JP2010169286A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform an operation of high efficiency capable of securing a necessary oil supply amount to a compressor, increasing a refrigerating capacity and reducing power consumption. <P>SOLUTION: This refrigerating device is constituted of a refrigerating cycle is configured by successively connecting the compressor 1, an oil separator 2 for separating refrigerating machine oil from a refrigerant discharged from the compressor, an air cooling-type condenser 3 having an air distribution fan 14, a pressure reducing device 5 and an evaporator 6. In the refrigerating device which supplies oil to the compressor 1, the refrigerating machine oil separated by the oil separator 2 is supplied to the compressor 1 by utilizing a pressure difference between pressure at a high pressure side and pressure at a low pressure side generated by the compressing action of the compressor 1, pressure detecting means 15, 16 are disposed to detect the pressure of a sucking section and a discharging section of the compressor 1, the target discharge pressure of the compressor corresponding to the minimum necessary oil supply amount of the compressor 1 is determined according to the detected pressure of the sucking section, and a rotation speed of the air distribution fan is controlled so that the detected pressure of the discharging section reaches the target discharge pressure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus, and more particularly, to a refrigeration apparatus including a differential pressure oil supply type compressor that supplies oil using a pressure difference between a high pressure side pressure and a low pressure side pressure generated by a compression action of a compressor.

  In the refrigeration apparatus, a refrigeration cycle is used in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected by refrigerant piping. In this refrigeration cycle, the low-pressure refrigerant sucked into the compressor is compressed to a predetermined high-pressure, led to a condenser, and exchanges heat with air to become a high-pressure liquid refrigerant. The high-pressure liquid refrigerant is led to the expansion valve and expanded, and then sent to the evaporator to exchange heat with a fluid to be cooled such as air or water to be cooled to become a low-pressure gas refrigerant. The low-pressure gas refrigerant is sucked into the compressor and compressed again, and circulates in the above-described refrigeration cycle.

  In such a refrigeration apparatus, the refrigerant discharged from the compressor is led to an oil separator provided on the upstream side of the condenser to separate the refrigeration oil from the refrigerant, and the pressure of the separated refrigeration oil and the compressor A differential pressure lubrication system is used in which refrigeration oil is supplied to a bearing portion of a compressor by utilizing a differential pressure with respect to the pressure of the suction portion (hereinafter referred to as suction pressure). Here, the pressure of the refrigerating machine oil to be supplied is slightly lower (for example, about 0.05 MPa) than the pressure of the discharge part of the compressor (hereinafter referred to as discharge pressure). For example, in the case of a two-stage compressor that compresses refrigerant in two stages, the pressure of the refrigerating machine oil separated from the refrigerant discharged from the second-stage compressor, the first-stage compressor, and the second-stage compressor Refrigeration oil is supplied to the intermediate part of the compressor by utilizing the differential pressure with the intermediate pressure.

  By the way, in such a differential pressure oil supply system, if the discharge pressure is too low, the pressure of the separated refrigeration oil also decreases, so the difference between the pressure of the refrigeration oil and the suction pressure or the pressure of the refrigeration oil and the intermediate pressure is It may decrease and may not satisfy the minimum amount of oil required for the compressor (hereinafter referred to as the minimum required amount of oil). If the minimum required amount of oil cannot be supplied to the compressor, there is a risk of damaging the rotor surface of the compressor, bearings, etc. and reducing the life of the compressor.

  On the other hand, when pressure sensors are installed on the discharge side and suction side of the compressor, respectively, and the differential pressure between the discharge pressure and the suction pressure is close to or less than the lower limit of the pressure difference that can be refueled A technique for controlling to reduce or stop the rotation speed of a blower fan for a condenser is disclosed (see Patent Document 1). According to this, since the refrigerant pressure in the condenser rises, that is, the discharge pressure rises, the differential pressure becomes large and a sufficient oil supply amount can be secured, and the lack of oil supply in the compressor can be solved. it can.

JP-A-8-28971

  However, according to the above-mentioned Patent Document 1, consideration is given to ensuring the minimum required oil supply amount of the compressor, but consideration is not given to improving the operation efficiency of the compressor, and further improvements are made. There is room for.

  That is, in Patent Document 1, the differential pressure between the discharge pressure and the suction pressure of the compressor is maintained to be equal to or higher than the lower limit value of the differential pressure at which the compressor can be supplied with oil. If the value is much larger than the lower limit value, the condition is satisfied and no control is performed. In this state, the operation is performed at a discharge pressure higher than necessary based on the idea that the required differential pressure can be ensured by increasing the discharge pressure, and the operation efficiency of the compressor is not necessarily good.

