JP5010364B2 - Heat source machine and control method thereof, heat source system and operation method thereof - Google Patents

Description

  The present invention relates to a heat source machine, for example, a turbo refrigerator and a control method thereof, and a heat source system and an operation method thereof.

  As a refrigerator used for supplying cold water in a large-scale clean room of a semiconductor manufacturing factory, a turbo refrigerator (a large-capacity heat source machine) that compresses a refrigerant by a turbo compressor is frequently used. An inlet vane (a pre-rotation vane for capacity control) for adjusting the amount of sucked refrigerant gas is provided at the refrigerant gas suction port of the turbo compressor. The control unit of the turbo chiller maintains the outlet temperature of the cold water supplied to the external load constant by adjusting the angle (opening) of the inlet vane (see Patent Document 1). For example, when the chilled water temperature required by the external load is 7 ° C. (set chilled water outlet temperature), control is performed to maintain this 7 ° C. In addition, the chilled water temperature difference between the chilled water outlet temperature and the chilled water inlet temperature has a set value of a predetermined specification. When the chilled water temperature difference is the set value, the turbo chiller load is designed to be 100%. Yes. For example, when the set cold water outlet temperature is 7 ° C. and the cold water temperature difference at 100% load is 5 ° C., the cold water inlet temperature at 100% load is 12 ° C.

No. 5-10186

  As in the winter, when the outside air temperature is low, the load required for the turbo chiller becomes small and may be less than 10%. When the load is 10%, the cold water temperature difference is 0.5 ° C. (5 ° C. × 10% = 0.5 ° C.). When the chilled water temperature difference is 0.5 ° C. or less, accurate control becomes difficult due to the limit of the accuracy of the thermometer that measures the chilled water outlet temperature and the chilled water inlet temperature. For example, when a resistance temperature detector (JIS A class) is used for the thermometer, the accuracy of the resistance temperature detector is ± 0.1 ° C., and the error of the converter is ± 0.1 ° C. Therefore, one thermometer has an error of ± 0.2 ° C, and the error of the two thermometers is superimposed to measure the temperature difference between the chilled water outlet and the chilled water inlet. Measurement error is assumed. Therefore, if the load on the turbo chiller is less than 10% and the chilled water temperature difference is less than 0.5 ° C, the control is within the error range of the thermometer, making it difficult to control the temperature by continuous operation. The operation is performed in a low load mode that temporarily stops (low load stop) and repeats start and stop while confirming the re-rise of the chilled water temperature. However, when the operation of the compressor becomes intermittent, the temperature of the chilled water greatly fluctuates due to a rise in the temperature of the chilled water after the stop or a fluctuation in the temperature of the chilled water when starting up again. Therefore, there is a demand for a turbo refrigerator that can be operated continuously without stopping the compressor even at a low load.

  In addition, when a new heat source system including a turbo chiller is newly constructed, an adjustment operation including the turbo chiller is performed at the initial stage of completion. Generally, facilities are installed so as to be able to cope with the summertime when the demand for cold energy is large, so the installation time of the centrifugal chiller is the winter season. In winter, the outside air temperature is low and the load on the heat source system is small, often far below the 10% load. With this, since the continuous operation cannot be performed as described above, the adjustment operation cannot be performed. Therefore, in practice, a boiler or the like is temporarily introduced for adjustment operation to create a cooling load. Since the boiler introduced at this time is used only for the adjustment operation, it is removed after the adjustment operation is completed. This increases the introduction cost of the centrifugal chiller. Therefore, there is a demand for a turbo chiller that can be operated continuously even at a low load and that can be adjusted without introducing a separate boiler.

In addition, since the outside air is dry in winter, the outside air introduced into the clean room is also dry and does not need to be dehumidified. However, when it rains temporarily like street rain, the humidity of the outside air introduced into the clean room rapidly rises, so it is necessary to dehumidify. Fluctuation of humidity in the clean room, it is necessary to Ru is stabilized to influence the quality of a semiconductor product is manufactured in a clean room. Its dehumidifying operation by the cold water supply of the turbo chiller in this is carried out. However, since a predetermined time is required to start up the centrifugal chiller that is stopped for dehumidification, it cannot sufficiently cope with the humidity increase caused by rain. Accordingly, there is a demand for a turbo chiller that can perform a standby operation at a low load so that it can immediately cope with a cooling load due to dehumidification.

  As described above, a continuous operation at a low load is desired for a turbo refrigerator due to various circumstances. However, when the operation is performed at a low load, the opening degree of the inlet vane that adjusts the suction gas refrigerant flow rate of the compressor becomes excessively small and falls below an appropriate control range. On the other hand, load control is performed by bypassing a part of the refrigerant discharged from the compressor from the condenser and the evaporator and returning it to the suction side of the compressor (hot gas bypass). However, as a result of intensive studies by the present inventors, when the opening control setting of the hot gas bypass valve suitable for a low load is used, the hot gas bypass valve is increased when the load increases and becomes a normal load exceeding the low load. The problem was found that even in areas where it is not necessary to open and control, it becomes open and the efficient operation of the refrigerator is impaired.

  In addition, when adopting a method of cooling a compressor electric motor, lubricating oil, or the like with a refrigerant, the cooling refrigerant is caused to flow using a pressure difference between the condenser and the evaporator. However, when the outside air temperature is low as in winter, the pressure in the condenser does not rise to a desired value, and there may be a place where the cooling refrigerant system in the compressor lacks an appropriate pressure balance.

