Refrigeration system with variable speed compressor and clustered expansion devices

Abstract

The present invention relates to an advanced refrigeration system designed to optimize the control of the working fluid's mass flow rate and pressure drop, thereby enhancing the overall efficiency and performance of low-temperature cooling applications. The system integrates a variable speed compressor, a cluster of fixed expansion devices, flow regulating valves, and an onboard control system to achieve precise temperature control and efficient operation. The variable speed compressor adjusts the mass flow rate of the working fluid, while the fixed expansion devices, arranged in series and parallel configurations, provide specific flow resistance. Flow regulating valves, controlled by the onboard control system, direct the working fluid through specific paths to achieve the desired flow rate and pressure drop. The control system continuously monitors the system's parameters and makes real-time adjustments to maintain optimal performance and uniform temperature control. The invention provides a more efficient and flexible refrigeration system capable of dynamically adjusting to varying operating conditions, minimizing inefficiencies, and maximizing the cooling effect. Figure 1

Description

FIELD OF THE INVENTIONThe present invention relates to the field of refrigeration and cooling systems,specifically to systems utilizing variable speed compressors in conjunction withmultiple fixed expansion devices and flow regulating valves to achieve optimalcontrol of the working fluid's mass flow rate and pressure drop. This invention isparticularly applicable to low-temperature cooling applications where precisetemperature control and efficient operation are critical.BACKGROUND OF THE INVENTION AND PRIOR ARTIn most low-temperature cooling applications, at least one throttling process is usedto generate the cooling effect. Devices used for such throttling effects, such ascapillary tubes, orifice valves, and needle valves, etc. provide constant flowresistance for given operating conditions. One of these operating parameters is themass flow rate of the working fluid. With the introduction of variable speedcompressors, uniform temperature control can be achieved by varying the massflow rate of the working fluid. However, for a fixed type of expansion device, theflow resistance varies with the change in mass flow rate across it. This inconsistencycan lead to inefficiencies and suboptimal performance in refrigeration systems.Problem StatementThe primary problem addressed by the present invention is the inability of fixedexpansion devices to provide consistent flow resistance when used with variablespeed compressors. This inconsistency affects the overall efficiency andperformance of the refrigeration system, making it difficult to achieve the desiredcooling effect and temperature control.Disadvantages of Prior Art1. In prior art CN205536643U, the aim is to regulate room temperature usinga variable speed compressor in conjunction with three capillary tubesconnected in parallel. The three capillary tubes are of different lengths andare controlled by a solenoid valve. However, this setup does not provide theflexibility to achieve optimal operating conditions for varying mass flowrates.2. In prior art CN109059411A, a Vapour Compression Refrigeration Cycle(VCRS) based on a Liquid-Vapour Heat Exchanger (LVHE) is disclosed.Here, after the condenser, the refrigerant is cooled in the LVHE beforeentering a multiway valve. The exit of this valve is connected to a cluster ofcapillary tubes. The refrigerant flow is governed based on the roomtemperature, which dictates the opening and closing of the multiway valve.This system lacks the ability to dynamically adjust the flow resistance forvarying mass flow rates, leading to inefficiencies.Technical SolutionThe proposed invention addresses these problems by using a cluster of fixedexpansion devices in conjunction with a control system and flow regulating valves.The key features of the invention include:1. A variable speed compressor that provides a variable mass flow rate of theworking fluid.2. A cluster of fixed expansion devices, such as capillary tubes, orifice valves,or needle valves, arranged in a combination of series and parallelconfigurations to achieve the desired pressure drop for any given flow rateof the working fluid.3. A plurality of flow regulating valves that control the flow of the workingfluid through the fixed expansion devices, allowing for precise control ofthe flow resistance.4. An onboard control system programmed to operate the flow regulatingvalves and adjust the speed of the variable speed compressor based on thecurrent state of the system. This ensures that the working fluid flows in aspecific pattern to achieve the desired flow rate and pressure drop,optimizing the performance of the refrigeration system.5. By implementing these features, the invention provides a more efficient andflexible refrigeration system capable of maintaining uniform temperaturecontrol and optimal performance under varying operating conditions.OBJECT OF THE INVENTIONThe primary objective of the present invention is to overcome the limitations ofprior art refrigeration systems by providing a more efficient and flexible solutionfor controlling the mass flow rate and pressure drop of the working fluid. Thespecific objectives of the invention include:1. To utilize a cluster of fixed expansion devices arranged in a combination of seriesand parallel configurations to achieve the desired pressure drop for any given flowrate of the working fluid.2. To implement a control system that operates flow regulating valves to direct theworking fluid through specific paths, thereby achieving the desired flow rate andpressure drop.3. To integrate a variable speed compressor that can adjust the mass flow rate of theworking fluid based on the current state of the system, ensuring uniformtemperature control and optimal performance.4. To provide a