(19)
(11) EP 4 545 878 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication:
30.04.2025 Bulletin 2025/18

(21) Application number: 24209144.5

(22) Date of filing: 28.10.2024
(51) International Patent Classification (IPC): 
F25B 30/02(2006.01)
F25B 40/02(2006.01)
F25B 49/02(2006.01)
 F25B 31/00(2006.01)
F25B 40/06(2006.01)
(52) Cooperative Patent Classification (CPC):
F25B 30/02; F25B 31/004; F25B 49/02; F25B 2700/21151; F25B 40/02; F25B 40/06; F25B 2400/07; F25B 2400/054; F25B 2400/13
(84) Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC ME MK MT NL NO PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA
Designated Validation States:
GE KH MA MD TN

(30) Priority: 27.10.2023 NL 2036141

(71) Applicant: Dutek Group B.V.
7951NE Staphorst (NL)

(72) Inventors:
  • BELTMAN, Sander Gerardus
    7951 NE STAPHORST (NL)
  • WIELINK, Hendrik
    7951 NE STAPHORST (NL)

(74) Representative: Arnold & Siedsma 
Bezuidenhoutseweg 57
2594 AC The Hague
2594 AC The Hague (NL)

   


(54) HEAT PUMP AND METHOD FOR HEATING AND/OR COOLING


(57) The invention relates to a heat pump comprising:
- an evaporator;
- at least one compressor that is positioned downstream of the evaporator and is connected to the evaporator by a gas conduit;
- a condenser that is positioned downstream of the compressor and is operatively connected thereto;
- at least one expander that is positioned downstream of the condenser and is connected thereto by a liquid conduit; and
- a suction gas heat exchanger that is operatively connected to the gas conduit and the liquid conduit.
The invention further relates to a heating and/or cooling system and to a method for generating heat and/or cold.




Description


[0001] The invention relates to a heat pump, a heating and/or cooling system and a method for heating and/or cooling.

[0002] Heat pumps are known from practice and are increasingly used to heat and/or cool buildings. An advantage of heat pumps is that the amount of fossil fuel to heat a building is significantly reduced and, in some cases, even leads to the use of fossil fuel being obviated altogether. Another advantage is that heat pumps can also be used to supply cold to a building during warmer (or hot) weather.

[0003] Although heat pumps are more efficient than traditional gas-based heating systems, the increasing need for energy reduction and more sustainable heating systems require heat pumps that have an increased efficiency.

[0004] Another advantage of the known heat pumps is that the efficiency thereof decreases with an increase in the distribution temperature. In other words, heat pump are most useful when applied in low temperature (LT) heating systems, such as systems having a distribution temperature of up to 50 °C.

[0005] As many buildings have heating systems adjusted to higher distribution temperatures, such as temperatures of 60 °C and even up to 80 °C,

[0006] Therefore, there is a need for heat pumps having an increased efficiency, which preferably can also be used to provide heat to high temperature (HT) heating systems.

[0007] The present invention is aimed at obviating or at least reducing the aforementioned problems by providing a heat pump comprising:
  • an evaporator;
  • at least one compressor that is positioned downstream of the evaporator and is connected thereto by a gas conduit;
  • a condenser that is positioned downstream of the compressor and is operatively connected thereto;
  • at least one expander that is positioned downstream of the condenser and is connected thereto by a liquid conduit; and
  • a suction gas heat exchanger that is operatively connected to the gas conduit and the liquid conduit.


[0008] It is noted that the terms 'downstream' and 'upstream' mentioned in this application are merely used to describe the relative positioning of the various components of the heat pump to each other and should not be considered to be an absolute positioning. It is noted that any other component may also be used as a reference point for describing the relatively positioning of the various components to each other. The abovementioned gas conduit is also described in this application as 'suction gas conduit', which terms are interchangeably used.

[0009] The suction gas heat exchanger is configured to transfer heat from the flow medium in the liquid conduit to the flow medium in the gas conduit to increase the temperature of the gas exiting the evaporator. An advantage of the heat pump according to the invention is that the efficiency of the heat pump is increased. The heat transfer achieved in the suction gas heat exchanger is preferably used to overheat the flow medium in the gas conduit prior to entry into the compressor. Heat that would otherwise be lost during expansion in the expander is now recovered and provided to the compressor, resulting in a more efficient heat pump.

[0010] Another advantage is that the temperature of the medium flowing into the compressor can be more accurately be regulated by means of the amount of heat that is transferred into the flow medium prior to entry into the compressor. It is preferred that the temperature of the flow medium entering the compressor is as high as possible without damaging the compressor, such that the amount of extractable heat in the condenser is maximized.

[0011] The heat pump is operable in three different states. In a first or heating state, the heat pump is configured to supply heat to a building or room. In the first state, the evaporator extracts heat from a heat source and subsequently transfer the heat via the condenser to a building or room heating system.

[0012] In a second or cooling state, the evaporator is configured to extract heat from a source that is connected to a cooling system of a room or building. In the second state, the evaporator extracts heat from the source, which source is subsequently used to provide cold to the building or room. The extracted heat may, by means of the condenser, be released to the environment or to a heat sink (that may later be operatively connected to the evaporator to be used as heat source).

[0013] In a third or mixed state, the heat pump is used for both heating and cooling at the same time. In the third state, the evaporator extracts heat from a heat source to cooled the heat source down. The cooled source is subsequently used to provide cold to the building or room. The extracted heat is, by means of the condenser, provided to a building or room to be heated. Therewith the heat pump is capable of simultaneously providing both heat and cold in a highly efficient manner.

[0014] In an embodiment of the heat pump according to the invention, the gas conduit is a low pressure gas conduit. The flow medium exiting the evaporator in general will be a low pressure gas without any liquid present therein. The low pressure gas will then be compressed to high pressure gas in the compressor, to which the low pressure gas conduit is connected.

[0015] In an embodiment of the heat pump according to the invention, the heat pump further comprises a second gas conduit, preferably a high pressure conduit, that extends between the condenser and the compressor.

