Cascade refrigeration system

Abstract

The present disclosure is directed to various embodiments of a cascade refrigeration system (10). For example, an embodiment of the cascade refrigeration system (10) includes a high side refrigerant assembly (14), a low side refrigerant assembly (16), a first chiller (12a), and a second chiller (12b). The first chiller (12a) includes a first chiller evaporator (18a) shared between the high side refrigerant assembly (14) and the low side refrigerant assembly (16), and the second chiller (12b) includes a second chiller evaporator (18b) shared between the high side refrigerant (14) assembly and the low side refrigerant assembly (16).

Description

CASCADE REFRIGERATION SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application Serial No. 63 / 529,610, entitled “CASCADE REFRIGERATION SYSTEM,” filed July 28, 2023, which is incorporated herein by reference in its entirety for all purposes.BACKGROUND[0002| This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0003] Cascade refrigeration systems are becoming increasingly prevalent, namely, in industrial refrigeration applications. For example, cascade refrigeration systems generally employ a common heat exchanger shared between a low side refrigerant assembly and a high side refrigerant assembly. However, traditional systems and methods may be expensive, time consuming to build, and / or susceptible to failure due to leakage, such as leakage of a low side refrigerant of the low side refrigerant assembly into a high side refrigerant of the high side refrigerant assembly. Further, traditional systems and methods that attempt to address leakage concerns may have suboptimal efficiency. Accordingly, it is now recognized that improved systems and methods are desired.SUMMARY

[0004] A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended tolimit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

[0005] In an embodiment, a cascade refrigeration system includes a high side refrigerant assembly and a low side refrigerant assembly. The cascade refrigeration system also includes a first chiller having a first chiller evaporator shared between the high side refrigerant assembly and the low side refrigerant assembly. The cascade refrigeration system also includes second chiller having a second chiller evaporator shared between the high side refrigerant assembly and the low side refrigerant assembly.[0006| In another embodiment, a cascade refrigeration system includes a high side refrigerant assembly having a first chiller configured to circulate first ammonia and a second chiller configured to circulate second ammonia. The cascade refrigeration system also includes a low side refrigerant assembly configured to circulate carbon dioxide. The cascade refrigeration system also includes a first chiller evaporator shared between the low side refrigerant assembly and the first chiller of the high side refrigerant assembly such that the first chiller evaporator is configured to receive the carbon dioxide and the first ammonia. The cascade refrigeration system also includes a second chiller evaporator shared between the low side refrigerant assembly and the second chiller of the high side refrigerant assembly such that the second chiller evaporator is configured to receive the carbon dioxide and the second ammonia.

[0007] In another embodiment, a cascade refrigeration system includes a refrigerant assembly configured to circulate a first refrigerant. The cascade refrigeration system also includes a chiller configured to circulate a second refrigerant and having a chiller evaporator configured to interface the first refrigerant with the second refrigerant. The cascade refrigeration system also includes an additional chiller configured to circulate a third refrigerant and having an additional chiller evaporator configured to interface the first refrigerant with the third refrigerant. A first material composition of the first refrigerant differs from a second material composition of the second refrigerant and a third material composition of the third refrigerant. The second material composition of the second refrigerant is substantially the same as the third material composition of the third refrigerant.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:

[0009] FIG. 1 is a schematic illustration of a cascade refrigeration system employing a number of chillers, such as multi-temperature hydronic system (MTHS) enabled chillers, in a high side refrigerant assembly of the cascade refrigeration system, in accordance with an aspect of the present disclosure;

[0010] FIG. 2 is a schematic illustration of a portion of the cascade refrigeration system of FIG. 1 including a multi-temperature hydronic system (MTHS) skid, in accordance with an aspect of the present disclosure;

[0011] FIG. 3 is a perspective view of a portion (e.g., a chiller) of the cascade refrigeration system of FIG. 1, in accordance with an aspect of the present disclosure; and

[0012] FIG. 4 is a process flow diagram of a method of operating the cascade refrigeration system of FIG. 1, in accordance with an aspect of the present disclosure.DETAILED DESCRIPTION

[0013] One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vaiy from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinaiy skill having the benefit of this disclosure.

