US3363430A

US3363430A - Refrigeration system with auxiliary condensing means

Info

Publication number: US3363430A
Application number: US489470A
Authority: US
Inventors: Elizabeth C White
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-09-21
Filing date: 1965-09-21
Publication date: 1968-01-16
Anticipated expiration: 1985-01-16

Description

United States Patent T 3,363,430 REFRIiGERATION SYSTEM WITH AUXHJARY CONDENSING MEANS Clarence E. White, deceased, late of Gurnee, Ill., by Elizabeth C. White, executrix, 4371 Birch Road, Gurnee, Ill. 60031 Filed Sept. 21, 1965, Ser. No. 489,470 11 Claims. (Cl. 62183) ABSTRACT OF THE DISCLOSURE This disclosure relates to a refrigeration system including a single compressor and two isolated refrigerant flow paths. The compressor is connected in series with one of the flow paths, which includes a counterflow condenser and one or more evaporation coils. The other refrigerant flow path includes a different conduit in the counterflow condenser, and is connected in series with a receiving chamber at about the same elevation as the condenser, and a second condenser placed above the elevation of the first condenser. The flow of refrigerant in the other flow path is brought about entirely by thermal means, so that no compressor is required in this flow path. In a multiple system, including a plurality of compressors for delivering flows of refrigerant to a plurality of refrigeration units, a separate counterflow condenser is provided for each of the compressors and the isolated conduits in all of the condensers are connected in parallel with each other and in series with a receiving chamber and an additional condenser disposed above the level of the condensers connected with the compressors.

This invention relates to refrigeration systems and particularly to refrigeration systems having a plurality of refrigeration units which are to be maintained at a relatively low temperature.

it has been known in the prior art to employ systems known as cascade refrigeration systems. In a cascade system, a condenser in a primary refrigerant flow path is cooled by the refrigerant in a secondary refrigerant flow path. However, in such a system, a relatively large compressor is required in the secondary refrigerant flow path, in addition to a compressor in the primary line in circuit with one or more refrigeration units. As a result, such systems have proven relatively costly and have generally been economical only for very low temperature applications such as, for example, freezing carbon dioxide and the like.

In applications involving a number of different refrigeration units, it has been customary to provide a plurality of separate refrigerant flows, each having its own individual compressor and condenser. The condensers are sometimes juxtaposed with each other in an air-cooled unit, mounted on the roof of a building, with a separate length of tubing connecting the air-cooled unit in circuit with each refrigeration unit. This necessitates a great deal of tubing, however, and it is desirable to find a way to reduce the expense of such a system.

Other approaches of the prior art have employed counterflow condensers for each separate refrigeration system, with a stream of constant temperature fluid flowing through one conduit of each counterflow condenser. Typically, the constant temperature fluid has been tap water, which is discarded to a drain after being heated in the condenser. The water, used only once in such a system, amounts to a considerable expense, and it is also necessary to clean the condensers frequently of the deposits and residues left there by the tap water. The cleaning operation thus required is time consuming and difficult, and adds to the expense of operating the system.

3,363,430 Patented Jan. 16, 1968 The present invention has for its principal object, the provision of a refrigeration system which is substantially less expensive to construct and operate than prior art systems.

Another object of the present invention is to provide a refrigeration system which achieves greater efliciency than prior art systems.

A further object of the present invention is to provide a refrigeration system in which frequent cleaning of the condenser is unnecessary.

Another object of the present invention is to provide a system employing a plurality of different refrigerants for each of the individual refrigeration units, and yet permit the use of another, different, refrigerant for the secondary condensing flow path, such that the different refrigeration units may be operated at different temperatures, and the most efficient refrigerant may be used in each case.

A further object of the present invention is to provide a refrigeration system in which the condenser temperature is held constant.

Other objects and advantages of the present invention will become manifest by an examination of the following description and the appended drawings.

