US2188475A - Evaporator for refrigeration systems - Google Patents

Description

J. HEINRICH 2,188,475

EVAPORA'IOR FORREFRIGERATION SYSTEMS Filed Feb. 15, 1938 2 Sheets-Sheetl Jan. 30, 1940.

: INVENTOR I JO'HANN HEINRICH ATTORNEYS J. HEINRICH 2,188,475

EVAPORATOR FOR REFRIGERATION SYSTEMS Jm so, 1940;

' Filed Feb. 15, 19:53 2 She'ets-She et 2' INVENTOR J "HANN HE/NEsCH Patented Jan. 30, 1940.

PATENT oFFlcs EVAPORATOR FOB REFRIGERATION SYSTEMS Johann Heinrich, Berlin- 'legel, Germany, as-

signor to Rheinmetail-Borsig Aktiengesellq schaft Werk- Borsig Berlin-Tegel, Beriin-Tegel, Germany, a corporation of Germany Application February 15, 1938. Serial No. 190,663

Germany February 15, 1937 1 Claim. (01. 02-12 This invention relates to refrigeration systems and refers more particularly to an evaporator used in such systems for the purpose of evaporating a cooling medium and causing a circulation thereof. 7

In prior art so-called flooded evaporators are often used as heat exchangers, such evaporators consisting of two cylinders situated one above the other and interconnected by short vertical or bent pipes. Bubbles rising in the cooling liquid situated in these evaporators stir a part of this liquid and cause it to circulate. However, the natural circulation of the cooling medium drops with a drop in temperature and stops for all practical purposes as soon as the saturation 7 pressure is within the vacuum range. The cocompressor chamber receiving the sucked-in gas eii'icient of heat transmission drops correspondingly and in order to cool the carrier of cold sufficiently it is necessary to operate with great differences in temperature between the cooling medium and the carrier of cold.

If, for example, ammonia is used as the cooling medium and if such ammonia should evaporate at a temperature of*-60 C. which corresponds to a saturation pressure of 0.223 absolute atmosphere, then the upper level of the cooling medium situated in a flooded evaporator which is about 1500' millimeters high, must have a temperature of C. and a pressure of 0.11 absolute atmosphere, in order that there should be a formation of vapor in the lower part of the heat exchanger and that the vapor bubbles should be able to overcome the static pressure of the column of liquid situated in the evaporator.

The disadvantage of such cooling systems is that it is necessary to increase the volume of the by about corresponding to an increase in the specific volume of ammonia. On the other hand, if the pressure of liquefaction be assumed to be 12 absolute atmospheres, the ratio of compression rises' from 1:54 to 1:108. This increase in the volume of the compressor chamber and -the ratio of compression makes it necessary to construct a very large condensation plant consisting of several stages, the size of which is considerably out of proportion to its output. It is possible to avoid the necessity of using such expensive condensation plants, but then the heat exchanging surfaces must be very large and such large heat exchange surfaces require a large amount of space and again increase the costs of manufacture and installation to a considerable extent.

An object of the present invention is the provision of an evaporator for cooling systems by showing by way of example a preferred embodiment of the inventive idea. 7

means of which the described disadvantages may be avoided, and which is comparatively inexpensive in manufacture and eflicient in operation.

Another object is the provision of a cooling system which will operate eifectively and at low 5 cost without requiring the use of a large condensation plant, large heat exchange surfaces, or an injector pump for circulating the cooling medium.

Other objects of the invention will be apparent 10 in the course of the following specification.

The objects of the presentinvention may be realized through the provision of a mechanically driven pump which causes the circulation of the liquid qooling medium situated in flooded evaporators. This pump is particularly useful in systems operating with low temperatures and serves the purpose of creating an advantageous exchange of heat. The pump is preferably built into the collecting pipe or container of the heat exchanger and is driven by a regulatable motor.

