US2718122A

US2718122A - Refrigerating system

Info

Publication number: US2718122A
Application number: US273389A
Authority: US
Inventors: Charles S Grimshaw
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1952-02-26
Filing date: 1952-02-26
Publication date: 1955-09-20
Anticipated expiration: 1972-09-20

Description

Sept. 20, 19 c. s. GRIMSHAW REFRIGERATING SYSTEM Filed Feb. 26, 1952 Fig.2.

Fi a.

Inventor Charles S. Grimshaw,

His Attorney.

United States Patent Ofidce 2,718,122 Patented Sept. 20, 1955 REFRIGERATENG SYSTEM Charles S. Grimshaw, Erie, Pa., assignor to General Electric Company, a corporation of New York Application February 26, 1952, Serial No. 273,389

13 Claims. (Cl. 62-8) My invention relates to refrigerating systems and more particularly to refrigerating systems including a flooded recirculating evaporator.

In some refrigerating systems, a flooded evaporator of the recirculating type is employed to secure a more uniform temperature. Such an evaporator may consist of a length of continuous tubing depending from a header and connected at both ends to the header. Circulation is dependent upon the difference between the head of liquid refrigerant imposed on one end of the tubing and the head of liquid and vaporized refrigerant imposed on the other end. In order to secure improved cooling by such evaporators and to increase the length of tubing which may be employed, it is desirable to induce circulation therein so that the circulation of refrigerant therethrough is greater than that resulting entirely from the aforementioned difference in head. By my invention, the valve employed for providing a pressure, and hence a temperature, differential between two contiguous sections of the refrigerating system, for example, between two evaporators operating at different temperatures, is arranged so that the discharge therefrom is effective for inducing circulation in the flooded evaporator. By my invention, an improved arrangement is also provided for adjusting the pressure differential maintained by the valve.

It is an object of my invention to provide an improved arrangement for inducing circulation in a flooded recirculating evaporator.

It is another object of my invention to provide a series two-temperature refrigerating system including a pressure-reducing device and an improved arrangement including this device for inducing circulation in one of the evaporators of the two-temperature system and an improved arrangement for facilitating separation of liquid and vaporized refrigerant to minimize supply of vaporized refrigerant to the second evaporator.

It is a further object of my invention to provide a twotemperature refrigerating system including a pressurereducing device and including an impoved arrangement for adjusting the pressure differential maintained by this device.

It is still another object of my invention to provide a refrigerating system including a header and an improved arrangement associated with the header for inducing circulation in a flooded evaporator connected at both ends to the header.

It is still a further object of my invention to provide a refrigerating system including a pressure-reducing device and an improved arrangement utilizing the pressure reducing device for inducing circulation of refrigerant in a flooded recirculating evaporator.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawing in which Fig. 1

is a schematic representation of a refrigerating system incorporating an embodiment of my invention; Fig. 2 is an enlarged sectional view of the portion of the system shown in Fig. 1; Fig. 3 is a sectional elevation view illustrating a modified form of my invention; Fig. 4 is a view taken along the line 44 in Fig. 3 in looking in the direction of the arrows; and Fig. 5 is a view, corresponding to Fig. 4, showing another modified form of my invention.

In carrying out the objects of my invention, a pressurereducing valve is employed for maintaining a pressure differential between two contiguous sections of a refrigerating system and this valve is arranged so that refrigerant is discharged therefrom directly in line with one end of a flooded recirculating evaporator to induce circulation of refrigerant therein. The pressure-reducing valve and the flooded evaporator are associated in a particular manner with the header of the refrigerating system. A conduit is provided for transferring the liquid refrigerant from the header to the discharge passage of the valve to insure availability of the liquid refrigerant for supply to the flooded evaporator. In modified forms of the invention, magnetic elements and Curie metal elements are employed for varying the operation of the valve.

Referring to Figs. 1 and 2, there is shown a refrigerating system including a refrigerating unit 1, a condenser 2, and two evaporators 3 and 4. The evaporator 4 is operated at a low temperature, such as 0 F., suitable for the proper preservation of frozen foods. The evaporator 3 is operated at a somewhat higher temperature suitable for the proper preservation of fresh foods. Liquid refrigerant is supplied from the condenser 2 to the fresh food evaporator 3 through a capillary tube 5. Vaporized refrigerant is returned to the refrigerating unit from a header 6 through a suction line 7.

