CN1113202C - Chiller systems for shops - Google Patents

Abstract

A refrigeration system for shops that operates in accordance with load capacity. It precisely minimizes temperature fluctuations within the cabinet, reduces noise and space requirements, and facilitates commissioning, maintenance, and troubleshooting. It utilizes a non-reciprocating screw compressor, housed in the machine room. Its speed is controlled by monitoring the operating suction pressure and varying the inverter frequency. It can detect faults, such as abnormally high inverter temperature, and switch to commercial power when a fault occurs. Digital displays reflect the operating status of various components, including pressure and temperature, and also indicate the cause of abnormal shutdown.

Description

Chiller systems for shops

The present invention relates to a refrigerator system for shops; more particularly, to a refrigerator suitable for connecting 5 to 7 small-capacity showcases (refrigerated cabinets) to one refrigerator system, as seen in convenience stores.

As an example, Japanese Patent Laid-Open No. 60-175970 describes a system in which an air-cooled condenser section is installed outdoors, a compressor section is installed indoors in a mechanical room, and the The capacity of the compressor is controlled by changing the rotation speed of the compressor with an inverter to suppress the reduction of its cooling capacity.

Many prior art refrigerator systems using an inverter and a reciprocating compressor with reciprocating motion suffer from the following problems.

(1). Because the torque of the compressor inherently fluctuates frequently, when it operates at low frequency, it sometimes loses inertial force to cause stalling. And when it is operated at high frequency, it sometimes causes the temperature of the discharge gas from the compressor to rise abnormally, or excessive stress acts on the discharge valve and the suction valve in the compressor. Therefore, it cannot operate fully and precisely with high accuracy over a wide range of capacities;

(2). Although the high-pressure discharge gas discharged from the compressor fluctuates greatly, the fluctuation is sometimes further amplified when the rotational speed of the compressor is changed by an inverter. Therefore, there are many restrictions in arranging the refrigerant pipes in order to prevent the sound of refrigerant gas flow inside the refrigerant pipes, and the vibration of the pipe itself; and

(3). Although the vibration and noise of the compressor itself are large, the vibration and noise are further amplified when the inverter is used to change its rotational speed. Therefore, there are many restrictions in terms of a machine room, installation in an urban residential area, operation at night, and the like.

Therefore, the object of the present invention is to solve the above-mentioned problems by providing a refrigerator system for shops, which can be equipped with a plurality of small refrigerator showcases, for example, 5 to 7 showcases, according to the large fluctuation It can operate with a large load capacity; it can achieve energy-saving effects; it can precisely control the temperature fluctuations in the cabinet to a minimum; it can reduce noise and space; and it is conducive to trial operation, maintenance and troubleshooting.

In order to achieve the above-mentioned purpose, an inventive refrigerator system for a store includes: as a most important feature, at least 3 or more refrigerators, which are installed in the store and whose internal temperature is maintained at 2 ℃; a one-person freezer installed in the backyard of the shop, the temperature inside the cabinet is maintained at about 5 ℃; a screw compressor and a drive for driving it under the control of the inverter:

A heat exchanger, which is installed on the outside of the store; a system of piping for forming a refrigerating cycle, formed by sequentially connecting refrigerated cabinets, accessible freezers, screw compressors, and outdoor heat exchangers. connected; a receiver, installed downstream of the outdoor heat exchanger of the refrigerating cycle; a liquid injection pipe, used to connect the inside or downstream of the receiver with a compression chamber of the screw compressor; a fluid control valve, installed on the liquid injection pipe to control the amount of liquid injected; a controller used to control the control valve corresponding to the discharge gas temperature of the screw compressor; and an on-off valve installed on each pipe to control the Refrigerant is directed to each refrigerator.

One end of the liquid injection pipe is preferably open so as to communicate with the compression chamber at a certain position in a wrap coming from the discharge port of the screw compressor.

Preferably, the refrigerators are 3 feet (1 yard) wide and five or more refrigerators are connected to one refrigeration cycle section.

Preferably, the driver for driving the compressor under inverter control has means for determining inverter failure and continuing operation by automatically transferring power to a commercial power source.

In addition, the driver of the screw compressor preferably has a device for controlling the rotation speed according to the suction pressure and operating the screw compressor by adjusting the rotation speed.

The refrigerator system preferably has some means for numerically displaying the operating conditions of the refrigeration system (pressure and temperature of each part, degree of superheat and rotational speed), cause of stop and cause of abnormal stop.

