KR20170005103A - Turbo refrigerator, control device therefor, and control method therefor - Google Patents

Abstract

The object of the present invention is to alleviate the control delay of the expansion valve caused by the measurement delay of the thermometer. The control device 30 of the turbo refrigerator has a temperature correction section 31 for correcting the hot water inlet temperature and the hot water outlet temperature and a hot water inlet temperature correction section 31 for correcting the hot water inlet temperature and the hot water outlet temperature, And an expansion valve control section (32) for performing opening control of the expansion valve. The temperature correction section 31 includes a condensation temperature acquisition section 41 for obtaining the condensation temperature from the condensation pressure, a temperature difference calculation section 42 for calculating the temperature difference by subtracting the condensation temperature before the current condensation temperature from the present condensation temperature, A correcting section (44) for adding the temperature difference to the hot water inlet temperature and the hot water outlet temperature when the absolute value of the temperature difference is equal to or greater than the threshold value, .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a turbo refrigerator,

The present invention relates to a turbo refrigerator and its control device and a control method thereof.

Conventionally, a turbo chiller 100 as shown in Fig. 9 is known. The turbo chiller 100 is connected to the main circuit of the refrigeration cycle which sequentially connects the two-stage turbo compressor 102, the condenser 103, the economizer 104, the main expansion valve 105 and the evaporator 107 Main circuit). The gas refrigerant compressed in the turbo compressor (102) and having a high temperature and a high pressure is sent to the condenser (103). The condenser (103) is a plate type heat exchanger. The hot water circulating in the hot water circuit (111) is heat-exchanged with the gas refrigerant, thereby raising the temperature of the hot water to a predetermined temperature.

The refrigerant condensed and condensed in the condenser 103 is supplied to the economizer 104. The economizer 104 exchanges heat between the liquid refrigerant (liquefied refrigerant flowing in the main circuit) from the condenser 103 and the refrigerant decompressed by the auxiliary expansion valve 113 that is divided (shunted) from the main circuit, And is a plate type refrigerant / refrigerant heat exchanger for supercooling liquid refrigerant flowing in the main circuit by latent heat of evaporation. The economizer 104 is provided with a gas circuit for injecting the gas refrigerant vaporized by supercooling the liquid refrigerant from the intermediate inlet 102C of the two-stage turbo compressor 102 into the intermediate-pressure compressed refrigerant. The main expansion valve 105 expands the supercooled refrigerant through the economizer 104 and supplies it to the evaporator 107. The evaporator 107 is a plate type heat exchanger and evaporates the refrigerant by exchanging the refrigerant derived from the main expansion valve 105 and the heat source water circulating in the heat source circuit 115 to evaporate the heat source water .

The pressure gauges 141, 142 and 143 are connected to the suction port 102A, the discharge port 102B and the intermediate suction port 102C of the two-stage turbo compressor 2 as measuring means for measuring the temperature and pressure of the refrigerant, Thermometers 135, 136, 137 and 138 are provided at the inlet and the outlet of the hot water circuit 111 and at the inlet and the outlet of the heat source water circuit 15, respectively, At the entrance of the main expansion valve 105, a thermometer 134 is provided.

Japanese Laid-Open Patent Publication No. 2012-77971

It is known that a thermometer generally used in a turbo chiller or the like is not limited to the above-described turbo chiller 100, but has a poor response and a delay of about several minutes. This is because the temperature measuring portion can not be directly inserted into the pipe from the viewpoint of safety, ease of maintenance, or the like. For example, Fig. 10 shows a configuration example of the thermometer. 10 (a) shows an example in which a temperature-measuring resistor with a protective pipe (a thermometer made of a double structure) is inserted into a tube, Fig. 10 (b) shows an example in which the temperature is indirectly measured by welding a thermometer to the outer wall of the tube have.

And, as described above, the following problems arise due to the bad response of the thermometer.

For example, when the turbo chiller 100 shown in Fig. 9 is taken as an example, when a sudden temperature change occurs in the hot water circulating in the hot water circuit 111 (for example, when a large amount of water is added to hot water by the user, (For example, when the hot water temperature on the inlet side of the condenser 103 is suddenly decreased), it is necessary to quickly grasp this temperature change and narrow the opening degree of the main expansion valve 105 and the auxiliary expansion valve 113 have. However, since the control of the main expansion valve 105 and the auxiliary expansion valve 113 is delayed due to the measurement delay of the thermometer, the opening degree of the expansion valve becomes excessively larger than the actual temperature and the evaporator 107 and the economizer 104 The liquid refrigerant that has not yet evaporated from the evaporator 102 is sucked into the two-stage turbo compressor 102, and the two-stage turbo compressor 102 may be damaged.

An object of the present invention is to provide a turbo refrigerator which can alleviate a control delay of an expansion valve due to a measurement delay of a thermometer, a control device thereof, and a control method.