[0014] When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intendedto be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be noted that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0015] As used herein, the terms “approximately,” “generally,” “substantially,” and so forth, are intended to convey that the property value being described may be within a relatively small range of the property value, as those of ordinary skill would understand. For example, when a property value is described as being “approximately” equal to (or, for example, “substantially similar” to) a given value, this is intended to convey that the property value may be within + / - 5%, within + / - 4%, within + / - 3%, within + / - 2%, within + / - 1%, or even closer, of the given value. Similarly, when a given feature is described as being “substantially parallel” to another feature, “generally perpen icular” to another feature, and so forth, this is intended to convey that the given feature is within + / - 5%, within + / - 4%, within + / - 3%, within + / - 2%, within + / - 1%, or even closer, to having the described nature, such as being parallel to another feature, being perpendicular to another feature, and so forth. Mathematical terms, such as “parallel” and “perpendicular,” should not be rigidly interpreted in a strict mathematical sense, but should instead be interpreted as one of ordinary skill in the art would interpret such terms. For example, one of ordinary skill in the art would understand that two lines that are substantially parallel to each other are parallel to a substantial degree, but may have minor deviation from exactly parallel.

[0016] Embodiments of the present disclosure relate to cascade refrigeration systems. For example, a cascade refrigeration system may include a high side refrigerant assembly employing a number of chillers, such as multi-temperature hydronic system (MTHS) enabled chillers. In some embodiments, the chillers of the high side refrigerant assembly may be fluidly separate from one another and / or disposed in parallel (e.g., with respect to one or more fluid flows described below).

[0017] For example, a first chiller may define a first high side refrigerant (e.g., ammonia) loop, and a second chiller may define a second high side refrigerant (e.g., ammonia) loop fluidly separate from the first high side refrigerant (e.g., ammonia) loop. The cascade refrigeration system also includes a low side refrigerant assembly. Evaporators of the chillers may be shared between the high side refrigerant assemblyand the low side refrigerant assembly. For example, unlike configurations that employ sensible cooling, the evaporators of the chillers may be employed to directly condense a low side refrigerant (e.g., carbon dioxide) of the low side refrigerant assembly via the high side refrigerant (e.g., ammonia) of the high side refrigerant assembly. The first and second chillers may be disposed in parallel, for example, with respect to a flow of the low side refrigerant (e.g., carbon dioxide). While certain embodiments of the present disclosure are described with respect to carbon dioxide corresponding to the low side refrigerant and ammonia corresponding to the high side refrigerant, other types of refrigerants are also possible. In general, the high side refrigerant includes a material composition that differs from the low side refrigerant.

[0018] By maintaining fluidly separate high side refrigerant loops in the chillers, in the event leakage of the low side refrigerant (e.g., carbon dioxide) occurs at one of the evaporators of the chillers, only the chiller having the leak is affected. In other words, while leakage at one evaporator may affect the chiller corresponding to the one evaporator, the other chillers of the high side refrigerant assembly are not affected and can remain on-line.

[0019] Further, the cascade refrigeration system may employ one or more glycol loops and / or multi-temperature hydronic system (MTHS) features for condenser cooling of the chillers, oil cooling of the chillers, or both. Further still, the cascade refrigeration system may employ new control strategies to minimize or potentially eliminate the need for continuous bleeding and chemical water treatment of a spray water circuit of an evaporative fluid cooler. The above-described features generally improve a capacity, safety, resiliency, cost, and / or redundancy of the cascade refrigeration system, while also enabling the use of ammonia and carbon dioxide as the high side and low side refrigerants, respectively, without employing an intermediate glycol loop that other configurations may employ to reduce an impact of leakage at the cost of energy penalty. These and other features in accordance with the present disclosure are described in detail below with reference to the drawings.

