JP6873788B2 - Low temperature turbo chiller - Google Patents

Description

The present invention relates to a low-temperature turbo chiller that includes a plurality of compressors that compress refrigerant gas in multiple stages and can cool a fluid to be cooled (brine) to a low temperature in an evaporator.

A low-temperature turbo chiller that has a plurality of compressors that compress a refrigerant gas in multiple stages and cools a fluid to be cooled (brine) to a low temperature in an evaporator is known. Each compressor needs to lubricate sliding parts such as bearings and gears with lubricating oil. Therefore, each compressor has a built-in oil tank for storing lubricating oil, and the lubricating oil in the oil tank is pumped to sliding parts such as bearings and gears by an oil pump arranged in this oil tank. ..

Japanese Unexamined Patent Publication No. 2010-19541

The oil tank built into each compressor is equalized by the evaporator with the lowest pressure in the system and the connecting pipe. In a low-temperature turbo chiller that uses brine as the fluid to be cooled, the pressure inside the evaporator is lower than that of a normal turbo chiller that uses water as the fluid to be cooled, so the pressure inside the oil tank is also reduced. This makes it impossible to secure the NPSH (Net Positive Suction Head) required for the oil pump. Therefore, in the conventional low-temperature turbo chiller, the amount of lubricating oil sent to the sliding parts such as the bearings and gears of the compressor is reduced, which often causes a trouble that the safety device operates. Here, the NPSH required for the pump is an absolute pressure head required at the suction port of the pump so as not to cause performance deterioration such as cavitation.

The present invention has been made in view of the above circumstances, and it is possible to secure the NPSH required for an oil pump for pumping lubricating oil to a sliding portion such as a bearing of a compressor, and to lubricate the sliding portion. An object of the present invention is to provide a low-temperature turbo chiller capable of stably supplying oil.

In order to achieve the above object, the low temperature turbo refrigerating machine of the present invention is a low temperature turbo refrigerating machine including a plurality of compressors for compressing refrigerant gas in multiple stages, the first compressor and the first compressor. The first oil tank built in the oil tank, the second oil tank arranged below the first oil tank and configured to be always filled with lubricating oil, and the second oil tank. The first oil tank is provided with a first oil pump provided , a first oil connecting pipe connecting an oil discharge port of the first oil tank and an oil inlet of the second oil tank, and the first oil tank. The oil inflow port of the second oil tank is provided at a position below the oil discharge port of the above and at a position where the suction pressure required for the first oil pump or higher can be secured, and the first oil connecting pipe is made of oil. is Ri is der flow path cross-sectional area than can ensure continuous oil without interruption, provided with gas connection pipe for connecting the gas inlet of said gas outlet of the second oil tank first oil tank It is characterized by that.

According to a preferred embodiment of the present invention, the gas connecting pipe is characterized by having a flow path cross-sectional area or more capable of discharging the refrigerant gas dissolved in the oil at the time of starting.
According to a preferred embodiment of the present invention, the gas connecting pipe is connected to a position above the maximum liquid level of the first oil tank.
According to a preferred embodiment of the present invention, a branch pipe connected to the gas connecting pipe is provided at a predetermined position of the first oil connecting pipe.

According to a preferred embodiment of the present invention, a second compressor, the second and the third oil reservoir incorporated in the compressor, before Symbol second oil pump disposed in the second oil reservoir When the third further comprising an oil outlet of the oil tank and a second oil communication pipe for connecting the oil inlet of the second oil tank, the second oil tank, the first oil It is characterized in that it is arranged below the tank and the third oil tank.
According to a preferred embodiment of the present invention, the first compressor and the second compressor have the same oil level during operation of the first oil tank and the third oil tank. The feature is that each height position is set.
According to a preferred embodiment of the present invention, the first oil connecting pipe and the second oil connecting pipe are connected at a predetermined position.

According to the present invention, it is possible to secure the NPSH required for the oil pump for pumping the lubricating oil to the sliding portion such as the bearing of the compressor, and to stably supply the lubricating oil to the sliding portion. be able to.

