KR101467804B1 - Turbo chiller - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a turbo chiller, and more particularly, to a turbo chiller capable of preventing impeller breakage and cooling ability from being reduced by blocking liquid refrigerant from being introduced into a compressor.

Description

Turbo chiller

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a turbo chiller, and more particularly, to a turbo chiller capable of preventing impeller breakage and cooling ability from being reduced by blocking liquid refrigerant from being introduced into a compressor.

Generally, a turbo chiller is a device for performing heat exchange between cold water and cooling water using a refrigerant, and includes a compressor, an evaporator, a condenser, and an expansion valve.

The compressor may include an impeller rotating by the driving force of the driving motor, a shroud receiving the impeller, and a variable diffuser converting the kinetic energy of the fluid discharged by the rotation of the impeller into pressure energy .

The evaporator and the condenser may have a shell-in-tube structure in which the cold water and the cooling water flow into the tube, respectively, and the refrigerant can be received in the shell.

Also, cold water is introduced into and discharged from the evaporator, and heat exchange is performed between the refrigerant and the cold water inside the evaporator, and the cold water is cooled in passing through the evaporator.

In addition, the cooling water is introduced into and discharged from the condenser, and the refrigerant and the cooling water are exchanged in the inside of the condenser, and the cooling water is heated in the process of passing through the condenser.

In addition, the refrigerant contained in the evaporator and the condenser can be maintained at a predetermined required refrigerant level, and the refrigerant level can be adjusted through an expansion valve provided between the condenser and the evaporator.

On the other hand, the refrigerant level of the condenser may fluctuate at the time of initial startup of the turbo chiller, at the time of load change, or at a set temperature change, and when the refrigerant level of the condenser can not be maintained constant, the reliability of the turbo chiller is lowered.

Further, the liquid refrigerant in the evaporator must be maintained at a refrigerant level in a steady state. When the level of the liquid refrigerant in the evaporator is increased, the liquid refrigerant flows into the compressor. As a result, the impeller inside the compressor is broken or the cooling capacity due to the reduction of the compression amount is decreased.

Disclosure of the Invention The present invention provides a turbo refrigerator capable of preventing liquid refrigerant from flowing into a compressor.

It is another object of the present invention to provide a turbo chiller which can prevent the impeller from being damaged and the cooling ability being reduced.

Another object of the present invention is to provide a turbo refrigerator which can reduce manufacturing cost and increase control responsiveness.

According to an aspect of the present invention, there is provided a refrigerator comprising: a compressor including an impeller for compressing refrigerant; a condenser for exchanging heat between the refrigerant introduced from the compressor and the cooling water; An evaporator for exchanging heat with cold water, an expansion valve provided between the condenser and the evaporator, And a controller for decreasing the opening degree of the expansion valve to lower the level of the liquid refrigerant in the evaporator when it is determined that the liquid refrigerant is sucked into the compressor based on the evaporation pressure change amount of the refrigerant and the compressor discharge superheating degree A turbo refrigerator is provided.

According to another aspect of the present invention, there is provided a refrigerant compressor comprising: a multi-stage compressor having a plurality of stages; a condenser for exchanging heat between the refrigerant and cooling water introduced from the compressor; a liquid refrigerant and a gaseous refrigerant separated from the refrigerant discharged from the condenser; A first expansion valve disposed between the condenser and the phase separator, a second expansion valve disposed between the phase separator and the evaporator, and a second expansion valve disposed between the phase separator and the evaporator, A second expansion valve provided between the first expansion valve and the second expansion valve; And at least one of the first expansion valve and the second expansion valve to lower the level of the liquid refrigerant in the evaporator if it is determined that the liquid refrigerant is sucked into the compressor based on the evaporation pressure change amount of the refrigerant and the compressor discharge superheating degree of the compressor And a control section for reducing the opening degree of the expansion valve.

