GB2052710A

GB2052710A - Cryogenic Container

Info

Publication number: GB2052710A
Application number: GB7921847A
Authority: GB
Original assignee: DEMENKO V; SHALAEV V; TSOGLIN G
Current assignee: DEMENKO V; SHALAEV V; TSOGLIN G
Priority date: 1979-06-22
Filing date: 1979-06-22
Publication date: 1981-01-28
Also published as: FR2462358A1; DE2926646A1

Abstract

A cryogenic container (e.g. for storing and conveying biological products) comprises a jacket 1 and a heat-insulated vessel 2 disposed within the jacket and joined therewith by a neck tube 3. The container includes also a cap 5 with a plug 6. The plug 6 is made of a heat-insulating material (e.g. foam plastic), and fitted in the neck tube 3 so that therebetween there is a passage 7 for escape of the refrigerant vapours. The side wall 8 of the cap 5 envelops with a clearance 9 a portion "M" of the outer surface of the jacket 1, adjacent to the neck tube 3, and forms therewith an annular chamber 10 communicating both with the atmosphere through the clearance 9 and with the passage 7 for escape of the refrigerant, so that the refrigerant vapours leaving the neck tube 3 through the passage 7 expand in the chamber 10 and cool the portion "M" of the surface of the jacket (1), which results in diminishing the refrigerant evaporation rate. The cap and plug may comprise an integral part (e.g. Fig. 5). <IMAGE>

Description

SPECIFICATION Cryogenic Container The present invention relates to the art of cryogenic engineering and is specifically concerned with the design of cryogenic containers employed for storing and conveying biological products at low temperatures.

The invention may be most advantageously used in stock breeding for storing and conveying the cattle semen intended for the artificial insemination. It may also be used in the medicine for storing and conveying the bone marrow, crystalline lenses of eyes, and like biological specimens.

In accordance with the present invention, there is provided a cryogenic container comprising a jacket, a heat-insulated vessel for the refrigerant, disposed within the jacket and provided with a neck tube joining the vessel with the jacket, and a cap with a plug made of a heat-insulating material and fitted in the neck tube so that a passage for the refrigerant vapours to escape is formed between the plug and the neck tube, the cap having a side wall enveloping with a clearance a portion of the jacket surface adjacent to the neck tube, and forming jointly with said jacket surface an annular chamber communicating both with the atmosphere through the clearance and with the passage for the refrigerant vapours, so that the refrigerant vapours flow into the chamber to cool the jacket surface portion enveloped by the cap.

With such a construction of the cryogenic container, the refrigerant vapours leaving the neck tube at a relatively low temperature move over the jacket surface adjoining the neck tube and, entering into a heat exchange with the surface, lower its temperature as against that of the ambient atmosphere.

This reduces the temperature difference between the jacket and the neck tube and hence decreases the heat inflow from the outside through the jacket and neck tube to the inside of the cryogenic container, thereby diminishing the refrigerant evaporation rate.

It is expedient that the area of the jacket surface enveloped by the side wall of the cap constitute from 2 to 7 percent of the total jacket surface area.

Such an area of the jacket surface enveloped by the side wall of the cap yields the most efficient cooling of the surface by the refrigerant vapours. It has been- also found that if said area is less than 2 percent of the total jacket surface area, only a comparatively small portion of the jacket surface is cooled, which is insufficient to substantially decrease the heat inflow from the outside through the jacket into the neck tube. If said area exceeds 7 percent of the total jacket surface area, the refrigerant vapours escaping from the neck tube are incapable of cooling the whole jacket surface portion enveloped by the cap because of their limited cooling capacity.A further increase of this jacket surface portion area is therefore inexpedient, since this will only increase the container dimensions and mass without any substantial decrease in the heat inflow and in the refrigerant evaporation rate.

An embodiment of the cryogenic container is advantageous, wherein the cap envelops the jacket with a clearance whose cross-sectional area does not exceed that of the passage for the refrigerant vapours.

This embodiment of the container provides for creating in the annular chamber an excess (with respect to the atmospheric one) pressure of a relatively small magnitude (1 to 5 mm Hg). Such an insignificant pressure calls for no special seals and especially strong materials for the cap, and yet is suff;cient enough to prevent an ingress of the ambient air into the annular chamber and thereby to preclude a possible temperature rise therein.

The invention will now be explained with reference to particular embodiments thereof which are represented in the accompanying drawings, wherein: Fig. lisa longitudinal section of the cryogenic container according to the invention; Fig. 2 is a longitudinal section of the top portion of the cryogenic container, wherein the side wall of the cap has a cylindrical configuration; Fig. 3 is the same as Fig. 2, and wherein the side wall of the cap has the configuration of a surface of revolution having a convex generatrix; Fig. 4 is the same as Fig. 2, and wherein the side wall of the cap has the configuration of a surface of revolution having a concave generatrix; Fig. 5 is the same as Fig. 2, and wherein the cap is integral with the plug.

A cryogenic container comprises a jacket 1 (Fig. 1) and a vessel 2 for the refrigerant, disposed within the jacket. The vessel 2 is joined with the jacket 1 by a neck tube 3.

