JP6340213B2 - Turbo refrigerator - Google Patents

Description

  The present invention relates to a turbo chiller, and more particularly to a turbo chiller that cools an electric motor by introducing a part of refrigerant from a refrigeration cycle to an electric motor that drives the turbo compressor.

  Conventionally, a turbo refrigerator used in a refrigeration air conditioner or the like is configured by a closed system in which a refrigerant is enclosed, an evaporator that takes heat from cold water (fluid to be cooled) and evaporates the refrigerant to exert a refrigeration effect; A compressor that compresses the refrigerant gas evaporated in the evaporator to form a high-pressure refrigerant gas; a condenser that cools and condenses the high-pressure refrigerant gas with cooling water (cooling fluid); and depressurizes the condensed refrigerant. An expansion valve (expansion mechanism) that is expanded by being connected by a refrigerant pipe.

  In many cases, a turbo compressor used in a turbo refrigerator employs a semi-hermetic compressor in which an electric motor is housed in a split casing together with a compressor. In this semi-hermetic compressor, the heat generated due to the loss of the electric motor is often cooled by introducing condensed refrigerant (liquid refrigerant) in the refrigeration cycle into the electric motor and using the latent heat of vaporization of the refrigerant. In this case, the refrigerant is normally sent from the condenser to the electric motor, and the drive source for sending the refrigerant is a pressure difference between the condenser and the electric motor (evaporator).

JP-A-57-95152

  In the expansion process, the condensed refrigerant that has cooled the electric motor is flushed with the refrigerant gas corresponding to the quality (dryness) and returned to the evaporator. To improve the efficiency of turbo chillers, it is also effective to reduce the amount of cooling refrigerant to the motor, but the amount of cooling refrigerant corresponding to the heat generated by the motor is required. As a result, the temperature of the electric motor rises and it becomes difficult to continue normal operation of the refrigerator.

  Although the amount of refrigerant for cooling the heat loss of the motor loss is calculated from the calorific value calculation, when operating the actual refrigerator, the cooling of the motor is required unless a cooling refrigerant amount several times the calculated value is supplied to the motor. There is a risk that the cooling function of the electric motor is impaired by excessively reducing the refrigerant. In the expansion process, the condensed refrigerant that has cooled the electric motor is flushed with the refrigerant gas corresponding to the dryness (quality) and returned to the evaporator. The flushed refrigerant gas is sucked into the compressor without contributing to the refrigeration effect, causing excessive compression power to be consumed, leading to a reduction in efficiency of the refrigerator.

  The present invention has been made in view of the above circumstances, and by using the subcooler supercooled refrigerant liquid as a cooling refrigerant for the electric motor that drives the turbo compressor, the evaporator is flushed and does not contribute to the refrigeration effect. It is an object of the present invention to provide a turbo chiller that can reduce the amount of refrigerant gas and that can secure a stable cooling function of the motor by avoiding flash in the cooling refrigerant piping of the motor.

In order to achieve the above-described object, a turbo refrigerator of the present invention includes an evaporator that takes heat from a fluid to be cooled and evaporates the refrigerant to exert a refrigeration effect, and a multistage turbo compressor that compresses the refrigerant using a multistage impeller. An electric motor that drives the multi-stage turbo compressor, a condenser that cools and condenses the compressed refrigerant gas with a cooling fluid, and evaporates a part of the condensed refrigerant liquid to evaporate the evaporated refrigerant gas. In a turbo chiller equipped with an economizer that is an intermediate cooler that supplies an intermediate part of a multistage compression stage of a compressor, a subcooler that supercools the refrigerant condensed in the condenser, and a refrigerant that is supplied from the economizer to the electric motor A refrigerant supply pipe for supplying refrigerant to the electric motor from the subcooler side, a refrigerant supply from the economizer to the electric motor, and the subcooler side. Characterized by comprising a control device for switching between the refrigerant supply to the motor.
According to the present invention, since the economizer cycle in which the refrigerant gas separated by the economizer is introduced into the middle part of the multistage compression stage of the multistage turbo compressor can be constructed, the refrigeration effect part by the economizer is added. Only the refrigeration effect can be increased and the efficiency can be improved. When the differential pressure between the economizer and the evaporator is large, it is possible to reduce the economizer effect to zero by supplying refrigerant for cooling the motor from the economizer, which is an intermediate pressure. Reduction and efficiency reduction can be prevented.
According to the present invention, when the differential pressure between the economizer and the evaporator is small, the refrigerant for cooling the electric motor can be supplied from the subcooler side.
According to an embodiment of the present invention, an evaporator that takes heat from cold water and evaporates the refrigerant to exert a refrigeration effect, a turbo compressor that compresses the refrigerant with an impeller, an electric motor that drives the turbo compressor, and a compression A subcooler for cooling the refrigerant condensed by the condenser, and a pipe branched from the subcooler side. A refrigerant supply pipe for supplying a refrigerant from the subcooler side to the electric motor, wherein the electric motor is cooled by the refrigerant subcooled by the subcooler, and the turbo refrigerator is further connected to the refrigerant supply pipe. A control valve that is installed and controls the flow rate of refrigerant flowing through the refrigerant supply pipe, and measures the stator core temperature that is linearly related to the rated current ratio of the motor and has a high correlation. A temperature measuring means and a control device for controlling the opening degree of the control valve, wherein the control device measures the temperature based on the relationship between the stator core temperature determined in advance and the opening degree of the control valve. It is to determine the degree of opening of the control valve from the stator core temperature of the motor, that controls the flow rate of refrigerant supplied to the electric motor by controlling the control valve on the determined degree of opening.