According to another aspect of the present invention, there is provided a refrigerator comprising: a compressor including an impeller for compressing refrigerant; a condenser for exchanging heat between the refrigerant and cooling water introduced from the compressor; and a heat exchanger for exchanging heat between the refrigerant discharged from the condenser and the cold water An expansion valve provided between the condenser and the evaporator; And a controller for controlling the opening degree of the expansion valve based on the refrigerant level of the condenser and a normal control mode for controlling the opening degree of the expansion valve based on the evaporation pressure change amount and the compressor discharge superheating degree of the refrigerant, There is provided a turbo refrigerator including a control unit having emergency control models for adjusting the opening degree of the expansion valve to lower an internal liquid refrigerant level.

As described above, according to the turbo refrigerating machine according to the embodiment of the present invention, the liquid refrigerant can be prevented from flowing into the compressor, and the liquid refrigerant level in the evaporator can be easily controlled.

Further, according to the turbo chiller related to one embodiment of the present invention, it is possible to prevent the impeller from being damaged and the cooling ability being reduced.

Further, according to the turbo refrigerator related to the embodiment of the present invention, it is possible to reduce the manufacturing cost and increase the control responsiveness.

1 is a conceptual view of a turbo refrigerator according to a first embodiment of the present invention;
2 is a block diagram of a turbo refrigerator according to a first embodiment of the present invention;
3 is a flowchart showing a control method of the turbo chiller according to the first embodiment of the present invention.
4 is a graph for explaining an operating state of a turbo chiller related to the first embodiment of the present invention.
5 is a conceptual view of a turbo refrigerator according to a second embodiment of the present invention;
6 is a block diagram of a turbo refrigerator according to a second embodiment of the present invention;
7 is a ph diagram of a turbo refrigerator according to a second embodiment of the present invention.

Hereinafter, a turbo refrigerator according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

In addition, the same or corresponding components are denoted by the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted. For convenience of explanation, the size and shape of each constituent member shown may be exaggerated or reduced have.

On the other hand, terms including an ordinal number such as a first or a second may be used to describe various elements, but the constituent elements are not limited by the terms, and the terms may refer to a constituent element from another constituent element It is used only for the purpose of discrimination.

Hereinafter, each component constituting the turbo chiller 1 related to the first embodiment will be described in detail with reference to the accompanying drawings.

2 is a block diagram of a turbo chiller related to the first embodiment of the present invention, and Fig. 3 is a block diagram of a turbo chiller related to the first embodiment of the present invention. Fig. 4 is a graph for explaining an operating state of the turbo chiller related to the first embodiment of the present invention.

1, the turbo chiller 1 includes a compressor 10 for compressing a refrigerant, a condenser 30 for condensing the refrigerant, an expansion valve 40 for expanding the refrigerant, an evaporator 40 for evaporating the refrigerant, (20).

1 and 2, a turbo chiller 1 according to a first embodiment of the present invention includes a compressor 10 including an impeller 11 for compressing a refrigerant, A condenser 30 for exchanging heat between the refrigerant and the cooling water, an evaporator 20 for exchanging heat between the refrigerant discharged from the condenser 30 and the cold water, an expansion valve 40 provided between the condenser and the evaporator, (20) to lower the level of the liquid refrigerant in the evaporator (20) if it is determined that the liquid refrigerant is sucked into the compressor (10) based on the pressure change amount and the compressor discharge superheating degree And a control unit 70.

Hereinafter, each component constituting the turbo chiller 1 will be described in detail with reference to the accompanying drawings.

The compressor 10 includes an impeller 11 rotated by a driving force of a driving motor, a shroud 11 accommodating the impeller 11, and a variable diffuser 11, which converts kinetic energy of the fluid discharged by rotation of the impeller into pressure energy. (Diffuser).

The evaporator 20 and the condenser 30 may have a shell-in-tube structure in which the cold water and the cooling water flow respectively into the tube and the refrigerant can be accommodated in the shell .

In addition, chilled water is introduced into and discharged from the evaporator 20, and heat exchange is performed between the refrigerant and the cold water in the evaporator 20. The cold water is cooled in the process of passing through the evaporator 20, do.

In addition, condenser water is introduced into and discharged from the condenser 30, and heat exchange is performed between the refrigerant and the cooling water in the condenser 30. The cooling water is heated in the course of passing through the condenser 30, do.

