JP2012072919A - Refrigerating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerating device which detects the shortage of oil inexpensively when an amount of oil in an oil tank is reduced, and is provided with a highly reliable oil shortage detecting function which hardly causes malfunction due to a change of oil level.SOLUTION: The refrigerating device includes a compressor 1, an oil separator 2, an oil tank 8, and an oil cooler 9 for cooling an oil in the oil tank and supplying it to the compressor. A plurality of compressors are provided, and a discharge temperature sensors 11 is provided to each of the compressors. The oil cooler is provided with an oil inlet 12 on an upstream side for oil flow and a plurality of oil outlets 13 on a downstream side, and the oil outlets are provided on the upper portion of the oil cooler and are arranged in sequence from the upstream to the downstream side in the flow direction of oil and they are connected with any of the compressors, respectively. Discharge temperatures detected by the discharge temperature sensors of each of the compressors are compared to detect a decrease of oil amount in the oil tank.

Description

  The present invention relates to a refrigeration apparatus having an oil cycle in which oil is separated from compressed refrigerant gas discharged from a compressor and refueled to a necessary portion of the compressor, and in particular, a screw refrigerator having a plurality of screw compressors. It is suitable for.

  For example, in a screw refrigerator as a refrigeration apparatus, an oil cycle is configured, and oil in compressed refrigerant gas discharged from the compressor is separated by an oil separator, and the separated oil is separated from an oil tank and an oil cooler. After that, the oil is again supplied to the necessary portions of the compressor.

  In a conventional refrigeration system, an oil level sensor using a float or the like is attached to an oil reservoir such as an oil tank, etc., and the presence or absence of oil is detected by the height of the oil level. There is something that detects whether or not.

5 and 6 each show a conventional example in which an oil level sensor is attached to an oil tank.
In the example of FIG. 5, the oil level sensor 16 is directly attached to the oil tank 8, and the oil level sensor 16 including the float 17 is attached to the oil tank 8 via the connection port 18 and the flange portion 19. . The oil level sensor 16 detects the oil level in the oil tank 8 by a float 17, and when there is a required amount of oil, the float 17 floats and the electrical contact is turned off. ing. When the oil in the oil tank 8 is reduced and the oil level is lowered, the float 17 is lowered, and when reaching the lowermost part, the electrical contact is turned on, and this is used as an input signal for the control panel. Built in control within.

In the example shown in FIG. 6, the oil reservoir 20 is provided outside the oil tank 8, the oil level sensor 16 is installed in the oil reservoir 20, and the oil reservoir 20 and the oil tank 8 are connected to the liquid side pipe. 21 and the gas side pipe 22 are connected to equalize the pressure in the oil tank 8 and the oil reservoir 20. The oil level of the oil reservoir 20 is detected by the oil level sensor 16 in the same manner as in the example shown in FIG. 5, thereby determining the oil level in the oil tank 8 and detecting the presence or absence of oil. I am doing so.
In addition, there exists a thing of patent document 1 etc. as this kind of prior art.

JP 2001-124388 A

  In the oil cycle in the refrigeration apparatus such as the screw refrigerator described above, generally, the difference between the oil supply pressure (discharge side pressure) and the low pressure side (suction pressure or intermediate pressure) causes the compressor bearing part to be required. A differential pressure lubrication system is used to lubricate. In addition, a plurality of compressors of a single stage or a two-stage compressor are mounted, and an oil cycle is often constituted by an oil separator, an oil tank, a shell and tube type oil cooler, and the like.

  In such a refrigeration system, in a situation where the operating conditions change, such as during a trial operation or when the operating conditions after defrosting are switched, a large amount of oil flows out of the compressor together with the refrigerant. In other words, the so-called oil rise in which the amount of oil in the oil tank decreases tends to increase, and the amount of oil held in the refrigeration apparatus may also decrease. In such a case, the amount of oil in the oil tank decreases, so that the amount of oil supplied to the compressor is insufficient, and in the worst case, the compressor rotor part overheats and leads to solid astringency. There are things to do.

  Therefore, conventionally, as shown in FIGS. 5 and 6, the oil level sensor 16 is provided in the oil tank 8 and the oil reservoir 20, but in order to attach the oil level sensor 16 to the oil tank 8 and the like, In addition, modification of the equipment and modification of the control, such as incorporating detection by the oil level sensor into the control, are required, and there are many modification items and the number of parts increases.

