System for use in regenerative cooling cycle and regenerative cooling method

Abstract

This invention discloses a system and method for a cooling cycle based on a regenerative injector, which utilizes the injector as the power source in the cooling circuit to regenerate subcooled refrigerant in a single-stage cooling cycle.

Description

System and Single-Stage Cooling Method for Single-Stage Cooling Cycle The present invention generally relates to systems and methods for a regenerative ejector-based cooling cycle. More specifically, the systems and methods utilize an ejector as the power in a cooling loop to regeneratively subcool a refrigerant in a single-stage cooling cycle. It is well-known to use heat exchangers to modify the thermodynamic performance of a cooling cycle. An exemplary heat exchanger in a conventional cooling cycle is referred to as a suction line heat exchanger (SLHX). The purpose of the SLHX is to preheat the refrigerant before it enters the compressor. Other concepts have been proposed to use heat exchangers to subcool the refrigerant in a cooling cycle using an ejector. For example, in FIG. 1, a heat exchanger is used in system 100 for a conventional two-stage cooling cycle with an ejector to subcool the refrigerant and reduce the total power consumption of the system, which is also referred to as cascade refrigeration. Vapor first refrigerant enters a first compressor 104 from an evaporating first refrigerant line 102 and is compressed to an evaporation pressure determined by ambient conditions. The compressed vapor first refrigerant passes through a compressed first refrigerant line 106 to a heat exchanger referred to as an evaporative condenser 108. The condensed liquid first refrigerant passes through a condensed refrigerant line 110 to a first expansion valve 107 and / or an ejector 114 based on a control valve (not shown). The condensed liquid first refrigerant expands when passing through the expansion valve 107. The expanded two-phase first refrigerant passes through a first expanded first refrigerant line 118 to a heat exchanger referred to as a cascade exchanger 132, where it evaporates by heat and is used to cool a second refrigerant from a compressed second refrigerant line 130, which forms part of the second stage of the cooling cycle. The evaporated first refrigerant passes through an evaporating first refrigerant line 102 to the compressor 104. The condensed liquid of the first refrigerant enters the ejector 114 as the motive fluid, mixes in the ejector 114 with the evaporated first refrigerant from another evaporating first refrigerant line 126, and is ejected from the ejector 114 as a two-phase first refrigerant. The two-phase first refrigerant passes through the two-phase first refrigerant line 116 to the flash economizer 112, where it flashes into a vapor first refrigerant and a liquid first refrigerant. The vapor first refrigerant from the flash economizer 112 enters the compressor 104 through the evaporating first refrigerant line 102. The liquid first refrigerant from the flash economizer 112 passes through the liquid first refrigerant line 120 to the second expansion valve 121. The liquid first refrigerant expands when passing through the second expansion valve 121. The expanded two-phase first refrigerant passes through the second expanded first refrigerant line 122 to a heat exchanger called the subcooler 124, where it is evaporated by heat and used to cool a second refrigerant in a second refrigerant line 134 that forms part of the second stage of the cooling cycle. The evaporated first refrigerant from the subcooler 124 passes through another evaporating first refrigerant line 126 to the ejector 114. The evaporated second refrigerant passes through the evaporated second refrigerant line 128 to the second compressor 136. The compressed vapor second refrigerant passes through the compressed second refrigerant line 130 to the cascade exchanger 132, where it is cooled. The cooled liquid second refrigerant passes through the cooled second refrigerant line 134 to the subcooler 124, where it is further cooled. The subcooled liquid second refrigerant from the subcooler 124 passes through the subcooled second refrigerant line 135 to the third expansion valve 138. The expanded two-phase second refrigerant passes through the expanded second refrigerant line 139 to a heat exchanger called the evaporator 140, where it is evaporated by heat into an evaporated second refrigerant. Thus, the two-stage cooling cycle system 100 requires two cascade cooling loops and refrigerants for each respective stage. Cross-reference to Related Applications This application, PCT applications Nos. PCT / US20 / 62972 and PCT / US21 / 49010, and U.S. Patents Nos. 10,514,201, 10,533,793, 10,465,983, and 10,514,202, each of which is incorporated herein by