JP2006313044A - Screw refrigerating unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw refrigerating unit capable of sufficiently sealing, cooling and lubricating a screw compressor with a simple structure. <P>SOLUTION: This screw refrigerating unit 1 is provided with: a circulation passage I composed of the screw compressor 2, a condenser 3, a main expansion valve 4 and an evaporator 5 for circulating a refrigerant containing lubrication oil of a quantity for stopping the degradation of heat transmission efficiency in the condenser 3 and the evaporator 5 to a practically negligible level; a lubricating passage II branched from the circulation passage I between the screw compressor 2 and the condenser 3 for introducing the refrigerant to bearing parts 7a and 7b of the screw compressor 2; and a cooling passage III branched from the circulation passage I between the condenser 3 and the main expansion valve 4 for introducing the refrigerant into a rotor chamber 6 of the screw compressor 2 through a restriction means 10 for regulating the flow rate of the refrigerant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a screw refrigeration apparatus using a screw compressor.

  2. Description of the Related Art Conventionally, a screw refrigeration apparatus is known in which a circulation channel is configured by a screw compressor, a condenser, a main expansion valve, and an evaporator.

  In a conventional screw compressor, oil is injected into the rotor chamber for the purpose of sealing between the rotors and between the rotor and the inner wall surface of the rotor chamber, cooling of the temperature rising portion accompanying compression, and lubrication. For this reason, the complicated accessory equipment for separating and cooling oil from the discharge gas of a screw compressor, and inject | pouring into a rotor chamber again was required.

As a screw refrigeration apparatus that does not require such complicated accessory equipment, Patent Document 1 discloses a screw refrigeration apparatus 21 as shown in FIG. The screw refrigeration apparatus 21 includes a screw compressor 22, a condenser 23, an expansion valve 24, and an evaporator 25 having a rotor chamber (not shown) that rotatably accommodates a pair of male and female screw rotors that mesh with each other, and circulates a refrigerant. A circulation flow path IV and a bypass flow path V branching from the circulation flow path IV between the condenser 23 and the expansion valve 24 and introducing the refrigerant into the screw compressor 22 via the throttle means 26 are provided.
JP 2004-205195 A

  In the screw refrigeration apparatus 21, the refrigerant branched into the bypass flow path V is partially vaporized in the process of passing through the throttle means 26, becomes a gas-liquid mixed state, and is introduced into the rotor chamber in the screw compressor 22. . The liquid state refrigerant seals and lubricates between the rotors and the rotor and the inner wall of the rotor chamber, and the liquid state and gas state refrigerants particularly from the surroundings when the liquid state refrigerant evaporates. Due to the action of depriving the heat of vaporization, the temperature raising part accompanying the compression operation of the refrigerant in the rotor chamber is cooled.

  Patent Document 1 describes that a part of the refrigerant may be introduced from the bypass channel V into the bearing portion for fluid lubrication of the bearing of the screw compressor 22. Furthermore, Patent Document 1 discloses that the refrigerant includes an amount of lubricating oil within a range that stops the decrease in heat transfer efficiency in the condenser 23 and the evaporator 25, which are a kind of heat exchanger, from a practical level. It is described that a slight amount of lubricating oil of about 1 to 3% by weight may be mixed.

  The screw refrigeration apparatus 21 described in Patent Document 1 is very useful because it has the effect of simplifying the structure of the entire apparatus, reducing the size, and reducing the maintenance burden. Since the lubricating oil in the refrigerant adheres to the inner wall of the rotor chamber, the rotor surface and the bearing to form a lubricating oil film, the effect of sealing and lubrication can be enhanced. However, the liquid refrigerant introduced from the bypass channel V also has an action of washing away the lubricating oil film formed on the bearing. Therefore, even if a small amount of lubricating oil is mixed in the refrigerant, the life of the bearing may not be sufficiently extended.

  In view of the above problems, an object of the present invention is to provide a screw refrigeration apparatus that can sufficiently seal, cool, and lubricate a screw compressor with a simple structure.