A first aspect of the present invention is a refrigerant cycle system comprising a main circuit of a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected and in which a refrigerant is circulated and a first circuit for measuring a temperature of an inlet of the refrigerant flowing into the condenser A second temperature measuring means for measuring an outlet temperature of the heat discharged from the condenser, and a pressure measuring means for measuring a condensation pressure, wherein the first temperature measuring means and the second temperature measuring means, A temperature correction means for correcting the temperature measured by the second temperature measurement means and an expansion valve control means for performing an opening control of the expansion valve by using the heat inlet temperature and the heat outlet temperature corrected by the temperature correction means, Wherein the temperature correction means comprises a condensation temperature obtaining means for obtaining a condensation temperature from the condensation pressure acquired by the pressure measurement means, A temperature difference calculating means for calculating a temperature difference by subtracting a condensation temperature a certain period before the current condensation temperature from the present condensation temperature; a judging means for judging whether the absolute value of the temperature difference is equal to or larger than a predetermined threshold value; And correction means for adding the temperature difference to each of the temperatures measured by the first temperature measurement means and the second temperature measurement means when the absolute value of the temperature difference is equal to or greater than the threshold value.

According to the control apparatus for the turbo refrigerating machine, the condensation temperature based on the condensation pressure is acquired by the condensation temperature acquisition means, and the temperature difference between the present condensation temperature and the condensation temperature before a certain period is calculated by the temperature difference calculation means. When the absolute value of the temperature difference is equal to or greater than the threshold value, it is determined by the determining means that the absolute value of the temperature difference is equal to or larger than the predetermined threshold value. The temperature difference is added to each temperature, and the temperature is corrected. As a result, the temperature change can be captured early and the measurement delay of the temperature measuring means can be relaxed. By controlling the expansion valve using the temperature after the correction by the expansion valve control means, it is possible to relax the control delay of the expansion valve caused by the measurement delay by the first temperature measurement means and the second temperature measurement means .

In the control device for the turbo refrigerator, the predetermined period may be set to a period in which the refrigerant circulates in the main circuit.

According to the control device for the turbo refrigerator, it is possible to accurately grasp the variation of the inlet temperature of the fruit.

Wherein the control device of the turbo refrigerator is provided between the condenser and the expansion valve and performs heat exchange between the liquid refrigerant flowing in the main circuit and the refrigerant which is separated from the main circuit and reduced in pressure by the auxiliary expansion valve, And a gas circuit for returning the refrigerant having undergone heat exchange with the liquid refrigerant flowing through the main circuit to the compressor in the heat exchanger, wherein the expansion valve control means The opening degree control of the sub-expansion valve may be performed by using the temperature of the heat-receiving inlet and the temperature of the heat-receiving outlet, which are corrected by the temperature correcting means.

According to the control apparatus for the turbo refrigerator, since the control of the auxiliary expansion valve is performed by using the temperature after the correction, the control delay of the auxiliary expansion valve due to the measurement delay by the first temperature measurement means and the second temperature measurement means is alleviated .

A second aspect of the present invention is a refrigerating cycle apparatus comprising a main circuit of a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected and through which a refrigerant circulates, and a heat source number A controller for controlling the inlet temperature of the evaporator and the temperature of the outlet of the evaporator, wherein the temperature of the outlet is measured by subtracting the temperature of the outlet of the evaporator from the temperature of the outlet of the evaporator, And a ratio of a value obtained by subtracting the evaporation temperature from the temperature of the heat source water inlet to a value of the evaporation temperature corrected by the evaporation temperature correction means, And an expansion valve control means for controlling the opening of the expansion valve by using an evaporation pressure obtained from the evaporation temperature, .

According to the control device for the turbo refrigerator, the ratio of the value obtained by subtracting the heat source inlet temperature from the heat source inlet temperature to the value obtained by subtracting the heat source inlet temperature from the heat source outlet temperature is corrected by the evaporation temperature correction means, The evaporation temperature corresponding to the target ratio is calculated. By reflecting the evaporation temperature calculated by the evaporation temperature correction means to the valve opening control of the expansion valve, it is possible to prevent the valve opening of the expansion valve from excessively increasing.

A third aspect of the present invention is a turbo refrigerator having the above-described control device.

A fourth aspect of the present invention is a refrigerant cycle system comprising a main circuit of a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected and through which a refrigerant is circulated, A second temperature measuring means for measuring an outlet temperature of the heat discharged from the condenser, and a pressure measuring means for measuring a condensation pressure, wherein the first temperature measuring means and the second temperature measuring means An expansion valve control step of controlling the opening degree of the expansion valve by using a temperature correction step of correcting the temperature measured by the second temperature measurement means, Wherein the temperature correction step includes a step of calculating a condensation temperature based on the condensation pressure acquired by the pressure measurement unit, A temperature difference calculating step of calculating a temperature difference by subtracting a condensation temperature a certain period before the present condensation temperature from a current condensation temperature; a judgment step of judging whether or not the absolute value of the temperature difference is equal to or larger than a predetermined threshold value; And a temperature correcting step of adding the temperature difference to each of the temperatures measured by the first temperature measuring means and the second temperature measuring means when the absolute value of the temperature difference is equal to or greater than the threshold value.