[0020] FIG. 1 is a schematic illustration of an embodiment of a cascade refrigeration system 10 employing a number of chillers 12a, 12b, 12n, such as multitemperature hydronic system (MTHS) enabled chillers, in a high side refrigerant assembly 14 of the cascade refrigeration system 10. For example, the high siderefrigerant assembly 14 in the illustrated embodiment employs multiple portions of fluidly separate high side refrigerant (e.g., ammonia) to directly condense a low side refrigerant (e.g., carbon dioxide) associated with a low side refrigerant assembly 16 of the cascade refrigeration system 10. While other refrigerants may be used, the description below refers to the high side refrigerant as ammonia and the low side refrigerant as carbon dioxide.

[0021] As shown, the first chiller 12a includes a first evaporator 18a (e.g., first chiller evaporator), a first compressor 20a, a first condenser 22a, and a first expansion valve 24a. The first evaporator 18a of the first chiller 12a is configured to receive a first portion of ammonia and a first portion of carbon dioxide to interface the first portion of ammonia with the first portion of carbon dioxide. That is, the first evaporator 18a is configured to directly condense the first portion of carbon dioxide via the first portion of ammonia, as opposed to sensible cooling techniques. Likewise, the second chiller 12b includes a second evaporator 18b (e.g., second chiller evaporator), a second compressor 20b, a second condenser 22b, and a second expansion valve 24b. The second evaporator 18b of the second chiller 12b is configured to receive a second portion of ammonia and a second portion of carbon dioxide to interface the second portion of ammonia with the second portion of carbon dioxide. That is, the second evaporator 18b is configured to directly condense the second portion of carbon dioxide via the second portion of ammonia, as opposed to sensible cooling techniques. As described in greater detail with reference to FIG. 2, one or more glycol loops and / or multi-temperature hydronic system (MHTS) features may be employed for heat rejection and cooling of certain aspects of the chillers 12a, 12b, 12n, such as the condensers 22a, 22b, 22n and / or componentry corresponding to oil (e.g., lubricating oil) employed in the chillers 12a, 12b, 12n. Further, any number “n” of chillers may be employed in FIG. 1. For example, “n” may be 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. In general, the chillers 12a, 12b, 12n may be pre-engineered, factory-build and tested, with direct carbon dioxide condensing evaporators 18a, 18b, 18n and plate type condensers 22a, 22b, 22n.

[0022] As shown, the evaporators 18a, 18b, 18n (e.g., chiller evaporators) are arranged in parallel with respect to a flow of the carbon dioxide in the low side refrigerant assembly 16. Further, the portions of ammonia corresponding to the chillers12a, 12b, 12n may be fluidly separate from one another. In other words, the ammonia charge is divided between the chillers 12a, 12b, 12n. That is, ammonia is not distributed from one of the chillers, such as the first chiller 12a, to another of the chillers, such as the second chiller 12b. In this way, if a leak occurs, such as a leak in the first evaporator 18a of the first chiller 12a, only the first chiller 12 is affected. That is, while a leak in the first evaporator 18a may cause carbon dioxide to rise into the high side refrigerant assembly 14 and mix with the first portion of ammonia in the first chiller 12a (e.g., due to a relatively high pressure of the carbon dioxide), the other chillers 12b, 12n of the high side refrigerant assembly 14 and their corresponding portions of ammonia are unaffected.

[0023] As shown, the first chiller 12a includes a high side inlet 26a to the evaporator 18a and a high side outlet 28a from the evaporator 18a. Further, the first chiller 12a includes a low side inlet 30a to the evaporator 18a and a low side outlet 32a from the evaporator 18a. The other chillers 12b, 12n include the same or similar arrangements. As shown, fluid pathways 34a, 34b, 34n from the low side outlets 32a, 32b, 32n are employed to guide the carbon dioxide from the evaporators 18a, 18b, 18c to a first economizer 35 (e.g., medium temperature [MT] economizer). In some embodiments, a common pathway 36 of respective segments of the fluid pathways 34a, 34b, 34n is employed to couple to the first economizer 35. Further, the fluid pathways 34a, 34b, 34n may include respective liquid float valves 38a, 38b, 38n, as shown, configured to control various aspects of the flow of carbon dioxide toward the first economizer 35.