  That is, in the case shown in FIG. 5, it is necessary to additionally install the connection port 18 and the flange portion 19 for attaching the oil level sensor 16 to the oil tank 8, and electrical modification is also required. 6 also requires modification of the oil tank 8, connection pipes 21 and 22 between the oil tank 8 and the oil reservoir 20, and electrical modification. Accordingly, there is a problem in that the number of parts is increased in the case where the oil level sensor is attached, and the cost for remodeling is increased.

In addition, the above-described prior art is liable to malfunction due to oil level fluctuations, and there is a problem in terms of ensuring the reliability of the compressor.
Because of these problems, there are few examples in which a protection device using an oil level sensor is attached.

  The object of the present invention is to realize a low-cost detection of an oil shortage when the amount of oil held in the oil tank decreases and the oil becomes insufficient. It is to obtain a refrigeration apparatus having a high oil shortage detection function.

  In order to achieve the above object, the present invention provides a compressor, an oil separator that separates oil from a refrigerant discharged from the compressor, an oil tank that stores the separated oil, and an oil in the oil tank. In the refrigeration apparatus comprising an oil cooler that cools and supplies the compressor to the compressor, a plurality of the compressors are provided, and a discharge temperature sensor that detects the temperature of the discharge gas from each compressor is provided. Provided in the compressor, the oil cooler is provided with an oil inlet on the upstream side with respect to the flow of oil flowing in the oil cooler, and provided with a plurality of oil outlets on the downstream side that are more than the number of compressors. The plurality of oil outlets are provided in the upper part of the oil cooler and sequentially arranged from the upstream side to the downstream side in the oil flow direction, and each oil outlet is connected to one of the plurality of compressors, Detected by the discharge temperature sensor of each compressor And detecting a decrease in the oil amount of the oil tank by comparing the discharge temperature that is.

  According to the present invention, when the amount of oil held in the oil tank decreases and the oil becomes insufficient, it is possible to realize the detection of the oil shortage at low cost, and it is also difficult to cause a detection malfunction due to oil level fluctuation. A refrigeration apparatus having a high oil shortage detection function can be obtained.

The refrigeration cycle system | strain diagram which shows Example 1 of the freezing apparatus of this invention. The top view which shows the structure of the oil cooler shown in FIG. It is a longitudinal cross-sectional view of the oil cooler shown in FIG. 2, and the figure explaining the flow of the oil in an oil cooler. The diagram explaining the change of the compressor discharge temperature with progress of time when the oil holding amount in the oil tank shown in FIG. 1 reduces. It is a figure explaining an example of the oil shortage detection means in the conventional freezing apparatus, and the front view which shows an oil tank in a partial cross section in the example which attached the oil level sensor to the oil tank. It is a figure explaining the other example of the oil shortage detection means in the conventional freezing apparatus, and is a schematic block diagram which shows the example which has provided the oil sump part provided with the oil level sensor outside the oil tank.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a refrigeration cycle diagram showing Embodiment 1 of the refrigeration apparatus of the present invention. In this embodiment, a water-cooled screw refrigerator equipped with a two-stage screw compressor will be described. Moreover, the oil cycle which comprises separating the oil from the compressed refrigerant gas discharged from the compressor and refueling the necessary portion of the compressor is constituted.

  In the figure, reference numeral 1 (1a, 1b, 1c) denotes a compressor, which is a two-stage screw compressor in this embodiment, and three such two-stage screw compressors are connected in parallel. Moreover, the solid line arrow shows the flow of the refrigerant, and the broken line arrow shows the flow of oil (refrigerating machine oil). The refrigerant is compressed on the low-stage side and the high-stage side of the compressor 1 to become a high-temperature and high-pressure refrigerant gas, and is discharged together with the oil that has lubricated the compressor 1, and enters the oil separator 2. Here, after separating the oil from the refrigerant gas, the refrigerant gas flows into the condenser 3, is cooled by the cooling water supplied to the condenser 3, is condensed, and becomes a liquid refrigerant. Thereafter, the temperature of the refrigerant is further lowered by the supercooler 4. A part of the liquid refrigerant branches from the downstream side of the supercooler 4 and is decompressed and expanded by the expansion valve 5 for the supercooler. After the main liquid refrigerant is cooled by the supercooler 4, It flows into the stage (between the lower stage side and the higher stage side). In this embodiment, three subcoolers 4 are provided in the same number as the compressors 1, and the refrigerant after cooling the mainstream refrigerant in each of the subcoolers 4 is injected into the corresponding compressor 1. Has been.