refrigeration system that can dynamically adjust to varyingoperating conditions, minimizing inefficiencies and maximizing the cooling effect.5. To enhance the overall performance and reliability of refrigeration systems usedin low-temperature cooling applications by incorporating advanced controlmechanisms and multiple expansion devices.SUMMARY OF THE INVENTIONThe summary of the invention provided herein is intended to give a brief overviewof the key features and aspects of the invention. It is not intended to be an exhaustiveor limiting description of the invention. The detailed description, claims, andaccompanying figures should be referred to for a complete understanding of theinvention and its various embodiments.The present invention provides an advanced refrigeration system designed tooptimize the control of the working fluid's mass flow rate and pressure drop, therebyenhancing the overall efficiency and performance of low-temperature coolingapplications. The system integrates a variable speed compressor, a cluster of fixedexpansion devices, flow regulating valves, and an onboard control system toachieve precise temperature control and efficient operation.The refrigeration system comprises a variable speed compressor (1, 3) thatcompresses the working fluid to a higher pressure. The compressed fluid is thencooled by aftercoolers (2, 4) to remove the heat of compression. Multiplecompressor-aftercooler pairs are used to achieve a higher pressure ratio withoutdamaging the compressor.Following the compression and cooling stages, the working fluid undergoes severalexpansion processes through a series of expansion valves (5, 6, 7, 8, 9). The flowof the working fluid through these expansion devices is governed by flow controlvalves (10, 11, 12, 13), which are operated by an onboard control system (15). Thecontrol system is programmed to adjust the flow regulating valves and the speed ofthe variable speed compressor based on the current state of the system, ensuring thedesired pressure drop and flow rate are achieved.The working fluid, after undergoing the expansion process, provides a coolingeffect in the evaporator (14). The control system (15) continuously monitors andadjusts the operation of the flow regulating valves and the variable speedcompressor to maintain optimal performance and uniform temperature control.The key features of the invention include:1. A variable speed compressor that provides a variable mass flow rate of theworking fluid.2. A cluster of fixed expansion devices, such as capillary tubes, orifice valves, orneedle valves, arranged in a combination of series and parallel configurations toachieve the desired pressure drop for any given flow rate of the working fluid.3. A plurality of flow regulating valves that control the flow of the working fluidthrough the fixed expansion devices, allowing for precise control of the flowresistance.4. An onboard control system programmed to operate the flow regulating valvesand adjust the speed of the variable speed compressor based on the current state ofthe system. This ensures that the working fluid flows in a specific pattern to achievethe desired flow rate and pressure drop, optimizing the performance of therefrigeration system.By implementing these features, the invention provides a more efficient and flexiblerefrigeration system capable of maintaining uniform temperature control andoptimal performance under varying operating conditions.BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGSThe above and other aspects, features and advantages of the embodiments of thepresent disclosure will be more apparent in the following description taken inconjunction with the accompanying drawings, in which:Figure 1 illustrates the schematic of the advanced refrigeration system according tothe present invention.Persons skilled in the art will appreciate that elements in the figures are illustratedfor simplicity and clarity and may not have been drawn to scale. For example, thedimensions of some of the elements in the figure may be exaggerated relative toother elements to help to improve understanding of various exemplaryembodiments of the present disclosure. Throughout the drawings, it should be notedthat like reference numbers are used to depict the same or similar elements, features,and structures.DETAILED DESCRIPTION OF THE INVENTIONThe following description with reference to the accompanying drawings is providedto assist in a comprehensive understanding of various embodiments of the presentdisclosure as defined by the claims and their equivalents. It includes various specificdetails to assist in that understanding, but these are to be regarded as merelyexemplary. Accordingly, those of ordinary skill in the art will recognize that variouschanges and modifications of the various embodiments described herein can bemade without departing from the scope and spirit of the present disclosure. Inaddition, descriptions of well-known functions and constructions may be omittedfor clarity and conciseness.All terms (including technical and scientific terms) used herein have the samemeaning as commonly understood by one of ordinary skill in the art to whichvarious embodiments belong. Further, the meaning of terms or words used in thespecification and the claims should not be limited to the literal or commonlyemployed sense but should be construed in accordance with the spirit of thedisclosure to most properly describe the present disclosure.The terminology used herein is for the purpose of describing particular variousembodiments only and is not intended to be limiting of various embodiments. Asused herein, the singular forms "a," "an" and "the" are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It will be furtherunderstood that the terms "comprises" and / or "comprising" used herein specify thepresence of stated features, integers, steps, operations, members, components,and / or groups thereof, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, members, components, and / or groupsthereof.The present