  An object of the present invention is to realize a refrigeration apparatus that secures a required amount of oil supplied to a compressor, increases refrigeration capacity, and enables high-efficiency operation by reducing power consumption.

  In order to solve the above-described problems, a refrigeration apparatus according to the present invention sequentially includes a compressor, an oil separator that separates refrigeration oil from refrigerant discharged from the compressor, an air-cooled condenser having a blower fan, a decompression device, and an evaporator. In a refrigeration system that connects and configures a refrigeration cycle, and supplies refrigerating machine oil separated by an oil separator to a compressor using a pressure difference between a high-pressure side pressure and a low-pressure side pressure generated by the compression action of the compressor , Equipped with pressure detection means for detecting the pressure of the suction part and the discharge part of the compressor, respectively, and setting the target discharge pressure of the compressor corresponding to the minimum required oil supply amount of the compressor according to the detected pressure of the suction part The number of rotations of the blower fan is controlled so that the detected pressure of the part becomes the target discharge pressure.

  In this case, when the detected pressure of the discharge unit is higher than the target discharge pressure, control is performed to increase the rotational speed of the blower fan.

  In other words, the target discharge pressure can be obtained from the detected pressure of the suction portion and the differential pressure that satisfies the minimum required oil supply amount. Therefore, by preparing the target discharge pressure value corresponding to the suction pressure in advance, The target discharge pressure can be set based on the detected pressure of the part. Here, for example, when the detected pressure of the discharge part of the compressor is higher than the target discharge pressure, that is, when the minimum required amount of oil is satisfied, the rotational speed of the blower fan is increased, the amount of condensation is increased, and the discharge pressure is increased. By lowering the pressure, the operation can be continued with the detected pressure of the discharge section always approaching the target discharge pressure. By controlling the discharge pressure of the compressor to always become the target discharge pressure in this way, it becomes possible to operate the discharge pressure to the minimum necessary, so the power consumption of the compressor is reduced and the efficiency is high. Driving is possible. Moreover, since the enthalpy effect is increased by lowering the refrigerant temperature at the outlet of the condenser, the refrigeration capacity can be improved.

  Here, when a two-stage compressor that compresses the refrigerant in two stages is used as the compressor, the pressure detecting means detects the discharge pressure of the second-stage compressor and the suction pressure of the first-stage compressor, respectively. Refrigerating machine oil is supplied between the compressor and the second stage compressor. In this case as well, the target discharge pressure is determined from the detected pressure at the suction portion of the first stage compressor and the differential pressure that satisfies the minimum required amount of oil supplied between the first stage compressor and the second stage compressor. By setting, the same control as described above can be performed.

  ADVANTAGE OF THE INVENTION According to this invention, while ensuring the required amount of oil supply to a compressor, the refrigerating apparatus which makes high efficiency driving | operation possible by increasing refrigerating capacity and reducing power consumption is realizable.

It is a figure which shows the whole structure of the freezing apparatus formed by applying this invention. It is a figure which shows typically the connection location of a pressure compound meter and a pressure sensor. It is a figure which shows the relationship between discharge pressure and the amount of oil supply. It is a figure which shows each pressure of the refrigerant | coolant discharge pressure of a compressor, the oil supply pressure of the oil isolate | separated from the discharge refrigerant | coolant, the intermediate pressure, and the suction pressure of a compressor with the evaporation temperature of the refrigerant | coolant in an evaporator. It is a figure which shows the relationship between suction pressure and target discharge pressure. It is a figure which shows typically the refrigerating cycle of the state where the discharge pressure before control is high, and the state where the discharge pressure after control is reduced.

  Hereinafter, embodiments of a refrigeration apparatus to which the present invention is applied will be described in detail with reference to the drawings. In this embodiment, an example in which a two-stage screw compressor is used as the compressor will be described. However, the present invention is not limited to this example, and may be applied to various compressors such as a single-stage screw compressor. Is possible.

  FIG. 1 is a diagram illustrating the overall configuration of the refrigeration apparatus of the present embodiment. The refrigeration apparatus of the present embodiment is a refrigeration cycle in which a two-stage screw compressor 1 (hereinafter abbreviated as a compressor 1), an air-cooled condenser 3, a main expansion valve 5, an evaporator 6 and the like are connected by refrigerant piping. Is forming. A blower fan 14 that blows air for heat exchange to the condenser 3 is provided in the vicinity of the condenser 3.