To cut down the heat inflows, the vessel 2 is heat-insulated with the use of a vacuum-and-screen heat insulation 4.

The container comprises also a cap 5 with a plug 6 secured therein. The plug 6 is fitted in the neck tube 3 with a clearance so that an annular passage 7 for the refrigerant vapours to escape is provided therebetween.

Since the heat inflow into the cryogenic container occurs predominantly through the neck tube 3, the latter, as well as the plug 6, is made of a heat-insulating material. Specifically, the neck tube 3 is of fiber-glass plastic, and the plug 6 of foam plastic. It is clear that the neck tube 3 may be metallic, in which the thickness of the vacuum-and-screen heat insulation 4 in the zone of the neck 3 should be increased to reduce the heat condition. The vessel 2, jacket 1, and cap 5 may be of any adequately strong material suitable for this purpose, such as, for example aluminium.

In accordance with the invention, the cap 5 has a side wall 8 which envelops, with a clearance 9, the portion of the surface of the jacket 1 adjacent to the neck tube 3 and defined by the top edge of the neck tube 3 and by the bottom edge of the cap 5 (this portion is denoted by letter "M" in Fig. 1). The side wall 8 of the cap 5 jointly with said portion of the surface of the jacket 1 and with the plug 6 defines an annular chamber 10.

In the present invention, the term "annular chamber" is intended to denote a chamber having the configuration of a body produced by movement of a plane figure along a closed path, such as by rotation of the figure about an axis lying in the plane of the figure, but not intersecting the latter. In the embodiment of the container, shown in Fig. 1, such figure is a triangle defined by the side wall 8 of the cap 5, the portion "M" of the surface of the jacket 1, and the plug 6, and the axis of the conventional rotation of the triangle is the axis of symmetry of the container. It will be readily apparent that an annular chamber not only of a triangular, but also of another cross-section may be provided for the cryogenic container under consideration.

The passage 7 for escape of the refrigerant vapours terminates in the annular chamber 10, while the chamber itself communicates via the clearance 9 with the atmosphere.

The above-described cryogenic container functions as follows. The vessel 2 is filled through the neck tube 3 with the refrigerant, specifically liquid nitrogen, and then loaded with holders with a biological product (not shown in the drawing). Then the cryogenic container is closed with the cap 5 so that the plug 6 is received into the neck tube 3.

In operation the liquid nitrogen vapours rise along the passage 7 and, entering into a heat exchange with the neck tube 3 and the plug 6, which receive heat from the surrounding atmosphere, cool them. This somewhat raises the temperature of the nitrogen vapours, which, however, still remains relatively low owing to a low heat conductivity of the materials whereof the plug 6 and the neck tube 3 are fabricated.

On leaving the neck tube 3, the vapours enter the annular chamber 10 where, expanding, they cool the portion "M" of the surface of the jacket 1 by convection. At the outlet of the chamber 1 0, the vapours are throttled in the clearance 9, thereby further cooling the surface of the jacket 1.

As a result, the temperature difference between the surface of the jacket 1, adjacent to the neck tube 3, and the neck tube 3 itself is considerably reduced, which decreases the heat inflow into the cryogenic container and consequently diminishes the rate of evaporation of liquid nitrogen.

The cap 5 also prevents the refrigerant vapours leaving the neck tube 3 against being blown off the surface of the jacket 1 by a wind or draught and thereby provides for a more complete utilization of the cooling capacity of the refrigerant and hence for a more efficient lowering of the temperature of said surface.

To find out what effect the area of the portion "M" has upon the rate of evaporation of liquid nitrogen, the authors have conducted a study with a 34 1 cryogenic container having a jacket outside surface area of 4,000 cm2, and the neck tube diameter of 60 mm. The results of the study are tabulated below.

Area ofjacket surface portion 'M" enveloped by cap Liquid nitrogen in percent of total evaporation rate, ExperimentNo. jacket surface area in cm2 g/day 1 0 0 220.0 2 1 40 213.75 3 2 80 208.80 4 3 120 204.05 5 4 160 201.10 6 5 200 200.75 7 6 240 199.95 8 7 280 199.86 9 8 320 199.83 10 9 360 199.80 The data represented in the Table indicate that the rate of evaporation of liquid nitrogen is reduced most efficiently when the area of the portion "M" of the surface of the jacket 1, enveloped by the cap 5, makes up from 2 to 7 percent of the total area of the surface of the jacket 1. It can be seen from the Table that when the area of said portion is less than 2 percent of the total surface area of the jacket 1, the liquid nitrogen evaporation rate still remains relatively high, whereas increasing the area of the portion "M" above 7 percent of the total surface area of the jacket 1 will but insignificantly diminish the liquid nitrogen evaporation rate, resulting at the same time in greater overall dimensions and mass of the cryogenic container.

In order to prevent an ingress of the ambient air into the chamber 1 0 and thereby to preclude a possible ternperature rise therein, the invention is embodied so that the cross-sectional area of the clearance 9 does not exceed that of the passage 7.