An inventive refrigerating machine system for stores comprising at least 3 or more refrigerated cabinets installed in the store and maintaining the temperature inside the cabinets at about 2°C; and a freezer that can be entered by a person , the temperature inside the cabinet is maintained at around 5°C. The system, as a second feature, has a screw compressor; a suction pressure probe mounted on the suction side of the screw compressor to detect the operating suction pressure; means for controlling the speed of the screw compressor by means of The frequency of the inverter is varied in accordance with the value of the suction pressure probe; a refrigerating cycle section, located outside the store, consists of an air-cooled condenser connected sequentially by pipes to the refrigerated cabinet, the man-access freezer and the A screw compressor; a receiver fitted downstream of the air-cooled condenser in the refrigerating cycle section; a liquid injection pipe for connecting the inside or downstream of the receiver with a compression chamber of the screw compressor; a A fluid control valve, installed on the liquid injection pipe, is used to control the amount of liquid injection; a discharge gas semiconductor thermometer is used to detect the temperature of the discharge gas of the screw compressor; a high-pressure detector is used to detect the pressure of the screw compressor on the discharge side ; the device used to control the opening angle of the fluid control valve according to the value of the exhaust gas semiconductor thermometer and the value of the high pressure detector; and a number of electromagnetic switching valves installed on each pipeline to guide the refrigerant to each refrigerator.

Preferably, the refrigerator has a width of about 1 meter, and five or more refrigerators are connected to the refrigeration cycle section.

Preferably, the refrigerating machine system further includes a means for determining a failure of the inverter, and when it is determined that the inverter has failed by the means for determining the failure, for automatically switching the power supply of the screw compressor to Connect to a commercial power source for continued operation.

It is more preferable that the refrigerator system has a device which digitally displays the pressure and temperature in each part and the rotation speed of the screw compressor representing at least the operating conditions; device.

According to the invention as described above, the following operations are provided:

(1) Since the torque fluctuation is not large due to the use of the screw compressor in the refrigerator system, the screw compressor will not stall even if it is operated at a low frequency, and there will be no problem even if it is operated at a high frequency. Therefore, it can stably control its capacity over a wide range. In addition, it is capable of finely operating with high precision for a capacity with a wide fluctuation range by detecting the operating suction pressure and changing the frequency of the inverter to control the rotational speed of the screw compressor. In addition, since the compressor whose torque does not fluctuate much originally is installed in the dedicated machine room, and the rotation speed is changed by the inverter, the vibration and noise of the entire refrigerator system can be reduced. Also, since the pulsation of the high-pressure gas discharged from the compressor is small, the flow sound of the refrigerant gas generated in the refrigerant piping and the vibration of the piping itself can be reduced, thereby reducing restrictions on the layout of the refrigerant piping . In addition, because the amount of liquid injected into the compression chamber of the compressor is controlled by the detection of the temperature and pressure of the discharged gas, and the injection of the refrigerant is at the compression chamber communicating with the discharge port of the screw compressor, it is possible to maintain refrigerating capacity while obtaining a stable discharge gas temperature without reducing the intake of refrigerant gas from the suction side of the compressor and without overheating up to higher frequencies;

(2) Because the refrigerating machine system is equipped with a device for detecting the failure of the inverter, and a device for continuing operation, by connecting the power supply of the screw compressor to the commercial power supply when it is determined by the measuring device that the inverter has failed , and when the converter fails, the power supply is automatically connected to the commercial power supply, so although the temperature cannot be continuously controlled, the required minimum refrigeration operation can be maintained, thereby avoiding adverse effects on the products stored in the showcase Impact;

(3) Since an operation mode in which the frequency is fixed is provided in the driver of the screw compressor, compared with the operation mode in which the operation frequency varies with the normal suction pressure, some maintenance can be easily performed, such as in During the test run, adjust the expansion valve, and charge the refrigerant, etc.

(4) Since the operation status is displayed, by periodically checking the refrigerator system in advance, failure can be prevented. In addition, since the cause of the abnormal stop or the like is displayed, it is easy to perform maintenance of the refrigerator system, such as confirming whether the operating range is appropriate or not.

The nature of the invention, as well as other objects, applications and advantages thereof, will become apparent from the following description and accompanying drawings.

