Refrigeration system and method of controlling the same

Abstract

The application provides a refrigeration system and a control method thereof. The refrigeration system comprises a main circuit, an air supplement branch and a liquid supplement branch. The main circuit is connected with a multi-stage compressor, a condenser, an economizer, a main throttling element and an evaporator through pipelines. The air supplement branch is connected with an air outlet of the economizer and an intermediate stage air inlet of the multi-stage compressor through a pipeline. The liquid supplement branch is connected with the intermediate stage air inlet of the multi-stage compressor from a section of the main circuit with high-pressure liquid-phase refrigerant. According to the refrigeration system and the control method thereof, liquid-phase refrigerant can be introduced when the vibration or noise of the unit exceeds the limit through the design of the liquid supplement branch. The liquid-phase refrigerant in the form of droplets can effectively absorb the sound wave energy in the pipeline of the compressor, thereby reducing the overall exhaust pulsation of the compressor and ultimately reducing the noise and vibration at the condenser.

Description

Technical Field

[0001] This invention relates to the field of refrigeration equipment, and more specifically, to a refrigeration system and its control method. Background Technology

[0002] Currently, refrigeration systems and related equipment are widely used in various temperature control fields, including residential air conditioning, commercial air conditioning, cold chain transportation, and low-temperature preservation. Small-scale refrigeration equipment is technologically mature, but large-scale refrigeration equipment, due to its high power, high head, and multiple circuits, typically has higher technical requirements for system setup and control. As a type of application in large-scale refrigeration equipment, two-stage or three-stage centrifugal compressors have relatively high power and can withstand greater extreme refrigeration loads. However, when they only need to withstand partial loads (which is usually not the target design condition for centrifugal compressors), the small opening of the inlet guide vanes can lead to severe flow separation at high heads. This flow separation phenomenon generates significant pressure pulsations and causes considerable operating noise and vibration when the refrigerant flows into the condenser, thus affecting the user experience. Summary of the Invention

[0003] The present invention aims to provide a refrigeration system and its control method to improve system noise or vibration.

[0004] To achieve at least one objective of this application, according to one aspect of this application, a refrigeration system is provided, comprising: a main circuit connected via piping to a multi-stage compressor, a condenser, an economizer, a main throttling element, and an evaporator; a gas supply branch connected via piping to the outlet of the economizer and the intermediate stage inlet of the multi-stage compressor; and a liquid supply branch connected from a section of the main circuit having high-pressure liquid refrigerant to the intermediate stage inlet of the multi-stage compressor.

[0005] Optionally, the replenishment branch includes a replenishment valve for controlled opening or closing of the replenishment branch.

[0006] Optionally, it also includes a vibration sensor and / or a noise sensor disposed on the condenser and / or a compressor guide vane opening sensor disposed in the multi-stage compressor; wherein, the replenishment valve opens the replenishment branch when the detection result of the vibration sensor exceeds a vibration preset value and / or the detection result of the noise sensor exceeds a noise preset value and / or the compressor guide vane opening is less than a guide vane opening preset value.

[0007] Optionally, the replenishment valve is controlled to open or close to control the superheat of the main circuit to be no less than a preset superheat value.

[0008] Optionally, the replenishment branch is connected to the intermediate stage inlet of the multi-stage compressor in the section from the condenser outlet to the economizer.

[0009] Optionally, the liquid replenishment branch is connected from the section of the main circuit containing high-pressure liquid refrigerant to the intermediate stage inlet via the section between the gas replenishment valve on the gas replenishment branch and the intermediate stage inlet.

[0010] Optionally, the multi-stage compressor is a two-stage or three-stage centrifugal compressor.

[0011] Optionally, the replenishment valve is an electric valve and / or a throttling orifice plate.

[0012] Optionally, the liquid replenishment branch is configured such that the liquid refrigerant enters the intermediate stage inlet of the multi-stage compressor in droplet form.

[0013] To achieve at least one objective of this application, according to another aspect of this application, a control method for a refrigeration system is also provided, which is used in the refrigeration system as described above; the method includes: when the vibration of the condenser exceeds a preset vibration value and / or the noise exceeds a preset noise value or the compressor guide vane opening is less than a preset guide vane opening value, opening the liquid supply branch to introduce liquid refrigerant to absorb the vibration; and when the system superheat is less than a preset superheat value, disconnecting the liquid supply branch.

[0014] According to the refrigeration system and control method of this application, by setting a liquid replenishment branch between the section with high-pressure liquid refrigerant in the main circuit and the gas replenishment branch, liquid refrigerant can be introduced when the compressor vibration or noise exceeds the limit. The liquid refrigerant, which is in the form of droplets, can effectively absorb the sound wave energy in the compressor pipeline, thereby reducing the overall exhaust pulsation of the compressor and ultimately reducing the noise and vibration at the condenser. Attached Figure Description

[0015] Figure 1 This is a system schematic diagram of one embodiment of the refrigeration system of this application.