[0024] The following discussion refers to various portions of the low side refrigerant, or carbon dioxide. It should be understood that reference to the portions of carbon dioxide should not be interpreted as meaning the portions are not in fluid communication with each other. Instead, reference to various portions of carbon dioxide (e.g., first, second, third, fourth, fifth, sixth, seventh, first compressed, second compressed, first return, and second return portions of carbon dioxide) is employed to clearly delineate flow directions and / or flow relationships between various componentry of the low side refrigerant assembly 16. Indeed, the low side refrigerant assembly 16 may be a closed- loop refrigerant circuit that handles a single charge of low side refrigerant (e.g., carbon dioxide).

[0025] The low side refrigerant assembly 16 includes the first economizer 35, as previously described, a first compressor 40 (e.g., MT compressor), a first accumulator 42 (e.g., MT accumulator), a second economizer 44 (e.g., low temperature [LT] economizer), a second compressor 46 (e.g., LT compressor), and a second accumulator 48 (e.g., LT accumulator), as shown. The first economizer 35 may be configured to direct a first portion 50 of carbon dioxide to the economizer port of the first compressor 40 and a second portion 52 of carbon dioxide toward, for example, a first load 54 (e.g., MT evaporator) and / or the first accumulator 42. Valves 56, 58 may be employed between to control carbon dioxide flow between the first accumulator 42 and the first load 54. The first load 54 may be configured to direct a first return portion 59 of carbon dioxide to the first accumulator 42, as shown. The first compressor 40 is configured to receive the first portion 50 of carbon dioxide from the first economizer 35 and a third portion 60 of carbon dioxide from the first accumulator 42, and to output a first compressed portion 62 of carbon dioxide toward the chillers 12a, 12b, 12n. In some embodiments, a header 64 may be employed to distribute the first compressed portion 62 of carbon dioxide to the evaporators 18a, 18b, 18n of the chillers 12a, 12b, 12n, respectively (e.g., in a parallel arrangement).

[0026] As previously described, the first accumulator 42 is configured to receive the return portion 59 of carbon dioxide from the first load 54 and output the third portion 60 of carbon dioxide to the first compressor 40. As shown, the first accumulator is also configured to output a fourth portion 66 of carbon dioxide toward the second economizer 44. In some embodiments, a valve 68 may be employed to control a flow of the fourth portion 66 of carbon dioxide between the first accumulator 42 and the second economizer 44. The second economizer 44 is also configured to output a fifth portion 70 of carbon dioxide toward the economizer port of the second compressor 46 and a sixth portion 72 of carbon dioxide toward a second load 74 (e.g., LT evaporator). In some embodiments, a valve 76 is employed to control a flow of the sixth portion 72 of carbon dioxide between second economizer 44 and the second load 74. The second load 74 is configured to output a second return portion 78 of carbon dioxide toward the second accumulator 48, which outputs a seventh portion 80 of carbon dioxide to the second compressor 46. The second compressor 46 is configured to direct a second compressed portion 82 of carbon dioxide to the first accumulator 42, as shown.

[0027] FIG. 2 is a schematic illustration of an embodiment of a portion of the cascade refrigeration system 10 of FIG. 1 including and / or employing a multitemperature hydronic system (MTHS) skid 100. In some embodiments, the MTHS skid 100 is considered a part of the cascade refrigeration system 10 and is employed for purposes of heat rejection, as described below. As shown, the high side refrigerant assembly 14 of the cascade refrigeration system 10 includes the chillers 12a, 12b, 12c, 12n, etc. The first chiller 12a in the illustrated embodiment includes the condenser 22a and an oil cooler 101a, although it should be understood that the other chillers 12b, 12c, 12n also include their own instances of such componentry.

