JP2007170803A - Refrigeration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that in a refrigerant circuit having a compressor, a condenser, a decompression device, and an evaporator annularly connected by piping in an air conditioner for air-conditioning a low temperature show case installed in a store such as a convenience store or for air-conditioning a store, the COP (Coefficient of Performance) is better when the high pressure side pressure of the compressor is low, but because the condensation pressure when the outside air temperature is low becomes remarkably low and the pressure difference between the high pressure side and the low pressure side becomes small, a refrigerant does not flow even when an expansion valve operates. <P>SOLUTION: In the refrigerating cycle device having the refrigerant circuit, when the outside temperature is low, capacity of the compressor and/or condensation capacity of the condenser is controlled so that the pressure difference between the low pressure side pressure and the high pressure side pressure of the compressor is a set value or within a set range. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle constituted by a refrigerant circuit in which a compressor, a condenser, a decompression device, and an evaporator are connected in a ring shape, and particularly relates to operation control at a low outside air temperature.

Conventionally, a low temperature showcase installed in a store such as a convenience store or an air conditioner for air conditioning in a store includes a refrigerant circuit in which a compressor, a condenser, a decompression device, and an evaporator are connected in a ring shape. (See Patent Document 1).
JP-A-4-24446

  In the refrigerant circuit as described above, the high pressure side pressure of the compressor is lowered and the coefficient of performance (COP) is improved at a low outside air temperature, but the condensing pressure is significantly reduced, so the pressure difference between the high pressure side pressure and the low pressure side pressure. Will become smaller. In such a state, since the pressure on the upstream side (condenser side) of the decompression device also decreases significantly, the refrigerant does not flow into the evaporator when the decompression device is opened, and the showcase and the like are cooled. There was a problem that could not.

  The present invention has been made to solve the conventional problems, and is intended to maintain a good coefficient of performance at a low outside air temperature and to secure a predetermined pressure difference before and after the decompression device. Providing a cycle.

  The invention according to claim 1 is a refrigeration system in which a compressor, a condenser, a decompression device, and an evaporator whose capacity can be controlled are connected by piping, wherein the condenser is a condenser capable of controlling a condensation capacity, and the compressor Pressure sensors provided on the low pressure side and the high pressure side, and a temperature sensor for measuring the temperature around the condenser, and when the outside air temperature detected by the temperature sensor is higher than a predetermined value, the low pressure side pressure The discharge capacity of the compressor and the condensing capacity of the condenser are controlled according to the low pressure side pressure detected by the sensor. When the outside air temperature is lower than a predetermined value, the low pressure side pressure sensor and the high pressure side pressure sensor The discharge capacity of the compressor and the condensation capacity of the condenser are controlled according to the detected pressure difference between the low pressure side pressure and the high pressure side pressure.

  According to a second aspect of the present invention, in the refrigeration system according to the first aspect, when the outside air temperature is lower than a predetermined value and the pressure difference falls below a lower limit value of a set range, the discharge capacity of the compressor is increased. At the same time, the condensation capacity of the condenser is reduced.

  According to the present invention, in a refrigeration system in which a compressor, a condenser, a decompression device, and an evaporator capable of capacity control are connected by piping, the condenser is a condenser capable of controlling a condensation capacity, and the outside air temperature is predetermined. When the air temperature is higher than the value, the condensing capacity of the condenser is controlled according to the low-pressure side pressure of the compressor and the discharge capacity of the compressor is controlled. When the outside air temperature is lower than the predetermined value, the low pressure of the compressor The condensation capacity of the condenser is controlled according to the pressure difference between the side pressure and the high pressure side pressure, and the discharge capacity of the compressor is controlled. In particular, when the outside air temperature is lower than a predetermined value and the pressure difference falls below the lower limit value of the setting range, the condensation capacity of the condenser is reduced to prevent the condensation pressure from being excessively lowered, and the compressor discharge By increasing the capacity, the discharge pressure can be increased, and the pressure difference before and after the pressure reducing device can be set within a set range. When the pressure reducing device is activated, the refrigerant is appropriately decompressed by this pressure difference and flows into the evaporator, so that cooling is possible even at a low outside temperature. Furthermore, by setting the pressure difference within a set range, it is possible to prevent a COP from being lowered due to an increase in the high-pressure side pressure of the compressor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, a portion surrounded by a broken line represents an indoor unit such as a low-temperature showcase or an air conditioner provided with a decompression device and an evaporator. Moreover, although the refrigerant | coolant used in each Example assumes the HFC type | system | group refrigerant | coolant, it is not restricted to this, A natural refrigerant | coolant, such as HC type | system | group refrigerant | coolant and a carbon dioxide, has the same effect.

