Absorption refrigeration cycle and compression absorption refrigeration cycle

Abstract

An absorption cycle (110) according to the present invention has a warming potential of less than 1,000, and operates using a refrigerant that contains at least one of an HFO refrigerant, an HFC refrigerant and an HCFO refrigerant, and an absorbent liquid that contains at least one of the compounds represented by formula (1), formula (2) or formula (3).　(1): R1-(OCH2CH2)n-OR2 (2): R1-(OCH2CH(CH3))n-OR2 (3): R1COO-(OCH2CH2)n-OR2 In the formulae, each of R1 and R2 independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; and n represents an integer of 1 to 6.

Description

[Technical Field]

[0001] This invention relates to absorption refrigeration cycles and compression absorption refrigeration cycles. [Background technology]

[0002] Conventionally, cooling systems in air conditioners have used compression refrigeration cycles using compressors or absorption refrigeration cycles driven by heat.

[0003] Furthermore, in order to improve the performance of the system, systems that incorporate a compressor into the absorption refrigeration cycle are being considered. For example, Japanese Patent Publication No. 05-332633 (Patent Document 1) and Japanese Patent Publication No. 2003-307359 (Patent Document 2) disclose a system in which ammonia is used as the refrigerant and a compressor is installed between the evaporator and the absorber. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 05-332633 [Patent Document 2] Japanese Patent Publication No. 2003-307359 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the technologies described in Patent Documents 1 and 2 use ammonia refrigerants, which, although having a low global warming potential, are toxic and require measures to be taken in case of refrigerant leakage. Furthermore, while Patent Document 1 discloses an example using R134a refrigerant, which is a non-toxic HFC refrigerant, it has a high global warming potential and may become unusable in the future.

[0006] Therefore, there is a need to realize absorption refrigeration cycles that can operate with refrigerants that are non-toxic and have a low global warming potential, as well as compression-absorption refrigeration cycles equipped with compressors. [Means for solving the problem]

[0007] The characteristic configuration of the absorption refrigeration cycle according to the present invention is that the global warming potential is less than 1000, and it operates using a refrigerant containing at least one of an HFO-based refrigerant, an HFC-based refrigerant, and an HCFO-based refrigerant, and Triethylene glycol butyl methyl ether an absorption liquid containing 。

[0008] According to this configuration, an absorption refrigeration cycle using a non-toxic refrigerant with a relatively low global warming potential can be realized.

[0009] Hereinafter, preferred embodiments of the present invention will be described. However, the scope of the present invention is not limited by the preferred embodiment examples described below.

[0012] The characteristic configuration of the compression absorption refrigeration cycle according to the present invention is that any one of the above absorption refrigeration cycles and a compression refrigeration cycle are integrated in a manner of sharing the refrigerant.

[0013] According to this configuration, a compression absorption refrigeration cycle using a non-toxic refrigerant with a relatively low global warming potential can be realized.

[0014] Further features and advantages of the present invention will become more apparent from the following illustrative and non-limiting description with reference to the drawings.

Brief Description of the Drawings

[0015] [Figure 1] It is a flowchart of an air conditioning system according to an embodiment. [Figure 2] It is a flowchart of an air conditioning system according to another embodiment. [Figure 3] It is a flowchart of an air conditioning system according to another embodiment.

Modes for Carrying Out the Invention

[0016] Embodiments of the absorption refrigeration cycle and the compression absorption refrigeration cycle according to the present invention will be described with reference to the drawings. Hereinafter, an example in which the compression absorption refrigeration cycle according to the present invention is applied to an air conditioning system 100 for a car air conditioner (an example of a compression absorption refrigeration cycle) will be described.

[0017] 〔Configuration of the air conditioning system〕 The air conditioning system 100 according to the present embodiment has a configuration in which an absorption refrigeration cycle and a compression refrigeration cycle are integrated in a manner of sharing a refrigerant. The air conditioning system 100 includes a high-pressure stage section 110, a low-pressure stage section 120, and a gas-liquid separation device 130 (FIG. 1).

[0018] The high-pressure stage section 110 is provided with a pump 111, a solution decompression device 112, a solution heat exchanger 113, a regenerator 114, a condenser 115, a refrigerant expansion device 116, and an absorber 117.

