JPH0456225B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Classification, Field> The disclosed technology belongs to the field of technology for controlling the refrigerant circulation capacity of the refrigeration cycle of an air conditioning centrifugal refrigerator.

<Explanation of the gist> Accordingly, the invention of this application supplies the evaporated refrigerant gas from the evaporator to the compressor to compress it to high temperature and high pressure, and then condenses and liquefies the high temperature and high pressure refrigerant with cooling water in the condenser, and evaporates it again. The above condensation suppresses surging of the suction vane of the compressor of a turbo chiller that performs a refrigeration cycle in which the heat of vaporization is taken from the cold water returned to the container, vaporized and recycled to the compressor, and the cold water is cooled and used. This invention relates to a method for controlling the capacity of a circulating refrigerant in which the operation of the suction vane is automatically controlled according to the temperature at the inlet of the cooling water of the refrigerant, and a device directly used in the control method. The inlet temperature of the cooling fluid such as the cooling water of the condenser is actually measured with a thermistor, etc., and inputted to the temperature control device to control the actuator of the suction vane to ensure surging suppression and set its lower operating limit to the actual deviation. This invention relates to a method for controlling the capacity of a centrifugal chiller, which changes the capacity according to the change in capacity so as to be able to operate at the minimum capacity corresponding to the actual load, and a device directly used therefor.

<Prior Art> As is well known, there are absorption type and turbo type air conditioning systems, and the latter is widely used because of its high operational efficiency and ease of management.

In the conventional turbo refrigeration system, the refrigerant gas generated in the evaporator is compressed to high temperature and high pressure by the compressor, sent to the next stage condenser, condensed with cooling water, liquefied, and returned to the evaporator. However, since surging of the refrigerant circulating in the refrigeration cycle disturbs smooth air conditioning operation, the refrigeration cycle is designed to limit the operating range of the suction vanes of the compressor.

Additionally, in order to determine the amount of condensed liquefied refrigerant in the circulating refrigerant in the condenser in order to meet the general standards for air conditioning usage, the temperature at the cooling water inlet of the condenser is determined as the specification temperature. The generation of surging is controlled by temperature, and the operation of the suction vane is controlled to be limited.

As a result, the operating characteristics of the suction vanes are uniquely determined by the specified temperature of the cooling water inlet of the condenser.

A related example of this type is JP-A-57-115656.

<Problems with the Prior Art> Therefore, in a conventional turbo refrigeration system in which a specified temperature is set, the lower limit of the capacity control of the circulating refrigerant during operation is constrained by the specified temperature. For example, there was a drawback in that there was no operational flexibility because the temperature was achieved only at the specified temperature, and the specified temperature itself was not suitable for all seasons.

Furthermore, under conditions where the cooling water inlet temperature is lower than the specified temperature, surging does not occur because the operation of the suction vane is limited to the specified temperature as described above. Another drawback was that it was not possible to control the capacity up to its limit.

Furthermore, since the capacity can be controlled only for the set specification temperature, the suction vane drive actuator starts and stops frequently, which means that maintenance and inspections are required frequently, and as long as this is the case, the life of the device cannot be extended sufficiently. There were some defects, and the disadvantage was that maintenance costs were high.

<Objective of the Invention> The object of the invention of this application is to solve the problem of capacity control by the suction vane in the refrigeration cycle of the turbo refrigeration system based on the above-mentioned prior art, and to solve the problem by restricting the cooling water inlet temperature to the specified temperature. It is possible to control the capacity according to the actual load, avoid overcooling of the fluid to be cooled, save energy, avoid frequent starts and stops, extend the life of the equipment, and enable smooth operation with minimum capacity. In this way, it is an object of the present invention to provide an excellent method for controlling the capacity of a centrifugal chiller, which is beneficial to the field of air conditioning application in various industries, and a device directly used therefor.

<Structure of the Invention> In order to solve the above-mentioned problems, the invention of this application, which is based on the above-mentioned claims in accordance with the above-mentioned object, operates a centrifugal refrigerator to transfer evaporated refrigerant gas from an evaporator to a compressor. The suction vane rotates the refrigerant, changes the compression state, brings it to a high temperature and high pressure state, and sends it under pressure to a condenser, where it is cooled by a cooling fluid to become a condensed liquefied refrigerant, which is circulated and fed to the evaporator to cool the fluid. The heat of vaporization is removed from the fluid and the fluid is evaporated and gasified again to follow the refrigeration cycle, and the fluid to be cooled is cooled and used for air conditioning. The inlet temperature of the cooling fluid is detected by the sensor and input to the temperature adjustment device, and the temperature adjustment device calculates the detected cooling water inlet temperature and the corresponding preset and memorized suction vane operation opening. to change the lower operating limit of the suction vane, output a control signal when the surging limit is reached, operate the drive actuator, avoid overcooling of the cooled fluid at the minimum output, and perform turbo refrigeration with the optimum operation for the actual load. This is a technical measure that allows the machine to operate.