A fifth aspect of the present invention is a refrigerating cycle apparatus comprising a main circuit of a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected and through which a refrigerant circulates, and a heat source number A control method applied to a turbo refrigerator having an inlet temperature measuring means and a heat source outlet temperature measuring means for measuring an outlet temperature of the heat source water flowing out of the evaporator, And a ratio of a value obtained by subtracting the evaporation temperature from the temperature of the heat source water inlet to a value obtained by subtracting the evaporation temperature from the value of the evaporation temperature, And an expansion valve control step of controlling the opening degree of the expansion valve by using an evaporation pressure obtained from the evaporation temperature, Is a control method of the machine.

According to the present invention, the control delay of the expansion valve due to the measurement delay of the thermometer can be mitigated.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a schematic configuration of a turbo chiller according to a first embodiment of the present invention; FIG.
2 is a functional block diagram of the control apparatus according to the first embodiment of the present invention.
3 is a flowchart showing a flow of processing executed by the current flow rate calculation unit.
4 is a flowchart showing a process executed by the main expansion valve opening degree calculation section.
5 is a flowchart showing a process executed by the auxiliary expansion valve opening degree calculation section.
6 is a diagram for explaining control of the control apparatus according to the first embodiment of the present invention.
7 is a graph showing an example of the temporal transition of the heat source inlet temperature Tswi measured by the temperature sensor, the heat source outlet temperature Tswo measured by the temperature sensor, the evaporation temperature ET converted from the evaporation pressure Ps, and the compressor discharge temperature .
8 is a functional block diagram of the control apparatus according to the second embodiment of the present invention.
9 is a view showing a configuration example of a conventional turbo refrigerator.
10 is a diagram showing an example of a configuration of a thermometer.

[First Embodiment]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a turbo chiller according to a first embodiment of the present invention, its control device and a control method will be described with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing a schematic configuration of a turbo chiller according to a first embodiment of the present invention. Fig. 1, a turbo chiller 1 includes a compressor 2, a condenser 3, an economizer 4, a main expansion valve 5, and an evaporator 7, And a refrigerant main circuit (8).

The compressor 2 is a multi-stage centrifugal compressor driven by an inverter motor 6 and has an intermediate inlet 2C provided between the first vane and the second vane, in addition to the inlet 2A and the outlet 2B, Pressure gas refrigerant sucked from the suction port 2A is sequentially centrifugally compressed by the rotation of the first blades and the second blades, and the compressed high-pressure gas refrigerant is discharged from the discharge port 2B.

The high-pressure gas refrigerant discharged from the discharge port (2B) of the compressor (2) is led to the condenser (3). The condenser 3 is, for example, a plate type heat exchanger. The hot water is heated to a predetermined temperature by exchanging heat between the high-pressure gas refrigerant supplied from the compressor 2 and hot water circulating through the hot water circuit. The refrigerant condensed and condensed in the condenser 3 is supplied to the economizer 4.

The economizer 4 exchanges the liquid refrigerant flowing in the refrigerant main circuit 8 with the refrigerant which is separated from the refrigerant main circuit 8 and reduced in pressure by the auxiliary expansion valve 9 and is supplied to the latent heat of evaporation Is a plate type refrigerant / refrigerant heat exchanger for supercooling the liquid refrigerant flowing in the refrigerant main circuit (8). The economizer 4 is provided with a gas circuit 10 for injecting gas refrigerant (intermediate-pressure refrigerant) evaporated by supercooling the liquid refrigerant from the intermediate inlet 2C of the compressor 2 into the intermediate-pressure compressed refrigerant, This constitutes an economizer cycle of the intercooler type.

The refrigerant supercooled through the economizer 4 is expanded by being passed through the main expansion valve 5 and supplied to the evaporator 7. The evaporator 7 is a heat exchanger (for example, a plate type heat exchanger). The refrigerant is evaporated by exchanging the refrigerant derived from the main expansion valve 5 and the heat source water circulating through the heat source water circuit 15 , And the heat source water is cooled by the latent heat of evaporation.