Figure 1 is a top view illustrating the overall configuration according to an embodiment of a refrigerator system invented for store applications;

Figure 2 is a side view illustrating the overall configuration according to one embodiment of the present invention;

FIG. 3 is a block diagram illustrating a partial structure of a refrigeration cycle according to an embodiment of the present invention;

FIG. 4 is a flow chart illustrating an outline of the operation for controlling the suction pressure of the refrigeration cycle portion according to one embodiment of the present invention;

5 is a block diagram illustrating a method of continuing operation when a converter fails, according to an embodiment of the present invention;

Figure 6 is a side view illustrating peripheral equipment for a screw compressor in accordance with one embodiment of the present invention;

Figure 7 is a front view illustrating details of a display panel according to one embodiment of the present invention;

Fig. 8 is a sectional view illustrating the joint state of the helical cladding in the screw compressor, and the relationship between the helical cladding and the position of the aperture for injecting liquid refrigerant.

Some concepts of the invention can be summarized as follows.

(1) A screw compressor without reciprocating motion is used. Its driving method is to control its rotational speed by detecting the operating suction pressure and changing the converter frequency. It is installed in a special mechanical room.

(2) Control the liquid injection volume according to the temperature and pressure value of the gas discharged from the screw compressor. Liquid refrigerant is injected into the compression chambers near a discharge port, communicating with each other once during a rotary motion of the rotating helical envelope of the screw compressor.

(3) The inventive refrigerant system can discriminate a malfunction, such as an abnormal rise in inverter temperature, and can connect the power supply of the screw compressor to a commercial power supply when such a malfunction occurs.

(4) providing a mode of operating the compressor at a fixed speed; and

(5) At least the pressure and temperature of each part and the rotational speed of the screw compressor are displayed numerically as the operation status, and besides that, the reason why the operation stops and the reason of the abnormal stop are also displayed.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a top view of the entire configuration of a refrigerating machine system of the present invention for stores, Fig. 2 is a side view thereof, and Fig. 3 is a block diagram illustrating the structure of a refrigerating cycle part from the control relationship.

The goods are stored in six refrigerated cabinets 2, which are installed in the store 1 and have a width of about 1 meter. The temperature in the cabinet is maintained at about 2°C.

In the backyard of the store, there is a freezer 3 that can be entered by a person, people can walk into it, and commodities can be stored therein, and the temperature in the cabinet is maintained at about ℃. It should be pointed out that from the perspective of efficiency, at least 3 or more refrigerators 2 need to be connected, and the refrigerator system needs to be operated for more than 2/3 of the day, so that during this time (for example, 7A. M to 23P.M) for sales activities. A screw refrigerator 100 equipped with a screw compressor 10 and a driver 200 for driving the compressor under inverter control are installed in a machine room 4 adjacent to the shop. An air-cooled condenser 20 is provided outside the store. It is attempted to reduce noise emitted to the outside and facilitate maintenance by installing a screw compressor 10 whose torque does not fluctuate much in the machine room 4 . The refrigeration cycle section includes a refrigerator 2, an accessible freezer 3, an accumulator 60, a screw compressor 10, an air-cooled condenser 20, and a receiver 30 installed downstream of the air-cooled condenser 20 , they are sequentially connected to each other. The interior or downstream of the receiver 30 is connected via a liquid injector 85 to a compression chamber (not shown) of the screw compressor 10 . A fluid control valve 80 for controlling the amount of liquid injected into the screw compressor 10 is mounted on the liquid injection pipe 85, and a solenoid-operated valve 70, which is closed when the screw compressor 10 is stopped or when the power supply is cut off. .

In the refrigerating machine system and refrigerating cycle section arranged as described above, the low-temperature pressure refrigerant gas evaporated in the refrigerated cabinet 2 and the accessible freezer 3 flows through the accumulator installed in the machine room 4 60, and is compressed by the screw compressor 10 into high-pressure refrigerant gas. Since the high-pressure gas discharged from the screw compressor 10 has little pulsation at this time, it is possible to reduce the flow sound of the refrigerant gas generated in the piping, and the vibration of the piping itself. Thereafter, the refrigerant gas is condensed into refrigerant liquid by the air-cooled condenser 20 installed outside the store, and it is temporarily stored in the receiver 30. Then, through the refrigerant liquid pipeline 33 and the expansion valve 36 flowing through the electromagnetic switching valve 35, the refrigerant liquid is supplied to the refrigerator 2 as the evaporator and the freezer 3 that people can enter, thereby forming a circulation system, and Generate cold air.