According to the above embodiment , by using the refrigerant liquid supercooled by the subcooler for cooling the electric motor, the amount of flash gas at the time of the supercooled refrigerant liquid is reduced, and the refrigerant gas that does not contribute to the refrigeration effect can be reduced. The excess power of the compressor can be reduced and the efficiency of the refrigerator can be avoided.
Also, according to the above embodiment , since the supercooled refrigerant liquid at the outlet of the subcooler is used as the coolant for the electric motor, the refrigerant liquid from the subcooler has already been subcooled to the saturation temperature or lower, so that the piping The risk of flashing due to the pressure loss is reduced, and a stable motor cooling function can be secured.
According to the above embodiment , the internal temperature of the electric motor that drives the turbo compressor is measured during operation of the turbo refrigerator, and the measurement signal is sequentially sent to the control device. The control device controls the opening degree of the control valve based on the measured internal temperature of the electric motor, and controls the flow rate of the condensed refrigerant supplied to the electric motor from the subcooler side through the refrigerant supply pipe. In this way, by optimizing the amount of condensed refrigerant supplied to the electric motor so as to match the amount of heat generated by the electric motor, the electric motor can be properly cooled without excess or deficiency. The gas refrigerant that has finished cooling the electric motor is returned to the evaporator via the return pipe.

According to an embodiment of the present invention, a control valve that is installed in the refrigerant supply pipe and controls the flow rate of the refrigerant flowing through the refrigerant supply pipe, and means for measuring the inlet temperature of cold water that exchanges heat with the refrigerant in the evaporator; And means for measuring the outlet temperature of the cold water after heat exchange with the refrigerant in the evaporator, and a control device for controlling the opening degree of the control valve, the control device comprising the cold water inlet temperature of the evaporator, The refrigerating capacity is calculated from the temperature difference of the chilled water outlet temperature and the flow rate of the chilled water flowing through the evaporator, and the flow rate of the refrigerant supplied to the motor is controlled by controlling the opening of the control valve based on the calculated refrigeration capacity. you control.

According to the above embodiment , the cold water inlet temperature of the evaporator is measured and the cold water outlet temperature of the evaporator is measured while the turbo refrigerator is in operation. These measurement signals are sequentially sent to the control device, and the control device calculates the temperature difference between the cold water inlet and outlet. In the control device, the refrigerating capacity is calculated by multiplying the temperature difference thus obtained by the flow rate of the cold water flowing through the evaporator. At this time, when the chilled water flow rate is the rated flow rate (fixed flow rate), it is not necessary to measure, but when the chilled water flow rate is a variable flow rate, the flow rate measuring means measures to obtain the chilled water flow rate. Since the refrigerant amount of the condensed refrigerant (liquid refrigerant) necessary for cooling the electric motor is determined from the refrigeration capacity calculated in this way, the opening of the control valve is controlled, and the electric motor is connected from the subcooler side via the refrigerant supply pipe. The flow rate of the condensed refrigerant supplied to the is controlled. In this way, by optimizing the amount of condensed refrigerant supplied to the electric motor so as to match the amount of heat generated by the electric motor, the electric motor can be properly cooled without excess or deficiency. The gas refrigerant that has finished cooling the electric motor is returned to the evaporator via the return pipe.

According to the embodiment of the present invention, there is provided means for measuring the flow rate of the cold water flowing through the evaporator .
According to the above embodiment , when the flow rate of the cold water flowing through the evaporator is a variable flow rate, the flow rate is measured by the flow rate measuring means to obtain the cold water flow rate.

According to an embodiment of the present invention, comprising means for measuring the pressure difference between the cold water inlet pressure and the coolant outlet pressure of the evaporator, the control device you calculating the flow rate of cold water flowing through the evaporator from the pressure difference .
According to the above embodiment , a differential pressure gauge is provided between the cold water inlet pipe and the cold water outlet pipe of the evaporator to measure the cold water pressure loss generated in the evaporator, and the flow rate of cold water flowing through the evaporator from the cold water pressure loss of the evaporator Is calculated.

According to the embodiment of the present invention, the control valve that is installed in the refrigerant supply pipe and controls the flow rate of the refrigerant flowing through the refrigerant supply pipe, and the means for measuring the inlet temperature of the cooling water that exchanges heat with the refrigerant in the condenser And means for measuring the outlet temperature of the cooling water after exchanging heat with the refrigerant in the condenser, and a control device for controlling the opening of the control valve, wherein the control device is a cooling water for the condenser. By calculating the cooling water cooling capacity from the temperature difference between the inlet temperature and the cooling water outlet temperature and the flow rate of the cooling water flowing through the condenser, and controlling the opening of the control valve based on the calculated cooling water cooling capacity that controls the flow rate of refrigerant supplied to the electric motor.

