said second inlet and outlet ports; and an expander; wherein, when in use, said plurality of heat pump modules are connected in parallel to each other, by their respective first inlet and outlet ports being connected to said first inlet and outlet junction pipes, respectively, and by their respective second inlet and outlet ports being connected to said second inlet and outlet junction pipes, respectively.

Through-out the application text, the term “modular fluid-fluid heat transfer arrangement” will also be referred to as “heat transfer arrangement” or “arrangement”.

By the term “modular fluid-fluid heat transfer arrangement” is here meant an arrangement which comprises a plurality of heat pump modules which are separate from and independently of each other. Thus, the plurality of heat pump modules may be introduced in a housing or a zone, e.g., in a controlled space in which the plurality of heat pump modules is arranged, without the need of being attached, e.g., fastened, or mounted, to each other. The arrangement may be configured to cover, i.e. , being able to heat and/or cool and/or provide tap water to, an area. The area may be the whole, or a part of, the building. Thus, the fluid-fluid heat transfer arrangement may be configured to provide cooling or heating to a building, or a part of a building. If the arrangement is configured to provide heat to the building, the purpose of the arrangement is to supply heat from the cold to the hot side. If the arrangement is configured to provide cooling to the building (i.e. to remove heat therefrom), the purpose of the arrangement is to remove heat from the cold side.

The fluid-fluid heat transfer arrangement may be a fluid-fluid heat pump arrangement configured to provide heat to the hot side fluid for heating the same.

The fluid-fluid heat transfer arrangement may be a fluid-fluid cool pump arrangement configured to remove heat from the cold side fluid for cooling the same.

As readily appreciated by the person skilled in the art, the fluid-fluid heat pump arrangement and the fluid-fluid cool pump arrangement is in principle the same, the only difference being what the end user is interested in to achieve (heating or cooling). However, there may be differences between the two implementations of the general concept with regards to features such as e.g. the temperature range used in the hot and cold side grids. This is further discussed later.

By the term “connecting the modular fluid-fluid heat transfer arrangement to a cold fluid side” is here meant that the first inlet and outlet junction pipes are configured to be physically connected to, or coupled to, the cold fluid side via any kinds of pipes, connectors, or the like. Put differently, the first inlet and outlet junction pipes are configured to be fluidly connected to the cold fluid side such that a cold side fluid is able to be fed in the cold side fluid recirculation path, between the heat transfer arrangement and the cold fluid side. In this context, the first inlet junction pipe is connectable to a hot conduit of the cold fluid side and the first outlet junction pipe is connectable to a cold conduit of the cold fluid side. For typical heating applications of the arrangement, the fluid in the cold conduit of the cold fluid side may be in the range of -10 to 25°C and the fluid in the hot conduit of the cold fluid side may be in the range of 0 to 40°C. For typical cooling applications of the arrangement, the fluid in the cold conduit of the cold fluid side may be in the range of -10 to 25°C and the fluid in the hot conduit of the cold fluid side may be in the range of 10 to 50°C.

For typical heating application, the cold fluid side 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 fluid side may be coupled to a downhole heat exchanger, or borehole heat exchanger. For typical cooling applications, the cold fluid side may be a cooling system in the building.

By the term “connecting the modular fluid-fluid heat transfer arrangement to a hot fluid side” is here meant that the second inlet and outlet junction pipes are able to be physically connected to, or coupled to, the hot fluid side via any kinds of pipes, connectors, or the like. Put differently, the second inlet and outlet junction pipes are configured to be fluidly connected to the hot fluid side such that the hot side fluid is able to be transported in the hot side fluid recirculation path, between the heat transfer arrangement and the hot fluid side. In this context, the second inlet junction pipe is connectable to a cold conduit of the hot fluid side and the second outlet junction pipe is connectable to a hot conduit of the hot fluid side. For typical heating applications of the arrangement, the fluid in the cold conduit of the hot fluid side may be in the range of 10 to 50°C and the fluid in the hot conduit of the hot fluid side may be in the range of 25 to 75°C. For typical cooling applications of the arrangement, the fluid in the cold conduit may be in the range of -10 to 25°C and the fluid in the hot conduit may be in the range of 0 to 40°C.