The header 6 includes a tubular housing 8. A pressure-reducing device 9 is assembled within the housing 8,

and divides the header into two chambers 10 and 11.

The pressure-reducing device 9 is employed to maintain a predetermined temperature differential between the fresh food evaporator 3 and the freezer evaporator 4 by maintaining a predetermined pressure difference therebetween.

The fresh food evaporator 3 is connected to the header 6 in communication with the chamber 10 by a conduit 12. The freezer evaporator 4 is of the flooded recirculating type and it includes a continuous length of conduit connected at both ends to the header 6 in communication with the chamber 11. One end 13 of the freezer evaporator 4 is connected through a header 6 and extends into the chamber 11 below the level of liquid refrigerant normally present therein, as indicated at 14. The other end 15 of the freezer evaporator 4 is connected with the header 6 and extends into the chamber 11 above the level 14 of liquid refrigerant therein. Liquid refrigerant is supplied from the chamber 11 of the header 6 to the evaporator 4 through the one end or inlet conduit 13 and refrigerant vaporized in the evaporator 4 passes through the other end or discharge conduit 15 into the chamber 11. Vaporized refrigerant and oil is returned from the chamber 11 to the refrigerating unit through the suction line 7. In order to assist in starting ebullition in the freezer evaporator 4, a trap 15a is provided at the bottom of the inlet conduit 13 of this evaporator, and this trap includes a slight rise indicated at 15b. A bubble of gaseous refrigerant is held in the rise 15b during the off cycle, and this acts to initiate ebullition during the on cycle.

The circulation of refrigerant in the flooded evaporator is then dependent upon the difference between the liquid head imposed through the inlet conduit 13 and the head of liquid and vaporized refrigerant imposed through the discharge conduit 15. Since this head may be inadequate for securing sufficient circulation under some circum- 3 stances, I have provided a particular arrangement for inducing circulation in the flooded evaporator 4.

The pressure-reducing device includes a solid genera'lly cyliri'd'rical body In which divides the header into the two chambers lid and 11. The body 16 is drilled to provide a passage therethrough including an inlet passage 17 from the chamber 19 and the fresh food evaporator 3 and a discharge or outlet passage 18. Communication between the inlet and

discharge passages

17 and 18 respectively, and hence between the chambers and 11 and between the evaporators 3 and 4, is controlled by a valve or valve element 19 slidable in the passage 17 so as to block or to permit flow of refrigerant between the

passages

17 and 18. In order to bias the valve element 19 toward aclosed position, that is toward a position wherein how of refrigerant between the

passages

17 and 18 is blocked, a pivoted weight member 20 is provided. This weight member 2i) is pivotally mounted by a pin 21 on the solid body 16, and the face 22 of this pivoted weight engages the valve element 19 to urge the valve element toward its closed position. The weight of the member 20 and its effective lever arm determine the pressure diiferential between the evaporators 3 and 4 which is necessary to effect opening of the valve and hence determine the temperature difference between the fresh food evaporator 3 and the freezer evaporator 4.

The weight member has been shown in Fig. 2 positioned in a vertical plane. In this position, the maximum opposing forces exerted by the weight against the pin 19 and hence a maximum pressure differential is maintained between the evaporators 3 and 4. If it is desired to reduce the pressure differential maintained, particularly in setting this pressure differential during factory assembly, the header may be rotated about its longitudinal axis, that is, about an axis coinciding with or parallel to the axis of the portion of the passage 17 in which the pin 19 is disposed, thereby moving the pivoted weight member 26 out of the vertical plane shown in Fig. 2. The

conduits

7, 12, 13 and 15 have sufiicient freedom to permit the small amount of rotation of the header required for this adjustment. In this manner, the pressure differential between the evaporators 3 and 4, and

hence the temperature differential therebetween may be adjusted. The force exerted by the weight in its rotated positions, ignoring the possible increase in friction at the pivot pin 21, is proportional to the cosine of the angle of rotation, that is, the angle between the plane of the pivoted weight member 2t) in the adjusted position and in the vertical plane shown in Fig. 2.

