Heat pump system

Abstract

To provide technique for improving energy consumption efficiency in a heat pump system.SOLUTION: The heat pump system comprises: a generation portion where clathrate hydrate is generated; a decomposition portion where the clathrate hydrate is decomposed and the decomposition product is delivered; a first main flow path where heating medium flows from the generation portion to the decomposition portion; a second main flow path where the heating medium flows from the decomposition portion to the generation portion; a gas-liquid separation portion separating gas in the decomposition product delivered from the decomposition portion, from mixed solvent; and a heat exchange portion where slurry including the clathrate hydrate flowing out from the generation portion and the mixed solvent separated by the gas-liquid separation portion are flown and heat- exchanged.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat pump system. [Background technology]

[0002] Conventionally, heat pumps that combine gas compression / expansion and heat exchange have been used. For example, Patent Document 1 discloses a vehicle air conditioning system that includes an expansion valve that expands condensed refrigerant and is interconnected via a refrigerant line, an evaporator that evaporates the expanded refrigerant through heat exchange with air, and a compressor that compresses the evaporated gaseous refrigerant.

[0003] Although heat pumps are characterized by their ability to efficiently obtain thermal energy using little electrical energy, with the recent rise in awareness of environmental issues, there is a demand for even greater improvements in energy consumption efficiency. To address this, heat pump systems utilizing the decomposition / formation of clathrate hydrates have been proposed (see, for example, Patent Documents 2 and 3 and Non-Patent Document 1). The heat of decomposition / formation of clathrate hydrates is more than 10 times the latent heat of evaporation / condensation of ordinary refrigerants, such as those used in the heat pump described in Patent Document 1, and therefore, improvements in energy consumption efficiency are expected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-076792 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-101140 [Patent Document 3] Japanese Patent Publication No. 2022-087404 [Non-patent literature]

[0005] [Non-Patent Document 1] T. Ogawa et al., Applied Energy, 26, 2157 (2006). Summary of the Invention [Problem to be solved by the invention]

[0006] In the heat pump systems that utilize the decomposition / generation of clathrate hydrates disclosed in Patent Documents 2 and 3 and Non-Patent Document 1, further improvements in energy consumption efficiency are desired.

[0007] The present invention has been made to solve the above-mentioned problems, and has an object to provide a technique for improving energy consumption efficiency in a heat pump system. [Means for solving the problem]

[0008] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0009] (1) According to one aspect of the present invention, there is provided a heat pump system that transports heat by repeating a decomposition process and a generation process of clathrate hydrates using a heat medium. The heat pump system includes a generation section into which a mixed liquid of a mixed solvent of a liquid auxiliary agent and water and a gas is introduced to generate clathrate hydrates, a decomposition section into which the clathrate hydrates are decomposed and a decomposition product, which is a mixed phase of the gas and the mixed solvent, is discharged, a first main flow path through which the heat medium flows from the generation section to the decomposition section, a second main flow path through which the heat medium flows from the decomposition section to the generation section, a heat dissipation section that dissipates heat from the heat medium in the generation section by heat exchange between the heat medium and a heat source outside the heat pump system, a pressure reduction section that decompresses the heat medium in the decomposition section, a heat absorption section that absorbs heat into the heat medium in the decomposition section by heat exchange between the heat medium in the decomposition section and a heat source outside the heat pump system, and a heat transfer section between the decomposition section and the second main flow path. a gas-liquid separation section connected to the first main flow path and configured to separate the gas in the decomposition product discharged from the decomposition section from the mixed solvent; a compression section connected to the gas-liquid separation section via the second main flow path and configured to compress the gas separated by the gas-liquid separation section; a mixing section connected to the compression section and the production section via the second main flow path and connected to the gas-liquid separation section via a first sub-flow path and configured to produce the mixed liquid containing the mixed solvent separated by the gas-liquid separation section and the gas compressed by the compression section; and a heat exchange section connected to the first main flow path and the first sub-flow path and configured to circulate a slurry containing the clathrate hydrate flowing out of the production section and the mixed solvent separated by the gas-liquid separation section, thereby performing heat exchange.

[0010] According to this configuration, since the heat exchanger is provided, sensible heat can be recovered by exchanging sensible heat between the high-temperature slurry discharged from the production section and the low-temperature mixed solvent of water and the auxiliary discharged from the decomposition section. The low-temperature slurry can be supplied to the decomposition section, and the high-temperature mixed liquid can be supplied to the production section, promoting the production of clathrate hydrates in the production section and promoting the decomposition of clathrate hydrates in the decomposition section. In other words, according to this configuration, the temperature difference between the high-temperature side and the low-temperature side during refrigeration cycle operation can be increased, and the energy consumption efficiency (COP) can be improved.

[0011] (2) The heat pump system of the above aspect may further include a gas / solid-liquid separation unit connected to the generation unit via the first main flow path and separating the gas from the slurry generated in the generation unit, and a third sub-flow path for supplying the gas separated by the gas / solid-liquid separation unit to the mixing unit.

[0012] According to this configuration, a gas / solid-liquid separation section is provided between the generation section and the decomposition section, so that gas can be separated / removed from a slurry (mixture) containing clathrate hydrate solids, and the slurry with a reduced gas content can be supplied to the decomposition section. The heat transfer medium (a mixed phase of gas, water, and auxiliary agent) on the outlet side of the decomposition section is at a low temperature and pressure. According to this configuration, the amount of gas supplied to the decomposition section is reduced, so the amount of low-pressure gas supplied to the compression section can be reduced, and a decrease in compressor efficiency can be suppressed. As a result, energy consumption efficiency can be further improved.

[0013] (3) The heat pump system of the above aspect may further include a mixed solvent separation unit connected downstream of the gas / solid-liquid separation unit via the first main flow path and configured to separate the mixed solvent from the slurry that has passed through the gas / solid-liquid separation unit, and a fourth sub-flow path connected to the mixed solvent separation unit and configured to supply the mixed solvent separated by the mixed solvent separation unit to the mixing unit. In this manner, a slurry in which gas and mixed solvent have been reduced can be supplied to the decomposition unit. Because the mixed solvent separated by the mixed solvent separation unit is at a high temperature, a higher-temperature mixed liquid can be supplied to the production unit, and a lower-temperature slurry can be supplied to the decomposition unit. As a result, energy efficiency can be further improved.

[0014] (4) The heat pump system of the above aspect may further include a transport pump disposed in the first main flow path and transporting the heat medium. In this way, the flow rate can be adjusted by the transport pump, and therefore the decomposition rate in the decomposition section can be adjusted.

[0015] (5) The heat pump system of the above aspect may further include a dehydration unit disposed between the gas-liquid separation unit and the compression unit, and configured to adsorb the mixed solvent in the gas separated by the gas-liquid separation unit. This allows the mixed solvent mixed in the gas separated by the gas-liquid separation unit to be removed. This reduces energy consumption by the compression unit, thereby further improving the energy consumption efficiency of the heat pump system.

[0016] The present invention can be realized in various forms, for example, in the form of a heat utilization device having a heat pump system, a control method for a heat pump system, a method for generating cold heat, a method for generating hot heat, etc. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is an explanatory diagram schematically illustrating a basic configuration of a heat pump system according to a first embodiment. [Figure 2]FIG. 2 is an explanatory diagram schematically illustrating a normal mode in the heat pump system. [Figure 3] FIG. 2 is an explanatory diagram schematically illustrating a sensible heat exchange mode in a heat pump system. [Figure 4] 10 is a flowchart showing an example of a flow of mode switching control in a control unit. [Figure 5] FIG. 10 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system according to a second embodiment. [Figure 6] FIG. 10 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system according to a third embodiment. [Figure 7] FIG. 10 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system according to a fourth embodiment. [Figure 8] FIG. 10 is a diagram showing the proportion of sensible heat in the total heat amount. [Figure 9] FIG. 1 is a diagram showing an improvement in COP due to sensible heat recovery. [Figure 10] FIG. 2 is a diagram showing specifications of a heat exchanger. [Figure 11] FIG. 1 shows the physical properties of gas, water, and clathrate hydrate solids. [Figure 12] FIG. 3 is a diagram showing a temperature change of a heat medium in the heat pump system of the first embodiment. [Figure 13] FIG. 10 is a diagram showing a temperature change of a heat medium in a heat pump system according to a second embodiment. [Figure 14] FIG. 10 is a diagram showing a temperature change of a heat medium in a heat pump system according to a third embodiment. [Figure 15] FIG. 1 is a diagram showing the relationship between the power COP and the gas-solid-liquid ratio. [Figure 16] FIG. 10 is a diagram showing the results of calculations of the amount of cold generated in a heat pump system. [Figure 17] These are the input conditions for 1D-SIM. [Figure 18] FIG. 1 is a diagram showing a 1D-SIM model of a generation unit. [Figure 19] FIG. 1 is an explanatory diagram showing an example of a 1D-SIM model and a simulation result. DETAILED DESCRIPTION OF THE INVENTION

[0018] First Embodiment FIG. 1 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system 100 according to a first embodiment. The heat pump system 100 transports heat by using a heat medium to repeatedly undergo decomposition and formation processes of clathrate hydrates. Clathrate hydrates are ice-like compounds (clathrate compounds) in which gas molecules are enclosed in cages formed by hydrogen bonds between water molecules. Heat is generated during the formation process in which clathrate hydrates are formed from water and gas, and heat is absorbed during the decomposition process in which the clathrate hydrates are separated into water and gas. The heat pump system 100 according to this embodiment transports heat by utilizing the latent heat (heat of decomposition and formation) of clathrate hydrates.

[0019] The heat pump system 100 comprises a production section 10 into which a mixture of a gas and a mixed solvent of water and an auxiliary agent is introduced and clathrate hydrates are produced, a decomposition section 20 into which the clathrate hydrates are decomposed and a decomposition product, which is a mixed phase of gas and the mixed solvent, is discharged, a first main flow path 30 through which a heat transfer medium flows from the production section 10 to the decomposition section 20, and a second main flow path 40 through which the heat transfer medium flows from the decomposition section 20 to the production section 10. Fig. 1 shows the phase changes of the heat transfer medium flowing through the first main flow path 30 and the second main flow path 40, with the clathrate hydrate slurry indicated by a dashed line, the decomposition product (gas / mixed solvent mixed phase) indicated by a dashed line, the mixed liquid obtained by mixing gas and the mixed solvent indicated by a double line, the gas phase indicated by a dashed-dotted line, and the aqueous phase (mixed solvent) indicated by a solid line. From the production section 10, a clathrate hydrate (clathrate hydrate slurry) is output in the form of a gas-solid-liquid mixture containing a clathrate hydrate solid, unreacted gas, and a mixed solvent (water / adjuvant). The clathrate hydrate slurry is also simply called "slurry."

[0020] Gases that can be used to produce clathrate hydrates include hydrocarbon gases such as methane, ethane, propane, ethylene, and acetylene; fluorocarbon gases such as HFCs (hydrofluorocarbons) and HCFCs (hydrochlorofluorocarbons); rare gases such as argon and krypton; carbon dioxide (CO2), nitrogen, air, ammonia, and xenon (Xe). Gases with properties such as a high maximum equilibrium temperature, a low equilibrium pressure, and a small change in pressure relative to temperature are preferred because they can achieve a high COP. These gases may be used alone or in combination to achieve desired properties. Combining different gases allows for the adjustment of the phase change conditions of clathrate hydrates.

[0021] As described above, in the heat pump system 100 of this embodiment, a mixture of a mixed solvent of water and an auxiliary agent and a gas is supplied to the generator 10. The auxiliary agent is added to the water to adjust the phase change conditions of the clathrate hydrate. The auxiliary agent is not particularly limited, but is preferably one with a molecular size (5.8 to 8.6 Å) that can form a clathrate hydrate. Examples of such auxiliary agents that can be used include organic solvents such as cyclohexane and cyclopentane, and water-soluble ammonium salts such as tetrabutylammonium fluoride and tetrapentylammonium chloride.

[0022] As shown in the figure, the heat pump system 100 includes a heat dissipation section 12 that causes the heat medium to dissipate heat by heat exchange between the heat medium in the generation section 10 and a heat source outside the heat pump system 100, and a heat absorption section 22 that causes the heat medium to absorb heat by heat exchange between the heat medium in the decomposition section 20 and a heat source outside the heat pump system. Heat exchangers are used as the heat dissipation section 12 and the heat absorption section 22.

[0023] The heat pump system 100 includes, in the first main flow path 30, a pressure reduction section 24 that reduces the pressure of the heat medium in the decomposition section 20. The heat pump system 100 also includes, in the second main flow path 40, a first gas-liquid separation section 14 that separates the decomposition product, which is a mixed phase of gas and water (mixed solvent) delivered from the decomposition section 20, into gas and liquid, a compression section 16 that compresses the gas separated by the first gas-liquid separation section 14, and a mixer 18 that is connected to the first gas-liquid separation section 14 via a first sub-flow path 43 and mixes the water (mixed solvent) separated by the first gas-liquid separation section 14 with the gas compressed by the compression section 16 to produce a mixed liquid. Note that the first gas-liquid separation section 14 in this embodiment will also be simply referred to as the "gas-liquid separation section."

[0024] The heat pump system 100 also includes a heat exchanger 70 that is connected to the first main flow path 30 and the first sub-flow path 43 and performs heat exchange by circulating the clathrate hydrate slurry flowing out of the production unit 10 and the mixed solvent separated by the first gas-liquid separation unit 14. The heat exchanger 70 is disconnectably connected to the first main flow path 30 via a second sub-flow path 71. The heat exchanger 70 is also provided in the first sub-flow path 43. The first sub-flow path 43 includes a bypass flow path 43d that avoids the heat exchanger 70, so that the mixed solvent separated by the first gas-liquid separation unit 14 can flow into the mixing unit 18 without passing through the heat exchanger 70.

[0025] The heat pump system 100 also includes a second gas-liquid separation section 56 in the second main flow path 40 between the compression section 16 and the mixing section 18, and returns the compressor oil separated in the second gas-liquid separation section 56 to the compression section 16 via a fifth sub-flow path 80.

[0026] The second main flow path 40 includes a first flow path 41 connecting the decomposition section 20 and the first gas-liquid separation section 14, a second flow path 42 connecting the first gas-liquid separation section 14 and the compression section 16, an eighth flow path 48 connecting the compression section 16 and the second gas-liquid separation section 56, a fourth flow path 44 connecting the second gas-liquid separation section 56 and the mixing section 18, and a fifth flow path 45 connecting the mixing section 18 and the generation section 10.

[0027] As described above, the first gas-liquid separation unit 14 is connected to the mixing unit 18 via the first sub-channel 43. The first sub-channel 43 includes a tenth channel 43a connecting the first gas-liquid separation unit 14 and the heat exchange unit 70, and an eleventh channel 43b connecting the heat exchange unit 70 and the mixing unit 18. The tenth channel 43a is provided with a liquid feed pump 15 that sends the mixed solvent separated in the first gas-liquid separation unit 14 to the heat exchange unit 70. The eleventh channel 43b is provided with a liquid feed pump 58 that sends the mixed solvent that has passed through the heat exchange unit 70 to the mixing unit 18. A liquid feed pump with a higher pressure than the liquid feed pump 15 is used as the liquid feed pump 58. The first sub-channel 43 is provided with on-off valves 75, 76, and 77 that are opened and closed according to predetermined conditions, as described below. The heat exchange unit 70 is also disconnectably connected to the first main channel 30 via a second sub-channel 71. As shown in the figure, an on-off valve 74 is provided in the first main flow path 30, and on-off valves 72 and 73 are provided in the second sub-flow path 71, which are opened and closed according to predetermined conditions as will be described later.

[0028] An expansion valve, a capillary tube, or the like can be used as the pressure reducing section 24. Various types of gas-liquid separators can be used as the first gas-liquid separation section 14, such as a surface tension type, cyclone type, filter type, centrifugal force type, cooling type, multi-stage filter type, or cyclone type. In the case of a surface tension type gas-liquid separator, it is expected that after separation, the gas phase side will be 100% refrigerant gas, and the liquid phase side will be 30 / 70% refrigerant gas / mixed solvent (volume ratio). In this embodiment, an electric compressor is used as the compression section 16.

[0029] The heat exchanger 70 performs heat exchange by circulating the clathrate hydrate slurry flowing out of the production unit 10 and the mixed solvent separated by the first gas-liquid separation unit 14. The clathrate hydrate slurry cooled by the heat exchanger 70 is supplied to the decomposition unit 20 via the first main flow path 30, and the mixed solvent heated by the heat exchanger 70 is supplied to the decomposition unit 20 via the eleventh flow path 43b. Various types of heat exchangers can be used as the heat exchanger 70, such as a plate-type countercurrent type or a cross-flow type.

[0030] The mixing section 18 actively mixes water (mixed solvent) with the high-pressure gas. The type of the mixing section 18 that can be used includes internal mixing, external mixing, and collision types. The mixed solvent and the high-pressure gas can be mixed, for example, by stirring the gas and mixed solvent, or by supplying the gas into the mixed solvent through a filter. Mixing the mixed solvent and the gas in the mixing section 18 results in finer gas bubbles in the mixed solvent. The size of the bubbles is not particularly limited, but is preferably micro- to nano-sized. Reducing the bubble size increases the contact area between the gas and water, improving the efficiency of clathrate hydrate production. Nano-sized bubbles improve the efficiency of clathrate hydrate production, but require more energy. Therefore, it is preferable to set the bubble size in consideration of the balance with energy consumption.

[0031] The heat transfer medium delivered from the decomposition section 20 is a mixed phase containing gas resulting from the decomposition of clathrate hydrates, water, and an auxiliary agent. Although the heat transfer medium flowing through the first flow path 41 is a mixed phase containing gas, water, and an auxiliary agent, it is not actively mixed, and the gas is not mixed as uniformly in the mixed solvent as in the heat transfer medium flowing through the fifth flow path 45. In this specification, a solution in which high-pressure gas and a mixed solvent are actively mixed is referred to as a "mixed liquid," and a solution containing gas, water, and an auxiliary agent produced by the decomposition of clathrate hydrates in the decomposition section 20 but which is not actively mixed is referred to as a "decomposed product."

[0032] The heat pump system 100 of this embodiment includes a heat exchanger 70, and can control the temperatures of the mixed liquid supplied to the production section and the clathrate hydrate slurry supplied to the decomposition section by controlling the opening and closing of on-off valves 72 to 77. The heat pump system 100 of this embodiment is operated by switching between a normal mode in which the heat exchanger 70 is disconnected and a sensible heat exchange mode in which the heat exchanger 70 is connected (described in detail later).

[0033] FIG. 2 is an explanatory diagram schematically illustrating the normal mode of the heat pump system 100 of this embodiment. FIG. 2 and FIG. 3, which will be described later, show a control unit 90 that controls the entire heat pump system 100, including switching between the normal mode and the sensible heat exchange mode. The control unit 90 is a computer including a ROM, a RAM, and a CPU. Here, the computer includes a PLC (programmable logic controller), a PC (personal computer), or the like. In other embodiments, switching between the normal mode and the sensible heat exchange mode, i.e., opening and closing the on-off valves 72 to 77, may be performed manually by a user. Heat transport in the normal mode of the heat pump system 100 of this embodiment will be described using FIG. 2. In the normal mode, the on-off valves 72, 73, 75, and 76 are closed, and the on-off valves 74 and 77 are open.

[0034] The heat medium at the outlet of the decomposition section 20 in FIG. 2 is in a decomposed state (a mixed phase of gas, water, and auxiliary agent) and is at low temperature and low pressure. The decomposition product as the heat medium flows through the first flow path 41 into the first gas-liquid separation section 14. The decomposition product is decomposed into gas and the mixed solvent in the first gas-liquid separation section 14. The gas flows through the second flow path 42 into the compression section 16, is pressurized by the compression section 16, and flows into the mixing section 18 through the eighth flow path 48, the second gas-liquid separation section 56, and the fourth flow path 44. The gas is pressurized and heated by compression in the compression section 16. Meanwhile, the mixed solvent is forced through the first sub-flow path 43 by the liquid feed pumps 15 and 58 and flows into the mixing section 18. At this time, the first sub-flow path 43 is composed of the tenth flow path 43a, the eleventh flow path 43b, and the bypass flow path 43d, and does not pass through the heat exchange section 70. Therefore, the mixed solvent flowing into mixing section 18 has a temperature similar to that at the outlet of decomposition section 20. In mixing section 18, high-temperature, high-pressure gas and mixed solvent are mixed to generate a high-temperature, high-pressure mixed liquid, which flows into production section 10 through fifth flow path 45. In other words, the heat transfer medium (mixed liquid) on the inlet side of production section 10 is at a high temperature and high pressure.

[0035] The high-temperature, high-pressure mixed liquid (heat medium) that flows into the generation section 10 is cooled by heat dissipation in the heat dissipation section 12. Specifically, the heat exchanger that serves as the heat dissipation section 12 exchanges heat between the heat medium in the generation section 10 and a heat source outside the heat pump system, cooling the heat medium. When heat equivalent to the heat of generation is released from the heat medium, the state of the heat medium crosses the phase equilibrium line of the heat medium and becomes a clathrate hydrate state (high pressure) at the outlet side of the generation section 10. The clathrate hydrate discharged from the generation section 10 is in a slurry state containing unreacted water (mixed solvent) and gas. The heat medium flows from the generation section 10 to the decomposition section 20 due to the pressure difference between the generation section 10 and the decomposition section 20.

[0036] The clathrate hydrate slurry as a heat transfer medium flows through the first main flow path 30, is decompressed by the decompression section 24, and flows into the decomposition section 20. The clathrate hydrate is decompressed and cooled by the decompression section 24. That is, the heat transfer medium is a low-temperature, low-pressure clathrate hydrate slurry at the inlet side of the decomposition section 20. The low-temperature, low-pressure clathrate hydrate slurry (heat transfer medium) that flows into the decomposition section 20 is heated by the heat absorption section 22. Specifically, the heat exchanger serving as the heat absorption section 22 exchanges heat between the heat transfer medium in the decomposition section 20 and a heat source external to the heat pump system, and the heat transfer medium absorbs the external heat and is heated. When the heat transfer medium absorbs heat equivalent to the heat of decomposition, the state of the heat transfer medium crosses the phase equilibrium line of the heat transfer medium and reaches a low-temperature, low-pressure decomposed state (a mixed phase of gas and mixed solvent) at the outlet side of the decomposition section 20.

[0037] In this way, in the heat pump system 100 of this embodiment, heat equivalent to the heat of decomposition and formation of clathrate hydrates can be pumped from an object outside the heat pump system 100 and provided to another object outside the heat pump system 100. The heat exchanger serving as the heat release section 12 and the heat exchanger serving as the heat absorption section 22 may perform heat exchange inside or outside the generation section 10 and the decomposition section 20, respectively.

[0038] 3 is an explanatory diagram schematically illustrating the sensible heat exchange mode in the heat pump system 100 of this embodiment. In the sensible heat exchange mode, the heat pump system 100 of this embodiment has the on-off valves 72, 73, 75, and 76 open and the on-off valves 74 and 77 closed. That is, in the sensible heat exchange mode, the heat exchange section 70 is connected to the first main flow path 30 and the first sub-flow path 43 (described in detail later).

[0039] As shown in FIG. 3 , in the sensible heat exchange mode, in the heat pump system 100, the clathrate hydrate slurry flowing out from the generator 10 flows through the heat exchanger 70 via the second sub-channel 71, and the mixed solvent separated by the first gas-liquid separator 14 flows through the heat exchanger 70 via the first sub-channel 43, resulting in heat exchange between the high-temperature clathrate hydrate slurry and the low-temperature mixed solvent. Therefore, the clathrate hydrate slurry cooled by the heat exchanger 70 is supplied to the decomposition section 20, and the mixed solvent heated by the heat exchanger 70 is supplied to the mixing section 18. Therefore, the clathrate hydrate slurry is supplied to the decomposition section 20 at a lower temperature than in the normal mode, and the mixed liquid is supplied to the generator 10 at a higher temperature than in the normal mode. This makes it possible to maintain a high temperature inside the generator or suppress a temperature rise inside the decomposer, thereby suppressing a decrease in the reaction efficiency of the clathrate hydrate solid formation and decomposition at the target temperature.