The invention will appear more clearly from thefollowing detailed description when taken in connection with the accompanying drawings In the drawings:

Figure 1 shows a device constructed in accor ance with the principles of the present invention, in front elevation and partly in section:

Figure 2 is a horizontal section along the line 2-2 of Figure 1; and

Figure 3 is a vertical section through the device along the line 33 of Figure 2.

The heat exchanger shown in the drawings comprises a cylindrical collecting pipe or container l which is partly filled with a liquid medium 5, such as ammonia. The outer cylindrical surfaces of the container! carry a large number of pipes 6 to IE. Each of these pipes has substantially the form of a loop and the two ends of each pipe are in communication with theinterior of the container I. .As shown in Figures -1 and 2, the pipes are disposed substantially vertically, the upper end of each pipe being attached to the container 1 at substantially the upper portion thereof, while the lower end of each pipe is situated underneath its upper end and is attached to the lower portion of the container 4.

A second container l6 constituting a condensation chamber is situated adjacent the container l and is in communication with the latter by means of two pipes l1 and I8. The'pipe I I is narrower than the pipe l8 and leads to the bottom of the container IS. The wider pipe I8 is $5 connected with the container l8 at substantially the middle thereof and is attached to the container 4 close to the top thereof. A connecting branch I9 is carried by the container i 6 and is situated close to the bottom thereof, while a second connecting branch is carried by the top portion of the container I6.

The pump 2| situated within the container 4, comprises a propeller 22 which is immersed in the cooling medium 5 and which is carried by a vertical shaft 23. The upper end of the shaft 23 may constitute the driving shaft of the motor 24 or be firmly connected therewith. The motor 24 is situated above the container 4 and is provided with a regulator used for the purpose of varying its speed of rotation.

As shown in Figure l, the container 4 operates as a .floodedevaporator, being only about half filled with the cooling medium 5, and the pipes 6 to l5 are consequently also filled with the liquid cooling medium to about one half or somewhat over one half.

Ammonia which is used as the cooling medium is first introduced through the connecting branch i9 into the container l6 and then flows through the pipe I'I into the container 4, filling the container 4 and the pipes connected therewith to about one half.

As soon as the motor 24 is switched on, it actuates the pump 2| causing a circulation of the fiuid in the direction of the arrows shown in Figure 3, namely, the cooling medium is pressed into the lower portions of the pipes 6 to I5, which are situated underneath the propeller 22, and is circulated therethrough, returning to the container 4 through the upper ends of these pipes,

which aresituated above the propeller 22.

That portion of the cooling medium, which still remains in the liquid state, is separated to a large'extent from the gas particles in the container 4; The liquid particles return to the main body of theliquid within the container 4. The gaseous portion of the cooling medium flows through the pipe l8 into the container l6 and the remaining liquid particles drop to the bottom of the container l6 and flow through the pipe I! back to the container 4. The gas is sucked through the branch 20 into a compressor which may be of the standard type and which is not shown in the drawings.

Due to the provision of the regulator 25, the speed of the motor 24 may be varied at will and may be adjusted to vary the amount of the circulated cooling medium and, consequently, the output of the cooling system.

It is apparent that the specific illustration shown above has been given by way of illustration and not by way of limitation, and that the structures above described are subject to wide variations and modifications without departing from. the scope of the invention. All of such variations and modifications are to be included within the scope of the present invention.

What is claimed is:

In a refrigeration system, a substantially vertical container adapted to contain a cooling medium, a plurality of pipes communicating with the interior of said container and having upper ends connected to the upper portion of said container and lower ends connected to the lower portion of said container, a regulatable pump situated within said container substantially between the upper portion and the lower portion thereof, another. container, means interconnecting the two containers and providing for flow of a liquid cooling medium from the secondmentioned container to the first-mentioned container and of a gaseous cooling medium from the first-mentioned container to the secondmentioned container, means connected with the second-mentioned container for introducing the liquid cooling medium thereinto, and means connected with the second-mentioned container for removing the gaseous cooling medium therefroml J OHANN HEINRICH.

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