disclosure will now be described more fully with reference to theaccompanying drawings, in which various embodiments of the present disclosureare shown.In the context of the present invention, the following technical terms are defined asfollows:Variable Speed Compressor: A compressor whose speed can be adjusted to varythe mass flow rate of the working fluid. This allows for precise control of thecooling process and helps maintain uniform temperature control in the refrigerationsystem.Fixed Expansion Devices: Components such as capillary tubes, orifice valves, orneedle valves that provide a specific flow resistance to the working fluid. Thesedevices are arranged in a combination of series and parallel configurations toachieve the desired pressure drop for any given flow rate.Flow Regulating Valves: Valves that control the flow of the working fluid throughthe fixed expansion devices. These valves are operated by the control system todirect the working fluid through specific paths, allowing for precise control of theflow resistance and ensuring the desired flow rate and pressure drop are achieved.The flow regulating valves are solenoid valves selected so as to work at cryogenictemperatures.Control System: An onboard system programmed to operate the flow regulatingvalves and adjust the speed of the variable speed compressor based on the currentstate of the system. The control system continuously monitors the system'sparameters and makes real-time adjustments to maintain optimal performance anduniform temperature control.Compressor-Aftercooler Pair: A combination of a compressor and an aftercoolerused to compress the working fluid to a higher pressure and then cool it by removingthe heat of compression. Multiple compressor-aftercooler pairs are used to achievea higher pressure ratio without damaging the compressor.Evaporator: A component in the refrigeration system where the working fluidabsorbs heat from the environment, providing the desired cooling effect. Theevaporator is typically located at the end of the expansion process.Mass Flow Rate: The amount of working fluid passing through a given point in thesystem per unit of time. It is typically measured in units such as kilograms persecond (kg / s) or pounds per hour (lb / h).Pressure Drop: The reduction in pressure of the working fluid as it passes throughthe fixed expansion devices. The pressure drop is a critical parameter in achievingthe desired cooling effect and is controlled by the arrangement of the expansiondevices and the operation of the flow regulating valves.Heat of Compression: The heat generated during the compression of the workingfluid in the compressor. This heat must be removed by the aftercooler to ensureoptimal performance and prevent overheating of the system.Throttling Process: A process in which the working fluid undergoes a pressuredrop without a significant change in enthalpy. This process is typically achievedusing fixed expansion devices such as capillary tubes, orifice valves, or needlevalves.The present invention provides an advanced refrigeration system designed tooptimize the control of the working fluid's mass flow rate and pressure drop, therebyenhancing the overall efficiency and performance of low-temperature coolingapplications. The system integrates a variable speed compressor, a cluster of fixedexpansion devices, flow regulating valves, and an onboard control system toachieve precise temperature control and efficient operation.The embodiment of the invention is illustrated in the accompanying figure, whichshows the schematic of the refrigeration system. The system comprises thefollowing key components:1. Variable Speed Compressor 1The initial stage compressor (1) compresses the working fluid to a higher pressure.The speed of the compressor is adjustable, allowing for precise control of the massflow rate of the working fluid. This feature enables uniform temperature controland efficient operation under varying conditions.2. Aftercooler 2The compressed working fluid is cooled by the aftercooler (2), which removes theheat of compression. This ensures optimal performance and prevents overheatingof the system.3. Variable Speed Compressor 3A subsequent stage compressor (3) further compresses the working fluid. Similarto Compressor 1, the speed of Compressor 3 is adjustable to maintain precisecontrol of the mass flow rate.4. Aftercooler 4The working fluid is further cooled by Aftercooler 4, which removes additional heatof compression from the fluid.5. Expansion Valves 5, 6, 7, 8, 9The system employs a cluster of fixed expansion devices (5, 6, 7, 8, 9) arranged ina combination of series and parallel configurations. These devices, which caninclude capillary tubes, orifice valves, or needle valves, provide specific flowresistance to achieve the desired pressure drop for any given flow rate of theworking fluid.6. Flow Control Valves 10, 11, 12, 13A plurality of flow regulating valves (10, 11, 12, 13) control the flow of the workingfluid through the fixed expansion devices. These valves are operated by the controlsystem to direct the working fluid through specific paths, allowing for precisecontrol of the flow resistance and ensuring the desired flow rate and pressure dropare achieved.7. Evaporator 14After undergoing the expansion process, the working fluid provides a cooling effectin the evaporator (14). The evaporator is responsible for absorbing heat from theenvironment, thereby achieving the desired cooling effect.8. Control System 15The onboard control system (15) is programmed to operate the flow regulatingvalves and adjust the speed of the variable speed compressors based on the currentstate of the system. The control system continuously monitors the system'sparameters and makes real-time adjustments to maintain optimal performance anduniform temperature control. It ensures that the working fluid flows in a specificpattern to achieve the desired flow rate and pressure drop, optimizing theperformance of the refrigeration system.In operation, the working fluid is initially