FIG. 1 is a schematic view showing an embodiment of a low-temperature turbo chiller according to the present invention. FIG. 2 is a schematic diagram showing only the refueling system for the first turbo compressor in an enlarged manner. FIG. 3 is a schematic view showing another embodiment of the low temperature turbo chiller according to the present invention.

Hereinafter, embodiments of the low temperature turbo chiller according to the present invention will be described with reference to FIGS. 1 to 3. In FIGS. 1 to 3, the same or corresponding components are designated by the same reference numerals, and duplicate description will be omitted.
FIG. 1 is a schematic view showing an embodiment of a low-temperature turbo chiller according to the present invention. As shown in FIG. 1, in the low-temperature turbo refrigerator, the first turbo compressor 1-1 and the second turbo compressor 1-2 that compress the refrigerant gas in multiple stages and the compressed refrigerant gas as cooling water (cooling water ( Between the compressor 2 that cools and condenses with a cooling fluid), the evaporator 3 that removes heat from the brine (cooled fluid) and evaporates the refrigerant to exert a refrigerating effect, and between the condenser 2 and the evaporator 3. An economizer 4 which is an intermediate cooler to be arranged is provided, and each of these devices is connected by a refrigerant pipe 5 in which a refrigerant circulates.

The first turbo compressor 1-1 and the second turbo compressor 1-2 that compress the refrigerant gas in multiple stages are connected in series via the economizer 4. That is, the low-temperature low-pressure refrigerant gas discharged from the evaporator 3 is compressed by the first turbo compressor 1-1, and the refrigerant gas discharged from the first turbo compressor 1-1 is passed through the economizer 4. It is guided to the second turbo compressor 1-2 and further compressed by the second turbo compressor 1-2 to obtain a high-temperature and high-pressure refrigerant gas.

In the refrigeration cycle of the low-temperature turbo chiller configured as shown in FIG. 1, the first turbo compressor 1-1, the second turbo compressor 1-2, the condenser 2, the evaporator 3, and the economizer 4 are used. The refrigerant circulates, the brine is cooled to a low temperature (-5 ° C to -25 ° C) by the evaporator 3 to handle the load, and the amount of heat taken from the evaporator 3 taken into the refrigeration cycle and supplied from the compressor motor. The amount of heat corresponding to the work of the turbo compressors 1-1 and 1-2 is released to the cooling water supplied to the condenser 2. On the other hand, the gas refrigerant separated by the economizer 4 merges with the gas refrigerant from the first turbo compressor 1-1 and is compressed by the second turbo compressor 1-2. According to the economizer cycle, since the freezing effect portion of the economizer 4 is added, the freezing effect is increased by that amount, and the efficiency of the freezing effect can be improved as compared with the case where the economizer 4 is not installed.

As shown in FIG. 1, the first turbo compressor 1-1 includes a first oil tank 11. The first oil tank 11 is equalized with the evaporator 3 by the connecting pipe 26. A second oil tank 12 is arranged below the first oil tank 11. The second oil tank 12 is not built in the compressor, but is installed independently of the compressor. The oil discharge port 11a of the first oil tank 11 and the oil inflow port 12a of the second oil tank 12 are connected by a first oil connecting pipe 21. Therefore, the lubricating oil in the first oil tank 11 flows into the second oil tank 12 via the first oil connecting pipe 21.

The oil inflow port 12a of the second oil tank 12 is provided below the oil discharge port 11a of the first oil tank 11 and at a position where the suction pressure required for the first oil pump 31 or higher can be secured. The first oil connecting pipe 21 is set to have a flow path cross-sectional area or more that allows continuous oil continuity without interruption. Therefore, the lubricating oil is smoothly supplied from the first oil tank 11 to the second oil tank 12 via the first oil connecting pipe 21 without interruption in the middle. A first oil pump 31 is provided in the second oil tank 12. The first oil pump 31 pumps lubricating oil to sliding parts such as bearings and gears of the first turbo compressor 1-1. The gas outlet 12b of the second oil tank 12 and the gas inlet 11b of the first oil tank 11 are connected by a gas connecting pipe 25. The gas connecting pipe 25 is connected to a position above the maximum liquid level of the first oil tank 11. Therefore, the refrigerant gas dissolved in the lubricating oil is returned to the space above the oil storage portion of the first oil tank 11 via the gas connecting pipe 25, and the second oil tank 12 is always lubricated. It is configured to be filled with oil. The gas connecting pipe 25 is set to have a cross-sectional area of a flow path or larger capable of discharging the refrigerant gas dissolved in the oil when the refrigerator is started.