[0019] The low-pressure stage section 120 is provided with a refrigerant expansion device 121, an evaporator 122, and a compressor 123. The compressor 123 is driven by a motor 124. However, the compressor 123 may be driven by power such as an engine.

[0020] The gas-liquid separation device 130 is provided at the boundary between the high-pressure stage section 110 and the low-pressure stage section 120. In the high-pressure stage section 110, it is provided at a position downstream of the refrigerant expansion device 116 and upstream of the absorber 117, and in the low-pressure stage section 120, it is provided downstream of the compressor 123 and upstream of the refrigerant expansion device 121.

[0021] 〔Operation of the air conditioning system〕 The case where the air conditioning system 100 performs a cooling operation will be described. In the evaporator 122, the air in the vehicle is cooled. That is, in the evaporator 122, the refrigerant receives heat from the air in the vehicle and the refrigerant evaporates. The refrigerant is compressed in the compressor 123 to become superheated vapor and is introduced into the gas-liquid separation device 130.

[0022] As will be described later, the refrigerant separated from the absorbent liquid (strong solution) that absorbed the refrigerant in the regenerator 114 is condensed in the condenser 115. The condensed refrigerant is depressurized in the refrigerant expansion device 116 to become wet vapor, which is then introduced into the gas-liquid separator 130. In the gas-liquid separator 130, this wet vapor refrigerant is mixed with the aforementioned superheated vapor refrigerant compressed in the compressor 123, and then separated into saturated liquid and saturated vapor.

[0023] The gaseous component (saturated vapor) of the refrigerant separated in the gas-liquid separator 130 flows through the high-pressure stage 110. The gaseous component of the refrigerant is absorbed by the absorbent liquid in the absorber 117. In this embodiment, the absorber 117 is air-cooled, and the heat generated by the mixing of the refrigerant and the absorbent liquid is removed by air cooling. The absorbent liquid (strong solution) that has absorbed the refrigerant is pressurized by the pump 111 and goes to the solution heat exchanger 113, where it is preheated before going to the regenerator 114.

[0024] In the regenerator 114, the absorbent liquid (strong solution) that has absorbed the refrigerant is heated. At this time, some of the refrigerant vaporizes due to the difference in boiling points between the refrigerant and the absorbent liquid. The energy for heating is supplied by the waste heat from the engine.

[0025] In the regenerator 114, the absorbent liquid (weak solution) from which some of the refrigerant has been separated is cooled in the solution heat exchanger 113, then depressurized in the solution depressurization device 112 and returned to the absorber 117.

[0026] The refrigerant separated from the absorbent liquid (strong solution) in the regenerator 114 is condensed in the condenser 115. As described above, the condensed refrigerant is depressurized in the refrigerant expansion device 116 to become wet vapor, which is then introduced into the gas-liquid separator 130.

[0027] However, in situations where there is little exhaust heat from the engine, such as immediately after starting the vehicle, there may be insufficient energy to heat the absorbent liquid (strong solution) that has absorbed the refrigerant in the regenerator 114. In this case, in addition to the path provided with the absorber 117, pump 111, solution heat exchanger 113, and regenerator 114, a path provided with the compressor 118 is also used. In this case, a portion of the gaseous component of the refrigerant separated in the gas-liquid separator 130 is compressed in the compressor 118 to become superheated steam, which is then introduced into the condenser 115 along with the refrigerant separated from the absorbent liquid (strong solution) in the regenerator 114. The compressor 118 is driven by a motor 119. However, the compressor 118 may also be driven by a power source such as an engine. If there is little energy to heat the absorbent liquid (strong solution) that has absorbed the refrigerant in the regenerator 114, all of the gaseous component of the refrigerant separated in the gas-liquid separator 130 is compressed in the compressor 118 to become superheated steam, which is then introduced into the condenser 115.

[0028] [Refrigerant] In the air conditioning system 100 according to this embodiment, the refrigerant includes at least one of HFO-based refrigerants, HFC-based refrigerants, and HCFO-based refrigerants, and has a global warming potential (GWP) of less than 1000.