compressed by Compressor 1 and cooledby Aftercooler 2. It is then further compressed by Compressor 3 and cooled byAftercooler 4. The compressed fluid undergoes several expansion processesthrough Expansion Valves 5, 6, 7, 8, and 9, with the flow regulated by Flow ControlValves 10, 11, 12, and 13. The expanded fluid provides a cooling effect inEvaporator 14. The entire system is controlled by Control System 15, which ensuresoptimal performance and uniform temperature control.By implementing these features, the invention provides a more efficient and flexiblerefrigeration system capable of maintaining uniform temperature control andoptimal performance under varying operating conditions. The integration of avariable speed compressor, multiple fixed expansion devices, flow regulatingvalves, and an advanced control system ensures that the refrigeration system candynamically adjust to changing conditions, minimizing inefficiencies andmaximizing the cooling effect.Best Mode of Working of the InventionThe best mode of working the present invention involves the integration andoperation of the variable speed compressor, fixed expansion devices, flowregulating valves, and the control system to achieve optimal performance andefficiency in a refrigeration system. The following steps outline the best mode ofworking the invention, as illustrated in the accompanying figure:1. Initial Compression and CoolingThe working fluid is initially compressed by the first variable speed compressor (1).The speed of Compressor 1 is adjusted by the control system (15) to provide thedesired mass flow rate of the working fluid. The compressed fluid is then cooled byAftercooler 2, which removes the heat of compression, ensuring the fluid is at anoptimal temperature for further compression.2. Subsequent Compression and CoolingThe working fluid is further compressed by the second variable speed compressor(3). Similar to Compressor 1, the speed of Compressor 3 is adjusted by the controlsystem (15) to maintain precise control of the mass flow rate. The compressed fluidis then cooled by Aftercooler 4, which removes additional heat of compression fromthe fluid.3. Expansion ProcessThe compressed working fluid undergoes several expansion processes through acluster of fixed expansion devices (5, 6, 7, 8, 9). These devices are arranged in acombination of series and parallel configurations to achieve the desired pressuredrop for any given flow rate of the working fluid. The flow of the working fluidthrough these expansion devices is regulated by flow control valves (10, 11, 12, 13).4. Flow RegulationThe flow control valves (10, 11, 12, 13) are operated by the control system (15) todirect the working fluid through specific paths, allowing for precise control of theflow resistance. The control system continuously monitors the system's parametersand makes real-time adjustments to the flow regulating valves and the speed of thevariable speed compressors to maintain optimal performance and uniformtemperature control.5. Cooling EffectAfter undergoing the expansion process, the working fluid provides a cooling effectin the evaporator (14). The evaporator absorbs heat from the environment, therebyachieving the desired cooling effect. The control system ensures that the workingfluid flows in a specific pattern to achieve the desired flow rate and pressure drop,optimizing the performance of the refrigeration system.6. Control System OperationThe onboard control system (15) is programmed to operate the flow regulatingvalves and adjust the speed of the variable speed compressors based on the currentstate of the system. The control system continuously monitors the system'sparameters, such as temperature, pressure, and flow rate, and makes real-timeadjustments to maintain optimal performance and uniform temperature control. Itensures that the working fluid flows in a specific pattern to achieve the desired flowrate and pressure drop, optimizing the performance of the refrigeration system.By implementing these steps, the invention provides a more efficient and flexiblerefrigeration system capable of maintaining uniform temperature control andoptimal performance under varying operating conditions. The integration of avariable speed compressor, multiple fixed expansion devices, flow regulatingvalves, and an advanced control system ensures that the refrigeration system candynamically adjust to changing conditions, minimizing inefficiencies andmaximizing the cooling effect.The present invention has been described in detail with reference to specificembodiments and accompanying figures. However, it is to be understood that theinvention is not limited to the specific embodiments disclosed. Variousmodifications and changes may be made to the invention without departing fromthe scope and spirit of the invention as defined by the appended claims.The invention is intended to cover all alternatives, modifications, and equivalentsthat may be included within the scope of the invention as defined by the claims.The specific components, configurations, and methods described herein areillustrative and not restrictive. The invention may be practiced with other variationsand modifications consistent with the principles and scope of the invention.Furthermore, the terminology used in the description of the invention is for thepurpose of describing particular embodiments only and is not intended to belimiting. The use of the singular forms "a," "an," and "the" include plural referentsunless the context clearly dictates otherwise. The terms "comprising," "including,""having," and "containing" are inclusive and open-ended and do not excludeadditional, unrecited elements or method steps.It is also to be understood that the invention is not limited to the specificconfigurations, components, or methods described herein. The invention may bepracticed with other variations and modifications consistent with the principles andscope of the invention. The scope of the invention is defined by the appended claimsand their equivalents.