  FIG. 1 is a refrigerant circuit of a refrigeration cycle to which the present invention is applied. In FIG. 1, 1 is a compressor capable of inverter control (compressor capable of capacity control), 2 is a condenser, 3 is an expansion valve (decompression device), and 4 is an evaporator. The circuit is configured.

  Further, 11 is a controller for controlling the capacity of the compressor 1, 12 is a condenser temperature sensor, 13 is an outside air temperature sensor, 14 is a high pressure side pressure sensor, and 15 is a low pressure side pressure sensor. The signal is input to the controller 11. The controller 11 controls the capacity of the compressor 1 according to the input signal.

  When the compressor 1 is started with the above configuration, the high-temperature and high-pressure gas refrigerant compressed by the compressor 1 is discharged from the compressor 1 and enters the condenser 2 to be cooled. The cooled refrigerant is in a gas-liquid mixed state and flows into the evaporator 4 via the expansion valve 3. The refrigerant is decompressed by being throttled in the expansion valve 3, and is cooled by being evaporated in the evaporator 4. The low-temperature and low-pressure gas refrigerant evaporated in the evaporator 4 is again sucked into the compressor 1 to constitute a refrigeration cycle.

  In this embodiment, the expansion valve 3 uses a thermo valve whose opening degree is changed by a temperature sensing cylinder that detects the outlet temperature of the evaporator 4, but electronically corresponding to the outlet temperature of the evaporator 4. An electronic expansion valve whose opening degree is controlled may be used.

  Based on the output from the outside air temperature sensor 13, the controller 11 controls the capacity of the compressor 1 based on the input from the low pressure side pressure sensor 15 at room temperature such as 0 ° C. or more. Therefore, when the evaporator 4 is sufficiently cooled, the expansion valve 3 is closed, so that the low-pressure side pressure decreases and the high-pressure side pressure increases.

  Since the COP of the refrigeration cycle apparatus decreases due to the increase in the high pressure side pressure, when the low pressure side pressure sensor 15 detects a decrease in the low pressure side pressure, the controller 11 reduces the capacity of the compressor 1 and performs energy saving operation. Do.

  Further, when the temperature of the showcase or the like rises and the evaporator 4 starts a cooling operation, the expansion valve 3 opens, so that the low pressure side pressure rises and the high pressure side pressure falls. If this situation continues, it becomes difficult for the refrigerant to flow due to a decrease in the cooling capacity of the refrigeration cycle apparatus due to a shortage of refrigerant and a decrease in pressure difference.

  Therefore, when the low pressure side pressure sensor 15 detects an increase in the low pressure side pressure, the controller 11 increases the capacity of the compressor 1 and increases the high pressure side pressure to increase the pressure difference.

  On the other hand, when the outside air temperature is low, such as 0 ° C. or less, the controller 11 controls the compressor 1 based on the pressure difference between the outputs of the low pressure side pressure sensor 15 and the high pressure side pressure sensor 14.

  When the pressure difference is smaller than the lower limit value represented by the set value −α, the refrigerant becomes difficult to flow. Therefore, the controller 11 maintains the pressure difference by increasing the capacity of the compressor 1 and increasing the high-pressure side pressure. To do.

  By making the pressure difference equal to or greater than the set value −α (the lower limit of the set range) by the above control, the refrigerant is appropriately decompressed when the expansion valve 3 is operated, and cooling is performed in the showcase or the like. Can do.

  Further, when the pressure difference is larger than the upper limit value represented by the set value + α, the COP of the compressor 1 is reduced due to the increase of the high-pressure side pressure. Suppress the rise. When the pressure difference is not less than the lower limit and not more than the upper limit, the capacity control of the compressor 1 is not performed.

  FIG. 2 is a refrigerant circuit of a refrigeration cycle to which the present invention is applied. In this figure, 5-a and 5-b are compressors, 2 is a condenser, 3 is an expansion valve, and 4 is an evaporator, which constitute a refrigerant circuit of the refrigeration cycle apparatus.

  11 is a controller for controlling the operation of the compressors 5-a and 5-b, 12 is a condenser temperature sensor, 13 is an outside air temperature sensor, 14 is a high-pressure sensor, and 15 is a low-pressure sensor. Yes, signals from each sensor are input to the controller 11. The controller 11 controls the operation of the compressors 5-a and 5-b according to the input signal.

  When the compressor 5-a or 5-b is started with the above configuration, the high-temperature and high-pressure gas refrigerant compressed by the compressor 5-a or 5-b is discharged from the compressor 5-a or 5-b. And enters the condenser 2 to be cooled. The cooled refrigerant is in a gas-liquid mixed state and flows into the evaporator 4 via the expansion valve 3. The refrigerant is decompressed by being throttled in the expansion valve 3, and is cooled by being evaporated in the evaporator 4. The low-temperature and low-pressure gas refrigerant evaporated in the evaporator 4 is again sucked into the compressor 5-a or 5-b to constitute a refrigeration cycle.