[0016] The second gas conduit is, in this application, also referred to as discharge gas conduit. The flow medium exiting the compressor is a high pressure gas that is provided to the condenser in order to extract the heat from the flow medium to provide it to a heating system, such as a heating system of a building or room.

[0017] In an embodiment of the heat pump according to the invention, the heat pump further comprises a second liquid conduit, preferably a conduit configured for transporting a gas-liquid mixture, wherein the second liquid conduit extends between the at least one expander and the evaporator.

[0018] The flow medium will, after expansion in the expander, mainly consist of a low pressure gas-liquid mixture that, via the second liquid conduit, is provided to the evaporator.

[0019] In an embodiment of the suction gas heat pump according to the invention, the suction gas heat pump may further comprise a suction gas heat exchanger control unit, such as a control valve, that is operatively connected to the suction gas heat exchanger and that is configured to control the suction gas heat exchanger such that the gas temperature of the gas exiting the suction gas heat exchanger is below 60 °C, preferably below 55 °C, more preferably below 50 °C and most preferably below or at around 45 °C.

[0020] An advantage of the abovementioned embodiment is that, due to the control valve, an even more accurate control over the suction gas heat exchanger is achieved. This allows an optimal recovery of heat from the flow medium in the liquid conduit, while simultaneously preventing compressor damage due to overheating. Compressor overheating is the situation in which the electromotor of the compressor can not be sufficiently cooled, leading to damage. It is therefore preferred that the flow medium temperature in the gas conduit is kept below the abovementioned temperatures to prevent such damage, while simultaneously recovering as much heat as possible from the liquid conduit. In particular, the discharge temperature of the flow medium in the gas conduit is controlled to prevent the oil in the compressor from overheating.

[0021] In an embodiment of the heat pump according to the invention, the heat pump may further comprise a vapour-quantity measuring unit that is configured to, in use of the heat pump, measure a vapour quantity of a flow medium in or directly downstream of the evaporator.

[0022] An advantage of providing a vapour-quantity measuring unit is that the need to overheat the flow of gas from the evaporator to prevent residual liquid from exiting the evaporator is obviated. In the known heat pumps, the flow of gas to the evaporator is overheated using a overheat control unit in order to prevent liquid from exiting the evaporator.

[0023] As a resulting advantage, the temperature of the gas exiting the evaporator can be increased. An other advantage is that the required electricity for evaporation is reduced. This increases the efficiency of the heat pump with up to 10%, or even up to 15%. Preferably, data provided by the vapour quantity measuring unit can be used by a control unit to control the expander, which preferably is an expansion valve, to control the liquid fraction being provided to the evaporator. This allows the evaporating pressure and temperature (in the evaporator) to be controlled, and as a result, no residual liquid will remain at the exit of the evaporator.

[0024] In an embodiment according to the invention, the vapour quantity measuring unit is a vapour quantity sensor that preferably is operatively connected to or part of the evaporator.

[0025] An advantage of the abovementioned embodiment is that a vapour quantity sensor has a limited size and can easily be applied in an evaporator. Another advantage is that the sensor can be used to directly control the evaporator, thus providing a highly accurate control over the evaporator and the flow of medium therein.

[0026] In an embodiment of the heat pump according to the invention, the heat pump may comprise a control unit that is configured to:
  • determine or, alternatively receive an evaporation temperature of the flow medium;
  • receive temperature data including a temperature of the flow medium in the evaporator;
  • controlling a flow of flow medium in the expander, wherein the controlling comprises one or more of:

    ~ increasing the flow of flow medium in the expander if the temperature of the flow medium included in the temperature data increases above a set point temperature; and

    ~ decreasing the flow of flow medium in the expander if the measured temperature included in the temperature data decreases to below the set point temperature; and wherein the set point temperature is a temperature of the flow medium that is 3 Kelvin above the evaporation temperature, and preferably is about 1 Kelvin above the evaporation temperature of the flow medium.



[0027] An advantage of the abovementioned embodiment is that an increased flow of the flow medium through the evaporator and, subsequently, the compressor can be achieved, while simultaneously maintaining a completely gaseous flow from the evaporator to the compressor. This is mainly due to the fact that an increase in temperature above the setpoint increases the amount of superheat of the flow medium, which in turn reduces the efficiency. By controlling, in this case reducing, the amount of superheat, the efficiency of the heat pump is increased. The efficiency increase may be 5% to 10% or even higher. It is noted that superheat or superheating is defined as the temperature difference of the flow medium leaving or exiting the evaporator relative to the evaporation temperature of the flow medium.

[0028] In a preferred embodiment, the control unit comprises a processor and/or a software program that is configured to:
  • receive the temperature data including the measured temperature;
  • based on the temperature data, calculate, using the processor and/or the software program, a flow to be provided to the evaporator to maintain the set point temperature and/or to adjust the temperature to the set point temperature; and
  • control the expander to adjust the flow through the expander to match the calculated flow.


[0029] An advantage is that the superheat of the flow medium in the evaporator may be controlled by increasing and/or decreasing the flow in the expander. This will determine the (amount of) superheating that will occur in the evaporator. The processor and/or software progam of the control unit are configured to provide a stable flow (control) within the expander without overflowing the evaporator and without increasing the (amount of) superheat in the evaporator.

[0030] In an embodiment of the heat pump according to the invention, the heat pump may comprise a natural flow medium, wherein the natural flow medium preferably is R600a isobutane, R-290 propane , R600 butane or R601a isopentane.

[0031] An advantage of a natural flow medium is that it significantly reduces the environmental impact of the heat pump. This is especially true during disposal after the life-time of the heat pump, or in case flow medium is released to the atmosphere during leakage.

[0032] Moreover, a specific advantage of R600 isobutane or similar natural flow media is that these can advantageously be used for high temperature heating systems. R600 isobutane can be used for systems requiring temperatures of up to 85 °C at high heating efficiency.