[0028] As shown, a first distribution assembly 102 may be employed to distribute a fluid, such as glycol, from the MTHS skid 100 to the condensers of the chillers 12a, 12b, 12c, 12n (e.g., the condenser 22a of the first chiller 12a), and to return the fluid, such as glycol, from the condensers of the chillers 12a, 12b, 12c, 12n (e.g., the condenser 22a of the first chiller 12a) to the MTHS skid 100. A first pump 103 may be employed to bias the fluid, such as glycol, through the first distribution assembly 102. Further, a second distribution assembly 104 may be employed to distribute a fluid, such as glycol, from the MTHS skid 100 to the oil coolers of the chillers 12a, 12b, 12c, 12n (e.g., the oil cooler 101a of the first chiller 12a) and to return the fluid, such as glycol, from the oil coolers of the chillers 12a, 12b, 12c, 12n to the MTHS skid 100. A second pump 105 may be employed to bias the fluid, such as glycol, through the second distribution assembly 104.

[0029] In some embodiments, separation of the fluid corresponding to the first distribution assembly 102 and the fluid corresponding to the second distribution assembly 104 may be maintained in all or parts of the system 10. For example, a first glycol loop corresponding to the first distribution assembly 102 may be employed and a second glycol loop corresponding to the second distribution assembly 104 may be employed, where the first and second glycol loops interact with the MTHS skid 100 (e.g., at different temperatures). Example features of the MTHS skid 100 and other aspects of the system 10 (e.g., heat rejection, recapture, reclaiming features, described in detail below) can be found in U.S. Publication No. 20220316733, which is incorporated by reference herein.

[0030] Selective heat rejection, recapture, and / or reclaiming features may be employed in accordance with the present disclosure. As shown, for example, the MTHS skid 100 may be fluidly coupled with an expansion tank 106, an evaporative fluid cooler 108, a dry cooler 110, and / or a heat recovery heat exchanger 112. Depending on operating, ambient, and / or load conditions, among other possible factors, the system 10 may be controlled to selectively bias the fluid(s) (e.g., glycol) described above toward the expansion tank 106, the evaporative fluid cooler 108, the dry cooler 110, and / or the heat recovery heat exchanger 112. In general, the expansion tank 106 is employed to accommodate changes in liquid volume as liquid temperature changes, whereas the evaporative fluid cooler 108, the dry cooler 110, and / or the heat recovery heat exchanger 112 are selectively employed as heat rejection devices. For example, a controller 114 (or control assembly) includes processing circuitry 116 and memoiy circuitry 118, the memory circuitry 118 storing instructions thereon that, when executed by the processing circuitry 116, cause the processing circuitiy 116 to perform various functions. As an example, the controller 114 may receive one or more inputs 120 (e.g., indicative of one or more operating, ambient, and / or load conditions). Based on the one or more inputs 120, the controller 114 may control various aspects of the system 10 (e.g., the pumps 103, 105, valves associated with the first distribution assemblyl02, valves associated with the second distribution assembly 104, fans, etc.) to direct, change, block, enable, or otherwise control fluid flows through the system 10.

[0031] As an example control feature, the controller 114 may control the evaporative fluid cooler 108 make-up and drain valves to drain a sump of the evaporative fluid cooler 108 and piping of spray water when ambient temperatures approach or fall below freezing conditions. Additionally or alternatively, the dry cooler 110 may be sized to handle the entire heat rejection load when the ambient temperature is above freezing. Additionally or alternatively, when a pan of the evaporative fluid cooler 108 is drained, the evaporative fluid cooler 108 may provide additional capacity through dry operation. The controller 114 may independently control a fan speed of the diy cooler 110 to provide the lowest combined fan and pump energy. Additionally or alternatively, as ambient temperature rises sufficiently above freezing yet still below the switch point of the dry cooler 110, the controller 114 will stop fans of the evaporative fluid cooler 108 and the fan speed on the dry cooler 110 will increase to compensate. The controller 114 may then control the make-up and drain valves againto fill the sump of the evaporative fluid cooler 108 so that it is ready to operate as temperatures rise above the switch point of the dry cooler 110.