  In order to solve the above problems, a screw refrigeration apparatus according to the present invention includes a screw compressor, a condenser, a main expansion valve, and an evaporator, and a circulation flow path for circulating a refrigerant containing lubricating oil, and the screw compression. A lubrication channel that branches from the circulation channel between the compressor and the condenser and introduces the refrigerant into a bearing portion in the screw compressor; and from the circulation channel between the condenser and the main expansion valve A cooling flow path is provided that branches and introduces the refrigerant into a rotor chamber in the screw compressor via a throttle means.

  According to this configuration, a part of the gas-phase refrigerant immediately after being discharged from the screw compressor is branched and introduced into the bearing portion in the screw compressor where cooling is not necessary, so that the lubricating oil in the refrigerant gas can be removed. The bearing can be lubricated by the oil film formed by adhering to the surface of the bearing, and since the liquid phase refrigerant is not introduced, the oil film once formed is not washed away. In addition, in the rotor chamber where the necessity of cooling is high, a part of the refrigerant in the liquid layer cooled by the condenser is branched to introduce the refrigerant in the gas-liquid mixed state. It can be cooled sufficiently.

  Further, in the screw refrigeration apparatus of the present invention, the amount of the lubricating oil may be an amount that stops a decrease in heat transfer efficiency of the refrigerant in the condenser and the evaporator so that it can be practically ignored.

  The above-described bearing can be sufficiently lubricated without hindering the functions of the condenser and evaporator as the heat exchanger, and the screw compressor can be sufficiently cooled.

  In the screw refrigeration apparatus of the present invention, the throttle means is not less than a saturation temperature (condensation temperature or evaporation temperature) of the refrigerant at a discharge pressure set by a discharge temperature of the screw compressor and not more than the saturation temperature + 10 ° C. The opening may be controlled so that

  According to this configuration, the refrigerant introduced into the bearing portion of the screw compressor is kept in a low temperature range that does not include a liquid phase and has no risk of overheating of the bearing.

  Further, in the screw refrigeration apparatus of the present invention, the lubricating flow path is a flow for introducing the lubricating oil separated from the refrigerant by the gas-liquid separator provided at the branching point into the bearing portion along with the refrigerant. It may be a road. Preferably, the gas-liquid separator is a cyclone separator that separates the lubricating oil from the refrigerant by centrifugal force.

  According to this structure, the refrigerant | coolant containing more lubricating oil than the refrigerant | coolant of a circulation flow path or a cooling branch path can be supplied to the bearing of a screw compressor, and lubrication of a bearing is reliable.

  According to the present invention, a gas-phase refrigerant containing lubricating oil can be introduced into the bearing to reliably lubricate the screw compressor, and a liquid-phase refrigerant can be introduced into the rotor chamber to reliably cool the screw compressor. .

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 is a flow sheet of a screw refrigeration apparatus 1 according to a first embodiment of the present invention. The screw refrigeration apparatus 1 includes a circulation flow path I in which a screw compressor 2, a condenser 3, a main expansion valve 4, and an evaporator 5 are connected in an annular shape. The screw compressor 2 includes a rotor chamber 6 including a pair of male and female screw rotors, and bearing portions 7a and 7b that receive bearings that rotatably support the screw rotor, and includes a motor 8 that drives the screw rotor. . Further, the screw refrigeration apparatus 1 further includes a lubrication flow path II branched from the circulation flow path I between the screw compressor 2 and the condenser 3 and connected to the bearing portions 7a and 7b via the control valve 9, and a condensation A cooling flow path III branched from the circulation flow path I between the container 3 and the main expansion valve 4 and connected to the rotor chamber 6 via the throttle valve 10. Further, the screw refrigeration apparatus 1 is provided with a temperature sensor 11 in the circulation flow path I immediately after the discharge of the screw compressor 2, and the temperature of the refrigerant discharged from the screw compressor 2 is saturated when the temperature is equal to or higher than the saturation temperature at the discharge pressure. The opening degree of the throttle valve 10 is adjusted so that the temperature becomes 10 ° C. or lower.