[0033] A specific advantage of R-290 propane is that it has a low evaporation temperature, in particular of around -40 0C, and additionally allow a condensation temperature of up to 750C. As a result, this particular flow medium is highly suitable for heat sources that have a temperature of 0 °C or even lower. R600 isobutane and R601a isopentane may be used in systems that have temperatures of up to 120 °C (R600 butane) or even above 120 °C (R601a isopentane).

[0034] In an embodiment of the heat pump according to the invention, the heat pump may further comprise an intercooler that is positioned between the condenser and the expander, and preferably positioned between the suction gas heat exchanger and the expander.

[0035] An advantage of the intercooler is that it increases the efficiency of the heat pump even further by using residual heat from the liquid flow medium in the liquid conduit. This is achieved by extracting additional heat from the liquid and subcooling the liquid (even further).

[0036] In a first option, the intercooler is configured to preheat the flow medium to the evaporator, which increases the efficiency of the heat pump.

[0037] In a second option, the intercooler is configured to provide heat to a (recirculation) flow of fluid from an external heating system, preferably a low grade space heating system. The external heating system may for example be part of the system to which the heat pump is configured to supply heat.

[0038] In an embodiment of the heat pump according to the invention, a conduit extending between the suction gas heat exchanger and the compressor comprises a riser section that is configured to supply lubrication oil present in the flow medium to the compressor, wherein the riser section preferably comprises a double riser section comprising a gooseneck.

[0039] An advantage of the abovementioned embodiment is that the oil present in the conduit circuit in the heat pump, by means of the riser section, flows back into the compressor for lubrication. In particular, the riser section increases the flow velocity of the flow medium, which in turn prevents a back flow of oil towards the suction gas heat exchanger and the evaporator.

[0040] It is noted that a gooseneck, which is also referred to as gooseneck duct, swan neck or swan neck duct, is a construction that is capable of obviating, or at least reducing, backflow of a fluid through the curved section of the gooseneck. In the present case, compressor oil that may be present in the flow medium (also referred to as cooling medium, working medium or cooling liquid), is carried along towards the compressor in which it provides lubrication. The compressor oil will not be able to flow back towards the suction gas heat exchanger and the evaporator due to the fact that it will, at that time, be collected in the lower end of the gooseneck. In other words, the lubrication oil is collected in the gooseneck and, from thereon, is carried along with the flow of flow medium towards the compressor (in which it provides lubrication).

[0041] In an embodiment of the heat pump according to the invention, the compressor comprises cooling means that are operatively connected to the cylinder head, wherein the cooling means are configured to simultaneously provide cooling of the compressor and deliver heat to an external source.

[0042] An advantage of the abovementioned embodiment is that the compressor can be regulated to be at an optimal operational temperature, while simultaneously extracting heat that can be used to increase the efficiency of the heat pump. This can be performed by providing the extracted heat to an external source, for example the heating system of a building, or the extracted heat may be (re)used within the heat pump to increase the efficiency thereof.

[0043] In an embodiment of the heat pump according to the invention, the heat pump may further comprise an oil separator that is operatively coupled to the condenser and that is configured to extract oil from the flow medium, wherein the oil preferably is lubrication oil.

[0044] An advantage of providing an oil separator downstream of the compressor is that it reduces the amount of oil that is introduced in the flow circuit of the heat pump and therewith increases the efficiency of the heat pump. This is due to the fact that oil present in the flow medium reduces the efficiency of the condenser, the suction gas heat exchanger and the evaporator, which in turn reduces the heat transfer efficiency of the heat pump. This is substantially obviated by the use of an oil separator.

[0045] Another advantage is that the separated oil can be reused for lubrication of the compressor, which reduces the amount of lubrication oil that is required to lubricate the compressor. This in turn reduces operational and maintenance costs.

[0046] In an embodiment of the heat pump according to the invention, the heat pump may further comprise an oil separator control system that is configured to recirculate the oil from the oil separator and selectively provide the oil to the compressor.

[0047] An advantage of recirculating oil form the oil separator is that the amount of lubrication oil required to lubricate the compressor is significantly reduced. This in turn reduces operational and maintenance costs. In addition, the recirculation of the separated oil also reduces the environmental impact due to the reduced need for oil for the compressor.

[0048] In an embodiment of the heat pump according to the invention, the compressor may be a piston compressor.

[0049] An advantage of a piston compressor is that it provides a high compression ratio, which allows high condensation temperatures and pressures. This increases the working range of the compressor and, therewith, of the heat pump. It allows the heat pump to function over a large temperature range compared to heat pumps with another type of compressor.

[0050] In an embodiment of the heat pump according to the invention, the compressor may comprise a frequency control unit.

[0051] An advantage of providing a frequency control unit is that an optimal efficiency of the compressor is achieved over a large range of heat demand by regulating the speed of the compressor. In other words, regardless of the heat demand, the compressor will function at optimal heating or cooling capacity. In particular in partial load of the heat pump, the efficiency of the heat transfer is increased compared to non-frequency controlled compressors.

[0052] In an embodiment of the heat pump according to the invention, the frequency control unit is configured to operate in a frequency range of 10 to 90 HZ, preferably in the range of 20 to 80 Hz and more preferably in the range of 30 to 70 Hz to control the speed of revolutions of the compressor.

[0053] It has been found that the abovementioned range increases the efficiency of the heat pump in particular in partial load thereof.

[0054] In an embodiment of the heat pump according to the invention, the heat pump comprises two, three of four compressors.

[0055] An advantage of providing multiple compressors, especially multiple frequency controlled compressors, is that a partial load range of the heat pump in the range of 25% to 100% is achieved. In addition, the use of multiple compressors allows the efficiency of the heat pump to be at an optimal value over substantially the entire load range.

[0056] In an embodiment of the heat pump according to the invention, the heat pump comprises multiple expanders, wherein the number of expanders preferably is equal to the number of compressors.

[0057] An advantage of multiple expanders is that the high pressure liquid from the condenser can efficiently be turned into a low pressure gas-liquid mixture. A further advantage is that, especially when each expander is associated with a single one or a few of the multiple compressors, the expander-compressor combinations may form a single flow circuit.

