Centrifugal chiller condenser outlet vapor-liquid separation dryness physical reference system

Abstract

The application discloses a condenser outlet gas-liquid separation dryness physical reference system of a centrifugal refrigerating unit. The system comprises a condenser, a gas-liquid separation device, a gas backflow pipeline and a liquid output pipeline. The refrigerant charging quantity is accurately matched with the standard design working condition of the system, and no excess redundancy reserved in the traditional design. The gas-liquid separation device separates the refrigerant at the condenser outlet into gas phase and liquid phase; the gas backflow pipeline sends the gas phase back to the condenser for recooling; and the liquid output pipeline outputs the saturated liquid of the dryness to the front of a throttling device. The application locks the refrigerant dryness through a physical structure, simplifies the compressor control to matching the load flow, and eliminates the surge and liquid knock from the root. The system further comprises a dryness monitoring unit for verifying the state. The application is complementary to the prior dryness reference patent, and is suitable for centrifugal water chiller units and stock modification.

Description

Technical Field

[0001] This invention relates to the field of refrigeration system technology, and more specifically to a dryness physical reference system for centrifugal refrigeration units. Background Technology

[0002] Centrifugal compressors inherently carry the risks of surge and liquid slugging. Existing centrifugal chiller units typically employ feedback control based on chilled water outlet temperature: a temperature sensor detects the deviation between the evaporator outlet chilled water temperature and the set value, and a PID controller adjusts the compressor inlet guide vane opening or motor speed to match changes in building load.

[0003] To prevent surge under low load, existing technologies require additional auxiliary devices such as hot gas bypass valves. When the unit approaches the surge zone, the bypass valve opens, allowing some of the high-temperature, high-pressure exhaust gas to bypass directly to the evaporator, artificially increasing the compressor flow to avoid the surge point. This "post-compensation" control method suffers from low energy efficiency, high noise, and control lag, and liquid slugging control also exhibits lag.

[0004] In traditional refrigeration system design, to ensure no liquid shortage, surge, or liquid slugging under various extreme operating conditions, a large safety margin is usually reserved in various aspects such as heat exchanger area, compressor displacement, and refrigerant charge. This design concept of "trading area for safety and using margin to ensure operation" results in large equipment size, high manufacturing costs, and excessive liquid accumulation in the system under partial load, which actually increases the risk of liquid slugging.

[0005] The applicant had previously submitted several data points regarding the dryness of the refrigerant before it enters the throttling device. Based on the relevant patent applications (application numbers 202610262063.7, 202610274347.8, 202610311074.X, 202610311570.5), this patent is a further deepening and physical realization of this technical concept in centrifugal refrigeration units. Summary of the Invention

[0006] Physical basis of the invention

[0007] The core of this invention lies in the precise matching of refrigerant charge quantity with the standard design conditions of the system, eliminating the excessive redundancy inherent in traditional designs. Under this premise, a gas-liquid separation device is installed at the condenser outlet to separate the gas phase and force it back to the condenser for recooling, ensuring that the liquid flowing towards the throttling device is always saturated liquid (dryness fraction). The two work together to eliminate the need for excessive safety margins in heat exchangers and compressors to cope with extreme operating conditions, thus eliminating the physical conditions for surge and liquid slugging at the source.

[0008] Technical solution

[0009] This invention provides a physical reference system for dryness at the condenser outlet of a centrifugal refrigeration unit, characterized by gas-liquid separation, comprising:

[0010] • Condenser;

[0011] • A gas-liquid separator, the inlet of which is connected to the outlet of a condenser;

[0012] • Gas return pipeline, connecting the gas outlet of the gas-liquid separator to the condenser inlet;

[0013] • Liquid output pipeline, connecting the liquid outlet of the gas-liquid separator to the throttling device.

[0014] The refrigerant charge is precisely matched to the standard design conditions of the system, without the excessive redundancy reserved in traditional designs.

[0015] The system may also include a dryness detection unit for verifying dryness status; a compressor control unit that adjusts the load flow rate under superheat safety constraints; and a data output unit for real-time monitoring and energy efficiency assessment.

[0016] Beneficial effects

[0017] 1. Based on dryness As an absolute physical benchmark, it forms a technology family with prior patents;

[0018] 2. The refrigerant charge is precisely matched with the design operating conditions, eliminating the excessive redundancy of traditional designs;

[0019] 3. By physically locking dryness through gas-liquid separation, surge and liquid hammer are eliminated at their source;

[0020] 4. Compressor control is simplified to match load flow, with superheat as the only safety constraint;

[0021] 5. Heat exchangers and compressors do not require excessive safety margins, which can significantly reduce equipment size and manufacturing costs;

[0022] 6. Design and operation are unified; the system always operates under design conditions.

