The present disclosure relates to a method for controlling an operation of an ice-making machine. More specifically, the present disclosure relates to a method for controlling an operation of an ice-making machine configured to make sherbet-like ice slurry.
Sherbet-like ice slurry has occasionally been used for refrigerating fish and the like. Heretofore, for example, a double pipe ice-making machine including an inner pipe and an outer pipe has been known as an apparatus for making such ice slurry (refer to, for example, Patent Literature 1). An ice-making system that includes such an ice-making machine also includes a tank for storing a medium to be cooled, such as seawater. The medium to be cooled is supplied from the tank to an inner pipe of the ice-making machine, and ice slurry is made through heat exchange of the medium to be cooled with a refrigerant supplied to an annular space between an outer pipe and the inner pipe of the ice-making machine. The ice slurry thus made is returned to the tank.
Patent Literature 1: Japanese Patent No. 3,888,789
A method for controlling an operation of an ice-making machine (hereinafter, also simply referred to as an “operation control method”) according to a first aspect of the present disclosure has the following configurations.
(1) A method for controlling an operation of an ice-making machine configured to make ice by cooling a medium to be cooled, through heat exchange with a refrigerant,
the method including:
increasing an evaporation temperature of the refrigerant to be supplied to the ice-making machine when a drive current for an ice scraper of the ice-making machine is more than a first current value.
Hereinafter, a specific description will be given of an operation control method according to the present disclosure with reference to the accompanying drawings. The present disclosure is not limited to the following exemplary description, and all changes that fall within metes and bounds of the claims, or equivalence such metes and bounds thereof are therefore intended to be embraced by the claims.
First, a description will be given of an exemplary ice-making system including an ice-making machine to which an operation control method according to the present disclosure is applied.
The ice-making system A adopts seawater as a medium to be cooled. The ice-making system A also includes, in addition to the ice-making machine 1 serving as a part of a utilization-side heat exchanger, a compressor 2, a heat source-side heat exchanger 3, a four-way switching valve 4, a utilization-side expansion valve 5, a heat source-side expansion valve 6, a superheater 7, a receiver 8, a seawater tank (a reservoir tank) 9, and a pump 10. The ice-making machine 1, the compressor 2, the heat source-side heat exchanger 3, the four-way switching valve 4, the utilization-side expansion valve 5, the heat source-side expansion valve 6, the superheater 7, and the receiver 8 each serve as a part of a refrigeration apparatus. These apparatuses or members are interconnected via pipes to form a refrigerant circuit. The ice-making machine 1, the seawater tank 9, and the pump 10 are interconnected via pipes to form a seawater circuit. In the ice-making system A, each of the ice-making machine 1, the compressor 2, the heat source-side heat exchanger 3, the four-way switching valve 4, the utilization-side expansion valve 5, the heat source-side expansion valve 6, the superheater 7, the receiver 8, and the like is an equipment-side element, and each of the seawater tank 9, the pump 10, the pipes, and the like is a facility-side element.
The ice-making system A also includes a control apparatus 30. The control apparatus 30 includes a central processing unit (CPU) and a memory such as a random access memory (RAM) or a read only memory (ROM). The control apparatus 30 achieves various kinds of control concerning an operation of the ice-making system A, including the operation control according to the present disclosure, in such a manner that the CPU executes a computer program stored in the memory.
In a normal ice-making operation, the four-way switching valve 4 is maintained at a state indicated by a solid line in
In the annular space 14, the refrigerant evaporates by heat exchange with the seawater which the pump 10 supplies into the inner pipe 12. The seawater is cooled by the evaporation of the refrigerant. The seawater then returns to the seawater tank 8 via the inner pipe 12. The refrigerant gasifies by the evaporation in the ice-making machine 1. Thereafter, the refrigerant is sucked into the compressor 2. At this time, if the refrigerant that is not sufficiently evaporated in the ice-making machine 1 and slightly left liquefied is sucked into the compressor 2, an abrupt increase in pressure inside a compressor cylinder (liquid compression) or a decrease in viscosity of a refrigerating machine oil causes a failure in the compressor 2. In order to protect the compressor 2, the refrigerant from the ice-making machine 1 is heated by the superheater 7 before being sucked into the compressor 2. The superheater 7 is of a double pipe type. The refrigerant from the ice-making machine 1 is superheated when passing a space between an inner pipe and an outer pipe of the superheater 7. The refrigerant thus superheated then returns to the compressor 2.