[0016] Figure 2 This is a system schematic diagram of another embodiment of the refrigeration system of this application. Detailed Implementation

[0017] The present application will now be described in detail with reference to exemplary embodiments shown in the accompanying drawings. However, it should be understood that the present application may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided herein to make the disclosure of the present application more complete and exhaustive, and to fully convey the concept of the present application to those skilled in the art.

[0018] See Figure 1This illustrates an embodiment of a refrigeration system according to this application. From a piping connection perspective, the refrigeration system 100 includes three parts: a main circuit 110, a gas supply branch 120, and a liquid supply branch 130. The main circuit 110 includes a multi-stage compressor 111, a condenser 112, an economizer 113, a main throttling element, and an evaporator 115, connected sequentially via piping. The gas supply branch 120 connects the outlet of the economizer 113 to the intermediate stage inlet of the multi-stage compressor 111 via piping. In this arrangement, when the refrigeration system is operating normally, the gaseous refrigerant compressed by the compressor enters the condenser 112 and condenses into a low-temperature, high-pressure liquid refrigerant. It then enters the economizer 113, where a portion of the liquid refrigerant evaporates, further cooling the remaining portion. The cooled liquid refrigerant then expands and throttles through the economizer float valve 113a, which acts as the main throttling element, forming a low-temperature, low-pressure liquid refrigerant. This refrigerant then enters the evaporator 115 to evaporate and absorb heat, and subsequently returns to the multi-stage compressor 111 via its inlet, beginning a new cycle. The remaining gaseous refrigerant, formed by evaporation and heat absorption in the economizer 113, directly enters the intermediate stage inlet of the multi-stage compressor 111 via the make-up gas branch 120 for enthalpy enhancement, improving system efficiency.

[0019] Based on this, the refrigeration system also includes a liquid replenishment branch 130, which connects from the section of the main circuit 110 containing high-pressure liquid refrigerant to the intermediate stage inlet of the multi-stage compressor 111. In this arrangement, when compressor vibration or noise exceeds limits, or when the guide vane opening is less than a preset value, liquid refrigerant can be introduced through this liquid replenishment branch. The droplet-shaped liquid refrigerant can effectively absorb the acoustic energy within the compressor piping, thereby reducing the overall exhaust pulsation of the compressor and ultimately reducing the noise and vibration of the unit.

[0020] The structure of each part of the refrigeration system will be described below. Furthermore, for further improvements in system energy efficiency, reliability, or other aspects, additional components may be added, as illustrated below.

[0021] For example, considering that the refrigerant supply branch 130 is mainly used to achieve noise reduction by absorbing sound wave energy through refrigerant droplets, it is not a flow path that needs to be constantly involved in system operation. Therefore, its opening and closing can be controlled. For example, a refrigerant supply valve 131 can be provided on it for controlled opening or closing of the refrigerant supply branch 130, and the specific form of the refrigerant supply valve 131 can be an actively controlled electric valve and / or a passively controlled orifice plate.

[0022] More specifically, additional sensors can be installed to determine the precise timing of activation or deactivation. For example, a vibration sensor or noise sensor can be added to the condenser 112. The replenishment valve 131 can activate the replenishment branch 130 when the vibration sensor's detection result exceeds a preset vibration value, or when the noise sensor's detection result exceeds a preset noise value. Alternatively, a compressor guide vane opening sensor can be installed in the multi-stage compressor. The replenishment valve 131 can activate the replenishment branch 130 when the compressor guide vane opening is less than a preset value. This ensures that the valve only operates when system noise exceeds limits, effectively and specifically improving the user experience. When there is no noise exceeding limits, the system's focus can still be on improving system energy efficiency.

[0023] In addition, the liquid replenishment valve 131 can be opened or closed according to the superheat of the evaporator in the main circuit 110 to avoid the problem of excessive liquid refrigerant bypass leading to too low a quantity of liquid refrigerant participating in the evaporation heat exchange in the main circuit, thereby ensuring the superheat of the evaporator outlet.

