WO2024096799A1

WO2024096799A1 - A method for monitoring a check valve condition in a modular fluid-fluid heat transfer arrangement and a modular fluid-fluid heat transfer arrangement

Info

Publication number: WO2024096799A1
Application number: PCT/SE2023/051105
Authority: WO
Inventors: Fredrik ROSENQVIST; Bengt Lindoff
Original assignee: Qvantum Industries Ab
Priority date: 2022-11-03
Filing date: 2023-11-02
Publication date: 2024-05-10

Abstract

A method (200) for monitoring a check valve condition in a modular fluid-fluid heat transfer arrangement (100) which comprises a plurality of heat pump modules (130a, 130b) and, for each of the heat pump modules (130a, 130b), a check valve (140a, 140b) arranged in a fluid flow path of the heat pump module (130a, 130b) and configured to selectively close the fluid flow path, the method (200) comprising: (a) providing a close valve signal to the check valve (140a, 140b); (b) determining a data set pertaining to a fluid temperature of the fluid flow path; (c) comparing the data set with a reference data set; and (d) if a difference between the data set and the reference data set exceeds a threshold: transmitting (S201) an alarm signal for indicating a malfunctioning of said check valve (140a, 140b). The disclosure further relates to a modular fluid-fluid heat transfer arrangement (100).

Description

A METHOD FOR MONITORING A CHECKVALVE CONDITION IN A MODULAR FLUID-FLUID HEAT TRANSFER ARRANGEMENT AND A MODULAR FLUID-FLUID HEAT TRANSFER ARRANGEMENT

Technical field

The present disclosure relates to a method for monitoring a check valve condition in a modular fluid-fluid heat transfer arrangement which comprises a plurality of heat pump modules and, for each of the heat pump module, a check valve. The present disclosure further relates to 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, easier to control and with lower technical complexity, e.g., with fewer and/or less complex sensors for measuring the space heat and tap water energy consumption than presently used heat pumps. 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 monitoring method for a heat transfer arrangement.

Another object of the disclosure is to provide a time-efficient monitoring method for a heat transfer arrangement.

Another object of the disclosure is to provide a time-efficient but also cost-efficient fault monitoring method for a heat transfer arrangement.

Another object of the disclosure is to provide an accurate monitoring method for a heat transfer arrangement.

It is also an object to provide a cost-efficient heat transfer arrangement.

According to a first aspect, there is provided a method for monitoring a check valve condition in a modular fluid-fluid heat transfer arrangement which comprises a plurality of heat pump modules, each of the plurality of heat pump modules being fluidly connected to a first fluid grid via a respective first fluid flow path and to a second fluid grid via a respective second fluid flow path, and wherein the modular fluid-fluid heat transfer arrangement further comprises, for each of the plurality of heat pump modules, a check valve arranged in a fluid flow path selected from the respective first fluid flow path and the respective second fluid flow path of the heat pump module, the check valve being configured to selectively close the fluid flow path, the method comprising: for at least one of the plurality of heat pump modules:

(a) providing a close valve signal to the check valve;

(b) determining a data set pertaining to a fluid temperature of the fluid flow path in response to a provision of the close valve signal to the check valve; and (c) comparing the data set with a reference data set pertaining to at least one reference temperature;

(d) upon the comparison fulfilling a comparison criterion, transmitting an alarm signal for indicating a malfunctioning of the check valve.

The first fluid grid may be a cold fluid grid or a hot fluid grid. The second grid may be a cold fluid grid or a hot fluid grid. The first fluid grid and the second fluid grid may be different fluid grids, i.e. , one may be the cold fluid grid and the other may be the hot fluid grid.

The respective first and second fluid flow paths may extend through the associated heat pump module.

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, a building. Thus, the fluid-fluid heat transfer arrangement may be configured to provide cooling or heating or tap water to the building, or a part of the building. If the arrangement is configured to provide heat to the building, the purpose of the arrangement is to supply heat from a cold to a 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 a 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 a 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 first and second fluid grids.

The disclosed check valve may be configured to hydraulically connect the associated heat pump module to the first or second fluid grid. The disclosed check valve may be configured to disconnect the associated heat pump module from the first or second fluid grid. The check valve may be configured to control a flow direction of the fluid in the fluid flow path (i.e. , the first or second fluid flow path) in which the check valve is arranged. The check valve is configured to selectively close the fluid flow path such that the flow of the fluid is closed. When the fluid flow path is closed, the associated heat pump module is disconnected from the fluid grid. If the check valve works as expected, there is no flow in the fluid flow path or in the associated heat pump module when the check valve has closed the fluid flow path.

The check valve is advantageous as it allows for controlling the associated heat pump module in an easy and efficient way. The check valve is further advantageous as it allows for connecting the associated heat pump module to the grid in a controlled way. The check valve is yet further advantageous as it allows for disconnecting the associated heat pump module from the grid in a controlled way. This is especially advantageous in case some malfunction of components in the heat transfer arrangement occurs. If malfunctions in the heat transfer arrangement is identified, the modular heat pumps may have to be disconnected from the grid in order to identify where in the arrangement the problem is located. In order to being able to close the arrangement in a safe and reliable way, the check valve has to work as expected such that the associated heat pump module may be closed in a safe and reliable way. The check valve may be arranged in the first fluid flow path or in the second fluid flow path. The check valve may be arranged on either an inlet pipe or an outlet pipe of the respective first fluid flow path or the respective second fluid flow path. As the arrangement comprises a plurality of heat pump modules, the arrangement also comprises a plurality of check valves since the arrangement comprises a check valve for each of the heat pump modules. The check valves may be individually arranged, i.e. , one check valve may be arranged on the inlet pipe of the associated first fluid flow path and another check valve may be arranged on the outlet pipe of the associated first fluid flow path. This should only be seen as an example and other configurations may be possible as well.

By the term “close valve signal” is here meant a signal instructing the check valve to be closed. Hence, if the check valve works as expected, the check valve will be closed when the close valve signal is provided to the check valve. Thereby, the fluid flow path will be closed. It should thus be noted that the provision of the close valve signal does not mean that the check valve will be closed, only that instructions are conveyed to the check valve instructing the same to close. In response to that the close valve signal is provided, the determination of the data set may be provided.

By the term “data set” is here meant everything from a single data point pertaining to the fluid temperature at one location and time position, to a plurality of data points determined e.g., for multiple time positions for one location, for multiple locations for one time position, or for multiple time positions and multiple locations within the arrangement.