[0058] In an embodiment of the heat pump according to the invention, the heat pump comprises multiple compressors and expanders, wherein each expander is associated with two compressors and together form a single flow circuit, and preferably wherein the heat pump comprises multiple flow circuits.

[0059] An advantage of two compressors associated with a single expander in a flow circuit is that the flexibility of the heat pump with respect to the operational range is increased. This allows an optimal heating or cooling capacity of the heat pump at variable and/or partial loads, while simultaneously reducing the energy use by the heat pump. Another advantage is that an increased reliability of the heat pump is achieved. A further advantage is that an increased performance of the heat pump is achieved.

[0060] In an embodiment of the heat pump according to the invention, the heat pump comprises multiple compressors and expanders, wherein each compressor has an expander associated thereto, and wherein the compressor-expander pairs are positioned in parallel flow circuits to each other.

[0061] An advantage of providing multiple compressor-expander pairs is that multiple flow circuits can be formed, which increases flexibility of the heat pump with respect to the operational range of the heat pump. It is preferred that all compressor-expander pairs share a single condenser and evaporator, because it provides the abovementioned advantages, while simultaneously reducing the size of the heat pump.

[0062] In an embodiment of the heat pump according to the invention, the heat pump comprises a closed-loop conduit circuit that is configured for circulating a flow medium.

[0063] An advantage of a closed-loop conduit circuit is that the flow medium is contained (and confined) in a limited space. This is in particular relevant if natural flow media, such as R600 isobutane or R290 propane, are used since these are flammable.

[0064] Another advantage is that, due to the confinement of the flow media in the closed-loop conduit circuit, only a limited amount of flow medium is required. Another advantage is that the flow medium can be used over substantially the entire life-time of the heat pump without the need to provide additional flow medium.

[0065] In an embodiment of the heat pump according to the invention, the heat pump may further comprise a leak detection unit that is configured to detect flow medium loss from the closed-loop conduit circuit.

[0066] An advantage of a leak detection unit is that, in case a leak is detected, the heat pump may be shut down to prevent damage to the heat pump. Another advantage is that leakage of potentially damaging or hazardous flow media can be detected, which reduces the risk to the environment, people and/or surrounding buildings.

[0067] In an embodiment of the heat pump according to the invention, the heat pump may additionally comprise one or more leak detection sensors that are operatively coupled to the leak detection unit and/or a control unit, wherein the sensors are configured to provide measuring data to the leak detection unit and/or control unit.

[0068] An advantage of providing at least one sensor is that the measuring data can be used to rapidly and efficiently detect leakage of flow medium from the closed-loop conduit circuit. This may for example be performed by detecting (traces of) flow medium outside the closed-loop conduit system or a pressure loss in the closed-loop conduit system. Other detection options are however also possible.

[0069] In an embodiment of the heat pump according to the invention, the heat pump further comprises an alarm unit that is operatively coupled to the leak detection unit and that is configured to be activated based upon an activation signal provided by the leak detection unit and/or a control unit.

[0070] An advantage of an alarm unit, in combination with a leak detection, is that it becomes immediately evident that a leak is present. The alarm unit preferably comprises an audible alarm, a visual alarm or a combination thereof. This alerts nearby persons, which will than be able to vacate the vicinity of the heat pump and/or take appropriate action to reduce or obviate the leak. This increases the operational safety of the heat pump.

[0071] In an embodiment of the heat pump according to the invention, the heat pump further comprises housing comprising a ventilation system, wherein the ventilation system preferably is configured to vent gases from the housing to an outside environment.

[0072] An advantage of the abovementioned embodiment is that, in case of emergency such as a leakage of flow medium, the flow medium can be vented into the environment to prevent built-up of flow medium in the space or room in which the heat pump is positioned. This is especially relevant if a hazardous and/or flammable flow medium is used.

[0073] In an embodiment of the heat pump according to the invention, the heat pump further comprises a housing, preferably a housing complying with ATEX-regulation, that is

[0074] An advantage of providing a housing, especially an ATEX-housing, is that, in case of emergency, any gases leaking from the heat pump are contained within the housing. This allows the gases to be discharged, for example by a ventilation unit, to another, safe, location.

[0075] Another advantage of the housing is that it reduces sound, therewith reducing the noise emitted towards a surrounding of the heat pump.

[0076] The invention also relates to a heating and/or cooling system comprising:
  • at least one heat pump according to the invention;
  • a heat and/or cold distribution system that is operatively coupled to the condenser; and
  • a heat exchange circuit configured to exchange heat with the evaporator.


[0077] The system according to the invention has similar effects and advantages as the heat pump according to the invention. The embodiments as described for the heat pump can, alone or in combination, also be applied in the system according to the invention.

[0078] The invention further relates to a method for heating and/or cooling, the method comprising the steps of:
  • providing a heat pump according to the invention;
  • circulating a flow medium through the heat pump, in particular through the conduits and components thereof;
  • accumulating heat in the flow medium in one of the evaporator or the condenser; and
  • extracting the heat from the flow medium in the other of the evaporator or the condenser.


[0079] The method according to the invention has similar effects and advantages as the heat pump and/or the system according to the invention. The embodiments as described for the heat pump and/or the system can, alone or in combination, also be applied in the method according to the invention.

[0080] In an embodiment of the method according to the invention, the method may further comprise the step of transferring heat between the flow medium in the liquid conduit and the gas conduit to increase the efficiency of the heat pump.

[0081] An advantage of the abovementioned embodiment is that the heat can be transferred from the flow medium in the liquid conduit to the flow medium in the gas conduit to increase the temperature of the (suction) gas exiting the evaporator, in particular the suction gas heat exchanger. This increases the efficiency of the heat pump by recovering heat that would otherwise be lost during expansion in the expander by recovering heat from the liquid flow medium. As a result, the efficiency of the heat pump is increased.

[0082] In an embodiment of the method according to the invention, the method may further comprise the steps of:
  • providing an intercooler that is positioned in the liquid conduit between the condenser and the expander; and
  • transferring heat between the flow medium and an external heating system, such as a building heating system; or
  • exchanging heat with the flow medium of a heat source prior to the flow medium of the heat source entering the evaporator.