Then, the effect | action of the screw refrigeration apparatus 1 by the above structure is demonstrated.
When the discharge temperature of the screw compressor 2 rises, the screw refrigeration apparatus 1 increases the opening degree of the throttle valve 10 and introduces a large amount of low-temperature refrigerant into the rotor chamber 6 from the cooling flow path III to cool the rotor chamber 6. To do. On the contrary, when the discharge temperature of the screw compressor 2 is lowered, the opening degree of the throttle valve 10 is reduced, and the refrigerant introduced into the rotor chamber 6 from the cooling flow path III is reduced to suppress the cooling effect. For this reason, since the discharge temperature of the screw compressor 2 is controlled between the saturation temperature and the saturation temperature + 10 ° C., the refrigerant branched into the lubrication flow path II is always in the gas phase, but is changed to an excessively high temperature gas. Must not. Moreover, the refrigerant | coolant enclosed with the screw cooling device 1 is the lubricating oil in the range which stops the fall of the heat transfer efficiency of the refrigerant | coolant in the condenser 3 and the evaporator 5 which are 1 type of heat exchangers to the extent which can be disregarded practically, That is, it contains a slight amount of about 0.5 to 3% by weight, for example, 2% by weight of lubricating oil with respect to the refrigerant. For this reason, when the gas-phase refrigerant branched into the lubrication flow path II is introduced into the bearing portions 7a and 7b of the screw compressor 2, oil droplets (mist) of lubricating oil contained in the refrigerant adhere to the bearing. Then, a lubricating film (oil film) that lubricates the bearing is formed. When the liquid phase refrigerant is introduced into the bearing portions 7a and 7b, the lubricating film once formed is washed away, but since the gas phase refrigerant is always supplied from the lubricating flow path II, a good lubricating film is maintained. Is done. For this reason, the bearing is sufficiently lubricated and has a long life. Further, since the refrigerant supplied from the lubrication flow path II is controlled to the saturation temperature + 10 ° C. or less, there is no fear that the bearing is overheated and seized.

  On the other hand, the rotor chamber 6 of the screw compressor 2 needs to be lubricated and sealed, and needs to be cooled so that the screw rotor and the rotor chamber 6 are not heated too much due to a temperature rise due to adiabatic compression of the refrigerant. The refrigerant supplied to the rotor chamber 6 from the cooling channel III is a gas-liquid mixed state refrigerant in which the flow rate of the liquid phase refrigerant branched from the circulation channel I after being cooled by the condenser 3 is controlled by the throttle valve 10. . The liquid phase refrigerant absorbs the heat in the rotor chamber 6 and vaporizes it, so that a lot of heat is taken and the rotor chamber 6 can be efficiently cooled. In the rotor chamber 6, the liquid-phase refrigerant is also immediately vaporized, so that the lubricating oil in the refrigerant forms a lubricating film on the rotor surface and the inner wall of the rotor chamber 6. Although the lubricating film formed by the liquid-phase refrigerant may be washed away, the requirement for lubrication is not as strict as the bearing, so that problems due to poor lubrication are less likely to occur.

  As described above, in this embodiment, good cooling and good lubrication of the screw compressor 2 are realized with a simple configuration, and the equipment is inexpensive and has a long life.

Then, the flow sheet of screw refrigeration apparatus 1 'of 2nd Embodiment of this invention is shown in FIG.
This embodiment is a kind of a gas-liquid separator that separates mist-like lubricating oil in the refrigerant at the branch point between the circulation flow path I and the lubricating flow path II, and separates the lubricating oil using centrifugal force. This is different from the first embodiment in that a cyclone separator 12 is provided.