By the term “reference data set” is here meant everything from a reference data point pertaining to a single reference temperature at one location and time position, to a plurality of reference data points determined e.g., for multiple time positions for one location, multiple location for one time position, or for multiple time positions and multiple locations within the arrangement. The reference data set may be determined for each of the heat pump modules of the arrangement such that each heat pump module has an associated reference data set. If the heat pump modules are equal, i.e., have identical properties such as compressor capacity etc., the reference data set may be equal for each of the heat pump modules. If the heat pump modules are different, the reference data set may be different for different heat pump modules. Thus, two heat pump modules which are equal may typically react in a similar way if the associated check valve does not work as expected.

The reference data set may be determined in different ways, as will be detailed later. It is understood that the reference data set, independent on which way it is determined, will describe the estimated and/or expected behavior of the data set for a situation where the check valve is operating as expected or for a situation where the check valve is not operating as expected. Thus, the reference data set will reflect an estimation of the temperature behavior of the heat pump module for one of the two situations: check valve is actually closed, and check valve is still open I was not able to close.

When there are malfunctions of the check valve, i.e., when the check valve is not operating as expected, the check valve may not be able to disconnect the associated heat pump module from the grid in a controlled way. Instead, the associated heat pump module may be disconnected from the grid by turning off the heat pump module or the check valve may be able to partly disconnect the heat pump module from the grid. In this context, the term “disconnect” should be interpreted as inactivate, i.e., there may not be any thermal exchange between the fluids, but the heat pump module may still be connected to the grid. This is disadvantageous compared to having the check valve disconnecting the heat pump module from the grid because it is more time-consuming. In addition, the disconnection of the heat pump module from the grid without having the check valve is less efficient and accurate compared to the solution in which the check valves are included. The disconnection is also provided in a less controllable way.

The comparison criterion may be defined in different ways, as will be detailed later. It is understood that the comparison criterion, independent on which way it is defined, will indicate if the check valve is operating as expected or not, i.e., if the alarm signal is transmitted or not.

If the comparison between the data set and the reference data set fulfills the comparison criterion, the method indicates the malfunctioning of the check valve, i.e. , the method indicates that the check valve is not operating as expected.

If the comparison between the data set and the reference data set does not fulfill the comparison criterion, the check valve is considered to be operating as expected, i.e., in a correct way.

The disclosed method helps to monitor a check valve condition of the check valve provided in the heat transfer arrangement. The check valve condition is typically relating to if the check valve is working as expected or if there are malfunctions of the check valve. By the disclosed method, in which an alarm signal is transmitted indicating a malfunctioning of the check valve if the comparison criterion is fulfilled, it is possible to indicate if there is something wrong with the check valve in an easy and efficient way. The alarm signal may indicate for an operator or user that something may be wrong with the check valve. The alarm signal is preferably transmitted to a control unit of the arrangement or to a remote control unit, wherein both the control unit and the remote control unit are configured to indicate for an operator that something may be wrong with the check valve. The determination of the data set may require that some time has passed from the time at which the close valve signal is provided to the check valve before the data set will pertain to fluid temperatures that deviates from their expected values. As readily appreciated by the person skilled in the art, this behavior occurs since the fluid, at the time of sending the close valve signal, has not yet had time to react to the conditional change, if any, introduced to the system by the sending of the close valve signal. The reaction is described by heat conduction to the surroundings for the case of a check valve is operating as expected, since the fluid, by the closure of the check valve, will be prevented from further heat exchange in the heat exchanger thereby, by heat conduction to the surroundings, over time converging towards the temperature which is outside of the fluid flow path. However, the data set may be determined also at said time position of sending the close valve signal but may for such embodiments have to be determined also at later time positions at which the fluid has had time to react to the conditional change. The monitoring of the check valve, e.g., the steps of the first aspect, may take 1 to 10 minutes to perform, preferably 3 to 7 minutes. It should however be noted that the monitoring of the check valve, e.g., the steps of the first aspect, may take longer or short time to perform as well.

By being able to identify if the check valve does not work as expected, and to identify which check valve of the arrangement these problems are related to, time spent for fault detection of the arrangement is decreased compared to conventional solutions. By being able to decrease the time spent for fault detection, the downtime of the arrangement, if any, may be decreased as well and thereby, a more cost-efficient but also energy-efficient solution is provided.

This is further advantageous as it provides for an early and exact detection of check valve issues which in turn may reduce the risk for major failure of the modular fluid-fluid heat transfer arrangement.

The comparison criterion may be fulfilled when a difference between the data set and the reference data set exceeds a threshold.

If the difference between the data set and the reference data set exceeds the threshold, the method indicates the malfunctioning of the check valve, i.e. , the method indicates that the check valve is not operating as expected.

If the difference between the data set and the reference data set is within the threshold, the check valve is considered to be operating as expected, i.e., the method indicates that the check valve is operating in a correct way, and there is no malfunctioning of the check valve.

The threshold may be set according to the properties of the heat pump arrangement, the properties of temperature sensors, the properties of the check valves etc. and therefore the particular numbers are not relevant for the inventive concept as such. That said, for typical example embodiment of the inventions, the threshold value may be within the range 0.2 °C to 3 °C, or 0.5 °C to 2 °C or 0.5 °C to 1 °C.

For these embodiments, when the check valve is provided with the close valve signal and if the check valve is working as expected, the data set pertaining to the fluid temperature of the fluid flow path may therefore follow the reference data set. If the data set is following the reference data set, the difference between the data set and the reference data set may fall below the threshold. In other words, when the check valve is working as expected, the fluid temperature is following the reference temperature.

When the check valve is provided with the close valve signal and if there are malfunctions of the check valve, the data set pertaining to the fluid temperature of the fluid flow path may deviate from the reference data set. When the data set deviates too much from the reference data set, the difference between the data set and the reference data set may exceed the threshold.

The at least one reference temperature may be at least one ambient temperature.

In this context, the ambient temperature may be a temperature within the heat pump module, just outside the heat pump module or may be a temperature outside the arrangement. The ambient temperature may be representative of a temperature to which the heat conduction and possible also heat convection at the first or second fluid flow path will depend. When the check valve is working as expected, the fluid temperature may converge towards the ambient temperature. The fluid temperature may preferably exponentially converge towards the ambient temperature. This may be referred to as the fluid temperature following Newton’s law of cooling. Thus, if the difference between the data set pertaining to the fluid temperature of the fluid flow path in response to the provision of the close valve signal to the check valve and the reference data set, wherein the reference data set is the ambient temperature, exceeds the threshold, the alarm signal is transmitted. In other words, for embodiments where the comparison criterion is fulfilled when the difference between the data set and the reference data set exceeds the threshold, and upon this difference exceeding the threshold, the fluid temperature does not converge to the ambient temperature and the alarm signal is therefore transmitted.

The ambient temperature may be determined and stored during a test period. The ambient temperature may be determined in parallel with determining the data set. The at least one reference temperature may be at least one temperature of the fluid flow path which is determined in response to a provision of a reference close valve signal to the check valve when said check valve is operating according to its specification.

