Cooling loop of centrifugal water chilling unit under low-pressure-ratio working condition

Abstract

The utility model relates to a cooling loop of a centrifugal water chilling unit under the low-pressure-ratio working condition. The cooling loop comprises a centrifugal compressor, an evaporator, a condenser and a throttling expansion valve. The centrifugal compressor, the condenser, the throttling expansion valve and the evaporator are sequentially connected in series to form a loop; the centrifugal compressor and the condenser are also connected with a second pipeline; the second pipeline is connected with a refrigerant pump; a third pipeline is connected between the condenser and the throttling expansion valve, and the other end of the third pipeline penetrates through the second pipeline and then is communicated with the second pipeline in a turning-back mode. The second pipeline is connected with a first valve assembly; and the third pipeline is connected with a second valve assembly. The cooling loop of the centrifugal water chilling unit under the low-pressure-ratio working condition aims to overcome the existing defects, and control optimization is achieved under the condition of different pressure ratios.

Description

Technical Field

[0001] The utility model relates to a cooling circuit for a centrifugal chiller under a low pressure ratio condition. Background Art

[0002] For the cooling circuit of a centrifugal chiller with a low pressure ratio commonly used in the current market, usually the way of bypassing the water circuit of the condenser is adopted to increase the outlet water temperature of the condenser, so as to provide sufficient system pressure ratio for compressor cooling. Or only simply drive an external refrigerant pump according to the temperature of the compressor motor / frequency converter to provide liquid refrigerant for compressor cooling.

[0003] By adopting the method of bypassing the water circuit, although the system pressure ratio can be provided by increasing the outlet water temperature of the condenser, so as to provide cooling for the compressor, this method increases the outlet water temperature of the condenser, that is, increases the condensation temperature, greatly increasing the power consumption of the compressor and reducing the operating performance of the unit;

[0004] By adopting the method of simply controlling the refrigerant pump according to the compressor temperature, the control is not accurate enough, and the refrigerant pump is still turned on for cooling when the temperature of the compressor electrical components is high and the system pressure ratio is sufficient. This situation increases the power consumption of the unit and reduces the circulating refrigerant flow rate, reducing the cooling capacity of the unit and the performance. Moreover, the long-term operation of the fluorine pump shortens its service life; when the fluorine pump is turned on and the internal cooling solenoid valve of the compressor is closed, the fluorine pump will have overcurrent protection due to excessive pressure difference, affecting the normal operation of the unit and the service life of the fluorine pump. Therefore, a cooling circuit for a centrifugal chiller under a low pressure ratio condition is proposed for the above problems. Summary of the Utility Model

[0005] The purpose of the utility model is to provide a cooling circuit for a centrifugal chiller under a low pressure ratio condition to achieve the optimization of control under different pressure ratios, overcoming the existing defects.

[0006] The technical solution to achieve the above purpose is: a cooling circuit for a centrifugal chiller under a low pressure ratio condition, including a centrifugal compressor, an evaporator, a condenser and a throttle expansion valve;

[0007] The centrifugal compressor, the condenser, the throttle expansion valve and the evaporator are connected in series in turn to form a circuit;

[0008] A second pipeline is also connected between the centrifugal compressor and the condenser;

[0009] A refrigerant pump is connected to the second pipeline;

[0010] A third pipeline is connected between the condenser and the throttle expansion valve, and the other end of the third pipeline penetrates through the second pipeline and then turns back to be connected to the second pipeline;

[0011] The second pipeline is connected with a first valve assembly; the third pipeline is connected with a second valve assembly.

[0012] Preferably, the first valve assembly includes a first maintenance ball valve, and the first maintenance ball valve is connected to the second pipeline.

[0013] Preferably, the second valve assembly includes a second maintenance ball valve, a differential pressure check valve and a first check valve, and the second maintenance ball valve, the differential pressure check valve and the first check valve are connected in series on the third pipeline in sequence.

[0014] Preferably, the connection point between the third pipeline and the second pipeline is located between the first maintenance ball valve and the refrigerant pump, and between the refrigerant pump and the centrifugal compressor.

[0015] The beneficial effects of the present utility model are as follows: for the cooling circuit of the centrifugal chiller under low pressure ratio conditions, the outlet water temperature of the condenser is not increased, that is, the system energy efficiency is not sacrificed; when the system pressure ratio is sufficient, there is no need to start the fluorine pump, and the compressor is cooled through the system pressure difference, ensuring the system energy efficiency; when the system pressure ratio is insufficient, the fluorine pump is started for compressor cooling, ensuring the normal operation of the compressor, and a differential pressure check valve is provided. After the compressor cooling solenoid valve is closed, the refrigerant at the outlet of the fluorine pump can flow to the evaporator on the low-pressure side, ensuring the safety of the fluorine pump. The cooling scheme of the centrifugal chiller under low pressure ratio conditions in the market is abandoned, and the refrigerant pump is used for cooling. The outlet water temperature of the condenser is not increased, and it is controlled according to different working conditions, realizing the optimization of control under different pressure ratios. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the cooling circuit of the centrifugal chiller under low pressure ratio conditions of the present utility model.

[0017] In the figure: 1. Centrifugal compressor; 2. Evaporator; 3. Condenser; 4. Throttle expansion valve; 5. First check valve; 6. Differential pressure check valve; 7. First maintenance ball valve; 8. Second maintenance ball valve; 9. Refrigerant pump; 10. Second pipeline; 11. Third pipeline. Detailed Embodiments

[0018] The technical solution of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings. In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0019] The present utility model will be further described below in conjunction with the accompanying drawings.