As shown in FIG. 1, the second turbo compressor 1-2 has a third oil tank 13 built-in. The pressure of the third oil tank 13 is equalized to that of the evaporator 3 by the connecting pipe 26. The second oil tank 12 is arranged below the third oil tank 13. The oil discharge port 13a of the third oil tank 13 and the oil inflow port 12c of the second oil tank 12 are connected by a second oil connecting pipe 22. Therefore, the lubricating oil in the third oil tank 13 flows into the second oil tank 12 via the second oil connecting pipe 22.

The oil inflow port 12c of the second oil tank 12 is provided below the oil discharge port 13a of the third oil tank 13 and at a position where the suction pressure required for the second oil pump 32 or higher can be secured. The second oil connecting pipe 22 is set to have a flow path cross-sectional area or more that allows continuous oil continuity without interruption. Therefore, the lubricating oil is smoothly supplied from the third oil tank 13 to the second oil tank 12 via the second oil connecting pipe 22 without interruption in the middle. A second oil pump 32 is provided in the second oil tank 12. The second oil pump 32 pumps lubricating oil to sliding parts such as bearings and gears of the second turbo compressor 1-2.

FIG. 2 is a schematic diagram showing only the refueling system for the first turbo compressor 1-1 in an enlarged manner. As shown in FIG. 2, the first turbo compressor 1-1 includes a first oil tank 11. A second oil tank 12 is arranged below the first oil tank 11. The oil discharge port 11a of the first oil tank 11 and the oil inflow port 12a of the second oil tank 12 are connected by a first oil connecting pipe 21. Therefore, the lubricating oil in the first oil tank 11 flows into the second oil tank 12 via the first oil connecting pipe 21. A first oil pump 31 is provided in the second oil tank 12. The first oil pump 31 pumps lubricating oil to sliding portions such as bearings and gears of the first turbo compressor 1-1 via an oil supply pipe 30. The gas outlet 12b of the second oil tank 12 and the gas inlet 11b of the first oil tank 11 are connected by a gas connecting pipe 25. The gas connecting pipe 25 is connected to a position above the maximum liquid level of the first oil tank 11. Although not shown in FIG. 2, the third oil tank 13 built in the second turbo compressor 1-2 is connected to the second oil tank 12, and the second oil tank It is as shown in FIG. 1 that the second oil pump 32 is arranged in 12.

According to the low-temperature turbo chiller of the present invention shown in FIGS. 1 and 2, the first oil tank 11 incorporated in the first turbo compressor 1-1 and the second turbo chiller incorporated in the second turbo compressor 1-2. A separate second oil tank 12 is installed at a position below the oil tank 13 of No. 3, and the first oil tank 11 and the second oil tank 12 are connected by the first oil connecting pipe 21. The third oil tank 13 and the second oil tank 12 are connected by a second oil connecting pipe 22. Then, the first oil pump 31 is arranged in the second oil tank 12, the lubricating oil is supplied to the first turbo compressor 1-1 by the first oil pump 31, and the second oil tank 12 is supplied with lubricating oil. A second oil pump 32 is arranged, and lubricating oil is supplied to the second turbo compressor 1-2 by the second oil pump 32. In this way, as the installation position of the oil tank 12 is lowered downward, the hydraulic pressure due to the weight of the lubricating oil is applied to the suction ports of the oil pumps 31 and 32, so that the NPSH required for the oil pumps 31 and 32 should be secured. Can be done. Therefore, the pump does not deteriorate in performance such as cavitation, and the sliding parts such as the bearing of the compressor can be refueled without any problem.