Preferably, in this context, the reference temperature will converge towards the ambient temperature. This is in line with the discussion above, in which the fluid temperature converges towards the ambient temperature when the check valve is working as expected.

By the term “reference close valve signal” is here meant a signal instructing the check valve to be closed when the check valve is operating according to its specification. The term “according to its specification” is here meant that the check valve is operating as expected, i.e. , the check valve is operating according to the principles set up by the check valve manufacturer. Hence, the reference data set for these embodiments will pertain to at least one reference temperature which has been determined when the check valve is working as expected. When the check valve is operating according to its specification, there are no malfunctions of the check valve and the check valve is able to control the heat pump module in a desired way. Thereby, as the reference data set has been determined when the check valve is operating according to its specification, the reference data set has been determined when the check valve is operating in a correct way. Thus, if the difference between the data set pertaining to the fluid temperature of the fluid flow path in response to the provision of the close valve signal to the check valve and the reference data set, wherein the reference data set is a temperature of the fluid flow path which is determined in response to a provision of a reference close valve signal to the check valve when said check valve is operating according to its specification, exceeds the threshold, the alarm signal is transmitted. In other words, if the difference between the fluid temperature and the fluid temperature determined when the check valve operated according to its specification, exceeds the threshold, the fluid temperature does not converge to the ambient temperature and the alarm signal is therefore transmitted. The reference data set may be determined and stored during a test period in which the check valve is operating according to its specification. This is advantageous as it allows for ensuring that the check valve is operating according to its specification. Thereby, it allows for ensuring that the determined reference data set is a valid data set to use as a reference data set. The reference data set may be provided during one or more test periods. The reference data set may be updated at a periodical basis in order for the check valve monitoring to be as exact as possible.

A further reference data set which could be used as input to the comparison criterion which is fulfilled when a difference between the data set and the reference data set exceeds a threshold is disclosed below.

The at least one reference temperature may be determined based on at least one temperature of a fluid flow path of at least one adjacent heat pump module, wherein the at least one temperature of the at least one adjacent heat pump module is determined in response to a provision of a reference close valve signal to an associated check valve of said at least one adjacent heat pump module.

The at least one reference temperature may be determined based on at least one fluid temperature of one adjacent heat pump module only. For such embodiments, the at least one reference temperature may be the at least one fluid temperature of said one adjacent heat pump module.

Alternatively, the at least one reference temperature may be determined based on at least one fluid temperature of two or more adjacent heat pump modules. For such embodiments, the at least one reference temperature may be a function of the associated at least one fluid temperatures of said two or more adjacent heat pump modules. The function may be the arithmetic mean of the associated at least one fluid temperatures of said two or more adjacent heat pump modules.

For these embodiments, it is not required that the check valves of the adjacent heat pump modules actually operate according to its specification. In other words, a separate verification of the status of the check valve is not required. This is however based on the assumption that the probability of simultaneously having two or more faulty check valves in the arrangement is small. However, it is also conceivable that a verification is made that the check valves of each adjacent heat pump module operate according to their specification.

For other choice of reference data sets, the comparison criterion may be different.

The comparison criterion may be fulfilled when a difference between the data set and the reference data set falls below a threshold.

In this context, if the difference between the data set and the reference data set falls below the threshold, the method indicates the malfunctioning of the check valve, i.e. , the method indicates that the check valve is not operating as expected.

In this context, if the difference between the data set and the reference data set does not fall below the threshold, the check valve is considered to be operating as expected, i.e., the method indicates that the check valve is operating in a correct way.

A reference data set which could be used as input to the comparison criterion which is fulfilled when a difference between the data set and the reference data set falls below a threshold is disclosed below. The at least one reference temperature may be determined based on at least one fluid temperature of a fluid flow path of at least one adjacent heat pump module. When there are malfunctions of the check valve, the fluid temperature may correlate with a fluid temperature of other heat pump modules of the plurality of heat pump modules provided in the arrangement, preferably adjacent heat pump modules. This is because if the check valve does not work as expected, fluid may flow through the check valve towards the heat pump module. The temperature of that fluid may therefore be similar to the temperature of fluids flowing through the other heat pump modules of the arrangement. Therefore, if the check valve does not work as expected, the data set pertaining to the temperature of the fluid flow path may correlate with the fluid temperature of adjacent heat pump modules. Thus, as said above, when there are malfunctions of the check valve, the fluid temperature correlates with the fluid temperature of other, e.g., adjacent, heat pump modules. In other words, if the check valve is working as expected the fluid temperature of the fluid flow path of the heat pump module should have bad a correlation with the fluid temperature of the fluid flow path of other heat pump modules.

Each heat pump module of the plurality of heat pump modules may comprise a refrigerant circulation path which includes a first heat exchanger unit, a compressor, a second heat exchanger unit and an expander being connected to one another in a sequence, wherein the first fluid flow path may extend through the first heat exchanger unit and the second fluid flow path may extend through the second heat exchanger unit.

The first heat exchanger unit, the compressor, the second heat exchanger unit and the expander may be referred to as components of the heat pump arrangement as discussed above. Each heat pump module may comprise different types of sensors configured to monitor or detect the heat pump module or the arrangement. Each heat pump module may comprise one or more pumps configured to ensure that fluid in the heat pump module is always available where needed. It should however be noted that the heat pump module may comprise other components as well.

The method steps (a) to (d) may be performed in a sequence for each of the plurality of heat pump modules.

This is advantageous as it allows for monitoring the check valve condition for one check valve at a time such that it is possible to identify malfunction of the specific check valve in the arrangement in an easy and efficient way. The term “sequence” is here meant that one check valve of the arrangement is provided with the close valve signal at the time. Another check valve may be checked when the previous check valve has been checked. Thus, the check of the previous check valve may have to be completed before the check of the next check valve is provided.

This is further advantageous as it allows the monitoring of the check valve condition to be provided under a normal operation mode of the arrangement, except that the heat pump module associated with the monitoring is not operating. Thus, there is no need of interruption of operation of the arrangement when providing the check valve monitoring. Preferably, the operated heat pump modules may be ramped up, if possible, such that the arrangement has the same output as before although running with fewer heat pump modules during the monitoring check.

When the arrangement is operating in the normal operation mode, each heat pump module may be in operation and the power for each heat pump module may be controlled according to predetermined control laws. The control laws may be configured to control the operation of the associated heat pump module to operate in a normal heat pump module operation mode such that the arrangement is operating in the normal operation mode. The normal operation mode may include a common heat pump module operation mode of operating all heat pump modules of the plurality of heat pump modules in a similar way. For such a case, the common heat pump module operation mode may be defined by an input power, i.e. , compressor capacity, being common for all heat pump modules of the plurality of heat pump modules. This implies that every heat pump module is always operating at the same input power.