According to the above embodiment , the cooling water inlet temperature of the condenser is measured while the turbo refrigerator is in operation, and the cooling water outlet temperature of the condenser is measured. These measurement signals are sequentially sent to the control device, and the control device calculates the temperature difference between the cooling water inlet and outlet. In the control device, the cooling water cooling capacity is calculated by multiplying the temperature difference thus obtained by the cooling water flow rate flowing through the condenser. At this time, when the cooling water flow rate is the rated flow rate (fixed flow rate), it is not necessary to measure, but when the cooling water flow rate is a variable flow rate, the cooling water flow rate is obtained by measuring with the flow rate measuring means. The amount of condensed refrigerant (liquid refrigerant) necessary for cooling the electric motor is determined from the cooling water cooling capacity calculated in this way, so the opening degree of the control valve is controlled and the subcooler side is connected via the refrigerant supply pipe. To control the flow rate of the condensed refrigerant supplied to the electric motor. In this way, by optimizing the amount of condensed refrigerant supplied to the electric motor so as to match the amount of heat generated by the electric motor, the electric motor can be properly cooled without excess or deficiency. The gas refrigerant that has finished cooling the electric motor is returned to the evaporator via the return pipe.

According to an embodiment of the present invention, there is provided means for measuring the flow rate of the cooling water flowing through the condenser .
According to the above embodiment , when the flow rate of the cooling water flowing through the condenser is a variable flow rate, the flow rate is measured by the flow rate measuring means to obtain the cooling water flow rate.

According to an embodiment of the present invention, there is provided means for measuring the pressure difference between the cooling water inlet pressure and the cooling water outlet pressure of the condenser, and the control device determines the flow rate of the cooling water flowing through the condenser from the pressure difference. you arithmetic.
According to the above embodiment , the differential pressure gauge is provided between the cooling water inlet pipe and the cooling water outlet pipe of the condenser to measure the cooling water pressure loss generated in the condenser, and the condenser is determined from the cooling water pressure loss of the condenser. The flow rate of the cooling water flowing through the

According to an embodiment of the present invention, the control valve that is disposed in a position close to the motor.
According to the above embodiment , the mounting position of the electric control valve is preferably as close as possible to the electric motor side in the refrigerant supply pipe. This is because the control valve becomes a throttling mechanism, so that the liquid refrigerant is flushed on the secondary side to form a two-phase flow of the refrigerant, and the refrigerant flow may be hindered.

According to an embodiment of the present invention, the temperature measuring means Ru der thermocouple.

In a preferred aspect of the present invention, the control device performs the switching based on a differential pressure between the economizer and the evaporator.
A preferred embodiment of the present invention includes a pressure sensor that measures the pressure of the economizer and a pressure sensor that measures the pressure of the evaporator, and the control device uses the measurement signals of the two pressure sensors to calculate the economizer and the evaporation. It is characterized in that a differential pressure with the vessel is obtained.

In a preferred aspect of the present invention, when the differential pressure between the economizer and the evaporator is a predetermined value or more, a refrigerant is supplied from the economizer to the electric motor.
According to the present invention, when the differential pressure between the economizer and the evaporator is equal to or greater than a predetermined value, the cooling refrigerant for cooling the electric motor is transported with the differential pressure. The predetermined value is a value calculated from the pipe pressure loss. That is, the predetermined value is a value in consideration of the pipe pressure loss from the economizer to the evaporator, and is a value obtained by adding a margin pressure, for example, 20 kPa to 30 kPa in the case of the refrigerant R134a, to this pipe pressure loss. .

In a preferred aspect of the present invention, when the differential pressure between the economizer and the evaporator is less than a predetermined value, the refrigerant is supplied to the electric motor from the subcooler side.
According to the present invention, when the differential pressure between the economizer and the evaporator is less than a predetermined value, the cooling refrigerant for cooling the motor is transported using the differential pressure between the subcooler and the evaporator.

In a preferred aspect of the present invention, there is provided a vane for controlling an intake air amount of the impeller in an intermediate portion of the multistage compression stage of the multistage turbo compressor.
According to the present invention, the intake air volume of the impeller at the intermediate portion of the multistage compression stage can be reduced by the vane, so that an extreme decrease in the economizer pressure at the time of low head can be prevented. Therefore, a sufficient pressure difference can be secured between the economizer pressure and the evaporation pressure, and stable cooling refrigerant can be supplied from the economizer to the electric motor.

The present invention has the following effects.
(1) By using the subcooler supercooled refrigerant liquid as the refrigerant for cooling the electric motor that drives the turbo compressor, it is possible to reduce the amount of refrigerant gas that does not contribute to the refrigeration effect by flushing with the evaporator. The surplus power of the compressor can be reduced, and the efficiency of the refrigerator can be avoided. In addition, since the refrigerant liquid from the subcooler is already supercooled below the saturation temperature, the risk of flushing due to pressure loss in the piping is reduced, and a stable motor cooling function is achieved by avoiding flushing in the cooling refrigerant piping of the motor. It can be secured.
(2) By optimizing the refrigerant amount of the refrigerant supplied from the refrigeration cycle to the electric motor as the refrigerant for cooling the electric motor that drives the turbo compressor, the electric motor can be properly cooled without excess or deficiency. It is possible to prevent a decrease in efficiency.
(3) In the economizer cycle provided with the economizer, the liquid refrigerant supplied for cooling the electric motor does not become excessive, and therefore, the situation where the liquid refrigerant returns to the evaporator does not occur. Therefore, the reduction in the economizer effect can be suppressed or made zero, and the efficiency of the refrigerator can be improved.