[0032] In accordance with the present disclosure, the controller 114 may also operate to address issues associated with traditionally having to provide a continuous bleed of the spray water circuit of the evaporative fluid cooler 108 and the addition of chemicals to provide scale and biological control of the spray water circuit. In accordance with the present disclosure, neither a continuous bleed nor chemical water treatment is needed. Instead, the controller 114 may operate valves, fans, spray water pumps, and compressors to allow the piping and sump of the evaporative fluid cooler 108 to be completely flushed each day and then refilled with clean water. This daily flush and refill of the spray water circuit will consume less water than the traditional continuous bleed and negate the need to add chemical water treatment since the water will only be in use for less than 24 hours.

[0033] The above-described control strategy may include, for example, turning off the spray waterpumps of the evaporative fluid cooler 108, shutting the make-up supply valve of the evaporative fluid cooler 108, and opening the pan drain valve of the evaporative fluid cooler 108 when the coldest dry bulb temperature occurs each day (e.g., at 5 AM). The fans of the evaporative fluid cooler 108 may be operated and the glycol may continue running through the coils of the evaporative fluid cooler 108. After a predetermined period of time, such as 30 minutes, the fan of the evaporative fluid cooler 108 may be turned off, the pan drain valve closed, and the make-up supply valve opened such that the pan is refilled. When the pan is full, the evaporative fluid cooler 108 may be brought back into service via instruction by the controller 114. The compressors of the chillers 12a, 12b, 12c, 12n and the low side compressors 40, 46 may be automatically offloaded, as necessary, to maintain the condensing pressures below the maximum with only the heat recovery heat exchanger 112 and the dry cooler 110 acting as heat rejection devices.

[0034] FIG. 3 is a perspective view of an embodiment of a portion of the cascade refrigeration system 10 (or portion thereof) of FIG. 1. For example, the first chiller 12a of the cascade refrigeration system 10 is illustrated in FIG. 1 . As shown, the first chiller 12a includes the evaporator 18a configured to directly condense a carbon dioxide of a low side refrigeration assembly of the refrigeration system 10, the compressor 20a, thecondenser 22a, the oil cooler 101a, and a surge drum 130. As previously described, first distribution assembly 102 may be configured to direct glycol to and from the condenser 22a, the second distribution assembly 104 may be configured to direct glycol to and from the oil cooler 101a, and the first and second distribution assemblies 102, 104 may be fluidly separate.

[0035] FIG. 4 is a process flow diagram of an embodiment of a method 200 of operating the cascade refrigeration system 10 of FIG. 1. In the illustrated embodiment, the method 200 includes operating (block 202) multiple chillers, each chiller having a separate high side refrigerant (e.g., ammonia) loop. For example, in a first chiller, a first portion of ammonia is directed through a first evaporator, a first compressor, a first condenser, and a first expansion valve. In a second chiller, a second portion of ammonia fluidly separate from the first portion of ammonia is directed through a second evaporator, a second compressor, a second condenser, and a second expansion valve.

[0036] The method 200 also includes operating (block 204) a low side refrigerant assembly to direct a low side refrigerant (e.g., carbon dioxide) through the evaporators of the chillers in the high side refrigerant assembly, such as the first evaporator and the second evaporator described above. As previously described, the first evaporator of the first chiller and the second evaporator of the second chiller are disposed in parallel with respect to a flow of the low side refrigerant (e.g., carbon dioxide). Thus, the first evaporator may receive a first portion of the low side refrigerant and the second evaporator may receive a second portion of the low side refrigerant.

[0037] The method 200 also includes directly condensing (block 206) the low side refrigerant (e.g., carbon dioxide) via the high side refrigerant (e.g., ammonia). For example, the first portion of the low side refrigerant may be directly condensed at the first evaporator via the first portion of ammonia corresponding to the first chiller, and the second portion of the low side refrigerant may be directly condensed at the second evaporator via the second portion of ammonia corresponding to the second chiller.