<Embodiment - Configuration> Next, one embodiment of the invention of this application will be described below with reference to the drawings.

The embodiment shown in FIG. 1 is a centrifugal refrigerator 1, in which an evaporator 2, a compressor 3, and a condenser 4 are connected in series via refrigerant circulation passages 5, 5, 5, and the evaporator 2 is the one to be cooled. A water pipe line 6 is connected to the condenser 4, and a cooling water line 7 is interposed in the condenser 4. A drive motor 8 is connected to the compressor 3, and a suction side connected to an actuator 9 is connected to the compressor 3. Vanes 10 are provided, and their structure is substantially mechanically similar to that of conventional centrifugal chillers.

Therefore, in the invention of this application, a thermistor 12 as a temperature sensor is interposed at the cooling water inlet portion 11 of the cooling water pipe 7 of the condenser 4,
It is connected to the temperature control device 13 through a signal circuit 14 .

Although not shown, the temperature control device 13 is appropriately equipped with a microcomputer, and has a preset value that outputs an output signal only when the cooling water temperature reaches the surging limit with respect to the cooling water inlet temperature of the condenser 4 detected by the thermistor. The actuator 9 controls the control circuit 15 by comparing and calculating the actual detected cooling water inlet temperature and changing the lower limit of operation of the suction vane 10 according to changes in the cooling water temperature during operation.
I'm trying to send control signals through the .

Note that 16 is a feedback circuit from the actuator 9 to the temperature adjustment device 13.

In addition, it is known that in the turbo chiller 1, the surging limit can be approximated almost linearly if limited to a narrow range of low capacity.Therefore, in the low capacity range, the surging limit is The limit is determined by inputting the operating amount of the actuator 9 to the temperature control device 13 via the feedback circuit 16, comparing it with the cooling water inlet temperature detection signal, and operating the actuator 9 in a state where the surging limit is reached.

Note that it is not difficult for those skilled in the art to convert the temperature signal detected by the thermistor 12 into an electrical resistance signal.

The graph shown in FIG. 2 shows changes in the performance of the compressor 3 due to changes in the operation of the suction vane 10, with the horizontal axis representing the suction gas amount V of the vane 10, and the vertical axis representing the adiabatic head H. Then, the cooling water inlet temperature Tc (Tc ₁ to Tc ₅ ) of the condenser 4 is set in stages,
A correlation is shown in which the operating opening degree D (D ₀ to _{D 4} ) of the suction vane 10 is determined in stages.

This shows that the lower limit of operation of the suction vane 10 with respect to the cooling water inlet temperature is changed in accordance with the change in the inlet temperature.

<Embodiment - Effect> In the above configuration, the characteristics of the suction vane 10 of the centrifugal chiller 1 are calculated in advance by design calculations, and the microcomputer of the temperature control device 13 is programmed with the surging limit value and the vane 10 for the cooling water inlet temperature Tc. The operating lower limit value of is memorized and input.

Therefore, according to the present invention, it is not necessary to set a specific specified temperature, but it may be set within a specific range.

When the centrifugal chiller 1 is operated in this manner, the evaporated refrigerant gas from the evaporator 2 is sucked into the compressor 3 as described above, and is rotated by the suction vanes 10 to control the suction amount by the throttling effect, thereby controlling the capacity. The water is heated to high temperature and pressure, reaches the condenser 4, is cooled by cooling water, is condensed and liquefied, is then sent to the evaporator 2, absorbs the heat of vaporization from the water to be cooled, evaporates, and returns to the compressor 3. The water is sucked in and sent to the refrigeration cycle, where the heat of evaporation is removed from the water to be cooled and used for air conditioning.