[0083] An advantage of the abovementioned embodiment is that heat from the flow medium in the liquid conduit can be extracted and transferred to the flow medium prior to entering the evaporator. Alternatively, it can be used to preheat the flow medium in an external heating system, such as the water in a building heating system. This increases the efficiency of the heat pump.

[0084] In an embodiment of the method according to the invention, the method may further comprise the steps of:
  • providing a vapour-quantity that is operatively connected directly downstream of the evaporator or is positioned in the evaporator; and
  • measuring a vapour quantity of the flow medium directly downstream of the evaporator to collect vapour quantity data.


[0085] An advantage of measuring the vapour quantity in the gas exiting the evaporator is that the need to overheat the flow of gas from the evaporator is obviated. In the known heat pumps, the flow of gas to the evaporator is overheated using a overheat control unit in order to ascertain that all liquid is evaporated in the evaporator. By measuring the vapour quantity, the evaporator can be controlled such that the output is completely gaseous (i.e. does not include liquid). Therewith, the need for overheating the flow medium entering the evaporator is obviated. As a result, the efficiency of the heat pump can be increased by up to 15%.

[0086] In an embodiment of the method according to the invention, the heat pump may comprise a control unit and the method may further comprise the steps of:
  • providing the vapour quantity data to the control unit; and
  • controlling the evaporator such that the flow medium is in a fully gaseous state upon exiting the evaporator.


[0087] An advantage of providing a control unit is that this can be used to even more accurately control the evaporator. The control unit may use the measured vapour quantity data to regulate the amount of heat transferred to the flow medium (and therewith the temperature and state of the flow medium). This is preferably performed by regulating the flow of flow medium towards (and through) the evaporator, yet alternatively may also be performed by increasing or decreasing the heat transfer from the heat source (such as by increasing or decreasing the flow of the substance used to heat the flow medium in the evaporator).

[0088] In an embodiment of the method according to the invention, the heat pump may comprise a control unit and the method may comprise the steps of:
  • providing, preferably to the control unit, temperature data including a measured temperature of the flow medium in the evaporator;
  • determining or, alternatively receiving , an evaporation temperature of the flow medium by the control unit;
  • controlling a flow of flow medium in the expander, wherein the controlling comprises one or more of:

    ~ increasing the flow of flow medium in the expander if the measured temperature of the flow medium included in the temperature data increases above a set point temperature; and

    ~ decreasing the flow of flow medium in the expander if the measured temperature of the flow medium included in the temperature data decreases to below the set point temperature;

wherein the set point temperature is a temperature of the flow medium that is 3 Kelvin above the evaporation temperature, and preferably is about 1 Kelvin above the evaporation temperature of the flow medium.

[0089] In the method according to the invention, the method thus comprises several steps performed by the control unit to reduce the amount of superheat/superheating of the flow medium in the evaporator. It is noted that superheat or superheating is defined as the temperature difference of the flow medium leaving or exiting evaporator relative to the evaporation temperature of the flow medium.An advantage of the abovementioned embodiment is that an increased flow of the flow medium through the evaporator and, subsequently, the compressor can be achieved, while simultaneously maintaining a completely gaseous flow from the evaporator to the compressor. As a result, the efficiency of the heat pump is increased. The efficiency increase may be 5% to 10% or even higher.In a preferred elaboration of the previously mentioned embodiment, the method is a computer-implemented method.

[0090] In a preferred embodiment of the method, the control unit comprises a processor and/or a software program and the method further comprises the steps of:
  • receiving the temperature data including the measured temperature;
  • based on the temperature data, calculating, using the processor and/or the software program, a flow to be provided to the evaporator to maintain the set point temperature and/or to adjust the temperature to the set point temperature; and
  • adjusting the flow through the expander to match the calculated flow.


[0091] An advantage is that the superheat of the flow medium in the evaporator may be controlled by increasing and/or decreasing the flow in the expander. This will determine the (amount of) superheating that will occur in the evaporator. The processor and/or software progam of the control unit are configured to provide a stable flow (control) within the expander without overflowing the evaporator and without increasing the (amount of) superheat in the evaporator.

[0092] It is noted that the heat pump according to the invention may also be provided without the suction gas heat exchanger and, instead, provided with at least one intercooler. In that particular case, the heat pump according to the invention would comprise:
  • an evaporator;
  • at least one compressor that is positioned downstream of the evaporator and is connected thereto by a gas conduit;
  • a condenser that is positioned downstream of the compressor and is operatively connected thereto;
  • at least one expander that is positioned downstream of the condenser and is connected thereto by a liquid conduit; and
  • an intercooler that is positioned in the liquid conduit between the condenser and the expander.


[0093] An advantage of the heat pump according to the invention in which an intercooler is used, is that it increases the efficiency of the heat pump by using residual heat from the liquid flow medium in the liquid conduit. In a first option, the intercooler is configured to preheat a recirculation flow of fluid from an external heating system. The external heating system may for example be part of the system to which the heat pump is configured to supply heat. In a second, alternative option, the intercooler is configured to preheat the flow medium to the evaporator, which increases the efficiency of the heat pump.

[0094] It is noted that the heat pump with an intercooler according to the invention as described above may also be combined with one or more of the embodiments described for the heat pump with a suction gas heat exchanger according to the invention and/or may be applied in the method according to the invention in which the heat pump does not comprise a suction gas heat exchanger.

[0095] It is noted that the heat pump according to the invention may also be provided without the suction gas heat exchanger and, instead, provided with a vapour-quantity measuring unit. In that particular case, the heat pump according to the invention would comprise:
  • an evaporator;
  • at least one compressor that is positioned downstream of the evaporator and is connected thereto by a gas conduit;
  • a condenser that is positioned downstream of the compressor and is operatively connected thereto;
  • at least one expander that is positioned downstream of the condenser and is connected thereto by a liquid conduit; and
  • a vapour-quantity measuring unit that is configured to, in use of the heat pump, measure a vapour quantity of a flow medium in or directly downstream of the evaporator.