With such an embodiment, the pressure of the nitrogen vapours in the chamber 10 is about from 1 to 5 mm higher than the atmospheric pressure. The excess pressure of such an insignificant magnitude calls for neither sealing of the chamber 10, nor especially strong materials for the cap 5, and yet constitute a quite dependable barrier for the air surrounding the cap 5.

The cryogenic container of the present invention provides for diminishing the rate of evaporation of liquid nitrogen, on the average, by 7-8 percent as against that in prior art containers, which allows the period of biological product storage in the cryogenic container to be prolonged.

It is to be pointed out that the rate of refrigerant evaporation can be controlled within a narrow range by varying the profile of the annular chamber 10 by means of changing the configuration of the side wall 8 of the cap 5. Possible configurations of the side wall 8 of the cap 5 are represented in Figs.

1 through 4.

Specifically, in Fig. 1 the side wall 8 is conical, and in Fig. 2, cylindrical. The cap 5 with the cylindrical wall 8 (Fig. 2) is suited for cryogenic containers with a wide neck tube, which feature a higher liquid nitrogen evaporation rate, while the cap 5 with the conical wall 8 (Fig. 1) is quite suitable for cryogenic containers with a smaller neck and a lower refrigerant evaporation rate.

It is relevant to note in this connection that the diameter of the neck tube 3 of the container is defined by the dimensions of the holders to receive a biological product which are to be placed in the container.

Fig. 3 illustrates an embodiment of the cryogenic container, wherein the side wall 8 of the cap 5 has the configuration of a surface of revolution having a convex generatrix. Such a configuration of the side wall 8, like the cylindrical one, is quite suitable for containers with a wide neck tube 3 and a higher refrigerant evaporation rate. It is to be noted that increasing the convexity of the side wall 8 extends the time of contact of the refrigerant vapours with the portion "M" of the surface of the jacket 1 (Fig. 1) and thereby decreases the heat inflow into the cryogenic container.

For narrow-neck tube cryogenic containers featuring a relatively low rate of refrigerant evaporation, the side wall 8 of the cap 5 preferably has the configuration of a surface of revolution having a concave generatrix (Fig. 4). Such a configuration of the side wall 8 ensures an undisturbed laminar flow of the refrigerant vapours over the surface of the jacket 1 from the passage 7 to the clearance 9.

The following should thus be taken into account in selecting the configuration of the side wall 8 of the cap 5. First, the refrigerant evaporation rate rises with increasing the diameter of the neck tube 5.

Second, changing the configuration of the side wall 8 of the cap 5 in the sequence, such as, a surface with a concave generatrix, a conical surface, a cylindrical surface, and a surface with a convex generatrix results in decreasing of the refrigerant evaporation rate respectively.

It will be apparent to those skilled in the art that the embodiments of the side wall 8 of the cap 5, defining the profile of the annular chamber 10, which are shown in Figs. 1 through 4 do not exhaust all the possible modifications of this profile.

In Figs. 1 through 4, the cap 5 and the plug 6 are two separately fabricated parts. Such a construction is simple in manufacture but not the only possible one.

Thus, Fig. 5 illustrates an embodiment of the cryogenic container, wherein the cap and the plug are an integral part 5 whose portion 5a serves as the cap, whereas its portion 5b is the plug. It is quite clear that it is reasonable to fabricate the part 5, like the plug 6 (Figs. 1 through 4), of foam plastic or some other suitable heat-insulating material in order to decrease the heat inflow into the container.

Due to diminishing the refrigerant evaporation rate, provided by the proposed cryogenic container, the period of storing a biological product therein is substantially extended. Thus, this period, which is conditioned by the evaporation time of the refrigerant for one supply thereof, for the cattle semen is of up to 130 days.

While particular embodiments of the invention have been shown and described, various modifications thereof will be apparent to those skilled in the art.

Various other modifications may be made in the invention without departing from its spirit and scope as defined in the claims.

Claims

1. A cryogenic container comprising a jacket, a heat-insulated vessel for the refrigerant, disposed within the jacket and provided with a neck tube joining the vessel with the jacket, and a cap with a plug made of a heat-insulating material and fitted in the neck tube so that between the plug and the neck tube there is a passage for the refrigerant vapours to escape, the cap having a side wall which envelops with a clearance a portion of the jacket surface adjacent to the neck tube, and jointly with said jacket surface forms an annular chamber communicating both with the atmosphere through the clearance and with the passage for the refrigerant vapours, so that the refrigerant vapours flow into the chamber to cool the jacket surface portion enveloped by the cap.

2. A cryogenic container in accordance with claim 1, wherein the area of the jacket surface enveloped by the side wall of the cap constitutes from 2 to 7 percent of the total jacket surface area.

3. A cryogenic container in accordance with claim 1 or 2, wherein the cap envelops the jacket with a clearance whose cross-sectional area does not exceed the cross-sectional area of the passage for escape of the refrigerant vapours.

4. A cryogenic container substantially as hereinbefore described and as illustrated in the accompanying drawings.