  An oil separator 2 that separates refrigeration oil (hereinafter abbreviated as oil) from the refrigerant discharged from the compressor 1 is provided on the discharge side of the compressor 1, and the oil separator 2 separates the refrigerant from the refrigerant. The oil is returned to the compressor 1 through the piping path a via the oil cooler 7. Between the condenser 3 and the main expansion valve 5, a supercooler 4 for cooling the refrigerant condensed in the condenser 3 is provided.

  The downstream side of the subcooler 4 is branched from the piping system path b on the upstream side of the electromagnetic valve 8 and the piping system path b connected to the evaporator 6 by sequentially arranging the electromagnetic valve 8 and the main expansion valve 5. , The solenoid valve 11, the supercooling expansion valve 12, and the supercooler 4 are arranged in this order, and the piping system path c connected to the compressor 1 and the branching point where the piping system path c branches from the piping system path b The solenoid valve 10, the oil cooling expansion valve 9, and the oil cooler 7 are sequentially arranged and distributed to the piping system d connected to the compressor 1. . Here, the piping system path c and the piping system path d are both connected between the low stage side and the high stage side of the compressor 1.

  A pressure sensor 15 for detecting the suction pressure is provided on the suction side of the compressor 1, and a pressure sensor 16 for detecting the discharge pressure is provided on the discharge side. The pressure sensors 15 and 16 and the blower fan 14 are electrically connected to the control device 17, and a control signal output from the control device 17 based on a signal from the pressure sensors 15 and 16 is input to the blower fan 14. It has become so.

  FIG. 2 is a diagram schematically showing the connection location of the pressure sensor of the compressor 1. FIG. 2 (a) uses the two-stage compressor of the present embodiment, and FIG. 2 (b) uses the single-stage compressor. The connection part of the pressure sensor in the case of being present is shown.

  In the two-stage compressor 1, as shown in FIG. 2A, a low-pressure side pressure compound meter 25 is connected to a refrigerant return pipe 21 having one end connected to an end face on the suction side of the compressor 1 via a pipe 23. The pressure sensor 15 is connected to a point where the pipe 23 is branched on the way. The pressure sensor 16 is connected to a refrigerant discharge pipe 27 having one end connected to the discharge-side end face of the compressor 1 via a pipe 29. An oil supply pipe 31 is connected to a substantially central portion in the longitudinal direction of the compressor 1, that is, a portion between the low stage side and the high stage side of the compressor 1. Detection signals from the pressure sensors 15 and 16 are input to the control device 17.

  On the other hand, when the single-stage compressor 20 is used, as shown in FIG. 2B, the pressure on the low-pressure side is connected via a pipe 23 to a refrigerant return pipe 21 having one end connected to the suction-side end face of the compressor 20. A compound meter 25 is connected, and a pressure sensor 15 is connected to a point where the pipe 23 is branched. The pressure sensor 16 is connected via a pipe 29 to a refrigerant discharge pipe 27 having one end connected to the discharge-side end face of the compressor 20. An oil supply pipe 31 is connected to the discharge side of the compressor 20. In the present embodiment, the pressure sensors 15 and 16 are connected to the refrigerant return pipe 21 and the refrigerant discharge pipe 27 via pipes, respectively, but are connected to the suction port and the discharge port of the compressor via pipes, respectively. It may be directly connected.

  Next, the basic operation of the refrigeration apparatus of the present embodiment will be described with reference to FIG. The solid line arrow in the figure indicates the flow direction of the refrigerant, and the broken line arrow indicates the flow direction of the refrigerating machine oil.

  The refrigerant that is sequentially compressed at the low and high stages of the compressor 1 becomes a high-temperature and high-pressure refrigerant gas, and is discharged from the compressor 1 together with oil, and then led to the oil separator 2 where the oil is refrigerant gas. Separated from. When the refrigerant gas is led to the condenser 3, it is cooled and condensed by exchanging heat with air to become a liquid refrigerant. When this liquid refrigerant is guided to the supercooler 4, it is further cooled by exchanging heat with the refrigerant decompressed by the supercooling expansion valve 12, and then becomes a low-pressure wet gas by the action of the main expansion valve 5. Subsequently, the low-temperature liquid refrigerant guided to the evaporator 6 is sucked into the compressor 1 after the cooled fluid is cooled and evaporated.