This invention is made | formed in view of such a situation, Comprising: For example, it aims at providing the heat source machine which can be drive | operated continuously, even if it is a low load less than 10% load.
It is another object of the present invention to provide a heat source machine that can perform standby operation at a low load lower than, for example, 10% load.
It is another object of the present invention to provide a heat source device having a hot gas bypass valve opening degree control that realizes an appropriate inlet vane opening degree in low load operation.
It is another object of the present invention to provide a heat source device that maintains the balance of the cooling refrigerant properly even when the condensation pressure is reduced.

In order to solve the above-described problems, the heat source machine and the control method thereof, and the heat source system and the operation method thereof employ the following means.
That is, a heat source device according to the present invention includes a compressor that compresses a refrigerant, an inlet vane that adjusts a suction refrigerant flow rate of the compressor, a condenser that condenses the refrigerant compressed by the compressor,
An expansion valve that expands the refrigerant condensed by the condenser; an evaporator that evaporates the refrigerant expanded by the expansion valve; and a cold water pipe that supplies cold water heat-exchanged by the evaporator to an external load; A hot gas bypass pipe provided between the refrigerant discharge side and the refrigerant suction side of the compressor, bypassing the condenser and the evaporator, and provided with a hot gas bypass valve, and supplied to the external load And a control unit that controls the inlet vane so that the temperature of the chilled water becomes a set temperature, and the control unit is obtained from the rotation speed of the compressor, the refrigerating capacity, the refrigerant condensing pressure, the refrigerant evaporating pressure, and the like. It is an opening degree of the hot gas bypass valve in each opening of the inlet guide vanes based on the characteristics of the compressor in the heat source unit for calculating a normal operation opening, the control unit, the hot gas bypass A normal operation mode for controlling the inlet guide vanes without opening the front Kigaibu when the load being outputted to the load becomes lower predetermined low load range than the normal operation mode, the opening of the hot gas bypass valve It controls the degree, low load mode and the even lower super low load range than the low load range load output to the external load hot gas controlled by repeating the stopping and starting of the heat source equipment The operation is continued while controlling the opening of the bypass valve, and when the lower limit value of the ultra-low load range is reached, the heat source machine is stopped, and the hot in the ultra-low load mode The opening degree of the gas bypass valve is an opening degree for very low load that is larger than the normal calculation opening degree.

When the load required by the external load on the heat source device decreases and becomes, for example, in the range of 20% to 10% (low load range), the control unit temporarily stops and temporarily starts the compressor. Repeat the operation and control to achieve the set cold water outlet temperature. In this way, a low load mode that repeats stop and start of the compressor when the load is low is provided to cope with the low load.
Further, even if the load required by the external load to the heat source device is lower than the low load range and is, for example, 10% to 0% (super low load range), the operation of the compressor is continued, and the heat source device An ultra-low load mode is provided in which the heat source unit is stopped when the temperature of the cold water inlet falls below the minimum temperature at an ultra-low load exceeding the minimum allowable reference temperature of the installed heat source system. In this ultra-low load mode, the heat source machine is not stopped even when the load falls below the low load range, and the heat source machine is stopped only when the cold water inlet temperature or the cold water outlet temperature falls below the minimum temperature during the ultra low load. That is, the mode in which the heat source machine is difficult to stop and can be continuously operated even when the load is low is achieved.

On the other hand, the hot gas bypass pipe is provided between the refrigerant discharge side and the refrigerant suction side of the compressor, and causes a part of the refrigerant discharged from the compressor to flow to bypass the condenser and the evaporator. Since the refrigerant flowing through the hot gas bypass pipe does not perform refrigeration work (becomes a circulation loss), load control of the heat source unit is performed by controlling the flow rate through the hot gas bypass pipe with the hot gas bypass valve. The opening of the hot gas bypass valve is calculated by calculating the required values according to the physical properties of the refrigerant from the condensing pressure, evaporating pressure, compressor speed, and refrigeration capacity (obtained from the chilled water inlet / outlet temperature and chilled water flow rate). Compared with (internal data), it is calculated as the minimum opening (normal calculation opening) of the required hot gas bypass valve. Since the characteristics of the compressor differ depending on the opening degree of the inlet vane, the normal calculation opening degree is determined for each opening degree of the inlet vane.
In the present invention, the opening of the hot gas bypass valve in the ultra-low load mode is set to an opening larger than the normal calculation opening (opening for ultra-low load). It will flow to the bypass pipe. Thereby, since a circulation loss becomes large, control is performed so that the opening degree of the inlet vane is greatly opened in order to obtain a necessary refrigeration output. The smaller the opening degree of the inlet vane, the larger the control range of the compressor suction refrigerant flow rate, that is, the adjustment resolution of the suction refrigerant is remarkably lowered in the small opening range. Therefore, it is possible to maintain the appropriate control range of the inlet vane even in the ultra-low load mode, where the load is lower than in the low-load mode and it is difficult to continue operation. Can do.

  Note that the low load mode and the ultra low load mode may be selected alternatively, and as described later, the low load mode and the ultra low load mode are continuously selected according to the load change. You may make it connect to.

Furthermore, according to the heat source apparatus of the present invention, the difference between said normal operation opening the ultra-low load opening, the said small as going to the upper limit value from the lower limit value of the ultra-low load range ultra-low-load The use opening is brought close to the normal calculation opening .

  The load increases as the value goes from the lower limit value to the upper limit value of the ultra-low load range. In this way, as the load increases, the difference between the normal calculation opening and the opening for ultra-low load is reduced so that the opening for ultra-low load approaches the normal calculation opening. As a result, when entering the low load range from the ultra-low load range, the opening degree of the hot gas bypass valve is set to an excessively larger opening degree than the normal calculation opening degree, and the inlet vane opening degree becomes excessive. Can be prevented. Preferably, when connecting from the ultra-low load range to the low load range, the difference between the normal calculation opening and the ultra-low load opening is set to be zero.