[0096] An advantage of the abovementioned heat pump with a vapour-quantity measuring unit is that the need to overheat the flow of gas from the evaporator to prevent residual liquid from exiting the evaporator is obviated. In the known heat pumps, the flow of gas to the evaporator is overheated using a overheat control unit in order to prevent liquid from exiting the evaporator.

[0097] As a resulting advantage, the temperature of the gas exiting the evaporator can be increased. An other advantage is that the required electricity for evaporation is reduced. This increases the efficiency of the heat pump with up to 10%, or even up to 15%.

[0098] It is noted that the heat pump with an vapour-quantity measuring unit according to the invention as described above may also be combined with one or more of the embodiments described for the heat pump with a suction gas heat exchanger according to the invention and/or may be applied in the method according to the invention in which the heat pump does not comprise a suction gas heat exchanger.

[0099] Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

Figure 1 shows a schematic view of a first example of a heat pump according to the invention;

Figure 2 shows a schematic view of a second example of a heat pump according to the invention;

Figure 3 shows a schematic view of an example of a control system according to the invention; and

Figure 4 shows a schematic view of an example of the method according to the invention.



[0100] In an example of heat pump 2 (see figure 1), heat pump 2 comprises conduit circuit 4 that comprises, when viewed in flow direction F, evaporator 4, compressor 6, condenser 8 and expander 10, which in this example is expansion valve 10. Evaporator 4 is coupled to heat source 12, which allows a flow medium to be evaporated in evaporator 4, therewith accumulating heat in the flow medium. Evaporator 4 is connected to gas conduit 14, also mentioned as suction gas conduit 14, which in this example is low pressure gas conduit 14, that extends between evaporator 4 and compressor 6. Gas conduit 14 is provided with double riser section 16 having a gooseneck. Riser section 16 is configured to allow lubrication oil present in the cooling fluid to flow towards the compressor. In this example compressor 6 is connected to condenser 8 by means of gas conduit 18, also mentioned as discharge gas conduit 18, which in this example high pressure gas conduit 18. Gas conduit 18 in this example also contains oil separator 20, which is configured to separate lubrication oil from the flow medium in gas conduit 18 and allow it to flow back into compressor 6 by means of conduit 22. The flow of oil is regulated using optional oil regulator 24 and optional oil storage 26. Compressor 6 is in this example provided with cooling means for cooling the cylinder head or heads (not shown), which means preferably are integrated in compressor 6.

[0101] Condenser 8 is connected to heat system 28 of a building and is configured to transfer the heat from the flow medium to heat system 28 by means of condensation of the flow medium. Condenser 8 is connected to expander 10, which in this example is expansion valve 10, by means of liquid conduit 30. An outlet of expander 10 is connected by means of conduit 32 to evaporator 4. Conduit 32 is configured to transport liquid or a gas-liquid mixture of flow medium.

[0102] Heat pump 2 further comprises heat exchanger 34, which is also mentioned as suction gas heat exchanger, that is operatively connected to gas conduit 14 and to liquid conduit 30. This allows flow medium to flow from gas conduit 14 in flow direction F1 towards heat exchanger 34, while simultaneously allowing flow medium to flow from liquid conduit 30 in flow direction F2 towards heat exchanger 34. Heat exchanger 34 is configured to allow heat transfer from the flow medium in liquid state flowing in direction F2 to the flow medium in gaseous state flowing in direction F1. In this example, the heat transfer in heat exchanger 34 is controlled by means of heat exchanger control unit, in this heat exchanger control valve, 36. In this particular example, heat exchanger control valve 36 is controlled using control unit 37, which is an optional control unit 37.

[0103] Heat pump 2 in this example further comprises intercooler 38, which is operatively connected to liquid conduit 30 on the one hand and to heat source circuit 40 on the other hand. Alternatively, intercooler 38 may be connected to a separate (low temperature) heating system, which are represented by connections A, B.

[0104] Intercooler 38 is configured to extract heat from the flow medium flowing in flow direction F3 and transfer the heat to flow medium flowing in flow direction F4. In the present case, the flow medium flowing in direction F4 is a flow medium of the heat source rather than the flow medium present in heat pump 2 when it is in use.

[0105] Heat pump 2 further also comprises vapour-quantity sensor 33, which in this example is used to (indirectly or directly) regulate the evaporator. In particular, data provided by the vapour quantity sensor 33 is used by control unit 54, 154 to control expansion valve 10 to control the liquid fraction being provided to evaporator 4. This allows the evaporating pressure and temperature (in the evaporator) to be controlled, and as a result, no residual liquid will remain at the exit of evaporator 4. This will increase energy efficiency by 5% to 10% and thus will comply with higher energy standards than existing heat pumps.

[0106] In use of heat pump 2 for heating, heat is extracted from a flow medium of heat source 12 flowing through conduit 40 by means of evaporator 4. The flow medium in heat pump 2 is evaporated in evaporator 4 due to the heat extracted from the flow medium in conduit 40. Subsequently, the flow medium flows in flow direction F into gas conduit 14 towards compressor 6. A part of the gaseous flow medium is rerouted through heat exchanger 34, in which it is heated to a higher temperature before flowing towards compressor 6. The heat in heat exchanger 34 is extracted from the flow medium flowing in flow direction F2 from liquid conduit 30. This allows additional heat to be recovered from the flow in conduit 30. Compressor 6 compresses the gaseous flow medium to a high temperature, high pressure gas that flows through conduit 18 to condenser 8, in which the flow medium is substantially completely condensed to (high pressure) liquid while transferring heat to heat system 28. The liquid flows through conduit 30 to expander 10, in which the liquid is expanded to low pressure liquid flow medium, or to a mixture of liquid and gaseous flow medium (at low pressure), before once more flowing into evaporator 4.