FIG. 1 is a schematic diagram showing a first embodiment of a turbo refrigerator according to the present invention. FIG. 2 is a schematic view showing a second embodiment of the turbo refrigerator according to the present invention. FIG. 3 is a Mollier diagram for comparing the amount of gas generated by flushing with an evaporator. FIG. 4 is a schematic diagram showing a third embodiment of a turbo refrigerator according to the present invention. FIG. 5 is a graph showing the relationship between the refrigeration capacity and the opening of the electric control valve. FIG. 6 is a schematic diagram showing a fourth embodiment of a turbo refrigerator according to the present invention. FIG. 7 is a schematic view showing a fifth embodiment of a turbo refrigerator according to the present invention. FIG. 8 is a graph showing the relationship between the rated current ratio (%) of the motor and the temperature inside the motor. FIG. 9 is a schematic view showing a sixth embodiment of a turbo refrigerator according to the present invention. FIG. 10 is a Mollier diagram when the cooling water temperature is low and the head is low. FIG. 11 is a Mollier diagram in the case where the pressure difference between the economizer pressure and the evaporation pressure is increased by narrowing the suction air volume of the second stage impeller by using the suction vane at the time of the low head where the cooling water temperature is low.

Hereinafter, embodiments of a turbo refrigerator according to the present invention will be described with reference to FIGS. 1 to 11. In FIG. 1 to FIG. 11, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted.
FIG. 1 is a schematic diagram showing a first embodiment of a turbo refrigerator according to the present invention. As shown in FIG. 1, a turbo refrigerator includes a turbo compressor 1 that compresses refrigerant, a condenser 2 that cools and compresses the compressed refrigerant gas with cooling water (cooling fluid), and cold water (cooled fluid). ), An evaporator 3 that evaporates the refrigerant and exerts a refrigeration effect, and an economizer 4 that is an intermediate cooler disposed between the condenser 2 and the evaporator 3. Are connected by a refrigerant pipe 5 that circulates.

  In the embodiment shown in FIG. 1, the turbo compressor 1 is composed of a multistage turbo compressor and is driven by an electric motor 11. The turbo compressor 1 is a semi-hermetic turbo compressor in which an electric motor 11 is housed together with a compressor in a split casing. The turbo compressor 1 is connected to the economizer 4 by a flow path 8, and the refrigerant gas separated by the economizer 4 is an intermediate portion (in this example, two stages) of the multi-stage compression stage (two stages in this example) of the turbo compressor 1. It is introduced in the part between the first stage and the second stage). The condenser 2 is a shell-and-tube condenser having a subcooler SC built in at the bottom.

  In the refrigeration cycle of the turbo chiller configured as shown in FIG. 1, the refrigerant circulates through the turbo compressor 1, the condenser 2, the evaporator 3, and the economizer 4, and chilled water is generated by the cold heat source obtained by the evaporator 3. The amount of heat from the evaporator 3 that is manufactured and corresponds to the load and taken into the refrigeration cycle and the amount of heat corresponding to the work of the turbo compressor 1 supplied from the electric motor 11 are released to the cooling water supplied to the condenser 2. Is done. On the other hand, the refrigerant gas separated by the economizer 4 is introduced into an intermediate portion of the multistage compression stage of the turbo compressor 1, merged with the refrigerant gas from the first stage compressor, and compressed by the second stage compressor. According to the two-stage compression single-stage economizer cycle, since the refrigeration effect portion by the economizer 4 is added, the refrigeration effect is increased by that amount, and the efficiency of the refrigeration effect is improved as compared with the case where the economizer 4 is not installed. Can do.

  As shown in FIG. 1, a refrigerant supply pipe 5BP is installed that branches from a refrigerant pipe 5 that connects the subcooler SC and the economizer 4 at the bottom of the condenser 2 and guides the refrigerant from the subcooler SC to the electric motor 11. Yes. The refrigerant supply pipe 5BP is connected to the casing 11c of the electric motor 11, and the supercooled refrigerant liquid is introduced into the casing 11c of the electric motor 11 from the subcooler SC. The refrigerant introduced into the casing 11c of the electric motor 11 evaporates while flowing in the casing 11c, and uses the latent heat of evaporation at this time to take away the heat of the electric motor 11 to cool the electric motor 11.

FIG. 2 is a schematic view showing a second embodiment of the turbo refrigerator according to the present invention. As shown in FIG. 2, in this embodiment, the subcooler is not a built-in type but an external subcooler SC. The external subcooler SC is composed of a plate heat exchanger or the like. Other configurations are the same as those of the turbo refrigerator shown in FIG.
Also, in the turbo chillers according to the third to sixth embodiments shown below, both types of built-in subcoolers and external subcoolers can be used. Only the case of using the subcooler is illustrated.

In the turbo chiller configured as shown in FIGS. 1 and 2, the supercooled refrigerant liquid at the outlet of the subcooler SC is used as a coolant for the electric motor 11. The merit of using the supercooled refrigerant liquid at the outlet of the subcooler as a coolant for the electric motor is as follows.
That is, after the refrigerant liquid supercooled by the subcooler SC is used for cooling the electric motor 11, the refrigerant liquid returned to the evaporator 3 is flushed and becomes wet steam, but the condenser → electric motor → evaporator cooling path Since the dryness (quality) is low, the amount of gas generated by flushing with the evaporator 3 is reduced.