In addition, the refrigerant received in the evaporator 20 and the condenser 30 can be maintained at a predetermined required refrigerant level, and the refrigerant level can be adjusted through the expansion valve 40, The level of the liquid refrigerant in the evaporator 20 and the condenser 30 can be adjusted.

As described above, the evaporator 20 has a shell-like tube structure, and the liquid refrigerant inside the evaporator 20 must be maintained at a predetermined steady state refrigerant level inside the shell. When the amount of refrigerant flowing into the evaporator 20 increases due to the increase of the opening degree of the expansion valve 40, the refrigerant level in the evaporator 20 can be increased. On the contrary, when the opening degree of the expansion valve 40 is decreased The refrigerant level in the evaporator 20 can be lowered when the amount of refrigerant flowing into the evaporator 20 decreases.

That is, by regulating the opening degree of the expansion valve (40), the liquid refrigerant level in the evaporator (20) can be maintained at the steady state refrigerant level.

As described above, when the refrigerant in the evaporator 20 can not be maintained at the predetermined refrigerant level, the liquid refrigerant in the evaporator 20 can be introduced into the compressor 10, When the compressor 10 flows into the compressor 10, the impeller 11 of the compressor 10 may be damaged or the cooling capacity may decrease as the compression amount of the compressor 10 is reduced.

2 and 3, in order to determine whether liquid refrigerant flows into the compressor 10, the controller 70 controls the compressor 10 based on the evaporation pressure change amount of the refrigerant and the compressor discharge superheat degree, The opening degree of the expansion valve 40 is reduced to lower the level of the liquid refrigerant in the evaporator 20 when it is determined that the liquid refrigerant is sucked into the inside of the evaporator 20.

Here, the evaporation pressure variation S _n of the refrigerant is measured at a predetermined time interval, and may be determined as a weighted average of the variation amount X _n of the present evaporation pressure and the variation amount X _{n -1} of the previous evaporation pressure.

The change amount X _n of the present evaporation pressure is determined as the difference value between the present evaporation pressure P _n and the previously measured evaporation pressure P _{n -1} and the change amount X _{n -1} of the previous evaporation pressure Can be determined as the difference between the previous evaporation pressure (P _n-1 ) and the previously measured evaporation pressure (P _{n -2} ).

Further, the first weight (λ ₁ ) for the variation amount (X _n ) of the present evaporation pressure is smaller than the second weight (λ ₂ ) for the amount of the previous evaporation pressure change (X _{n -1} ), and the first weight ₁ ) and the second weight (? ₂ ) may be one.

In summary, the evaporation pressure variation S _n of the refrigerant can be expressed by Equation (4) below.

&Quot; (4) "

Also, the first weight (λ ₁ ) for the current variation of the evaporation pressure (X _n ) may be 0.2, and the second weight (λ ₂ ) for the previous evaporation pressure change (X _{n -1} ) Lt; / RTI >

On the other hand, the discharge superheat degree (C ° C) of the compressor is defined as the difference between the temperature of the refrigerant discharged from the compressor (10) and the condensation temperature of the refrigerant, and the discharge superheat degree (C ° C) In one embodiment, the discharge superheat (C ° C) can be maintained at 6 ° C or higher. That is, it is judged that the liquid refrigerant flows into the compressor 10 when the discharge superheat degree (C ° C) is smaller than a certain value.

2, the turbo chiller 1 according to the first embodiment of the present invention includes at least one pressure sensor 90 for measuring the evaporation pressure change amount S _n of the refrigerant and the discharge superheat degree C ° C And a temperature sensor 80.

On the other hand, the controller 70 can control the opening degree of the expansion valve 40 to decrease when the evaporation pressure change amount S _n is equal to or lower than the predetermined value and the superheating degree C ° C is lower than the predetermined temperature A ° C have.

That is, according to the turbo refrigerator 1 related to the first embodiment of the present invention, it is judged that the liquid refrigerant flows into the compressor 10 based on the evaporation pressure change amount S _n and the discharge superheat degree C And reduces the amount of liquid refrigerant flowing into the evaporator 20 by reducing the opening degree of the expansion valve 40 in order to prevent the liquid refrigerant from flowing into the compressor 10.