  On the other hand, the oil separated by the oil separator 2 and accumulated at the bottom of the oil separator 2 flows into the oil cooler 7 by the action of pressure. The oil introduced into the oil cooler 7 is cooled by exchanging heat with the refrigerant decompressed by the oil cooling expansion valve 9. After the foreign matter in the oil is removed by the oil strainer, the cooled oil is supplied to the compressor oil supply port 13 by the differential pressure between the pressure of the oil and the pressure of each bearing portion that is an intermediate pressure portion of the compressor 1. Is done.

  The pressure relationship in the oil supply system (including the piping path a) from the oil separator 2 to the bearing portion of the compressor 1 is oil separator 2> oil cooler 7> bearing portion of the compressor 1, and compression The oil discharged from the machine 1 and separated by the oil separator 2 is supplied to the bearing portion of the compressor 1 by the differential pressure.

  FIG. 3 shows the relationship between the discharge pressure of the compressor 1 and the amount of oil supplied to the compressor 1. The discharge pressure can be detected by the pressure sensor 16. As shown in the figure, the discharge pressure on the horizontal axis and the oil supply amount on the vertical axis are in a substantially proportional relationship, and when the suction pressure is constant, the oil supply differential pressure increases as the discharge pressure increases, so the oil supply amount increases. The lower the discharge pressure, the smaller the oil supply differential pressure, so the oil supply amount decreases. Further, since the minimum required oil supply amount is set in advance for each compressor, the minimum required differential pressure for satisfying the minimum required oil supply amount can also be set in advance. Therefore, the discharge pressure PD when the oil pressure becomes the minimum necessary differential pressure becomes the lower limit of the discharge pressure, that is, the target discharge pressure. Here, if the suction pressure fluctuates, the discharge pressure that can ensure the minimum required differential pressure also fluctuates. Therefore, a target discharge pressure corresponding to the minimum necessary differential pressure is set in advance according to the suction pressure. If the operation is performed so that the discharge pressure becomes the target discharge pressure, it is possible to ensure the amount of oil required for the compressor 1, that is, the minimum required amount of oil.

  Next, FIG. 4 shows the discharge pressure (thin line) of the compressor 1, the oil supply pressure of the oil separated from the discharge refrigerant (dotted line), the intermediate pressure at the bearing (dashed line), and the suction pressure of the compressor 1 (thick line). These pressures are shown in relation to the evaporation temperature of the refrigerant in the evaporator 6. Here, the oil supply pressure is the pressure of the oil separated by the oil separator 2, for example, the pressure applied to the oil accumulated at the bottom of the oil separator 2. The oil supply pressure is a pressure lower than the discharge pressure by a predetermined pressure loss (for example, about 0.05 MPa), and fluctuates following the discharge pressure. Further, the intermediate pressure is a pressure at each bearing portion, which is an intermediate pressure portion between the first stage and the second stage of the compressor 1, and is, for example, a pressure substantially equal to the discharge pressure of the first stage of the compressor 1. ing. In this embodiment, the oil supply pressure and the intermediate pressure are not detected by a pressure gauge, and both are treated as estimated pressures.

  Actually, the amount of oil supplied to the compressor 1 varies depending on the differential pressure (ΔP) between the oil supply pressure and the intermediate pressure, but in this embodiment, the discharge pressure is controlled to ensure a predetermined amount of differential pressure. The minimum required amount of oil is to be secured. In other words, assuming that the suction pressure is constant, the higher the discharge pressure, the higher the oil supply pressure, so the differential pressure between the oil supply pressure and the intermediate pressure increases, the oil supply amount increases, and conversely the discharge pressure decreases. Since the oil supply pressure is also low, the differential pressure between the oil supply pressure and the intermediate pressure becomes small, and the oil supply amount decreases. If the discharge pressure is constant, the lower the suction pressure, the larger the oil supply differential pressure and the oil supply amount.

  FIG. 5 shows a target discharge pressure value corresponding to an arbitrary suction pressure. An arbitrary suction pressure is set to PS1, PS2,..., And a target discharge pressure for PS1 is set to PD1, a target discharge pressure for PD2, and so on. At this time, the target discharge pressure is set (solid line) at a value lower than the discharge pressure (dotted line) when operated by conventional control. The target discharge pressure set in this way is approximately proportional to the suction pressure.

