DE2020755A1 - Cooled vapor separator for vapor vacuum pumps - Google Patents

Description

NTAWWAtT

Dipl. Ing. .B. HOXZEB S9 AUGSBURG

-WISE »-STKASSE U

lirxrtra. 813ΪΪ

K. 343

Augsburg, April 28, 1970

Edwards High. Vacuum international Limited, Manor Royal Crawley, Sussex, England, and Cambridge Scientific Instruments Limited, Chesterton Road, Cambridge, Sussex,

England

Cooled vapor separator for vapor vacuum pumps

The invention relates to cooled vapor separators for vapor vacuum pumps and in particular for vapor vacuum pumps of systems with a very strong vacuum.

009845/1401

202075b

It is already known to connect cooled vapor separators between the vapor vacuum pumps and the devices to be evacuated in order to prevent steam from flowing from the relevant vapor vacuum pump to the device mentioned. In systems with a very strong vacuum, liquid nitrogen is normally used as the refrigerant, which is used to dissipate heat from cooling surfaces arranged in the vapor path between the vacuum pump and the device in question. This as a "separator" -i ¹ lächen cooling surfaces referred to achieve such a low temperature that resulting vapor particles freeze on them.

The liquid nitrogen is normally fed intermittently to the vapor separator, e.g. by is refilled via manually operated valves. This has the disadvantage that the steam separator is too local Ambient temperature begins to warm up when the Refilling of the refrigerant, or more precisely, cryogenic agent, is interrupted, so that both frozen vapor is released as well as fresh steam emitted by the vacuum pump is no longer separated properly.

Attempts were made to overcome this difficulty by means of water-cooled retaining walls arranged in the steam path

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which the steam condenses when in the steam separator there is no refrigerant. However, this in turn has the disadvantage that the JLb separator surfaces combined with the retaining walls impede the flow of the fluid to be evacuated in an impermissible manner.

In a known, cooled type of steam separator a set of separator surfaces connected to a carrier element in a heat-transferring manner, in which two coolant channels are formed. In one of these channels there is more fluid Nitrogen or some other cryogenic liquid while tap water or another in the other channel Fluid coolant is located, the temperature of which is normally below the "ambient temperature". Before this well-known steam separator put into operation , can, this must be in the relevant coolant duct Any water located is frozen so there is no water inside of this channel flows, while the cryogenic liquid flows through the other coolant channel, which keeps the various separator surfaces that interact with it at a very low temperature. This condition can only be achieved if the Stagnated water flow and the liquid nitrogen to freeze this stagnant water

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is used. Then a valve or a cock must be used of the water channel can be opened, with of course no flow due to the blocking ice results. When the system is then working normally, it will be hit by vapor particles from the separator surfaces deposited by freezing.

If the flow or the supply of liquid nitrogen is discontinuous and the respective If the remaining nitrogen has evaporated as a result of the penetrated heat, the temperature of the separator surfaces begins to rise. Here, the temperature can rise so far that the water frozen in the carrier element thaws. The separator surfaces then retain approximately the temperature of the cooling water, which now passes through the carrier element can flow freely through it. Under these circumstances the separator surfaces act as water-cooled surfaces, at which the steam condense and into the steam vacuum pump can flow back.

If fresh nitrogen or another relevant cryogenic liquid is then supplied, the water flow leading to the carrier element is again brought to a standstill for a certain period of time,

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because the nitrogen does not give the water what it takes to freeze it can extract the required amount of heat, if. the water is in motion. .

This known system has the disadvantages that an operator both the closing and opening the water valve to the corresponding Must monitor times and that the cyclical freezing and thawing of the carrier element, which is an Eontraction and expansion of this carrier element with it "brings" a requires more robust and massive vapor separator construction than would be functionally necessary. Furthermore must the vapor separator can be switched into a cooling water circuit, which is from the coolant circuit of the associated steam vacuum pump is disconnected.

The object of the invention is to be achieved in a cooled vapor separator of the type mentioned above Type even in the absence of a cryogenic liquid to keep the separator surfaces continuously at a certain temperature, which in general is below the ambient temperature.