Since the low-temperature turbo chiller requires two compressors, it also requires two oil tanks to be installed below the compressor, and these two oil tanks must be communicated with each other by a communication pipe. However, as shown in FIG. 1, the separately placed oil tanks are combined into one to provide a single second oil tank 12, and the second oil tank 12 has a capacity equivalent to two. The communication pipe can be omitted.

Next, a specific numerical value of the oil pump pushing pressure will be described.
Tests have shown that the oil pump indentation pressure must be 21 kPa or higher.
Oil pump pushing pressure = oil tank internal pressure + hydraulic pressure due to the weight of the oil itself.
In the case of a turbo chiller for air conditioning, the internal pressure of the oil tank is about 70 kPa, and stable operation of the oil pump is possible without any special measures. Without countermeasures, the hydraulic pressure due to the weight of the oil is 1.4 kPa.
In the case of a low-temperature turbo chiller, the internal pressure of the oil tank is about 14 kPa, so the oil pump cannot be operated stably unless any measures are taken. Therefore, the hydraulic pressure due to the weight of the oil is required to be equal to or larger than the difference between the minimum required pressing pressure (21 kPa) of the oil pump and the internal pressure of the oil tank.
Since the density of the oil used is 0.961 g / cm ³ , it can be said that a pressure of ^{0.961 g / cm 2} acts per 1 cm in height. When this is converted into units, ^{it becomes 0.961 × 10 -3} × 98.0665 = 0.0942 kPa.
Since the liquid pressure due to the weight of the required oil is 21-14 = 7 kPa, the liquid height of the oil required to apply this pressure is 7 ÷ 0.0942 = 74.3 cm. In consideration of safety, when applying to an actual machine, it is desirable to take a height of 30 cm or more plus the required height.
Therefore, the required oil liquid height H = 74.3 + 30 = 104.3 cm or more shown in FIG.

FIG. 3 is a schematic view showing another embodiment of the low temperature turbo chiller according to the present invention. In the embodiment shown in FIG. 3, a branch pipe 21a connected to the gas connecting pipe 25 is provided at a predetermined position of the first oil connecting pipe 21. That is, the branch pipe 21a is branched from a predetermined position of the first oil connecting pipe 21, and the tip of the branch pipe 21a is pointed at the gas discharge port 12b of the second oil tank 12 and the gas inlet 11b of the first oil tank 11. It is connected to the gas connecting pipe 25 for connecting to.
When the refrigerant gas dissolved from the lubricating oil in the first oil connecting pipe 21 is separated from the oil at the time of starting and a refrigerant gas pool is formed in the first oil connecting pipe 21, the first oil tank 11 to the second Since it becomes temporarily difficult to secure continuous oil up to the oil tank 12 of the first oil connecting pipe 21, in order to remove the refrigerant gas pool in the first oil connecting pipe 21, the first oil connecting pipe 21 By providing the branch pipe 21a connected to the gas connecting pipe 25 at a predetermined position, it is possible to solve the problem that the refrigerant gas is accumulated in the first oil connecting pipe 21. As the connection point of the branch pipe 21a, the elbow portion (90 ° bent portion) where gas pools are likely to occur in the first oil connecting pipe 21 is most preferable. A part of the branch pipe 21a (the upper part of the inverted U-shaped tubular branch pipe 21a in the illustrated example) is located at a position higher than the maximum liquid level hmax of the first oil tank 11, and the inside of the branch pipe 21a is filled with oil. Refrigerant gas can easily escape from the branch pipe 21a without being folded.

Further, in the embodiment shown in FIG. 3, the first turbo compressor 1-1 and the second turbo compressors 1-1 and the second are so that the oil level heights of the first oil tank 11 and the third oil tank 13 during operation are the same. The height position of each of the turbo compressors 1-2 is set.
As shown in FIG. 3, an oil heater 27 is provided in each of the first oil tank 11 and the third oil tank 13. If the liquid level of the oil tank during operation of the first turbo compressor 1-1 and the second turbo compressor 1-2 is different, the liquid level becomes lower. The oil heater 27 arranged in the oil tank may be exposed from the oil and become empty-fired. Further, in the oil tank having a higher liquid level, the oil may overflow from the portion where the impeller shaft 28 penetrates the oil tank to the outside of the oil tank. The oil level during operation, which is determined according to the oil tank capacity of the first turbo compressor 1-1 and the second turbo compressor 1-2, is appropriately determined by calculation or experiment, and the determined oil level is determined. By obtaining the mounting position of the compressor in the height direction in advance so that the values are the same and installing the compressor, the oil heater 27 is exposed from the oil due to the difference in the liquid level, and the oil heater 27 is exposed. It is possible to prevent the situation where the 27 is emptied, and it is possible to prevent the oil from overflowing to the outside of the oil tank from the portion where the impeller shaft 28 penetrates the oil tank.