  In this embodiment, the expansion valve 3 uses a thermo valve whose opening degree is changed by a temperature sensing cylinder that detects the outlet temperature of the evaporator 4, but electronically corresponding to the outlet temperature of the evaporator 4. An electronic expansion valve whose opening degree is controlled may be used.

The controller 11 controls the operation and stop of the compressors 5-a and 5-b based on the input from the low-pressure side pressure sensor 15 based on the input from the outside air temperature sensor 13 based on the input from the low-pressure sensor 15 at a normal temperature such as 0 ° C. or more. . When the evaporator 4 is sufficiently cooled, the expansion valve 3 is closed, so that the low-pressure side pressure decreases and the high-pressure side pressure increases. The increase in the high-pressure side pressure causes the COP of the refrigeration cycle apparatus to decrease.

  Therefore, when the low-pressure side pressure sensor 15 detects a decrease in the low-pressure side pressure, the controller 11 stops the compressor 5-b when, for example, both the compressor 5-a and the compressor 5-b are operating. By operating only the compressor 5-a, the capacity of the compressor of the refrigeration cycle apparatus is reduced, and energy saving operation is performed.

  Further, when the temperature of the showcase or the like rises and the evaporator 4 starts a cooling operation, the expansion valve 3 opens, so the low pressure side pressure rises and the high pressure side pressure falls. If this situation continues, it becomes difficult for the refrigerant to flow due to a decrease in the cooling capacity of the refrigeration cycle apparatus due to a shortage of refrigerant and a decrease in pressure difference.

  Therefore, when the low-pressure side pressure sensor 15 detects a decrease in the low-pressure side pressure, the controller 11 operates both the compressor 5-a and the compressor 5-b, for example, to increase the high-pressure side pressure of the compressor. To increase the pressure difference.

  On the other hand, when the outside air temperature is low such as 0 ° C. or less, the controller 11 controls the compressors 5-a and 5-b based on the pressure difference due to the outputs of the low pressure sensor 15 and the high pressure sensor 14. Do.

  If the pressure difference is smaller than the lower limit value represented by the set value −α, it becomes difficult for the refrigerant to flow. For example, when the controller 11 is operating only the compressor 5-a, the compressors 5-a and 5- The pressure difference is maintained by operating both b and increasing the high-pressure side pressure.

  By setting the pressure difference to be equal to or larger than the set value −α by the above control, the refrigerant is appropriately decompressed when the expansion valve 3 is operated, and cooling can be performed in the showcase or the like.

  When the pressure difference is larger than the upper limit value represented by the set value + α, the COPs of the compressors 5-a and 5-b are reduced due to the increase in the high-pressure side pressure. Therefore, in such a state, for example, when both the compressors 5-a and 5-b are operating, the controller 11 stops the compressor 5-a and suppresses the increase in the high-pressure side pressure. When the pressure difference is not less than the lower limit and not more than the upper limit, the compressors 5-a and 5-b are not controlled.

  FIG. 3 is a refrigerant circuit of a refrigeration cycle to which the present invention is applied. In this figure, 6 is a compressor, 2 is a condenser, 3 is an expansion valve, 4 is an evaporator, and these constitute a refrigerant circuit of the refrigeration cycle apparatus. 21 is a condenser blower for air-cooling the condenser 2, and is driven by a motor 22. The condenser 2 can change the condensing capacity depending on the rotational speed of the motor 22.

  11 is a controller for controlling the rotation speed of the motor 22 of the condenser blower 21, 12 is a condenser temperature sensor, 13 is an outside air temperature sensor, 14 is a high pressure side pressure sensor, and 15 is a low pressure side pressure sensor, Signals from each sensor are input to the controller 11. The controller 11 controls the rotation speed of the motor 22 of the condenser blower 21 based on the input signal.

When the compressor 6 is started with the above configuration, the high-temperature and high-pressure gas refrigerant compressed by the compressor 6 is discharged from the compressor 6 and enters the condenser 2 to be cooled. At this time, the condensing capacity of the condenser 2 varies depending on the rotational speed of the motor 22 of the condenser blower 21.

  The cooled refrigerant is in a gas-liquid mixed state and flows into the evaporator 4 via the expansion valve 3. The refrigerant is decompressed by being throttled in the expansion valve 3, and is cooled by being evaporated in the evaporator 4. The low-temperature gas refrigerant evaporated in the evaporator 4 is again sucked into the compressor 6 to constitute a refrigeration cycle.

  In this embodiment, the expansion valve 3 uses a thermo valve whose opening degree is changed by a temperature sensing cylinder that detects the outlet temperature of the evaporator 4, but electronically corresponding to the outlet temperature of the evaporator 4. An electronic expansion valve whose opening degree is controlled may be used.