In one embodiment of the present invention, there is provided a plurality of refrigeration units connected in series with individual compressors and condensers, each in a primary refrigerant flow path, and a secondary refrigerant flow path, including a secondary condenser in which the secondary refrigerant is circulated solely by a heat differential generated by heat extracted from a refrigeration unit associated with the primary flow path. Each primary flow path includes one conduit of an individual counterflow condenser, while the other conduit of the counterflow condenser is connected in circuit with the secondary refrigerant flow path. The secondary flow path includes an air-cooled condenser, which may be conveniently mounted on the roof of a building, and a refrigerant receiving chamber. The refrigerant receiving chamber and the counterflow condenser are positioned in relation to each other so as to cause the secondary refrigerant to flow through the secondary flow path under the influence of the temperature difference caused by the heating of the secondary refrigerant in the condenser.

Reference will now be made to the accompanying drawings in which:

FIG. 1 is a schematic diagram, partly in section of a refrigeration system incorporating the present invention; and

FIG. 2 is a functional block diagram, in simplified form, of a refrigeration system embodying the present invention.

Referring now to the drawings, there is illustrated a compressor 10 which is adapted to compress a refrigerant and conduct the same to a line 12. The line 12 is connected to one conduit 13 of a pair of

coaxial conduits

13 and 30 of a counterflow condenser 14. The other end of the conduit 13 is connected to a receiver 16 by a line 18, whereby refrigerant in its liquid state, after having been condensed in the condenser 14, may be stored.

The output of the receiver 16 is connected to a line 20, which extends from the receiver 16 to an expansion valve 22 located at the site of the refrigeration unit. The output of the expansion valve is connected to a line 24 which extends to one end of a refrigeration coil 26, Where the refrigerant is permitted to expand to its gaseous state within the coil 26, thereby cooling the coil. The other end of the coil 26 is connected by a line back to the compressor 10. There is thus formed a complete circuit for refrigerant which flows in succession from compressor 10 through the counterflow condenser 14, the receiver 16, the expansion valve 22, and the cooling coil 26. This circuit will hereinafter be referred to as the primary flow path, and the refrigerant employed in this path as the primary refrigerant. The primary refrigerant is chosen for efficient operation within the primary flow path, taking into consideration the desired temperature of the cooling coil 26, in addition to the capacities of the compressor and the counterflow condenser 14.

The other conduit 3f! within the counterfiow condenser 14 is coaxial with the conduit 13, and is connected in a series path which hereinafter will be referred to as the secondary flow path. The secondary refrigerant is heated in the condenser 14 and thereby vaporized. The gaseous secondary refrigerant passes through a line 32 connected to the end of the conduit 30, and conducts the gas to the upper portion of an air-cooled condenser 34 which is disposed at some remote location, preferably on the roof of the building housing the refrigeration system. The outlet of the air-cooled condenser 34 is connected to a line 36 which extends to a refrigerant receiver chamber 38 disposed near the counterflow condenser 14. The outlet of the refrigerant receiver chamber 38 is connected to a line 40, which is adapted to conduct secondary refrigerant to the lower end of the conduit 30 of the counterfl'ow condenser 14.

Thus, the secondary refrigerant flow path comprises a closed circuit in which the secondary refrigerant is adapted to flow in series through the counterflow condenser 14, the air-cooled condenser 34 and the refrigerant receiving chamber 38. The flow of the secondary refrigerant through the secondary flow path is sustained entirely by thermal action. There is a heat differential between the temperature of the refrigerant in the counterflow condenser 14 and in the refrigerant receiving chamber 33. The secondary refrigerant is vaporized in the counterfiow condenser 14, and condenses to its liquid state in the aircooled condenser 34, whereupon it returns to the refrigerant receiving chamber 3-8 in its liquid state, and establishes a fluid level 42 within the chamber 38. As will be more fully explained hereinafter, the fluid level 42 within the refrigerant receiving chamber 38 is higher in elevation than the fluid level 44 within the counterfiow condenser 14, so that the pressure differential between the fluid levels 42 and 44 causes the liquid refrigerant to flow from the receiving chamber 38 to the condenser 14 where it is vaporized.