The turbo chiller 1 is provided with a temperature sensor 12 for measuring the temperature of the hot water inlet Thwi which is the temperature of the hot water flowing into the condenser 3 and a temperature sensor 12 for measuring the hot water outlet temperature Thwo which is the temperature of the hot water flowing out from the condenser 3 A sensor 13 and a temperature sensor 14 provided at the refrigerant outlet side of the condenser 3 for measuring the condenser outlet temperature Tc and a temperature sensor 14 for measuring the temperature of the refrigerant in the refrigerant main circuit 8, And includes a temperature sensor 19 for measuring the inlet temperature Tecoh of the main expansion valve, a temperature sensor 16 for measuring the intermediate-pressure refrigerant temperature Tm, which is the temperature of the intermediate-pressure refrigerant flowing through the gas circuit 10, A temperature sensor 17 for measuring the temperature of the heat source inlet port Tswi which is the temperature of the heat source water flowing into the evaporator 7 and a temperature sensor 18 for measuring the temperature of the heat source outlet temperature Tswo which is the temperature of the heat source water flowing out of the evaporator 7 have. The turbo chiller 1 includes a pressure sensor 20 for measuring a condensing pressure (compressor discharge pressure) Pd, a pressure sensor 21 for measuring an intermediate-pressure refrigerant pressure Pm which is a pressure of an intermediate-pressure refrigerant flowing through the gas circuit 10, And a pressure sensor 22 for measuring the evaporation pressure (compressor suction pressure) Ps.

The measured values of the various sensors are transmitted to the control device 30 and used for control of the rotation speed of the compressor, opening control of the main expansion valve 5 and the auxiliary expansion valve 9, and the like.

The control device 30 is, for example, a computer, and includes a CPU (Central Processing Unit), a main memory such as a RAM (Random Access Memory), an auxiliary memory, a communication Device and the like.

The auxiliary storage device is a computer-readable recording medium, for example, a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, Various programs are stored in this auxiliary memory device, and the CPU realizes various processes by reading programs from the auxiliary memory device to the main memory device and executing them.

Fig. 2 is a functional block diagram of the control device 30. Fig. As shown in Fig. 2, the control device 30 includes a temperature correction section 31 and an expansion valve control section 32. As shown in Fig.

The temperature corrector 31 corrects the hot water inlet temperature Thwi and the hot water outlet temperature Thwo. That is, as described above, the measurement delay occurs in the temperature sensors 12 and 13 and the like. The temperature corrector 31 is a configuration for correcting the measurement delay by the temperature sensors 12, 13.

Specifically, the temperature control unit 31 includes a condensation temperature acquisition unit 41, a temperature difference calculation unit 42, a determination unit 43, and a correction unit 44.

The condensation temperature acquisition section (41) acquires the condensation temperature (Tc) from the condensation pressure (Pd) measured by the pressure sensor (20). Specifically, the condensation temperature acquisition section 41 has corresponding information (a function or a table) in which the condensation pressure Pd and the condensation temperature CT are uniquely associated with each other, and from this condensation pressure Pd, the condensation temperature CT .

The temperature difference computing section 42 computes a temperature difference? CT by subtracting the condensation temperature obtained before a certain period from the current condensation temperature obtained by the condensation temperature obtaining section 41. [ Here, the constant period corresponds to, for example, a period during which the refrigerant flows through the refrigerant main circuit 8, and is obtained by dividing the refrigerant charge amount [kg] by the refrigerant circulation amount [kg / min]. A period in which a predetermined margin (margin) is taken into account in this value may be a constant period.

The judging unit 43 judges whether or not the absolute value of the temperature difference [Delta] CT [Delta] CT is equal to or greater than a preset threshold value. The threshold value is, for example, a value derived from the rate of change determined by the specification of the main expansion valve 5. [ For example, when the rate of change of the main expansion valve 5 is 10 [%] / 60 [sec], the hot water inlet temperature Thwi is about 70 [deg.] C, the hot water outlet temperature Thwo is 80 [ 30 [sec], the threshold value is set by the following expression (1).

The temperature value is calculated by the following equation: Temp value = (10 [%] x 10 [占 폚] 占 30 [sec] / 60 [sec] (One)

Here,? Is a margin (margin) and may be a fixed value or a value determined according to the value in parentheses in the above-mentioned expression (1).

The correction unit 44 corrects the hot water inlet temperature Thwi and the hot water outlet temperature Thwo by adding the temperature difference? CT to the hot water inlet temperature Thwi and the hot water outlet temperature Thwo when the absolute value of the temperature difference |? CT |

The expansion valve control unit 32 calculates the expansion valve opening degree using the corrected hot water inlet temperature Thwi and the corrected hot water outlet temperature Thwo during the period in which the temperature correction is performed by the temperature correction unit 31, In the period during which the temperature correction is not performed by the correcting unit 31, the expansion valve opening degree is calculated using the hot water inlet temperature Thwi and the hot water outlet temperature Thwo measured by the temperature sensors 12 and 13. Hereinafter, the expansion valve control section 32 will be described.

The expansion valve control section 32 includes a current flow rate calculation section 51, a set flow rate calculation section 52, a main expansion valve opening degree calculation section 53 and a secondary expansion valve opening degree calculation section 54, for example. The expansion valve control is not limited to the following method, and various known control methods can be employed. In this case, when the hot water inlet temperature Thwi and the hot water outlet temperature Thwo are used as parameters, when the temperature correction is performed by the temperature corrector 31, the corrected hot water inlet temperature Thwi and hot water outlet temperature Thwi Thwo is used.

The current flow rate computation unit 51 performs the flow rate computation using the hot water inlet temperature Thwi and the hot water outlet temperature Thwo as parameters. Fig. 3 shows a flowchart of a process executed by the current flow rate calculating section 51. Fig. As shown in Fig. 3, the current flow rate calculating unit 51 calculates the current heating capacity Qcon [kW] by using the hot water inlet temperature Thwi and the hot water outlet Thwo (step SA1). Subsequently, the condenser flow rate Gcon [kg / s] is calculated using the following expression (2) (step SA2).

Gcon = Qcon / (Hd-Hc) (2)

 (2), Hd is the discharge enthalpy [kJ / kg] and Hc is the condenser outlet enthalpy [kJ / kg].

Subsequently, the current flow rate Geva of the main expansion valve 5 is calculated using the following equation (3) (step SA3).

Geva = (Gcon-Gmo-Goc) / (1 + x) (3)

Here, x = (Hc-Hecoh) / (Hecom-Hc) (4)

 In the equation (3), Gcon is the condenser flow rate [kg / s], Gmo is the motor cooling flow rate [kg / s], and Goc is the oil cooling refrigerant flow rate [kg / s]. In the equation (4), Hc is the enthalpy of the condenser outlet [kJ / kg], Hecoh is the enthalpy of enthalpy at the inlet of the main expansion valve [kJ / kg], and Hecom is the enthalpy of middle suction gas [kJ / kg].

Next, the current flow rate calculation unit 51 calculates the current flow rate Geco of the secondary expansion valve 9 using the condenser flow rate Gcon (step SA4). More specifically, calculation is performed using the following equation (5).

Geco = x Geva (5)

 In the formula (5), x is as described in the formula (4). Geva is the current flow rate Geva of the main expansion valve calculated in the above equation (3).

The current flow rate Geva of the main expansion valve and the current flow rate Geco of the auxiliary expansion valve thus calculated are output to the main expansion valve opening degree calculation section 53 and the secondary expansion valve opening degree calculation section 54. [

The set flow rate computation unit 52 computes the set flow rate Geva * of the main expansion valve 5 and the set flow rate Geco * of the auxiliary expansion valve 9. [ Here, the calculation by the set flow rate calculation unit 52 is different from the above-described calculation formula used in the current flow rate calculation unit 51 only in that the preset hot water outlet set temperature Thwo * is used instead of the hot water outlet temperature Thwo And the rest is the same. Therefore, detailed description is omitted.

The set flow rate Geva * of the main expansion valve 5 and the set flow rate Geco * of the auxiliary expansion valve 9 are outputted to the main expansion valve opening degree calculation section 53 and the secondary expansion valve opening degree calculation section 54. [

The main expansion valve opening degree calculation section 53 calculates the main expansion valve opening degree calculation section 53 based on the current flow rate Geva of the main expansion valve 5 and the present flow rate Geco of the auxiliary expansion valve 9 calculated by the current flow rate calculation section 51, The feedforward opening command is calculated by using the set flow rate Geva * of the set main expansion valve 5 and the set flow rate Geco * of the auxiliary expansion valve 9 to calculate the feedforward opening command and perform feedback control using the evaporator terminal temperature And the feedback opening command is calculated and added to all of them to generate an opening command.

4 is a flowchart showing a process executed by the main expansion valve opening degree calculation section 53. Fig.

First, in the feedforward control, the current opening degree Cveva of the main expansion valve 5 is calculated using the current flow rate Geva of the main expansion valve, the differential pressure ΔP2 (= Pd-Ps) between the condensation pressure and the evaporation pressure as parameters Step SB1). Next, the set opening degree Cveva * of the main expansion valve is calculated using the set flow rate Geva * of the main expansion valve 5 and the differential pressure? P2 as parameters (step SB2).

The opening command OP_FF in the feedforward control is calculated by calculating the current opening degree Cveva and the opening degree Cveva * of the main expansion valve 5 (step SB3).

In the feedback control, an opening command OP_FB is calculated, in which the temperature difference DELTA Tswo between the heat source outlet temperature Tswo in the evaporator 7 and the evaporation temperature ET converted from the evaporation pressure Ps coincides with the target value DELTA Tswo * (step SB4). For example, the opening command OP_FB in the feedback control is calculated by performing the PID control on the difference between the temperature difference? Tsswo and the neck mark value? Tsswo *.

In this manner, when the opening command OP_FF by the feedforward control and the opening command OP_FB by the feedback control are calculated, the final opening command OP = OP_FF + OP_FB is calculated by adding them (step SB5).

The opening degree of the main expansion valve 5 is controlled based on the opening command OP.

The auxiliary expansion valve opening degree calculation section 54 calculates the auxiliary expansion valve opening degree calculation section 54 based on the current flow rate Geva of the main expansion valve 5 and the present flow rate Geco of the auxiliary expansion valve 9 calculated by the current flow rate calculation section 51, The feedforward opening command is calculated by using the set flow rate Geva * of the set main expansion valve 5 and the set flow rate Geco * of the sub-expansion valve 9 to calculate the feedforward opening command, and using the main expansion valve inlet temperature Tecoh The feedback opening command is calculated by performing the feedback control, and all of them are added to generate the opening command OPeco of the secondary expansion valve.

5 is a flow chart showing a process executed by the auxiliary expansion valve opening degree calculation section 54. Fig.

First, in the feedforward control, the present flow rate Geco of the auxiliary expansion valve 9, the differential pressure ΔP1 (= Pd-Pm) between the condensation pressure Pd and the intermediate pressure Pm, Cveco (step SC1). Next, the set opening degree Cveco * of the auxiliary expansion valve 9 is calculated using the set flow rate Geco * of the auxiliary expansion valve 9 and the differential pressure AP1 as parameters (step SC2).

Then, the command value OPeco_FF in the feedforward control is calculated by calculating the current opening Cveco and the set opening degree Cveco * of the secondary expansion valve 9 (step SC3).

In the feedback control, the main expansion valve inlet temperature target value Tecohset (= ΔT2 + MT) is set by adding the previously set economizer outlet temperature difference ΔT2 to the sub-expansion valve inlet temperature MT (step SC4). Next, an opening command OPeco_FB for matching the current main expansion valve inlet temperature Tecoh to the main expansion valve inlet temperature target value Tecoh * is calculated (step SC5). For example, the opening command OPeco_FB in the feedback control is calculated by performing PID control on the difference between the current main expansion valve inlet temperature Tecoh and the main expansion valve inlet temperature target value Tecoh *.

In this way, the command value OPeco_FF by the feedforward control and the command value OPeco_FB by the feedback control are calculated, and the final opening command OPeco = OPeco_FF + OPeco_FB is calculated by adding these values (step SC6). The valve opening degree of the secondary expansion valve 9 is controlled based on the opening command OPeco.

Next, the operation of the control device 30 will be described with reference to Fig.

6 is a diagram for explaining control of the control device 30 according to the present embodiment.

6, before the occurrence of the change in the hot water inlet temperature Thwi at the time t1, the hot water inlet temperature Thwi shows a stable value. Therefore, the temperature difference | Th calculated by the temperature difference calculator 42 of the temperature corrector 31, ΔCT | is close to zero. Therefore, in the determining section 43, it is determined that the temperature difference | [Delta] CT | is less than the threshold value, and the temperature correction by the correcting section 44 is not performed.

On the other hand, when the hot water inlet temperature Thwi suddenly decreases at time t1, the condensation pressure Pd rapidly decreases accordingly, and the condensation temperature acquired by the condensation temperature acquisition section 41 drops. As a result, the absolute value of the temperature difference |? CT | calculated in the temperature difference computing section 42 becomes a relatively large value. As a result, the determination section 43 determines that the temperature difference [Delta] CT is equal to or greater than the threshold value, and the temperature correction by the correcting section 44 is performed. As a result, ΔCT (negative value) is added to the hot water inlet temperature Thwi measured by the temperature sensor 12 and the hot water outlet temperature Thwo measured by the temperature sensor 13, respectively, so that the hot water inlet temperature Thwi, A flow amount calculation or opening calculation using the outlet temperature Thwo is performed in the expansion valve control unit 32. [ As a result, for example, the auxiliary expansion valve 9 is controlled in such a direction as to reduce the valve opening degree (period of time t1 to t2 in Fig. 6). In the opening control of the conventional auxiliary expansion valve, since the valve opening degree is calculated using the temperature measured by the temperature sensors 12 and 13, that is, the temperature with the measurement delay, the hot water inlet temperature Thwi actually decreases The auxiliary expansion valve 9 is controlled in the opening direction, which causes the liquid suction of the compressor 2.

As described above, according to the turbo chiller, the control device and the control method thereof according to the present embodiment, the condensation temperature is acquired based on the condensation pressure, and the maximum value of the temperature difference between the present condensation temperature and the condensation temperature before the certain time | The temperature difference is corrected by adding the temperature difference? CT to the hot water inlet temperature Thwi and the hot water outlet temperature Thwi measured by the temperature sensors 12 and 13, respectively, The control delay of the expansion valve caused by the measurement delay can be relaxed. This makes it possible to avoid the liquid refrigerant suction of the compressor (2).

In the present embodiment, the excessive opening of the expansion valve is suppressed by correcting the hot water inlet temperature Thwi and the hot water outlet temperature Thwo. However, if the rate of change of the opening degree of the auxiliary expansion valve 9 is determined by the specification It is possible to avoid the suction of the liquid refrigerant in the compressor by employing a method of suppressing the refrigerant temperature to below the rated value.

[Second embodiment]

Hereinafter, a turbo chiller according to a second embodiment of the present invention, its control device and a control method will be described with reference to the drawings.

In the first embodiment described above, the hot water inlet temperature Thwi and the hot water outlet temperature Thwo are corrected. In this embodiment, however, the evaporation temperature ET in the evaporator 7, in other words, Correct the evaporation pressure Ps. As a result, the additional precision of the expansion valve control is improved.

In the first embodiment, the temperature correction is performed using the condensation temperature CT converted from the condensation pressure Pd because the influence of the change in the hot water inlet temperature Thwi appears relatively early in the condensation pressure Pd. However, with respect to the evaporator 7, when the temperature Tswi of the heat source inlet drops, it has been clarified experimentally that the influence does not appear in the evaporation pressure Ps at an early stage. 7 shows the relationship between the heat source inlet temperature Tswi measured by the temperature sensor 17, the heat source outlet temperature Tswo measured by the temperature sensor 18, the evaporation temperature ET converted from the evaporation pressure Ps, It shows an example of transition.

As shown in Fig. 7, it can be seen that the change of the evaporation temperature ET converted from the evaporation pressure Ps is slower than the change of the heat source inlet temperature Tswi and the heat source outlet temperature Tswo. Therefore, the evaporator 7 can not adopt the same method as that of the evaporator 3, such as correcting the heat source inlet temperature Tsi and the heat source outlet temperature Tswo by using the evaporation pressure Ps.

7, the difference between the heat source inlet temperature Tswi and the evaporation temperature ET (the conversion value of the evaporation pressure Ps)? Te and the difference? Ts between the heat source inlet temperature Tswi and the heat source outlet temperature Tswo It was found that the ratio K was the same. That is, it was found that the following expression holds.

K =? Te / Ts = (Tswi-ET) / (Tswi-Tswo) = constant (6)

Therefore, in the present embodiment, the value of the ratio K at the time of stabilization is set as the target ratio K *, and the evaporation temperature ET is always corrected so that the ratio K becomes the target ratio K * Tswi is reflected in the expansion valve control.

8 is a functional block diagram of the control device 35 according to the present embodiment. As shown in Fig. 8, the control device 35 further includes an evaporation temperature correcting section 33 in addition to the configuration of the control device 30 shown in Fig.

The evaporation temperature corrector 33 holds the value of the ratio K at the time of stabilization as the target ratio K *, and corrects the evaporation temperature so that the ratio K becomes the target ratio K *. That is, the evaporation temperature ET is calculated by substituting the heat source inlet temperature Tswi, the heat source outlet temperature Tswo, and the previously held target ratio K * in the following equation (7) derived from the above equation (6).

ET = Tswi- (Tswi-Tswo) K * (7)

Then, the evaporation temperature ET is converted into the evaporation pressure Ps, and the evaporation pressure Ps is used for the expansion valve control. That is, the main expansion valve opening degree calculator 53 and the auxiliary expansion valve opening degree calculator 54 calculate the main expansion valve opening degree command Sv (n) using the evaporation pressure Ps based on the evaporation temperature ET calculated by the evaporation temperature correction unit 33 OP and the auxiliary expansion valve opening command OPeco.

Here, for example, when the evaporation temperature ET is lowered due to the lowering of the heat source inlet temperature Tswi, the evaporation pressure Ps is also reduced. In the feedforward control (steps SB1 to SB3 in Fig. 4) of the opening command of the main expansion valve 5, when the evaporation pressure Ps becomes small, the main expansion valve differential pressure? P2 = Pd-Ps becomes a large value. As a result, the current flow rate Cveva and the set flow rate Ceva * of the main expansion valve become small, and the opening instruction OP_FF of the feedforward control of the main expansion valve becomes small.

In the feedback control (step SB4 in Fig. 4), an opening command OP_FB for matching the temperature difference DELTA Tswo between the heat source outlet temperature Tswo and the evaporation temperature ET in the evaporator 7 to the target value DELTA Tswo * is calculated. Here, the temperature difference DELTA Tswo can be said to be substantially constant even if the heat source inlet temperature Tswi varies (see Fig. 7), and therefore does not act in the direction in which the main expansion valve 5 is opened. From the above, it is possible to avoid the excessive opening of the main expansion valve 5 by reflecting the evaporation temperature ET by the evaporation temperature correcting section 33 to the valve opening control of the main expansion valve 5, Of the liquid refrigerant can be avoided.

Although the control devices 30 and 35 applied to the turbo chiller 1 having the configuration shown in Fig. 1 have been described in the above embodiments, the turbo chiller 1, to which the control device of the present invention is applied, 1 is not limited to the configuration shown in Fig. 1, a turbo refrigerator having no constitution relating to the economizer 4, for example, an economizer 4, an auxiliary expansion valve 9, a gas circuit 10, a temperature sensor 16 ), And the pressure sensor 21 are omitted. In this case, in the opening control of the main expansion valve 5, the above calculation may be performed with the flow rate flowing through the auxiliary expansion valve 9 being zero.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the invention.