FIG. 3 is a Mollier diagram for comparing the amount of gas generated by flushing with an evaporator. From the Mollier diagram shown in FIG. 3, the amount of flash gas when the supercooled refrigerant liquid at the subcooler outlet is used as the coolant for the motor and when the saturated refrigerant liquid at the condenser outlet is used as the coolant for the motor is as follows: It is expressed as
Flash gas amount in supercooled refrigerant liquid = (Δh1 / Δh) × G
Flash gas amount at saturated refrigerant liquid = (Δh2 / Δh) × G
G: Supply amount of cooling refrigerant to the motor [kg / s]
When the refrigerant liquid supercooled by the subcooler SC is used for cooling the electric motor 11 in this way, the amount of flash gas at the time of the supercooled refrigerant liquid is reduced, and the refrigerant gas that does not contribute to the refrigeration effect can be reduced. The surplus power of the compressor can be reduced, and the efficiency of the refrigerator can be avoided.

In addition, when the saturated condensate from the condenser 2 is used as a refrigerant and the pressure difference between the condenser 2 and the evaporator 3 is used as a drive source and supplied to the electric motor 11, the pressure loss of the supply pipe is large (for example, a filter, a sight glass, etc. When the squeezing mechanism is provided, the refrigerant liquid is flushed and the inside of the cooling refrigerant pipe becomes a two-phase flow. If it becomes a two-phase flow, supply of a cooling refrigerant | coolant will be inhibited and the cooling function of the electric motor 11 may be impaired.
However, according to the present invention, since the supercooled refrigerant liquid at the outlet of the subcooler SC is used as the coolant for the electric motor 11, the refrigerant liquid from the subcooler SC has already been subcooled below the saturation temperature. The risk of flushing due to pressure loss in the piping is reduced, and a stable motor cooling function can be ensured.

  FIG. 4 is a schematic diagram showing a third embodiment of a turbo refrigerator according to the present invention. As shown in FIG. 4, a refrigerant supply pipe 5 </ b> BP that branches from the refrigerant pipe 5 that connects the subcooler SC and the economizer 4 at the bottom of the condenser 2 and guides the refrigerant from the subcooler SC to the electric motor 11 is installed. Yes. The refrigerant supply pipe 5BP is connected to the casing 11c of the electric motor 11, and the supercooled refrigerant liquid is introduced into the casing 11c of the electric motor 11 from the subcooler SC. The refrigerant introduced into the casing 11c of the electric motor 11 evaporates while flowing in the casing 11c, and uses the latent heat of evaporation at this time to take away the heat of the electric motor 11 to cool the electric motor 11.

As shown in FIG. 4, the evaporator 3 is provided with a temperature sensor T1 for measuring the cold water inlet temperature and a temperature sensor T2 for measuring the cold water outlet temperature. That is, the temperature sensor T1 measures the inlet temperature of cold water that exchanges heat with the refrigerant in the evaporator 3, and the temperature sensor T2 measures the outlet temperature of cold water after heat exchange with the refrigerant in the evaporator 3. ing. The temperature sensor T1 and the temperature sensor T2 are connected to the control device 10, respectively. Thereby, in the control apparatus 10, the refrigerating capacity Qe can be calculated from the temperature difference between the cold water inlet temperature and the cold water outlet temperature and the rated (fixed) cold water flow rate. When the flow rate of cold water flowing through the evaporator 3 is a variable flow rate, as shown in FIG. 4, by providing a flow rate sensor FE for measuring the flow rate of cold water in the cold water outlet pipe, the temperature between the cold water inlet temperature and the cold water outlet temperature. The refrigeration capacity Qe can be calculated by multiplying the difference by the cold water flow rate measured by the flow rate sensor FE.
As shown in FIG. 4, a differential pressure gauge ΔPe is provided between the cold water inlet pipe and the cold water outlet pipe to measure the cold water pressure loss generated in the evaporator 3, and the evaporator 3 is determined from the cold water pressure loss of the evaporator 3. The refrigeration capacity Qe may be calculated by estimating the flowing cold water flow rate and multiplying the estimated cold water flow rate by the temperature difference between the cold water inlet temperature and the cold water outlet temperature.

Next, the operation of the turbo refrigerator configured as shown in FIG. 4 will be described.
During operation of the turbo refrigerator, the temperature sensor T1 measures the cold water inlet temperature and the temperature sensor T2 measures the cold water outlet temperature. These measurement signals are sequentially sent to the control device 10, and the control device 10 calculates the temperature difference between the chilled water inlet and outlet. The control device 10 calculates the refrigerating capacity Qe by multiplying the temperature difference thus obtained and the flow rate of cold water flowing through the evaporator 3. At this time, when the chilled water flow rate is a rated flow rate (fixed flow rate), it is not necessary to measure, but when the chilled water flow rate is a variable flow rate, the flow rate sensor FE measures to obtain the chilled water flow rate. Since the refrigerant quantity of the condensed refrigerant (liquid refrigerant) necessary for cooling the electric motor 11 is determined from the refrigeration capacity Qe calculated in this way, the opening degree of the electric control valve 12 is controlled, and the refrigerant from the subcooler SC is obtained. The flow rate of the condensed refrigerant supplied to the electric motor 11 through the supply pipe 5BP is controlled.