  Furthermore, according to the heat source apparatus of the present invention, the opening degree for ultra-low load is calculated by multiplying the normal calculation opening degree by a correction coefficient.

By multiplying the normal calculation opening by the correction coefficient, an ultra-low load opening can be obtained by simple calculation.
Further, by changing the correction coefficient in accordance with the load, it is possible to bring the ultra-low load opening closer to the normal calculation opening as it goes from the lower limit value to the upper limit value of the ultra-low load range. For example, if the correction coefficient at the lower limit value of the ultra-low load range is set to 1.5, the correction coefficient at the upper limit value is set to 1.0, and the correction coefficient between the lower limit value and the upper limit value is prorated according to the load. good.

Furthermore, according to the heat source apparatus of the present invention, the load limit value of the low load mode and a load upper limit value of the ultra-low-load mode are the same, by the control unit, a load to be output to the front Kigaibu load Switching between the low load mode and the ultra-low load mode according to is continuously connected.

By continuously connecting the low load mode and the ultra low load mode, the operation of the heat source device can be continuously continued even when the load increases from the ultra low load. For example, a load of 0% to 10% is set to an ultra-low load mode, a load of 10% to 20% is set to a low load mode, and a load of 20% or more is set to a normal operation mode. The heat source machine can be operated.
In particular, as in the above-described invention, if the difference between the normal calculation opening and the opening for ultra-low load becomes smaller from the lower limit value to the upper limit value of the ultra-low load range, The low load mode can be smoothly connected.

  Furthermore, according to the heat source apparatus of the present invention, the compressor includes an impeller case that houses an impeller that compresses the refrigerant, and a motor that is connected to the impeller case and houses a motor that rotates the impeller. A refrigerant introduction pipe for introducing a refrigerant from the condenser and a refrigerant outflow pipe for allowing the refrigerant to flow out to the evaporator, and each device in the motor case includes: Flow rate limiting means for limiting the flow rate of the refrigerant that is cooled by the refrigerant flowing through the refrigerant introduction pipe, the motor case, and the refrigerant outflow pipe and flows out of the refrigerant outflow pipe in the low load mode and / or the ultra low load mode. Is provided.

In the low load mode and / or in the ultra low load mode, the pressure of the condenser tends to be low, and the pressure in the motor case is low. On the other hand, the main system refrigerant passing through the impeller is compressed by the impeller and thus has a certain level of pressure. The impeller case and the motor case are connected and provided with a seal. However, because the refrigerant slightly flows between the cases according to the pressure gradient before and after the seal, the pressure balance between the refrigerant cooling line passing through the refrigerant introduction pipe, the motor case and the refrigerant outflow pipe and the main system flowing through the impeller is If the design condition is not satisfied, the pressure in the motor case becomes lower than the pressure in the impeller case, and the lubricating oil in the impeller case may flow out to the motor case side.
On the other hand, in the present invention, by restricting the flow rate of the refrigerant flowing out from the refrigerant outflow pipe, the lubricating oil flows out from the impeller case side to the motor case by keeping the pressure in the motor case at a predetermined value or more. The possibility disappears.

  Moreover, the heat source system of the present invention includes at least one heat source device described in any of the above.

  By providing at least one heat source device of the present invention, standby operation can be performed by operating this heat source device in the ultra-low load mode, and a sudden load request can be dealt with immediately.

In addition, the control method of the heat source apparatus of the present invention includes a compressor that compresses the refrigerant, an inlet vane that adjusts the suction gas refrigerant flow rate of the compressor, and a condenser that condenses the refrigerant gas compressed by the compressor. An expansion valve that expands the refrigerant condensed by the condenser; an evaporator that evaporates the refrigerant expanded by the expansion valve; and a cold water pipe that supplies cold water heat-exchanged by the evaporator to an external load And a hot gas bypass pipe provided between the refrigerant discharge side and the refrigerant suction side of the compressor, bypassing the condenser and the evaporator, and provided with a hot gas bypass valve, and supplied to the external load And a control unit that controls the inlet vane so that the temperature of the chilled water to be set becomes a set temperature, and the control unit determines the rotation speed of the compressor, the refrigerating capacity, the refrigerant condensing pressure, the refrigerant evaporating pressure, etc. A method of controlling a heat source apparatus for calculating an opening degree of the hot gas bypass valve in each opening of the inlet guide vanes as a normal operation opening based on the characteristics of the resulting compressor, the control unit, the hot gas bypass valve a normal operation mode for controlling the inlet guide vanes without opening the front Kigaibu when the load being outputted to the load becomes lower predetermined low load range than the normal operation mode, the opening of the hot gas bypass valve It controls the degree, low load mode and the even lower super low load range than the low load range load output to the external load hot gas controlled by repeating the stopping and starting of the heat source equipment continue to operate while controlling the opening degree of the bypass valve, and a super-low-load mode for stopping the heat source apparatus when a lower limit of the ultra low load range, contact the ultra low load mode That opening of the hot gas bypass valve is characterized by being ultra-low load opening is the larger opening than the normal operational opening.