  The main-stream liquid refrigerant discharged from the subcooler 4 flows into the evaporator 7 as a low-pressure wet gas by the action of the main expansion valve 6, and cools and evaporates the cooled fluid 30 flowing in the evaporator 7. Then, it is sucked into the compressor 1.

  On the other hand, the refrigerating machine oil separated from the refrigerant gas by the oil separator 2 flows into the oil tank 8 from the oil separator 2, and the oil accumulated in the oil tank 8 enters the oil cooler 9 and is cooled by the cooling water. Is done. The cooled oil passes through the oil strainer 10 to remove foreign matter in the oil, and then becomes a discharge side pressure (oil supply pressure) and a low pressure side pressure (generally an intermediate pressure such as a pressure of each bearing portion) of the compressor. The pressure difference between the compressor 1 and the bearing portion of the compressor 1 is used to supply oil. In order to supply oil to the bearings, etc., the compressor 1 is provided with oil supply ports on the low-stage side and the high-stage side of the two-stage compressor, and the oil from the oil strainer 10 is supplied with this oil supply. Refueled to the mouth.

The relationship of the pressure in the oil supply system from the oil separator 2 to the bearing portion of the compressor 1 is
Refrigerating machine oil discharged from the compressor 1 and separated by the oil separator 2 by the differential pressure of each part is oil compressor 2> oil cooler 8> compressor 1 bearing. Oil is supplied to each bearing portion 1. In addition, when the compressor 1 is a two-stage screw compressor, the bearings are normally at an intermediate pressure. However, when a single-stage screw compressor is used as the compressor 1, The bearing is at the suction pressure. Accordingly, the oil from the oil cooler 8 is supplied to the bearing portion or the like by a differential pressure between the oil supply pressure (discharge side pressure) in the oil cooler and the intermediate pressure or the suction pressure.

  Note that a discharge temperature sensor 11 for detecting the temperature of the discharged refrigerant gas is provided in the discharge pipe on the discharge side of each compressor 1, and the discharge temperature of each compressor 1 is constantly set during operation of the refrigeration apparatus. I try to detect it.

The structure of the oil cooler 9 shown in FIG. 1 will be described with reference to FIGS. FIG. 2 is a plan view of the oil cooler 9, and FIG. 3 is a longitudinal sectional view of the oil cooler.
As shown in these drawings, in this embodiment, the oil cooler 9 is a water-cooled and horizontal shell-and-tube oil cooler. Further, the oil cooler 9 is provided with an oil inlet 12 on the upstream side with respect to the flow of oil flowing in the oil cooler, and on the downstream side, a plurality of oil coolers more than the number of the compressors 1 shown in FIG. (Three in this example) oil outlets 13 (13a, 13b, 13c) are provided. The plurality of oil outlets 13 are provided in the upper part of the oil cooler 9 and are sequentially arranged from the upstream side to the downstream side in the oil flow direction, and each oil outlet 13 is connected to one of the plurality of compressors 1. Connected. That is, the most upstream oil outlet 13a is connected to the compressor 1a, the central oil outlet 13b is connected to the compressor 1b, and the most downstream oil outlet 13c is connected to the compressor 1c.

  Further, the oil cooler 9 is of a shell and tube type, and the internal structure thereof has a plurality of cooling pipes 15 arranged in the longitudinal direction in the shell as shown in FIG. It is configured to enter from the inlet and to discharge from the cooling water outlet. Also, a plurality of baffles 14 are alternately arranged in the longitudinal direction of the shell in the shell so that the oil entered from the oil inlet 12 flows toward the oil outlet 13 while meandering up and down in the shell. It is configured. When the cooling water flows through the cooling pipe 15, the oil is cooled to a temperature of about 40 to 60 ° C. by exchanging heat with the oil flowing through the oil inlet 12 while meandering by the baffle 14. The baffle 14A arranged on the most downstream side is provided on the upper side in the shell, and the plurality of oil outlets 13 are provided on the oil cooler 9 on the further downstream side than the baffle 14A.