[0040] 4 is a flowchart showing an example of the flow of mode switching control in the control unit 90. The mode switching control is control for switching between the normal mode and the sensible heat exchange mode described above. The example shows a case where the heat pump system 100 is applied to an air conditioning device. When the control unit 90 starts the mode switching control, in step S102, the control unit 90 operates the heat pump system 100 in the normal mode.

[0041] In step S104, the control unit 90 compares the temperature with a threshold value, and operates in normal mode until the temperature falls below the threshold value (NO in step S104). When the temperature falls below the threshold value (YES in step S104), the process proceeds to step S106. Here, the temperature is a value detected by a temperature sensor (not shown) provided in the heat pump system 100. The threshold value can be set arbitrarily, and may be set to 15°C in winter, for example.

[0042] In step S106, the control unit 90 operates the heat pump system 100 in the sensible heat exchange mode. In step S108, the control unit 90 compares the temperature with a threshold value, and operates the air conditioner in the sensible heat exchange mode until the temperature exceeds the threshold value (NO in step S108). When the temperature exceeds the threshold value (YES in step S108), the process returns to step S102. Here, the threshold value is the same as the threshold value used in step S104.

[0043] In this way, the heat pump system 100 operates in sensible heat exchange mode when the temperature is 15°C or below in winter. When the temperature is low, the air conditioning system may take a long time to supply high-temperature heat during normal operation, or may not be able to supply high-temperature heat at all. In such cases, by operating in sensible heat exchange mode, the temperature of the fluid supplied to the generation unit 10 and the decomposition unit 20 is controlled, increasing the temperature difference with the outside of the heat pump system 100, allowing high-temperature heat to be supplied quickly.

[0044] In step S104, in summer, for example, the threshold value can be set to 30° C. In that case, by setting step S104 to "air temperature ≧ threshold value" and step S108 to "air temperature < threshold value," low-temperature heat can be supplied quickly.

[0045] Also, for example, the system may be configured to switch to the sensible heat exchange mode in response to an instruction from the user.

[0046] As described above, the heat pump system 100 of this embodiment transports heat by utilizing the latent heat (heat of decomposition and formation) of clathrate hydrates. The heat of decomposition and formation of clathrate hydrates is greater than the heat associated with the condensation and evaporation of a refrigerant. Therefore, compared to conventional heat pumps that utilize the exchange of heat associated with the condensation and evaporation processes of a refrigerant, the energy consumption efficiency can be improved. A heat pump system using clathrate hydrates is expected to have an electric power COP of greater than 10, even when considering an increase in auxiliary power (for example, the addition of a pump for transporting clathrate hydrate slurry). In contrast, a conventional heat pump system (using the condensation and evaporation of a refrigerant) is expected to have an electric power COP of approximately 3 to 4.

[0047] Furthermore, the heat pump system 100 of this embodiment includes a heat exchanger 70, which allows sensible heat to be exchanged between the high-temperature slurry output from the generator 10 and the low-temperature mixed solvent output from the decomposition section 20, thereby recovering sensible heat. The low-temperature slurry can be supplied to the decomposition section, and the high-temperature mixed liquid can be supplied to the generator, promoting the production of clathrate hydrates in the generator and the decomposition of clathrate hydrates in the decomposition section. This configuration allows the temperature difference between the high-temperature side and the low-temperature side during refrigeration cycle operation to be increased, thereby improving the energy consumption efficiency (COP: Coefficient of Performance).

[0048] Furthermore, according to the heat pump system 100 of this embodiment, the water and the adjuvant can be separated from the decomposition product, which is a mixed phase of gas, water, and the adjuvant, by the first gas-liquid separation unit 14, and the gas from which the water has been separated can be compressed by the compression unit 16. Therefore, compared to a case where the first gas-liquid separation unit 14 is not provided, the work of the compression unit 16 is reduced by the work of compressing the water, and the energy consumption efficiency of the heat pump system can be improved.

[0049] Furthermore, according to this configuration, the mixed solvent and compressed gas are mixed in advance by mixing unit 18, and the resulting mixed liquid is sent to production unit 10. Therefore, compared to a case where mixing unit 18 is not provided and the gas and mixed solvent are sent directly to production unit 10 without being mixed, the contact area between the gas and water is increased, and the efficiency of clathrate hydrate production in production unit 10 can be improved. As a result, the energy consumption efficiency of the heat pump system can be improved.

[0050] Second Embodiment 5 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system 100A of the second embodiment. The heat pump system 100A of the second embodiment differs from the heat pump system 100 of the first embodiment in that a gas / solid-liquid separation unit 52 is provided in the first main flow path 30, between the generation unit 10 and the pressure reduction unit 24, and upstream of the second sub-flow path 71. The same components as those of the first embodiment are denoted by the same reference numerals, and the preceding description will be referred to.

[0051] The gas / solid-liquid separation section 52 separates the gas from a gas-solid-liquid mixture (clathrate hydrate slurry) containing clathrate hydrate solids, unreacted gas, water, and auxiliary agent. The solid-liquid mixture from which the gas has been separated is also referred to as a clathrate hydrate slurry. The separated gas flows into the compression section 16 via the third sub-channel 60 and the second channel 42. The gas / solid-liquid separation section can be of a surface tension type, centrifugal force type, multi-stage filter type, cyclone type, or other type. In the case of a cyclone-type gas / solid-liquid separation section, it is expected that the solid-liquid phase and the gas phase will be 100% (volume ratio) after separation. The clathrate hydrate slurry flowing out of the gas / solid-liquid separation section 52 may contain a small amount of gas.