Next, referring to the flowchart shown in Fig. 4, the outline of the operation for controlling the suction pressure of the refrigerating cycle portion in Fig. 3 will be described. When the capacity of the compressor is constant and when the load required by the evaporator becomes larger, that is, when the temperature of the refrigerator 2 and the walk-in freezer 3 rises, the suction pressure during compressor operation increases. And when they are overcooled, and the load becomes smaller, the suction pressure becomes lower. Therefore, it is possible to perform a capacity-controlled operation by which the cooling capacity of the refrigerator can be changed in accordance with the load by changing the rotational speed of the compressor by detecting the suction pressure.

In step 401 , the operating suction pressure detected by a suction pressure detector 91 is input into a controller 201 . Here, it is compared with a preset pressure value (Psb) set in advance, and in step 403, it has a range of allowable preset pressure difference (ΔPs). When it is larger than them, that is, when it is in the (A) region of the range, an operation frequency command is output to the inverter 202 so that the operation frequency is increased in step 405 . It should be noted that in steps 404 and 406, the upper limit of the frequency is set to 80 Hz. Then, the inverter 202 generates a power supply having a frequency instructed by the controller 201, and supplies it to the screw compressor 10 to control it so as to increase the rotational speed.

And when it is less than the preset pressure value (Psb), that is, when it is in the (C) zone, on the contrary, the operating frequency is reduced in step 409 . It should be noted that in steps 408 and 406 the lower frequency limit is set at 20 Hz. When the operating suction pressure is within the allowable range, that is, in zone (B), the frequency at this time is maintained in step 406 . The pre-set preset pressure value (Psb) and preset pressure difference (ΔPs) are changed automatically by detecting the temperature inside the store equipped with refrigerated cabinet 2 and accessible freezer 3, and equipped with air cooling The temperature outside the store of the type condenser 20 is used to achieve stable and efficient operation throughout the year with environmental changes.

Next, the control of the discharge gas temperature in the refrigerating cycle section in Fig. 3 will be described. Since the refrigerator with screw compressor 10 contains oil on the discharge side, it must be superheated to a certain extent to maintain the viscosity of the oil. If the discharge pressure is constant, only the temperature of the discharge gas needs to be controlled. However, because the discharge pressure varies with operating suction pressure, operating frequency and outside air temperature, it must be kept as low as possible without overheating too much. Then, the controller 201 calculates the degree of superheating of the refrigerant depending on a relationship between the exhaust gas temperature detected by the exhaust gas semiconductor thermometer (temperature detector) and the pressure detected by the high pressure detector 92 . The opening angle of the fluid control valve 80 is changed corresponding to the degree of superheat to control the amount of liquid refrigerant injected into the screw compressor 10 (liquid injection amount). When the refrigerant is superheated too much, the temperature of the exhaust gas is lowered by increasing the liquid injection amount, and is controlled to an appropriate temperature without lowering its refrigerating capacity. It can use chlorofluorocarbons 22 in addition to specific chlorofluorocarbons without having to use specific chlorofluorocarbons.

Fig. 8 is a positional view of the spiral cladding hole for injecting liquid refrigerant in the screw compressor 10, in which a hole 141a for injecting liquid refrigerant is installed on a mirror 115, which is installed The position is within the first turn (within 2π in terms of incline angle) from the start of the winding of the fixed helical cladding 110, near an outer periphery of the fixed helical cladding 110. Another hole 141b for injecting liquid cryogen is also provided on the mirror surface, its position is near an inner periphery of the fixed helical cladding 110, ie advanced 2π from the hole 141a. Liquid refrigerant is injected into the cavity 121a and the bore 121b by providing the holes at the above positions, and the bores communicate with one discharge hole 102 once during one circular motion of the spiral track member 111. It avoids excessive liquid compression of the refrigerant, thereby avoiding a decrease in refrigeration capacity.

In addition, it has been possible to prevent moisture compression or alarm generation by, according to a relationship between the suction gas temperature detected by the suction gas semiconductor thermometer 93 and the operating suction detected in the same way, for the temperature determined by this relationship. The degree of superheat of the suction gas is calculated.

Although when the type of refrigerant is determined, the degree of superheating of the discharge side and the suction side can be determined from the pressure and temperature as described above, but if the type of refrigerant is different, even at the same temperature and pressure, The degree of overheating also varies. For this reason, the inherent values of several kinds of refrigerants are input in advance into the controller 201 so that the values can be selected by a setting device such as an external switch, thereby even when the types of refrigerants are different, Ability to calculate the correct degree of superheat. Therefore, even when the types of refrigerants are different, the degree of superheating can be accurately controlled.

Referring now to Fig. 5, a method for continuing operation even when the converter is faulty is described.