When the load required by the external load on the heat source device decreases and becomes, for example, in the range of 20% to 10% (low load range), the control unit temporarily stops and temporarily starts the compressor. Repeat the operation and control to achieve the set cold water outlet temperature. In this way, a low load mode that repeats stop and start of the compressor when the load is low is provided to cope with the low load.
In addition, even if the load required by the external load on the heat source unit is lower than the low load range and is, for example, 10% to 0% (ultra low load range), the operation of the heat source unit is continued, An ultra-low load mode is provided in which the heat source unit is stopped when the cold water inlet temperature or the cold water outlet temperature reaches the minimum temperature during the ultra-low load. In this ultra-low load mode, the compressor is not stopped even when the load falls below the low load range, and the heat source machine is stopped only when the cold water inlet temperature or the cold water outlet temperature reaches the lower limit of the lowest temperature at the ultra low load. Let That is, the mode in which the heat source machine is difficult to stop and can be continuously operated even when the load is low is achieved.

On the other hand, the hot gas bypass pipe is provided between the refrigerant discharge side and the refrigerant suction side of the compressor, and causes a part of the refrigerant discharged from the compressor to flow to bypass the condenser and the evaporator. Since the refrigerant flowing through the hot gas bypass pipe does not perform refrigeration work (becomes a circulation loss), load control of the heat source unit is performed by controlling the flow rate through the hot gas bypass pipe with the hot gas bypass valve. The opening of the hot gas bypass valve is calculated by calculating the required values according to the physical properties of the refrigerant from the condensing pressure, evaporating pressure, compressor speed, and refrigeration capacity (obtained from the chilled water inlet / outlet temperature and chilled water flow rate). Compared with (internal data), it is calculated as the minimum opening (normal calculation opening) of the required hot gas bypass valve. Since the characteristics of the compressor differ depending on the opening degree of the inlet vane, the normal calculation opening degree is determined for each opening degree of the inlet vane.
In the present invention, the opening of the hot gas bypass valve in the ultra-low load mode is set to an opening larger than the normal calculation opening (opening for ultra-low load). It will flow to the bypass pipe. Thereby, since a circulation loss becomes large, control is performed so that the opening degree of the inlet vane is greatly opened in order to obtain a necessary refrigeration output. Therefore, it is possible to maintain the appropriate control range of the inlet vane even in the ultra-low load mode, where the load is lower than in the low-load mode and it is difficult to continue operation. Can do.

  Note that the low load mode and the ultra low load mode may be selected alternatively, and as described later, the low load mode and the ultra low load mode are continuously selected according to the load change. You may make it connect to.

Further, the method of operating the heat source system of the present invention is a load, a said heat source system operation method of supplying cold water to the external load, in a state in which the no load on the external load occurs, which is expected to occur In order to respond to the above, standby operation is enabled in the ultra-low load mode.

  Since it was decided to cope with the load generated by the turbo chiller in standby operation, the time can be significantly reduced compared to the case of starting the stopped turbo chiller, and the load can be handled immediately. Can start. In addition, since the standby operation is performed in the ultra-low load mode, the power consumption can be reduced as much as possible.

According to the present invention, the following operational effects can be obtained.
The operation of the heat source unit is continued even if the load required by the external load on the heat source unit is lower than the low load range, and the chilled water inlet temperature or chilled water outlet temperature is the minimum temperature at the very low load. Since the ultra-low load mode for stopping the heat source machine in the case of becoming a load is provided, it is possible to enable continuous operation in which the heat source machine is difficult to stop even if the load becomes low. In addition, even in the adjustment operation when the heat source equipment is introduced in winter, it is not necessary to separately install a boiler or the like to give a cooling load larger than the load that stops in the low load mode, and the low load in winter Adjusting operation becomes possible with.

  In addition, since the opening of the hot gas bypass valve in the ultra-low load mode is set to an opening larger than the normal calculation opening (opening for ultra-low load), the operation is continued at a lower load than in the low-load mode. Even in an ultra-low load mode, which is difficult to achieve, an appropriate control range of the inlet vane can be maintained.

  In addition, since the refrigerant flow rate flowing out from the refrigerant outflow pipe connected to the motor case is limited in the low load mode and / or the ultra-low load mode, the pressure in the motor case is maintained at a predetermined value or more. The lubricant oil can be prevented from flowing out from the impeller case to the evaporator via the motor case.

  Further, since the load generated by the turbo chiller in the standby operation is handled, the load handling can be started immediately. In addition, since the standby operation is performed in the ultra-low load mode, the power consumption can be reduced as much as possible.

Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic configuration of a turbo refrigerator (heat source machine) 1 of the present invention.
As shown in FIG. 1, the turbo refrigerator 1 is condensed by a turbo compressor 3 that compresses a refrigerant, a condenser 5 that condenses the refrigerant compressed by the compressor 3, and the condenser 5. An expansion valve 7 for expanding the liquid refrigerant, and an evaporator 9 for evaporating the refrigerant expanded by the expansion valve 7.

The compressor 3 is a turbo centrifugal compressor provided with a centrifugal impeller, and is rotationally driven by an electric motor. The rotation speed of the electric motor is variable by inverter control.
An inlet vane 12 for adjusting the flow rate of the suction refrigerant is provided at the refrigerant suction port of the compressor 3. The opening degree of the inlet vane 12 is controlled by the control unit of the turbo refrigerator 1.

  The condenser 5 is a shell-and-tube heat exchanger. The condenser 5 is connected to a cooling water return pipe 5a and a cooling water forward pipe 5b. The cooling water flowing into the condenser 5 from the cooling water return pipe 5a exchanges heat with the refrigerant in the shell, and removes the heat of condensation from the refrigerant. The cooling water pipes 5a and 5b are connected to a cooling tower (not shown) installed outside.

The expansion valve 7 is provided between the condenser 5 and the evaporator 9, and is enthalpy-expanded by squeezing the liquid refrigerant supplied from the condenser 5.
The opening degree of the expansion valve 7 is controlled by the control unit of the turbo refrigerator 1.