[0052] Because the gas / solid-liquid separation section 52 is located upstream of the pressure reduction section 24, the gas separated in the gas / solid-liquid separation section 52 is in a high-pressure state. If the gas / solid-liquid separation section 52 were not provided, excess gas in the gas-solid-liquid mixture mainly containing clathrate hydrate solids would be decompressed in the pressure reduction section 24 and flow into the compression section 16 in a low-pressure state, where it would be compressed. In contrast, in the heat pump system 100A of this embodiment, before the clathrate hydrate slurry flowing through the first main flow path 30 is decompressed, excess gas in the clathrate hydrate slurry is separated by the gas / solid-liquid separation section 52 and supplied to the compression section 16. This makes it possible to suppress a decrease in compressor efficiency in the compression section 16, thereby further improving the energy consumption efficiency (COP).

[0053] <Third embodiment> 6 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system 100B according to a third embodiment. The heat pump system 100B according to the third embodiment differs from the heat pump system 100A according to the second embodiment in that it includes a mixed solvent separation section 53 downstream of the gas / solid-liquid separation section 52 in the first main flow path 30, and a fourth sub-flow path 62 for supplying the mixed solvent separated by the mixed solvent separation section 53 to the mixing section 18. The same components as those in the second embodiment are designated by the same reference numerals, and reference is made to the preceding description.

[0054] In this embodiment, the mixed solvent separation unit 53 is a solid-liquid separator that separates liquid (mixed solvent) from the clathrate hydrate slurry (a solid-liquid mixture containing clathrate hydrate solids and mixed solvent) flowing out of the gas / solid-liquid separation unit 52. The separated mixed solvent passes through the fourth sub-channel 62 and flows into the eleventh channel 43b via the confluence unit 69. The solid phase from which the mixed solvent is separated also contains a small amount of liquid and is also referred to as clathrate hydrate slurry. The mixed solvent separation unit 53 can be of a surface tension type, centrifugal force type, cyclone type, or other type. In the case of a cyclone type mixed solvent separation unit, it is expected that the liquid phase after separation will be 100% mixed solvent, and the solid phase will be 10 / 90% mixed solvent / clathrate hydrate solid (volume ratio). The clathrate hydrate slurry flowing out of the mixed solvent separation unit 53 may contain a small amount of gas.

[0055] According to the heat pump system 100B of the present embodiment, the mixed solvent separation section 53 is provided, and the high-temperature mixed solvent is supplied to the mixing section without passing through the decomposition section 20, so that the temperature of the mixed liquid supplied to the production section 10 can be further increased and the temperature of the clathrate hydrate slurry supplied to the decomposition section 20 can be further decreased. Therefore, the temperature difference between the production section 10 on the high-temperature side and the decomposition section 20 on the low-temperature side can be further increased, and the energy consumption efficiency COP (Coefficient of Performance) can be further improved.

[0056] <Fourth embodiment> 7 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system 100C of the fourth embodiment. The heat pump system 100C of the fourth embodiment differs from the heat pump system 100B of the third embodiment in that it includes a slurry pump 39 in the first main flow path 30 and a dehydration unit 17 in the second flow path 42. The same components as those of the third embodiment are denoted by the same reference numerals, and reference is made to the preceding description.

[0057] The slurry pump 39 transports the clathrate hydrate slurry delivered from the production section 10. By providing the slurry pump 39, the heat pump system 100C can adjust the flow rate of the heat medium flowing through the first main flow path 30, and therefore can adjust the decomposition rate in the decomposition section 20. The slurry pump 39 in this embodiment is also referred to as a "transport pump."

[0058] The dehydration section 17 adsorbs water and the auxiliary agent in the gas separated in the first gas-liquid separation section 14. The dehydration section 17 can perform dehydration using an adsorbent such as silica gel. This can remove the water (mixed solvent) mixed in the gas separated in the first gas-liquid separation section 14, thereby further reducing the energy consumption by the compression section 16 and further improving the energy consumption efficiency of the heat pump system 100C. The adsorbent is not limited to silica gel, and any known adsorbent can be used. The adsorbent can be easily regenerated by heat treatment.

[0059] <Effects of the embodiment> Fig. 8 is a diagram showing the proportion of sensible heat in the total heat amount, and in Fig. 8, bar graphs are shown for cold heat, liquid sensible heat, solid sensible heat, and gas sensible heat when cold heat is generated in the heat pump systems of Embodiments 1 to 3. As shown in the figure, the total heat amount is the largest in the heat pump system of Embodiment 3.

[0060] FIG. 9 is a diagram showing the improvement in COP due to sensible heat recovery. FIG. 9 shows the COP before and after sensible heat recovery in the heat pump systems of the first to third embodiments. The COP before sensible heat recovery corresponds to operation in the normal mode described in the first embodiment, and the COP after sensible heat recovery corresponds to operation in the sensible heat recovery mode described in the first embodiment. The COP improvement rate is 1.3 times in the first embodiment, 1.2 times in the second embodiment, and 1.3 times in the third embodiment. It was confirmed that the COP can be improved by recovering sensible heat in all of the heat pump systems of the first to third embodiments. It was also confirmed that the COP improvement effect achieved by separating gas using the gas / solid-liquid separation unit 52 is greater than the COP improvement effect achieved by separating the mixed solvent using the mixed solvent separation unit 53.

[0061] Figures 8 and 9 show the required power, cold heat output, and COP estimated using 1D-SIM (1D simulation), with each sensible heat calculated as the product of the heat exchange volume (described below) and the weight ratio of the gas, solid, and liquid. The 1D-SIM model was created using commercially available software, Open-Modelica, based on the experimentally obtained formation and decomposition rates of clathrate hydrates. The input conditions are described below. The COP can be roughly calculated using the following formula (1): COP = (cold heat output - liquid sensible heat - solid sensible heat - gas sensible heat) / required power ... (Equation 1)

[0062] Fig. 10 is a diagram showing the specifications of the heat exchanger. The heat exchanger shown in Fig. 10 has a heat transfer area of 6 m 2, and the overall heat transfer coefficient is 50. The diagram shows a case without a gas / solid-liquid separation section (when the clathrate hydrate slurry flowing through the heat exchanger contains gas) and a case with a gas / solid-liquid separation section (when the gas content in the clathrate hydrate slurry flowing through the heat exchanger is reduced). As shown in the diagram, it was confirmed that the temperature efficiency at high temperatures can be improved by having a gas / solid-liquid separation section.