For typical heating applications, an input temperature of the fluid to the arrangement may be om the range of 0 to 40°C and an output temperature of the fluid from the arrangement to the building or parts of the building may be in the range of 25 to 75°C. For typical cooling applications, the input temperature of the fluid may be in the range of 0 to 40°C and the output temperature of the fluid from the arrangement to the building or parts of the building may be in the range of -10 to 25°C.

For typical heating applications, the hot fluid side may be a heating system, such as radiators or tap water systems, in the building. For typical cooling applications, the hot fluid side 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 hot fluid side may be coupled to a downhole heat exchanger, or borehole heat exchanger.

By the term “refrigerant circulation path” is here meant a heat pump module loop in which a refrigerant is circulating. The refrigerant is typically circulated through the first heat exchanger unit, the compressor, the second heat exchanger unit and the expander. The expander may be configured to control an amount of refrigerant released into the first heat exchanger unit. The refrigerant may be referred to as a working fluid. The refrigerant may be configured to evaporate and condense when circulating in the heat pump module.

A refrigerant is a working fluid used in the refrigeration cycle of air conditioning systems and heat pumps where in most cases they undergo a repeated phase transition from a liquid to a gas and back again. A particular refrigerant has a phase transition temperature at a specific pressure.

For typical heating and/or cooling applications of the arrangement, the refrigerant should have a phase transition temperature in the range of -30 to 0°C in a pressure range 1-10 bar. For such applications, the refrigerant may be chosen from the group consisting of: R290, R32, R410A, R470C and R134A.

By the term “control means” is here meant any means of controlling the heat pump module, especially the operation thereof. The control means may be e.g. a microprocessor or a central processing unit, CPU, which is capable of making its own individual assessment based on input data from e.g. sensors. This is an example of an active control means. However, a control means according to the disclosure may alternatively be a socket for operably connecting the heat pump module to an external control unit. In the latter case, the heat pump module is passive, and the decisions are made outside of the heat pump module in the external control unit. Preferably, the control means of each heat pump of the plurality of heat pumps comprises a processor, e.g., a CPU configured to actively control the heat pump modules.

Each heat pump module of the plurality of heat pump modules may have a maximum input power, Pin, max, of 1-10 kW, preferably 3-6 kW. Neglecting the much smaller power needed for pumps, sensors etc. in the module, the term “maximum input power” may be approximately the same as a maximum capacity of the compressor, often referred to as compressor power, i.e. , the power which is supplied to the compressor during operation at its maximum rated power. Each compressor may be configured to operate with a variable compressor power, wherein the maximum input power is the highest power which may be supplied to the compressor during operation. Accordingly, the associated heat pump module may also be variably operated.

The arrangement may have a maximum arrangement input power. In this context, the “maximum arrangement input power” is the sum of the maximum input powers of all heat pump modules present in the arrangement.

Each heat pump module may be able to produce a maximum output power, Pout, max, based on the associated maximum input power and a coefficient of performance (COP). The COP is a ratio of useful provided heating or cooling to supplied work energy. It is advantageous to have as high COP as possible because it provides to higher efficiency, lower energy consumption and thus lower operating costs.

The arrangement may have a maximum arrangement output power. In this context, the “maximum arrangement output power” is the sum of the maximum output powers of all heat pump modules present in the arrangement. The heat transfer arrangement may be operating in order to produce a required arrangement output power. The “required arrangement output power” is the power needed to fulfil heating and/or cooling and/or tap water requirements. Thus, the required arrangement output power is the output power needed to provide a required temperature of heating and/or cooling and/or tap water to the building. As readily appreciated by the person skilled in the art, the required arrangement output power may be the same as the maximum arrangement output power but may also be less than the maximum arrangement output power, dependent on the requirements.

Each heat pump module of the plurality of heat pump modules may have a height between 25-45 cm. Each heat pump module of the plurality of heat pump modules may have a width between 15-35 cm. Each heat pump module of the plurality of heat pump modules may have a depth between 45- 65 cm.

Each heat pump module of the plurality of heat pump modules may alternatively have a height between 10-50 cm. Each heat pump module of the plurality of heat pump modules may alternatively have a width between 10-50 cm. Each heat pump module of the plurality of heat pump modules may alternatively have a depth between 30-80 cm, or 40-65 cm. In one embodiment, each heat pump module of the plurality of heat pump modules has a height of about 41 cm, a width of about 23 cm and a depth of about 43 cm.