If the flow of the seawater is stagnated in the inner pipe 12 of the ice-making machine 1, the ice is accumulated in the inner pipe 12 (ice accumulation) to hinder the operation of the ice-making machine 1. In this case, a defrosting operation (a heating operation) is performed for melting the ice in the inner pipe 12. At this time, the four-way switching valve 4 is maintained at a state indicated by a broken line in
The ice-making machine 1 is a portrait-oriented double pipe ice-making machine that includes the evaporator E including the inner pipe 12 and the outer pipe 13 whose axes extend horizontally, and an ice scraper to be described later. The evaporator E is of a flooded type, in which most of the annular space 14 between the inner pipe 12 and the outer pipe 13 is filled with the liquid refrigerant. The evaporator E thus enhances heat exchange efficiency of the refrigerant with the seawater. In addition, when most of the annular space 14 is filled with the liquid refrigerant, the refrigerating machine oil is easily discharged from the flooded-type evaporator. The refrigerating machine oil returns to the compressor 2 to compensate for unsatisfactory lubrication of the compressor 2, leading to improvement in reliability.
The inner pipe 12 is an element through which the seawater serving as a medium to be cooled passes. The inner pipe 12 is made of a metal material such as stainless steel or iron. The inner pipe 12 has a cylindrical shape, and is disposed in the outer pipe 13. The inner pipe 12 has two ends that are closed. In the inner pipe 12, the ice scraper 15 is disposed to scrape sherbet-like ice slurry off an inner peripheral face of the inner pipe 12 and to disperse the sherbet-like ice slurry in the inner pipe 12. The inner pipe 12 is connected at its first axial end (the right side in
The outer pipe 13 has a cylindrical shape, and is made of a metal material such as stainless steel or iron as in the inner pipe 12. The outer pipe 13 is connected at its lower side to a plurality of refrigerant inlet pipes 18 (three refrigerant inlet pipes 18 in
As illustrated in
The annular space 14 is defined with an outer peripheral face of the inner pipe 12 and an inner peripheral face of the outer pipe 13 to form refrigerant paths that extend from the refrigerant supply ports 20 on the lower side of the outer pipe 13 to the refrigerant discharge ports 21 on the upper side of the outer pipe 13.
Next, a description will be given of a method for controlling an operation of the ice-making machine 1 in the ice-making system A. More specifically, a description will be given of an operation control method that involves changing operating conditions of the ice-making machine 1, stopping the ice-making machine 1, or restarting the ice-making machine 1, based on an ice packing factor in the seawater tank 9.
In the ice-making system A, as the ice packing factor IPF in the seawater tank 9 increases through the operation of the ice-making machine 1, the amount of ice to be discharged from the seawater tank 9 increases, and the amount of ice in the inner pipe 12 of the ice-making machine 1 also increases. The increase in amount of ice in the inner pipe 12 causes an increase in driving torque of the motor 26 in the ice scraper 15 that scrapes the sherbet-like ice slurry off the inner peripheral face of the inner pipe 12. The increase in driving torque causes an increase in drive current of the motor 26. In the first embodiment, the operation of the ice-making machine 1 is controlled using a drive current value of the motor 26 in the ice scraper 15, the drive current value being detected by the ammeter 31 and transmitted to the control apparatus 30.
If the ice is excessively retained in the seawater tank 9 due to the increase in ice packing factor IPF of the seawater in the seawater tank 9, the seawater containing a large amount of ice flows into the ice-making machine 1, so that the current value of the motor 26 in the ice scraper 15 becomes larger than usual. In the first embodiment, when the current of the motor 26 exceeds a first current value, an evaporation temperature of the refrigerant to be supplied to the ice-making machine 1 is increased.
In the first embodiment, when the current value exceeds a second current value (e.g., 11 A) larger than the first current value, a thermostat is forcibly turned off to stop the operation of the ice-making machine 1. In other words, the operation of the compressor 2 is stopped to stop the circulation of the refrigerant through the refrigerant circuit. It should be noted that the ice scraper 15 is continuously operated even when the thermostat is forcibly turned off. After the thermostat is forcibly turned off, when the current value of the motor 26 decreases to a certain value, for example, 9 A, the thermostat, which has been forcibly turned off, is turned on again to restart the operation of the compressor 2.
