Device for expansion of liquefied gases

A device for expansion of liquefied gases, whereby the liquefied gases are used, for instance, as refrigerants for cooling a freezing room. For even distribution of the expanded refrigerant, the liquefied gas is supplied to expansion openings which are arranged inside a cold gas supply pipe. The cold gas supply pipe has an ejector bore hole for aspiration of secondary atmosphere into the cold gas supply pipe. In this way, the expanded refrigerant is finely distributed in the cold gas supply pipe and is mixed with secondary atmosphere.

BACKGROUND OF THE INVENTION 
The present invention relates to a device for expansion of a liquefied gas 
having liquefied gas piping and at least one connected expansion opening. 
For cooling of freezing materials such as food-stuffs, synthetics, etc., or 
for freezing out pollutants, during exhaust gas purification, for example, 
multiple liquefied gases are used as refrigerants which are usually stored 
in a pressure vessel and expanded for cooling or freezing. 
DE-PS 28 17 454 describes an arrangement for rapid freezing of liquid or 
solid foodstuffs, in which liquid carbon dioxide is fed into a container 
and expanded at the end of the tubing. This expansion causes carbon 
dioxide snow, from which a bed of carbon dioxide snow particles is 
produced in the container by stirring. The foodstuff is then introduced 
into the container and brought into contact with the carbon dioxide snow 
by stirring. 
Furthermore, it is known from U.S. Pat. No. 3,214,928 to feed the 
foodstuffs past nozzles which spray them with liquid carbon dioxide, which 
then hardens into flakes of carbon dioxide snow. 
The known arrangements for expansion of liquefied gases are disadvantaged 
in that even distribution of the expanded refrigerant can be achieved only 
through use of expensive construction. Besides, when the liquefied gas 
supply is turned off, plant components may become clogged by icing over. 
When the liquefied gas supply is switched on again, this clogging results 
in uneven distribution of the expanded refrigerant. 
SUMMARY OF THE INVENTION 
An object of the present invention is therefore to provide a device of the 
type initially nominated in such a way that expanded refrigerant is made 
available to meet demands in an economical reliable way. 
This is achieved according to the present invention by the expansion 
opening being arranged inside a cold gas supply pipe which has at least 
one ejector bore hole in the vicinity of the expansion opening for 
aspirating secondary atmosphere into the cold gas supply pipe. 
The expansion opening is arranged preferably in the center of gravity of 
the cold gas supply pipe. In order to achieve jet expansion of the 
generated stream of refrigerant, the cold gas supply pipe has a lateral 
groove advantageously on each of its ends. 
The liquefied gas flows through the liquefied gas piping to the expansion 
opening or to the expansion openings where the stream of liquefied gas is 
expanded under the triple point of the liquefied gas against the 
atmosphere inside the cold gas supply pipe. Because of the ejector bore 
hole in the cold gas supply pipe, the device works as an ejector which 
draws secondary atmosphere into the cold gas supply pipe, finely diffuses 
the refrigerant produced by expansion and relays it to the consumer, a 
cold room or freezing room, for example. When liquid carbon dioxide is 
used, it becomes a question of carbon dioxide snow and carbon dioxide cold 
gas in the case of expanded refrigerant. The carbon dioxide snow is 
distributed finely in the cold gas supply pipe and mixed with the carbon 
dioxide cold gas as well as the aspirated secondary atmosphere. The 
resulting two-phase mixture is distributed evenly to the cold room or 
freezing room. In this way extremely fine atomization of the refrigerant 
is possible, as is its even distribution. The refrigerant can thus be 
supplied on demand to the consumer, that is, to the product to be cooled. 
No areas of the product are frozen excessively or insufficiently. 
In order to avoid uneven distribution of the refrigerant as a result of 
clogging, it is proposed according to a further development of the 
inventive concept of the present invention that the liquefied gas piping 
is connected with a flow divider which divides the liquefied gas flow into 
two branch lines, whereby one branch line ends in a gas pressure storage 
tank, while the other branch line has the expansion opening for expansion 
of the liquefied gas. 
The outcome of this arrangement is that the gas pressure storage tank is 
loaded when the liquid gas supply is switched on, while simultaneously 
liquid gas is supplied to the expansion openings for expansion purposes. 
After the liquid gas supply is switched off, the gas pressure storage 
tank, according to its storage capacity, ensures that the liquid gas still 
present in the branch line leading to the expansion openings is maintained 
in a pressure range above the triple point of the liquid gas until the 
liquid gas piping is completely emptied. This effectively prevents 
clogging of the expansion bore holes by carbon dioxide snow. 
