GB2084306A

GB2084306A - Cooling Apparatus

Info

Publication number: GB2084306A
Application number: GB8119331A
Authority: GB
Original assignee: Kernforschungszentrum Karlsruhe GmbH
Current assignee: Forschungszentrum Karlsruhe GmbH
Priority date: 1980-07-25
Filing date: 1981-06-23
Publication date: 1982-04-07
Also published as: DE3028217A1; GB2084306B

Abstract

Apparatus for producing low temperatures has an oil-flooded compressor (1) with oil lubrication and to which compressor a helium gas circuit is connected having a high- pressure line (16) extending to an object (15) to be cooled and a low- pressure line (11) extending from this object to be cooled back to the compressor. A cooling system (3) and an oil separating system (4) are included in the high-pressure line and the high-pressure line is connected to the low-pressure line via a connecting line (18) which includes pressure- relieving means (8). Means (13, 14) for retaining oil is installed in the low- pressure line (11) between the object to be cooled (15) and the point of connection (20) for said connecting line (18). <IMAGE>

Description

SPECIFICATION Cooling Apparatus The invention relates to an apparatus for producing low temperatures having a compressor with oil-circulation lubrication, to which compressor a helium gas (He) circuit is connected having a high-pressure line extending to the object to be cooled and a low-pressure line extending from this object back to the compressor - a cooling system and an oil separating system being installed in the high-pressure line and the high-pressure line being connected to the lowpressure line via a connecting line which comprises pressure relieving means.

A cooling unit of this type produces temperatures of between 40 K and 300 K which are stable for weeks - no fluid coolants being required. The refrigerating capacity is dependent upon the specific location of the cooling system on theobject itself, e.g. a four cycle goniometer of a diffractometer for neutron diffraction experiments on mono-crystals. Cooling units of this type are known as "Split Cycle Refrigerators" and are manufactured, for example, by the company called "Air Products and Chemicals".

After between 1000 and 6000 operating hours, however, faults occur in the systems, such faults manifesting themselves as a reduction in the refrigerating capacity associated with the cooling system being fouled by oil at the object to be cooled. The improvements which technical circles have made in the cooling system and highpressure-line system by, for example, an additional use of filters, produced only temporary success. It was considered to be impossible or was not recognised at least for the cooling system to be fouled by oil at the object to be cooled by way of the connecting line from the low-pressure side counter to the flow direction of the gas returning to the compressor.

It is an object of the invention to prevent the cooling capacity from being reduced and/or to prevent or minimize the cooling system from being fouled by oil at the object to be cooled.

According to the present invention there is provided apparatus for producing two temperatures having a compressor with oil lubrication and to which compressor a helium gas circuit is connected having a high-pressure line extending to an object to be cooled and a lowpressure line extending from this object to be cooled back to the compressor, a cooling system and an oil separating system being included in the high-pressure line and the high-pressure line being connected to the low-pressure line via a connecting line which includes pressure-relieving means, characterised in that means for retaining oil is installed in the low-pressure line between the object to be cooled and the point of connection for said connecting line.

Preferably the retaining element is a non-return or check valve and/or a trap or syphon. Further, the oil separating means is preferably an oil separator and an oil-vapour separator.

The invention will be described further, by way of example, with reference to the accompanying drawing which is a schematic illustration of a cooling or refrigeration system.

An "oil-flooded" or oil utilizing compressor 1 sets in motion a cooling circuit which has helium gas (He) as the cooling gas or refrigerant and can cool an object 1 5 at the end of a high-pressure line 1 6 to temperatures of approx. 32 K. A low pressure line 11 leads from the object 1 5 back to the compressor 1.

Connected downstream of the compressor 1 in the high-pressure line 16 is a cooling coil 3, which is cooled by a fan 2, and an oil separating device 4. The oil separating device 4 preferably comprises a compressed-air gas oil separator 4', which has a pressure rate of 30 m3/h and is constructed so as to be helium-tight, and the oil separating device also has an oil-vapour separator 4". Connected downstream of the oil separator 4 itself is an oil absorbing vessel 5 in the highpressure line 1 6 before it leads to the object 1 5 to be cooled. Oil which has been separated in the oil separator 4' flows via the capillary line 12 back to the compressor 1 which is provided with an oil level indicator 9 and an oil filler pipe 10.

The pressure between the oil separator 4 (4', 4") and the oil absorbing vessel 5 is indicated or monitored by the manometer 7. If the pressure rises in the high-pressure line 1 6 above a predetermined limit, then a pressure balance is effected via a connecting line 1 8 with the safety or pressure relieving valve 8 and a by-pass 1 9 parallel thereto. The pressure behind the pressure-relieving valve 8 is likewise determined and/or monitored by the manometer 6.

This connecting line 1 8 is connected to the low-pressure line 11 prior to its entry into the compressor 1. It can generally be explained that oil may enter the low-pressure line 11 via this connecting line 1 8. However, technical circles hitherto excluded the possibility that this oil could diffuse counter to the flow direction of the He gas returning from the object 15, relative to the compressor 1. This phenomenon has been proved, however, by way of experiments carried out for this purpose.

In order to correct this fault, an oil trap in the form of a non-return or check valve 13 and a trap or syphon 14 is therefore also installed in the lowpressure line 11 upstream of the attachment point 20 for the connecting line 1 8. Experiments and tests at 120 K and 52 K over thousands of hours proved that the cooling system of the invention operated faultlessly with stable pressure.