According to the conventional art, the operation control is not performed. Consequently, when the amount of ice in the inner pipe 12 exceeds a certain amount as the ice packing factor IPF increases with a lapse of a time, the drive current of the motor 26 sharply increases. Then, when the drive current exceeds a predetermined value A1, an overcurrent protective device is operated to stop the operation of the motor 26. In this case, since the motor 26 continuously operates at a high torque until the operation of the motor 26 is stopped, the blades 24, the support bars 23, and the like of the ice scraper 15 are possibly damaged.
The operation control according to the first embodiment is equal to that according to the conventional art in the current value of the motor 26 until the time t1 at which the amount of ice in the inner pipe 12 reaches a certain amount. According to the first embodiment, however, the current value of the motor 26 gradually increases after the time t1. Since the amount of ice is decreased in such a manner that the value of the evaporation temperature is set larger than usual in accordance with the increase in current value as described above, the increase in current value in the first embodiment is gentler than that in the conventional art.
When the current value of the motor 26 exceeds the second current value, that is, 11 A at the time t2, the thermostat is forcibly turned off to stop the operation of the ice-making machine 1. With this configuration, since ice is not newly made although the ice slurry in the seawater tank 9 is used, the amount of ice in the inner pipe 12 gradually decreases, and the drive current of the motor 26 also gradually decreases with this decrease. When the current value of the motor 26 falls below 9 A at a time t3, the thermostat, which has been forcibly turned off, is turned on again to restart the operation of the ice-making machine 1. The amount of ice in the inner pipe 12 increases again after the restart of the operation of the ice-making machine 1. When the current value of the motor 26 exceeds 11 A at a time t4, the thermostat is forcibly turned off again to stop the operation of the ice-making machine 1.
In the first embodiment, the operation of the ice-making machine 1 that is an equipment-side element is controlled based on the current value of the motor 26 of the ice scraper 15 in the ice-making machine 1. This configuration thus improves the reliability of operation control on the ice-making machine 1 irrespective of occurrence of, for example, abnormal communications with an equipment side in the conventional art. This configuration enables a reduction in risk of damage to the blades 24 and the support bars 23 of the ice scraper 15 due to ice made excessively, and improves the reliability of the ice-making system A as a system.
In the first embodiment, the evaporation temperature is increased stepwise in accordance with an excess of the current from the first current value. This configuration therefore enables stepwise reduction in amount of ice to be made by the ice-making machine 1.
In order to control the operation of the ice-making machine 1, a second embodiment focuses attention on an increase in pressure loss of the seawater flowing through the inner pipe 12 of the ice-making machine 1 from the inlet toward the outlet with an increase in amount of ice in the inner pipe 12. According to the second embodiment, specifically, the evaporation temperature of the refrigerant to be supplied to the ice-making machine 1 is increased when a pressure difference between a pressure of the seawater (the medium to be cooled) at the inlet of the ice-making machine 1 and a pressure of the seawater at the outlet of the ice-making machine 1 exceeds a first pressure value. In the second embodiment, a pressure sensor 32 detects a pressure of the seawater at the seawater inlet pipe 16 of the ice-making machine 1, and a pressure sensor 33 detects a pressure of the seawater at the seawater outlet pipe 17 of the ice-making machine 1 (see
In the second embodiment, when the pressure difference exceeds a second pressure value larger than the first pressure value, the thermostat is forcibly turned off to stop the operation of the ice-making machine 1. In other words, the operation of the compressor 2 is stopped to stop the circulation of the refrigerant through the refrigerant circuit. It should be noted that the ice scraper 15 is continuously operated even when the thermostat is forcibly turned off. After the thermostat is forcibly turned off, when the pressure difference decreases to a certain value, for example, 0.06 MPa, the thermostat, which has been forcibly turned off, is turned on again to restart the operation of the compressor 2.
According to the second embodiment, the operation of the ice-making machine 1 that is an equipment-side element is controlled based on the pressure difference between the pressure of the seawater (the medium to be cooled) at the seawater inlet pipe 16 of the ice-making machine 1 and the pressure of the seawater at the seawater outlet pipe 17 of the ice-making machine 1. This configuration thus improves the reliability of operation control on the ice-making machine 1 irrespective of occurrence of, for example, abnormal communications with an equipment side in the conventional art. This configuration enables a reduction in risk of damage to the blades 24 and the support bars 23 of the ice scraper 15 due to ice made excessively, and improves the reliability of the ice-making system A as a system.