The gas pressure storage tank preferably has a gilled-pipe evaporator. 
Thus, sufficient pressure can be built up in the gas pressure storage tank 
without considerable expense on apparatus, in order to maintain the liquid 
gas above the triple point after switching off of the liquid gas supply. 
So as to ensure maintaining the necessary pressure, a pressure gauge is 
usefully provided, connected to the gas pressure storage tank. A magnetic 
valve is used preferably to switch the liquid gas supply on and off and is 
arranged in the liquid gas piping upstream of the flow divider. 
With the device according to the present invention it is possible for 
expanded refrigerant to be made available according to demand at any time 
and without considerable expense on apparatus. Switching off the liquid 
gas supply at times when no refrigerant is required leads to clogging of 
nozzle holes, guaranteeing supply of the refrigeration plant with expanded 
refrigerant after the liquid gas supply is switched on again. 
According to an especially preferred embodiment the liquid gas piping is 
installed for the most part inside the room to be cooled, that is when the 
invention is used in cold rooms or freezing rooms inside the cold room or 
freezing room, so as to minimize heat loss. By way of example, the liquid 
gas tank can be housed inside the cold room or freezing room or directly 
next to the cold room or freezing room, whereby as short as possible 
supply is provided from the liquid gas tank to the cold room or freezing 
room. 
To prevent malfunctions due to condensation, it is further proposed to 
arrange beneath those installation components located outside the cold 
room or freezing room a condensation collecting chamber which has a 
condensation discharge pipe for drawing off condensation. 
With the device according to the present invention optimization of the 
refrigeration supply is achieved, especially with the use of liquefied 
carbon dioxide. Whereas with conventional devices for expansion of 
liquefied carbon dioxide the problem of clogging by carbon dioxide snow 
may arise, the device according to the present invention enables 
trouble-free periodic or continuous operation. The device is space-saving 
and manages by using commercial components. Furthermore, assembly and 
repairs are made easy. Altogether, the invention offers an economical and 
reliable expansion device which can make available expanded refrigerant at 
any time according to demand. 
The device according to the present invention is suited to expansion and 
distribution of all imaginable liquefied gases, such as liquid nitrogen, 
liquid oxygen, liquid hydrogen, and the like. The greatest advantages of 
the present invention involves the use of liquid carbon dioxide, as here 
what matters is reliable prevention of clogging by carbon dioxide snow and 
even distribution of the carbon dioxide snow and gaseous carbon dioxide as 
refrigerant. With the device according to the present invention, these 
problems are solved smoothly and without considerable expense on 
apparatus. 
The device is provided for, among others, cold gas purging, such as of 
foodstuffs. Use of a cold gas/air mixture, in cold rooms or freezing 
rooms, for example, is also possible. The invention is also suitable for 
precipitation of pollutants from waste gas. Here, the waste gases are fed 
through a freezing room impacted by means of the expansion device 
according to the present invention with carbon dioxide cold gas and carbon 
dioxide snow particles. The pollutants freeze out from the waste gas and 
can be separated from the waste gas as solids, for example, by means of a 
cyclone. It is also possible to introduce expanded liquid gas, especially 
gaseous carbon dioxide and carbon dioxide snow, to fluids or particle mass 
flows for mass and/or energy transfer. Altogether, the invention offers a 
wide spectrum of use in environmental and pollution abatement technology, 
as well as in refrigeration technology.

DETAILED DESCRIPTION 
The expansion device illustrated in the Figure is provided for cooling of a 
freezing room by means of carbon dioxide snow and carbon dioxide cold gas. 
Foodstuffs may be deep-frozen in the freezing room or enclosure, for 
example. The diagram illustrates only part of the freezing room ceiling 1. 