  The evaporator 9 is a shell-and-tube heat exchanger. The evaporator 9 is connected to a cold water return pipe 34 and a cold water forward pipe 35. The cold water that has flowed into the evaporator 9 from the cooling water return pipe 34 and the refrigerant in the shell exchange heat, and the refrigerant takes the heat of evaporation from the cold water to cool the cold water. The cooled cold water is sent to an external load (not shown) through the cold water outgoing pipe 35 and supplies cold heat to the external load.

  A plurality of chilled water inlet temperature sensors 40 for measuring the chilled water inlet temperature TE0 immediately before the evaporator 9 inflow are provided on the downstream side of the chilled water return pipe 34, and the chilled water outlet temperature TE immediately after the evaporator 9 is discharged on the upstream side of the chilled water outgoing pipe 35. A plurality of cold water outlet temperature sensors 42 for measuring 'are provided respectively. As the temperature sensor, it is preferable to use a JIS A class resistance temperature detector. Generally, the cold water inlet temperature TE0 is set to 12 ° C., and the cold water outlet temperature TE ′ is set to 7 ° C.

  A hot gas bypass pipe 45 is provided between the discharge side of the compressor 3 and the suction side of the compressor 3. The hot gas bypass pipe 45 is provided with a hot gas bypass valve 45a for adjusting the refrigerant flow rate. The high-temperature and high-pressure discharged refrigerant whose flow rate is adjusted by the hot gas bypass valve 45a bypasses the condenser 5 and the evaporator 9, and is led to the suction side of the compressor 3. The opening degree of the hot gas bypass valve 45 a is adjusted by the control unit of the turbo chiller 1.

Next, the operation of the turbo refrigerator 1 having the above configuration will be described.
The compressor 3 is driven by an electric motor and rotated at a predetermined frequency. The opening degree of the inlet vane 12 is adjusted by the control unit so as to achieve a set temperature (for example, a cold water outlet temperature of 7 ° C.).
Further, a part of the high-temperature and high-pressure gas refrigerant discharged from the compressor 3 passes through the hot gas bypass pipe 45, and the refrigerant flow rate is adjusted by the hot gas bypass valve 45 a, and then is guided to the compressor 3. It has become.

The low-pressure gas refrigerant sucked from the evaporator 9 is compressed by the compressor 3 and becomes a high-pressure gas refrigerant. The high-pressure gas refrigerant discharged from the compressor 3 is guided to the condenser 5.
In the condenser 5, the high-pressure gas refrigerant is cooled to approximately the same pressure by the cooling water introduced from the cooling tower via the cooling water pipes 5 a and 5 b to become a high-pressure liquid refrigerant. The high-pressure liquid refrigerant is guided to the expansion valve 7, and is expanded enthalpy by the expansion valve 7. The refrigerant thus expanded evaporates in the evaporator 9 and takes heat from the cold water flowing in the heat transfer tube 37. Thus, the cold water flowing in at 12 ° C. from the cold water return pipe 34 is cooled to 7 ° C. and returned to the external load side via the cold water forward pipe 35. At this time, the cold water outlet temperature and the cold water inlet temperature are measured by the temperature sensors 40 and 42, respectively.
The low-pressure gas refrigerant evaporated in the evaporator 9 is guided to the compressor 3 and compressed again.

The opening degree of the inlet vane 12 is controlled by the control unit such that the cold water outlet temperature becomes the set temperature.
As the opening degree of the hot gas bypass valve 45a, a necessary minimum opening degree (normal calculation opening degree) is calculated based on the current characteristics of the compressor 3. The characteristics of the compressor 3 are stored as internal data of the control unit, and are obtained in advance with parameters such as condensing pressure, evaporating pressure, compressor rotation speed, and refrigerating capacity according to the physical properties of the refrigerant. The refrigeration capacity is obtained from the cold water inlet / outlet temperature and the cold water flow rate. Since the characteristics of the compressor 3 differ depending on the opening degree of the inlet vane 12, the normal calculation opening degree is determined for each opening degree of the inlet vane 12.

Next, an operation method of the turbo chiller 1 at a low load such as in winter will be described.
The turbo refrigerator 1 has a low load mode and an ultra-low load mode.
In the low load mode, when the load output to the external load falls within a predetermined low load range, the turbo chiller is repeatedly controlled to stop and start. Specifically, it is performed in a low load range of 10 to 20% of the rated load.
In the ultra-low load mode, the operation is continued even if the load output to the external load is in the ultra-low load range lower than the low load range, and the turbo chiller is stopped when it reaches the lower limit of the ultra-low load range. To do. Specifically, this is a mode in which the cold water inlet temperature can be continuously operated up to the lowest temperature at the time of ultra-low load (the lower limit value of the ultra-low load range).

  The control unit of the centrifugal chiller 1 is provided with a physical switch that switches between a low load mode and an ultra-low load mode. This switch is switched by an operator. By setting this switch, the ultra-low load mode is selected when it is not desired to stop even at a low load, and the low load mode is selected when it is desired to stop at a low load. In addition, when the standby operation is performed, the super low load mode is selected. In addition, it may replace with a physical switch and it is good also as switching by the remote operation by the signal from the central control room which controls the system containing the turbo refrigerator 1 integrated.

FIG. 2 shows a flowchart showing an operation method of the turbo chiller 1 in which continuous operation between the ultra-low load mode and the low load mode is possible.
When the turbo chiller 1 is started, first, in step S0, it is determined whether the load during the standard operation is 10% or more. This determination is made by the control unit of the turbo chiller 1 after obtaining information from the external load.