  When the amount of oil retained in the oil tank 8 of the refrigeration apparatus shown in FIG. 1 is reduced to such an extent that the oil level cannot be formed, the refrigerant gas is also involved when the oil flows from the oil tank 8 to the oil cooler 9. When the oil holding amount in the oil tank 8 is sufficient, the oil cooler 9 is filled with oil. However, when the amount of oil held in the oil tank 8 decreases and refrigerant gas is mixed into the oil cooler 9, the refrigerant gas is not liquefied so much in the oil cooler 9, and remains in the oil cooler 9 as a gas. To the downstream side, discharged from the oil outlet 13, and supplied to the compressor 1 through the oil supply pipe.

  In the oil cooler 9, the oil that has passed through the baffle (the most downstream baffle) 14 </ b> A closest to the outlet side has inertia due to the flow from the oil inlet 12 to the oil outlet 13, and further (the most downstream oil). It tries to flow to the outlet 13c side). On the other hand, since the refrigerant gas is in the form of bubbles, the refrigerant gas tends to float upward immediately after passing through the baffle 14A. In this embodiment, a plurality of oil outlets 13 are arranged in the upper part of the oil cooler 9 in order from the upstream side to the downstream side in the axial direction (oil flow direction). The oil flowing out from the oil outlet 13a (upstream side) contains a large amount of gas refrigerant, and the amount of gas refrigerant contained in the oil decreases as the oil outlet 13c side farthest (most downstream). For this reason, since a large amount of refrigerant gas is mixed in the compressor 1a connected to the oil outlet 13a on the most upstream side and a necessary oil supply amount is not ensured, the discharge temperature of the compressor 1a gradually increases. To go.

  FIG. 4 is a diagram for explaining changes in the compressor discharge temperature with the passage of time when the amount of oil retained in the oil tank 8 shown in FIG. 1 decreases. In FIG. 4, the dotted line shows the change in the discharge temperature of the compressor in which the oil supply amount is insufficient, and the solid line shows the change in the discharge temperature of the compressor during normal operation in which the oil supply amount is sufficiently secured.

  That is, when the amount of oil retained in the oil tank 8 decreases and the amount of gas refrigerant flowing into the oil cooler 9 increases, the oil flowing out from the upstream oil outlet 13a contains a lot of gas refrigerant. The required amount of oil supply is not secured in the compressor 1a connected to the compressor 1a, and the discharge temperature of the compressor 1a rises as shown by the dotted line in FIG. Since the oil flowing out from the downstream oil outlets 13b and 13c contains almost no gas refrigerant, the compressors 1b and 1c connected to these oil outlets 13b and 13c have the required amount of oil supply, The discharge temperature of the compressor does not increase as shown by the solid line in FIG. 4 (or if the oil amount in the oil tank 8 further decreases, the discharge temperature may increase as the oil amount decreases, but the rate of increase is moderate. Become). For this reason, a difference occurs in the discharge temperature between the compressor 1a in which the amount of oil supply is insufficient and the compressors 1b and 1c in which the required amount of oil is supplied, and an oil tank is obtained by obtaining the difference ΔT in the discharge temperature. It is possible to determine that the oil holding amount of No. 8 has decreased and that an oil supply failure has occurred due to an oil shortage.

  That is, if the oil holding amount in the oil tank 8 is sufficient, the required oil amount is supplied from the oil cooler 9 to all the compressors 1a, 1b, 1c, so the discharge temperature of any compressor is As shown by the solid line in FIG. 4, the operation is performed at a substantially approximate discharge temperature. However, as described above, when the temperature difference ΔT occurs in the discharge temperature, it can be determined that a sufficient amount of oil is not secured in the oil tank 8, so an allowable value (a constant value) is set in advance for this temperature difference ΔT. When the set time t has passed with ΔT exceeding the allowable value, it is determined that the amount of oil retained in the oil tank 8 has decreased, and an alarm is issued or refrigeration is performed. Protective control is performed to stop the device in an emergency.