  FIG. 5 is a graph showing the relationship between the refrigerating capacity Qe and the opening degree of the electric control valve 12. If the relationship between the refrigerating capacity Qe and the opening degree of the electric control valve 12 as shown in FIG. 5 is obtained in advance and tabulated, and the refrigerating capacity Qe is calculated, the electric control valve 12 is immediately obtained. Can be determined.

  In this way, by optimizing the refrigerant amount of the condensed refrigerant supplied to the electric motor 11 so as to match the calorific value of the electric motor 11, the electric motor 11 can be properly cooled without excess or deficiency. The gas refrigerant that has finished cooling the electric motor 11 is returned to the evaporator 3 via a return pipe (not shown).

FIG. 6 is a schematic diagram showing a fourth embodiment of a turbo refrigerator according to the present invention. As shown in FIG. 6, in the present embodiment, various sensors are installed in the condenser 2. Other configurations are the same as those of the turbo refrigerator shown in FIG. That is, the condenser 2 is provided with a temperature sensor T1 for measuring the cooling water inlet temperature and a temperature sensor T2 for measuring the cooling water outlet temperature. The temperature sensors T1 and T2 are connected to the control device 10, respectively. Thereby, the control device 10 can calculate the cooling water cooling capacity Qc from the temperature difference between the cooling water inlet temperature and the cooling water outlet temperature and the rated (fixed) cooling water flow rate. When the flow rate of the cooling water flowing through the condenser 2 is a variable flow rate, as shown in FIG. 6, by providing a flow rate sensor FC for measuring the flow rate of the cooling water in the cooling water outlet pipe, the cooling water inlet temperature and the cooling water The cooling water cooling capacity Qc can be calculated by multiplying the temperature difference from the outlet temperature by the cooling water flow rate measured by the flow rate sensor FC.
As shown in FIG. 6, a differential pressure gauge ΔPc is provided between the cooling water inlet pipe and the cooling water outlet pipe to measure the cooling water pressure loss generated in the condenser 2, and from the cooling water pressure loss of the condenser 2. The cooling water flow rate flowing through the condenser 2 is estimated, and the cooling water cooling capacity Qc may be calculated by multiplying the estimated cooling water flow rate by the temperature difference between the cooling water inlet temperature and the cooling water outlet temperature.

  Since the refrigerant amount of the condensed refrigerant (liquid refrigerant) necessary for cooling the electric motor 11 is determined from the cooling water cooling capacity Qc calculated in this way, the opening degree of the electric control valve 12 is controlled, and the subcooler SC. The flow rate of the condensed refrigerant supplied to the electric motor 11 via the refrigerant supply pipe 5BP is controlled. In addition, the relationship between the cooling water cooling capacity Qc and the opening degree of the electric control valve 12 is obtained in advance as in FIG.

FIG. 7 is a schematic view showing a fifth embodiment of a turbo refrigerator according to the present invention.
As shown in FIG. 7, there is installed a refrigerant supply pipe 5BP that branches from the refrigerant pipe 5 that connects the subcooler SC and the economizer 4 at the bottom of the condenser 2 and guides the refrigerant from the subcooler SC to the electric motor 11. Yes. The refrigerant supply pipe 5BP is connected to the casing 11c of the electric motor 11, and the refrigerant condensed by the condenser 2 is introduced into the casing 11c of the electric motor 11. The refrigerant supply pipe 5BP is provided with an electric control valve 12, and the flow rate of the refrigerant can be controlled by controlling the opening degree of the control valve 12. The control valve 12 is connected to the control device 10. The refrigerant introduced into the casing 11c of the electric motor 11 evaporates while flowing in the casing 11c, and uses the latent heat of evaporation at this time to take away the heat of the electric motor 11 to cool the electric motor 11. The refrigerant gas after cooling the electric motor 11 returns to the evaporator 3. The mounting position of the electric control valve 12 is preferably as close as possible to the motor side in the refrigerant supply pipe 5BP. This is because the control valve 12 serves as a throttling mechanism, so that the liquid refrigerant is flushed on the secondary side to form a two-phase flow of the refrigerant, which may impede the flow of the refrigerant.

  As shown in FIG. 7, the electric motor 11 is provided with a temperature sensor T that measures the temperature inside the electric motor. The temperature sensor T uses, for example, a thermocouple, and the temperature sensor has a detection end that can measure the temperature of the highest temperature inside the motor. The temperature sensor T is connected to the control device 10.

Next, the operation of the turbo refrigerator configured as shown in FIG. 7 will be described.
During operation of the turbo refrigerator, the temperature inside the electric motor 11 is measured by the temperature sensor T. The measurement signal of the temperature sensor T is sequentially sent to the control device 10. Based on the measurement signal of the temperature sensor T, the control device 10 proportionally controls the opening of the electric control valve 12 so that the inside of the electric motor reaches a predetermined temperature. Here, the predetermined temperature is a temperature determined from the specifications of the electric motor (temperature with a margin provided for the insulation grade). In this way, by performing proportional control of the opening degree of the electric control valve 12, the minimum condensed refrigerant (liquid refrigerant) necessary for efficiently cooling the heat generated by the electric motor determined by the operating conditions (load) of the refrigerator. This amount of refrigerant can be supplied to the electric motor 11. Therefore, the electric motor 11 can be properly cooled without excess or deficiency, and a reduction in efficiency of the refrigerator can be prevented.