[0024] For example, considering that the main purpose of the replenishment branch 130 is to absorb sound wave energy through refrigerant droplets to achieve noise reduction, the location where the replenishment branch 130 connects to the main circuit 110 can be further designed. For instance, the liquid inlet of the replenishment branch 130 can be set in the section between the outlet of the condenser 112 and the economizer 113, thereby ensuring the purity of the liquid introduced into the replenishment branch 130; specifically, see Figure 1 The condenser 112 used in the figure is a shell-and-tube heat exchanger, which has a condenser float valve 112a at the bottom for throttling. High-temperature, high-pressure gas enters the condenser 112 from the compressor 111, exchanges heat with the coolant (e.g., cooling water) entering the condenser through the tube bundle, and then condenses into liquid refrigerant, accumulating at the bottom of the shell-and-tube heat exchanger. After reaching a certain pressure, it actuates the condenser float valve 112a to open the passage, and then flows into the economizer 113 for flash evaporation. Therefore, the bottom outlet of this type of condenser 112 is almost entirely low-temperature, high-pressure liquid refrigerant, and it remains in a liquid phase in the pipeline section before it enters the economizer for further flash evaporation and separation into liquid and gaseous refrigerants. Therefore, the refrigerant in this section meets the requirements for being guided into the intermediate stage suction port of the compressor for vibration absorption, so the liquid inlet of the makeup liquid branch 130 can be set here.

[0025] For example, the liquid outlet of the liquid replenishment branch 130 can be located in the section between the gas replenishment valve and the intermediate stage inlet on the gas replenishment branch 120. This ensures that this portion of liquid refrigerant is reliably and stably drawn into the intermediate stage of the compressor to perform its noise reduction function. For details, see [link to relevant documentation]. Figure 1Since the centrifugal compressor used here is a back-to-back two-stage compressor, it has an interstage flow path 111c located outside the compressor housing to guide refrigerant gas between the first stage 111a and the second stage 111b. For compressors with this type of external interstage flow path 111c, it is more convenient to introduce liquid refrigerant into the compressor to absorb sound wave energy and reduce vibration. For example, the gas supply branch 120 can be connected from any point on the interstage flow path 111c to perform its purpose of gas supply and enthalpy increase, while the liquid supply branch 130 can be connected from the gas supply valve of the gas supply branch 120 (…). Figure 1 (Not shown in the text) The downstream access pipeline section is indirectly connected to the interstage flow path 111c, or it can be directly connected to the interstage flow path 111c, or it can be directly connected to the first stage compressor volute (for back-to-back two-stage compressors), and finally enters the second or third stage compressor through the intermediate stage inlet of the compressor to achieve its vibration absorption purpose.

[0026] In addition, see also Figure 1 Considering that the inlet guide vanes of the centrifugal compressor are prone to flow separation at high head when the opening degree is low, the multi-stage compressor 111 used in the aforementioned system is a two-stage centrifugal compressor, which has a better noise reduction effect.

[0027] Furthermore, considering that droplets have a better effect on absorbing sound wave energy than liquid flow, the pipeline of the liquid replenishment branch 130 can be adjusted and configured, such as by changing its diameter, so that the liquid refrigerant enters in droplet form between the outlet of the economizer 113 and the intermediate stage inlet of the multi-stage compressor 111.

[0028] See also Figure 2 Another embodiment of the refrigeration system 100 is also shown here. It has the same characteristics as... Figure 1 The system flow path configurations shown in the embodiments are similar, therefore, unless there is a clear contradiction, the aforementioned... Figure 1 The various improvements described in the previous embodiments are also applicable to this embodiment, and will not be repeated here. The following will focus on describing them. Figure 2 The special features of the illustrated embodiment.

[0029] In comparison, Figure 2The illustrated refrigeration system 100 uses another type of compressor 111, namely a two-stage compressor with a built-in interstage flow path. Therefore, the flow path guiding the refrigerant gas between the first and second stages of the compressor is arranged inside the housing of the compressor 111. For this type of compressor, on the one hand, the liquid replenishment branch 130 can be connected downstream of the gas replenishment branch 120 to the intermediate stage inlet of the compressor so as to share part of the flow path with the gas replenishment branch 120 to achieve its vibration absorption purpose without making other modifications to the compressor; on the other hand, an additional port can be opened on the compressor so that the liquid replenishment branch 130 can be connected to the intermediate stage inlet of the compressor independently of the gas replenishment branch 120 to achieve its vibration absorption purpose and avoid mutual interference between the two branches.

[0030] Similarly, although not shown in the figure, an additional control method for the refrigeration system 100 is provided here, which can be applied to the refrigeration system 100 in the foregoing embodiments or any combination thereof, thereby providing better noise reduction for the system. Specifically, the method includes: when the vibration of the condenser 112 exceeds a preset vibration value and / or the noise exceeds a preset noise value and / or the guide vane opening is less than a preset value, opening the liquid supply branch 130 to introduce liquid refrigerant to absorb the vibration; thus, it only operates when the system noise exceeds the limit, which can effectively and specifically improve the user experience; while when there is no problem of noise exceeding the limit, the system's focus can still be on improving system energy efficiency. And when the system superheat is less than a preset superheat value, disconnecting the liquid supply branch 130. This is to avoid the problem of excessive liquid refrigerant bypass leading to an insufficient amount of liquid refrigerant participating in the evaporation heat exchange in the main circuit, thereby ensuring the superheat at the evaporator outlet.

