JPH0381064B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for controlling an auxiliary cold source for a cryogenic refrigerator that uses liquid nitrogen or the like as an auxiliary cold source.

[Background of the invention]

In cryogenic refrigeration equipment that uses helium gas, argon gas, etc. as a refrigerant to generate a cryogenic refrigerant of the gas (in the case of helium gas, for example, cryogenic helium gas of 20K or liquid helium of 4K or less), The energy efficiency of the device has been improved by using liquid nitrogen as an auxiliary cooling source. Therefore, it is important to appropriately control the supply amount of the auxiliary cold source in order to maintain the capacity of the apparatus and also maintain the energy efficiency of the apparatus at an optimum level.

Hereinafter, a helium liquefaction refrigeration system will be explained as an example. FIG. 1 is a block diagram showing an example of a configuration for controlling an auxiliary cold source of a conventional helium liquefaction refrigeration system. In FIG. 1, 1 is a compressor unit, 2 is a medium pressure tank, 3a and 3b are pressure control valves, 5 is a high pressure refrigerant gas inlet pipe, 6 is a low pressure refrigerant gas outlet pipe, 7 is a temperature controller, and 8a ~8c is a flow control valve, 9 is a cold box, 10a~10e
is a heat exchanger, 12a and 12b are expanders, and 14 is an object to be cooled.

Next, the operation of the conventional helium liquefaction refrigeration system configured as described above will be described. The high-pressure refrigerant gas compressed by the compressor unit 1 is introduced into the cold box 9 through the introduction pipe 5, cooled by liquid nitrogen and low-pressure refrigerant gas in the first heat exchanger 10a, and then transferred to the liquefaction line and expansion line. Branch to machine line. The high-pressure refrigerant gas branched into the expander line is
After generating cold by performing adiabatic expansion work in the first expander 12a, the third heat exchanger 10
The temperature is further lowered by exchanging heat with the low-pressure refrigerant gas at c, and the second expander 12b performs adiabatic expansion work again to generate refrigeration, which joins the low-pressure line. The high-pressure refrigerant gas branched to the liquefaction line is
~After exchanging heat with the low-pressure refrigerant gas in the fifth heat exchangers 10b to 10e and finally cooling to below the reversal temperature, cryogenic refrigerant is generated by performing Joel-Thompson expansion with the flow control valve 8c. Cooled object 1
Sent to 4. The cryogenic refrigerant that has absorbed the heat load in the object to be cooled 14 returns to the cold box 9, and returns to the compressor unit 1 after recovering the cooled state by exchanging heat with the heat exchangers 10e to 10a.

On the other hand, liquid nitrogen, which is an auxiliary cold source, is controlled by a temperature controller 7 and a flow rate control valve 8a so as to maintain a constant temperature of the refrigerant gas flowing through the low-pressure refrigerant gas outlet pipe 6 from the cold box 9. .

In the conventional helium liquefaction refrigeration system configured as described above, when the temperature of the cooling water used in the compressor unit 1 changes, the temperature of the high-pressure refrigerant gas changes.
The temperature difference between the refrigerant gas inlet and outlet of the cold box 9 changes. This means that the cooling loss due to the difference in gas temperature at the inlet and outlet of the cold box 9 changes, and the device capacity fluctuates.

The above relationship will be explained with reference to FIG. FIG. 2 is an example showing the device capacity using the inlet temperature and outlet temperature of the refrigerant gas of the cold box as parameters. As shown in FIG. 2, it can be seen that in order to maintain the device capacity in response to the high-pressure refrigerant gas inlet temperature, it is necessary to change the low-pressure refrigerant outlet temperature.

As described above, in conventional helium liquefaction refrigeration equipment, in order to maintain equipment capacity in response to changes in the high-pressure refrigerant inlet gas temperature and to optimize the usage of liquid nitrogen, which is an auxiliary cooling source, it is necessary to adjust the temperature controller. Setting values had to be adjusted frequently.

