DD290939A5 - FLOW REGULATOR FOR KRYGOGENIC COOLER - Google Patents

Abstract

The invention relates to a flow control for gas stream, which can be used in Kaelteerzeugungsanlagen low power. The diamagnetism of a superconducting substance is used during the transition from the normal conducting to the superconducting state. In particular, in the present invention, substances are used which become superconducting in the vicinity of the boiling temperature of the liquid nitrogen (Tc78 K) (so-called high-temperature superconductors). The essence of the invention is that a needle forming a valve together with a dome is mounted on a permanent magnet and the permanent magnet is located above a superconducting material exhibiting the Meiszner effect {flow control; Gas; Kaelteanlage; Substance, superconducting; Nitrogen; High temperature superconductors; Needle; Jet; Valve; Permanent magnet; Meiszner effect}

Description

For this 1 page drawing

Field of application of the invention

The invention relates to a flow controller for cryogenic coolers, the z. B. based on the throttled relaxation of a high-pressure gas using a limited gas reservoir works (eg Joule-Thomson cooler). The invention may, for. B. are used for cooling electronic components.

Characteristic of the known state of the art Cryogenic coolers, such as. B. Joule-Thomson cooler, i. a. from displacer, heat exchanger and expansion nozzle. The Radiator is surrounded by a cryostat. The regulation of the flow through the expansion nozzle has in addition to the Extension of the operating time at the same time a constancy of the working temperature of the mounted on the cooled surface Sensors result. In the field of liquid nitrogen i.a. Infrared sensors. In principle, the control can be installed both outside and inside the cooler. Thermodynamic on

most favorable proves the arrangement of the control in the interior (displacement) of the radiator.

With regard to the type of control, the following systems can be distinguished:

a) flow control by cross-sectional change of the throttle,

b) flow control with immediate or delayed feedback,

c) Flow control with pulsating or quasi-stationary mass flow rate.

The control elements are bimetals, direct and indirect expansion elements, materials with memory and bellows

Commitment.

Fast coolers, which are characterized by the largest possible cooling rate, use a temperature sensor,

which is not contacted directly in the expansion space, but on a precisely fixed intermediate temperature level (DE-OS

To compensate for the stationary power loss, the nozzle flows through a constant, minimal gas flow. This is realized

by notches in the nozzle needle (US-PS 4569210) or by additional drilling (US-PS 4468935). The advantages of a

Bimetallic regulation, how

- Lower production costs

- small mass and small heat capacity

- any shape

- No influence by pressure fluctuations in the expansion area

There are disadvantages, in particular as a result of expected aging and the associated change in the

Adjustment be caused. A variety of solutions use expansion elements for flow and temperature control. In US-PS 4468935 and in the SU-PS1177611, the different expansion coefficients of different materials when cooled for the Utilized plant. An additive coupling of several expansion elements is known from DE-OS 2801215. Due to the

expected control paths of a few micrometers, a very high manufacturing accuracy is necessary. In addition, complicated arrangements must be provided to accurately set the operating point (US Patent No. 4569210, DE-OS

The use of bellows as a control element has the following disadvantages:

- the bellows must be filled with a well-defined pressure depending on the working temperature range,

the requirements on the purity of the filling gas or the constancy of the composition when using gas mixtures are extremely high,

- a fine adjustment is no longer possible after filling

- the long-term stability is determined by the tightness of the bellows, including the solder or welded joints,

- Pressure fluctuations in the expansion chamber affect the position of the bellows.

Object of the invention

The object of the invention is a miniaturizable and maintenance-free controller for a cryogenic cooler.

Presentation of the essence of the invention

The object of the invention is a flow controller for cryogenic coolers, which is free of hysteresis and aging effects.

According to the invention the object is achieved in that a needle which forms a valve together with the nozzle, is mounted on a permanent magnet and the permanent magnet is located above a superconducting material, which shows the Meissner effect. The permanent magnet is in the normal conducting state of the superconducting material on the superconducting material. In the superconducting state of the material, the needle engages the nozzle.

In this case, the Meissner effect which occurs during the transition from the normally-loosening state to the ^H 9n superconducting state is utilized, according to which a magnetic field is displaced from a superconductor. When the superconductor transitions to the superconducting state, the permanent magnet is lifted off the superconductor and engages with the needle retained on it into the expansion nozzle of the cooler. The inflow of refrigerant is throttled or interrupted. Rises the temperature of the

Superconductor back on, which corresponds to the transition to the normalleitendon state, the diamagnetism is released and the Entscannungsdüse released.

The controller k / jnn be part of a Joule-Thomson cooler with the known main components displacer, heat exchanger and expansion nozzle. The superconducting material is at the same time the inner bottom of the Joule-Thomson cooler surrounding cryostat or component thereof.

It is advantageous if the bottom of the superconducting material is concave towards the nozzle.

Particularly advantageous is a high-temperature superconductor made of ceramic. The coolant used is liquid nitrogen. An infrared sensor can be arranged on the superconductor. By appropriate choice of the composition of the grain and the firing conditions of the ceramic, both the position (working temperature of the sensor) and the width of the transition curve, which decisively co-determines the control fluctuation of the sensor temperature, can be influenced.

Such a regulation, in contrast to regulations that use mechanical actuators, aging and hysteresis-free.

In addition, it takes up very little space and there are no suspensions must be performed in the displacement of the radiator.

embodiment

The invention will be explained using the example of a Joule-Thomson cooler. The drawing shows the cooler with the flow controller according to the invention in a sectional view.

The Joule-Thomson cooler is miniaturized and consists of the known main components displacer 1, heat exchanger 3 and expansion nozzle 4. It is surrounded by a cryostat with an entrance window 9. The working gas is nitrogen. An infrared sensor 8 is located in the vacuum space 2 of the cryostat and is thermally well contacted to the inner bottom of the cryostat, which consists of a superconducting ceramic 7. The ceramic shows the Meissner effect. The material used was YiBa ₂ Cu ₃ O ₇ . A needle, which forms a valve together with the expansion nozzle 4, is mounted on a permanent magnet 5. The permanent magnet 5 is mounted in a guide 6 and is located between the ceramic 7 and the expansion nozzle 4. It is biased by a spring 11 against the superconducting material 7. Reached the ceramic 7 as a result of the relaxation of the high pressure gas, the range of the transition temperature (transition from the normal conducting to the superconducting state), the permanent magnet 5 is pressed upwards due to the Meissner effect and closes the expansion nozzle 4. The temperature of the ceramic 7 rises due to the now When the cooling capacity has become lower again, the diamagnetism of the superconducting state of the ceramic 7 is eliminated and the permanent magnet 5 releases the nozzle opening again.

The relatively large width of the transition curves of the superconducting ceramics is to be regarded as favorable for the control behavior since there is no abrupt closing and opening of the expansion nozzle.

Claims (3)

1. Flow controller for cryogenic coolers, in which the refrigerant flows through a nozzle which forms a valve together with a needle, characterized in that the needle (10) with a permanent magnet (5) is connected directly or via levers and the permanent magnet (5 ) against a superconducting material (7) such as La ₂ - _x Ba _x CuO ₄ - _y , Y ₂ - _x Ba, Cu (- _y) , YiBa ₂ CUaO _7, or another which exhibits the Meissner effect Spring (11) or biased by its own weight. -1- 290 93d Claims: 2. Flow controller according to claim 1, characterized in that the superconducting material (7) forms the bottom of the inner vessel of a cryostat ι nit Joule-Thomson cooler or is part of the soil. 3. Flow controller according to claims 1 and 2, characterized in that the bottom of the superconducting material (7) to the nozzle (4) out konka /.