Further, in the embodiment shown in FIG. 3, the first oil connecting pipe 21 and the second oil connecting pipe 22 are connected at a predetermined position. By connecting the first oil connecting pipe 21 and the second oil connecting pipe 22 at a predetermined position in this way, the number of pipes can be reduced and the cost can be reduced. Here, the predetermined position is, for example, a position where the second oil connecting pipe 22 is extended in the horizontal direction and the extended portion collides with the portion extending in the vertical direction of the first oil connecting pipe 21. The predetermined position may be any position as long as the second oil connecting pipe 22 can be connected to the first oil connecting pipe 21 at the shortest distance.
Other configurations of the low-temperature turbo chiller shown in FIG. 3 are the same as those of the low-temperature turbo chiller shown in FIG.

Although the embodiments of the present invention have been described so far, the present invention is not limited to the above-described embodiments, and it goes without saying that the present invention may be implemented in various different forms within the scope of the technical idea.

1-1 First turbo compressor 1-2 Second turbo compressor 2 Condenser 3 Evaporator 4 Economizer 5 Coolant piping 11 First oil tank 11a Oil outlet 11b Gas inlet 12 Second oil tank 12a Oil inlet 12b Gas outlet 13 Third oil tank 21 First oil connecting pipe 21a Branch pipe 22 Second oil connecting pipe 25 Gas connecting pipe 26 Connecting pipe 27 Oil heater 28 Impeller shaft 30 Refueling pipe 31 First Oil pump 32 Second oil pump

Claims (7)

In a low-temperature turbo chiller equipped with multiple compressors that compress refrigerant gas in multiple stages,
The first compressor and
The first oil tank built in the first compressor and
A second oil tank disposed below the first oil tank and configured to be constantly filled with lubricating oil.
The first oil pump arranged in the second oil tank and
It is provided with a first oil connecting pipe connecting the oil outlet of the first oil tank and the oil inlet of the second oil tank.
The oil inlet of the second oil tank is provided at a position below the oil discharge port of the first oil tank and at a position where the suction pressure required for the first oil pump or higher can be secured.
It said first oil communication pipe is state, and are continuous over the channel cross-sectional area can be secured for the oil without interruption oil,
A low-temperature turbo chiller provided with a gas connecting pipe connecting the gas outlet of the second oil tank and the gas inlet of the first oil tank. The gas connection pipe is cold turbo refrigerator according to claim 1, wherein the discharge of the refrigerant gas is capable flow path cross-sectional area than that dissolved in the oil at startup. The low-temperature turbo chiller according to claim 1 or 2 , wherein the gas connecting pipe is connected to a position above the maximum liquid level of the first oil tank. The low-temperature turbo chiller according to claim 1 or 2 , wherein a branch pipe connected to the gas connecting pipe is provided at a predetermined position of the first oil connecting pipe. With the second compressor,
A third oil tank built in the second compressor and
A second oil pump arranged in the second oil tank and
Further provided with a second oil connecting pipe connecting the oil outlet of the third oil tank and the oil inlet of the second oil tank.
The low-temperature turbo chiller according to claim 1, wherein the second oil tank is arranged below the first oil tank and the third oil tank. The height positions of the first compressor and the second compressor are set so that the oil level heights of the first oil tank and the third oil tank during operation are the same. The low-temperature turbo chiller according to claim 5 , wherein the low-temperature turbo chiller is provided. The low-temperature turbo chiller according to claim 5 or 6, wherein the first oil connecting pipe and the second oil connecting pipe are connected at a predetermined position.

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