When the inverter 202 is normal, the electromagnetic contactors 203 and 204 are turned on, and power is supplied to a motor for the screw compressor 10, thereby controlling it. It can be seen that when the converter 202 itself sends an abnormal signal to the controller 201, for example, when the temperature of the converter 202 rises abnormally, or when the controller 201 sends an operation command to the converter 202, but the converter 202 A fault occurs in converter 202 when a current detector on the secondary side fails to detect current. Subsequently, the electromagnetic contactors 203 and 204 are turned off, and the electromagnetic contactor 205 is turned on, so that the commercial power is directly supplied to the motor of the screw compressor 10 . As a result, although the operation cannot be controlled, at least the operation can be maintained.

Fig. 6 illustrates the peripheral equipment of the screw compressor 10 in the compressor system 100, which is equipped with a digital display panel 207 on an electrical equipment box (driver) 200, and a controller 201, a converter 202, and an electromagnetic contactor are housed in the box 203, 204 and 205, and current detector 206.

Figure 7 shows the details of the digital display panel 207, in which codes 208 and data 209 are provided as digital display items; selection keys 210 are also provided for selecting display items. By manipulating the selection key 210, the operating conditions are digitally displayed by the data 209 (preset pressure, each pressure value of discharge pressure and suction pressure, each temperature value of discharge gas temperature, suction gas temperature, store temperature and outdoor temperature, discharge gas refrigeration Each superheat value of refrigerant and suction gas refrigerant, operating frequency value, and operating current value, etc.). When a certain abnormal condition occurs, the abnormal lamp 211 lights up. The display can show a code stating the reason for the stop and, when it is abnormally stopped, has the function of maintaining the operation condition, so as to allow to determine which protection device has been operated when the operation condition is stopped under the operation of the protection device .

As described above, even when a plurality of small refrigerated showcases are installed, and when some connected showcases and storage temperatures vary greatly, for example, due to store remodeling or changes in displayed merchandise, the present invention The refrigerator system can also be operated in accordance with the load capacity. It also saves energy because the suction pressure is always constant throughout the year while the chiller is running. In addition, it can continuously control the temperature fluctuation in the presentation cabinet to a minimum, so the storage temperature in the presentation cabinet is stable, and the stored goods can be kept fresh. Moreover, it can achieve noise reduction and space reduction because the screw compressor whose torque does not fluctuate much inherently is installed in the machine room. It is also useful for commissioning, performing maintenance, troubleshooting, and displaying operating conditions.

Although a preferred embodiment of the invention has been described, a person skilled in the art can make changes within the scope of the inventive concept described in the following claims.

Claims (4)

1. A refrigerating machine system for a store, comprising at least 3 or more refrigerated cabinets, which are installed in the store, and the temperature inside the cabinets is maintained at about 2°C, and includes a freezer that can be entered by one person , the temperature inside the cabinet is kept at around 5°C; The refrigerator system for a store also includes: a screw compressor; a suction pressure detector installed on the suction side of the screw compressor for detecting the operating suction pressure; means for controlling the rotational speed of said screw compressor by varying the frequency of the inverter in accordance with said suction pressure detection; a refrigerating cycle section, installed outside the store, comprising an air-cooled condenser connected in sequence by a pipe to said refrigerated cabinet, said man-access freezer and said screw compressor; a receiver positioned downstream of said air-cooled condenser of said refrigeration cycle section; a liquid injection pipe for connecting the inside or downstream of said receiver with the compression space of said screw compressor; A flow control valve, installed on the liquid injection tube, is used to control the liquid injection volume; A semiconductor thermometer for exhaust gas, used to detect the temperature of the exhaust gas from the screw compressor; a high pressure detector for detecting the pressure of said screw compressor on the discharge side; means for controlling the opening angle of the flow control valve according to the values of the exhaust gas semiconductor thermometer and the high pressure detector; and Some electromagnetic switching valves are installed on each pipeline to guide the refrigerant into each refrigerator. 2. The refrigerator system for stores according to claim 1, wherein the refrigerator has a width of about 1 meter, and 5 or more refrigerators are connected to the refrigeration cycle section. 3. The refrigerator system for shops according to claim 1, further comprising means for determining failure of said inverter and for continuing operation when said means for determining failure determines said The power supply to the screw compressor is automatically switched to a commercial power supply when the converter has experienced a failure. 4. The refrigerating machine system for stores according to claim 1, having means for displaying at least the temperature and pressure of each part as operating conditions and the rotational speed of said screw compressor in numbers, and having a display stop cause and the cause of the abnormal stop.

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