Claims

1. A refrigeration system comprising: a variable speed compressor configured to compress a working fluid; a plurality of fixed expansion devices arranged in a cluster, each expansion device providing a specific flow resistance; a plurality of flow regulating valves configured to control the flow of the working fluid through the fixed expansion devices; and a control system configured to operate the flow regulating valves and adjust the speed of the variable speed compressor based on the current state of the system, thereby achieving a desired pressure drop and flow rate of the working fluid.

2. The refrigeration system of claim 1, wherein the fixed expansion devices are capillary tubes.

3. The refrigeration system of claim 1, wherein the fixed expansion devices include at least one of a capillary tube, orifice valve, or needle valve.

4. The refrigeration system of claim 1, wherein the control system is configured to operate the flow regulating valves to create a specific pattern of fluid flow through the fixed expansion devices to achieve the desired flow rate.

5. The refrigeration system of claim 1, further comprising a plurality of compressor-aftercooler pairs, each pair including a compressor and an aftercooler, wherein the aftercooler is configured to remove the heat of compression from the working fluid.

6. The refrigeration system of claim 5, wherein the control system is configured to regulate the speed of each compressor in the compressoraftercooler pairs to optimize the compression process and minimize the maximum temperature in the compressors.

7. The refrigeration system of claim 1, wherein the control system is configured to electronically control the flow regulating valves based on the present state of the system.

8. The refrigeration system of claim 1, wherein the control system is further configured to adjust the speed of the variable speed compressor to achieve a uniform temperature control in the refrigeration system.

9. The refrigeration system of claim 1, wherein the flow regulating valves are solenoid valves adapted work at cryogenic temperatures.

10. The refrigeration system of claim 1, wherein the control system is configured to minimize the work of compression by optimizing the speed of the variable speed compressor and the operation of the flow regulating valves.