JPH03213960A - Oil recovery device for closed type turbo freezer - Google Patents

Abstract

PURPOSE:To prevent a hydraulic reduction trip caused by a lack of oil and enable a continuous operation to be carried out by a method wherein when the times per unit hour of an automatic starting and stopping of a compressor is more than a set number of times, it is controlled to restrict the degree of opening of a suction volume control valve of the compressor less than the specified value. CONSTITUTION:As the number of times of starting or stopping of a compressor 2 within a specified time are detected and are more than a set value, a degree of opening of a suction volume control valve 3 of the compressor 2 is restricted to a value less than a specified degree of opening. The degree of opening is a differential pressure across the volume control valve 3 sufficient for sucking the refrigerant liquid from an evaporator 1 and then it can be determined under a trial operation. Due to this fact, the differential pressure of the control valve 3 is sufficient for sucking the refrigerant liquid and its operating time is extended, so that the oil accumulated in the evaporator 1 is sufficiently recovered and the trial operation can be carried out without causing any hydraulic pressure reduction trip under a lack of oil.

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, evaporated refrigerant gas A is 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 bearing of the impeller 6 of the compressor 2, the speed increasing gear 7, etc. are lubricated by a separate lubricating 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 the evaporator 1 is also carried out. 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 sucked by an ejector 11 or the like and collected into an oil tank 13.

In addition, in FIG. 2, 9 is the main motor of the compressor 2, and 14 is the main motor of the compressor 2.
．． 15 are 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
20 is a purge condenser, 20 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, and a low oil pressure trip is activated, causing the refrigerator to stop.

In this way, in order to continue operating the refrigerator without interruption, it was necessary to replenish the lubricating device with oil.

Next, when the load increases and full-load operation becomes possible, the oil recovery function due to the refrigerant gas is restored, causing the oil level in the oil tank to rise, making it necessary for the driver to remove the oil from the oil tank. It was very troublesome for me.

Further, there is a problem in that the concentration of oil dissolved in the refrigerant liquid becomes high for the evaporator 1, promoting fouling of the tubes and inhibiting heat transfer.

In order to prevent this, the suction capacity control valve 3 is closed during partial load operation, and by utilizing the difference in pressure that occurs before and after the valve, the refrigerant liquid containing dissolved oil is removed from the evaporator 1. There is a valve downstream of the suction capacity control valve 3 that has a function of recovering the drawn oil. However, even with a turbo chiller equipped with such a function, when the refrigeration load becomes small and the compressor 2 is turned on and off, the chilled water temperature rises in the OFF state, and when the compressor 2 is turned ON, the conventional method For the time being, the suction capacity control valve 3 is fully open because the chilled water temperature is high.

However, since the load is originally small, the chilled water temperature drops in a short time and the compressor 2 is turned off. Therefore, if this frequency of start and stop is high, even if an attempt is made to perform the oil recovery function by drawing in the refrigerant liquid containing dissolved oil using the differential pressure of the suction capacity control valve 3, the operating time is insufficient. There was a problem that I couldn't get it.

Further, in the lubricating system, the oil pump normally remains in operation for a certain period of time after the compressor 2 is stopped, and in this case, leakage of oil to the refrigerant side occurs even while the compressor 2 is stopped. Therefore, the problem that oil accumulates in the evaporator 1 and is not collected in the oil tank has not been completely solved.

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

[Means to solve the problem]

In order to solve the above problems, the present invention provides that the compressor 2 is equipped with a suction capacity control valve 3, and the refrigerant liquid containing dissolved oil is transferred from the evaporator 1 to the suction capacity using the differential pressure across the suction capacity control valve 3. In a hermetic centrifugal chiller that is equipped with a mechanism to collect oil drawn downstream of the control valve 3 and has a control mechanism that automatically starts and stops the compressor 2 depending on the magnitude of the load, the unit time for automatically starting and stopping the compressor 2 When the number of hits exceeds the predetermined set number of times,
The compressor is characterized by being equipped with a suction capacity control valve opening degree control means that reduces the frequency of starting and stopping by suppressing the opening degree of the suction capacity control valve 3 of the compressor 2 below a certain value.