[0023] 7. It can monitor dryness in real time and calculate load for energy efficiency assessment;

[0024] 8. Applicable to frequency conversion and guide vane adjustment, as well as magnetic levitation units;

[0025] 9. Existing generating units can be retrofitted. Attached Figure Description

[0026] Figure 1 A schematic diagram of the system of the present invention.

[0027] Figure 2The control flowchart of the system of this invention. Detailed Implementation

[0028] Example 1: Basic System Structure

[0029] like Figure 1 As shown, the system includes a condenser 100, a gas-liquid separator 200, a gas return line 300, and a liquid output line 400. The condenser outlet is connected to the gas-liquid separator inlet. The gas phase is returned to the condenser inlet via the return line, and the liquid phase flows to the throttling device via the liquid output line. The system refrigerant charge is precisely matched to the design operating conditions, with no traditional redundancy.

[0030] A dryness detection unit 500 is installed on the liquid output pipeline to monitor the dryness status.

[0031] Example 2: Compressor Control

[0032] The compressor control unit 700 targets the flow demand caused by the load and adjusts the guide vane opening or rotation speed as long as the superheat at the evaporator outlet is not lower than a safe threshold (e.g., 3-8°C). When the superheat is lower than the threshold, the safety protection logic is executed first.

[0033] Example 3: Retrofitting of Existing Generating Units

[0034] A gas-liquid separation device and a return pipeline are installed at the condenser outlet to recover the original refrigerant. The recharge amount is then precisely matched according to the design conditions and connected to the control unit for commissioning and operation.

[0035] References

[0036] [1] Greitzer E M. Surge and rotating stall in axial flow compressors[J]. Journal of Engineering for Power, 1976.

Claims

1. A physical reference system for dryness at the condenser outlet of a centrifugal refrigeration unit, characterized in that, The refrigerant charge is precisely matched to the system's standard design conditions, without the excessive redundancy inherent in traditional designs. The system includes: (a) Condenser; (b) A gas-liquid separation device, the inlet of which is connected to the outlet of the condenser, for separating the refrigerant at the outlet of the condenser into a gas phase and a liquid phase; (c) Gas return line, connecting the gas outlet of the gas-liquid separator to the inlet of the condenser, for sending the separated gas phase back to the condenser for recooling; (d) Liquid output pipeline, connecting the liquid outlet of the gas-liquid separator to the throttling device, for outputting dryness. saturated liquid.

2. The system according to claim 1, characterized in that, The gas-liquid separation device is any one of a gravity separator, a centrifugal separator, or a cyclone separator.

3. The system according to claim 1, characterized in that, It also includes a dryness detection unit, which is installed on the liquid output pipeline for real-time monitoring of the dryness of the output refrigerant. To verify whether the system maintains its position state.

4. The system according to claim 1, characterized in that, It also includes a compressor control unit, which takes the refrigerant flow demand caused by the load as the control target and adjusts the guide vane opening or speed of the centrifugal compressor on the premise of ensuring that the superheat of the evaporator outlet is not lower than the safety threshold.

5. The system according to claim 4, characterized in that, The compressor is a mechanical bearing centrifugal compressor or a magnetic levitation centrifugal compressor.

6. The system according to claim 1, characterized in that, It also includes a real-time online monitoring and data output unit, which outputs data based on real-time dryness. Calculate the system load and output it continuously through the communication interface.

7. A method for protecting a centrifugal chiller unit from surge and liquid hammer based on the system described in claim 1, characterized in that, Includes the following steps: (1) Pass the refrigerant from the condenser outlet into a gas-liquid separator for gas-liquid separation; (2) The separated gas phase is sent back to the condenser for recooling through the gas return pipeline; (3) The separated liquid phase is output to the throttling device through the liquid output pipeline to ensure that the refrigerant flowing to the evaporator has a dryness level. saturated liquid; (4) Adjust the guide vane opening or speed of the centrifugal compressor according to the refrigerant flow demand caused by the load, and on the premise of ensuring that the superheat of the evaporator outlet is not lower than the safety threshold.

8. A centrifugal chiller unit comprising the system according to any one of claims 1-6, characterized in that, The unit is based on the condenser outlet dryness. It is in a physically locked state and automatically operates under the designed working conditions.

9. The centrifugal refrigeration unit according to claim 8, characterized in that, The unit is a single-stage or multi-stage centrifugal chiller, a heat pump system, or a modified existing unit with the system added.

10. The system according to claim 1, characterized in that, The gas return pipeline is equipped with a one-way valve.

Images