reference and jointly assigned to Bechtel Energy Technologies & Solutions, Inc. The subject matter of the present invention is clearly described. However, the description itself is not intended to limit the scope of the present invention. Therefore, in combination with other current or future technologies, the subject matter described herein may also be embodied in other ways to include different structures, steps, and / or combinations similar to and / or less than those described herein. Although the term "step" may be used herein to describe different elements of the methods employed, the term should not be construed as implying any particular order among or between the various steps disclosed herein, unless the description specifically limits it to a particular order. Based on reviewing the following figures and detailed description, other features and advantages of the disclosed embodiments will be or will become apparent to those of ordinary skill in the art. It is intended that all such additional features and advantages be included within the scope of the disclosed embodiments. In addition, the figures shown are illustrative only and are not intended to confirm or imply any limitation on the environment, architecture, design, or procedure in which different embodiments may be implemented. With respect to the temperatures and pressures mentioned in the following description, these conditions are illustrative only and are not meant to limit the present invention. Accordingly, the systems and methods disclosed herein improve the conventional two-stage cooling cycle by using an ejector as the power in the cooling loop to regeneratively subcool the refrigerant in a single-stage cooling cycle. The systems and methods disclosed herein achieve the same or higher energy efficiency as the conventional two-stage cooling cycle but with fewer devices since a second stage is not required to achieve the subcooling effect. The single-stage cooling cycle disclosed herein also does not require a high entrainment ratio ejector, which reduces the compression ratio and improves the energy efficiency of the cooling cycle. In one embodiment, the present invention includes a system for a single-stage cooling cycle, the system comprising: i) a single refrigerant; ii) an ejector for mixing a condensed liquid form of the single refrigerant and a first vaporized form of the single refrigerant to form a two-phase form of the single refrigerant; iii) a flash economizer fluidly connected to the ejector for separating the two-phase form of the single refrigerant from the ejector into a second vaporized form of the single refrigerant and a liquid form of the single refrigerant; iv) an expansion valve fluidly connected to the flash economizer for converting a portion of the liquid form of the single refrigerant into an expanded two-phase form of the single refrigerant; and v) a subcooler fluidly connected to the expansion valve for cooling another portion of the liquid form of the single refrigerant by transferring heat from the another portion of the liquid form of the single refrigerant to the expanded two-phase form of the single refrigerant, and generating the first vaporized form of the single refrigerant and a separately subcooled liquid form of the single refrigerant. In another embodiment, the present invention includes a single-stage cooling method, the method comprising: i) mixing a condensate liquid form of a single refrigerant and a first vaporized form of the single refrigerant to form a two-phase form of the single refrigerant; ii) separating the two-phase form of the single refrigerant into a second vaporized form of the single refrigerant and a liquid form of the single refrigerant; iii) converting a portion of the liquid form of the single refrigerant into an expanded two-phase form of the single refrigerant; and iv) cooling another portion of the liquid form of the single refrigerant by transferring heat from the another portion of the liquid form of the single refrigerant to the expanded two-phase form of the single refrigerant, and generating the first vaporized form of the single refrigerant and a separate subcooled liquid form of the single refrigerant. In some embodiments, the temperature and pressure of the second vaporized form of the single refrigerant can be about 72°F and about 89 psia, respectively. The temperature and pressure of the liquid form of the single refrigerant can be about 95°F and about 129 psia, respectively. The temperature and pressure of the separate subcooled liquid form of the single refrigerant can be about 68°F and about 88 psia, respectively. The temperature and pressure of the two-phase form of the single refrigerant can be about 72°F and about 89 psia, respectively. The temperature and pressure of the first vaporized form of the single refrigerant