During this time, as shown in FIG. 3, the thermistor 12 at the cooling water inlet 11 of the condenser 4 is constantly sensing the cooling water inlet temperature, and the detection signal is converted into an electrical resistance signal to adjust the temperature. The characteristic values corresponding to the cooling water inlet temperature of the stored vane characteristic values inputted and recalled into the device 13 are compared and calculated to determine the corresponding characteristic value, and the lower limit point of its operation is set as shown in FIG. Alternatively, the surging limit value is determined, and the feedback signal of the actual operation detection value of the actuator 9 via the feedback circuit 16 is compared with the above-mentioned inlet temperature, and the actuator operation signal is sent to the control circuit 15 in the surging limit state. The actuator 9 is controlled by the actuator 9, and the capacity is controlled according to the temperature of the cooling water, so that the actuator 9 is operated at the minimum capacity corresponding to the actual load.

<Other Examples> It goes without saying that the embodiments of the invention of this application are not limited to the above-mentioned embodiments. For example, air may be used as the cooling fluid of the condenser instead of the cooling water described above. It is also possible to use a resistance temperature sensor as appropriate for the temperature sensor, and various embodiments can be adopted.

<Effects of the Invention> According to the invention of this application, the capacity control of a centrifugal chiller is basically not limited to the specified temperature, and the operating range is significantly expanded, and the minimum Since the system can be operated with limited capacity while controlling its capacity, it not only saves energy but also enables all-season operation.

In addition, since capacity control operation is possible even at low temperatures below the specification temperature, supercooling of the cooled fluid is prevented.
It also has the effect of reducing the load on the equipment and extending its life.
It also has the advantage of not requiring frequent maintenance inspections.

In addition, since the lower limit of operation of the suction vane is lowered, the number of times the suction vane starts and stops is reduced, which has the advantage of reducing breakdowns and wear and reducing energy costs.

Therefore, the condenser inlet temperature can be easily detected by the temperature sensor, and the detection signal is controlled by the temperature control device by sending a control signal to the actuator of the suction vane, so that the condenser inlet temperature can be easily detected in accordance with the actual load. This has the effect of accurately controlling the capacity.

Furthermore, by inputting and storing the inlet temperature, surging limit value, and suction vane operating lower limit value obtained through design calculations in advance in the temperature control device, comparison calculations can be easily made and the operating lower limit value can be set. This also has the effect of allowing the actuator actuation signal to be output in the surging limit state.

[Brief explanation of the drawing]

The drawings are explanatory diagrams of one embodiment of the invention of this application, in which Fig. 1 is a mechanical diagram of a centrifugal chiller, Fig. 2 is a graph showing the performance of the compressor due to changes in suction vane operation, and Fig. 3 is It is an operation flowchart. 2...evaporator, 3...compressor, 4...condenser,
10... Suction vane, 11... Cooling fluid inlet (part), 5... Circulation system path, 9... Actuator,
15... Control circuit, 13... Temperature adjustment device, 12
...Temperature sensor, 14...Signal circuit.

Claims (1)

[Claims] 1. A circulating refrigerant in a refrigeration cycle in which refrigerant gas generated in an evaporator is compressed to high temperature and pressure by a compressor, sent to the next stage condenser, condensed with a cooling fluid, liquefied, and returned to the evaporator. In a method for controlling the capacity of a centrifugal chiller in which the amount is controlled by operating a suction vane of the compressor, the temperature of the cooling fluid inlet of the condenser is detected, and the temperature of the cooling fluid is adjusted in advance according to a change in the detected temperature. A method for controlling the capacity of a centrifugal chiller, characterized by changing a lower operating limit point of a suction vane from a surging limit of a compressor to a predetermined set point. 2. The method for controlling the capacity of a turbo chiller according to claim 1, wherein the cooling fluid of the condenser is cooling water. 3. The method for controlling the capacity of a turbo chiller according to claim 1, wherein the cooling fluid of the condenser is the atmosphere. 4. The refrigerant gas generated in the evaporator is compressed to high temperature and high pressure by a compressor, sent to the next stage condenser, condensed with cooling fluid, liquefied, and returned to the evaporator. In a capacity control device for a centrifugal chiller that operates and controls a suction vane, an actuator is connected to the suction vane of the evaporator,
A temperature control device is connected to this actuator, and a temperature sensor provided at the cooling fluid inlet of the condenser is connected to the temperature control device. A set value that outputs an output signal only when the temperature reaches the surging limit is stored and input in advance, and this value is compared and calculated with the fluid inlet temperature to change the lower limit of operation of the suction vane according to changes in the fluid inlet temperature. A capacity control device for a centrifugal chiller, characterized in that: