CONTROL DEVICE AND CONTROL METHOD FOR EXTRACTION DEVICE

Abstract

The purpose of the present invention is to provide a control device which is for an extraction device, and is capable of estimating the total amount of air intrusion more accurately and optimizing the operation of the extraction device. A control device (7) that controls an extraction device (6) provided in a refrigerator (1) is provided with: an estimating unit that estimates the total amount of air intruding into the refrigerator (1); a determining unit that determines whether or not the total amount of air intrusion is equal to or greater than a preset allowable value; an activation control unit (6) that determines an activation duration time of the extraction device (6) on the basis of the total amount of air intrusion when the total amount of air intrusion is equal to or greater than the allowable value, and that activates the extraction device (6) for the activation duration time; an exhaust air amount calculation unit that calculates an amount of exhaust air that is the amount of air actually exhausted by the extraction device (6); and a correction unit that corrects at least one among the total amount of air intrusion and the activation duration time when the difference between the total amount of air intrusion and the amount of exhaust air is equal to or larger than a predetermined amount.

Description

TECHNICAL FIELD

The present invention relates to a chiller, and particularly to a control device and a control method for an extraction device.

BACKGROUND ART

A chiller that adopts a low-pressure refrigerant has a possibility that a non-condensable gas (mainly air) infiltrates into the chiller and stays in a condenser in a case where in particular sealability deteriorates since the inside of the chiller comes under a negative pressure according to an operation condition. In this state, a condensation pressure rises due to the non-condensable gas, and thereby there is a concern that the condenser does not operate normally. For this reason, in the related art, the non-condensable gas that has entered the device is discharged into the atmosphere by the extraction device.

Due to amendments to a CFC collection and destruction law and European F-gas regulations, it is desirable for the chiller to use a low-GWP refrigerant which is a low-pressure refrigerant. However, the low-GWP refrigerant is easily decomposed by oxygen, and thus there is a possibility that byproducts affecting safe operation of the chiller is generated. In a case where a non-condensable gas has infiltrated in the chiller using the low-GWP refrigerant, there is a possibility that the low-GWP refrigerant is decomposed and the operation of the chiller becomes unstable. For this reason, in order to maintain the safe operation of the chiller using the low-GWP refrigerant, it is necessary to highly accurately estimate and appropriately extract the amount of the non-condensable gas in the device (total amount of infiltrated air).

PTL 1 discloses a method of estimating a total amount of infiltrated air into a chiller according to a chiller structure and a pressure state and controlling the start of an extraction device based on the estimated total amount of infiltrated air.

CITATION LIST

Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No. 2016-65673

SUMMARY OF INVENTION

Technical Problem

However, since the total amount of infiltrated air changes according to various conditions such as external environments including humidity and an outside temperature, it is difficult to highly accurately estimate the total amount of infiltrated air. For this reason, under a situation where a possibility that a non-condensable gas infiltrates is low, a large air infiltration amount is estimated and the extraction device is operated uselessly in some cases.

In view of such circumstances, an object of the present invention is to provide a control device and a control method for an extraction device that can more accurately estimate a total amount of infiltrated air and further optimize operation of the extraction device.

Solution to Problem

According to a first aspect of the present invention, there is provided a control device that controls an extraction device provided in a chiller. The control device includes an estimating unit that estimates a total air infiltration amount into the chiller, a determination unit that determines whether or not the total air infiltration amount is equal to or larger than an allowable value set in advance, a starting control unit that determines a starting continuation time of the extraction device based on the total air infiltration amount and starts the extraction device for the starting continuation time in a case where the total air infiltration amount is equal to or larger than the allowable value, a discharge air amount calculating unit that calculates a discharge air amount, which is an amount of air actually discharged by the extraction device, and a correcting unit that corrects at least any one of the total air infiltration amount and the starting continuation time in a case where a difference between the total air infiltration amount and the discharge air amount is equal to or larger than a predetermined amount.

According to the configuration, since the discharge air amount, which is the amount of air actually extracted, is calculated, and at least any one of the total amount of infiltrated air and the starting continuation time of the extraction device is corrected with the use of the discharged air amount, the total amount of infiltrated air can be more accurately corrected according to an actual operation status of the chiller. Since the starting continuation time of the extraction device is determined based on the total amount of infiltrated air, the total amount of infiltrated air is indirectly corrected even in a case where the starting continuation time is corrected. That is, it is possible to more accurately estimate the total amount of infiltrated air according to an operation status. For example, even in a case where a low-GWP refrigerant is used as a refrigerant of the chiller, it is possible to more accurately estimate the total amount of infiltrated air. Thus, more stable operation can be maintained.

In the control device, the correcting unit may correct at least any one of the total amount of infiltrated air and the starting continuation time by multiplying the total amount of infiltrated air or the starting continuation time by a correction constant according to the difference between the total amount of infiltrated air estimated by the estimating unit and the discharge air amount.

According to the configuration, in a case where the difference between the estimated total amount of infiltrated air and the actual discharge air amount is large, correction can be performed with simple calculation of multiplying the air infiltration amount and/or the starting continuation time by the correction constant. For this reason, correction can be performed without a processing burden.

In the control device, the correction constant may be a value obtained by dividing the discharge air amount by the total amount of infiltrated air.

According to the configuration, since correction can be performed with simple calculation, correction can be performed without a processing burden.

In the control device, the chiller may be divided into a plurality of sections, an air infiltration effect degree may be set for each of the sections, the estimating unit may estimate an air infiltration amount for each of the sections and estimate the total amount of infiltrated air of the entire chiller from the estimated air infiltration amount of each of the sections, and the correcting unit may correct the air infiltration amount for each of the sections according to the air infiltration effect degree in a case of correcting the total amount of infiltrated air.

According to the configuration, since the air infiltration amount can be corrected for each section according to an air infiltration effect degree, it is possible to perform highly accurate correction according to an operation state of the chiller and a structure of each section. Since the respective sections have configurations different from each other, such as the number of couplings, the easiness of air infiltration (air infiltration effect degree) varies. For this reason, an air infiltration amount of a section where air infiltrates easily can be effectively corrected by performing correction according to an air infiltration effect degree. For this reason, the total amount of infiltrated air can be more accurately estimated.

According to a second aspect of the present invention, there is provided a chiller that adopts a low-pressure low-GWP refrigerant. The chiller includes an extraction device and the control device.

According to a third aspect of the present invention, there is provided a control method for an extraction device provided in a chiller. The control method includes an estimation step of estimating a total amount of infiltrated air into the chiller, a determination step of determining whether or not the total amount of infiltrated air is equal to or larger than an allowable value set in advance, a starting control step of determining a starting continuation time of the extraction device based on the total amount of infiltrated air and starting the extraction device for the starting continuation time in a case where the total amount of infiltrated air is equal to or larger than the allowable value, a discharge air amount calculation step of calculating a discharge air amount, which is an amount of air actually discharged by the extraction device, and a correction step of correcting at least any one of the total amount of infiltrated air and the starting continuation time in a case where a difference between the total amount of infiltrated air and the discharge air amount is equal to or larger than a predetermined amount.

Advantageous Effects of Invention

According to the present invention, an effect of more accurately estimating a total amount of infiltrated air and optimizing the operation of the extraction device can be achieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a schematic configuration of a chiller according to a first embodiment of the present invention.

FIG. 2 is a diagram showing functional blocks of a control device according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing flow of a control method for an extraction device according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing flow of a discharge air amount calculating method executed by the control device according to the first embodiment of the present invention.

FIG. 5 is a flowchart showing flow of a correcting method executed by the control device according to the first embodiment of the present invention.

FIG. 6 is a graph showing the amount of a non-condensable gas in a condenser of the chiller according to the first embodiment of the present invention.

FIG. 7 is a graph showing the amount of the non-condensable gas in the extraction device of the chiller according to the first embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereinafter, a first embodiment of a control device and a control method for an extraction device according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a chiller 1 according to the first embodiment of the present invention. As shown in FIG. 1, the chiller 1 according to the embodiment is a compression chiller, and is configured to mainly include a compressor 2 that compresses a refrigerant, a condenser 3 that condenses the high-temperature and high-pressure gas refrigerant compressed by the compressor 2, an expansion valve 4 that expands the liquid refrigerant from the condenser 3, an evaporator 5 that evaporates the liquid refrigerant expanded by the expansion valve 4, an extraction device 6 that discharges a non-condensable gas (mainly air) infiltrated in the chiller 1 to the atmosphere, and a control device 7 that control each unit included in the chiller 1.

A low-GWP refrigerant, which is a low-pressure refrigerant, is adopted as a refrigerant. Since the extraction device 6 according to the embodiment can accurately estimate the amount of the non-condensable gas infiltrated in the device through correction to be described later, it is possible to use various refrigerants without being limited to the low-GWP refrigerant.

The compressor 2 is, for example, a multi-state centrifugal compressor driven by a constant speed motor or a variable speed motor. The extraction device 6 is connected to the condenser 3 by a pipe 8, and a refrigerant gas (including a non-condensable gas) from the condenser 3 is led to an extraction tank 16 of the extraction device 6 through the pipe 8. The pipe 8 is provided with a valve 9 and a check valve 10, which are for controlling flowing and blocking of the refrigerant gas. As the control device 7 controls the opening and closing of the valve 9, the start and stop of the extraction device 6 are controlled. The check valve 10 prevents reverse flow of the refrigerant gas (including the non-condensable gas) from the extraction tank 16 to the condenser 3 in the extraction device 6.

The extraction device 6 includes, for example, the extraction tank 16 that condenses the refrigerant gas (including the non-condensable gas) supplied through the pipe 8 by cooling the refrigerant gas with a peltier element and separates the refrigerant gas from the non-condensable gas and a pump 11 that extracts the non-condensable gas accumulated in the extraction tank 16 into the atmosphere. In the extraction tank 16, the non-condensable gas is discharged into the atmosphere, and the refrigerant gas separated from the non-condensable gas returns to the evaporator 5 through a pipe 13 by controlling a valve 12. A configuration of the extraction device 6 is an example, and the extraction device is not limited to the configuration. Cooling with the use of the peltier element is also an example of a cooling method for condensing the refrigerant gas in the extraction tank 16, and the cooling method is not limited to the configuration.

The extraction tank 16 of the extraction device 6 is provided with a pressure sensor 14 and a temperature sensor 15 in order to monitor a state of the non-condensable gas accumulated therein (the presence or absence of the non-condensable gas or an accumulated amount). Measurement values from the sensors are transmitted to the control device 7, and are used in controlling the extraction device 6.

A configuration of the chiller 1 shown in FIG. 1 is an example, and the chiller is not limited to the configuration. For example, a configuration where an air heat exchanger is disposed instead of the condenser 3 and heat is exchanged between the cooled outside air and a refrigerant may be adopted. The chiller 1 is not limited to a case of having only a cooling function. For example, the chiller may have only a heating function or both of the cooling function and the heating function.

The control device 7 has a function of controlling the compressor 2 based on a measured value received from each of the sensors and a load rate sent from a higher system and a function of controlling the extraction device 6.

The control device 7 includes, for example, a central processing unit (CPU), a memory such as a random access memory (RAM), and a computer readable recording medium, which are not shown. A series of processes for realizing a variety of functions to be described later are stored, for example, in a recording medium in a form of program. A variety of functions to be described later are realized by the CPU reading the program from the RAM and executing processing and calculating of information.

FIG. 2 is a functional block diagram showing a control function of the extraction device 6 which is selected from functions included in the control device 7. As shown in FIG. 2, the control device 7 includes an estimating unit 21, a determination unit 22, a starting control unit 23, a storage unit 24, a discharge air amount calculating unit 25, and a correcting unit 26.

The estimating unit 21 estimates a total amount of infiltrated air with the use of an air infiltration effect degree indicating the easiness of air infiltration determined from a structural aspect of the chiller 1 and a function including a pressure as a parameter.

The air infiltration effect degree is, for example, an index indicating how large a gap, which has a possibility of allowing air (oxygen) to infiltrate into the chiller 1, and is stored in the storage unit 24 in advance. The air infiltration effect degree is determined by, for example, a structure, a size, and the number of couplings that connect a pipe. In consideration of a case where air infiltrates by permeating a resin material, an air infiltration effect degree may be set by adding information of the resin material.

In the embodiment, the chiller 1 is divided into a plurality of sections, and an air infiltration effect degree is set for each section.

Herein, it is possible for the chiller to be divided into sections as appropriate. For example, division into sections may be performed such that places showing the same tendency become one section from a perspective of whether or not a negative pressure is likely to be caused according to an operation condition (for example, whether the chiller is being operated or stopped) and a winter season or a summer season. For example, the vicinity of the evaporator 5 is likely to come under the negative pressure in the summer season, and a place other than a refueling system is likely to come under the negative pressure when the chiller is being operated or stopped in the winter season. Based on such a tendency, for example, the vicinity of the evaporator 5 may be determined as one section. As for places other than the vicinity of the evaporator, for example, each of the vicinity of the compressor 2 and the vicinity of the condenser 3 may be determined as one section.

The estimating unit 21 estimates an air infiltration amount for each section, for example, with the use of an air infiltration effect degree set for each section, a pressure of each section, and the atmospheric pressure. Specifically, in a case where a pressure of a section is higher than the atmospheric pressure, that is, in a case of a positive pressure, an air infiltration amount is zero. On the other hand, in a case where a pressure of a section is lower than the atmospheric pressure, that is, in a case of the negative pressure, a value obtained by multiplying the 1/2 power of a differential pressure between the pressure and the atmospheric pressure by an air infiltration effect degree is estimated as an air infiltration amount. When expressed into a formula, Expression (1) and Expression (2) below are obtained.

$\begin{array}{cc}\mathrm{In}a\mathrm{case}\mathrm{of}P\left(s\right)-\mathrm{Pat}\geqq 0\left(\mathrm{in}a\mathrm{case}\mathrm{of}a\mathrm{positive}\mathrm{pressure}\right)M\left(s\right)=0& \left(1\right)\\ \mathrm{In}a\mathrm{case}\mathrm{of}P\left(s\right)-\mathrm{Pat}<\left(\mathrm{in}a\mathrm{case}\mathrm{of}a\mathrm{negative}\mathrm{pressure}\right)\begin{array}{c}M\left(s\right)=E\left(s\right)\times f\left(P\left(s\right),\mathrm{Pat}\right)\\ =E\left(s\right)\times \sqrt{}P\left(s\right)-\mathrm{Pat}\end{array}& \left(2\right)\end{array}$

In Expression (1) and Expression (2), P(s) is a pressure [Pa(abs)] of a section s, Pat is the atmospheric pressure [Pa(abs)], M(s) is an air infiltration amount [m³] of the section s, and E(s) is an air infiltration effect degree [m³/Pa] of the section s. Without being limited to [m³] described above, for example, kg and mol may be used as the unit of an air infiltration amount.

The air infiltration amount M(s) of the section s indicates the amount of air estimated to be infiltrated in the section s per unit time (per one control cycle) in a state of a pressure of the section s and the atmospheric pressure.

When the air infiltration amount M(s) is estimated for each section in such a manner, the correcting unit 26 corrects the air infiltration amount M(s), and thereby an air infiltration amount Ma(s) is calculated. Then, the estimating unit 21 adds a value obtained by adding up the air infiltration amounts Ma(s) of the sections (an air infiltration amount Ms(s)) to a previously integrated value of air infiltration amounts, to calculate an integrated value of air infiltration amounts, that is, a total of the air infiltration amounts of the entire chiller 1 at the current time point (hereinafter, referred to as a “total amount of infiltrated air”). A formula thereof is Expression (3) below.

M(t)=M(t−1)+ΣMa(s)   (3)

In Expression (3), M(t) is a total amount of infiltrated air, M(t−1) is a previously integrated value of air infiltration amounts, and ΣMa(s) is a total value of air infiltration amounts for sections calculated this time.

The determination unit 22 determines whether or not the total amount of infiltrated air M(t) estimated by the estimating unit 21 is equal to or larger than an allowable value Mc set in advance.

The allowable value Mc is set, for example, based on a refrigerant chemical stability test and operation results. For example, a total amount of infiltrated air, at which decomposition of a refrigerant occurs, or a total amount of infiltrated air, at which safe operation of the chiller 1 is not inhibited, is acquired based on tests and operation results, and the allowable value is set to a value smaller than the total amount of infiltrated air.

Herein, it is necessary for the unit of the allowable value Mc and the unit of a total amount of infiltrated air are consistent with each other. For example, in a case where the unit of an allowable value is [mol] and the unit of a total amount of infiltrated air is other than [mol], the unit of the total amount of infiltrated air may be converted to the unit of the allowable value [mol], and the total amount of infiltrated air after conversion and the allowable value may be compared with each other.

In a case where the total amount of infiltrated air M(t) is equal to or larger than the allowable value Mc, the starting control unit 23 starts the extraction device 6. For example, the starting control unit 23 opens the valve 9 provided in the pipe 8 to start the extraction device 6. A starting continuation time of the extraction device 6 is determined at any time according to a ratio of the total amount of infiltrated air M(t) of the entire chiller 1 to a chiller capacity.

In a case where a starting continuation time is determined at any time according to a ratio of the total amount of infiltrated air M(t) of the entire chiller 1 to a chiller capacity, for example, Expression (4) below may be used.

tc=f[Vnc/Vc]  (4)

Vnc=M(t)+α  (5)

In Expression (4), tc is a starting continuation time [s] of the extraction device 6, and Vnc is the volume [m³] of a gas to be extracted and is calculated through Expression (5). Vc is an in-chiller volume [m³]. In Expression (5), the volume of a gas to be extracted is set slightly larger than the actual total amount of infiltrated air M(t) by adding a predetermined margin α to the total amount of infiltrated air M(t), and a margin is given to a starting continuation time to be calculated.

The starting continuation time tc of the extraction device 6 may be calculated through Expression (6) below in which the volume of a gas to be extracted and a pulling capacity of the extraction device 6 are parameters.

tc=f[Vnc/va]  (6)

In Expression (6), va is a pulling capacity [m³/s] of the extraction device 6.

In a case where a total amount of infiltrated air is smaller than an allowable value, the starting control unit 23 does not start the extraction device 6.

Information to be referred in the processing of the estimating unit 21 and the determination unit 22 described above is stored in advance in the storage unit 24. For example, in addition to the air infiltration effect degree E(s) of each section and the allowable value Mc, a constant included in each of Expressions (1)-(6) is registered in advance. A table, in which a difference between the estimated total amount of infiltrated air M(t) and a discharge air amount Md(t) and a correction constant c are set to correspond to each other, is stored in the storage unit 24. In a case where the total amount of infiltrated air M(t) is smaller than the discharge air amount Md(t), a correction constant is set to a value larger than 1. In a case where the total amount of infiltrated air M(t) is larger than the discharge air amount Md(t), the correction constant c is set to a value smaller than 1. The correction constant c is set according to a difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t), and is, for example, a value obtained by dividing the discharge air amount Md(t) by the total amount of infiltrated air M(t). Even in a case where the correction constant c is not stored as a table in the storage unit 24, a calculation formula may be stored to calculate the correction constant at the time of correction.

The discharge air amount calculating unit 25 calculates the discharge air amount Md(t), which is the amount of air actually extracted by the extraction device 6. When the extraction device 6 is actually operated, a non-condensable gas accumulates in the extraction tank 16 of the extraction device 6. Then, in a case where the non-condensable gas accumulated in the extraction tank 16 reaches a predetermined amount set in advance (a one-time discharge amount D1), the valve 9 is closed to stop supplying a refrigerant gas from the condenser 3, and the pump 11 provided in the extraction tank 16 is operated to discharge the non-condensable gas into the atmosphere. When the discharge of the non-condensable gas is completed, the valve 9 is opened again, and thereby the non-condensable gas accumulates in the extraction tank 16. Thus, the discharging operation described above is repeated until the discharge of the non-condensable gas is completed. The discharging operation is executed one time or a plurality of times according to the amount of the non-condensable gas actually accumulated in the chiller 1 for the set starting continuation time. Since the discharging operation is executed one time or a plurality of times for the starting continuation time of the extraction device 6, the discharge air amount Md(t), which is the amount of actually discharged air, can be calculated by measuring the one-time discharge amount D1 and the number of times n at which the discharging operation is executed.

The one-time discharge amount D1 is determined based on the capacity of the extraction device 6 (mainly the extraction tank 16). That is, when a non-condensable gas corresponding to the capacity of the extraction tank 16 is accumulated in the extraction device 6 (when the extraction tank 16 is full of the non-condensable gas), the accumulated non-condensable gas is discharged. In a case of discharging the non-condensable gas accumulated in the chiller 1 in a short period of time, it is preferable to use the extraction tank 16 having a large capacity in order to increase the one-time discharge amount. In a case of more accurately calculating a discharge air amount, which is the amount of air actually extracted, it is preferable to decrease the one-time discharge amount and enhance an estimated resolving power of the discharge air amount Md(t). In this case, the extraction tank 16 having a small capacity may be used.

The one-time discharge amount D1 may be determined at random with the capacity of the extraction device 6 (mainly the extraction tank 16) set as an upper limit. In this case, the amount of the non-condensable gas in the extraction tank 16 is estimated by the pressure sensor 14 and the temperature sensor 15, which are provided in the extraction device 6, and the estimated amount of the non-condensable gas and the predetermined amount which is determined at random (the one-time discharge amount D1) may be compared with each other.

In a case where a difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) is equal to or larger than a predetermined amount β, the correcting unit 26 corrects at least any one of the estimated total amount of infiltrated air M(t) and a starting continuation time. For this reason, the correcting unit 26 includes a correction necessity determination unit 31, a correction constant updating unit 32, and a correction executing unit 33. A case of correcting the total amount of infiltrated air M(t) in the embodiment will be described. The correction of the starting continuation time will be described in a modification example below.

The correction necessity determination unit 31 determines whether or not it is necessary to correct the total amount of infiltrated air M(t) by determining whether or not a difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) is equal to or larger than the predetermined amount β. As will be described later, in a case where it is necessary to correct the total amount of infiltrated air M(t), the correction constant c for correcting the estimated air infiltration amount M(s) of each section is updated, and consequently the total amount of infiltrated air M(t) is corrected. The predetermined amount β used by the correction necessity determination unit 31 is set within a range of an error, which is allowed for the discharge air amount, of the estimated total amount of infiltrated air M(t).

The correction constant updating unit 32 updates the correction constant in a case where the correction necessity determination unit 31 determines that the difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) is equal to or larger than the predetermined amount β. The correction constant is set to 1 as an initial set value, and the correction constant is updated each time the correction necessity determination unit 31 determines that it is necessary to correct the total amount of infiltrated air M(t). Specifically, in a case where it is determined that it is necessary to correct the total amount of infiltrated air M(t), the correction constant updating unit 32 reads a correction constant according to the difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) from the storage unit 24, and performs update by multiplying a correction constant which is set up until then by the read correction constant. For example, in a case where a correction constant of 1.1 is read from the storage unit 24 by the correction constant updating unit 32 in a state where the correction constant is set to 1.2, the correction constant is updated to a new correction constant through 1.2×1.1=1.32. The correction constant is updated by being multiplied by a new correction constant each time it is determined that it is necessary to correct the total amount of infiltrated air M(t).

The correction executing unit 33 calculates the air infiltration amount Ma(s) by multiplying the air infiltration amount M(s) of each section estimated by the estimating unit 21 by the correction constant. Then, the estimating unit 21 calculates the total amount of infiltrated air M(t) with the use of the air infiltration amount Ma(s) calculated by the correction executing unit 33.

Next, a control method for the extraction device 6 by the control device 7 described above will be described with reference to FIG. 3. The correction constant c is set to 1 as an initial value. In a case where the correction constant is updated by the correcting unit 26, the updated correction constant c is used.

First, measurement values of the pressure P(s) of each section and the atmospheric pressure Pat are acquired from a variety of sensors (for example, the pressure sensor and the temperature sensor (not shown in FIG. 1)) provided in the chiller 1 and near the chiller 1 (S301).

Next, the air infiltration amount M(s) of each section is calculated with the use of the pressure P(s) of each section and the atmospheric pressure Pat (S302).

Next, the air infiltration amount M(s) estimated for each section is corrected (S303). Specifically, the air infiltration amount Ma(s) is calculated by multiplying the air infiltration amount M(s) by the correction constant. Since the correction constant c is set to 1 as an initial value, M(s)=Ma(s) is satisfied in a case where the correction constant is not updated. In a case where the correction constant is updated, the updated correction constant (≠1) is used, and thus M(s)≠Ma(s) is satisfied.

Next, the total amount of infiltrated air M(t) is calculated by adding the value ΣMa(s) obtained by adding the air infiltration amounts Ma(s) of respective sections to the previously integrated value M(t−1) of air infiltration amounts (S304).

Next, whether or not the total amount of infiltrated air M(t) is equal to or larger than the allowable value Mc is determined (S305). Herein, in a case where the units of both of the total amount of infiltrated air and the allowable value do not match each other, the total amount of infiltrated air and the allowable value are compared with each other after performing processing of converting one unit to match the other unit.

In a case where the total amount of infiltrated air M(t) is equal to or larger than the allowable value Mc (determination of YES in S305) in S305, a starting continuation time is calculated based on the total amount of infiltrated air M(t) (S306). Then, the extraction device 6 is started (S307). Next, whether or not the starting continuation time has elapsed is determined (S308). In a case where the starting continuation time has elapsed, the extraction device 6 is stopped (S309).

Next, the previously integrated value M(t−1) of air infiltration amounts is set to zero (S310).

On the other hand, in a case where the total amount of infiltrated air M(t) is smaller than the allowable value Mc in S305, the total amount of infiltrated air M(t) calculated this time is set to the previously integrated value M(t−1) of air infiltration amounts (S311).

The processing is continuously performed at fixed time intervals, for example, regardless of the fact that the chiller 1 is being operated and being stopped.

Next, a discharge air amount calculating method for the extraction device 6 by the control device 7 described above will be described with reference to FIG. 4.

In a flowchart shown in FIG. 4, an operation starts when the extraction device 6 is started by the starting control unit 23.

First, when the extraction device 6 is started by the starting control unit 23, the number of times of discharging operation n=0 is set (S401).

Next, in a case where whether or not the starting continuation time has elapsed is determined (S402) and the starting continuation time has not elapsed (determination of NO in S402), whether or not the discharging operation is performed by the extraction device 6 is determined (S403). In a case where it is determined that the discharging operation is not performed (determination of NO in S403), whether or not the starting continuation time has elapsed is determined again (S402). Through the operation in S402 and S403, whether or not the discharging operation is performed within the starting continuation time is determined.

In a case where it is determined that the discharging operation of the extraction device 6 is performed (determination of YES in S403), the number of times of discharging operation n is counted up (plus one time) (S404). When the counting-up of the number of times of discharging operation n is finished, processing returns to S402, and the processing described above is repeated.

In a case where it is determined that the starting continuation time has elapsed (determination of YES in S402), the discharge air amount Md(t), which is the amount of air actually extracted, is calculated (S405). Specifically, in S405, the discharge air amount Md(t) is calculated by multiplying the discharge amount D1 of a non-condensable gas in one time of the discharging operation of the extraction device 6 by the number of times of discharging operation n.

Next, a correcting method for the control device 7 described above will be described with reference to FIG. 5.

A flowchart shown in FIG. 5 is executed after the discharging operation of the extraction device 6 is all completed and the discharge air amount Md(t) is calculated. The flowchart shown in FIG. 5 is executed each time the discharging operation of the extraction device 6 is completed.

First, whether or not a difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) (absolute value) is equal to or larger than the predetermined amount β is determined (S501). In a case where the difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) (absolute value) is smaller than the predetermined amount β (determination of NO in S501), a correction constant is not updated (S502).

In a case where the difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) (absolute value) is equal to or larger than the predetermined amount β (determination of YES in S501), a correction constant according to the difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) is read from the storage unit 24 (S503). Then, the read correction constant is updated by being multiplied by the correction constant set up until then (S504).

Next, the discharging operation of a non-condensable gas by the control device 7 described above will be described with reference to FIGS. 6 and 7. FIG. 6 is a graph showing the amount of a non-condensable gas in the condenser 3 of the chiller 1 according to the embodiment. FIG. 7 is a graph showing the amount of a non-condensable gas in the extraction device 6 of the chiller 1 according to the embodiment.

As shown in FIG. 6, the non-condensable gas accumulates in the chiller 1 according to an operation state of the chiller 1 and external environments. The amount of the non-condensable gas that is being accumulated is estimated by the estimating unit 21, and is accurately estimated as the correcting unit 26 performs correction. Then, in a case where the amount of the non-condensable gas accumulated in the condenser 3 (the total amount of infiltrated air M(t)) exceeds the allowable value Mc, the extraction device 6 is started, and the non-condensable gas accumulated in the condenser 3 is pulled out by the extraction device 6.

As shown in FIG. 7, in a case where the amount of the non-condensable gas accumulated in the condenser 3 (the total amount of infiltrated air M(t)) exceeds the allowable value Mc, the extraction device 6 is started, and the non-condensable gas is pulled out from the condenser 3. For this reason, the non-condensable gas accumulates in the extraction device 6. Then, in a case where the non-condensable gas accumulated in the extraction device 6 reaches the predetermined discharge amount D1, the valve 9 is closed, and the non-condensable gas is discharged into the atmosphere by the pump 11. Through the discharging operation, most of the non-condensable gas accumulated in the extraction device 6 is discharged. Then, as the valve 9 is opened again, the non-condensable gas is pulled out from the condenser 3 to the extraction device 6, and the non-condensable gas accumulates in the extraction device 6. Then, the discharging operation is repeatedly performed as described above. Although a case where the discharging operation is performed two times by the extraction device 6 in order to discharge the entire non-condensable gas accumulated in the condenser 3 is described in an example shown in FIG. 7, the invention is not limited to the example.

Although the correcting unit 26 calculates the air infiltration amount Ma(s) by correcting the air infiltration amount M(s) of each section estimated by the estimating unit 21 and the estimating unit 21 calculates a value by adding up the air infiltration amounts Ma(s), a value to be corrected by the correcting unit 26 is not limited to the air infiltration amount M(s) of each section estimated by the estimating unit 21. For example, when the estimating unit 21 estimates the air infiltration amount M(s) of each section, a value obtained by adding up the air infiltration amounts M(s) of respective sections (the air infiltration amount Ms(s)) is calculated. Then, the correcting unit 26 may correct the value obtained by adding up the air infiltration amounts M(s) of the respective sections (the air infiltration amount Ms(s)). Specifically, the correcting unit 26 corrects the air infiltration amount Ms(s) by multiplying the value obtained by adding up the air infiltration amounts M(s) of the respective sections estimated by the estimating unit 21 (the air infiltration amount Ms(s)) by the correction constant, and calculates the total amount of infiltrated air M(t) by adding the previously integrated value M(t−1) of air infiltration amounts to the value. Whether or not the total amount of infiltrated air M(t) calculated in such a manner is equal to or larger than the allowable value Mc set in advance is determined by the determination unit 22.

Next, a modification example of a correction target in the embodiment will be described. Although a total amount of infiltrated air is corrected in the first embodiment, instead of the correction of the total amount of infiltrated air or in addition to the correction of the total amount of infiltrated air, a starting continuation time set by the starting control unit 23 is corrected in the modification example. Since the starting continuation time is determined by the total amount of infiltrated air M(t), the total amount of infiltrated air M(t) is indirectly corrected even when the starting continuation time is corrected.

In the modification example, the storage unit 24 stores a table, in which a difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) and a correction constant c′ for correcting a starting continuation time are set to correspond to each other. Specifically, in a case where the correction necessity determination unit 31 determines that it is necessary to correct the total amount of infiltrated air M(t), the correction constant updating unit 32 reads the correction constant c′ for correcting a starting continuation time according to the difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t) from the storage unit 24, and updates the read correction constant by setting as a new correction constant. Then, the correction executing unit 33 performs correction by multiplying the starting continuation time by the new correction constant.

Next, a modification example of a correction constant in the embodiment will be described. In a case where an air infiltration effect degree is set for each section and the correcting unit 26 corrects a total amount of infiltrated air, an air infiltration amount is corrected for each section according to an air infiltration effect degree in the modification example.

For this reason, in the modification example, the storage unit 24 stores an addition constant corresponding to an air infiltration effect degree of each section. The correction executing unit 33 calculates the air infiltration amount Ma(s) by multiplying the air infiltration amount M(s) of each section estimated by the estimating unit 21 by a correction constant and adding the addition constant corresponding to each section. In a case where the correction constant updating unit 32 does not update the correction constant (a case of c=1), the addition constant is not added.

In consideration of an air infiltration effect degree of each section, the addition constant allows more effective correction. For this reason, the addition constant is set in advance through experiments according to an air infiltration effect degree.

For this reason, since the air infiltration amount M(s) of each section is corrected in consideration of an air infiltration effect degree of each section in the modification example, the air infiltration amount M(s) of each section can be more accurately corrected. That is, the total amount of infiltrated air M(t) calculated from the air infiltration amount M(s) of each section can also be more accurately corrected.

Although the correcting unit 26 (the correction executing unit 33) corrects the air infiltration amount M(s) of each section (calculates the air infiltration amount Ma(s)) by multiplying the air infiltration amount M(s) of each section estimated by the estimating unit 21 by a correction constant and adding an addition constant corresponding to each section in the modification example, correction performed by the correcting unit 26 is not limited to the description above. For example, first, the correcting unit 26 corrects the air infiltration amount M(s) of each section (weighting) by adding an addition constant corresponding to each section to the air infiltration amount M(s) of each section estimated by the estimating unit 21. Then, the correcting unit 26 may correct (calculate the air infiltration amount Ma(s)) by multiplying a total value of the corrected air infiltration amounts M(s) for respective sections by a correction constant. That is, the correcting unit 26 may correct (multiplication of a correction constant) the air infiltration amount M(s) estimated for each section after weighting (addition of an addition constant) is performed according to an air infiltration effect degree.

In the control device and the control method for an extraction device according to the embodiment as described above, the amount of a non-condensable gas infiltrated in the chiller 1 is estimated as a total amount of infiltrated air, and the estimated total amount of infiltrated air and/or a starting continuation time of the extraction device 6 is corrected based on a discharge air amount, which is the amount of air actually discharged by the extraction device 6. For this reason, according to an actual operation status of the chiller 1, the air infiltration amount and the starting continuation time of the extraction device 6 can be appropriately corrected. Since the starting continuation time of the extraction device 6 depends on an air infiltration amount, the total amount of infiltrated air is indirectly corrected even in a case of correcting the starting continuation time. That is, it is possible to more accurately estimate a total amount of infiltrated air according to an operation status. For example, even in a case where a low-GWP refrigerant is used as a refrigerant of the chiller 1, it is possible to more accurately estimate an air infiltration amount. Thus, more stable operation can be maintained. Since an air infiltration amount can be more accurately estimated, the start of the extraction device 6 is optimized, and thus unnecessary power consumption can be suppressed.

Further, since correction is performed with simple calculation of multiplying an air infiltration amount and/or a starting continuation time by a correction constant, correction can be performed without a processing burden.

Second Embodiment

Next, a control device and a control method for an extraction device according to a second embodiment of the present invention will be described.

Although an air infiltration amount is estimated for each section in the first embodiment described above, the embodiment is different in that the total amount of infiltrated air M(t) of the entire chiller 1 is directly estimated without performing division into sections. That is, the chiller 1 in the embodiment is different from the first embodiment in terms of a calculation method of the total amount of infiltrated air M(t) by the estimating unit 21. Hereinafter, points of the chiller 1 according to the embodiment, which are different from the first embodiment, will be mainly described.

The estimating unit 21 according to the embodiment calculates the current total amount of infiltrated air M(t) with the use of Expression (7) below.

M(t)=f(Mb×f(Ec′/Vc)×f(Pet, Pct))+M(t−1)   (7)

In Expression (7), Mb is an air infiltration amount of a reference chiller, f(Ec′/Vc) is a function having an air infiltration effect degree and an in-chiller volume as parameters, Ec′ is an air effect degree of the entire chiller 1 relatively determined based on a structural difference from the reference chiller, Vc is an in-chiller volume, and f(Pet, Pct) is a function having an evaporation pressure Pet and a condensation pressure Pct as parameters. That is, Mb×f(Ec′/Vc)×f(Pet, Pct) in Expression (7) indicates the amount of air estimated to be infiltrated in the entire chiller 1 per unit time (per one control cycle). f(Mb×f(Ec′/Vc)×f(Pet, Pct)) is a function having Mb×f(Ec′/Vc)×f(Pet, Pct) as a parameter. Specifically, f(Mb×f(Ec′/Vc)×f(Pet, Pct)) indicates correction of the amount of air estimated to be infiltrated in the entire chiller 1 (Mb×f(Ec′/Vc)×f(Pet, Pct)).

As shown in Expression (7), the current total amount of infiltrated air M(t) is calculated by adding the previously integrated value M(t−1) of air infiltration amounts to a value obtained by correcting the amount of air estimated to be infiltrated in the entire chiller 1 (Mb×f(Ec′/Vc)×f(Pet, Pct)).

Herein, the function (Ec′/Vc) having an air infiltration effect degree and an in-chiller volume as parameters functions as a coefficient relatively indicating the easiness of air infiltration in a structural aspect. That is, the higher a value of the function, the more easily air infiltrates from a structure surface than the reference chiller. The function f(Pet, Pct) of an evaporation temperature and a condensation temperature functions as a coefficient indicating the easiness of air infiltration from a perspective of a pressure (a differential pressure between a pressure and the atmospheric pressure). That is, the lower a pressure of the evaporator 5 and a pressure of the condenser 3, the more easily air infiltrates. Therefore, the higher the function value, the more easily air infiltrates from a perspective of a pressure.

The storage unit 24 in the embodiment stores a correction constant c″ based on a difference between the estimated total amount of infiltrated air M(t) and the discharge air amount Md(t), which is for correcting the amount of air estimated to be infiltrated in the entire chiller 1 (Mb×f(Ec′/Vc)×f(Pet, Pct)). The correcting unit performs correction by multiplying Mb×f(Ec′/Vc)×f(Pet, Pct) in Expression (7) by the correction constant c″. That is, specifically, f(Mb×f(Ec′/Vc)×f(Pet, Pct)) indicates multiplying Mb×f(Ec′/Vc)×f(Pet, Pct) by the correction constant c″. The determination unit 22 compares the total amount of infiltrated air M(t) calculated through Expression (7) and the allowable value Mc with each other.

In the control device 7 and the control method for the extraction device 6 of the chiller 1 according to the embodiment, it is possible to reduce a processing burden when calculating an air infiltration amount since it is not necessary to perform division into respective sections as in the first embodiment. Further, since a value relatively determined from a structural difference from the reference chiller is used also for an air infiltration effect degree, it is possible to reduce an effort that takes when determining an air infiltration effect degree. Then, since the total amount of infiltrated air M(t) estimated by the estimating unit 21 is corrected based on a discharge air amount, it is possible to more accurately estimate the amount of a non-condensable gas infiltrated in the chiller 1.

The present invention is not limited to only the embodiments described above, and it is possible to execute various modifications without departing from the gist of the invention.

For example, although a case where the control device 7 of the chiller 1 has a function of controlling the extraction device 6 is described in each of the embodiments, without being limited to this example, for example, a control device dedicated for the extraction device 6 may be separately provided with the control function of the extraction device 6 separated from the control device 7.

Although the extraction device 6 is connected to the condenser 3 by the pipe 8 in each of the embodiments, the extraction device may be connected to a place by other pipes insofar as air stays easily in the place, in addition to the condenser 3. By connecting the place where air stays easily and the extraction device 6 to each other as described above, it is possible to efficiently discharge air in the device.

Further, although the extraction device 6 is started based on an air infiltration amount in each of the embodiments, there is a possibility that a refrigerant is adversely affected by other substances such as moisture. Therefore, infiltration amounts of other substances such as moisture are estimated in addition to the air infiltration amount, and the start and stop of means of removing or reducing the substances according to the estimated infiltration amounts may be controlled. A configuration where a structure that can remove other substances at all times (moisture removal by a filter dryer) is provided and other substances are removed at all times may be adopted.

REFERENCE SIGNS LIST

1: chiller

2: compressor

3: condenser

4: expansion valve

5: evaporator

6: extraction device

7: control device

8, 13: pipe

9, 12: valve

10: check valve

11: pump

14: pressure sensor

15: temperature sensor

16: extraction tank

21: estimating unit

22: determination unit

23: starting control unit

24: storage unit

25: discharge air amount calculating unit

26: correcting unit

31: correction necessity determination unit

32: correction constant updating unit

33: correction executing unit

Claims

1. A control device that controls an extraction device provided in a chiller, the control device comprising:

an estimating unit that estimates a total amount of infiltrated air into the chiller;

a determination unit that determines whether or not the total amount of infiltrated air is equal to or larger than an allowable value set in advance;

a starting control unit that determines a starting continuation time of the extraction device based on the total amount of infiltrated air and starts the extraction device for the starting continuation time in a case where the total amount of infiltrated air is equal to or larger than the allowable value;

a discharge air amount calculating unit that calculates a discharge air amount, which is an amount of air actually discharged by the extraction device; and

a correcting unit that corrects at least any one of the total amount of infiltrated air and the starting continuation time in a case where a difference between the total amount of infiltrated air and the discharge air amount is equal to or larger than a predetermined amount.

2. The control device according to claim 1,

wherein the correcting unit corrects at least any one of the total amount of infiltrated air and the starting continuation time by multiplying the total amount of infiltrated air or the starting continuation time by a correction constant according to the difference between the total amount of infiltrated air estimated by the estimating unit and the discharge air amount.

3. The control device according to claim 2,

wherein the correction constant is a value obtained by dividing the discharge air amount by the total amount of infiltrated air.

4. The control device according to claim 1,

wherein the chiller is divided into a plurality of sections,

an air infiltration effect degree is set for each of the sections,

the estimating unit estimates an air infiltration amount for each of the sections and estimates the total amount of infiltrated air of the entire chiller from the estimated air infiltration amount of each of the sections, and

the correcting unit corrects the air infiltration amount for each of the sections according to the air infiltration effect degree in a case of correcting the total amount of infiltrated air.

5. A chiller that adopts a low-pressure low-GWP refrigerant, the chiller comprising:

an extraction device; and

the control device according to claim 1.

6. A control method for an extraction device provided in a chiller, the control method comprising:

an estimation step of estimating a total amount of infiltrated air into the chiller;

a determination step of determining whether or not the total amount of infiltrated air is equal to or larger than an allowable value set in advance;

a starting control step of determining a starting continuation time of the extraction device based on the total amount of infiltrated air and starting the extraction device for the starting continuation time in a case where the total amount of infiltrated air is equal to or larger than the allowable value;

a discharge air amount calculation step of calculating a discharge air amount, which is an amount of air actually discharged by the extraction device; and

a correction step of correcting at least any one of the total amount of infiltrated air and the starting continuation time in a case where a difference between the total amount of infiltrated air and the discharge air amount is equal to or larger than a predetermined amount.

7. A chiller that adopts a low-pressure low-GWP refrigerant, the chiller comprising:

an extraction device; and

the control device according to claim 2.

8. A chiller that adopts a low-pressure low-GWP refrigerant, the chiller comprising:

an extraction device; and

the control device according to claim 3.

9. A chiller that adopts a low-pressure low-GWP refrigerant, the chiller comprising:

an extraction device; and

the control device according to claim 4.