Since the secondary flow path is a closed system, a constant quantity of refrigerant is contained therein, and there is an ascertainable relation between the pressure and the temperature at every location within the secondary system which approaches the theoretical relation for a vapor, with respect to that portion of the secondary flow path in which the refrigerant is in its vaporous state. The vaporous refrigerant is in the upper part of the secondary system, and the pressure within the lower portion of the secondary flow path is determined by the height of the liquid level within the chamber 38, and the pressure of the vaporous refrigerant in the upper portion of the secondary flow path. In operation, the vapor pressure is much greater than the pressure component due to the height of the liquid, but as the vapor pressure is nearly equal on both the condenser and receiver sides of the secondary system, the rate of flow within the system is due entirely to the difference in liquid height between the two sides of the secondary system.

The quantity of refrigerant included within the secondary refrigerant flow path is chosen so that in the condition of the system before the compressor 10 is initiated, when the counterfiow condenser 14 is at ambient or room temperature, part of the secondary refrigerant is in its gaseous state. When the compressor 10 is started, the temperature of the counterflow condenser 14 rises, and eventually, the temperature of the entire secondary system rises, and becomes nearly equal to the temperature of secondary refrigerant within the counterflow condenser, which is about 10 F. below the temperature of the primary refrigerant in the counterflow condenser. The increased heat applied to the secondary refrigerant by the counterflow condenser 14 operates to change the quality of the secondary refrigerant, i.e., change the proportion of the refrigerant in its liquid and vaporous states. The quantity of the refrigerant within the secondary system is chosen so that the liquid level 44 of the liquid state secondary refrigerant, at the operating temperature of the condenser, is within the counterflow condenser on one side of the secondary system, and the level 42 is within the receiving chamber on the other side. If the quantity of refrigerant is less than this amount, the refrigerant will be converted to its vaporous state near the bottom of the condenser 14, so that only the bottom coils of the condenser 14 is cooled by the secondary refrigerant. This will cause the condenser to become hotter than normal and result in an increased load on the primary system compressor.

The cross-sectional area of the receiving chamber 38 is made large relative to the other conduits within the system, so that the change in the quality of the secondary refrigerant during operation of the system has less effect on the fluid level 42 within the receiver 38. This construction brings about the advantageous result that the fluid level within the receiving chamber 38 is substantially independent of the operating temperature of the secondary system, so that substantially the same secondary system may be used over a wide variety of temperatures of the counterfiow condenser 14.

The cross-sectional area of the receiving chamber 38 is also preferably large relative to the effective horizontal cross-sectional area of the fluid in a horizontal section of the counterflow condenser 14. This latter area is much greater than the transverse cross section of the tubes of which the condenser 14 is formed, since the horizontal section intersects the tube at an acute angle. The actual value of this cross section thus depends not only on the interior diameter of the tube of the condenser 14, but also upon the diameter of the coil and the angle with respect to a horizontal plane at which the coiled tube is disposed. As long as the cross-sectional area of the receiving chamber 38, at the level 42, is larger than the area of the liquid within the condenser 14 at the level 44, the rate of change of the fluid level 42, at different operating conditions, is less than the rate of change of the fluid level 44. This tends to ensure that the pressure differential between the fluid levels 42 and 44, and consequently the rate of flow of the secondary refrigerant through the secondary flow path, is generally proportional to the quantity of secondary refrigerant vaporized in the condenser 14 during a unit time. The more heat transferred between the primary and secondary refrigerants within the condenser 14, the lower will be the level 44. As the level 42 is substantially constant, the pressure difference resulting from the difference in the levels 42 and 44 will increase with increasing heat transfer within the condenser 14, and bring about an increased rate of flow of secondary refrigerant through the secondary system. Thus, the rate of flow of secondary refrigerant increases with increasing heat transfer within the condenser 14, and tends to maintain the temperature of the condenser 14 constant for varying loads.

This operation produces the advantageous result of eliminating the need for excess compressor capacity, which is ordinarily required in systems which operate with condensers having operating temperatures which are dependent upon the primary system load.