This implies that each heat pump module of the plurality of heat pump modules may be portable. By “portable” is herein means that the dimensions and/or weight of the heat pump module is within limits allowing it to be manually carried to and from a heat transfer arrangement by maintenance personnel without need of special equipment, such as hoists, lifts or the like. This may be advantageous as it allows to introduce an improved maintenance paradigm. Instead of repairing a faulty heat pump on site, the faulty heat pump module may be detached from the heat transfer arrangement and replaced by another heat pump module. This gives advantages in reduced complexity in maintenance. Each heat pump module of the plurality of heat pump modules may have a weight within the range of 20-40 kg, or 25-35 kg or about 30 kg.

It should however be noted that each heat pump module of the plurality of heat pump modules may have a greater, or smaller, maximum input power than the above-identified ranges. The maximum input power of the respective heat pump module may determine the size of the heat pump module. Thus, it should further be noted that each heat pump module of the plurality of heat pump modules may have greater, or smaller, height, width, and/or depth than the above-identified ranges.

The modular fluid-fluid heat transfer arrangement is advantageous as it provides for a flexible heat pump system. Thus, since each heat pump module of the plurality of heat pump modules is separated from and independent of the other heat pump modules comprised in the arrangement, and that they are connected to each fluid side in parallel, it is possible to design and/or modify the arrangement in different ways. Thus, the different heat pump modules may have different maximum input power such that it is possible to tailor an arrangement based on different requirements, among other things, the size of the building and the required arrangement output power needed for heating and/or cooling and/or providing tap water to the building. This facilitates the provision of being able to provide an efficient heat transfer arrangement for heating and/or cooling and/or providing tap water to different types of buildings.

By arranging the plurality of heat pump modules in parallel to each other, it is possible to continue operate the arrangement although one or more of the heat pump modules may broke or having other problems with running.

At least one heat pump module of the plurality of heat pump modules may be arranged in a respective operating position when in use, from which operating position it may be detachable.

The term “detachable” is here meant that at least one heat pump module of the plurality of heat pump modules are removably arranged in the arrangement. Put differently, at least one heat pump module of the plurality of heat pump modules is arranged in the arrangement in a way such that it is possible to remove and/or replace the heat pump module.

Preferably, each heat pump module of the plurality of heat pump modules is arranged in a respective operating position, when in use, from which operating position it is detachable.

This is advantageous as it allows for removing the heat pump module in an easy way upon maintenance of the heat pump module. Thus, it is possible to remove the heat pump module from the arrangement and maintain and/or service the heat pump module at a different position than within the arrangement. This simplifies maintenance of the heat transfer arrangement. This is further advantageous as it allows for decreasing the required output arrangement power needed, for instance if there is a need to downsize the area which the arrangement needs to cover, without the need of replacing the complete arrangement.

This is yet further advantageous as it allows for replacing the heat pump module with another heat pump module. Thus, the maximum arrangement input power of the arrangement may be easily adjusted by being able to replace the heat pump module to another heat pump module having a different maximum input power than the heat pump module removed from the arrangement.

Thus, instead of having to discard, or maintain, the complete arrangement when one of the heat pump modules has problems, it is possible to discard, or maintain, the specific heat pump module. This provides for both an increased life of the heat transfer arrangement but also a more environmentally friendly solution.

It may also be possible to add further heat pump modules to the heat transfer arrangement. This is advantageous as it allows for increasing the required output arrangement power, for instance if there is a need to expand the area which the arrangement needs to cover, without the need of replacing the complete arrangement.

Each heat pump module of the plurality of heat pump modules may comprise a cold side fluid flow control device configured to control a flow rate of cold side fluid being supplied to each heat pump module from said cold side fluid recirculation path.

This is advantageous as it allows for the cold side fluid flow control device to control, or balance, the flow rate of the cold side fluid. Thus, the cold side fluid flow control device is configured to control the flow of the cold side fluid in the respective heat pump module such that a required output power is achieved.

This is further advantageous as it allows for controlling the flow rate of the heat pump module in an easy and efficient way.