Meanwhile, the predetermined value to be compared with the evaporation pressure change amount S _n is 0.1, and the predetermined temperature (A ° C) to be compared with the discharge superheat degree (C) may be 2 ° C. In particular, the evaporation pressure variation S _n may be positive or negative depending on the case, and the predetermined value may be +/- 1.

The opening value of the expansion valve 40 controlled by the controller 70 may be determined by multiplying the current expansion valve opening value by a weight R determined according to Equation 1 below.

[Equation 1]

, A<= B <=6

, A < = B < = 6

As described above, A corresponds to the above-mentioned predetermined temperature, C corresponds to the currently measured discharge superheating, and in one embodiment, A may be 2, and B may be determined to be any value between 2 and 6 For example, B may be 4, and A, B, and C may be determined experimentally.

Referring to FIG. 3, a method of controlling a turbo refrigerator 1 according to an embodiment of the present invention includes a step S100 of operating a compressor, a step S200 of comparing a variation value S _n of the evaporation pressure with a predetermined value, (S300) of comparing the discharge superheating degree and the predetermined temperature of the compressor when the change amount of the evaporation pressure (S _n ) is equal to or less than a predetermined value (S300) and adjusting the opening value of the expansion valve when the discharge and the heat degree of the compressor are smaller than the predetermined temperature (S400).

The control method of the turbo refrigerator 1 further includes a step S500 of comparing the discharge superheating degree and the predetermined temperature of the compressor after a lapse of a predetermined period of time (S400), and returning to normal control when the discharge and the temperature of the compressor are equal to or higher than the predetermined temperature, . &Lt; / RTI &gt;

Here, comparing the predetermined temperature, the controller 70 includes a first amount of change of the evaporation pressure, compare the (S _n) to a predetermined value the discharge of only the compressor when the change amount (S _n) of the vapor pressure equal to or lower than the predetermined value, overheating help (S300). If the change amount (S _n ) of the evaporation pressure is greater than the predetermined value, the change amount (S _n ) of the evaporation pressure after a predetermined time is again compared with a predetermined value.

4 is a graph showing the relationship between the expansion valve opening degree and the compressor discharge superheating degree.

Referring to FIG. 4, the controller 70 increases the opening degree of the expansion valve 40 when the discharge and the degree of the entering into the regions A1 and A2 become smaller than a predetermined temperature, (B1, B2) in which the opening degree of the expansion valve 40 increases after the time (A1, A2).

On the other hand, the liquid refrigerant level in the evaporator 20 is closely related to the refrigerant level in the condenser. Particularly, the refrigerant level of the condenser 30 may fluctuate at the time of initial startup of the turbo chiller 1, at the time of a load change, or at a set temperature change. If the refrigerant level of the condenser can not be maintained constant, The problem of falling occurs.

Whether the liquid refrigerant is introduced into the compressor 10 can be judged based on the refrigerant level of the evaporator 20 or based on the refrigerant level of the condenser 30.

Also, the refrigerant level of the condenser 30 can be measured by a sensor, and the sensor can be a capacitance level sensor. That is, the turbo chiller 1 adds at least two electrostatic capacity detection sensors located at different heights along the increasing direction of the refrigerant level in order to detect the refrigerant level in the condenser 30 in the normal control mode As shown in FIG.

The control of the turbo chiller 1 based on the refrigerant level of the condenser 30 can be referred to as a normal control in this way and the turbo refrigerator 1 can be referred to as a normal control based on the evaporation pressure change amount, Controlling the refrigerator 1 may be referred to as emergency control. Particularly, in the case of the emergency control, it may be advantageous for the partial load operation of the turbo chiller 1.

Specifically, the control unit 70 determines whether or not the refrigerant level of the refrigerant is higher than the normal control mode for adjusting the opening degree of the expansion valve 40 based on the refrigerant level of the condenser 30, And an emergency control mode for controlling the opening degree of the expansion valve to lower the liquid refrigerant level in the evaporator (20) if it is determined that the liquid refrigerant is sucked into the compressor (10).