  The temperature sensor T needs to measure the temperature of the highest temperature inside the electric motor, and is preferably installed at a location where the correlation between the measured temperature and the rated current ratio of the electric motor is high. Therefore, the present inventors have installed a plurality of thermocouples at the positions of the stator core and the stator coil end, and investigated the correlation between the measured temperature and the rated current ratio of the motor.

FIG. 8 is a graph showing the relationship between the rated current ratio (%) of the motor and the temperature inside the motor. In FIG. 8, the motor temperature is the temperature when cooling is performed by supplying the refrigerant from the condenser side. In FIG. 8, the white squares indicate the relationship between the stator coil end temperature measured by the thermocouple and the rated current ratio, and the black squares indicate the relationship between the stator core temperature measured by the thermocouple and the rated current ratio.
As shown in FIG. 8, the stator core temperature and the rated current ratio are in a linear relationship and show a high correlation, but the stator coil end temperature and the rated current ratio have a poor correlation and vary. Therefore, it is preferable that the temperature sensor T is installed at a position where the stator core temperature can be measured, and the representative temperature of the electric motor is the stator core temperature or a temperature near the stator core.

  In the present invention, the relationship between the temperature of the stator core measured by the temperature sensor T or the temperature in the vicinity of the stator core and the opening of the electric control valve 12 is obtained in advance and tabulated, so that the measurement by the temperature sensor T is performed. The opening degree of the electric control valve 12 can be determined immediately from the temperature.

  According to the present invention, the temperature of the stator core or the temperature near the stator core is measured by the temperature sensor T, and the opening degree of the electric control valve 12 is controlled based on the measured temperature, whereby the refrigerant of the condensed refrigerant supplied to the electric motor 11 is obtained. The amount can be optimized to match the amount of heat generated by the electric motor 11, and the electric motor 11 can be properly cooled without being excessive or insufficient. The gas refrigerant that has finished cooling the electric motor 11 is returned to the evaporator 3 via a return pipe (not shown).

FIG. 9 is a schematic view showing a sixth embodiment of a turbo refrigerator according to the present invention.
As shown in FIG. 9, a refrigerant supply pipe 5 </ b> BP <b> 1 that branches from the refrigerant pipe 5 that connects the economizer 4 and the evaporator 3 and guides the refrigerant from the economizer 4 to the electric motor 11 is installed. The refrigerant supply pipe 5BP1 is connected to the casing 11c of the electric motor 11, and the refrigerant is introduced into the casing 11c of the electric motor 11. The refrigerant supply pipe 5BP1 that connects the economizer 4 and the electric motor 11 is provided with an electric control valve 13, and is supplied from the economizer 4 to the electric motor 11 by controlling the opening degree of the control valve 13. The flow rate of the refrigerant can be controlled. The control valve 13 is connected to the control device 10.

The driving force for supplying the cooling refrigerant to the electric motor 11 is a pressure difference between the economizer 4 and the evaporator 3. When the cooling water temperature is low and the head is low, the pressure difference between the economizer 4 and the evaporator 3 is small.
FIG. 10 is a Mollier diagram when the cooling water temperature is low and the head is low. As shown in FIG. 10, when the pressure difference between the economizer pressure and the evaporation pressure is small, the driving force for supplying the cooling refrigerant is lowered, and it becomes difficult to supply the cooling refrigerant to the motor 11, and the cooling refrigerant is supplied from the economizer 4. Can not do.

  Therefore, in the present invention, as shown in FIG. 9, a suction vane SV for controlling the suction air volume of the second stage impeller in the second stage compressor is provided. The suction vanes SV are arranged in a radial pattern, and the opening degree of the suction vane SV is changed by rotating the suction vanes SV by a predetermined angle around the axis of the suction vanes SV. Thus, by changing the opening degree of the suction vane SV, the suction air volume of the second stage impeller in the second stage compressor can be controlled, and the suction air volume of the second stage impeller is reduced when the head is low. As a result, it is possible to prevent an extreme decrease in the economizer pressure when the head is low. Therefore, a sufficient pressure difference can be ensured between the economizer pressure and the evaporation pressure, and stable cooling refrigerant can be supplied from the economizer 4 to the electric motor 11.

  FIG. 11 is a Mollier diagram in the case where the pressure difference between the economizer pressure and the evaporation pressure is increased by narrowing the suction air volume of the second stage impeller by using the suction vane SV at the time of the low head where the cooling water temperature is low. As shown in FIG. 11, by increasing the pressure difference between the economizer pressure and the evaporation pressure, it is possible to supply a stable cooling refrigerant from the economizer 4 to the electric motor 11.

  As shown in FIG. 9, a refrigerant supply pipe 5BP2 that branches from the refrigerant pipe 5 connecting the subcooler SC and the economizer 4 at the bottom of the condenser 2 and guides the refrigerant from the subcooler SC to the electric motor 11 is installed. Yes. The refrigerant supply pipe 5BP2 is connected to the refrigerant supply pipe 5BP1. The refrigerant supply pipe 5BP2 is provided with an electric control valve 14. By controlling the opening degree of the control valve 14, the flow rate of the refrigerant supplied from the subcooler SC to the electric motor 11 can be controlled. Yes. The control valve 14 is connected to the control device 10. As shown in FIG. 9, the refrigerant supply pipes 5BP1 and 5BP2 and the electric control valves 13 and 14 are provided so that the cooling refrigerant for the electric motor 11 can be taken out from both the economizer 4 and the subcooler SC.

