JPH03213959A - Oil recovery device in closed type turbo freezer - Google Patents

Abstract

PURPOSE:To reduce an amount of oil left in an evaporator and eliminate a lack of lubricant oil by a method wherein as the time of automatic starting and stopping of a compressor per hour is more than a set number of times, a suction volume control valve is forcedly kept by more than a specified period of time and by more than a specified degree of opening. CONSTITUTION:Under a partial loading state in which a repetition of turning-on or -off of a compressor 2 is high, as the number of times of turning-on or -off per specified time becomes more than the set value, a degree of opening of a suction volume control valve 3 of the compressor 2 is forcedly opened by more than a specified value for a specified period of time. The specified value in this case is defined as a value in which a flow rate of refrigerant gas is sufficient for accompanying the refrigerant liquid. Due to this fact, oil accumulated in the evaporator 1 is accompanied by the refrigerant gas and recovered. A gas bypassing valve 10 for carrying out a bypassing of refrigerant gas from the condenser 4 to the evaporator 1 is opened by a specified degree of opening, thereby the compressor 2 shows a higher load than the normal partial load and then the control valve 3 can be forcedly opened to a specified value and its operation can be kept. Accordingly, a lack of lubricant oil is eliminated and the continuous operation can be carried out.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hermetic centrifugal chiller that effectively recovers lubricating oil leaked into the refrigerant even when the refrigeration load is small. This relates to oil recovery equipment.

[Prior art]

The refrigeration cycle of a hermetic centrifugal refrigerator will be explained with reference to FIG.

In the evaporator 1, the evaporated refrigerant gas A can be sucked into the compressor 2. The amount of suction gas is adjusted by a suction capacity control valve 3, such as a sink vane, depending on the refrigeration load. The refrigerant gas compressed by the compressor 2 is transferred to the condenser 4
It is discharged into a refrigerant liquid through cooling and condensation. This refrigerant liquid returns to the evaporator 1 through an expansion mechanism 5 such as an orifice.

Here, the bearings of the impeller 6 of the compressor 20, the speed increasing gear 7, etc. are lubricated by a separate lubrication system (not shown).

In a hermetic centrifugal refrigerator, the refrigerant system and the lubrication system are completely isolated from the outside, and although they are separated by a sealing device, there is a small amount of traffic between them. Generally, oil leaks into the refrigerant side from the shaft penetrating portion of the compressor 2 as shown in B. This oil reaches the evaporator 1 through the condenser 4 together with the refrigerant gas. In the evaporator 1, the refrigerant evaporates leaving behind oil, so the oil accumulates here.

However, since refrigerant mist is usually sucked into the compressor 2 along with the refrigerant gas evaporated in the evaporator 1, the oil is eventually dissolved in this mist and completely carried out from the evaporator 1. As shown in FIG. 3, there is an oil reservoir 8 on the suction side of the compressor 2.
The oil accumulated in the oil reservoir 8 is removed from the ejector filter 1.
2 and is sucked by the ejector 11 etc. into the oil tank 1.
Collected to 3.

In addition, in FIG. 2, 9 is a bypass passage that bypasses a part of the refrigerant gas that has flowed into the condenser 4 from the compressor 2 to the evaporator 1, and the bypass passage 9 is provided with a hot gas bypass valve 10. There is. Further, 14 and 15 are the cold water inlets of the evaporator 1, respectively.

The cold water outlet 16 and 17 are the cooling water inlet and the cooling water outlet of the condenser 4, respectively. Also, 18 is an oil cooler, 19
2o is a purge condenser, 2o is a refrigerant pump, 21 is a strainer, and 22 is a refrigerant cooler.

[Problem to be solved by the invention]

In the conventional hermetic centrifugal refrigerator described above, under full load or similar load conditions, the flow rate of refrigerant gas is high, so a required amount of refrigerant mist is entrained, and sufficient oil is recovered.

However, in a partial load state, the amount of refrigerant mist accompanying the refrigerant gas is small, so the amount of oil recovered is less than the amount of leakage, and the amount of oil dissolved in the refrigerant and remaining in the evaporator 1 increases.

As a result, the oil in the lubricating system decreases, causing the oil pressure drop knob to operate and the refrigerator to stop.

Therefore, in order to continue operating the refrigerator, the lubricating system must be refilled with oil, which not only wastes oil, but also prevents the refrigerating machine from operating at full load the next time it is possible to operate at full load.
Since more oil can be recovered, the oil level in the oil tank becomes higher.
On the other hand, it is necessary to drain the oil from the oil tank, which is very troublesome for the driver.

Furthermore, if the evaporator 1 continues to operate in a partial load state, the concentration of oil dissolved in the refrigerant liquid increases, which promotes fouling of the tubes and impedes heat transfer.

The present invention has been made in view of the above-mentioned points, and is an oil recovery device for a hermetic centrifugal chiller that eliminates the above-mentioned problems and effectively recovers lubricating oil leaked into the refrigerant even when the refrigeration load is nagging. The purpose is to provide

[Means to solve the problem]

In order to solve the above problems, the present invention provides a compressor 2 equipped with a suction capacity control valve 3, an oil sump chamber 8 on the suction side of the compressor 112, and a suction device to drain the oil accumulated in the oil sump chamber into an oil tank. In a hermetic centrifugal chiller that is equipped with a recovery mechanism and has a mechanism that automatically starts and stops the compressor 2 depending on the magnitude of the load, the number of times per unit time that the compressor 2 automatically starts and stops exceeds a predetermined set number of times. The present invention is characterized in that means is provided for forcibly maintaining the suction capacity control valve 3 of the compressor 2 at a predetermined opening degree or more for a predetermined period of time or more when this occurs.