In terms of solving this problem is a cooled

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Vapor separator for vapor vacuum pumps according to the invention through a reservoir or a channel for cooling liquid, furthermore through an inner flow path, in which there is an arrangement of separator surfaces is located, which have thermal contact with the reservoir or the channel, further through the reservoir or the Channel surrounding housing at a distance, which by means of a well-flowing coolant with reference to the Cooling liquid can be kept at a temperature closer to the ambient temperature, but below this temperature can, and by flow-cooled, the reservoir bzxir. the Additional areas not surrounding the duct are marked, which are arranged on the same side of the separator surfaces as the vacuum pump in question in such a way that the fluid-cooled housing and the fluid-cooled Additional areas in the absence of the The above-mentioned cooling liquid shield the separator surfaces from external heat sources so that the separator surfaces do so tend to assume a temperature which is closer to the temperature of said flowable coolant than the ambient temperature.

In the steam separator according to the invention, the cooling water flows continuously and the cooling water flow can

00984SM4Q1

with the cooling water flow for the relevant steam ■ Vacuum pump connected in series. Furthermore, a Operator not burdened with the task of opening a water valve each time with a certain delay or to open or close in certain time intervals. In addition, since the cooling water never freezes, the vapor separator of the present invention are lightweight in construction.

Several embodiments of the cooled vapor separator according to the invention are each described below with reference to the drawing as an example. They represent:

Ig. i a schematic axial section

an embodiment of the cooled vapor separator according to the invention,

2 shows a schematic axial section

a further embodiment of the steam separator according to the invention.

■■ "'' · ■ and

a schematic axial section

yet another embodiment

of the steam separator according to the invention.

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The cooled steam separator according to the invention shown in the drawing has an annular one Reservoir 2 for liquid nitrogen or another cryogenic liquid. Through the reservoir 2 A cylindrical flow path 4 leads through in the middle, in which elements υ having separator surfaces are arranged in a certain arrangement. These elements 6 are attached to the with reference to the drawings The lower end of the flow path 4 is held by supports 8, only one of which is shown in the drawing. These carriers 8 are mechanically and thermally conductive with the reservoir 2 and the elements β Connection and serve as heat transfer paths between the separator surfaces and the reservoir 2.Das Reservoir 2, the separator surfaces of the elements 6 and the supports 8 are each made of stainless steel and are preferably surface-treated, e.g. polished that they have a weak heat absorption and thereby the heat transfer by thermal radiation from the surrounding housing and the adjacent heat sources to the reservoir and the cryogenic liquid is reduced. In order to avoid penetration of heat to the reservoir 2 as a result of conductive connections, one is preferred inlet pipe IH also made of stainless steel

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of the reservoir 2 is relatively long and thin-walled. If this line 12 is not strong enough to be able to withstand the forces acting on it when the reservoir 2 is filled with liquid nitrogen. then, for reinforcement, connections or struts made of a poorly thermally conductive material can be provided, which run between the reservoir and the adjoining housing, but such connections are BSW. Struts not shown in the drawing, ura to keep them clear.

The reservoir 2 is accommodated in a housing 14 which is at a small distance from the cylindrical outer surface and the axially aligned end faces of the reservoir. A tube 16 is wound onto the housing 14, the inlet 18 of which can be connected to a tap or a valve, and the outlet 20 of which can be connected to the cooling coil of an associated steam "vacuum pump, not shown in the drawing," in Botrieb is the cooled steam separator, which consists essentially of the reservoir 2 and the housing lh, sealed off from the upper end of the vacuum pump. A likewise not shown, to be evacuated device is slrömurigSBiitteldicht with the surface of the housing lh

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tied together. With this arrangement, the fluid to be evacuated flows from the device with respect to the Drawing down through an opening 22 through into the housing 14 and passes over the separator surfaces of the elements 6 and a set of obliquely arranged additional surfaces 24 one provided with slot openings Shielding device, which is in xfarmele it ender connection with the housing 14, to a reference to the drawing of the lower opening 26 of the housing 14.

The axes of the slot openings and thus also the additional surfaces 24 run parallel to one another across the mouth of the opening 26, inclined and arranged to prevent that the separator surfaces 6 in addition to receiving other radiation from certain directions Vfärme, the Additional surfaces 24 are in a thermally conductive connection with the housing 14, so that they are essentially at the same temperature of the cooling water are kept. The additional surfaces 24 accordingly act as water-cooled cooling surfaces which coming from the vacuum pump. Steam condenses, but its main function is to act as heat radiation Signs to work. The Susatzflächen 24 hinder

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BA ORIGiNAL

consequently that of the institution concerned the flow leading to the vacuum pump is not as strong as real storage walls. In this embodiment of the According to the invention, the separator surfaces 6 can only be the cooled surfaces of the associated vacuum pump "See" and from the hot jet arrangement of the vacuum pump no heat through immediate Absorb radiation.