1 turbo freezer
2 compressor
3 condenser
5-week expansion valve
7 Evaporator
8 Refrigerant main circuit
9 parts expansion valve
12 ~ 14, 16 ~ 18 Temperature sensor
20 ~ 22 Pressure sensor
30 control device
31 Temperature correction unit
32 expansion valve control section
33 Evaporation Temperature Correcting Unit
41 Condensation temperature acquisition unit
42 Temperature difference calculating section
43 judgment section
44 correction unit
51 Current Flow Calculator
52 Setting Flow Calculator
53 main expansion valve opening degree calculating section
54 part Expansion valve opening degree calculating section

Claims (7)

A condenser, an expansion valve, and an evaporator; a first temperature measuring means for measuring an inlet temperature of the heat introduced into the condenser; A second temperature measuring means for measuring an outlet temperature of the fruit to be measured, and a pressure measuring means for measuring a condensation pressure,
A temperature correction means for correcting the temperature of the inlet and outlet of the fiber, measured by the first temperature measuring means and the second temperature measuring means,
An expansion valve control means for controlling the opening of the expansion valve by using the heat input temperature and the heat outlet temperature corrected by the temperature correction means,
And,
The temperature correction means,
Condensation temperature acquisition means for acquiring a condensation temperature from the condensation pressure acquired by the pressure measurement means;
A temperature difference calculating means for calculating a temperature difference by subtracting a condensation temperature a certain period before the present condensation temperature,
Judging means for judging whether or not the absolute value of the temperature difference is equal to or larger than a predetermined threshold value;
And correcting means for adding the temperature difference to each of the temperatures measured by the first temperature measuring means and the second temperature measuring means when the absolute value of the temperature difference is equal to or greater than the threshold value,
And a controller for controlling the turbo refrigerator. The method according to claim 1,
Wherein the predetermined period is set to a period in which the refrigerant flows through the main circuit. The method according to claim 1 or 2,
The turbo-
A heat exchanger provided between the condenser and the expansion valve for exchanging heat between the liquid refrigerant flowing through the main circuit and the refrigerant decompressed by the auxiliary expansion valve and separated from the main circuit, ,
A gas circuit for returning the refrigerant that has undergone the heat exchange with the liquid refrigerant flowing through the main circuit to the compressor in the heat exchanger;
And,
Wherein the expansion valve control means controls the opening degree of the auxiliary expansion valve by using the temperature of the inlet and outlet temperatures corrected by the temperature correction means. A main circuit of a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected and in which a refrigerant is circulated, a heat source inlet temperature measuring means for measuring an inlet temperature of the heat source water flowing into the evaporator, And a heat source outlet temperature measuring means for measuring an outlet temperature of the heat source water flowing out from the heat source outlet,
A ratio of a value obtained by subtracting the evaporation temperature from the temperature of the heat source inlet port to a value obtained by subtracting the heat source inlet temperature from the temperature of the heat source water outlet port is equal to a target ratio in the stable state, and,
An expansion valve control means for controlling the opening of the expansion valve by using an evaporation pressure obtained from the evaporation temperature corrected by the evaporation temperature correction means,
And a controller for controlling the turbo refrigerator. A turbo refrigerator having the control device according to any one of claims 1 to 4. A condenser, an expansion valve, and an evaporator; a first temperature measuring means for measuring an inlet temperature of the heat introduced into the condenser; A second temperature measuring means for measuring an outlet temperature of the fruit to be measured, and a pressure measuring means for measuring a condensation pressure,
A temperature correction step of correcting the temperature measured by the first temperature measurement means and the second temperature measurement means,
An expansion valve control step for controlling the opening of the expansion valve by using the corrected inlet temperature and the outlet temperature at the temperature correction step
/ RTI >
In the temperature correction step,
A condensation temperature acquisition step of acquiring a condensation temperature from the condensation pressure acquired by the pressure measurement means;
A temperature difference calculating step of calculating a temperature difference by subtracting a condensation temperature a certain period before the current condensation temperature,
A determination step of determining whether the absolute value of the temperature difference is equal to or greater than a predetermined threshold value;
And a temperature correction step of adding the temperature difference to each of the temperatures measured by the first temperature measurement unit and the second temperature measurement unit when the absolute value of the temperature difference is equal to or greater than the threshold value
And a control device for controlling the turbo refrigerator. A main circuit of a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected and in which a refrigerant is circulated, a heat source inlet temperature measuring means for measuring an inlet temperature of the heat source water flowing into the evaporator, And a heat source outlet temperature measuring means for measuring an outlet temperature of the heat source water flowing out from the heat source outlet temperature measuring means,
An evaporation temperature correction step of calculating the evaporation temperature at which the ratio of the value obtained by subtracting the evaporation temperature from the temperature of the heat source water inlet to the value obtained by subtracting the heat source inlet temperature from the temperature of the heat source water outlet port is equal to the target ratio in the stable state and,
An expansion valve control step of performing an opening control of the expansion valve by using an evaporation pressure obtained from a corrected evaporation temperature in the evaporation temperature correction step
And a control device for controlling the turbo refrigerator.

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