In addition, such problems, as in this case,
In the case of a cryogenic refrigeration system in which a part of the high-pressure refrigerant gas is subjected to adiabatic expansion work by the first and second expanders 12a and 12b, and the remaining high-pressure refrigerant gas is subjected to Joel-Thomson expansion to generate liquefied refrigerant gas. Not limited to,
Needless to say, the same applies to cryogenic refrigeration equipment that cools the remaining high-pressure refrigerant gas by adiabatically expanding it to a cryogenic temperature that does not reach the liquefaction temperature, in other words, performing adiabatic expansion work on all of the high-pressure refrigerant gas. do not have.

[Purpose of the invention]

An object of the present invention is to provide an auxiliary cold source control for a cryogenic refrigeration system that can maintain the equipment capacity of a cryogenic refrigeration system using liquid nitrogen or the like as an auxiliary cold source and appropriately control the usage amount of the auxiliary cold source. The purpose is to provide a method.

[Summary of the invention]

A compressor unit compresses and circulates refrigerant gas, and a compressor unit uses liquid nitrogen as an auxiliary cold source to perform adiabatic expansion work on the high-pressure refrigerant gas compressed by the compressor unit to generate cold, which is used to generate cryogenic refrigerant. In a cryogenic refrigeration system consisting of a cold box, the temperature of the cooling water used in the compressor unit inevitably fluctuates depending on the ambient conditions, such as night and day, winter and summer. On the other hand, in order to maintain the heat balance of the cold box, it is necessary to keep the refrigerant gas temperature difference between the inlet and outlet of the cold box constant.

The present invention improves equipment capacity by controlling the supply amount of the auxiliary cold source so as to maintain a constant temperature difference between the high-pressure refrigerant gas compressed by the compressor unit and the low-pressure refrigerant gas returned from the cold box. This makes it possible to properly control the amount of auxiliary cold source used.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In Figure 3, the first
Components that are the same as those in the figures will be designated by the same reference numerals, and their explanations will be omitted, and parts that are different from those in FIG. 1 will be mainly described. Reference numeral 15 denotes an arithmetic unit for calculating a control set value for the low-pressure refrigerant gas temperature from the gas temperature of the high-pressure refrigerant gas introduction pipe 5. Other parts are the same as in FIG.

Next, the operation of the present invention having the above configuration will be explained. The temperature of the high-pressure refrigerant gas introduced from the compressor unit 1 fluctuates as the cooling water temperature of the compressor unit 1 fluctuates. A temperature set value is calculated and set in the controller 7. Based on the above set value, the controller 7 controls the supply amount of liquid nitrogen, which is an auxiliary cold source, by controlling the flow rate control valve 8a.
control by operating the

As described above, according to this embodiment, it is possible to appropriately maintain the heat balance of the cold box against fluctuations in the temperature of the high-pressure refrigerant gas introduced into the cold box, maintain the equipment capacity, and use the auxiliary cooling source. It becomes possible to easily maintain the amount appropriately.

〔Effect of the invention〕

According to the present invention, it is easy to maintain the equipment capacity of the cryogenic refrigeration equipment appropriately, the amount of auxiliary cold source used can be appropriately and easily controlled, and the energy efficiency of the equipment is improved. .

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a conventional cryogenic refrigeration system, Fig. 2 is a diagram showing an example of the characteristics of a cryogenic refrigeration system, and Fig. 3 is an implementation of a cryogenic refrigeration system implementing the present invention. FIG. 2 is a block diagram showing an example. 1...Compressor unit, 5...Introduction pipe, 6...
Outlet pipe, 7...controller, 8...flow control valve, 9...
...Cold box, 15...Arithmetic unit.

Claims (1)

[Claims] 1 a compressor unit that compresses and circulates refrigerant gas;
Cryogenic refrigeration consists of a cold box that uses liquid nitrogen or the like as an auxiliary cold source to perform adiabatic expansion work on the high-pressure refrigerant gas compressed by the compressor unit to generate cold, and uses the cold to generate cryogenic refrigerant. In the apparatus, the supply amount of the auxiliary cold source is controlled so as to maintain a constant temperature difference between the high-pressure refrigerant gas compressed by the compressor unit and the low-pressure refrigerant gas returned from the cold box. A method for controlling an auxiliary cold source for a low-temperature refrigeration system.