[0031] The following will combine Figure 1 The embodiments of the refrigeration system shown are used to describe the refrigerant flow path in both the normal operating mode and the vibration-damped operating mode. Figure 2 and Figure 1 The only difference lies in the compressor selection; therefore, the working process described below also applies. Figure 2 The illustrated embodiment.

[0032] In normal operating mode, the gaseous refrigerant compressed by compressor 111 enters condenser 112 and condenses into low-temperature, high-pressure liquid refrigerant, which then enters economizer 113. At this time, since the gas supply branch 120 is closed by the gas supply valve, the refrigerant flows directly through economizer 113, expands and throttles at economizer float valve 113a, and enters evaporator 115 to absorb heat and evaporate into gaseous refrigerant. This gaseous refrigerant then flows into the first stage 111a of compressor 111, and after two stages of compression, flows out of compressor to begin a new cycle.

[0033] When the gas replenishment mode is activated, the gas replenishment branch 120 is opened by the gas replenishment valve. At this time, a portion of the liquid refrigerant evaporates in the economizer, allowing another portion of the liquid refrigerant to be further cooled. The cooled liquid refrigerant expands and throttles through the economizer float valve 113a, forming a low-temperature, low-pressure liquid refrigerant, which then enters the evaporator 115 to evaporate and absorb heat. Subsequently, it returns to the multi-stage compressor 111 through the inlet of the multi-stage compressor 111, and after two stages of compression, it flows out of the compressor 111 to begin a new cycle. The other portion of the gaseous refrigerant formed by evaporation and heat absorption in the economizer 113 directly enters the intermediate stage inlet of the compressor 111 through the gas replenishment branch 120 for gas replenishment and enthalpy increase, improving system efficiency.

[0034] Furthermore, when the condenser vibrates excessively due to reasons such as high head and low load, the liquid replenishment branch can be opened. At this time, high-pressure liquid refrigerant is introduced into the interstage flow path of the compressor through the bottom of the condenser 112, and forms tiny droplets to absorb sound wave energy in the interstage flow path, thereby reducing vibration.

[0035] The above examples primarily illustrate the refrigeration system and control method of the present invention. Although only some embodiments of the invention have been described, those skilled in the art should understand that the invention can be implemented in many other forms without departing from its spirit and scope. Therefore, the examples and embodiments shown are to be considered illustrative rather than restrictive, and the invention may cover various modifications and substitutions without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A refrigeration system, characterized in that, include: The main circuit connects to the multi-stage compressor, condenser, economizer, main throttling element, and evaporator via pipelines. The supplementary air branch is connected to the outlet of the economizer and the intermediate stage inlet of the multi-stage compressor via a pipeline; A makeup line, connecting from the section of the main circuit containing high-pressure liquid refrigerant to the intermediate stage inlet of the multi-stage compressor, wherein the makeup line includes a makeup valve for controlled opening or closing of the makeup line; and A vibration sensor and / or a noise sensor are installed on the condenser and / or a compressor guide vane opening sensor is installed in the multi-stage compressor; wherein, the replenishment valve opens the replenishment branch when the detection result of the vibration sensor exceeds the vibration preset value and / or the detection result of the noise sensor exceeds the noise preset value and / or the compressor guide vane opening is less than the guide vane opening preset value.

2. The refrigeration system according to claim 1, characterized in that, The replenishment valve is controlled to open or close to ensure that the superheat of the main circuit is not less than a preset superheat value.

3. The refrigeration system according to any one of claims 1 to 2, characterized in that, The replenishment branch is connected to the intermediate stage inlet of the multi-stage compressor from the condenser outlet to the economizer.

4. The refrigeration system according to any one of claims 1 to 2, characterized in that, The liquid replenishment branch is connected from the section of the main circuit containing high-pressure liquid refrigerant, via the section between the gas replenishment valve on the gas replenishment branch and the intermediate stage inlet, to the intermediate stage inlet.

5. The refrigeration system according to any one of claims 1 to 2, characterized in that, The multi-stage compressor is a two-stage or three-stage centrifugal compressor.

6. The refrigeration system according to any one of claims 1 to 2, characterized in that, The replenishment valve is an electric valve and / or a throttling orifice plate.

7. The refrigeration system according to any one of claims 1 to 2, characterized in that, The replenishment branch is configured such that the liquid refrigerant enters the intermediate stage inlet of the multi-stage compressor in droplet form.

8. A control method for a refrigeration system, used in the refrigeration system as described in any one of claims 1 to 7; characterized in that, The method includes: When the vibration of the condenser exceeds a preset vibration value and / or the noise exceeds a preset noise value, or the compressor guide vane opening is less than a preset guide vane opening value, the liquid replenishment branch is activated to introduce liquid refrigerant to absorb the vibration; and When the system superheat is less than the preset superheat value, the replenishment branch is disconnected.

Images