[0063] FIG. 11 is a diagram showing the physical properties of gas, water, and clathrate hydrate solids. FIG. 12 is a diagram showing the temperature change of the heat medium caused by the heat exchanger in the heat pump system 100 of the first embodiment. FIG. 13 is a diagram showing the temperature change of the heat medium caused by the heat exchanger in the heat pump system 100A of the second embodiment. FIG. 14 is a diagram showing the temperature change of the heat medium caused by the heat exchanger in the heat pump system 100B of the third embodiment. FIGS. 12 to 14 show the results of the trial calculations using the above-mentioned 1D-SIM. As shown in FIGS. 12 to 14, it was confirmed that in all of the heat pump systems of the first to third embodiments, the temperature of the clathrate hydrate slurry on the production section side can be lowered and the temperature of the mixed solvent separated by the first gas-liquid separation section 14 can be increased.

[0064] FIG. 15 shows the relationship between the power COP and the gas-solid-liquid ratio. In FIG. 15, the axis of the values indicated by each point is indicated by an arrow. The COP shown in FIG. 15 was calculated using the above-mentioned (Equation 1) based on the results of the 1D-SIM calculation. In the example shown in FIG. 15, the COP was calculated by changing the solid ratio in the gas-solid-liquid mixed phase. The COP when using the heat pump system 100 of the first embodiment (configuration without the gas-solid-liquid separation unit 52) is indicated by an open triangle, and the COP when using the heat pump system 100A of the second embodiment is indicated by a filled triangle. In the heat pump system 100A of the second embodiment, gas is separated in the gas-solid-liquid separation unit 52 as described above. Therefore, the gas concentration in the heat medium flowing into the decomposition unit 20 is approximately 0 (zero), which can be said to be a solid-liquid mixed phase. On the other hand, since the heat pump system 100 of the first embodiment does not have the gas-solid-liquid separation unit 52, the heat medium flowing into the decomposition unit 20 is a gas-solid-liquid mixed phase. The example shown in FIG. 15 illustrates operation in normal mode.

[0065] In the example shown in Fig. 15, the COP is calculated under the following conditions: the temperature of the heat medium on the inlet side of the generation section 10 is 20°C, and the temperature of the heat medium on the outlet side of the decomposition section 20 is 10°C. A slurry pump (not shown) is provided in the first main flow path 30 shown in Fig. 1 and the third flow path 32 shown in Fig. 5, and the rotation speed of the slurry pump is 800 rpm. The volume of the refrigerant gas in the mixed liquid flowing into the generation section 10 is 91%.

[0066] As shown in the figure, the heat pump system 100A of the second embodiment has an improved COP compared to the heat pump system 100 of the first embodiment. As shown in the figure, the COP can be improved by separating the gas (refrigerant gas) from the clathrate hydrate slurry.

[0067] Fig. 16 is a diagram showing the results of calculations of the amount of cold generated, input power, and COP in the heat pump systems of the first to third embodiments. The COP shown in Fig. 16 was also calculated by the above-mentioned (Equation 1) using the results of calculations using the above-mentioned 1D-SIM. As shown in the figure, it was confirmed that in the heat pump systems of the first to third embodiments, although the input power is constant, the COP can be improved by providing the gas / solid-liquid separation unit 52 and the mixed solvent separation unit 53.

[0068] FIG. 17 shows the input conditions for 1D-SIM. FIG. 18 is a diagram showing a 1D-SIM model of the generation unit. FIG. 18 shows an outline of the internal structure of the generation unit. FIG. 19 is an explanatory diagram showing an example of a 1D-SIM model and simulation results. As shown in FIG. 19, by creating a SIM model and inputting temperature conditions, etc., it is possible to obtain simulation results such as those shown on the right side of FIG. 19. The solid fraction of the simulation results is solid / (solid + liquid + gas), as in FIG. 15.

[0069] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0070] The pressure reduction section 24 may be provided in the first main flow path 30 through which the heat transfer medium flows from the production section 10 to the decomposition section 20, or may be provided between the decomposition section 20 and the first gas-liquid separation section 14 in the second main flow path 40 through which the heat transfer medium flows from the decomposition section 20 to the production section 10. Alternatively, the decomposition section 20 may be provided with the pressure reduction section 24, or the compression section 16 may be provided with the pressure reduction section 24. In this case, the pressure inside the decomposition section 20 can be reduced and the decomposition of clathrate hydrates in the decomposition section 20 can be promoted.

[0071] In the fourth embodiment, an example was shown in which the heat pump system was provided with the slurry pump 39, but the slurry pump 39 may also be provided in the heat pump systems of the first and second embodiments.

[0072] In the fourth embodiment, an example was shown in which the heat pump system was provided with the dehydration unit 17, but the heat pump systems of the first and second embodiments may also be provided with the dehydration unit 17.

[0073] Although the above embodiment illustrates a configuration in which the second gas-liquid separation unit 56 is provided, the second gas-liquid separation unit 56 does not necessarily have to be provided.

[0074] In the above embodiment, an example was shown in which the normal mode and the sensible heat exchange mode were switched depending on the temperature, but switching may also be performed based on other conditions. For example, the air conditioner may operate in the sensible heat exchange mode when the required heat quantity is large. Furthermore, the air conditioner may operate in the sensible heat exchange mode in accordance with a user instruction. For example, the user may instruct the air conditioner to switch to the sensible heat exchange mode via a controller.

[0075] In the third embodiment, the mixed solvent separated in the mixed solvent separation unit 53 flows into the first sub-channel 43, is added to the mixed solvent separated by the first gas-liquid separation unit 14, and is then supplied to the mixing unit 18. However, the mixed solvent separated in the mixed solvent separation unit 53 may be supplied directly to the mixing unit 18 without flowing into the first sub-channel 43.