Regardless of the good thermal insulation of the reservoir and the separator surfaces 6 of the housing 14, they guarantee the almost complete enclosure of the Reservoirs and · the separator surfaces through the outer Housing and the shielding device, which are each kept at the temperature of the cooling water, and the fact that all connected lines and carriers are kept at the cooling water temperature j that in the absence of the. cryogenic liquid the temperature of the reservoir and the separator surfaces endeavors to assume the temperature of the cooling water, but not the temperature, if applicable adjacent heat sources, which is much higher.

When the system according to the invention is operated

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the intermediate space between the reservoir 2 and the housing Ik is automatically evacuated by the vapor vacuum pump, so that the reservoir 2 can essentially only absorb heat radiated from the housing 14 via this intermediate space and heat supplied along the inlet line 12. The inwardly radiated heat can be reduced to a minimum value by appropriate design of the surfaces of the housing, which is preferably made of stainless steel, for example by polishing the housing surfaces.

During operation, the housing 14 is through the tap water flowing continuously through the cooling coil 16 is kept at a temperature, which is usually below the ambient temperature.

As a result of the very small heat transfer from the housing 14 to the reservoir 2 there is no risk that the water flowing through the cooling coil 16 freezes ». The liquid located in the reservoir 2 Nitrogen slowly absorbs heat and vaporizes in the process, but the reservoir 2 essentially becomes

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BATH

kept at the temperature of liquid nitrogen, that is, at -196 C, as long as there is liquid nitrogen in this reservoir. The separator surfaces 6 take this temperature or one of these only v / s 12; different temperature as soon as stable operating conditions are reached, while the additional surfaces 2k essentially have the temperature of the cooling water.

I -'- at the end of the operation of the steam vacuum pump Steam from the operating fluid, e.g. oil or mercury, striving to flow back into the facility to be evacuated. The steam flows around the additional surfaces 24, which are so cold that a portion of this Dar.ipfe-s condenses on these surfaces and into the Vacuum pump falls back. The remaining part of the steam is collected by the separator surfaces 6, on which the vapor particles freeze immediately, so leave the space above the separator surfaces and in particular, the evacuated equipment is substantially free of contaminants caused by the steam Can be evoked. When all of the liquid Nitrogen in the reservoir 2. has evaporated, e.g. when the establishment during the night or during the

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If it is not used at weekends, the heat entering the reservoir increases continuously. Through the Invention, this unwanted penetration of heat is reduced to a minimum, as the far largest part of the surfaces of the reservoir and the associated separator surfaces only from the housing fro heat can receive, the remaining surface areas of the reserve voyage, in practice essentially only the cylindrical inner surface forming the flow path 4, and the separator surfaces 6 can also receive a limited amount of heat via the openings 22 and 26, however, the spatial angle within which heat can be received from external heat sources is tiny. As a result, the temperature of the Separator surfaces 6 can rise substantially only up to the temperature of the cooling water or only very much little more and that the temperature of the separator surface consequently always remains below the ambient temperature. If this heating of the reservoir and the separator surfaces is not interrupted, it stabilizes the temperature at a value essentially corresponding to the cooling water temperature, and the separator surfaces act more as water-cooled surfaces, but no longer as cold-central-cooled surfaces, which are thereby

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ns

The resulting lower efficiency with regard to the separation of vapor particles is about the relevant Acceptable period of time during which the plant is out of order and is still sufficient good for avoiding severe contamination of the interior of the facility as a result of condensed steam.

In some applications of the steam separator according to the invention, it may be sufficient if the Vapor separator does not feed any cryogenic liquid is, but only the separator surfaces 6 and the additional surfaces 24 are used, the amount of steam reaching the interior of the device on a to maintain a reasonable value. However, it is about achieving it a better efficiency with regard to the separation of steam expedient and in certain cases even necessary, use liquid nitrogen or another cryogenic liquid.