The cold side fluid flow control device may comprise a pump configured to be variably adjustable. This allows actively controlling the fluid flow rate for each module. In essence, each pump may take exactly the amount of fluid required by the respective module.

The cold side fluid flow control device may comprise a valve configured to be variably adjustable. This allows for a more simplified construction of the module. Each module is able to individually control how much fluid is input to the module, but each module is dependent on an overpressure on the intake side, e.g. from a central pump system being arranged in the cold fluid side.

The first inlet and outlet junction pipes may be physically connected to, or coupled to, the cold fluid side via the cold side fluid flow control device.

The modular fluid-fluid heat transfer arrangement may further comprise a main controller which may be configured to control an operation of each heat pump module of the plurality of heat pump modules.

The main controller may be one of the control means comprised in one of the heat pump modules. The main controller may alternatively be an external controller, being different from the control means comprised in the respective heat pump module.

The main controller configured to control the operation of each heat pump module is advantageous as it facilitates the provision for controlling each heat pump module, but also the arrangement, in an easy and efficient way. The main controller may be configured to control the operation of each heat pump module of the plurality of heat pump modules to operate in an operational mode being common for all heat pump modules.

In this context, the operational mode of each heat pump module is the same at all times. The heat pump modules may operate at variable input power. The variable input power may include simple switching on/off between no operation and operation at one predefined input power. The variable input power may alternatively include some complex switching between two or more different input powers. If the input power is variable, it is however variable in the same way (i.e. a common way) for all heat pump modules of the plurality of heat pump modules. Thus, all heat pump modules may be synchronized controlled such that either all heat pump modules are on, or all heat pump modules are off. If all heat pump modules are on, they are all running with the same input power.

This is advantageous in that the main controller is configured to control the operation of each heat pump module of the plurality of heat pump modules to be substantially equal for all heat pump modules in the arrangement. By being able to control the operation of each heat pump module to operate in the operation mode, which is common for all heat pump modules, it is possible to control the heat transfer arrangement in an easy and efficient way without the need of including any further fluid control devices, such as check valves or the like.

Preferably, each heat pump module of the plurality of heat pump modules has the same maximum input power. Thereby, it is possible to control all heat pump modules of the plurality of heat pump modules in the same way.

The operational mode may be defined by an input power being common for all heat pump modules.

This implies that every heat pump module is always operating at the same input power. As previously stated, by the term “input power” is here meant the power supplied to the heat pump module, a power which predominately is used by the compressor, e.g., the power needed to run the compressor of the respective heat pump module in order to produce a required output power.

The heat pump input power may be determined based on the number N of heat pump modules operating in the arrangement and a total input power P of all heat pump modules of the arrangement. Assume that the heat transfer arrangement comprises N heat pump modules. In order to achieve a required outlet temperature in the hot fluid side, a total input power P for the heat transfer arrangement is needed. The main controller may be configured to control the operation of each heat pump module such that each heat pump module operates in an operational mode which is common for all heat pump modules. Preferably, each heat pump module is supplied with the same input power. Thus, if dividing the total input power P evenly between the number N of heat pump modules operating in the heat transfer arrangement, each heat pump module should operate in an operational mode such that each heat pump module uses a common input power equal to P/N.

This is further advantageous in that it reduces the complexity of the heat transfer arrangement as well as it increases the controllability of the arrangement in an efficient way.

The above implies that the main controller can be configured to control the operation of each heat pump module of the plurality of heat pump modules based on the number N of heat pump modules operating in the heat transfer arrangement. It further implies that the main controller may be configured to adjust the operation of the heat pump modules in response to a change in the number of heat pump modules. If, for example, one heat pump module is removed for maintenance, the controller may be configured to operate the remaining heat pump modules at a slightly higher power to adjust for the lower number of heat pump modules in the system. This may be advantageous as it makes the controlling less complex and optimizes the performance of the heat transfer arrangement.

Each heat pump module of the plurality of heat pump modules may comprise a hot side fluid flow control device configured to control a flow rate of hot side fluid being supplied to the hot fluid side from each heat pump module.

This is advantageous as it allows for the hot side fluid flow control device to control, or balance, the flow rate of the hot side fluid. Thus, the hot side fluid flow control device is configured to control the flow of the hot side fluid in the respective heat pump module such that a required heat transfer and thereby output power is achieved.