  Here, when the target discharge pressure at an arbitrary suction pressure (pressure detected by the pressure sensor 15) is PD and the discharge pressure detected by the pressure sensor 16 during operation is PD ', the refrigeration apparatus is operated. Sometimes, if PD <PD ′, the rotational speed of the blower fan 14 is increased so that PD ′ approaches the PD to lower the discharge pressure. If PD> PD ′, the rotational speed of the blower fan 14 Is controlled so as to increase the discharge pressure. If PD≈PD ′, control is performed so that the rotation speed of the blower fan 14 is maintained and the discharge pressure is not changed.

  FIG. 6 shows a state where the discharge pressure is higher than the target discharge pressure (broken line) and a state where the rotation speed of the blower fan 14 is increased and the discharge pressure is lowered so that the discharge pressure approaches the target discharge pressure (solid line). A refrigerating cycle is shown typically. As shown in the figure, by reducing the discharge pressure from Pd2 to Pd1, the liquid temperature at the outlet of the condenser 3 and the liquid temperature at the outlet of the subcooler 4 are lowered, the enthalpy effect is increased, and the refrigeration capacity is improved. . Moreover, since the power consumption of the compressor 1 is significantly reduced due to a decrease in the discharge pressure, an extremely efficient operation is possible.

  Further, since the bearing load of the compressor 1 is reduced due to the reduction of the discharge pressure, the life of the bearing can be extended and the size can be reduced, and further, the overhaul time can be extended and the maintenance cost can be reduced. In addition, since the control device 17 constantly monitors the suction pressure and the discharge pressure to control the discharge pressure, the reliability is improved. It becomes possible to cope.

  In the control of this embodiment, the lower the outside air temperature is, for example, in a cold district, the easier it is to lower the condensation temperature, and by increasing the speed of the blower fan 14, the discharge pressure can be reduced more easily. The lower the outside air temperature, the longer the time during which the discharge pressure can be operated at the minimum value (target discharge pressure), and high-efficiency operation becomes possible over a long period of time. Also, since the refrigeration capacity is greatly increased, the capacity of the device can be reduced depending on the use conditions. In addition, even in a cold area, under conditions where the outside air temperature is lower than during the daytime, such as in the middle period or at night, the operation can be performed with the discharge pressure lowered to the minimum value as in this embodiment. An effect can be obtained.

  In this embodiment, an example using a screw type compressor has been described, but the present invention is not limited to this example, and can be applied to, for example, a scroll type compressor.

  In the present embodiment, the example in which the rotation speed of the blower fan 14 is controlled in order to adjust the discharge pressure has been described. However, as another reference example, for example, a water cooling system is incorporated in the condenser 3 and the condenser 3 is installed. It is also possible to control the discharge pressure by controlling the temperature and flow rate of the liquid refrigerant for cooling.

1 Two-stage screw compressor (compressor)
2 Oil separator 3 Air-cooled condenser 4 Supercooler 5 Main expansion valve 6 Evaporator 7 Oil cooler 8, 10, 11 Solenoid valve 12 Supercooling expansion valve 13 Compressor oil supply port 14 Blower fan 15, 16 Pressure sensor 17 Control device

Claims (3)

A compressor, an oil separator that separates refrigeration oil from refrigerant discharged from the compressor, an air-cooled condenser having a blower fan, a decompression device, and an evaporator are sequentially connected to form a refrigeration cycle. In the refrigerating apparatus for supplying the compressor with the refrigerating machine oil separated by the oil separator using the pressure difference between the high-pressure side pressure and the low-pressure side pressure generated by the compression action,
Pressure detecting means for detecting the pressure of the suction portion and the discharge portion of the compressor,
The target discharge pressure of the compressor corresponding to the minimum required oil supply amount of the compressor is set according to the detected pressure of the suction unit, and the blower fan is set so that the detected pressure of the discharge unit becomes the target discharge pressure. A refrigeration apparatus characterized by controlling a rotation speed.   2. The refrigeration apparatus according to claim 1, wherein when the detected pressure of the discharge unit is higher than the target discharge pressure, the rotational speed of the blower fan is increased. The compressor is a two-stage compressor that compresses the refrigerant in two stages,
The pressure detection means detects the discharge pressure of the second stage compressor and the suction pressure of the first stage compressor,
The refrigerating apparatus according to claim 1 or 2, wherein the refrigerating machine oil is supplied between the first stage compressor and the second stage compressor.

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