In accordance with my invention, the discharge passage 18 of the pressure-reducing device 9 is positioned directly in line with the end of the conduit 13 forming the freezer evaporator 4. Accordingly, refrigerant discharged through the passage 18 is directed into the inlet conduit 13. The velocity of the refrigerant so discharged is effective for inducing a circulation of refrigerant in the freezer evaporator 4, since part of the kinetic energy is recovered and increases the pressure in the inlet conduit 13 to assist in inducing this circulation. It will be noted that the discharge passage 18 is in line with the end of the conduit into which liquid refrigerant normally flows so that it acts in a direction to assist the natural circulation in the flooded evaporator.

The refrigerant from the fresh food evaporator 3 and from the discharge passage 18 is directed toward the inlet conduit 13 at a point in the header at or near the level of liquid refrigerant therein. Hence, separation of vapor and liquid is facilitated, the vapor passing into the suction line 7 without passing through the evaporator '4. By this arrangement, which provides for vapor and liquid separation, substantially all the vapor which passes through the freezer evaporator 4 represents that resulting from heat introduced into the evaporator 4, and the inefiicien'c'y which would result from circulating through the evaporator 4 vaporized refrigerant from the evaporator 3 is avoided. It is noted that this desirable operation is not secured where vaporized and liquid refrigerant from the fresh food evaporator are injected into a conduit of the freezer evaporator at the bottom of a vertical header and hence well below the level of liquid refrigerant in the flooded frozen food evaporator. In such a case, a large proportion of the vaporized refrigerant from the fresh food evaporator passes into the conduit forming the freezer evaporator and circulates through the entire length of tubing comprising this freezer evaporator, reducing the effectiveness of the freezer evaporator.

With an arrangement such as that described, it is possible for the velocity of the refrigerant discharged through the passage 18 to be such that it forces the liquid refrigerant 23 in the chamber 11 away from the region 24 and retards or prevents liquid refrigerant in the chamber 11 from flowing over the edge of the inlet conduit 13 into the evaporator 4. Hence, even though this velocity were still effective for inducing circulation of refrigerant in the freezer evaporator 4, it might have the disadvantage that it prevents liquid refrigerant in the chamber 11 from reaching the conduit 13 in sufficient quantity. Accordingly, the evaporator 4 might be starved of liquid refrigerant. To overcome this possible problem, a tube or conduit 25 is provided extending into the chamber 11 of the header and having one end 26 disposed below the level 14 of liquid refrigerant in the chamber 11. The other end 27 of this tube is fitted in a recess 28 in the body 16, the recess 28 communicating through a downwardly inclined orifice 29 with the discharge passage 18. With this arrangement, the velocity of the refrigerant discharged through the passage 18 and the consequent reduction in pressure adjacent the orifice 2% effects a transfer of liquid refrigerant through the tube 25 to the discharge passage 18. This liquid refrigerant from the tube 25 is then directed into the inlet conduit 13 by the refrigerant flowing past the valve 19 and through the discharge passage 18. By this arrangement, not only is circulation of refrigerant in the evaporator 4 induced but also a supply of liquid refrigerant into the inlet conduit 13 and the evaporator 4 is insured. The direction of the refrigerant from the passage 17 past the valve pin 19 varies, dependent upon the amount of opening of the valve, from a direction almost parallel to the longitudinal axis of the pin 19 to a direction inclined about 45 with respect to this axis. The downward inclination of the orifice 29 has been found to provide for the introduction of liquid refrigerant from the tube 25 into the discharge passage 18 under these widely varying directions of the stream of refrigerant introduced into the passage 18 from the passage 17.

The inlet passage 17 of the pressure-reducing device includes a downwardly inclined portion so that the inlet end 31 thereof is at a lower level. This reduces the liquid level which is maintained in the chamber it? and tense reduces the blow-through time and the charge of refrigerant necessary to operate the refrigerating system.

In the assembly of the structure described above, the

conduits

12, 13 and 15 are aluminum brazed into engagement with the header and the corrosive flux is then washed away. The pressure-reducing device 9 is then pressed into 'the endof the header into the position shown and is locked in position by rolling a portion 32 of the header into engagement with a circumferential groove in the body 16of the pressure-reducing device. As a final step, the open right end of the header is pinched together, as indicated at 3321, and welded by some non-flux method, for example, argon welding, because it would be difficult or impossible to remove corrosive flux from the evaporaan 4 after the pressure-reducing device 9 is in place.