[0020] As Figure 1 shown, a cooling circuit for a centrifugal chiller under low pressure ratio conditions includes a centrifugal compressor 1, an evaporator 2, a condenser 3, and a throttle expansion valve 4; the centrifugal compressor 1, the condenser 3, the throttle expansion valve 4, and the evaporator 2 are sequentially connected in series to form a circuit; a second pipeline 10 is also connected between the centrifugal compressor 1 and the condenser 3; a refrigerant pump 9 is connected to the second pipeline 10; a third pipeline 11 is connected between the condenser 3 and the throttle expansion valve 4, and the other end of the third pipeline 11 penetrates through the second pipeline 10 and then folds back and communicates with the second pipeline 10.

[0021] Specifically, a first valve assembly is connected to the second pipeline 10; a second valve assembly is connected to the third pipeline 11. The first valve assembly includes a first service ball valve 7, and the first service ball valve 7 is connected to the second pipeline 10. The connection point between the third pipeline 11 and the second pipeline 10 is located between the first service ball valve 7 and the refrigerant pump 9, and between the refrigerant pump 9 and the centrifugal compressor 1.

[0022] Specifically, the second valve assembly includes a second service ball valve 8, a differential pressure check valve 6, and a first check valve 5, and the second service ball valve 8, the differential pressure check valve 6, and the first check valve 5 are sequentially connected in series to the third pipeline 11.

[0023] System pressure ratio = condenser 3 saturation pressure [absolute pressure] / evaporator 2 saturation pressure [absolute pressure].

[0024] When the system pressure ratio > [set value 1] and the temperature of the centrifugal compressor 1 > [set value 2], at this time, the refrigerant pump 9 is closed, and the cooling solenoid valve inside the centrifugal compressor 1 is opened. The refrigerant flows from the bottom of the condenser 3 through the first service ball valve 7 and the first check valve 5 to the cooling port of the centrifugal compressor 1 under the action of the system pressure difference for compressor cooling; when the temperature of the centrifugal compressor 1 < [set value 2 - deviation value] after cooling for a period of time, the cooling solenoid valve inside the centrifugal compressor 1 is closed, and the refrigerant flow in this circuit stops;

[0025] When the system pressure ratio < [Set value 1] and the temperature of the centrifugal compressor 1 > [Set value 2], the refrigerant pump 9 is turned on at this time, and the cooling solenoid valve inside the centrifugal compressor 1 is opened. Under the action of the refrigerant pump 9, the refrigerant flows from the bottom of the condenser 3 through the first maintenance ball valve 7 and the refrigerant pump 9 to the cooling port of the centrifugal compressor 1 for cooling the centrifugal compressor 1; when the temperature of the centrifugal compressor 1 < [Set value 2 - deviation value] after cooling for a period of time, the internal cooling solenoid valve of the centrifugal compressor 1 is closed. After the refrigerant pressure difference at the outlet of the refrigerant pump 9 > the self-pressure difference of the differential pressure check valve 6, the refrigerant pressurized by the refrigerant pump 9 passes through the differential pressure check valve 6, the second maintenance ball valve 8, flows through the throttle expansion valve 4, and finally reaches the bottom of the evaporator 2.

[0026] For the cooling circuit of this centrifugal chiller under low pressure ratio conditions, the outlet water temperature of the condenser is not increased, that is, the system energy efficiency is not sacrificed; when the system pressure ratio is sufficient, there is no need to turn on the fluorine pump, and the compressor is cooled through the system pressure difference, ensuring the system energy efficiency; when the system pressure ratio is insufficient, the fluorine pump is turned on for compressor cooling, ensuring the normal operation of the compressor, and a differential pressure check valve is provided. After the compressor cooling solenoid valve is closed, the refrigerant at the outlet of the fluorine pump can flow to the evaporator on the low-pressure side, ensuring the safety of the fluorine pump. It abandons the cooling solutions for centrifugal chillers under low pressure ratio conditions in the market, adopts refrigerant pump cooling, does not increase the outlet water temperature of the condenser, and has control for different working conditions, achieving the optimization of control under different pressure ratios.

[0027] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cooling circuit for a centrifugal chiller under low pressure ratio conditions, characterized in that: It comprises a centrifugal compressor (1), an evaporator (2), a condenser (3) and a throttling expansion valve (4); The centrifugal compressor (1), the condenser (3), the throttling expansion valve (4) and the evaporator (2) are sequentially connected in series to form a loop; The centrifugal compressor (1) and the condenser (3) are further connected via a second pipeline (10); The second pipeline (10) is connected to a refrigerant pump (9); A third pipeline (11) is connected between the condenser (3) and the throttling expansion valve (4), and the other end of the third pipeline (11) passes through the second pipeline (10) and then turns back to be connected to the second pipeline (10); The second pipeline (10) is connected to a first valve assembly; and the third pipeline (11) is connected to a second valve assembly.

2. The cooling circuit of the centrifugal chiller under low pressure ratio condition according to claim 1, characterized in that: The first valve assembly comprises a first maintenance ball valve (7), and the first maintenance ball valve (7) is connected to the second pipeline (10).

3. The cooling circuit of the centrifugal chiller under low pressure ratio condition according to claim 2, characterized in that: The second valve assembly comprises a second maintenance ball valve (8), a pressure differential check valve (6) and a first check valve (5); the second maintenance ball valve (8), the pressure differential check valve (6) and the first check valve (5) are sequentially connected in series to the third pipeline (11).

4. The cooling circuit of the centrifugal chiller under low pressure ratio condition according to claim 2, characterized in that: The connection point between the third pipeline (11) and the second pipeline (10) is located between the first maintenance ball valve (7) and the refrigerant pump (9), and between the refrigerant pump (9) and the centrifugal compressor (1).

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