Claims

1. Apparatus for producing low temperatures having a compressor with oil lubrication and to which compressor a helium gas circuit is connected having a high-pressure line extending to an object to be cooled and a low-pressure line extending from this object to be cooled back to the compressor, a cooling system and an oil

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Cooling Apparatus The invention relates to an apparatus for producing low temperatures having a compressor with oil-circulation lubrication, to which compressor a helium gas (He) circuit is connected having a high-pressure line extending to the object to be cooled and a low-pressure line extending from this object back to the compressor - a cooling system and an oil separating system being installed in the high-pressure line and the high-pressure line being connected to the lowpressure line via a connecting line which comprises pressure relieving means. A cooling unit of this type produces temperatures of between 40 K and 300 K which are stable for weeks - no fluid coolants being required. The refrigerating capacity is dependent upon the specific location of the cooling system on theobject itself, e.g. a four cycle goniometer of a diffractometer for neutron diffraction experiments on mono-crystals. Cooling units of this type are known as "Split Cycle Refrigerators" and are manufactured, for example, by the company called "Air Products and Chemicals". After between 1000 and 6000 operating hours, however, faults occur in the systems, such faults manifesting themselves as a reduction in the refrigerating capacity associated with the cooling system being fouled by oil at the object to be cooled. The improvements which technical circles have made in the cooling system and highpressure-line system by, for example, an additional use of filters, produced only temporary success. It was considered to be impossible or was not recognised at least for the cooling system to be fouled by oil at the object to be cooled by way of the connecting line from the low-pressure side counter to the flow direction of the gas returning to the compressor. It is an object of the invention to prevent the cooling capacity from being reduced and/or to prevent or minimize the cooling system from being fouled by oil at the object to be cooled. According to the present invention there is provided apparatus for producing two temperatures having a compressor with oil lubrication and to which compressor a helium gas circuit is connected having a high-pressure line extending to an object to be cooled and a lowpressure line extending from this object to be cooled back to the compressor, a cooling system and an oil separating system being included in the high-pressure line and the high-pressure line being connected to the low-pressure line via a connecting line which includes pressure-relieving means, characterised in that means for retaining oil is installed in the low-pressure line between the object to be cooled and the point of connection for said connecting line. Preferably the retaining element is a non-return or check valve and/or a trap or syphon. Further, the oil separating means is preferably an oil separator and an oil-vapour separator. The invention will be described further, by way of example, with reference to the accompanying drawing which is a schematic illustration of a cooling or refrigeration system. An "oil-flooded" or oil utilizing compressor 1 sets in motion a cooling circuit which has helium gas (He) as the cooling gas or refrigerant and can cool an object 1 5 at the end of a high-pressure line 1 6 to temperatures of approx. 32 K. A low pressure line 11 leads from the object 1 5 back to the compressor 1. Connected downstream of the compressor 1 in the high-pressure line 16 is a cooling coil 3, which is cooled by a fan 2, and an oil separating device 4. The oil separating device 4 preferably comprises a compressed-air gas oil separator 4', which has a pressure rate of 30 m3/h and is constructed so as to be helium-tight, and the oil separating device also has an oil-vapour separator 4". Connected downstream of the oil separator 4 itself is an oil absorbing vessel 5 in the highpressure line 1 6 before it leads to the object 1 5 to be cooled. Oil which has been separated in the oil separator 4' flows via the capillary line 12 back to the compressor 1 which is provided with an oil level indicator 9 and an oil filler pipe 10. The pressure between the oil separator 4 (4', 4") and the oil absorbing vessel 5 is indicated or monitored by the manometer 7. If the pressure rises in the high-pressure line 1 6 above a predetermined limit, then a pressure balance is effected via a connecting line 1 8 with the safety or pressure relieving valve 8 and a by-pass 1 9 parallel thereto. The pressure behind the pressure-relieving valve 8 is likewise determined and/or monitored by the manometer 6. This connecting line 1 8 is connected to the low-pressure line 11 prior to its entry into the compressor 1. It can generally be explained that oil may enter the low-pressure line 11 via this connecting line 1 8. However, technical circles hitherto excluded the possibility that this oil could diffuse counter to the flow direction of the He gas returning from the object 15, relative to the compressor 1. This phenomenon has been proved, however, by way of experiments carried out for this purpose. In order to correct this fault, an oil trap in the form of a non-return or check valve 13 and a trap or syphon 14 is therefore also installed in the lowpressure line 11 upstream of the attachment point 20 for the connecting line 1 8. Experiments and tests at 120 K and 52 K over thousands of hours proved that the cooling system of the invention operated faultlessly with stable pressure. Claims

1. Apparatus for producing low temperatures having a compressor with oil lubrication and to which compressor a helium gas circuit is connected having a high-pressure line extending to an object to be cooled and a low-pressure line extending from this object to be cooled back to the compressor, a cooling system and an oil separating system being included in the highpressure line and the high-pressure line being connected to the low-pressure line via a connecting line which includes pressure-relieving means, characterised in that means for retaining oil is installed in the low-pressure line between the object to be cooled and the point of connection for said connecting line.

2. Apparatus as claimed in claim 1, in which the retaining element comprises a check valve and/or a trap.

3. Apparatus as claimed in claims 1 and 2, in which the oil separating system comprises an oil separator and an oil-vapour separator.

4. Apparatus as claimed in any of claims 1 to 3, in which a by-pass valve is connected in parallel to the pressure relieving means.

5. Apparatus constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.