The control law may further comprise individually controlling the operation of each heat pump module of the plurality of heat pump modules to allow operating each heat pump module at a respective heat pump module operation mode.

The respective heat pump operation 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 50% of the maximum arrangement output power, each heat pump module should operate with 50% 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 .5 kW and the other one with 3 kW.

The respective heat pump module operation 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.

The control laws may be configured to control the operation of the associated heat pump module, by operating a circulation pump of the associated heat pump module to operate the arrangement in a normal operation mode such that the heat pump module is operating in the common heat pump operation mode or in the respective heat pump module operation mode. Each heat pump module may comprise a circulation pump.

The modular fluid-fluid heat transfer arrangement may further comprise, for each of the plurality of heat pump modules, one or more temperature sensors arranged to measure at least the fluid temperature of the fluid flow path.

This is advantageous as it allows for determining the fluid temperature in an easy and accurate way. The data set may be determined by using the fluid temperature determined by the one or more temperature sensors. If the arrangement comprises more than one temperature sensor for each heat pump module, these temperature sensors may be configured to determine the same fluid temperature or different fluid temperatures of the fluid flow path. By determining the same fluid temperature by using different temperature sensors provides for an accurate measurement of the fluid temperature. By determining different fluid temperatures of the fluid flow path by using different temperature sensors provides for a greater knowledge of the heat pump module and the fluid temperature. By the term “different fluid temperatures” is here meant fluid temperatures provided at different locations in the heat pump module or at different time positions.

The modular fluid-fluid heat transfer arrangement may further comprise, for each of the at least one heat pump module, two temperature sensors arranged to measure a fluid temperature of the first fluid flow path and a temperature of the second fluid flow path, respectively. This is advantageous as it allows for a better knowledge of the heat pump module and the arrangement.

The temperature sensor allows obtaining data sets pertaining to the fluid temperature. This should be interpreted broadly to encompass any temperature sensor capable of providing temperature-based data. The temperature sensor may be in physical contact with the fluid, such as a thermometer, thermocouple, thermistor etc. However, the temperature sensor may alternatively be based on remote sensing, such as e.g., spectrally resolved IR imaging or the like. Irrespective of which technique is chosen, the data set will relate to the temperature of the fluid and thereby be useful to be compared to reference data in the method of the disclosure. It should be noted that other sensors capable of providing temperature-based data may be used as well.

The modular fluid-fluid heat pump arrangement may further comprise a control unit configured to control an operation of each of the plurality of heat pump modules.

By the term “control unit” is here meant any device or unit configured to control an operation of the plurality of heat pump modules. Preferably, the arrangement comprises one control unit which is configured to control the operation of each of the plurality of heat pump modules. It should however be noted that each heat pump module may have a respective control unit which is configured to control the operation of the associated heat pump module. The control unit may be e.g., a microprocessor or a central processing unit, CPU. The control unit may be configured to control the power and enablement of the heat pump module operation. The control unit may be wired, or wireless connected to each of the heat pump modules.

One or more of the method steps according to the first aspect may be performed by, or at least initiated by, the control unit. This is advantageous as it allows for the method steps to be performed in an efficient way in which one or more of the method steps are performed or initiated by the same unit. If all method steps are performed or initiated by the control unit, there is no need to transmit information between a lot of different units in the arrangement, but all information is obtained by the control unit.

The control unit may be configured to obtain, for each heat pump module, the data set pertaining to the fluid temperature of the fluid flow path of the associated heat pump module. The control unit may also be configured to obtain the reference data set pertaining to the reference temperature. Each temperature sensor may be connected to the control unit thus allowing the control unit to obtain measured fluid temperature data.

The method may be performed in response to that at least one heat pump module of the plurality of heat pump modules receiving a trigger signal or at a periodical basis.

The trigger signal may be output from, or at least initiated by, the control unit. The trigger signal may be an output in response to an error event being detected in one of the heat pump modules. The trigger signal may be an output in response to a request from a remote server or the control unit which may trigger the monitoring check to be performed.

This is advantageous as it allows for detecting if the check valves are operating in a desired way at all times. This is further advantageous as it allows to detect if something is wrong with the arrangement, and especially with the check valves of the arrangement.

If the method according to the first aspect is performed at a periodical basis, this may be once an hour, once a day or once a week. Other periodical bases may be used as well.

If the alarm signal is transmitted, the method may further comprise operating the modular fluid-fluid heat pump arrangement in a fallback operation mode being different from a normal operation mode of the modular fluid-fluid heat pump arrangement.

By being able to apply the fallback operation mode, the arrangement may continue its operation although one or more check valves have been determined to be broken. Thus, an improved robustness of the arrangement is achieved. As said above, the control unit may be configured to control the power and enablement of the operation of the heat pump module and may thus be configured to operate the arrangement in the fallback operation mode.

When the arrangement is operating in the fallback operation mode, the arrangement is operating in an operation mode which is different from the normal operation mode. By way of example, one or more of the heat pump modules may not be in operation. This may be the case if a malfunction of the check valve has been indicated. If this is the case, the operated heat pump modules may be ramped up, if possible, such that the arrangement has the same output power as before although running with fewer heat pump modules. If one or more heat pump modules has to be removed from the arrangement, the number of heat pump modules may be decreased by one i.e. , N=N-1 (herein, N is the number of heat pump modules provided in the arrangement). Thereby, the control unit may be configured to operate all heat pump modules with a check valve that is working as expected and the one or more heat pump modules which has a check valve which is not working as expected may be closed.

This is advantageous as it allows for the arrangement to operate in a desired way at the same time as one or more of the check valves may be checked, and if needed, replaced.

The fallback mode may be defined as controlling a circulation pump for all heat pump modules of the arrangement, including the heat pump module having a check valve which is not working as expected, such that all heat pump modules have the same flow.

If the comparison criterion is not fulfilled, the method may comprise providing an open valve signal to the check valve.

As said above, if the comparison criterion is not fulfilled, the check valve is considered to operate as expected. If the check valve operates as expected, the check valve may open the fluid flow path. This may be provided by, or at least initiated by, that the check valve receives the open valve signal. The open valve signal may instruct the check valve to open the fluid flow path and thereby the associated heat pump module. The modular fluid-fluid heat transfer arrangement may comprise, for each of the plurality of heat pump modules, two check valves arranged in the first fluid flow path and in the second fluid flow path, respectively.

This is advantageous as it allows for an improved robustness of the arrangement. If one of the check valves are determined to be broken and the other one is determined to be working as expected, it is possible to continue the operation of the heat pump module since only one check valve of each heat pump module is required.

This is further advantageous as it allows for an improved flexibility of the arrangement and especially the controlling of the respective heat pump module. By being able to control the heat pump modules in a more flexible way, it may also be possible to monitor the check valve condition in a more flexible way.