Introduced into a recess of the freezing room ceiling 1 is a grommet 2 
which accommodates the expansion device. The expansion device is supplied 
with liquid carbon dioxide by a liquid gas pipe 3. The liquid carbon 
dioxide is stored in a liquid gas tank, not illustrated in the Figure, 
which is accommodated directly next to the freezing room. The liquid gas 
tank is connected by way of a supply pipe to the inside of the freezing 
room. The liquid gas pipe 3 is connected inside the freezing room to this 
supply pipe coming from the liquid gas tank and is displaced for the most 
part inside the freezing room to reduce heat loss. The liquid gas pipe 3 
which provides a liquid conveying line, passes through the grommet 2 and 
terminates in a magnetic valve 4 arranged above the grommet 2, in a liquid 
gas storage tank 16. The liquid gas supply can be regulated by the 
magnetic valve 4 according to the prevailing refrigerant demand. The 
magnetic valve 4 is connected to a flow divider 5 which divides the liquid 
gas flow into two branch lines 6 and 7. The branch line 6 leads to a gas 
pressure storage tank 8, while the branch line or supply line 7 enters the 
interior of the freezing room through the grommet 2. 
Located at the end of the branch line 7 are several expansion bore holes 9, 
through which expanded carbon dioxide expands for forming carbon dioxide 
snow and cold carbon dioxide gas. The expansion bore holes 9 are located 
in the center of gravity of a cold gas supply pipe 10 open on both sides. 
In the vicinity of the expansion bore holes 9, an ejector bore 11 is 
positioned in the cold gas supply pipe 10, through which secondary 
atmosphere is aspirated from the freezing room. The cold gas supply pipe 
10 has on both of its ends a lateral groove 17 for jet expansion of the 
carbon dioxide snow and cold gas stream. 
The gas pressure storage tank 8 is equipped with a gilled-pipe evaporator. 
With this in place, a preselected system pressure can be produced and 
maintained without considerable expense on apparatus by evaporation of the 
liquid carbon dioxide supplied to the gas pressure storage tank 8. For 
monitoring of the system pressure, the gas pressure storage tank 8 has a 
pressure gauge 12. The gas pressure storage tank 8 ensures that, after 
switching off of the liquid gas supply by closing of the magnetic valve 4, 
the liquid carbon dioxide is held in the branch line 7 in a pressure range 
above the triple point of carbon dioxide until it is completely emptied, 
whereby formation of solid carbon dioxide in the branch line 7 is avoided, 
as is resulting clogging of the expansion bore holes 9. Variations in 
pressure can be compensated for with the gas pressure storage tank 8, 
constantly guaranteeing the required expansion pressure. 
A condensation collecting chamber 13 is embedded in the grommet 2 which 
receives the condensation from the installation components arranged above 
the freezing room ceiling 1. The condensation collecting chamber 13 has a 
condensation discharge pipe 14 with a siphon stopper 15. 
The operational method of the device is as follows: 
After the magnetic valve 4 is opened, liquid carbon dioxide, according to 
the pressure in the installation, flows through the flow divider 5 and the 
branch line 7 to the expansion bore holes 9, by which the carbon dioxide 
liquid stream is expanded under the triple point of carbon dioxide (5.18 
bar) toward the atmosphere inside the cold gas supply pipe 10. By means of 
this process, arrangement and configuration of the cold gas supply pipe 
10, the device works as an aspirator which draws secondary atmosphere 
through the accordingly arranged ejector bore 11 in from the freezing 
room, finely distributes the carbon dioxide snow produced by expansion and 
releases it into the freezing room with the carbon dioxide gas constituent 
as a two-phase mixture of ca. -78.degree. C. At the same time the gas 
pressure storage tank 8 is loaded as the magnetic valve 4 opens. After the 
magnetic valve 4 is closed, the gas pressure storage tank 8 maintains the 
liquid carbon dioxide in the branch line 7 according to its storage 
capacity in a pressure range above the triple point of the carbon dioxide 
until the liquid gas pipe 3 is completely emptied. This effectively avoids 
any build-up of carbon dioxide snow in the branch line 7, preventing 
clogging of the expansion bore holes, guaranteeing even distribution of 
the refrigerant after the magnetic valve 4 is reopened. 
Without further elaboration, it is believed that one skilled in the art 
can, using the preceding description, utilize the present invention to its 
fullest extent. The following preferred specific embodiments are, 
therefore, to be construed as merely illustrative, and not limitative of 
the remainder of the disclosure in any way whatsoever. 
In the foregoing, all temperatures are set forth uncorrected in degrees 
Celsius and unless otherwise indicated, all parts and percentages are by 
weight. 
The entire disclosure of all applications, patents and publications, cited 
above, and of corresponding German application P 40 34 076.7, are hereby 
incorporated by reference. 
From the foregoing description, one skilled in the art can easily ascertain 
the essential characteristics of this invention, and without departing 
from the spirit and scope thereof, can make various changes and 
modifications of the invention to adapt it to various usages and 
conditions.