  FIG. 3 shows a horizontal section of the cyclone separator 12 and will be described in detail. The cyclone separator 12 is composed of a pipe having a diameter of 150A and a length of 700 mm, which is installed vertically, for example, an outer tube 12a sealed at both ends with a plate, and a pipe having a diameter of 40A, for example, and one end of the outer tube 12a. An introduction tube 12b that opens to the inside of the outer tube 12a in a tangential direction along the inner wall, and an outer tube that passes through the sealed upper end of the outer tube 12a and has one end opened downward in the middle of the outer tube 12a. The inner pipe 12c is made of a pipe having the same diameter as the introduction pipe 12b, for example, concentric with 12a, and flanges 12d are provided on the outer ends of the introduction pipe 12b and the inner pipe 12c, respectively. The introduction pipe 12b is connected to the upstream side of the circulation flow path I, that is, the discharge pipe of the screw compressor 2, and the inner pipe 12c is connected to the downstream side of the circulation flow path I, that is, the condenser 3 by the flange 12d. Connected pipes are connected. And the drain flow path which draws out the lubricating oil isolate | separated from the lower end of the cyclone separator 12 with refrigerant gas is the lubrication flow path II connected to the bearing parts 7a and 7b of the screw compressor 2 via the control valve 9. .

  In the screw refrigerator 1 ′, for example, a refrigerant containing about 0.5% by weight of lubricating oil as a whole system is enclosed. In the screw refrigerator 1 ′, since the lubricating oil is separated by the cyclone separator 12, the refrigerant in the lubricating flow path II, which is the drain flow path of the cyclone separator 12, uses 2% by weight or more of the lubricating oil as in the first embodiment. Accompanying. By introducing the refrigerant into the bearing portions 7a and 7b, a lubricating film is formed on the bearing by the lubricating oil in the refrigerant to lubricate the bearing. Only in the circulation channel II, even if the thermal characteristics of the refrigerant due to the lubricating oil are impaired, the overall capacity of the screw refrigeration apparatus 1 ′ is not affected, so that only a small amount of refrigerant comes out of the inner pipe 12c of the cyclone separator 12. The refrigerant in the circulation channel II may contain a larger amount of lubricating oil while containing only the lubricating oil. Since the screw refrigerator 1 ′ has a small amount of lubricating oil circulating through the circulation flow path I, there is no concern that the thermal efficiency of the refrigerant is reduced by the lubricating oil, and the refrigerant in the circulation flow path II contains a large amount of lubricating oil. The risk that the lubricating oil in the bearing portions 7a and 7b is insufficient due to adhesion of the lubricating oil to the pipe wall is small.

The flow sheet of the screw refrigeration apparatus of a 1st embodiment of the present invention. The flow sheet of the screw refrigeration apparatus of the second embodiment of the present invention. Sectional drawing of the cyclone separator of the screw refrigeration apparatus of FIG. A flow sheet of a known screw refrigeration apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw refrigeration apparatus 1 'Screw refrigeration apparatus 2 Screw compressor 3 Condenser 4 Main expansion valve 5 Evaporator 6 Rotor chamber 7a Bearing part 7b Bearing part 8 Motor 9 Control valve 10 Throttle valve (throttle means)
11 Temperature sensor 12 Cyclone separator (gas-liquid separator)
I Circulation channel
II Branch channel
III Cooling channel

Claims (4)

A circulation passage through which a screw compressor, a condenser, a main expansion valve and an evaporator are interposed to circulate a refrigerant containing lubricating oil;
A lubrication flow path that branches from the circulation flow path between the screw compressor and the condenser and introduces the refrigerant into a bearing portion in the screw compressor;
A screw refrigeration comprising: a cooling channel that branches from the circulation channel between the condenser and the main expansion valve and introduces the refrigerant into a rotor chamber in the screw compressor through a throttle means. apparatus.   The screw refrigeration apparatus according to claim 1, wherein the amount of the lubricating oil is an amount that stops a decrease in heat transfer efficiency of the refrigerant in the condenser and the evaporator to a level that can be practically ignored.   The opening degree of the throttle means is controlled so that the discharge temperature of the screw compressor is equal to or higher than a saturation temperature of the refrigerant at a set discharge pressure and equal to or lower than the saturation temperature + 10 ° C. Item 3. A screw refrigeration apparatus according to item 1 or 2.   The lubrication flow path is a flow path for introducing lubricating oil separated from the refrigerant by a gas-liquid separator provided at a branch point into the bearing portion in association with the refrigerant. The screw refrigeration apparatus in any one of 1-3.

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