The data set may comprise a data set curvature including a time series pertaining to the fluid temperature of the fluid flow path over time.

By providing time-resolved temperature data, it is possible to improve knowledge about the temperature variations within the heat pump module over time. The data set curvature may comprise a plurality of data set points pertaining to the fluid temperature over time. The data set curvature may comprise a continuous data set pertaining to the fluid temperature over time. In this context, the term “over time” may refer to a plurality of seconds up to an hour. Preferably, the term “over time” refer to a plurality of minutes such as 1 to 10 minutes. This is advantageous as it allows for a check valve monitoring which is easy and exact.

The reference data set may comprise a reference data set curvature including a respective time series pertaining to the fluid temperature of the fluid flow path over time wherein said time series is obtained in response to a provision of a reference close valve signal to the check valve when the check valve is operating according to its specification.

By providing time-resolved temperature reference data, it is possible to improve knowledge about the temperature variations within the heat pump module over time when the check valve is operating according to its specification. Thus, the knowledge about how the temperature variations in the heat pump module behave when the check valve is operating according to its specification is improved. The reference data set curvature may comprise a plurality of reference data set points pertaining to the reference temperature over time. The reference data set curvature may comprise a continuous reference data set pertaining to the fluid temperature over time. The term “over time” is here meant during preferably a plurality of seconds but may also mean during a plurality of minutes. This is advantageous as it allows for a check valve monitoring which is easy and exact.

By having the data set comprising the data set curvature and the reference data set comprising the reference data set curvature provides for that the comparison step in the method according to the first aspect may be provided in an exact and efficient way. Preferably, the data set curvature and the reference data set curvature are provided in a similar way such that the comparison step may be provided in an easy and accurate way.

The reference data set may be defined by a reference data set vector for the time series output. If that is the case, the method may further comprise, prior to comparing the data set and the reference data set, generating a first data set vector for the time series output.

The data set and the reference data set may be compared for the respective speeds and/or deviations of the change in time.

This is advantageous as it allows for an exact and efficient comparison step and hence also an exact determined difference between the data set and the reference data set.

According to a second aspect of the disclosure, these and other objects are also achieved in full or at least in part, by a modular fluid-fluid heat transfer arrangement comprising: a plurality of heat pump modules, each of the plurality of heat pump modules being fluidly connected to a first fluid grid via a respective first fluid flow path and to a second fluid grid via a respective second fluid flow path; for each of the plurality of heat pump modules, a check valve arranged in a fluid flow path selected from the respective first fluid flow path and the respective second fluid flow path of that heat pump module, said check valve being configured to selectively close said fluid flow path, and a control unit which is configured to, for each of the plurality of heat pump modules: provide a close valve signal to the check valve; determine a data set pertaining to a fluid temperature of the fluid flow path; and compare the data set with a reference data set pertaining to at least one reference temperature; upon the comparison fulfilling a comparison criterion: transmit an alarm signal for indicating a malfunctioning of said check valve.

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. The disclosure may also in short be said to relate to a method for monitoring a check valve condition in a modular fluid-fluid heat transfer arrangement which comprises a plurality of heat pump modules and, for each of the heat pump modules, a check valve arranged in a fluid flow path of the heat pump module and configured to selectively close the fluid flow path, the method comprising: providing a close valve signal to the check valve; determining a data set pertaining to a fluid temperature of the fluid flow path; comparing the data set with a reference data set pertaining to at least one reference temperature of the fluid flow path; and if a difference between the data set and the reference data set exceeds a threshold: transmitting an alarm signal for indicating a malfunctioning of said check valve.

Brief description of the drawings

The disclosure 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 is a flowchart illustrating a method for monitoring a check valve condition in 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.

With reference to figure 1 , a modular fluid-fluid heat transfer arrangement 100 is illustrated by way of example. The modular fluid-fluid heat transfer arrangement 100 is preferably for heating and/or cooling and/or providing tap water to buildings or the like. Here after, the modular fluid-fluid heat transfer arrangement 100 is also referred to as “heat transfer arrangement 100” or “arrangement 100”.

The heat transfer arrangement 100 has a first side 161 and a second side 162. The heat transfer arrangement 100 comprises, at the first sidel 61 , a first fluid grid 111. The heat transfer arrangement 100 is connected, by the first side 161 , to a first fluid side 101 via the first fluid grid 111. The heat transfer arrangement 100 further comprises, at the second side 162, a second fluid grid 112. The heat transfer arrangement 100 is connected, at the second side 162, to a second fluid side 102 via the second fluid grid 112. The first fluid grid 111 may comprise first inlet and outlet junction pipes 113, 114. The second fluid grid 112 may comprise second inlet and outlet junction pipes 115,116. The first fluid side 101 may be a cold fluid side or a hot fluid side. The second fluid side 102 may be a cold fluid side or a hot fluid side. Preferably, one fluid side of the first and second fluid side 101 , 102 is the cold fluid side and the other one of the first and second fluid sides 101 , 102 is the hot fluid side.

The heat transfer arrangement 100 further comprises two heat pump modules 130a, 130b. It should be noted that the heat transfer arrangement 100 may comprise more than two heat pump modules. The respective heat pump module 130a, 130b is connected to the first fluid grid 111 via a respective first fluid flow path 121 . The respective heat pump module 130a, 130b is connected to the second fluid grid 112 via a respective second fluid flow path 122. The first and second fluid flow paths 121 , 122 are defined by a respective non-solid line. The fluid flow paths 121 , 122 which extends through the heat pump module 130a are illustrated with dotted lines. The fluid flow paths 121 , 122 which extends through the heat pump module 130b are illustrated with dashed lines. It should be noted that the fluid flow path 121 , 122 which extends through the heat pump module 130a are separated from the fluid flow paths 121 , 122 which extends through the heat pump module 130a, 130b.

The first fluid grid 111 is configured to supply a first side fluid from the first fluid side 101 to the heat transfer arrangement 100. The first fluid grid 111 is further configured to return the first side fluid from the heat transfer arrangement 100 to the first fluid side 101. If the first fluid side 101 is a cold fluid side, and energy should be retrieved therefrom, the first side fluid may be colder when being returned to the first fluid side 101 than when being supplied from the first fluid side 101 .

The second fluid grid 112 is configured to supply a second side fluid from the heat transfer arrangement 100 to the second fluid side 102. The second fluid grid 112 is further configured to return the second side fluid from the second fluid side 102 to the heat transfer arrangement 100. If the second fluid side 102 is the hot fluid side, and energy should be supplied thereto, the first side fluid may be colder when being returned to the second fluid side 102 than when being supplied to the second fluid side 102.