[0107] To further increase the heat recovery, a part of the flow medium from conduit 30 is routed via intercooler 38 and is used to preheat the flow medium in conduit 40, which is subsequently used to evaporate the flow medium in evaporator 4. Alternatively, the extracted heat may be used as low grade heat in a (low temperature) heating system.

[0108] In a cooling mode, heat pump 2 functions in mostly the same way. In this mode however, the medium in conduit 40 is used to cool a building, whereas the heat from condenser 8 may be discharged (at 28).

[0109] In a second example (see figure 2), heat pump 102 comprises conduit circuit 104 that comprises, when viewed in flow direction F, evaporator 104, compressor 106, condenser 108 and expander 110. Heat pump 102 in this example comprises two compressors 106, which both feed into a single condenser 108 and two expanders 110, which both feed into a single evaporator 104. It is noted that, in a not-shown alternative, heat pump 102, and in particular compressors 106a, 106b, may also be two compressors 106a and two compressors 106b.

[0110] Evaporator 104 is coupled to heat source 112, which allows a flow medium to be evaporated in evaporator 104, therewith accumulating heat in the flow medium. Evaporator 104 is connected to gas conduit 114, which in this example is low pressure gas conduit 114, that extends between evaporator 104 and compressor 106. Gas conduit 114 extends through one side of heat exchanger 134 and is further downstream provided with double riser section 116 having a gooseneck. Riser section 116 is configured to allow lubrication oil present in the cooling fluid to flow towards the compressor. Gas conduit 114 further comprises vapour quantity measuring unit 133, which in this case is vapour quantity sensor 133. Vapour-quantity sensor 133 in this example is used to (indirectly or directly) regulate evaporator 104. In particular, data provided by vapour quantity sensor 133 is used by control unit 154 to control expansion valve 110 to control the liquid fraction being provided to (and from) evaporator 104. This allows the evaporating pressure and temperature (in the evaporator) to be controlled, and as a result, no residual liquid will remain at the exit of evaporator 104. This will increase energy efficiency by 5% to 10% and thus will comply with higher energy standards than existing heat pumps.

[0111] In this example each compressor 106 is connected to condenser 108 by means of gas conduit 118, which in this example high pressure gas conduit 118. Each gas conduit 118 in this example also contains oil separator 120, which is configured to separate lubrication oil from the flow medium in gas conduit 118 and allow it to flow back into compressor 106 by means of conduit 122. The flow of oil is regulated using optional oil regulator 124. As already noted above, in this example heat pump 102 comprises two compressors 106. First compressor 106a is connected to first part 108a of condenser 108, in which heat is extracted from the flow medium to increase the temperature of a flow medium in heat system 128 that is connected to condenser 108. In second part 108b of condenser 108, the temperature of the flow medium in heat system 128 is increased even further by transferring heat from the flow medium delivered from second compressor 106b. The use of two separate compressors 106a, 106b increases the flexibility of heat pump 102, especially due to the fact that it increases the load range in which heat pump 102 can efficiently operate. It is noted that each compressor 106a, 106b, may also comprise two compressors (for a total of four compressors 106).

[0112] First part 108a of condenser 108 is connected to first expander 110a, which in this example is expansion valve 110a, by means of liquid conduit 130. An outlet of expander 110a is connected by means of conduit 132 to evaporator 104. Conduit 132 is configured to transport liquid or a gas-liquid mixture of flow medium. Second part 108b of condenser 108 is similarly connected to second expander 110b. As a result, first flow circuit 101a comprises first part 108a of condenser 108, first expander 110a, compressor 106a and first part of evaporator 104a. Second flow circuit 101b comprises second part 108b of condenser 108, second expander 110b, compressor 106b and second part of evaporator 104b.

[0113] In this example, conduit 130 comprises liquid storage 148 and subsequently extends through the other side of heat exchanger 134. This allows heat to be transferred from the flow medium in conduit 132, which is a liquid at that point, to the flow medium in conduit 114, which is a gas at that point. In this example, the heat transfer in heat exchanger 134 is controlled by means of heat exchanger control unit, in this heat exchanger control valve, 136. Heat exchanger control valve 136 can be (partially) closed or completely opened to regulate the flow of medium through heat exchanger 134 to therewith control the heat transfer between the flow media flow in respectively conduits 130 and 114. This will increase suction gas temperature, thus providing an increased energy performance, while simultaneously controlling the flow of liquid through the suction gas heat exchanger to prevent overheating of the electric motor/oil of the compressor.

[0114] Conduit 130 in this example of heat pump 102 further comprises intercooler 138. A first side of intercooler 138 is positioned in liquid conduit 30, whereas the other side is connected to heat source 112 by means of conduits 140, 142 (schematically indicated by connections A, B). In this example, intercooler 138 is used to extract heat from the liquid flow medium in conduit 130 and supply the extracted heat to the flow medium of the heat source prior to entry into the evaporator. Intercooler 138 may in this example be circumvented by means of conduit 144 and valves 146.

[0115] Heat pump 102 in this example also schematically shows housing 150, which may be housing 150 according to ATEX regulation, and fan 152 that is configured to selectively vent the inside of housing 150. The delineation between the inside IN of housing 150 and the outside OUT of housing 150 is provided by the demarcation lines. Heat pump 102 further comprises leak detection sensor 156 that is provided in housing 150.

[0116] In an example (see figure 3), heat pump 2, 102 may comprise control unit 154 which is configured to control one or more aspects of heat pump 102. In this example, control unit 154, which may for example be a computing device and/or a PLC, is configured to control heat exchanger control valve 136, compressor(s) 6, 106, oil regulator 24, 124 and intercooler control valves 146. Optionally, control unit 154 may also control fan 152. Heat pump 102 may also comprise one or more sensors 156 that are configured to measure parameters of heat pump 102, such as a leakage parameter, and alarm unit 158. In this example, in case of leakage of flow medium (i.e. refrigerant), this may be detected by one or more sensors 156, which relay this leakage data to alarm unit 158. Alarm unit 158 in this example comprises an integral control unit (not shown) which is configured to switch on fan 152 to expel the flow medium from housing 150 and is further configured to engage alarm unit 158 to warn persons near heat pump 102 of the leakage. In addition, alarm unit 158 will relay alarm information to control unit 154, which will subsequently shut heat pump 2, 102 off.