can be about 60°F and about 72 psia, respectively. Referring now to FIG. 2, there is shown an embodiment of a system 200 for a single-stage regenerative ejector-based cooling cycle with a single refrigerant. An exemplary refrigerant is an R-134A refrigerant with a cooling load of 5.4 MW for cooling a circulating cooling water system from 30°C (86°F) to 22°C (72°F), although other refrigerants can be used. Vapor refrigerant enters compressor 204 from first vaporized refrigerant line 202 and is compressed to a pressure of 114 psig and a temperature of 107°F. The compressed vapor refrigerant passes through compressed refrigerant line 206 to a heat exchanger known as evaporative condenser 208. The condensed liquid refrigerant passes through condensed refrigerant line 210 at a temperature of 95°F to ejector 214 with the help of pump 207. Due to the flexibility provided by pump 207 and ejector 214, system 200 can achieve a higher coefficient of performance and lower energy consumption than conventional systems. Thus, pump 207 is capable of achieving a higher discharge pressure at ejector 214 and a higher intermediate pressure at flash economizer 212. Optionally, pump 207 can be removed based on capital cost, maintenance considerations, and / or system limitations. The condensed liquid refrigerant enters the ejector 214 as the motive fluid, mixes with the evaporating refrigerant from the second evaporating refrigerant line 226 in the ejector 214, and is ejected from the ejector 214 as a two-phase refrigerant. The motive fluid will always be liquid as it is directly positioned downstream of the evaporative condenser 208. The two-phase refrigerant passes through the two-phase refrigerant line 216 to the flash economizer 212, where it is flashed into vapor refrigerant and liquid refrigerant. A regulating valve may be used for operating flexibility, as appropriate. The vapor refrigerant from the flash economizer 212 enters the compressor 204 through the first evaporating refrigerant line 202. The liquid refrigerant from the flash economizer 212 passes through the liquid refrigerant line 220 to the pump 222. For smaller cooling cycles, as appropriate, the flash economizer 212 and the pump 222 may be unnecessary and are thus removed. The liquid refrigerant is pumped to the expansion valve 223 and / or the subcooler 224 based on a control valve (not shown). The liquid refrigerant expands as it passes through the expansion valve 223. The expanded two-phase refrigerant passes through the expanded refrigerant line 225 to the subcooler 224, where it is thermally evaporated and used to cool the liquid refrigerant from the pump 222. The evaporated refrigerant from the subcooler 224 passes through the second evaporating refrigerant line 226 to the ejector 214. The subcooled liquid refrigerant from the subcooler 224 passes through the subcooled refrigerant line 228 to the evaporator 230, where it is thermally evaporated into evaporating refrigerant, which passes through the third evaporating refrigerant line 232 to the flash economizer 212, and is finally recycled back to the compressor 204 through the first evaporating refrigerant line 202 in the flash economizer 212. System 200 requires a single refrigerant and thus requires fewer components than the conventional system 100 for a two-stage ejector-based cooling cycle, which is less economical and efficient in cooling. Table A shows the correspondence between the generic terms herein and the specific terms used in the embodiment of FIG. 2. Table A The pressure-enthalpy diagram in FIG. 3 compares the expected pressure / enthalpy values at the state points of the system 200 shown in FIG. 2 and a conventional four (4)-component cooling cycle. The dashed lines connect the state points of the system 200, and the dashed / dotted lines connect the state points of the conventional 4-component cooling cycle. The bubble point curve represents the line above which the refrigerant is liquid. The dew point curve represents the line above which the refrigerant is vapor. In FIG. 4, the system 200 in FIG. 2 replaces the component symbols with corresponding state points in FIG. 3. Importantly, the transition of the refrigerant from state point 040 to state point 010 through the subcooler 224 helps to achieve a higher inlet pressure of the compressor 204 at state point 001 and a subsequent reduction in the pressure difference between state points 001 and 002. Comparing state point 0010 of the system 200 with state point 008 in the conventional 4-component cycle shown in FIG. 3, it shows that a single refrigerant in the system 200 achieves the same cooling temperature as the conventional 4-component cycle while operating at a higher pressure than the conventional 4-component cycle, which reduces the compression energy. Table 1 below uses a simulation model (Aspen