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

As introduced above, the heat transfer arrangement 100 comprises two heat pump modules 130a, 130b. Each heat pump module 130a, 130b 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 fluid grid 111. The first inlet and outlet ports 131a, 131b are connected to the first fluid grid 111 via the first inlet and outlet junction pipes 113, 114. respectively. The second inlet and outlet ports 132a, 132b are connected to the second fluid grid 112. The second inlet and outlet ports 132a, 132b are connected to the second fluid grid 112 via the second inlet and outlet junction pipes 115, 116 respectively.

When the heat transfer arrangement 100 is in use, the two heat pump modules 130a, 130b 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 113, 114 respectively, and by their respective second inlet and outlet ports 132a, 132b which are connected to the second inlet and outlet junction pipes 115, 116, respectively.

Each heat pump module 130a, 130b further comprises a refrigerant recirculation loop 134. The refrigerant recirculation loop 134 comprises a first heat exchanger unit 135 and a second heat exchanger unit 137 as well as a compressor 136 and an expander 138. The first heat exchanger unit 135 is fluidly connected to the first inlet and outlet ports 131a, 131b. Thus, the first heat exchanger 135 is connected to the first inlet and outlet junction pipes 113, 114 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 132a, 132b. Thus, the second heat exchanger unit 137 is connected to the second inlet and outlet junction pipes 115, 116 via the second inlet and outlet ports 132a, 132b, 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. If the first fluid side 101 is the cold fluid side, the refrigerant and the first side fluid are configured to exchange thermal energy between each other in the first heat exchanger unit 135 such that a temperature of the refrigerant increases and a temperature of the first side fluid decreases. The first side fluid is circulated from the first heat exchanger 135 to the first fluid side 101 . 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 supplying the refrigerant to the second heat exchanger unit 137. If the second fluid side 102 is the hot fluid side, the refrigerant and the second side fluid is configured to exchange thermal energy between each other in the second heat exchanger unit 137 such that a temperature of the refrigerant decreases and a temperature of the second side fluid increases.

The second side fluid is circulated in from the second heat exchanger unit 137 to the second 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.

The arrangement 100 further comprises, for each of the heat pump modules 130a, 130b, a check valve 140a, 140b. The check valve 140a, 140b is arranged in a fluid flow path selected from the respective first fluid flow path 121 or the second fluid flow path 122 of the heat pump module 130a, 130b. As illustrated in figure 1 , the arrangement 100 comprises, for each of the heat pump modules 130a, 130b, two check valves 140a, 140b, wherein one check valve 140a is arranged in the first fluid flow path 121 and another check valve 140b is arranged in the second fluid flow path 122. As further illustrated, in the upper heat pump module 130a (herein upper is only used for illustrative purposes), one check valve 140a is arranged at the inlet junction pipe 113 of the first fluid flow path 121 and the other check valve 140b is arranged at the inlet junction pipe 115 of the second fluid flow path 122. As further illustrated, in the lower heat pump module 130b (herein lower is only used for illustrative purposes), one check valve 140a is arranged at the outlet junction pipe 114 of the first fluid flow path 121 and the other check valve 140b is arranged at the outlet junction pipe 116 of the second fluid flow path 122. It should however be noted that these are only exemplified arrangements and the check valves 140a, 140b may be arranged in other ways as well, i.e., one at the inlet junction pipe 113 of the first fluid flow path 121 and one at the outlet junction pipe 114 of the first fluid flow path 121 or one at the inlet junction pipe 113 of the first fluid flow path 121 and one at the outlet junction pipe 116 of the second fluid flow path 122. The check valve 140a, 140b is configured to selectively close the fluid flow path (i.e., the first or second fluid flow path 121 , 122). Although not illustrated, the arrangement 100 may comprise, for each heat pump module 130a, 130b, one check valve 140a, 140b arranged in either the first fluid flow path 121 or the second fluid flow path 122.

The first fluid flow path 121 may extend through the first heat exchanger unit 135 and the second fluid path 122 may extend through the second heat exchanger unit 137.

The arrangement 100 further comprises, for each heat pump module 130a, 130b, two temperature sensors 150. It should however be noted that the arrangement 100 may comprise, for each heat pump module 130a, 130b, one temperature sensor or more than two temperature sensors. Each temperature sensor 150 is configured to measure at least a fluid temperature of the fluid flow path (i.e., the first or second fluid flow path 121 , 122). As illustrated in figure 1 , the temperature sensor 150 may be arranged at different positions in the heat pump module 130a, 130b. Hence, the temperature sensor 150 may be arranged at the inlet junction pipes 113, 115 of the fluid flow paths 121 , 122 or at the outlet junction pipes 114, 116 of the fluid flow paths 121 , 122. The arrangement 100 may comprise further temperature sensors (not illustrated) arranged to determine the ambient temperature of the heat pump module 130a, 130b or the arrangement 100. By way of example, the further temperature sensors may be arranged in the heat pump module 130a, 130b. The further temperature sensors may not be in contact with the fluid of the fluid flow paths 121 , 122.

The arrangement 100 further comprises a control unit 133. The control unit 133 is configured to control an operation of each of the heat pump modules 130a, 130b. The control unit 133 may be wired, or wireless connected to the heat pump modules 130a, 130b. The temperature sensor 150 may be connected to the control unit 133, either wired or wirelessly. The further temperature sensors may be connected to the control unit 133, either wired or wirelessly.

The control unit 133 may be configured to determine a data set pertaining to the fluid temperature of the fluid flow path 121 , 122. The data set may comprise a data set curvature including a time series pertaining to the fluid temperature of the fluid flow path over time.

The control unit 133 may be configured to obtain a reference data set pertaining to a reference temperature. The reference temperature may for some example embodiments be the at least one ambient temperature of the heat pump module 130a, 130b or the arrangement 100. The reference temperature may for some example embodiments be at least one temperature of the fluid flow path 121 , 122. The reference temperature may for some example embodiments be at least one fluid temperature of a fluid flow path 121 , 122 of at least one adjacent heat pump module 130a, 130b. The reference data set may comprise a reference data set curvature including a respective time series pertaining to the fluid temperature of the fluid flow path over time wherein said time series is obtained in response to a provision of a reference close valve signal to the check valve when the check valve is operating according to its specification. The reference data set may be determined and stored during a test period. If the reference data set is determined and stored during the test period in which the check valve 140a, 140b is operating according to its specification, it implies that the reference data set is determined at a time where it is made sure that the check valve 140a, 140b is operating according to its specification. This may be tested by using further test equipment at that time such as flow meters and/or position sensors.

With reference to figure 2, a flowchart illustrating a method 200 for monitoring a check valve condition in a modular fluid-fluid heat transfer arrangement 100 is shown by way of example. The modular fluid-fluid heat transfer arrangement 100 corresponds to the arrangement 100 as introduced in connection with figure 1 .