[0029] The term "HFO-based refrigerant" (hydrofluoroolefin-based refrigerant) refers to a group of compounds having a structure in which some hydrogen atoms of an unsaturated hydrocarbon compound are replaced by fluorine atoms. Examples include R1234yf (2,3,3,3-tetrafluoropropene), R1234ze(E) (trans-1,3,3,3-tetrafluoropropene), R1234ze(Z) (cis-1,3,3,3-tetrafluoropropene), R1336mzz(E) (trans-1,1,1,4,4,4-hexafluoro-2-butane), R1336mzz(Z) (cis-1,1,1,4,4,4-hexafluoro-2-butane), and R1243zf (3,3,3-trifluoropropene), R1233zd(E) (trans-1-chloro-3,3,3-trifluoropropene). Furthermore, each of the refrigerants exemplified above has a global warming potential (GWP) of less than 10, and thus falls under the category of so-called low-GWP refrigerants.

[0030] The term "HFC refrigerant" (hydrofluorocarbon refrigerant) refers to a group of compounds in which some hydrogen atoms of a saturated hydrocarbon compound are replaced by fluorine atoms. For example, R32 (difluoromethane) is one such example. R32 is a so-called low GWP refrigerant, with a global warming potential of 675.

[0031] The term "HCFO refrigerant" (hydrochlorofluoroolefin refrigerant) refers to a group of unsaturated hydrocarbon compounds composed of hydrogen, chlorine, fluorine, and carbon. For example, R1224yd(Z) ((Z)-1-chloro-2,3,3,3-tetrafluoropropene) is an example. R1224yd(Z) is a so-called low GWP refrigerant, with a global warming potential of less than 10.

[0032] In the air conditioning system according to this embodiment, the refrigerant may be one type selected from HFO-based refrigerants, HFC-based refrigerants, and HCFO-based refrigerants, or a mixture of two or three types. That is, the refrigerant may be only an HFO-based refrigerant, only an HFC-based refrigerant, only an HCFO-based refrigerant, a mixture of an HFO-based refrigerant and an HFC-based refrigerant, a mixture of an HFO-based refrigerant and an HCFO-based refrigerant, a mixture of an HFC-based refrigerant and an HCFO-based refrigerant, or a mixture of an HFO-based refrigerant, an HFC-based refrigerant, and an HCFO-based refrigerant. Furthermore, in each case, the HFO-based refrigerant, HFC-based refrigerant, and HCFO-based refrigerant may be a single compound or a mixture of multiple compounds belonging to each classification.

[0033] [Absorbent solution] In the air conditioning system 100 according to this embodiment, the absorbent liquid contains at least one of the compounds represented by formula (1), formula (2), and formula (3). R 1 -(OCH2CH2) n -OR 2 (1) R 1 -(OCH2CH(CH3)) n -OR 2 (2) R 1 COO-(OCH2CH2) n -OR2 (3)

[0034] R 1 and R 2 are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Here, the alkyl group may be a linear alkyl group or a branched alkyl group. R1 and R2 are each independently preferably selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, and a butyl group.

[0035] n is an integer of 1 or more and 6 or less. However, n is preferably an integer of 1 or more and 3 or less.

[0036] In the air conditioning system according to this embodiment, as the absorbent liquid, one compound selected from the group of compounds represented by formula (1), formula (2), and formula (3) may be used alone, or two or more compounds may be mixed and used. Further, when two or more compounds are mixed and used, the general formulas of the respective compounds may be the same or different. For example, a mixture of two or more compounds represented by formula (1) may be used, or a mixture of a compound represented by formula (1) and a compound represented by formula (2) may be used.

[0037] Examples of compounds represented by formula (1) include, but are not limited to, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol ethyl methyl ether, ethylene glycol diethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol mono-2-methylpropyl ether, ethylene glycol butyl ethyl ether, ethylene glycol dibutyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, diethylene glycol monopropyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol monobutyl ether, diethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, diethylene glycol monohexyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monoethyl ether, triethylene glycol ethyl methyl ether, triethylene glycol diethyl ether, triethylene glycol monobutyl ether, triethylene glycol butyl methyl ether, and triethylene glycol dibutyl ether.

[0038] Examples of compounds represented by formula (2) include, but are not limited to, propylene glycol, propylene glycol monomethyl ether, propylene glycol dimethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol dimethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, and tripropylene glycol monobutyl ether.

[0039] Examples of compounds represented by formula (3) include, but are not limited to, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monoisopropyl ether acetate, and diethylene glycol monobutyl ether acetate.