This is further advantageous as it allows for controlling the flow rate of the heat pump module in an easy and efficient way.

The hot side fluid flow control device may comprise a pump configured to be variably adjustable. This allows actively controlling the fluid flow rate for each module. In essence, each pump may take exactly the amount of fluid required by the respective module.

The fluid flow control device may comprise a valve configured to be variably adjustable. This allows for a more simplified construction of the module. Each module is able to individually control how much fluid is input to the module, but each module is dependent on an overpressure on the intake side, e.g. from a central pump system being arranged in the cold fluid side. The valve may preferably be a check valve.

The second inlet and outlet junction pipes may be physically connected to, or coupled to, the hot fluid side via the hot side fluid flow control device.

The main controller may be configured to individually control the operation of each heat pump module of the plurality of heat pump modules to allow operating each heat pump module at a respective operational mode.

In this context, the respective operational mode may be the same operational mode for one or more of the heat pump modules or it may be different for each of the heat pump modules.

In this context, the main controller is configured to control the operation of each heat pump module and allow operating each heat pump module at the respective operational mode. Here, the main controller is configured to control the operation of each heat pump module individually of the operation of the other heat pump modules of the heat transfer arrangement. The main controller may be an external controller, being different from the control means comprised in the respective heat pump module.

This is advantageous in that a flexible heat transfer arrangement deployment is achieved.

The respective operational mode of each heat pump module may be based on a predetermined fraction of a maximum input power of that heat pump module, wherein the predetermined fraction is common for all heat pump modules.

The predetermined fraction may be determined based on a required arrangement output power Pout for the arrangement and a total maximum input power of all heat pump modules in the heat transfer arrangement. If dividing the required arrangement output power evenly between the maximum input power of all heat pump modules, the predetermined fraction is achieved. As said above, for this example embodiment, the predetermined fraction is common for all heat pump modules. Thus, if the predetermined fraction is 40% of the maximum arrangement output power, each heat pump module should operate with 40% of the heat pump modules respective maximum input power. For example, if the maximum input power of one heat pump module is 3 kW and of another heat pump module is 6 kW, the one heat pump module should operate with 1 .78 kW and the other heat pump module should operate with 2.66 kW.

Each heat pump module may have a different maximum input power.

This is advantageous as it allows for an easy and efficient solution in which each heat pump module may be individually controlled.

The respective predefined operational mode of each heat pump module may be based on a predetermined time sequence alternating between a first state, where the heat pump module is not in operation, and a second state, where the heat pump module is operated at a predetermined input power.

By the term “predetermined input power” is here meant an input power determined by e.g. the main controller and subsequently supplied to the heat pump module. Thus, the predetermined input power may be a fraction of the maximum input power or, alternatively, may be the maximum input power.

This is advantageous as it allows for that at least one heat pump module is in the first state, if the heat transfer arrangement is in use, and other heat pump modules may be in the second state. Thus, a total compressor operation time per heat pump module may be maximized. Thereby, a flexible but also efficient heat transfer arrangement is achieved. The predetermined time sequence for each heat pump module may be determined such that a total number of stops for the compressor in the respective heat pump module is minimized. For instance, assuming N heat pump modules, and a required arrangement inlet power corresponding to a power P. Then by alternating each heat pump module to be enabled T/N of the time T and respective heat pump k=1 , ..., N is enabled at interval [T(k- 1 )/N,T(k/N)] each heat pump will be stopped once per time T. Thus, in this context, the required arrangement inlet power is equal to the input power of a heat pump module since only one heat pump module is operating at a time.

The control means of each heat pump module of the plurality of heat pump modules may be in communication with the control means of the other heat pump modules of the plurality of heat pump modules and/or with the main controller.

By the term “in communication with” is here meant that the control means of each of the plurality of heat pump modules and/or the main controller may be connected to each other, either wired or wireless connected. Thus, the control means of each of the plurality of heat pump modules and/or the main controller may be configured to communicate to each other. This is advantageous as it allows for controlling the heat transfer arrangement based on the control means of the respective heat pump module. Thus, it allows for controlling the heat transfer arrangement in an easy and efficient way.