The air-cooled condenser 34 has the function of condensing the secondary refrigerant, by giving up heat to the air. In order to ensure the effectiveness of the condenser, a pressure detector 43 is inserted in the line 32, and operates to energize a control device 45 to turn on a fan 46 when the pressure within the line 32 exceeds a 7 predetermined value corresponding to the desired operating pressure of the secondary flow path. If the pressure should exceed this value, the fan 46 is turned on, and improves the efiiciency of the condenser 34, to bring about a reduction in pressure to the desired level, after which the detector 42 de-energizes the fan 46. As long as the pressure of the secondary system does not exceed the desired level, however, the fan 46 is not required.

In FIG. 2, there is shown a schematic block diagram of a system employing a plurality of primary flow paths, each including a separate counterfiow condenser 48a, 48b and 48c. The inlet 50a, 50b and 500, and the

outlet

52a, 52b and 520 of each primary flow path is connected in the same manner as illustrated in FIG. 1, and the separate compressors and other equipment are not shown. Each of the condensers 48 includes one of a plurality of conduits 54a, 54b and 540, connected in parallel, and associated with a secondary refrigerant flow path including a series connected air-cooled condenser 56, and receiving chamber 58 similar to the condenser 34 and the receiving chamber 38 of FIG. 1. The flow of secondary refrigerant flowing through each of the counterfiow condensers 48a, 48b and 480 is dependent upon the amount of heat transfer taking place in it, and the amount of such flow may be different for each counterflow condenser. The cross-sectional area of the liquid level within the receiving chamber 58 is preferably greater than the combined areas of the liquid levels of the secondary refrigerant within all of the condensers 48a, 48b and 48c, for the same reasons as mentioned above in connection with the description of FIG. 1. Only one conduit 60 is required to convey all of t the secondary flows to the remotely located condenser 56, and a considerable savings in piping can be effected, as compared with other systems in which separate lines must be run from each individual primary system to an auxiliary condenser.

In the embodiment of FIG. 2, a different refrigerant may be employed for each primary system, depending on the individual requirements and specifications of each primary system. A fan similar to that illustrated in FIG. 1, actuated in response to the pressure on line 60 may also be employed with the system of FIG. 2.

In one specific embodiment of the present invention, the refrigerant in the single primary flow path was Freon- 12 and the refrigerant in the secondary fiow path was Freon-22. The temperature throughout the secondary system was between 92 F. and 96 F., and the temperature of the primary flow passing through the condenser 14 was 102. The rate of flow of the primary refrigerant was 50 lbs. per hour, and the rate of flow of the secondary refrigerant was about 40 lbs. per hour, representing a primary and secondary capacity, respectively, of 2400 B.t.u. per hour and 2900 B.t.u. per hour.

The primary flow path pursued a cycle of operation where at the input of the compressor the refrigerant was at approximately 22 F., a pressure of 37 p.s.i., and an enthalpy of 80 B.t.u. per hour, assuming zero enthalpy of saturated liquid at 40 F. The compressor increased the pressure and temperature of the refrigerant to 136 p.s.i. at 102 F., with an enthalpy of about 90 B.t.u. per pound, following a constant entropy line. The condenser 14 maintained substantially the same temperature and pressure, and condensed the vapor to substantially a saturated liquid, having an enthalpy of about 32 B.t.u. per pound. The expansion valve 22 decreased the temperature to 22 F. and a pressure of 37 p.s.i. along a constant enthalpy line, and the refrigeration unit 26 increased the enthalpy to 80 B.t.u. per pound at constant temperature and pressure.

In the secondary flow path, the secondary refrigerant started between 92 F. and 96 F., at a pressure of about 200 p.s.i. and an enthalpy of 38 B.t.u. per pound. In the counterfiow condenser 14, substantially the same temperature and pressure are maintained, and the enthalpy is increased to 112 B.t.u. per pound. In the secondary condenser 34, the same temperature and pressure again are 6 maintained, and the enthalpy is decreased to 38 B.t.u. per pound to arrive back at the condenser 14. There is very little sensible heat gain in the secondary flow path, being limited to between 4 F. to 6 F.