[0117] In an example of the method 1000 for generating heat and/or cold according to the invention (see figure 4), method 1000 comprises the steps of providing 1002 a heat pump according to the invention and circulating 1004 a flow medium through the heat pump, in particular through the conduits and components thereof. Method 1000 further comprises accumulating 1006 heat in the flow medium in one of the evaporator or the condenser and extracting 1008 the heat from the flow medium in the other of the evaporator or the condenser.

[0118] In this example, method 1000 further comprises the optional steps of providing 1010 a heat exchanger that is operatively connected to the gas conduit and the liquid conduit, and transferring 1012 heat between the flow medium in the liquid conduit and the gas conduit to increase the efficiency of the heat pump.

[0119] This example further comprises the optional steps of providing 1014 an intercooler that is positioned in the liquid conduit between the condenser and the expander and transferring 1016 heat between the flow medium and an external heating system, such as a building heating system. Alternatively to step 1016, optional step 1014 may be followed by the step of exchanging 1018 heat with the flow medium prior to the flow medium entering the evaporator.

[0120] It is noted that the optional steps 1010, 1012 may be used in combination or alternatively to the optional steps 1014 and 1016 or 1018.

[0121] Further optionally, method 1000 may further comprise the steps of providing 1020 a vapour-quantity sensor that is operatively connected directly downstream of the evaporator or is positioned in the evaporator and measuring 1022 a vapour quantity of the flow medium in or directly downstream of the evaporator to collect vapour quantity data. Method 1000 may optionally comprise, using the control unit of the heat pump, the steps of providing 1024 the vapour quantity data to the control unit and controlling 1026 the evaporator such that the flow medium is in a fully gaseous state upon exiting the evaporator. This increases evaporating temperature and pressure, leading to an increased efficiency and/or energy performance of the heat pump with about 5% to 10%.

[0122] The present invention is by no means limited to the above described preferred embodiments and/or experiments thereof. The rights sought are defined by the following claims within the scope of which many modifications can be envisaged.


Claims

1. Heat pump comprising:

- an evaporator;

- at least one compressor that is positioned downstream of the evaporator and is connected to the evaporator by a gas conduit;

- a condenser that is positioned downstream of the compressor and is operatively connected thereto;

- at least one expander that is positioned downstream of the condenser and is connected thereto by a liquid conduit; and

- a suction gas heat exchanger that is operatively connected to the gas conduit and the liquid conduit.


 
2. Heat pump according to claim 1, further comprising a suction gas heat exchanger control unit that is operatively connected to the suction gas heat exchanger and that is configured to control the suction gas heat exchanger such that the gas temperature of the gas exiting the suction gas heat exchanger is below 60 °C, preferably below 55 °C, more preferably below 50 °C and most preferably below or at around 45 °C.
 
3. Heat pump according to any one of the preceding claims, comprising a natural flow medium, wherein the natural flow medium preferably is R600a isobutane or R-290 propane.
 
4. Heat pump according to any one of the preceding claims, further comprising an intercooler that is positioned between the condenser and the expander.
 
5. Heat pump according to any one of the preceding claims, wherein a conduit extending between the suction gas heat exchanger and the compressor comprises a riser section that is configured to supply lubrication oil present in the flow medium to the compressor, wherein the riser section preferably comprises a double riser section comprising a gooseneck.
 
6. Heat pump according to any one of the preceding claims, wherein the compressor comprises cooling means that are operatively connected to the cylinder head, wherein the cooling means are configured to simultaneously provide cooling of the compressor and deliver heat to an external source.
 
7. Heat pump according to any one of the preceding claims, further comprising a vapour-quantity measuring unit that is configured to, in use of the heat pump, measure a vapour quantity of a flow medium directly downstream of the evaporator.
 
8. Heat pump according to any one of the preceding claims, further comprising an oil separator that is operatively coupled to the condenser and that is configured to extract oil from the flow medium, wherein the oil preferably is lubrication oil, and preferably further comprising an oil separator control system that is configured to recirculate the oil from the oil separator and selectively provide the oil to the compressor.
 
9. Heat pump according to any one of the preceding claims, wherein the compressor:.

- is a piston compressor; and/or

- comprises a frequency control unit


 
10. Heating and/or cooling system comprising:

- at least one heat pump according to any one of the preceding claims;

- a heat and/or cold distribution system that is operatively coupled to the condenser; and

- a heat exchange circuit configured to exchange heat with the evaporator.


 
11. Method for generating heat and/or cold, the method comprising:

- providing a heat pump according to any one of the preceding heat pump claims;

- circulating a flow medium through the heat pump, in particular through the conduits and components thereof;

- accumulating heat in the flow medium in one of the evaporator or the condenser; and

- extracting the heat from the flow medium in the other of the evaporator or the condenser.


 
12. Method according to claim 11, further comprising the steps of:

- providing a suction gas heat exchanger that is operatively connected to the gas conduit and the liquid conduit; and

- transferring heat between the flow medium in the liquid conduit and the gas conduit to increase the efficiency of the heat pump.


 
13. Method according to claim 11 or 12, further comprising the steps of:

- providing an intercooler that is positioned in the liquid conduit between the condenser and the expander;

- transferring heat between the flow medium and an external heating system, such as a building heating system; or

- exchanging heat with the flow medium of a heat source prior to the flow medium of the heat source entering the evaporator.


 
14. Method according to any one of the claims 11 to 13, further comprising the steps of:

- providing a vapour-quantity that is operatively connected directly downstream of the evaporator;

- measuring a vapour quantity of the flow medium directly downstream of the evaporator to collect vapour quantity data.


 
15. Method according to claim 14, wherein the heat pump comprises a control unit and wherein the method further comprises the steps of:

- providing the vapour quantity data to the control unit; and

- controlling the evaporator such that the flow medium is in a fully gaseous state upon exiting the evaporator.


 




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