The method of controlling the expansion valve by measuring the evaporation pressure of the refrigerant and the superheating degree of the compressor discharge in the emergency control mode is as described above and the process of controlling the turbo refrigerator 1 in the emergency control mode, The controller 70 may decrease the opening degree of the expansion valve, and after the lapse of a predetermined time, the turbo chiller 1 may be operated in the normal control mode if the discharge and the degree of heat are greater than a predetermined temperature A ° C.

As described above, according to the turbo chiller 1 related to the first embodiment of the present invention, the liquid refrigerant can be prevented from flowing into the compressor, and the liquid refrigerant level in the evaporator can be easily controlled.

Further, according to the turbo chiller 1 related to the first embodiment of the present invention, it is possible to prevent the breakage of the impeller and the cooling ability from being reduced, and the manufacturing cost can be reduced and the control response can be enhanced.

6 is a block diagram of a turbo chiller related to a second embodiment of the present invention, and Fig. 7 is a block diagram of a turbo chiller related to the second embodiment of the present invention. Fig. It is Ph diagram of refrigerator.

Referring to FIGS. 5 and 6, a turbo chiller 100 according to a second embodiment of the present invention includes a multi-stage compressor 110 having a plurality of stages, a heat exchanger 110 for exchanging heat between the refrigerant introduced from the compressor 110 and the cooling water, A phase separator 150 for separating the liquid refrigerant and the gaseous refrigerant from the refrigerant discharged from the condenser 130 and the condenser 130 and discharging the gaseous refrigerant to the compressor 110, A first expansion valve 141 provided between the condenser 130 and the phase separator 150 and a second expansion valve 141 provided between the phase separator 150 and the evaporator 120. The first expansion valve 141 is disposed between the evaporator 120 and the condenser 130, And a second expansion valve 142 provided in the second expansion valve 142.

If it is determined that the liquid refrigerant is sucked into the compressor based on the evaporation pressure change amount of the refrigerant and the compressor discharge superheating degree, the turbo refrigerant 100 may be supplied with the first expansion valve And a controller (170) for reducing the opening degree of at least one of the expansion valve and the second expansion valve.

Hereinafter, each component constituting the turbo chiller 100 related to the second embodiment will be described in detail with reference to the accompanying drawings.

The compressor 110 has a plurality of stages, and may include a low-pressure compression section 111 and a high-pressure compression section 112 in one embodiment. Specifically, the refrigerant discharged from the evaporator 120 flows into the low-pressure compression section 111, and the gaseous refrigerant separated from the phase separator 150 flows into the high-pressure compression section 112.

As a result, since the gaseous refrigerant separated by the phase separator 150 and the refrigerant compressed by the low-pressure compressor 111 are compressed together with the high-pressure compressor 112, the compression work applied to the compressor 110 is reduced. The compressing work to be applied to the compressor 110 is reduced and the operation range of the compressor 110 is increased.

The condenser 130 and the evaporator 120 have the same structure as that of the condenser 30 and the evaporator of the turbo chiller 1 according to the first embodiment, so a detailed description thereof will be omitted.

That is, the turbo chiller 100 related to the second embodiment divides the compressor 110 into a plurality of stages in order to increase the operation range of the compressor 110, increase the efficiency of the turbo chiller 100, A first expansion valve 141 provided between the condenser 130 and the phase separator 150 and a phase separator 150 provided between the evaporator 120 and the evaporator 120 The present invention is different from the turbo chiller 1 related to the first embodiment only in that the second expansion valve 142 is provided between the first expansion valve 142 and the second expansion valve 142.

In the second embodiment, the controller 170 controls the opening degree of at least one of the first expansion valve 141 and the second expansion valve 142 to adjust the liquid refrigerant level of the evaporator 120 Specifically, it is possible to adjust the opening degree of any one of the expansion valves 141 and 142 and adjust the opening degree of each of the first expansion valve 141 and the second expansion valve 142.

Hereinafter, the control unit 170 controls the opening degree of the second expansion valve 142 for convenience of explanation.

As described above, the evaporator 120 has a shell-like tube structure, and the liquid refrigerant inside the evaporator 120 must be maintained at a predetermined steady state refrigerant level inside the shell. The refrigerant level in the evaporator 120 can be increased when the degree of opening of the second expansion valve 142 increases and the amount of refrigerant flowing into the evaporator 120 increases. The refrigerant level in the evaporator 120 may be lowered when the amount of refrigerant flowing into the evaporator 120 decreases.