  As shown in FIG. 9, the evaporator 3 and the economizer 4 are provided with pressure sensors Pe and Peco, respectively. That is, the pressure in the evaporator 3 is measured by the pressure sensor Pe, and the pressure of the economizer 4 is measured by the pressure sensor Peco. The pressure sensor Pe and the pressure sensor Peco are each connected to the control device 10. Thereby, in the control apparatus 10, the pressure of the economizer 4 and the pressure of the evaporator 3 can always be compared.

Next, the operation of the turbo refrigerator configured as shown in FIG. 9 will be described.
During the operation of the turbo refrigerator, the pressure of the evaporator 3 is measured by the pressure sensor Pe and the pressure of the economizer 4 is measured by the pressure sensor Peco. These measurement signals are sequentially sent to the control device 10. The control device 10 compares the pressure (Peco) of the economizer 4 with the pressure (Pe) of the evaporator 3 and performs the following control.
1) When Peco ≧ Pe + α, the control valve 13 is opened and the control valve 14 is closed, whereby the cooling refrigerant is supplied from the economizer 4 to the electric motor 11.
2) When Peco <Pe + α, the control valve 13 is closed and the control valve 14 is opened, whereby the cooling refrigerant is supplied from the subcooler SC to the electric motor 11.
In 1) and 2), α (predetermined value) is a value obtained by adding a margin pressure to a value calculated from the pipe pressure loss.

In the present invention, when the differential pressure between the economizer 4 and the evaporator 3 is equal to or greater than a predetermined value, the cooling refrigerant for cooling the electric motor 11 is transported with the differential pressure. According to the present invention, since the cooling refrigerant for cooling the electric motor 11 is transported using the differential pressure between the economizer 4 and the evaporator 3, the driving force (driving force) for transporting the cooling refrigerant is reduced. Can do. Therefore, it is possible to prevent the refrigerant amount of the refrigerant that cools the electric motor 11 from becoming excessive. In order to ensure the differential pressure between the economizer 4 and the evaporator 3, a vane SV that controls the suction air volume of the second stage impeller of the turbo refrigerator 1 is provided.
When the differential pressure between the economizer 4 and the evaporator 3 is less than a predetermined value, the cooling refrigerant for cooling the electric motor 11 is transported using the differential pressure between the subcooler SC and the evaporator 3.

  In the embodiment shown in FIG. 9, the pressure sensors Pe and Peco are installed in the evaporator 3 and the economizer 4, respectively, but instead of the pressure sensor, temperature sensors may be installed in the evaporator 3 and the economizer 4, respectively. Good. That is, if the economizer temperature and the evaporation temperature are measured, the pressure of the economizer 4 is estimated from the economizer temperature, and the pressure of the evaporator 3 is estimated from the evaporation temperature, the same control as the above 1) and 2) can be performed. it can.

  Although the embodiment of the present invention has been described so far, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention may be implemented in various different forms within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 1 Turbo compressor 2 Condenser 3 Evaporator 4 Economizer 5 Refrigerant piping 5BP Refrigerant supply piping 6 Electric control valve 8 Flow path 10 Control device 11 Electric motor 11c Casing 12 Control valve 13 Control valve 14 Control valve FC, FE Flow rate sensor ΔPc , ΔPe Differential pressure gauge T1, T2 Temperature sensor SC Subcooler

Claims (6)

An evaporator that draws heat from the fluid to be cooled and evaporates the refrigerant to exert a refrigeration effect, a multi-stage turbo compressor that compresses the refrigerant with a multi-stage impeller, an electric motor that drives the multi-stage turbo compressor, A condenser that cools and condenses the refrigerant gas with a cooling fluid, and an intermediate cooler that evaporates a part of the condensed refrigerant liquid and supplies the evaporated refrigerant gas to an intermediate portion of the multistage compression stage of the multistage turbo compressor. In a turbo chiller equipped with an economizer,
A subcooler for supercooling the refrigerant condensed in the condenser;
A refrigerant supply pipe for supplying refrigerant from the economizer to the electric motor;
A refrigerant supply pipe for supplying refrigerant to the electric motor from the sub-cooler side;
A turbo refrigeration machine comprising: a control device that switches between refrigerant supply from the economizer to the electric motor and refrigerant supply from the subcooler side to the electric motor. The turbo chiller according to claim 1 , wherein the control device performs the switching based on a differential pressure between the economizer and the evaporator. A pressure sensor for measuring the pressure of the economizer and a pressure sensor for measuring the pressure of the evaporator; and the control device obtains a differential pressure between the economizer and the evaporator from measurement signals of the two pressure sensors. The turbo refrigerator according to claim 2 . The turbo refrigerator according to claim 2 , wherein when the differential pressure between the economizer and the evaporator is equal to or greater than a predetermined value, a refrigerant is supplied from the economizer to the electric motor. The turbo chiller according to claim 2 , wherein when the differential pressure between the economizer and the evaporator is less than a predetermined value, a refrigerant is supplied to the electric motor from the subcooler side. The turbo chiller according to any one of claims 1 to 5 , further comprising a vane that controls an intake air amount of an impeller at an intermediate portion of the multistage compression stage of the multistage turbo compressor.

Images