Further, the suction capacity control valve opening control means controls the current value of the main motor 9 of the compressor 2 by a current limiting mechanism so that the current value of the main motor 9 does not exceed a certain value. The invention is characterized in that it is a means for reducing the frequency of starts and stops by suppressing the opening degree of the suction capacity control valve 3 by suppressing the opening degree of the suction capacity control valve 3 below a certain value or by increasing the chilled water control temperature of the refrigerator. .

[Effect]

In a centrifugal chiller, the control mechanism of the suction capacity control valve 3 such as a suction vane is insufficient to adjust the reduction in the refrigeration load, so the compressor 2 is turned on by an automatic start/stop thermostat installed at the chilled water inlet 14. , is turned off. When the refrigeration load is small, the cold water is easily cooled and returns to a low temperature, so that the cold water inlet temperature also decreases by operating the compressor 2 for a short time. Therefore, the frequency of turning on and off the compressor 2 increases.

According to the present invention, the number of ON and OFF operations in a certain period of time is detected, and when this becomes equal to or greater than a set value, the opening degree of the suction capacity control valve 30 of the compressor 2 is suppressed to a certain degree of opening or less. The value of the opening degree is such that a pressure difference across the capacity valve section sufficient to suck refrigerant liquid from the evaporator 1 can be obtained, but the value can be determined by a trial run. Therefore, the differential pressure across the suction capacity control valve 3 is a value sufficient to suck the refrigerant liquid, and the operating time is increased, so that the oil accumulated in the evaporator 1 is sufficiently recovered.

Further, the main motor 9 for driving the compressor 2 is generally equipped with a current limiting mechanism to protect the motor. By controlling the current value of the main motor 9 so as not to exceed a certain value, the opening degree of the suction capacity control valve 30 can be easily suppressed.

Further, the opening degree of the suction capacity control valve 3 can also be suppressed by temporarily increasing the cold water control temperature.

〔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 n of operation of compressor 2, that is, the number of ONNs per unit time of compression@2 during automatic operation (step 10).
1). Next, the color of the ONN number per unit time of the compressor 2, which is the reference color, is compared (step 102), and then it is determined whether n>N (step 103), YES. Then, the suction capacity control valve 3 is stopped at a constant value (step 104). It is determined whether or not this state has passed once (step 106), and if YES, the restriction in step 104 is canceled and the restriction in step 1 is
Return to 01. Note that in step 103, NO1, that is, n
>N, the process returns to step 101.

If the answer is YES in step 103, the current value of the main motor 9 may be held constant (step 108) or the cold water control temperature may be increased (step 10).
9) There is also a method.

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 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...Main motor.

Claims (3)

[Claims] (1) The compressor is equipped with a suction capacity control valve, and a mechanism is provided for drawing refrigerant liquid containing dissolved oil from the evaporator downstream of the suction capacity control valve and recovering the oil by using the differential pressure across the suction capacity control valve. In a hermetic centrifugal chiller equipped with a control mechanism that automatically starts and stops the compressor depending on the magnitude of load, when the number of times the compressor automatically starts and stops per unit time exceeds a predetermined set number of times, An oil recovery device for a hermetic centrifugal chiller, comprising: a suction capacity control valve opening control means for suppressing the opening of the suction capacity control valve of the compressor below a certain value. (2) The suction capacity control valve opening control means controls the opening of the suction capacity control valve by controlling the main motor current value of the compressor so as not to exceed a certain value using a current limiting mechanism for the main motor current of the compressor. The oil recovery device for a hermetic centrifugal chiller according to claim 1, characterized in that the oil recovery device is a means for suppressing the temperature below a certain value. (3) Claim (1) characterized in that the suction capacity control valve opening degree control means is a means for suppressing the opening degree of the suction capacity control valve by increasing the chilled water control temperature of the refrigerator.
) Oil recovery device for a hermetic centrifugal chiller.