HYSYS version 12.1) to compare the expected performance of the conventional 4-component cooling cycle and the cooling cycle based on a single-stage regenerative ejector shown in FIG. 2 with the projected ejector performance. As shown in the expected results, the cooling cycle based on a single-stage regenerative ejector shown in FIG. 2 will produce a higher coefficient of performance with a smaller compression power. The system 200 in FIG. 2 can be combined with another cooling cycle based on a single-stage regenerative ejector. As shown in FIG. 2, by replacing the evaporator 230 in one cooling cycle and the evaporative condenser 208 in other cooling cycles with the single-stage cascade exchanger 502 shown in FIG. 5, cooling can be achieved at a lower temperature, for example, in cryogenic applications using independent refrigerants. The present disclosure provides the following embodiments: [Item 1] A system for a single-stage cooling cycle, comprising: a single refrigerant; an injector for mixing a condensed liquid form of the single refrigerant and a first vaporized form of the single refrigerant to form a two-phase form of the single refrigerant; a flash economizer fluidly connected to the injector for separating the two-phase form of the single refrigerant from the injector into a second vaporized form of the single refrigerant and a liquid form of the single refrigerant; an expansion valve fluidly connected to the flash economizer for converting a portion of the liquid form of the single refrigerant into an expanded two-phase form of the single refrigerant; and a subcooler fluidly connected to the expansion valve for cooling another portion of the liquid form of the single refrigerant by transferring heat from the another portion of the liquid form of the single refrigerant to the expanded two-phase form of the single refrigerant, and generating the first vaporized form of the single refrigerant and a separate subcooled liquid form of the single refrigerant. [Item 2] The system of Item 1, further comprising a pump positioned between the flash economizer and the subcooler for distributing the liquid form of the single refrigerant. [Item 3] The system of Item 1, further comprising an evaporator fluidly connected to the subcooler for heating the subcooled liquid form of the single refrigerant by transferring heat from an external source to the subcooled liquid form of the single refrigerant, and generating a third vaporized form of the single refrigerant. [Item 4] The system of Item 3, wherein the flash economizer is connected to the evaporator for receiving the third vaporized form of the single refrigerant. [Item 5] The system of Item 1, further comprising a compressor fluidly connected to the flash economizer for compressing the second vaporized form of the single refrigerant. [Item 6] The system of Item 1, further comprising a pump positioned upstream of the injector for increasing at least one of the discharge pressure at the injector and the intermediate pressure at the flash economizer. [Item 7] The system of Item 1, wherein the temperature and pressure of the second vaporized form of the single refrigerant are approximately 72˚F and approximately 89 psia, respectively. [Item 8] The system of Item 1, wherein the temperature and pressure of the liquid form of the single refrigerant are approximately 95˚F and approximately 129 psia, respectively. [Item 9] The system of Item 1, wherein the temperature and pressure of the subcooled liquid form of the single refrigerant are approximately 68˚F and approximately 88 psia, respectively. [Item 10] The system of Item 1, wherein the temperature and pressure of the two-phase form of the single refrigerant are approximately 72˚F and approximately 89 psia, respectively.[Item 11] A single-stage cooling method, comprising: mixing a condensate liquid form of a single refrigerant and a first evaporation form of the single refrigerant to form a two-phase form of the single refrigerant; separating the two-phase form of the single refrigerant into a second evaporation form of the single refrigerant and a liquid form of the single refrigerant; converting a part of the liquid form of the single refrigerant into an expanded two-phase form of the single refrigerant; and cooling the other part of the liquid form of the single refrigerant by transferring heat from the other part of the liquid form of the single refrigerant to the expanded two-phase form of the single refrigerant, and generating the first evaporation form of the single refrigerant and a separate subcooled liquid form of the single refrigerant. [Item 12] The method according to Item 11, further comprising heating the subcooled liquid form of the single refrigerant by transferring heat from an external source to the subcooled liquid form of the single refrigerant, and generating