[0038] The method 200 also includes directing (block 208) a first portion of glycol between an MTHS skid and the condensers of the chillers via a first glycol distribution assembly, and directing (block 210) a second portion of glycol between the MTHS skid and oil coolers of the chillers via a second glycol distribution assembly. In someembodiments, a first portion of glycol corresponding to the first glycol distribution assembly may be fluidly separate from a second portion of glycol corresponding to the second glycol distribution assembly in all or part of the system.

[0039] The method 200 also includes rejecting (block 212) heat to various componentry of (or coupled to) the MTHS skid. For example, an evaporative fluid cooler, a dry cooler, a heat recovery heat exchanger, or any combination thereof may be employed to reject heat from the glycol prior to return of the glycol to the condensers and / or oil coolers of the chillers. Additionally or alternatively, an expansion tank may be employed to accommodate changes in liquid volume as liquid temperature changes.

[0040] Technical benefits of embodiments of the present disclosure include capacity, safety, resiliency, and / or redundancy of cascade refrigeration systems employing, for example, a high side refrigerant assembly employing a high side refrigerant (e.g., ammonia) and a low side refrigerant assembly employing a low side refrigerant (e.g., carbon dioxide).

[0041] While only certain features and embodiments of the disclosure have been illustrated and described, many modifications and changes may occur to those skilled in the art, such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, including temperatures and pressures, mounting arrangements, use of materials, colors, orientations, and so forth without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure.

[0042] Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described, such as those unrelated to the presently contemplated best mode of carrying out the disclosure, or those unrelated to enabling the claimed disclosure. It should be noted that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless bea routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.

[0043] The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function]...” or “step for [perform] ing [a function]...”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Claims

CLAIMSWhat is claimed is:

1. A cascade refrigeration system, comprising: a high side refrigerant assembly; a low side refrigerant assembly; a first chiller comprising a first chiller evaporator shared between the high side refrigerant assembly and the low side refrigerant assembly; and a second chiller comprising a second chiller evaporator shared between the high side refrigerant assembly and the low side refrigerant assembly.

2. The cascade refrigeration system of claim 1, wherein: the first chiller is configured to receive a first portion of a high side refrigerant; the second chiller is configured to receive a second portion of the high side refrigerant, the second portion being fluidly separate from the first portion; the low side refrigerant assembly is configured to receive a low side refrigerant having a material composition different than the high side refrigerant assembly; the first chiller evaporator is configured to directly condense the low side refrigerant via the first portion of the high side refrigerant; and the second chiller evaporator is configured to directly condense the low side refrigerant via the second portion of the high side refrigerant.

3. The cascade refrigeration system of claim 2, wherein the first chiller evaporator and the second chiller evaporator are disposed in parallel with respect to an input flow of the low side refrigerant.

4. The cascade refrigeration system of claim 2, comprising: a first valve disposed in a first fluid pathway between a first low side refrigerant output of the first chiller evaporator and an economizer of the low side refrigerant assembly; and a second valve disposed in a second fluid pathway between a second low side refrigerant output of the second chiller evaporator and the economizer.

5. The cascade refrigeration system of claim 4, comprising a common pathway shared between a first segment of the first fluid pathway and a second segment of the second fluid pathway, wherein the common pathway is coupled to the economizer.

6. The cascade refrigeration system of claim 1, wherein the lower side refrigerant assembly is configured to direct: a first portion of a low side refrigerant to a first load; and a second portion of the low side refrigerant to a second load different than the first load.

7. The cascade refrigeration system of claim 1, comprising a multi -temperature hydronic system (MTHS) skid fluidly coupled with a first condenser of the first chiller and a second condenser of the second chiller via a first distribution assembly.

8. The cascade refrigeration system of claim 7. wherein the MTHS skid is fluidly coupled with a first oil cooler of the first chiller and a second oil cooler of the second chiller via a second distribution assembly.