  For example, if the discharge temperature during normal operation is 80 ° C., the discharge temperature of one compressor 1a is 100 ° C., and if the discharge temperatures of the other compressors 1b and 1c remain 80 ° C., the temperature difference ΔT Reaches 20 ° C. When the allowable value of the temperature difference ΔT is set to 20 ° C., the refrigeration apparatus is controlled as a shortage of oil when a predetermined set time t (for example, about 10 seconds to 1 minute) elapses after the allowable value is exceeded. It is preferable to perform a control such that an oil shortage alarm is issued on the monitor of the control panel or the refrigeration apparatus is stopped from the control panel.

  The discharge temperature sensor 11 provided on the discharge side of each compressor 1 is standardly provided in the refrigeration apparatus, and the discharge temperature of each compressor 1 is detected using the discharge temperature sensor 11. By doing so, it is possible to implement this embodiment without additionally installing a new discharge temperature sensor. Further, by using a control device such as a control panel provided in the refrigeration apparatus, the temperature difference ΔT of the discharge temperature between the compressors 1 is obtained from the detection value from each discharge temperature sensor 11, or the passage of time is measured. It should be configured to allow monitoring. Furthermore, it is preferable that the allowable value of the temperature difference ΔT and the setting time t can be set from the control device. As described above, in this embodiment, a control device such as a control panel provided in the refrigeration apparatus can be used as the oil shortage detection means.

  As a result, as in the conventional example shown in FIG. 5 and FIG. 6, modification of the oil tank for incorporating new parts such as the oil level sensor, modification of control such as incorporating detection by the oil level sensor in the control, This embodiment can be realized without performing electrical modification for the oil level sensor, and the protection control of the refrigeration apparatus against the shortage of oil becomes possible at low cost.

  For example, by detecting an oil shortage and issuing a warning to the outside, the operation status can be improved by the operation manager before the refrigeration system is stopped urgently. System failure can be prevented in advance.

  In the above-described embodiment, the case of the water-cooled shell and tube type oil cooler has been described. However, the invention is not limited to the water-cooled type, and a refrigerant cooling type that cools oil with a refrigerant may be used.

Moreover, although the said compressor demonstrated the example which used the two-stage screw compressor, it can implement similarly also with a single stage screw compressor. When the compressor is a two-stage screw compressor, the oil from the oil cooler is moved to the required locations such as the bearings of the compressor due to the differential pressure between the oil supply pressure in the oil cooler and the intermediate pressure of the compressor. Refueled. Further, when the compressor is a single-stage screw compressor, the oil from the oil cooler is caused by a differential pressure between the oil supply pressure in the oil cooler and the suction pressure of the compressor. Oil is supplied where necessary.
Furthermore, the compressor is not limited to a screw compressor, and can be applied to other types of compressors such as a turbo compressor and a scroll compressor.

  The plurality of oil outlets 13 provided in the oil cooler 9 are preferably provided at the uppermost part of the oil cooler 9, but are not limited to the uppermost part and may be provided at a part slightly lower than the uppermost part. If the most upstream oil outlet 13a is provided in the upper part of the oil cooler, the downstream oil outlets 13b and 13c may be provided below the most upstream oil outlet 13a.

As described above, according to this embodiment, the plurality of oil outlets are provided in the upper part of the oil cooler and are sequentially arranged from the upstream side to the downstream side in the oil flow direction, and each oil outlet is connected to the plurality of oil outlets. Each of the compressors is connected to each other, and a discharge temperature sensor provided in each compressor detects a discharge temperature of a specific compressor 1a and a discharge temperature of another compressor 1b or 1c. Since the configuration is such that when the temperature difference ΔT exceeds the allowable value, it is detected that the oil is insufficient, the following effects can be obtained.
(1) Since it is possible to detect a decrease in the amount of oil held in the oil tank using the discharge temperature sensor 11 that is provided as standard in each compressor of the refrigeration system, it is possible to detect oil shortage at a low cost at a low cost. Is possible. Further, since the oil level sensor is not used, a refrigeration apparatus having a highly reliable oil shortage detection function that hardly causes a detection malfunction due to oil level fluctuation can be obtained.
(2) Possible causes of abnormal rise in discharge temperature include various factors such as high cooling water temperature, insufficient amount of cooling water, contamination of heat exchanger, operation outside the operating range, etc. Monitoring alone will require a lot of time to investigate the final cause. On the other hand, in the present embodiment, there is an effect that it is possible to immediately detect that the oil is insufficient by detecting the temperature difference between the discharge temperatures of the plurality of compressors.
(3) When an oil shortage is detected, it can be reported to the outside so that the operation status can be improved by the operation manager. System down can be prevented beforehand.