a third evaporation form of the single refrigerant. [Item 13] The method according to Item 11, further comprising compressing the second evaporation form of the single refrigerant. [Item 14] The method according to Item 11, further comprising increasing at least one of the discharge pressure at the ejector and the intermediate pressure at the flash economizer with a pump. [Item 15] The method according to Item 11, wherein the temperature and pressure of the second evaporation form of the single refrigerant are about 72°F and about 89 psia, respectively. [Item 16] The method according to Item 11, wherein the temperature and pressure of the liquid form of the single refrigerant are about 95°F and about 129 psia, respectively. [Item 17] The method according to Item 11, wherein the temperature and pressure of the subcooled liquid form of the single refrigerant are about 68°F and about 88 psia, respectively. [Item 18] The method according to Item 11, wherein the temperature and pressure of the two-phase form of the single refrigerant are about 72°F and about 89 psia, respectively. [Item 19] The method according to Item 11, wherein the temperature and pressure of the first evaporation form of the single refrigerant are about 60°F and about 72 psia, respectively. [Item 20] The method according to Item 11, wherein the single refrigerant is a refrigerant with a cooling load of 5.4 MW, used to cool a circulating cooling water system from about 86°F to about 72°F. Although the present invention has been described in connection with the presently preferred embodiments, those skilled in the art will understand that it is not intended to limit the present invention to these embodiments. According to the invention herein, existing ejector-based cooling cycles can be retrofitted or modified, and can also be implemented in any other refrigeration process employed in a closed structure for heating or cooling to achieve similar results. Therefore, it is contemplated that various alternative embodiments and modifications can be made to the disclosed embodiments without departing from the spirit and scope of the present invention as defined by the appended patent claims and their equivalents. 001, 002, 008, 0010, 040: State point 100: System 102: First refrigerant pipeline 104: Compressor 106: First refrigerant pipeline 107: First expansion valve 108: Evaporative condenser 110: Condensed refrigerant pipeline 112: Flash economizer 114: Injector 116: First refrigerant pipeline 118: First refrigerant pipeline 120: First refrigerant pipeline 121: Second expansion valve 122: First refrigerant pipeline 124: Subcooler 126: First refrigerant pipeline 128: Second refrigerant pipeline 130: Second refrigerant pipeline 132: Cascade exchanger 134: Second refrigerant pipeline 135: Second refrigerant pipeline 136: Second compressor 138: Third expansion valve 139: Second refrigerant pipeline 140: Evaporator 200: System 202: First evaporative refrigerant pipeline 204: Compressor 206: Compressed refrigerant pipeline 207: Pump 208: Evaporative condenser 210: Condensed refrigerant pipeline 212: Flash economizer 214: Injector 216: Two-phase refrigerant pipeline 220: Liquid refrigerant pipeline 222: Pump 223: Expansion valve 224: Subcooler 225: Expanded refrigerant pipeline 226: Second evaporative refrigerant pipeline 228: Subcooled refrigerant pipeline 230: Evaporator 232: Third evaporative refrigerant pipeline 502: Single cascade exchanger The following detailed description is described with reference to the accompanying drawings, in which like elements are referred to by like reference numerals, wherein: FIG. 1 is a schematic diagram illustrating a system for a conventional two-stage ejector-based cooling cycle. FIG. 2 is a schematic diagram illustrating an embodiment of a system for a single-stage regenerative ejector-based cooling cycle. FIG. 3 is a pressure-enthalpy diagram comparing the expected pressure / enthalpy values at state points of the system illustrated in FIG. 2 and a conventional four (4)-component cooling cycle. FIG. 4 is a schematic diagram of the system of FIG. 2, wherein the component symbols are replaced by the corresponding state points in FIG. 3. FIG. 5 is a schematic diagram illustrating an embodiment of a system for two combined single-stage regenerative ejector-based cooling cycles. 200: System 202: First evaporative refrigerant pipeline 204: Compressor 206: Compressed refrigerant pipeline 207: Pump 208: Evaporative condenser 210: Condensed refrigerant pipeline 212: Flash economizer 214: Injector 216: Two-phase refrigerant pipeline 220: Liquid refrigerant pipeline 222: Pump 223: Expansion valve 224: Subcooler 225: Expanded refrigerant pipeline 226: Second evaporative refrigerant pipeline 228: Subcooled refrigerant pipeline 230: Evaporator 232: Third evaporative refrigerant pipeline