That is, by regulating the opening degree of the second expansion valve 142, the liquid refrigerant level in the evaporator 120 can be maintained at the steady state refrigerant level.

As described above, when the refrigerant in the evaporator 120 can not be maintained at the predetermined refrigerant level, the liquid refrigerant in the evaporator 120 can be introduced into the compressor 110, When the refrigerant flows into the compressor 110, the impeller (not shown) of the compressor 110 may be damaged or the cooling capacity may decrease as the compression amount of the compressor 110 decreases.

In order to determine whether the liquid refrigerant flows into the compressor 10 in the turbo chiller 100 related to the second embodiment, the controller 170 controls the compressor 10 based on the evaporation pressure change amount of the refrigerant and the compressor discharge superheat degree. The second expansion valve 142 is opened to lower the liquid refrigerant level in the evaporator 120 when it is determined that the liquid refrigerant is sucked into the evaporator 120.

Here, the evaporation pressure variation S _n of the refrigerant is measured at a predetermined time interval, and may be determined as a weighted average of the variation amount X _n of the present evaporation pressure and the variation amount X _{n -1} of the previous evaporation pressure.

The change amount X _n of the present evaporation pressure is determined as the difference value between the present evaporation pressure P _n and the previously measured evaporation pressure P _{n -1} and the change amount X _{n -1} of the previous evaporation pressure Can be determined as the difference between the previous evaporation pressure (P _n-1 ) and the previously measured evaporation pressure (P _{n -2} ).

Further, the first weight (λ ₁ ) for the variation amount (X _n ) of the present evaporation pressure is smaller than the second weight (λ ₂ ) for the amount of the previous evaporation pressure change (X _{n -1} ), and the first weight ₁ ) and the second weight (? ₂ ) may be one.

In summary, the evaporation pressure variation S _n of the refrigerant can be expressed by Equation (4) below.

&Quot; (4) &quot;

Also, the first weight (λ ₁ ) for the current variation of the evaporation pressure (X _n ) may be 0.2, and the second weight (λ ₂ ) for the previous evaporation pressure change (X _{n -1} ) Lt; / RTI &gt;

On the other hand, the discharge superheat degree (C ° C) of the compressor is defined as the difference between the temperature of the refrigerant discharged from the compressor (10) and the condensation temperature of the refrigerant, and the discharge superheat degree (C ° C) In one embodiment, the discharge superheat (C ° C) can be maintained at 6 ° C or higher. That is, it is judged that the liquid refrigerant flows into the compressor 10 when the discharge superheat degree (C ° C) is smaller than a certain value.

Referring to FIG. 6, the turbo chiller 100 according to the second embodiment of the present invention includes at least one pressure sensor 190 for measuring the evaporation pressure change amount S _n of the refrigerant and the superheating degree (C ° C) And a temperature sensor 180.

On the other hand, the controller 170 can control the opening degree of the expansion valve 40 to decrease when the evaporation pressure change amount S _n is equal to or lower than a predetermined value and the superheat degree C ° C is lower than the predetermined temperature A ° C have.

That is, according to the turbo chiller 100 related to the second embodiment of the present invention, it is determined that the liquid refrigerant flows into the compressor 110 based on the evaporation pressure change amount S _n and the discharge superheat degree C And reduces the amount of the liquid refrigerant introduced into the evaporator 120 by reducing the opening degree of the second expansion valve 142 in order to prevent the liquid refrigerant from flowing into the compressor 110.

Meanwhile, the predetermined value to be compared with the evaporation pressure change amount S _n is 0.1, and the predetermined temperature (A ° C) to be compared with the discharge superheat degree (C) may be 2 ° C. In particular, the evaporation pressure variation S _n may be positive or negative depending on the case, and the predetermined value may be +/- 1.

The opening value of the expansion valve 40 controlled by the controller 170 may be determined by multiplying the current expansion valve opening value by a weight R determined according to Equation (2).