[0040] The absorbent solution preferably contains one or more compounds selected from the group consisting of ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol monohexyl ether, triethylene glycol butyl methyl ether, propylene glycol monopropyl ether, and diethylene glycol monoethyl ether acetate. More preferably, the absorbent solution contains one or more compounds selected from the group consisting of ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol butyl methyl ether, propylene glycol monopropyl ether, and diethylene glycol monoethyl ether acetate.

[0041] [Other Embodiments] In the above embodiment, an air conditioning system 100 (compression absorption refrigeration cycle) having a configuration in which an absorption refrigeration cycle and a compression refrigeration cycle are combined in a manner that shares a refrigerant was described as an example. However, the above combination of refrigerant and absorbent liquid may also be applied to an absorption refrigeration cycle that does not have a compression refrigeration cycle.

[0042] Furthermore, although the above embodiment described an example in which a compressor 118 is provided in the high-pressure stage 110, the absorption refrigeration cycle according to the present invention may not have a compressor. An example of an air conditioning system equipped with an absorption refrigeration cycle without a compressor is shown in Figures 2 and 3. Note that in Figures 2 and 3, the same reference numerals are used for the same components as in the air conditioning system 100 in Figure 1.

[0043] In the air conditioning system 200A shown in Figure 2, an evaporator 201 and a condenser 202 are provided in place of the gas-liquid separator 130 in the air conditioning system 100. The evaporator 201 functions as a subcooler for the refrigerant. In the absorption refrigeration cycle consisting of a regenerator 114, condenser 115, refrigerant expansion device 116, evaporator 201, pump 111 and solution depressurization device 112, and solution heat exchanger 113, the combination of refrigerant and absorbent liquid according to the above embodiment is used. On the other hand, the refrigerant in the compression refrigeration cycle consisting of a refrigerant expansion device 121, evaporator 122, compressor 123, condenser 202, and evaporator 201 is not limited. In the air conditioning system 200A, the operating pressure of the absorption refrigeration cycle is higher than when water is used as the refrigerant, so the absorption refrigeration cycle can be miniaturized.

[0044] In the air conditioning system 200B shown in Figure 3, the condenser 202 is shared between the absorption refrigeration cycle and the compression refrigeration cycle. Compared to the air conditioning system 200A (Figure 2), the condenser for the absorption refrigeration cycle (condenser 115 in Figure 2) is omitted. This allows for further miniaturization of the air conditioning system 200B compared to the air conditioning system 200A. In the air conditioning system 200B, the regenerator 114, condenser 202, refrigerant expansion device 116, evaporator 201, pump 111 and solution depressurization device 112, and solution heat exchanger 113 form the absorption refrigeration cycle, while the refrigerant expansion device 121, evaporator 122, compressor 123, condenser 202, and evaporator 201 form the compression refrigeration cycle. Here as well, the evaporator 201 functions as a subcooler for the refrigerant. Furthermore, since the condenser 202 is shared, the refrigerant used in the absorption refrigeration cycle and the compression refrigeration cycle in the air conditioning system 200B is the same, and the refrigerant according to the above embodiment is used. Also, the absorbent liquid used in the absorption refrigeration cycle is as described in the above embodiment.

[0045] Although embodiments of the invention in which the refrigerant includes at least one of HFO-based refrigerants, HFC-based refrigerants, and HCFO-based refrigerants have been described above, it is clear that embodiments of the invention in which the refrigerant includes at least one of HFO-based refrigerants and HFC-based refrigerants (where HCFO-based refrigerants are not included as candidate refrigerants) are also disclosed in this specification. That is, the characteristic configuration of the absorption refrigeration cycle according to this invention is characterized by operating using a refrigerant having a global warming potential of less than 1000 and containing at least one of HFO-based refrigerants and HFC-based refrigerants, and an absorbent containing at least one of the compounds represented by formulas (1), (2), and (3). R 1 -(OCH2CH2) n -OR 2 (1) R 1 -(OCH2CH(CH3)) n -OR 2 (2) R 1 COO-(OCH2CH2) n -OR 2 (3) R 1 and R 2 Each of these is independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n is an integer between 1 and 6.