By the above description, the present invention has been described with suflicient particularity as to enable others skilled in the art to make and use the same and, by applying current knowledge, to adapt the same for use under varying conditions of service without departing from the essential features of novelty thereof, which are intended to be defined and secured by the appending claims.

What is claimed is:

1. In a refrigeration system including a compressor and a refrigeration unit connected in series with a first flow path of a first condenser, the combination comprising a second condenser, a refrigerant receiving chamber, and conduit means connecting said second condenser and said receiving chamber in series with a second flow path of said first condenser, said first and second flow paths being independent and each containing a quantity of refrigerant, said second condenser being disposed at an elevation above said first condenser, and said receiving chamber being disposed at about the same elevation as said first condenser and having an internal horizontal cross-sectional area exceeding the internal cross-sectional area of said conduit means, refrigerant being recirculated within said second flow path entirely by thermal means.

2. Apparatus according to claim 1, wherein said first condenser and said second condenser both have vertically disposed inlet and outlet ports and said conduit means interconnecting the upper ports of said condensers and interconnecting the lower ports of said condensers through said refrigerant receiving chamber.

3. In a refrigeration system including a compressor and a refrigeration unit connected in series with a first flow path of a first condenser, the combination comprising a second condenser, a refrigerant receiving chamber, and conduit means connecting said second condenser and said receiving chamber in series with a second flow path of said first condenser, said first and second flow paths being independent and each containing a quantity of refrigerant, said second condenser being disposed at an elevation above said first condenser, and said receiving chamber being disposed at about the same elevation as said first condenser and having an internal horizontal cross-sectional area exceeding the internal horizontal cross-sectional area of said second flow path of said first condenser.

4. In a refrigeration system including a compressor and a refrigeration unit connected in series with a first flow path of a first condenser, the combination comprising a second condenser, a refrigeration receiving chamher, and conduit means connecting said second condenser and said receiving chamber in series with a second flow path of said first condenser, said first and second flow paths being independent and each containing a quantity of refrigerant, said second condenser comprising an air-cooled condenser disposed at an elevation above said first condenser, fan means for directing air past said second condenser, control means energizing said fan means in response to a predetermined pressure within said conduit means, said first condenser being operative to vaporize refrigerant within said second flow pat-h and said second condenser being operative to condense refrigerant within said second fiow path, whereby said refrigerant within said second flow path is recirculated.

5. In a refrigeration system including a compressor and a refrigeration unit connected in series with a first flow path of a first, counterflow condenser, the combination comprising a second condenser and a refrigerant receiving chamber connected in series with a second flow path of said first condenser, said receiving chamber being disposed at about the same elevation as said first condenser and said second condenser being disposed at an elevation above said first condenser, said first and second flow paths being independent and each containing a quantity of refrigerant, whereby heat is transferred from refrigerant in said first flow path to refrigerant in said second flow path, thereby vaporizing the refrigerant in second flow path and condensing the refrigerant in said first flow path, the refrigerant within said second flow path having a first interface between its liquid and vapor states within said second flow path of said first condenser, and having a second interface between its liquid and vapor states within said receiving chamber at an elevation above said first interface, whereby there is created a pressure differential resulting in recirculation of refrigerant within said second flow path.

6. A refrigeration system comprising a plurality of refrigeration units, a plurality of compressors, one for each of said units, a plurality of first condensers, one for each of said units, each of said first condensers having a first flow path, means connecting said first flow path of each of said first condensers in series with a refrigeration unit and a compressor, each of said first condensers having a second flow path independent of said first flow path and disposed in heat exchanging relation therewith, means connecting the second flow paths of all of said first condensers in parallel, said first and second flow paths each containing a quantity of refrigerant, means connecting said second flow path in series with a second condenser and a refrigerant receiving chamber, all of said first condensers being disposed at about the same elevation, said second condenser being disposed at an elevation above said first condensers, and said receiving chamber being disposed at about the same elevation as said first condensers.