&Quot; (2) &quot;

, A<= B <=6

, A < = B < = 6

As described above, A corresponds to the above-mentioned predetermined temperature, C corresponds to the currently measured discharge superheating, and in one embodiment, A may be 2, and B may be determined to be any value between 2 and 6 For example, B may be 4, and A, B, and C may be determined experimentally.

As in the first embodiment, the control method of the turbo chiller 100 according to one embodiment of the present invention includes the steps of operating the compressor, comparing the variation amount S _n of the evaporation pressure with a predetermined value, Comparing the discharge superheating degree and the predetermined temperature of the compressor when the change amount S _{n of the} compressor is equal to or less than a predetermined value and adjusting the opening value of the second expansion valve when the discharge and the heat radiation degree of the compressor are smaller than the predetermined temperature .

Further, the control method of the turbo chiller 100 may further include a step of comparing the discharge superheating degree and the predetermined temperature of the compressor after a lapse of a predetermined time, and returning to the normal control when the discharge and the heat of the compressor are at a predetermined temperature or more have.

Here, comparing the predetermined temperature, the control unit 170 first amount of change of the evaporation pressure, compare the (S _n) to a predetermined value the discharge of only the compressor when the change amount (S _n) of the vapor pressure equal to or lower than the predetermined value, overheating help If the change amount S _n of the evaporation pressure is greater than the predetermined value, the change amount S _n of the evaporation pressure is compared with a predetermined value again after a predetermined time elapses.

5 and 7, the P (pressure) -h (enthalpy) diagram of the turbo chiller 100 related to the second embodiment, wherein the M line indicates a case where the discharge and the degree of heat are smaller than a predetermined temperature, And the discharge and the degree of heat are equal to or higher than a predetermined temperature.

The compressor 110 constituting the turbo chiller 100 related to the second embodiment includes a low pressure compressing section 111 and a high pressure compressing section 112. M1 and L1 denote Ph And M2 and L2 denote Ph diagrams in the high-pressure compression section 112, respectively.

When the discharge and the heat are less than the predetermined temperature, the compressor 110 is positioned in the D area after the completion of the compression by the compressor 110. If the discharge and the heat are less than the predetermined temperature, And is located in the leading image C region.

As described above, according to the present invention, the liquid refrigerant can be prevented from flowing into the compressor, and the liquid refrigerant level in the evaporator can be easily controlled.

Further, according to the turbo refrigerator related to the present invention, it is possible to prevent the impeller from being damaged and the cooling ability being reduced.

Further, according to the turbo refrigerator related to the present invention, it is possible to reduce the manufacturing cost and increase the control responsiveness.

The foregoing description of the preferred embodiments of the present invention has been presented for purposes of illustration and various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention, And additions should be considered as falling within the scope of the following claims.

1: Turbo freezer
10: Compressor
20: Evaporator
30: condenser
40: expansion valve

Claims (20)

A compressor including an impeller for compressing refrigerant;
A condenser for exchanging heat between the refrigerant introduced from the compressor and the cooling water;
An evaporator for exchanging heat between the refrigerant discharged from the condenser and the cold water;
An expansion valve provided between the condenser and the evaporator; And
When it is determined that the liquid refrigerant is sucked into the compressor based on the evaporation pressure change amount of the refrigerant and the compressor discharge superheating degree which are determined by a weighted average of the change amount of the present evaporation pressure and the change amount of the previous evaporation pressure, And a control unit for reducing the opening degree of the expansion valve to lower the opening degree of the expansion valve,
Wherein the control unit controls the opening degree of the expansion valve to decrease when the change amount of the evaporation pressure of the refrigerant is equal to or lower than a predetermined value and the discharge superheat degree (C) is equal to or lower than a predetermined temperature (A DEG C). The method according to claim 1,
Wherein the evaporation pressure change amount of the refrigerant is measured at a predetermined time interval. 3. The method of claim 2,
Wherein the first weight for the variation of the present evaporation pressure is less than the second weight for the previous evaporation pressure change and the sum of the first weight and the second weight is one. The method of claim 3,
Wherein the first weight is 0.2. delete The method according to claim 1,
Wherein the predetermined value is 0.1, and the predetermined temperature is 2 [deg.] C. 3. The method of claim 2,
The opening value of the expansion valve controlled by the control unit is determined by multiplying the current expansion valve opening value by the weight R determined according to the following equation (1)
Wherein A is the predetermined temperature, B is an experimentally determined arbitrary value between A and the constant 6, and C is the currently measured discharge superheating degree.
[Equation 1]