In addition, when the suction capacity control valve 3 of the compressor 2 is forcibly maintained at a certain opening degree or more for a certain period of time or more, the compressor 2
The hot gas bypass valve 10 provided in the bypass passage 9 that bypasses a part of the refrigerant gas that has flowed into the condenser 4 from the evaporator 1 to the evaporator 1 is opened.

Since the control mechanism of the suction capacity control valve 3 such as John Vane is insufficient for adjustment, the compressor 2 is turned on and off by an automatic start/stop thermostat installed at the cold water inlet 14. When the refrigeration load is small, the cold water is easily cooled down and returns to a low temperature, so the cold water inlet temperature also decreases by operating the compressor 2 for a short time. Therefore, compressor 2 is ON, 0FFJI
The degree becomes higher.

According to the present invention, the number of ON and OFF operations in a certain period of time is detected, and when this becomes a set value or more, the opening degree of the suction capacity control valve 3 of the compressor 2 is forcibly maintained at a certain value or more for a certain period of time or more. Here, the constant value is an opening degree such that the refrigerant gas flow rate becomes a value sufficient to accompany the refrigerant liquid, and can be determined by a trial run. By doing this, the operating time of the compressor 2 is shortened because the refrigerating capacity becomes larger than necessary, but the flow rate of the refrigerant gas becomes sufficient to entrain the refrigerant liquid, so the evaporator The oil accumulated in 1 is collected. The operating time of the compressor 2 will be long enough for oil recovery if the compressor 2 is operated until the suction pressure of the compressor 2 decreases or before the refrigerant low temperature trip or the chilled water low temperature trip occurs.

By opening to a certain degree, the load on the compressor 2 becomes larger than the normal partial load, which goes against the energy-saving operation of the compressor 2, but it is possible to force the suction capacity control valve 3 to a constant value in a stable manner. It can also be opened and maintained.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a flowchart showing the operation of the oil recovery device for a hermetic centrifugal refrigerator according to the present invention. The configuration of the hermetic centrifugal refrigerator of the oil recovery apparatus of this embodiment is the same as that shown in FIG. 2.

In FIG. 1, first, the hermetic centrifugal refrigerator is operated,
Count the number of times the compressor 2 is operated, that is, the number of times the compressor 2 is turned on per unit time during automatic operation (step 10).
1). Next, compare the number of ON times n per unit time with the number of ON times per unit time of the compressor 2 as a reference (Step 1o2), and then judge whether n>N (Step 1゜3). , if YES, the suction capacity control valve 3 is opened to a certain value (step 104), it is determined whether or not T has passed through this state (step 106), and if YES, the suction capacity control valve 3 is closed (step 106). Step 107), returning to step 101 above. Incidentally, if NO1 is determined in step 103, that is, n>N, the process returns to step 101.

Further, if YES in step 103, the hot gas bypass valve 10 is opened at a constant opening (step 1
08) There is also a method, but in this case, after step 107,
Close the hot gas bypass valve 10 (step 109)
.

The above operation can also be realized by a control means using a microcomputer, for example.

〔Effect of the invention〕

As explained above, according to the present invention, the following excellent effects can be obtained.

(1) Even if partial load operation with a small amount of oil recovery continues, continuous operation of the hermetic centrifugal chiller is possible without causing oil pressure drop trips due to oil shortage.

(2) There is no need for troublesome operations such as replenishing oil and draining oil from the oil tank in order to continue operation.

(3) Since it is possible to suppress the concentration of oil dissolved in the refrigerant liquid of the evaporator from increasing, it is possible to prevent contamination of the heat transfer tubes, maintain good heat transfer, and save energy.

[Brief explanation of drawings]

Fig. 1 is a flowchart showing the operation of the oil recovery device for a hermetic centrifugal chiller according to the present invention, Fig. 2 is a diagram showing the configuration of the hermetic centrifugal chiller, and Fig. 3 is a diagram showing the configuration of the oil recovery device for the compressor. FIG. In the figure, 1... evaporator, 2... compressor, 3...
・Suction capacity control valve, 4... Condenser, 5... Expansion mechanism, 6... Impeller, 7... Speed increasing gear, 8...
...Oil sump, 9..Bypass path, 10..Hot gas bypass valve.

Claims (2)

[Claims] (1) The compressor is equipped with a suction capacity control valve, has an oil sump chamber on the suction side of the compressor, and is equipped with a recovery mechanism that collects the oil accumulated in the oil sump chamber into an oil tank using a suction device, and is equipped with a In a hermetic centrifugal chiller that has a mechanism that automatically starts and stops the compressor according to An oil recovery device for a hermetic centrifugal chiller, comprising means for forcibly maintaining a control valve at a predetermined opening for a predetermined period of time or more. (2) A bypass path that bypasses a portion of the refrigerant gas flowing from the compressor into the condenser to the evaporator when the suction capacity control valve of the compressor is forcibly maintained at a certain opening degree or more for a certain period of time or more. 2. The oil recovery device for a hermetic centrifugal chiller according to claim 1, wherein a hot gas bypass valve provided at the hot gas bypass valve is opened.