Claims

1. A system for regenerating a cooling cycle, comprising: refrigerant; An ejector for mixing the condensed liquid form and the first evaporating form of the refrigerant to form a two-phase form of the refrigerant; a flash economizer fluidly connected to the ejector for separating the two-phase form of the refrigerant from the ejector into a second evaporating form and a liquid form of the refrigerant; an expansion valve located between a liquid refrigerant line connected to the flash economizer and a subcooler for converting a portion of the liquid form of the refrigerant from the liquid refrigerant line into an expanded two-phase form of the refrigerant, the subcooler being fluidly connected to the expansion valve; and an evaporator fluidly connected to the subcooler for heating the individual subcooled liquid form of the refrigerant by transferring heat from an external source to the individual subcooled liquid form of the refrigerant, and generating a third evaporating form of the refrigerant, wherein the flash economizer is connected to the evaporator for receiving the third evaporating form of the refrigerant.

2. The system of claim 1, further comprising a pump located between the flash economizer and the subcooler for distributing the liquid form of the refrigerant.

3. The system of claim 1, further comprising a compressor connected to the flash economizer for compressing the second evaporative form of the refrigerant.

4. The system of claim 1, further comprising a pump located upstream of the injector for increasing at least one of the discharge pressure at the injector and the intermediate pressure at the flash economizer.

5. As in request item 1, where, The temperature and pressure of the second evaporation form of the refrigerant are approximately 72˚F and approximately 89 psia, respectively.

6. As in request item 1, where, The temperature and pressure of the liquid form of the refrigerant are approximately 95˚F and approximately 129 psia, respectively.

7. As in request item 1, where, The temperature and pressure of the refrigerant in its individual subcooled liquid form are approximately 68˚F and approximately 88 psia, respectively.

8. As in request item 1, where, The temperature and pressure of the two phases of the refrigerant are approximately 72˚F and approximately 89 psia, respectively.

9. A regenerative cooling method, comprising: The refrigerant is mixed in its condensed liquid form and its first evaporated form to form a two-phase form. The refrigerant is separated into a second evaporating form and a liquid form by separating the two-phase form and the received third evaporating form of the refrigerant; a portion of the liquid form of the refrigerant is converted into an expanding two-phase form of the refrigerant; the other portion of the liquid form of the refrigerant is cooled by transferring heat from the other portion of the liquid form of the refrigerant to the expanding two-phase form of the refrigerant, thereby generating the first evaporating form of the refrigerant and a separate subcooled liquid form of the refrigerant; and the separate subcooled liquid form of the refrigerant is heated by transferring heat from an external source to the separate subcooled liquid form of the refrigerant, thereby generating the third evaporating form of the refrigerant.

10. The method of claim 9, further comprising compressing the second evaporation form of the refrigerant.

11. The method of claim 9, further comprising increasing the pressure of at least one of the condensed liquid form of the refrigerant and the liquid form of the refrigerant by using a pump.

12. As in request item 9, wherein, The temperature and pressure of the second evaporation form of the refrigerant are approximately 72˚F and approximately 89 psia, respectively.

13. As in request item 9, wherein, The temperature and pressure of the liquid form of the refrigerant are approximately 95˚F and approximately 129 psia, respectively.

14. As in request item 9, wherein, The temperature and pressure of the refrigerant in its individual subcooled liquid form are approximately 68˚F and approximately 88 psia, respectively.

15. As in request item 9, wherein, The temperature and pressure of the two phases of the refrigerant are approximately 72˚F and approximately 89 psia, respectively.

16. As in request item 9, wherein, The temperature and pressure of the first evaporation form of the refrigerant are approximately 60˚F and approximately 72 psia, respectively.

17. As in request item 9, wherein, The refrigerant has a cooling load of 5.4 MW when in use and is used to cool the circulating cooling water system from approximately 86˚F to approximately 72˚F.

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