[0076] The present invention has been described above based on embodiments and modifications, but the above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the claims, and the present invention includes equivalents thereof. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0077] The present invention can also be realized as the following application examples. [Application example 1] A heat pump system in which a heat transfer medium transports heat by repeating a decomposition process and a formation process of a clathrate hydrate, a generation section into which a mixture of a mixed solvent of a liquid adjuvant and water and a gas is introduced and into which a clathrate hydrate is generated; a decomposition section into which the clathrate hydrate is decomposed and into which a decomposition product, which is a mixed phase of the gas and the mixed solvent, is delivered; a first main flow path through which the heat transfer medium flows from the generation section to the decomposition section; a second main flow path through which the heat transfer medium flows from the decomposition section to the generation section; a heat dissipation unit that dissipates heat from the heat medium by heat exchange between the heat medium in the generation unit and a heat source outside the heat pump system; a pressure reducing section that reduces the pressure of the heat medium in the decomposition section; a heat absorption unit that absorbs heat into the heat medium by heat exchange between the heat medium in the decomposition unit and a heat source outside the heat pump system; a gas-liquid separation section connected to the decomposition section via the second main flow path, which separates the gas in the decomposition product sent out from the decomposition section from the mixed solvent; a compression section connected to the gas-liquid separation section via the second main flow path and configured to compress the gas separated by the gas-liquid separation section; a mixing section connected to the compression section and the production section via the second main flow path and connected to the gas-liquid separation section via a first sub-flow path, and configured to produce the mixed liquid containing the mixed solvent separated by the gas-liquid separation section and the gas compressed by the compression section; a heat exchange unit connected to the first main flow path and the first sub-flow path, which performs heat exchange by circulating the slurry containing the clathrate hydrate flowing out of the production unit and the mixed solvent separated by the gas-liquid separation unit; Equipped with Heat pump system. [Application example 2] The heat pump system according to Application Example 1, a gas / solid-liquid separation unit connected to the generation unit via the first main flow path and separating the gas from the slurry generated in the generation unit; a third sub-channel for supplying the gas separated by the gas / solid-liquid separation unit to the mixing unit; Further provided with Heat pump system. [Application example 3] The heat pump system according to Application Example 1 or Application Example 2, a mixed solvent separation unit connected downstream of the gas / solid-liquid separation unit via the first main flow path and configured to separate the mixed solvent from the slurry after passing through the gas / solid-liquid separation unit; a fourth sub-flow path connected to the mixed solvent separation unit for supplying the mixed solvent separated by the mixed solvent separation unit to the mixing unit; Further provided with Heat pump system. [Application example 4] The heat pump system according to any one of Application Examples 1 to 3, Further provided is a transport pump disposed in the first main flow path and transporting the heat medium. Heat pump system. [Application example 5] The heat pump system according to any one of Application Examples 1 to 4, a dehydration unit disposed between the gas-liquid separation unit and the compression unit, which adsorbs the mixed solvent in the gas separated by the gas-liquid separation unit. Heat pump system. [Explanation of symbols]

[0078] 10...Generation section 12...Heat radiation part 14...First gas-liquid separation section 15...Liquid transfer pump 16...Compression section 17...Dehydration section 18…Mixing section 20…Disassembly part 22...heat absorption part 24...Decompression section 30...First main channel 39...Slurry pump 40…Second main flow path 43...First sub-channel 43a...10th channel 43b...11th channel 43d...Bypass flow path 52...Gas / solid-liquid separation section 53... Mixed solvent separation section 56...Second gas-liquid separation section 58...Liquid transfer pump 60...Third sub-channel 62...4th sub-channel 69...Confluence 70...Heat exchange section 71…Second sub-channel 80...5th sub-channel 90...Control unit 100, 100A, 100B, 100C...Heat pump system

Claims

1. A heat pump system in which a heat transfer medium transports heat by repeating a decomposition process and a formation process of a clathrate hydrate, a generation section into which a mixture of a mixed solvent of a liquid adjuvant and water and a gas is introduced and into which a clathrate hydrate is generated; a decomposition section into which the clathrate hydrate is decomposed and into which a decomposition product, which is a mixed phase of the gas and the mixed solvent, is delivered; a first main flow path through which the heat transfer medium flows from the generation section to the decomposition section; a second main flow path through which the heat medium flows from the decomposition section to the generation section; a heat dissipation unit that dissipates heat from the heat medium by heat exchange between the heat medium in the generation unit and a heat source outside the heat pump system; a pressure reducing section that reduces the pressure of the heat medium in the decomposition section; a heat absorption unit that absorbs heat into the heat medium by heat exchange between the heat medium in the decomposition unit and a heat source outside the heat pump system; a gas-liquid separation section connected to the decomposition section via the second main flow path, which separates the gas in the decomposition product delivered from the decomposition section from the mixed solvent; a compression section connected to the gas-liquid separation section via the second main flow path and configured to compress the gas separated by the gas-liquid separation section; a mixing section connected to the compression section and the production section via the second main flow path and connected to the gas-liquid separation section via a first sub-flow path, and configured to produce the mixed liquid containing the mixed solvent separated by the gas-liquid separation section and the gas compressed by the compression section; a heat exchange unit connected to the first main flow path and the first sub-flow path, which performs heat exchange by circulating the slurry containing the clathrate hydrate flowing out of the production unit and the mixed solvent separated by the gas-liquid separation unit; Equipped with Heat pump system.

2. The heat pump system according to claim 1, a gas / solid-liquid separation unit connected to the generation unit via the first main flow path and separating the gas from the slurry generated in the generation unit; a third sub-flow passage for supplying the gas separated by the gas / solid-liquid separation section to the mixing section; Further provided with Heat pump system.

3. The heat pump system according to claim 2, a mixed solvent separation section connected downstream of the gas / solid-liquid separation section via the first main flow path and configured to separate the mixed solvent from the slurry that has passed through the gas / solid-liquid separation section; a fourth sub-flow path connected to the mixed solvent separation unit for supplying the mixed solvent separated by the mixed solvent separation unit to the mixing unit; Further provided with Heat pump system.

4. The heat pump system according to claim 1, The heat transfer system further includes a transport pump disposed in the first main flow path and configured to transport the heat transfer medium. Heat pump system.

5. The heat pump system according to any one of claims 1 to 4, a dehydration unit disposed between the gas-liquid separation unit and the compression unit, which adsorbs the mixed solvent in the gas separated by the gas-liquid separation unit. Heat pump system.

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