1 (1a, 1b, 1c) ... compressor 2 ... oil separator 3 ... condenser 4 ... supercooler 5 ... supercooler expansion valve 6 ... main expansion valve 7 ... evaporator 8 ... oil tank 9 ... oil cooler DESCRIPTION OF SYMBOLS 10 ... Oil strainer 11 ... Discharge temperature sensor 12 ... Oil inlet, 13 (13a, 13b, 13c) ... Oil outlet 14 ... Baffle, 15 ... Cooling pipe 16 ... Oil level sensor, 17 ... Float 18 ... Connection port, 19 ... Flange 20: Oil reservoir 21 ... Liquid side piping, 22 ... Gas side piping.

Claims (8)

An oil separator for separating oil from refrigerant discharged from the compressor; an oil tank for storing the separated oil; and oil cooling for cooling the oil in the oil tank and supplying the oil to the compressor In a refrigeration apparatus comprising a container,
A plurality of the compressors are provided, and each compressor is provided with a discharge temperature sensor that detects the temperature of the discharge gas from each compressor.
The oil cooler is provided with an oil inlet on the upstream side with respect to the flow of oil flowing in the oil cooler, and a plurality of oil outlets more than the number of the compressors are provided on the downstream side. The oil outlet is provided at the upper part of the oil cooler and sequentially arranged from the upstream side to the downstream side in the oil flow direction, and each oil outlet is connected to one of the plurality of compressors,
A refrigeration apparatus that detects a decrease in the amount of oil in the oil tank by comparing the discharge temperatures detected by the discharge temperature sensors of the compressors.   2. The refrigeration apparatus according to claim 1, wherein discharge temperatures respectively detected by the discharge temperature sensors of the compressors are compared, and when the temperature difference exceeds an allowable value, it is determined that oil is insufficient and an alarm is issued. A refrigeration apparatus comprising oil shortage detection means.   3. The refrigeration apparatus according to claim 2, wherein the oil shortage detecting means determines that the oil is insufficient when the temperature difference detected by each of the discharge temperature sensors has exceeded a permissible value for a predetermined time or longer. A refrigeration apparatus characterized by.   The refrigeration apparatus according to any one of claims 1 to 3, wherein the discharge temperature sensor is provided in a discharge pipe of each compressor and is connected to an oil outlet on the most upstream side provided in the oil cooler. A refrigeration apparatus characterized by determining that the oil is insufficient when the discharge temperature of the compressor rises by a predetermined value or more from the discharge temperature of another compressor.   5. The refrigeration apparatus according to claim 1, wherein the compressor is a two-stage screw compressor, and the oil from the oil cooler is supplied with an oil supply pressure in the oil cooler and an intermediate pressure of the compressor. The refrigerating machine is characterized in that oil is supplied to a required portion such as a bearing portion of a compressor by a differential pressure between the compressor and the compressor.   5. The refrigeration apparatus according to claim 1, wherein the compressor is a single-stage screw compressor, and oil from the oil cooler is supplied with oil supply pressure in the oil cooler and suction pressure of the compressor. The refrigerating machine is characterized in that oil is supplied to a required portion such as a bearing portion of a compressor by a differential pressure between the compressor and the compressor.   The refrigeration apparatus according to any one of claims 1 to 6, wherein the oil cooler is a horizontal shell-and-tube oil cooler.   8. The refrigeration apparatus according to claim 7, wherein the shell-and-tube oil cooler has a plurality of baffles arranged alternately in the longitudinal direction of the shell in the shell, and oil entered from the oil inlet passes through the shell. The baffle arranged to flow toward the oil outlet while meandering up and down, and the baffle arranged at the most downstream side is provided at the upper side in the shell, and the oil cooler further downstream than the baffle at the most downstream side The refrigeration apparatus characterized in that the plurality of oil outlets are provided at the top.

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