The method 200 comprises (a) providing a close valve signal to the check valve 140a, 140b. Thereafter, the method 200 comprising (b) determining a data set pertaining to the fluid temperature of the fluid flow path in response to a provision of the close valve signal to the check valve 140a, 140b. Thereafter, the method 200 comprises (c) comparing the data set with a reference data set. The reference data set pertaining to at least one reference temperature. In a step (d), upon the comparison fulfilling a comparison criterion, the method 200 further comprising transmitting S201 an alarm signal for indicating a malfunction of the check valve 140a, 140b.

The reference data set may be determined in different ways, as will be detailed below. It is understood that the reference data set, independent on which way it is determined, will describe the estimated and/or expected behavior of the data set for a situation where the check valve is operating as expected or for a situation where the check valve is not operating as expected. Thus, the reference data set will reflect an estimation of the temperature behavior of the heat pump module for one of the two situations: check valve is actually closed, and check valve is still open I was not able to close.

The comparison criterion may be determined in different ways. By way of example, the comparison criterion may be fulfilled when a difference between the data set and the reference data set exceeds a threshold. The threshold may be set according to the properties of the heat transfer arrangement 100, the properties of the temperature sensors 150, the properties of the check valves 140a, 140b etc. and therefore the particular numbers are not relevant for the inventive concept as such. That said, for typical example embodiment of the inventions, the threshold value may be within the range 0.2 °C to 3 °C, or 0.5 °C to 2 °C or 0.5 °C to 1 °C.

As said above, the reference temperature may be at least one ambient temperature. If that is the case, the reference data set may be determined in advance, i.e. , be predetermined, or at the same time as when performing the rest of the method steps. Optionally, the at least one reference temperature is at least one temperature of the fluid flow path which is determined in response to a provision of a reference close valve signal to the check valve 140a, 140b when said check valve 140a, 140b is operating according to its specification. This implies that the at least one reference temperature may be determined in advance, i.e. be predetermined, for a particular heat pump module at an occasion where it could be made certain that the check valve operated according to its specification. This could for example be achieved by performing calibration measurements during system maintenance. The correct operation of the check valve could for example be verified by measuring the flow rate in the fluid flow path 121 , 122 by means of a flow meter. The at least one reference temperature may, after an optional processing thereof, be stored in the modular fluid-fluid heat transfer arrangement 100, or in any peripheral device being accessible from said arrangement 100. Thus, for example embodiments utilizing this way of determining the reference data set, the determination is not made when performing the method per se and has instead to be made earlier.

As an alternative to the above-described way of determining the reference data set, the combined information from the plurality of heat pump modules may be used. This method differs from the above-described method in that the reference data set may be determined at the same time as when performing the rest of the method steps.

Optionally, the at least one reference temperature may be determined based on at least one temperature of a fluid flow path of at least one adjacent heat pump module 130b, wherein the at least one temperature of the at least one adjacent heat pump module 130b is determined in response to a provision of a reference close valve signal to an associated check valve 140a, 140b of said at least one adjacent heat pump module 130b. The at least one reference temperature may be determined based on at least one fluid temperature of one adjacent heat pump module 130b only. For such embodiments, the at least one reference temperature may be the at least one fluid temperature of said one adjacent heat pump module130b. Alternatively, for embodiments having three or more heat pump modules (not shown), thereby having two or more adjacent heat pump modules to the heat pump module that is being tested, the at least one reference temperature may be determined based on at least one fluid temperature of two or more adjacent heat pump modules. For such embodiments, the at least one reference temperature may be a function of the associated at least one fluid temperatures of said two or more adjacent heat pump modules. The function may be the arithmetic mean of the associated at least one fluid temperatures of said two or more adjacent heat pump modules. It is conceivable that the arithmetic mean is taken for all temperature values of each associated at least one fluid temperature, thereby resulting in a scalar. However, preferably, the arithmetic mean is taken between groups of temperature values which are expected to have similar values. For example, if the adjacent heat pump modules are identically or at least similarly constructed, it is reasonable to expect that the temperature value from a temperature sensor of one of these adjacent heat pump modules will be close to a temperature value of another adjacent heat pump module at a specific point in time after the close valve signal was received by the check valve. Temperature values from such corresponding sensors may advantageously be averaged to provide a mean temperature on which the reference data set may be based.

For the embodiments described hereinabove, the comparison criterion will be fulfilled when the data set differs from the reference data set, which may occur when the temperature of the fluid flow path at which the tested check valve 140a, 140b is arranged deviates “enough” (as determined by the threshold) from the reference temperature, which could be e.g. the ambient temperature. As readily appreciated by the person skilled in the art, a fluid temperature which does not agree with the ambient temperature will indicate that the tested check valve 140a, 140b has not been closed in spite of the check valve 140a, 140b receiving instructions to do close.

Optionally, for other choice of reference data sets, the comparison criterion may be different. The comparison criterion may be fulfilled when a difference between the data set and the reference data set falls below a threshold. A reference data set which could be used as input to this comparison criterion is that the reference temperature may be determined based on at least one fluid temperature of a fluid flow path of at least one adjacent heat pump module. Thus, contrary to the previously described embodiments, the comparison criterion will for the present embodiment be fulfilled when the data set is equal to or at least close to the reference data set, which may occur when the temperature of the fluid flow path at which the tested check valve 140a, 140b is arranged does not deviate “enough” (as determined by the threshold) from the temperature(s) of the fluid flow path(s) of adjacent heat pump module(s) 130a, 130b. As readily appreciated by the person skilled in the art, a similar fluid temperature will indicate that the tested check valve 140a, 140b has not been closed in spite of the check valve 140a, 140b receiving instructions to close.

Optionally, the method steps (a) to (d) may be performed in a sequence for each of the plurality of heat pump modules 130a, 130b. Thus, for this example embodiment, all check valves 140a, 140b are checked when monitoring the check valve condition.

The method 200 may be performed in response to that at least one heat pump module 130a, 130b of the arrangement 100 receives a trigger signal. The trigger signal may be received from an operator or from the control unit 133. The method 200 may be performed at a periodical basis.

If the alarm signal is transmitted, the method 200 may further comprise operating S203 the modular fluid-fluid heat transfer arrangement 100 in a fallback operation mode. The fallback operation mode may be different from a normal operation mode of the arrangement 100. The fallback operation mode may e.g., be to operate the heat pump module at a lower power.

If the comparison criterion is not fulfilled, i.e., if the alarm signal is not transmitted, the method 200 may further comprise providing S202 an open valve signal to the check valve 140a, 140b.

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

As previously mentioned, in case of a malfunction of the check valve 140a, 140b, the fluid in the first or second fluid grid 111 , 112 may continue to flow, resulting in a different fluid temperature time decay than for the reference data set where the temperature, as a result from the closed check valve 140a, 140b, will follow the fluid temperature time decay of water standing completely still, i.e. , a temperature time decay determined by heat conduction to the surroundings.