In the second embodiment, the evaporation temperature is increased stepwise in accordance with an excess of the pressure difference from the first pressure value. This configuration therefore enables stepwise reduction in amount of ice to be made by the ice-making machine 1.
The present disclosure is not limited to the foregoing embodiments, and various modifications may be made within the claims.
For example, in the foregoing embodiment (the first embodiment), the first current value of the motor and the second current value larger than the first current value are 6 A and 11 A, respectively. However, these current values are merely exemplary, and the present disclosure is not limited thereto. The first current value and the second current value are selectable as appropriate based on the size of the ice scraper, the characteristics of the motor, and others.
Likewise, in the foregoing embodiment (the second embodiment), the first pressure value and the second pressure value larger than the first pressure value are 0.03 MPa and 0.08 MPa, respectively. However, these pressure values are merely exemplary, and the present disclosure is not limited thereto. The first pressure value and the second pressure value are selectable as appropriate based on the size of the ice scraper, the characteristics of the pump, and others.
Moreover, in the foregoing embodiment (the first embodiment), when the current value of the motor decreases to 9 A, the thermostat, which has been forcibly turned off, is turned on again to restart the operation of the compressor. However, the current value at the time when the thermostat is turned on again is not limited thereto, and is selectable as appropriate based on the size of the ice scraper, the characteristics of the motor, and others.
Likewise, in the foregoing embodiment (the second embodiment), when the pressure difference between the pressures at the inlet and outlet of the ice-making machine decreases to 0.06 MPa, the thermostat, which has been forcibly turned off, is turned on again to restart the operation of the compressor. However, the pressure difference at the time when the thermostat is turned on again is not limited thereto, and is selectable as appropriate based on the size of the ice scraper, the characteristics of the pump, and others.
Moreover, in the foregoing embodiments, the evaporation temperature is increased stepwise in accordance with an excess of the current or the pressure difference. The evaporation temperature may alternatively be increased linearly in accordance with the excess. Also in the foregoing embodiments, the evaporation temperature is increased stepwise in accordance with an excess of the current or the pressure difference. The evaporation temperature may alternatively be increased by a preset temperature when the current or the pressure difference exceeds the first current value or the first pressure value.
Moreover, in the foregoing embodiment (the second embodiment), the pressure sensor 32 configured to detect a pressure of the seawater at the inlet of the ice-making machine 1 is disposed near the seawater inlet pipe 16. However, the pressure sensor 32 may be disposed at any location as long as it is capable of detecting a pressure of the seawater before heat exchange with the refrigerant in the evaporator E. For example, the pressure sensor 32 may be disposed at a position S1 indicated by a chain double-dashed line in
In the foregoing embodiments, the evaporator E is of a flooded type, in which most of the annular space 14 between the inner pipe 12 and the outer pipe 13 is filled with the liquid refrigerant. The evaporator E may alternatively be of a type, in which the refrigerant is jetted through a nozzle into the annular space 14 between the inner pipe 12 and the outer pipe 13.
1: ICE-MAKING MACHINE
2: COMPRESSOR
3: HEAT SOURCE-SIDE HEAT EXCHANGER
4: FOUR-WAY SWITCHING VALVE
5: UTILIZATION-SIDE EXPANSION VALVE
6: HEAT SOURCE-SIDE EXPANSION VALVE
7: SUPERHEATER
8: RECEIVER
9: SEAWATER TANK
10: PUMP
11: FAN
12: INNER PIPE
13: OUTER PIPE
14: ANNULAR SPACE
15: ICE SCRAPER
16: SEAWATER INLET PIPE
17: SEAWATER OUTLET PIPE
18: REFRIGERANT INLET PIPE
19: REFRIGERANT OUTLET PIPE
20: REFRIGERANT SUPPLY PORT
21: REFRIGERANT DISCHARGE PORT
22: SHAFT
23: SUPPORT BAR
24: BLADE
25: FLANGE
26: MOTOR
30: CONTROL APPARATUS
31: AMMETER
32: PRESSURE SENSOR
33: PRESSURE SENSOR
A: ICE-MAKING SYSTEM
E: EVAPORATOR
Number | Date | Country | Kind |
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2018-245322 | Dec 2018 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2019/033661 | 8/28/2019 | WO | 00 |