A < = B < = 6 The method according to claim 1,
Further comprising a phase separator for separating the liquid refrigerant and the gaseous refrigerant from the refrigerant discharged from the condenser and discharging the gaseous refrigerant to the compressor,
Wherein the compressor is provided with a multi-stage compressor having a plurality of stages,
The evaporator exchanges heat between the liquid refrigerant discharged from the phase separator and the cold water,
A first expansion valve is provided between the condenser and the phase separator, a second expansion valve is provided between the phase separator and the evaporator,
Wherein the control unit determines that the liquid refrigerant is sucked into the compressor based on the evaporation pressure change amount of the refrigerant and the superheating degree of the compressor discharge, the controller controls the first expansion valve and the second expansion valve to lower the liquid refrigerant level in the evaporator. And performs control to reduce the opening degree of at least one or more expansion valves. 9. The method of claim 8,
Wherein the evaporation pressure change amount of the refrigerant is measured at a predetermined time interval. 10. The method of claim 9,
Wherein the first weight for the variation of the present evaporation pressure is less than the second weight for the previous evaporation pressure change and the sum of the first weight and the second weight is one. 11. The method of claim 10,
Wherein the first weight is 0.2. 10. The method of claim 9,
Wherein the control unit controls the opening degree of the expansion valve to decrease when the evaporation pressure change is equal to or less than a predetermined value and the superheating degree of discharge is equal to or lower than a predetermined temperature (A DEG C). 13. The method of claim 12,
Wherein the predetermined value is 0.1, and the predetermined temperature is 2 [deg.] C. 10. The method of claim 9,
The opening value of the expansion valve controlled by the control unit is determined by multiplying the current expansion valve opening value by a weight R determined according to the following equation (2)
Wherein A is the predetermined temperature, B is an experimentally determined arbitrary value between A and 6, and C is a currently measured discharge superheating degree.
&Quot; (2) &quot;

A &lt; = B &lt; = 6 A compressor including an impeller for compressing refrigerant;
A condenser for exchanging heat between the refrigerant introduced from the compressor and the cooling water;
An evaporator for exchanging heat between the refrigerant discharged from the condenser and the cold water;
An expansion valve provided between the condenser and the evaporator; And
A normal control mode for adjusting the opening degree of the expansion valve based on the refrigerant level of the condenser, an evaporation pressure variation amount of the refrigerant and a compressor discharge superheat degree determined by a weighted average of a variation amount of the present evaporation pressure and a variation amount of the previous evaporation pressure And a control unit having emergency control models for controlling the opening degree of the expansion valve to lower the level of the liquid refrigerant in the evaporator if it is determined that the liquid refrigerant is sucked into the compressor,
Wherein the control unit controls the opening degree of the expansion valve to decrease when the evaporation pressure change is equal to or lower than a predetermined value and the superheating degree of discharge is equal to or lower than a predetermined temperature (A DEG C). 16. The method of claim 15,
Further comprising at least two electrostatic capacity sensing sensors located at different heights along the increasing direction of the refrigerant level to sense the refrigerant level inside the condenser in the normal control mode. 16. The method of claim 15,
Wherein the evaporation pressure change amount of the refrigerant is measured at a predetermined time interval. delete 18. The method of claim 17,
The opening value of the expansion valve controlled by the control unit is determined by multiplying the current expansion valve opening value by the weight R determined according to the following equation (3)
Wherein A is the predetermined temperature, B is an experimentally determined arbitrary value between A and the constant 6, and C is the currently measured discharge superheating degree.
&Quot; (3) &quot;

A &lt; = B &lt; = 6 18. The method of claim 17,
Wherein the control unit decreases the opening degree of the expansion valve and operates in a normal control mode when the discharge and the degree of heat are greater than a predetermined temperature (A DEG C) after a predetermined time elapses.

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