When the load during the standard operation is 10% or more, the process proceeds to step S10 and the operation with the normal low load, that is, the low load mode is started.
In step S11, it is determined whether or not a predetermined activation interlock is met. If it corresponds to the activation winter lock, the alarm is stopped (S12).
When it does not correspond to the start interlock, a predetermined start sequence is performed (S13), the motor is started (S14), and normal operation is performed (S14).
During normal operation, it is determined in step S16 whether the cold water inlet temperature is lower than the light load temperature. As this light load temperature, a cold water inlet temperature corresponding to a low load range is selected, and for example, a cold water inlet temperature corresponding to a load of 10% is selected.
If it is determined in step S16 that the cold water inlet temperature is lower than the light load temperature, the light load is stopped and the compressor 3 is stopped (S17). Thereafter, when the cold water inlet temperature becomes equal to or higher than the return temperature, the process returns to step S11 and the compressor 3 is restarted.
Thus, in the low load mode, the operation at a low load is performed by repeatedly stopping and starting.

On the other hand, if the load during the standard operation is less than 10% in step S0, the process proceeds to step S20 and the operation with the ultra-low load mode is started.
In step S21, it is determined whether or not a predetermined activation interlock is met. In the ultra-low load mode, unlike the low load mode, an item of a cooling water temperature of 25 ° C. or more is included as a start interlock. This is because when the cooling water temperature is 25 ° C. or higher, it is considered that a load of a certain level or more is required for the turbo refrigerator 1. In such a case, the ultra-low load mode is not performed. . In addition, 25 degreeC which is a threshold value of cooling water temperature may use another temperature, and can change it arbitrarily.
If it corresponds to the start interlock, the alarm is stopped (S22). When it does not correspond to the start interlock, a predetermined start sequence is performed (S23), the motor is started (S24), and normal operation is performed (S24).
During normal operation, it is determined in step S26 whether the cold water inlet temperature or the cold water outlet temperature is lower than the stop temperature. As this stop temperature, a temperature higher than the minimum reference temperature allowed for the heat source system in which the heat source apparatus is introduced is selected.
If it is determined in step S26 that the cold water inlet temperature or the cold water outlet temperature is lower than the light load temperature, the light load is stopped and the compressor 3 is stopped (S27). Thereafter, when the cold water inlet temperature becomes equal to or higher than the return temperature, the process returns to step S21, and the compressor 3 is restarted.
Thus, in the ultra-low load mode, the turbo chiller is continuously operated up to the stop temperature corresponding to the lower limit value of the ultra-low load range.

  The low load mode and the ultra-low load mode described above can shift to each other. For example, when the load of the turbo chiller 1 activated in the ultra-low load mode for performing the standby operation increases and the load exceeds 10%, the mode is shifted to the low load mode. This transition may be performed automatically by the control unit or may be performed by an operator. Of course, when the load of the turbo chiller 1 started in the low load mode decreases, it is possible to shift to the super low load mode.

[Hot gas bypass valve control at low load]
FIG. 3 shows a control method for the hot gas bypass valve. In the figure, the horizontal axis indicates the load of the turbo refrigerator 1. A load of less than 10% is defined as a very low load range, and a load of 10% or more and less than 20% is defined as a low load range.
As shown in the figure, the inlet vane opening decreases as the load decreases below 20%. Along with this, the opening degree of the hot gas bypass valve (HGBP valve) is controlled to gradually increase from around 20%. The opening degree of the hot gas bypass valve in this region is the normal calculation opening degree described above.

  When the load falls below 10% and enters the ultra-low load range, the hot gas bypass valve opening is set to an ultra-low load opening that is larger than the normal calculation opening. As shown in the figure, the opening for ultra-low load is performed by setting a correction coefficient that multiplies the normal calculation opening. That is, the correction coefficient is set to 1.0 in the low load range, and is set to gradually increase as the load decreases from 10% to 0% in the ultra-low load range, and to 1.5 at the load of 0%. . In other words, as the load increases from about 1%, the opening for ultra-low load is set to approach the normal calculation opening.

  The opening degree of the hot gas bypass valve in the ultra-low load range is preferably set so that the inlet vane opening does not exceed 40%. However, in the transient state, the inlet vane opening may exceed 40% and exceed 80%, which is the threshold value. In order to reduce the air volume corresponding to the difference of 40% to 80% of the inlet vane opening, It is preferable to provide a counter control for reducing the opening degree of the hot gas bypass valve so as to obtain a hot gas bypass amount corresponding to this difference. The opening correction time by the hot gas bypass valve is a time obtained by adding the operation time from the inlet vane opening of 80% to 40% to the valve operation amount arrival time. After the opening correction time has elapsed, the hot gas bypass valve opening is returned to the opening before the counter control. Note that the holding time may be used as a variable for adjusting the opening correction time.

In this way, in the ultra-low load range, the hot gas bypass valve opening is larger than the normal calculation opening, so that a larger flow rate flows in the hot gas bypass pipe 45 than in the low load region. Thereby, since a circulation loss becomes large, control is performed so that the opening degree of the inlet vane 12 is greatly opened in order to obtain a necessary refrigeration output. Therefore, the appropriate control range of the inlet vane 12 can be maintained even in the ultra-low load mode where the load is lower than in the low-load mode and it is difficult to continue operation.
Also, as the load increases from the lower limit value to the upper limit value of the ultra-low load range, that is, the difference between the normal calculation opening and the ultra-low load opening is reduced, and the normal calculation is performed from the ultra-low load opening. I approached the opening. As a result, when entering the low load range from the ultra-low load range, the opening degree of the hot gas bypass valve 45a is set to an opening degree that is excessively larger than the normal calculation opening degree, and the inlet vane opening degree becomes excessive. Can be prevented.