Each heat pump module of the plurality of heat pump modules may comprise a refrigerant, wherein an amount of the refrigerant in each heat pump module is below a predetermined threshold-value. This may be advantageous for the modular heat transfer arrangement since as it allows providing a considerably higher total output power than a single heat pump-based system while keeping the weight of refrigerant in each refrigerant cycle within allowed limits.

The plurality of heat pump modules may be arranged in the zone as introduced above, e.g., a controlled space in which the heat transfer arrangement is arranged. The zone may have characteristics at which the predetermined threshold-value is based. In this context, the pre-determined threshold value is based on standards or requirements known in the art for the specific refrigerant depending on the characteristics of the zone. The characteristics may be the size (area or volume) of the zone and/or if the zone is ventilated or non-ventilated and/or zones where certain chemicals are placed.

According to some embodiments, a total volume 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.

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.

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

The term “predetermined threshold-value” is here meant an amount allowed refrigerant in the heat pump module which is associated with characteristics of the zone. For example, if the refrigerant is R290, the predetermined threshold-value in a heat pump module is currently 334 g without requirements on that the zone should be a ventilated area. Other refrigerants may have different predetermined threshold-values. According to a second aspect of the disclosure, these and other objects are also achieved in full or at least in part, by a method for controlling a modular fluid-fluid heat transfer arrangement comprising a plurality of heat pump modules, each comprising first inlet and outlet ports and second inlet and outlet ports, the method comprising: connecting the modular fluid-fluid heat transfer arrangement to a cold fluid side thereby forming a cold side fluid recirculation path; connecting the modular fluid-fluid heat transfer arrangement to a hot fluid side thereby forming a hot side fluid recirculation path; connecting each heat pump module of the plurality of heat pump modules in parallel to each other by connecting their respective first inlet and outlet ports to first inlet and outlet junction pipes of the modular fluid-fluid heat transfer arrangement, respectively, and by connecting their respective second inlet and outlet ports to second inlet and outlet junction pipes, respectively of the modular fluid-fluid heat transfer arrangement; and controlling each heat pump module of the plurality of heat pump modules to operate in a respective operational mode.

The operational mode may be common for all heat pump modules of the plurality of heat pump modules or the operational mode may be individually defined for each heat pump module of the plurality of heat pump modules.

Effects and features of the second aspect 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. It is further noted that the inventive concepts relate to all possible combinations of features unless explicitly stated otherwise. A further scope of applicability of the present invention 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 invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description. Hence, it is to be understood that this invention 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 description of the drawings

The invention will by way of example be described in more detail with reference to the appended schematic drawings, which shows a presently preferred embodiment of the invention.

Figure 1 illustrates a modular fluid-fluid heat transfer arrangement.

Figure 2 illustrates a variant of the modular fluid-fluid heat transfer arrangement as illustrated in figure 1 .

Figure 3 is a flowchart illustrating a method for controlling a modular fluid-fluid heat transfer arrangement.

Detailed description

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. The present invention 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 to fully convey the scope of the invention to the skilled addressee. Like reference characters refer to like elements throughout. Figure 1 illustrates a modular fluid-fluid heat transfer arrangement 100 for heating and/or cooling and/or providing tap water to buildings or the like by way of example. Here after, the modular fluid-fluid heat transfer arrangement 100 may also be referred to as “heat transfer arrangement 100” or “arrangement 100”.

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

The first inlet junction pipe 111 is configured to supply a cold side first fluid from the cold fluid side 101 to the heat transfer arrangement 100. The first outlet junction pipe 112 is configured to supply a cold side second fluid from the heat transfer arrangement 100 to the cold fluid side 101 . Thereby the cold side fluid recirculation path 103 is formed. The cold side first fluid is preferably warmer than the cold side second fluid.

The second outlet junction pipe 121 is configured to supply a hot side first fluid from the heat transfer arrangement 100 to the hot fluid side 102. The second inlet junction pipe 122 is configured to supply a hot side second fluid from the hot fluid side 102 to the heat transfer arrangement 100. Thereby the hot side recirculation path 104 is formed. The hot side first fluid is preferably warmer than the hot side second fluid.

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

For typical heating applications of the arrangement 100, the cold fluid 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 fluid side 101 may be coupled to a downhole heat exchanger, or borehole heat exchanger. For typical heating applications of the arrangement 100, the hot fluid side 102 may be a heating system, such as radiators or tap water systems, in the building.