9. The cascade refrigeration system of claim 7, comprising an expansion tank fluidly coupled with the MTHS skid, an evaporative fluid cooler fluidly coupled with the MTHS skid, a dry cooler fluidly coupled with the MTHS skid, and a heat recovery heat exchanger fluidly coupled with the MTHS skid.

10. The cascade refrigeration system of claim 9, comprising a controller configured to: receive an input indicative of freezing ambient conditions; and automatically switch off the evaporative fluid cooler in response to receiving the input.

11. A cascade refrigeration system, comprising: a high side refrigerant assembly comprising a first chiller configured to circulate first ammonia and a second chiller configured to circulate second ammonia; a low side refrigerant assembly configured to circulate carbon dioxide;a first chiller evaporator shared between the low side refrigerant assembly and the first chiller of the high side refrigerant assembly such that the first chiller evaporator is configured to receive the carbon dioxide and the first ammonia; and a second chiller evaporator shared between the low side refrigerant assembly and the second chiller of the high side refrigerant assembly such that the second chiller evaporator is configured to receive the carbon dioxide and the second ammonia.

12. The cascade refrigeration system of claim 11, wherein the first chiller evaporator and the second chiller evaporator are disposed in parallel with respect to an input flow of the carbon dioxide.

13. The cascade refrigeration system of claim 1 1, comprising: a first valve disposed in a first fluid pathway between a first low side refrigerant output of the first chiller evaporator and an economizer of the low side refrigerant assembly; and a second valve disposed in a second fluid pathway between a second low side refrigerant output of the second chiller evaporator and the economizer.

14. The cascade refrigeration system of claim 13, comprising a common pathway shared between a first segment of the first fluid pathway and a second segment of the second fluid pathway, wherein the common pathway is coupled to the economizer.

15. The cascade refrigeration system of claim 11, wherein the lower side refrigerant assembly is configured to direct: a first portion of the carbon dioxide a first load; and a second portion of the carbon dioxide to a second load different than the first load.

16. The cascade refrigeration system of claim 1 1, comprising: a multi-temperature hydronic system (MTHS) skid fluidly coupled with a first condenser of the first chiller and a second condenser of the second chiller via a first distribution assembly, wherein the MTHS skid is fluidly coupled with a first oil coolerof the first chiller and a second oil cooler of the second chiller via a second distribution assembly; and an expansion tank fluidly coupled with the MTHS skid, an evaporative fluid cooler fluidly coupled with the MTHS skid, a dry cooler fluidly coupled with the MTHS skid, and a heat recovery heat exchanger fluidly coupled with the MTHS skid.

17. A cascade refrigeration system, comprising: a refrigerant assembly configured to circulate a first refrigerant; a chiller configured to circulate a second refrigerant and comprising a chiller evaporator configured to interface the first refrigerant with the second refrigerant; and an additional chiller configured to circulate a third refrigerant and comprising an additional chiller evaporator configured to interface the first refrigerant with the third refrigerant, wherein a first material composition of the first refrigerant differs from a second material composition of the second refrigerant and a third material composition of the third refrigerant, and the second material composition of the second refrigerant is substantially the same as the third material composition of the third refrigerant.

18. The cascade refrigeration system of claim 17, wherein: the first refrigerant corresponds to carbon dioxide; the second refrigerant corresponds to ammonia; and the third refrigerant corresponds to additional ammonia fluidly separate from the ammonia.

19. The cascade refrigeration system of claim 17, wherein the first chiller evaporator and the second chiller evaporator are disposed in parallel with respect to an input flow of the first refrigerant.

20. The cascade refrigeration system of claim 17, comprising: a first valve disposed in a first fluid pathway between a first refrigerant assembly output of the first chiller evaporator and an economizer of the refrigerant assembly; a second valve disposed in a second fluid pathway between a second refrigerant assembly output of the second chiller evaporator and the economizer; anda common pathway shared between a first segment of the first fluid pathway and a second segment of the second fluid pathway, wherein the common pathway is coupled to the economizer.

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