[Compressor refrigerant cooling system]
FIG. 4 shows a system for cooling the refrigerant of the compressor 3.
The compressor 3 includes an impeller case 3a that stores an impeller that compresses the refrigerant, and a motor case 3b that stores a motor that is connected to the impeller case 3a and rotates the impeller.
The motor case 3b is connected to a refrigerant introduction pipe 13 that guides the refrigerant from the condenser and a refrigerant outflow pipe 15 that causes the refrigerant to flow out to the evaporator.
Each device such as a motor in the motor case 3 b is cooled by the refrigerant flowing through the refrigerant introduction pipe 13, the motor case 3 b, and the refrigerant outflow pipe 15.
The refrigerant outflow pipe 15 is provided with a flow rate adjusting valve (flow rate limiting means) 17. The flow rate adjusting valve 17 can adjust the opening degree in a range of 100% to 50% without being completely closed. The flow rate adjusting valve 17 is controlled by the control unit so that the opening degree is reduced when the pressure in the motor case 3b is reduced.

The refrigerant cooling system of the compressor 3 having the above configuration operates as follows.
In normal operation, since the differential pressure between the condensation pressure and the evaporation pressure is sufficiently secured, the operation is performed with the flow rate adjustment valve 17 fully opened. Thereby, each apparatus in the motor case 3b is cooled by the liquid refrigerant guided from the condenser.
On the other hand, in the low load mode and the ultra low load mode, since the operation is performed when the outside air temperature is low as in winter, the pressure of the condenser tends to be low, and the pressure in the motor case 3b is low. On the other hand, the main system refrigerant passing through the impeller is compressed by the impeller and thus has a certain level of pressure. The impeller case 3a and the motor case 3b are connected and provided with a seal. However, since the refrigerant slightly flows between the cases according to the pressure gradient before and after the seal, the refrigerant cooling line passing through the refrigerant introduction pipe 13, the motor case 3b and the refrigerant outflow pipe 15 and the main system flowing through the impeller If the pressure balance deviates from the design condition, the pressure in the motor case 3b becomes lower than the pressure in the impeller case 3a, and the lubricating oil may flow out from the impeller case 3a side to the motor case 3b. In such a case, by controlling the flow rate adjusting valve 17 in the closing direction, there is no possibility that the lubricating oil flows out from the impeller case 3a side to the motor case 3b.

  In addition, as shown in FIG. 5, it is good also as providing two refrigerant | coolant outflow piping 15a, 15b in parallel, and providing the flow regulating valve 17 in one refrigerant | coolant outflow piping 15b. In this case, the opening degree of the flow rate adjusting valve 17 is from fully open (100%) to fully closed (0%). When the pressure in the motor case 3b becomes low, the flow rate adjustment valve 17 is fully closed so that the refrigerant flows from the other refrigerant outflow pipe 15a.

[Standby operation]
In the heat source system including a plurality of turbo chillers according to this embodiment, the following operation is possible.
Such a heat source system includes a turbo chiller that supplies cold water necessary for manufacturing facilities in the factory, and an air conditioning turbo chiller that performs air conditioning in the factory.
The turbo chiller that supplies the cold water necessary for the production equipment in the factory is operated in a state where the low load mode is selected because a predetermined load is expected. On the other hand, for the air-conditioning turbo chiller, since there is no cooling load in the winter season, the ultra-low load mode is selected and a standby operation is performed. And when humidity rises temporarily like a rain, dehumidification is performed by increasing the load of the turbo refrigerator set to the standby operation.

The turbo refrigerator 1 according to the present embodiment has the following operational effects.
When the load that the external load demands on the heat source unit falls below the low load range and the turbo chiller 1 continues to operate even if it is in the ultra low load range, and the lower limit of the ultra low load range is reached Since the ultra-low load mode for stopping the turbo chiller 1 is provided, the turbo chiller can be continuously operated without stopping even when the load becomes low.

  Further, since the opening degree of the hot gas bypass valve 45a in the ultra-low load mode is set to an opening degree larger than the normal calculation opening degree, it is an ultra-low load mode in which the load is lower and the operation is difficult to continue than in the low load mode. However, the appropriate control range of the inlet vane 12 can be maintained, and the continuous operation of the heat source machine at an ultra-low load can be ensured.

  In addition, since the dehumidification is performed by the turbo chiller set in the standby operation, the time can be significantly reduced as compared with the case of starting the stopped turbo chiller, and the dehumidification can be started immediately. it can. In addition, since the standby operation is performed in the ultra-low load mode, the power consumption can be reduced as much as possible.

  In the present embodiment, the configuration in which the low load mode and the ultra-low load mode can be continuously switched has been described. However, the low-load mode and the ultra-low-load mode may be operated as separate operation modes. good. Specifically, as shown in FIG. 6, mode selection may be performed by a remote signal from the in-panel switch or the central control room (S 01), and subsequent operations between the modes may be prohibited. The operation in each mode is the same as in FIG.

Further, in the present embodiment, the turbo chiller 1 that exclusively performs the refrigeration operation has been described, but the present invention can also be applied to a heat pump turbo chiller having a heat pump operation.
Moreover, although the turbo refrigerator was demonstrated as an example as a heat source machine, the heat source machine of another type may be sufficient, for example, a screw chiller may be sufficient.

It is the schematic which showed the turbo refrigerator concerning one Embodiment of this invention. It is a flowchart which shows the operating method of the turbo refrigerator by which the continuous driving | operation between the ultra low load mode and the low load mode was enabled. It is the graph which showed the control method of a hot gas bypass valve. It is the schematic which showed the refrigerant | coolant cooling system of the compressor. It is the schematic which showed the modification of FIG. It is a flowchart which shows the operating method of the turbo refrigerator shown the modification of FIG.