For typical cooling applications of the arrangement 100, the cold fluid side 101 may be a cooling system in the building. For typical cooling applications of the arrangement 100, the hot fluid side 102 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 hot fluid side 102 may be coupled to a downhole heat exchanger, or borehole heat exchanger.

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, 131 b and second inlet and outlet ports 132b, 132a. The first inlet and outlet ports 131a, 131 b 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.

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, 131 b 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.

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, an expander 138 and a cold side fluid flow control device 139. The first heat exchanger unit 135 is fluidly connected to the first inlet and outlet ports 131a, 131 b. 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, 131 b, 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.

The refrigerant circulation loop 134 preferably 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 and the cold side first fluid are configured to exchange thermal energy between each other such that a temperature of the refrigerant increases and a temperature of the cold side first fluid decreases thereby forming the cold side second fluid. Thus, the cold side first fluid and the cold side second fluid is typically the same fluid which has been supplied through the first heat exchanger unit 135 of the heat transfer arrangement 100, in which an exchange of thermal energy occurs between the cold side first fluid and the refrigerant.

The cold side second fluid is circulated in the cold side recirculation path 103 to the cold fluid side 102. The refrigerant is circulated from the first heat exchanger unit 135 to the compressor 136 which is configured to increase the temperature and pressure of the refrigerant even further before supping the refrigerant to the second heat exchanger unit 137.

In the second heat exchanger unit 137, the refrigerant and the hot side first fluid is configured to exchange thermal energy between each other such that a temperature of the refrigerant decreases and a temperature of the hot side first fluid increases thereby forming the hot side second fluid. Thus, the hot side first fluid and the hot side second fluid is typically the same fluid which has been supplied through a second heat exchanger unit 137 of the heat transfer arrangement 100, in which an exchange of thermal energy occurs between the hot side fluid and the refrigerant.

The hot side first fluid is circulated in the hot side recirculation path 104 to the hot fluid side 102. The refrigerant is circulated from the second heat exchanger unit 137 to the expander 138 which is configured to control an amount of refrigerant released into the first heat exchanger unit 135.

Each heat pump module 130a, 130b, 130c further comprises control means 133 for controlling the heat pump module 130a, 130b, 130c. Each control means 133 may be in communication with the control means 133 of the other heat pump modules 130a, 130b, 130c. Thus, the control means 133 may be wired or wireless connected to each other.

The heat transfer arrangement 100 further comprises a main controller 133, 143. The main controller 133, 143 is configured to control an operation of each heat pump module 130a, 130b, 130c of the plurality of heat pump modules 130a, 130b, 130c. The main controller 133, 143 may be configured to control each heat pump module 130a, 130b, 130c of the plurality of heat pump modules 130a, 130b, 130c to operate in an operational mode which is common for all heat pump modules 130a, 130b, 130c. The main controller 133, 143 may be configured to control each heat pump module 130a, 130b, 130c of the plurality of heat pump modules 130a, 130b, 130c to operate in a respective operational mode. The respective operational mode may be common for one or more heat pump modules 130a, 130b, 130c or may be different for all heat pump modules 130a, 130b, 130c.

The main controller 133, 143 may be one of the control means 133 comprised in one of the heat pump modules 130a, 130b, 130c. The main controller 133, 143 may be an external control unit 143. The main controller 133, 143 may be wired or wireless connected to the control means 133 of the respective heat pump module 130a, 130b, 130c.

When the main controller 133, 143 is configured to control each heat pump module 130a, 130b, 130c to operate in the common operational mode, the operational mode is defined by an input power of respective heat pump module 130a, 130b, 130c which is common for all heat pump modules 130a, 130b, 130c.

When the main controller 133, 143 is configured to control each heat pump module 130a, 130b, 130c to operate in the respective operational mode, the main controller 133, 143 is configured to individually control the operation of each heat pump module 130a, 130b, 130c. The respective operational mode may be based on a predetermined fraction of a maximum input power of that heat pump module 130a, 130b, 130c, wherein the predetermined fraction is common for all heat pump modules 130a, 130b, 130c. The respective operational mode may be based on a predetermined time sequence alternating between a first state and a second state. When in the first state, the heat pump module 130a, 130b, 130c is not in operation, and when in the second state, the heat pump module 130a, 130b, 130c is operated at a predetermined input power.