[0046] With regard to other configurations, the embodiments disclosed herein are illustrative in all respects, and it should be understood that the scope of the present invention is not limited thereto. Those skilled in the art will readily understand that modifications can be made as appropriate without departing from the spirit of the invention. Therefore, other embodiments modified without departing from the spirit of the invention are naturally included within the scope of the present invention. [Examples]

[0047] The present invention will be further described below with reference to examples. However, the following examples are not limiting to the present invention.

[0048] [Compounds of the Examples and Comparative Examples] Example 1: Diethylene glycol dibutyl ether Examples 2, 4, and 6: Triethylene glycol butyl methyl ether Examples 3 and 5: Diethylene glycol diethyl ether Comparative Example 1: [HMIM][Tf2N] (Ionic Liquid) Comparative Example 2: [BMIM][Tf2N] (Ionic Liquid) Comparative Example 3: [BMIM][PF6] (Ionic Liquid)

[0049] Note that "[HMIM]" represents "1-hexyl-3-methylimidazolium cation," "[BMIM]" represents "1-butyl-3-methylimidazolium cation," and "[Tf2N]" represents "bistrifluoromethylsulfonyl anion."

[0050] [Test Method] (Test 1) For each compound in the examples and comparative examples, the absorption characteristics were measured using R1234yf as the refrigerant, and the circulation ratio in the absorption refrigeration cycle was determined. The circulation ratio was determined using the following temperature conditions: evaporation temperature 10°C, regeneration temperature 80°C, absorption temperature 35°C, and condensation temperature 35°C. The results are shown in Table 1.

[0051] Table 1: Circulation ratio and refrigerant concentration of examples and comparative examples [Table 1]

[0052] As shown in Table 1, in Examples 1 to 3, which are embodiments of the present invention, a lower circulation ratio was obtained compared to Comparative Examples 1 and 2. From this, it was found that Examples 1 to 3 exhibit good physical properties as absorbents to be used in combination with R1234yf.

[0053] (Exam 2) For each compound in the examples and comparative examples, the absorption characteristics were measured when R32 was used as the refrigerant, and the circulation ratio in the absorption refrigeration cycle was determined. The circulation ratio was determined using the following temperature conditions: evaporation temperature 10°C, regeneration temperature 80°C, absorption temperature 35°C, and condensation temperature 35°C. The results are shown in Table 2.

[0054] Table 2: Circulation ratio and refrigerant concentration of examples and comparative examples [Table 2]

[0055] As shown in Table 2, in Examples 4 and 5, which are embodiments of the present invention, a lower circulation ratio was obtained compared to Comparative Example 3. From this, it was found that Examples 4 and 5 exhibit good physical properties as absorbents to be used in combination with R32.

[0056] (Exam 3) For the compound in Example 6, the absorption characteristics were measured when R1224yd(Z) was used as the refrigerant, and the circulation ratio in the absorption refrigeration cycle was determined. The circulation ratio was determined using the following temperature conditions: evaporation temperature 10°C, regeneration temperature 80°C, absorption temperature 35°C, and condensation temperature 35°C. The results are shown in Table 3.

[0057] Table 3: Circulation ratio and refrigerant concentration in Example 6 [Table 3]

[0058] As shown in Table 3, in Example 6, which is an embodiment of the present invention, a circulation ratio equivalent to that of Examples 1 to 5 was obtained. From this, it was found that Example 6 exhibits good physical properties as an absorbent used in combination with R1224yd(Z). [Industrial applicability]

[0059] The present invention can be used, for example, in absorption refrigeration cycles and compression absorption refrigeration cycles for air conditioning systems. [Explanation of Symbols]

[0060] 100: Air conditioning system 110: High-voltage section 111: Pump 112: Solution vacuum device 113: Solution heat exchanger 114: Regenerator 115: Condenser 116: Refrigerant expansion device 117: Absorber 118: Compressor 120: Low-pressure section 121: Refrigerant expansion device 122: Evaporator 123: Compressor 124: Motor 130: Gas-liquid separation equipment

Claims

1. An absorption refrigeration cycle that operates using a refrigerant having a global warming potential of less than 1000 and containing at least one of HFO-based refrigerants, HFC-based refrigerants, and HCFO-based refrigerants, and an absorbent containing triethylene glycol butyl methyl ether.

2. A compression absorption refrigeration cycle in which the absorption refrigeration cycle described in claim 1 and the compression refrigeration cycle are combined in a manner that shares the refrigerant.

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