A relatively inexpensive and straight-forward implementation of the method of the disclosure is to determine the data set based on input data from a single temperature sensor 150. The data set may thus include one or more temperature values of the temperature of the fluid at the position of that temperature sensor 150. By providing a reference temperature which is at least one ambient temperature, the comparison step may be carried out by taking the difference between the data set and the reference data set thus resulting in one or more temperature differences.

A further relatively inexpensive and straight-forward implementation of the method of the disclosure is to determine the data set based on input data from a single temperature sensor 150. The data set may thus include one or more temperature values of the temperature of the fluid at the position of that temperature sensor 150. By providing a reference data set for the same sensor choice and setup, a reference data set which is typically predetermined for that heat pump module 130a, 130b, the comparison step may be carried out by taking the difference between the data set and the reference data set thus resulting in one or more temperature differences. Temperature(s) of the data set and reference data set at a time period after the close valve signal was provided to the check valve 140a, 140b is typically chosen to be able to identify the difference in fluid temperature decay time.

Alternatively, more complex comparisons including for example mathematical operations, such as averaging, etc. can be used. The data set may include a plurality of temperature values as function of time, i.e., a time- resolved temperature curve. The reference data set may therefore also include a plurality of temperature values as function of time predetermined at a time where the check valve 140a, 140b was operating according to its specification. The comparison step may include taking the difference between temperature values of the data set and temperature values of the reference data set at different time positions after the close valve signal was sent to the check valve 140a, 140b. Alternatively, the time-resolved curves may be compared by more sophisticated algorithms such as curve fitting analysis etc.

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 may 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.

Claims

1. A method (200) for monitoring a check valve condition in a modular fluid-fluid heat transfer arrangement (100) which comprises a plurality of heat pump modules (130a, 130b), each of the plurality of heat pump modules

(130a, 130b) being fluidly connected to a first fluid grid (111 ) via a respective first fluid flow path (121 ) and to a second fluid grid (112) via a respective second fluid flow path (122), and wherein the modular fluid-fluid heat transfer arrangement (100) further comprises, for each of the plurality of heat pump modules (130a, 130b), a check valve (140) arranged in a fluid flow path selected from the respective first fluid flow path (121 ) or the respective second fluid flow path (122) of the heat pump module (130a, 130b), said check valve (140a, 140b) being configured to selectively close said fluid flow path, the method (200) comprising: for at least one of the plurality of heat pump modules:

(a) providing a close valve signal to the check valve (140a, 140b);

(b) determining a data set pertaining to a fluid temperature of the fluid flow path in response to a provision of the close valve signal to the check valve (140a, 140b); and

(c) comparing the data set with a reference data set pertaining to at least one reference temperature;

(d) upon the comparison fulfilling a comparison criterion, transmitting (S201 ) an alarm signal for indicating a malfunctioning of said check valve (140a, 140b).

2. The method (200) according to claim 1 , wherein the comparison criterion is fulfilled when a difference between the data set and the reference data set exceeds a threshold.

3. The method (200) according to claim 1 or 2, wherein the at least one reference temperature is at least one ambient temperature.

4. The method (200) according to claim 1 or 2, wherein the at least one reference temperature is at least one temperature of the fluid flow path which is determined in response to a provision of a reference close valve signal to the check valve (140a, 140b) when said check valve (140a, 140b) is operating according to its specification.

5. The method (200) according to any one of the preceding claims, wherein each heat pump module (130a, 130b) of the plurality of heat pump modules (130a, 130b) comprises a refrigerant circulation path (134) which includes a first heat exchanger unit (135), a compressor (136), a second heat exchanger unit (137) and an expander (138) being connected to one another in a sequence, wherein the first fluid flow path (121 ) extends through the first heat exchanger unit (135) and the second fluid path (122) extends through the second heat exchanger unit (137).

6. The method (200) according to any one of the preceding claims, wherein the method steps (a) to (d) are performed in a sequence for each of the plurality of heat pump modules (130a, 130b).

7. The method (200) according to any one of the preceding claims, wherein the modular fluid-fluid heat transfer arrangement (100) further comprises, for each of the plurality of heat pump modules (130a, 130b), one or more temperature sensors (150) arranged to measure at least the fluid temperature of the fluid flow path.

8. The method (200) according to any one of the preceding claims, wherein the modular fluid-fluid heat pump arrangement (100) further comprises a control unit (133) configured to control an operation of each of the plurality of heat pump modules (130a, 130b).

9. The method (200) according to any one of the preceding claims, wherein the method (200) is performed in response to that at least one heat pump module of the plurality of heat pump modules (130a, 130b) receiving a trigger signal or at a periodical basis.

10. The method (200) according to any one of the preceding claims, wherein, if the alarm signal is transmitted, the method (200) further comprises operating (S203) the modular fluid-fluid heat pump arrangement (100) in a fallback operation mode being different from a normal operation mode of the modular fluid-fluid heat pump arrangement (100).

11 . The method (200) according to any one of the preceding claims, wherein, if the comparison criterion is not fulfilled, the method comprises providing (S202) an open valve signal to the check valve (140a, 140b).

12. The method (200) according to any one of the preceding claims, wherein the modular fluid-fluid heat transfer arrangement (100) comprises, for each of the plurality of heat pump modules (130a, 130b), two check valves (140a, 140b) arranged in the first fluid flow path (121 ) and in the second fluid flow path (122), respectively.

13. The method (200) according to any one of the preceding claims, wherein the data set comprises a data set curvature including a time series pertaining to the fluid temperature of the fluid flow path over time.

14. The method (200) according to any one of the preceding claims, wherein the data set and the reference data set is compared for the respective speeds and/or deviations of the change in time.

15. A modular fluid-fluid heat transfer arrangement (100) comprising: a plurality of heat pump modules (130a, 130b), each of the plurality of heat pump modules (130a, 130b) being fluidly connected to a first fluid grid

(111 ) via a respective first fluid flow path (121) and to a second fluid grid

(112) via a respective second fluid flow path (122); for each of the plurality of heat pump modules (130a, 130b), a check valve (140a, 140b) arranged in a fluid flow path selected from the respective first fluid flow path (121 ) or the respective second fluid flow path (122) of that heat pump module (130a, 130b), said check valve (140a, 140b) being configured to selectively close said fluid flow path, and a control unit (133) which is configured to, for at least one of the plurality of heat pump modules: provide a close valve signal to the check valve (140a, 140b); determine a data set pertaining to a fluid temperature of the fluid flow path; and compare the data set with a reference data set pertaining to at least one reference temperature; upon the comparison fulfilling a comparison criterion: transmit an alarm signal for indicating a malfunctioning of said check valve (140a, 140b).