7. A refrigeration system comprising a plurality of refrigeration units, a plurality of compressors, one for each of said units, a plurality of first condensers, one for each of said units, each of said first condensers having a first flow pat-h containing a quantity of refrigerant, means connecting one of said first flow paths in series with a refrigeration unit and a compressor to support a flow of refrigerant therethrough, each of said first condensers having a second flow path, containing a quantity of refrigerant, in heat exchanging relation with said first flow path, a second condenser, and a refrigerant receiving chamber, conduit means for connecting all of said second flow paths in circuit with said second condenser and said refrigerant receiving chamber, said second condenser being disposed at an elevation above said first condensers, and said receiving chamber having a horizontal internal cross-sectional area greater than the internal cross section of said conduit, refrigerant being recirculated within said second flow path entirely by thermal means.

8. A refrigeration system comprising a plurality of refrigeration units, a plurality of compressors, one for each of said units, a plurality of first condensers, one for each of said units, each having a first flow path containing a quantity of refrigerant, means connecting said first flow path in series with one of said refrigeration units and one of said compressors to support a flow of refrigerant therethrough, each of said first condensers having a secondary flow path, containing a quantity of refrigerant, in heat exchanging relation with said first flow path, a second condenser, and a refrigerant receiving chamber, means for connecting said second flow paths in circuit with said second condenser and said refrigerant receiving chamber, said second condenser being disposed at an elevation above said first condenser, and said receiving chamber being disposed at about the same elevation as all of said first condensers, and having a horizontal internal cross-sectional area exceeding the horizontal internal cross-sectional area of said second flow path of any of said first condensers.

9. Apparatus according to claim 8 wherein the horizontal internal crosssectional area of said receiving chamber exceeds the total horizontal internal cross-sectional area of all of said first flow paths of said first condensers.

10. A refrigeration system comprising a plurality of refrigeration units, a plurality of compressors, one for each of said units, a plurality of first condensers, one for each of said units, each having a first flow path, containing a quantity of refrigerant, means connecting said first fiow path in series with one of said refrigeration units and one of said compressors to support a flow of refrigerant therethrough, each of said first condensers having a second flow path, containing a quantity of refrigerant, in heat exchanging relation with said first fiow path, a second condenser, a refrigerant receiving chamber, conduit means for connecting said second flow paths in parallel with each other and in series with said second condenser and said refrigerant receiving chamber, said second condenser being disposed at an elevation above said first condensers, said receiving chamber being disposed at about the same elevation as said first condensers, fan means for passing air over said second condenser, and pressure detecting means responsive to the pressure within said conduit means for energizing said fan means when said pressure exceeds a predetermined level.

11. A refrigeration system comprising a plurality of refrigeration units, a plurality of compressors, one for each of said units, a plurality of first condensers, one for each of said units, each having a first flow path, containing a quantity of refrigerant, means connecting said first flow path in series with one of said refrigeration units and one of said compressors to support a flow of refrigcrant therethrougb, each of said first condensers having a second flow path, containing a quantity of refrigerant, in heat exchanging relationship with said first flow path, a second condenser,- a refrigerant receiving chamber, means for connecting said second flow paths in parallel with each other and in series with said second condenser and said refrigerant receiving chamber for supporting a flow of refrigerant therethrough, said second condenser being disposed at an elevation above said first condensers, said receiving chamber being disposed at about the same elevation as said first condensers and having a horizontal internal cross-sectional area which is greater than the horizontal internal cross-sectional area of the second flow path of any one of said first condensers, each of said first condensers being operative to condense refrigerant in said first flow path and to vaporize refrigerant in said second flow path, said second flow path having a first liquid-vapor interface disposed within the second flow path of said first condenser, and a second liquid-vapor interface disposed within said refrigerant receiving chamber, at a higher elevation than said first interface, whereby there is created a pressure differential which causes recirculation of refrigerant within said second flow path.

References Cited UNITED STATES PATENTS 1,969,187 8/1934 Schutt 62238 X 2,111,618 3/1938 Erbach 62183 X 2,487,852 10/1949 Cook 62-506 X 2,875,594 3/1959 Schilling 62506 X 3,188,829 6/1965 Siewart.

MEYER PERLIN, Primary Examiner.