As said above, and as depicted in figure 1 , each heat exchanger module 130a, 130b, 130c comprises the cold side fluid flow control device 139. In the referred figure, the cold side fluid flow control device 139 is illustrated as a pump. The pump may be variably adjustable. The cold side fluid flow control device 139 is configured to control a flow rate of the cold side fluid, which is supplied to the heat pump module 130a, 130b, 130c from the cold side recirculation path 103. Although it is illustrated that each heat pump module 130a, 130b, 130c comprises one cold side fluid flow control device 139 the cold side fluid flow control device 139 may be omitted. The cold side fluid flow control device 139 may also be arranged in either one or both of the first inlet and outlet junction pipes 111 , 112. Thus, the arrangement 100 has to comprise at least one cold side fluid flow control device 139.

As further depicted, each heat pump module 130a, 130b, 130c comprises a hot side fluid flow control device 150 which is arranged at the second outlet junction pipe 121. Each heat pump module 130a, 130b, 130c may comprise a further hot side fluid flow control device 150 which may be arranged at the first inlet junction pipe 122. The hot side fluid control device 150 and, if present, the further hot side fluid control device, may be a check valve. Although it is illustrated that each heat pump module 130a, 130b, 130c comprises one hot side fluid flow control device 150, the hot side fluid flow control device 150 may be omitted. Preferably, this is the case when the main controller 133, 143 is configured to control the operation of each heat pump module 130a, 130b, 130c to operate in the operational mode which is common for all heat pump modules 130a, 130b, 130c.

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. This is however well known in the art and is therefore excluded from the figures in this context.

In addition to what have been discussed in connection with figure 1 , and as best illustrated in figure 2, the heat pump module 130c is configured to be removably arranged in the arrangement 100, or put differently, may be detachable from the arrangement 100. Thus, 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, all heat pump modules 130a, 130b, 130c of the arrangement may be removably arranged in the arrangement 100, or detachable from the arrangement 100.

In figure 2, the heat pump modules 130a, 130b are arranged in their operating position, which, when the arrangement 100 is in use, all heat pump modules 130a, 130b, 130c are. Thus, each heat pump modules 130a, 130b, 130c is detachable from its respective operating position.

Further, figure 2 illustrates that each heat pump module 130a, 130b, 130c may alternatively comprises a further cold side fluid flow device 140 instead of the cold side fluid flow control device 139 depicted in figure 1 . The cold side fluid flow control device 140 of figure 2 is a valve configured to be variably adjusted. Although not illustrated, the heat transfer arrangement 100 as depicted in figure 2, may comprise the same features as the heat transfer arrangement 100 illustrated in figure 1 and vice versa.

With reference to figure 3, a flowchart illustrating a method 300 for controlling the modular fluid-fluid heat transfer arrangement 100 which was introduced in connected with figures 1 and 2 by way of example.

The method 300 comprises a first step S302 in which the modular fluidfluid heat transfer arrangement 100 is connected to the cold fluid side 101 thereby forming a cold side fluid recirculation path 103.

Thereafter, in a second step S304, the modular fluid-fluid heat transfer arrangement 100 is connected to the hot fluid side 102 thereby forming a hot side fluid recirculation path 104.

In a third step S306, each heat pump module 130a, 130b, 130c of the plurality of heat pump modules 130a, 130b, 130c is connected in parallel to each other. The plurality of heat pump modules 130a, 130b, 130c are connected in parallel to each other by connecting their respective first inlet and outlet ports 131a, 131 b to said first inlet and outlet junction pipes 111 , 112, respectively, and by connecting their respective second inlet and outlet ports 132a, 132b to said second inlet and outlet junction pipes 121 , 122, respectively.

Thereafter, in a fourth step S308, each heat pump module 130a, 130b, 130c of the plurality of heat pump modules 130a, 130b, 130c being controlled to operate in a respective operational mode.

Even though illustrated and described in a certain order, other order may also be used.

The person skilled in the art realizes that the present invention 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 invention, from a study of the drawings, the disclosure, and the appended claims.