  The controller 11 controls the rotational speed of the motor 22 based on the input from the temperature sensor 12 of the condenser 2 based on the input from the outside air temperature sensor 13 at a normal temperature such as 0 ° C. or more. For example, when the temperature of the refrigerant flowing into the condenser 2 is high, the rotational speed of the motor 22 is increased to promote heat dissipation. Conversely, when the temperature of the refrigerant flowing into the condenser 2 is low and there is no need for heat dissipation, the motor 22 Reduce the number of revolutions to save energy.

  Further, when the temperature of the showcase or the like rises and the evaporator 4 starts a cooling operation, the expansion valve 3 opens, so that the low pressure side pressure rises and the high pressure side pressure falls. If this situation continues, the cooling capacity of the refrigeration cycle apparatus decreases due to a shortage of refrigerant, so the controller 11 increases the cooling capacity by increasing the number of revolutions of the motor 22 and lowering the temperature of the refrigerant flowing into the evaporator 4.

  On the other hand, when the outside air temperature is low such that the outside air temperature is lower than 0 ° C., the controller 11 controls the motor 22 of the condenser blower 21 based on the pressure difference between the outputs of the low pressure side pressure sensor 15 and the high pressure side pressure sensor 14. If the pressure difference is smaller than the lower limit value represented by the set value −α, it becomes difficult for the refrigerant to flow. Therefore, the controller 11 maintains the pressure difference by reducing the rotation speed of the motor 22 and suppressing the decrease in the condensation pressure.

  When the pressure difference is larger than the upper limit value represented by the set value + α, the controller 11 increases the rotation speed of the motor 22 to condense because the COP of the compressor 6 decreases due to the increase of the high-pressure side pressure. Reduce pressure. In addition, when the said pressure difference is more than a lower limit and below an upper limit, control of the rotation speed of the motor 22 is not performed.

  By the above control, the COP of the refrigeration cycle apparatus can be improved by suppressing an excessive increase in the high-pressure side pressure at a high outside air temperature. Further, by setting the pressure difference within a set value ± α (set range) at a low outside air temperature, the refrigerant is appropriately decompressed and cooled when the expansion valve 3 is operated. Furthermore, COP of the refrigeration cycle apparatus can be improved by performing control so that the pressure difference does not become too large even at low outside air temperatures.

  In the embodiment, the control method by the controller 11 is switched depending on the outside air temperature. However, the operation control may be performed so that the pressure difference between the high pressure side pressure and the low pressure side pressure of the compressor is always within the set value or the set range. Good. In the second embodiment, the number of compressors is two, but the number is not limited.

  In the third embodiment, the rotational speed of the motor 22 of the blower is used as a capacity control method of the condenser 2. However, the present invention is not limited to this, and the method of changing the surface area of the condenser or changing the number of condensers to be used. Etc.

  In addition, when performing control of Example 1, Example 2, and Example 3, in any case, the malfunction of the expansion valve 3 is prevented by setting the set value or the set range to 0.45 MPa or more. Confirm that you can.

It is a refrigerant circuit figure of the refrigerating system to which this invention is applied (Example 1). (Example 2) which is the refrigerant circuit figure of the refrigerating system to which this invention is applied. (Example 3) which is a refrigerant circuit figure of the refrigerating system to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter-controllable compressor 2 Condenser 3 Expansion valve 4 Evaporator 5-a, 5-b, 6 Compressor 11 Controller 12 Condenser temperature sensor 13 Outside temperature sensor 14 Compressor high pressure side sensor 15 Compressor low pressure side sensor 21 Condenser cooling fan 22 Condenser cooling fan motor

Claims (2)

In a refrigeration system in which a capacity-controllable compressor, condenser, decompressor and evaporator are connected by piping,
The condenser is a condenser capable of controlling the condensation capacity,
Pressure sensors provided on the low pressure side and the high pressure side of the compressor;
A temperature sensor for measuring the ambient temperature of the condenser;
When the outside air temperature detected by the temperature sensor is higher than a predetermined value, the discharge capacity of the compressor and the condensation capacity of the condenser are controlled according to the low pressure side pressure detected by the low pressure side pressure sensor,
When the outside air temperature is lower than a predetermined value, the discharge capacity of the compressor and the condensation of the condenser according to the pressure difference between the low pressure side pressure and the high pressure side pressure detected by the low pressure side pressure sensor and the high pressure side pressure sensor. A refrigeration system characterized by controlling capacity.
The outside air temperature is lower than a predetermined value,
When the pressure difference falls below the lower limit of the setting range,
The refrigeration system according to claim 1, wherein the discharge capacity of the compressor is increased and the condensing capacity of the condenser is decreased.