Explanation of symbols

1 Turbo refrigerator (heat source machine)
3 Compressor 5 Condenser 7 Expansion valve 9 Evaporator 34 Chilled water return pipe 35 Chilled water outgoing pipe 40 Chilled water inlet temperature sensor 42 Chilled water outlet temperature sensor 45 Hot gas bypass pipe 45a Hot gas bypass valve

Claims (8)

A compressor for compressing the refrigerant;
An inlet vane for adjusting the suction refrigerant flow rate of the compressor;
A condenser for condensing the refrigerant compressed by the compressor;
An expansion valve for expanding the refrigerant condensed by the condenser;
An evaporator for evaporating the refrigerant expanded by the expansion valve;
Cold water piping for supplying cold water heat-exchanged by the evaporator to an external load;
A hot gas bypass pipe provided between a refrigerant discharge side and a refrigerant suction side of the compressor, bypassing the condenser and the evaporator, and provided with a hot gas bypass valve;
A controller that controls the inlet vane so that the temperature of the cold water supplied to the external load becomes a set temperature;
The control unit opens the hot gas bypass valve for each opening of the inlet vane based on the compressor characteristics obtained from the rotational speed of the compressor, the refrigerating capacity, the refrigerant condensing pressure, the refrigerant evaporating pressure, and the like. In the heat source machine that calculates the degree as the normal calculation opening degree,
Wherein,
A normal operation mode for controlling the inlet vane without opening the hot gas bypass valve;
When the load to be output to the front Kigaibu load becomes lower predetermined low load range than the normal operation mode, controls the opening degree of the hot gas bypass valve, repeated stop and start of the heat source equipment Low load mode to control
Even if the load output to the external load is an ultra-low load range lower than the low load range, the operation is continued while controlling the opening degree of the hot gas bypass valve, and the lower limit value of the ultra-low load range is set. And has an ultra-low load mode to stop the heat source machine when
The heat source device according to claim 1, wherein the opening degree of the hot gas bypass valve in the ultra-low load mode is an opening degree for ultra-low load that is larger than the normal calculation opening degree. The difference between said normal operation opening the ultra-low load opening, close the smaller to the ultra-low load opening as the go upper limit value from the lower limit value of the ultra-low load range to the normal operation opening The heat source machine according to claim 1.   The heat source apparatus according to claim 1 or 2, wherein the opening degree for ultra-low load is calculated by multiplying the normal calculation opening degree by a correction coefficient. The load lower limit value of the low load mode and the load upper limit value of the ultra-low load mode match,
By the control unit, claim 1, characterized in that the corresponding to the load output Previous Kigaibu load the low load mode is switched to the ultra-low-load mode is continuously connected 3 The heat source machine described in 1. The compressor includes an impeller case that houses an impeller that compresses refrigerant, and a motor case that houses a motor that is connected to the impeller case and rotates the impeller.
The motor case is connected to a refrigerant introduction pipe for introducing a refrigerant from the condenser and a refrigerant outflow pipe for allowing the refrigerant to flow out to the evaporator.
Each device in the motor case is cooled by the refrigerant flowing through the refrigerant introduction pipe, the motor case and the refrigerant outflow pipe,
The low load mode and / or the ultra-low-load mode, according to any of claims 1 to 4, characterized in that the flow limiting means for limiting the flow rate of the refrigerant flowing out of the refrigerant outlet pipe is provided Heat source machine. A heat source system comprising at least one heat source device according to any one of claims 1 to 5 . A compressor for compressing the refrigerant;
An inlet vane for adjusting the suction refrigerant flow rate of the compressor;
A condenser for condensing the refrigerant compressed by the compressor;
An expansion valve for expanding the refrigerant condensed by the condenser;
An evaporator for evaporating the refrigerant expanded by the expansion valve;
Cold water piping for supplying cold water heat-exchanged by the evaporator to an external load;
A hot gas bypass pipe provided between a refrigerant discharge side and a refrigerant suction side of the compressor, bypassing the condenser and the evaporator, and provided with a hot gas bypass valve;
A controller that controls the inlet vane so that the temperature of the cold water supplied to the external load becomes a set temperature;
The control unit opens the hot gas bypass valve for each opening of the inlet vane based on the compressor characteristics obtained from the rotational speed of the compressor, the refrigerating capacity, the refrigerant condensing pressure, the refrigerant evaporating pressure, and the like. In the control method of the heat source machine that calculates the degree as the normal calculation opening degree,
Wherein,
A normal operation mode for controlling the inlet vane without opening the hot gas bypass valve;
When the load to be output to the front Kigaibu load becomes lower predetermined low load range than the normal operation mode, controls the opening degree of the hot gas bypass valve, repeated stop and start of the heat source equipment Low load mode to control
Even if the load output to the external load is an ultra-low load range lower than the low load range, the operation is continued while controlling the opening degree of the hot gas bypass valve, and the lower limit value of the ultra-low load range is set. And has an ultra-low load mode to stop the heat source machine when
The method of controlling a heat source machine, wherein the opening degree of the hot gas bypass valve in the ultra-low load mode is an opening degree for ultra-low load that is larger than the normal calculation opening degree. The operation method of the heat source system according to claim 6 , wherein cold water is supplied to an external load .
Wherein in a state in which the load on the external load has not occurred, the heat source system operating method, wherein a standby operation to accommodate loads occur is expected and is capable in the ultra-low-load mode.

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