FIGS. 2 and 3 of the drawing show that the spatial angle within which thermal radiation can reach the reservoir and the separator surfaces, for example, can be further reduced by appropriate approaches of the housing 1: 4. In the case of the in Fig. 3

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In the illustrated embodiment, the housing has a ^{projection 28 which extends vertically upward with reference to FIG. 1 of} the drawing and has a through opening 22. In the embodiment shown in FIG. 2, the housing has an inwardly drawn edge JO which effectively shields the cylindrical inner surface of the reservoir. These or similar embodiments of the invention can be used as appropriate.

In FIGS. 2 and 3, the separator surfaces and the heat radiation shields are for a better overview not shown.

The person skilled in the art will of course have further possible modifications within the scope of the invention. For example, the additional surfaces 2k indicated as being arranged parallel to one another can have the shape of a plurality of truncated cone outer surfaces arranged concentrically to one another. On the other hand, the separator surfaces shown as frustoconical jacket surfaces can be formed by mutually parallel, inclined strips, which are arranged in such a way that no linear path passes through the flow path 4 which is not of the

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Separator surfaces, the reservoir or approaches this Reservoirs is cut.

From this it can be seen that it is in the invention Steam separator is not required, jevreils To use water taps when it is operated with cryogenic liquid., And that the vapor separator according to the invention can have a relatively light construction, which by its function as a is determined by need, mechanically to be particularly robust.

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Claims (11)

Patent claims : Clj Cooled vapor separator for vapor vacuum pumps, characterized by a reservoir (2) or a channel for cooling liquid, furthermore by an inner flow path (4) in which there is an arrangement of separator surfaces (6) which are connected to the reservoir or the Channel have thermal contact, further through a housing (14) surrounding the reservoir or the channel at a distance, which can be kept at a temperature closer to, but below the ambient temperature with reference to the cooling liquid by means of a coolant with good flowability, and by fluid-cooled _e additional surfaces (24) not surrounding the reservoir or the channel, which are arranged on the same side of the separator surfaces as the relevant vacuum pump in such a way that the fluid-cooled housing and these fluid-cooled additional surfaces shield the separator surfaces from external heat sources in the absence of said cooling liquid , there ß the separator surfaces tend to assume a temperature which - 18 Ö098A5 / U01 the temperature of said fluid coolant closer than the ambient temperature. 2. Steam separator according to claim 1, characterized characterized in that said additional surfaces (24) by one provided with slot openings, with said flowable coolant in heat-transferring connection standing shielding device are formed or have one which extends at least over that end of said inner flow path (4) extends away which is the relevant vacuum pump closer, so that this shielding device than Thermal radiation shield acts. 3. Steam separator according to claim 2, characterized characterized in that said slot openings (at 24) of the shielding device with their respective longitudinal axes run parallel to each other. 4. Steam separator according to one of claims 1 to 3 «characterized in that at least some of the named separator surfaces (6) by an arrangement of frustoconical elements are formed, which longitudinal . -.19-.
00 9 8-4 5 / U0 1 W ■ the axis of said inner flow path (4) are arranged at a distance from one another. 5. Steam separator according to one of claims 1 to 4, characterized in that the housing (14) directly carries the reservoir (2) or the channel for the cooling liquid. 6. Steam separator according to one of claims 1 to 5, characterized in that the reservoir (2) has the shape of an annular container through which the essentially cylindrical inner flow path (4) leads through. 7 · Steam separator according to claim 6, characterized in that that the reservoir (2) the separator surfaces (6) and each between the reservoir and the separator surfaces extending associated beams (e.g. 8) are each made of stainless steel. 8. Steam separator according to claim 7 *, characterized in that that the surfaces of the stainless steel parts are each smoothed or polished. - 20 0098A5 / U01 9. Steam separator according to one of claims 1 to 8, characterized in that said additional surfaces (24) are formed by parts protruding from the housing (14), which reduce the physical angle at which ' the reservoir and / or the separator surfaces (6) of can absorb heat radiation outside the steam separator. 10. A vapor separator according to claim 9 »characterized in that one of the said additional surfaces (24) is formed by an inwardly drawn edge 00) which is a certain distance inward from the walls of the flow path (4) passing through the reservoir (2) has out (Fig. 2). 11. A vapor separator according to claim 9 or 10, characterized in that said one or another of the additional surfaces (24) is formed by an extension or an extension 00 or 28), which or which to the through the reservoir (2 ) running through the inner flow path (4) runs coaxially and forms an extension of the same (Flg. 2, 3) - 21 - 00 984 5 / UO 1