A modified form of my invention is shown in Figs. 3 and 4. The same numerals have been employed-to designate corresponding parts in Figs. 3 and 4 and in Figs. 1 and 2. In the form shown in Figs. 3 and 4, a pivoted weight member 20 for biasing the valve element 19 is mounted on the solid body 16 of the pressure-reducing valve 9 by means of a knife edge 34 engaging a recess in the body 16. The form of Figs. 3 and 4 differs from that previously described primarily by the addition of a magnetic element 35 to the pivoted weight member 20'. The magnetic element 35 is received within a recess in the weight member 20 and may be secured thereto in a suitable manner, as by a press fit, welding, etc. A magnetic yoke 36 is adjustably mounted outside the header 6. This yoke includes two inwardly extending

poles

37, 38 generally aligned with the magnetic element 35 so that adjustment of the yoke 36 upwardly and downwardly is effective to decrease or increase the force exerted by the pivoted weight member 20 and hence to vary the pressure differential maintained by the pressure-reducing device 9. The yoke 36 may be mounted in any suitable manner for effecting adjustment. In the form shown, a depending leg 39 of the yoke is received in a recess in a stationary member 40 and is held in any adjusted position by a set screw 41. In this form the header 6, or at least the portion thereof between the magnetic yoke 36 and the magnetic element 35, is made of a non-magnetic material.

The broad idea of employing an adjustable yoke for varying the pressure differential maintained by a weight type pressure differential valve is not my invention but is described and claimed in the copending application of James F. Young, Serial No. 264,173, filed December 29, 1951, now Patent No. 2,700,395, and assigned to the assignee of the present invention.

Another modified form of my invention is shown in Fig. 5. This form is somewhat similar to that of Figs. 3 and 4 except that the yoke 42 thereof is fixedly mounted on a stationary support 42. The yoke includes magnetizable or

magnetic elements

43 and 44 positioned externally of the housing 6 and generally adjacent a laterally extending element 45 fixed in the end of a pivoted weight member 46 in the same manner as the magnetic element 35 in the form shown in Fig. 3. The element 45 in the form shown in Fig. is composed of Curie metal which has the characteristic of becoming magnetic at a predetermined temperature. Thus when the temperature within the header 6 and hence the temperature of the evaporator 4 reaches a predetermined low value, the element 45 becomes magnetic and is then attracted toward the

legs

43, 44 of the yoke 42 exerting additional upward force on the pivoted element 46 and thereby moving the valve of the pressure-reducing device toward its open position. This reduces the pressure differential maintained by the pressure-reducing device. As in the form shown in Figs. 3 and 4, the header 6, or at least the portion thereof between the yoke 42 and the Curie metal element 45, is made of a non-magnetic material.

While I have shown and described specific embodiments of my invention, 1 do not desire my invention to be limited to the particular constructions shown and described and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A refrigerating system including a header, a pressurereducing device for maintaining a pressure differential between two contiguous sections of said system, said device including a member mounted in said header and dividing said header into two chambers, a flooded recirculating evaporator having an inlet conduit connected to said header for receiving liquid refrigerant from said header, said member including a discharge passage, and a second conduit extending into said header below the level of liquid refrigerant therein and communicating with said discharge passage for transferring liquid refrigerant from said header to said discharge passage, said discharge passage being aligned with said one end of said evaporator conduit for directing liquid refrigerant from said second 6 conduit into said one end of said evaporator conduit and for inducing circulation of refrigerant in said evaporator.

2. A two-temperature refrigerating system including a first evaporator, a second evaporator, a header, and a pressure-reducing device mounted in said header for maintaining a pressure differential between said first evaporator and said second evaporator, said second evaporator being of the flooded recirculating type and including a continuous conduit having one end connected to said header for receiving liquid refrigerant therefrom and the other end connected to said header for discharging vaporized refrigerant thereto, said pressure-reducing device including a discharge passage aligned with said one end of said conduit for inducing circulation of refrigerant in said evaporator.

3. A two-temperature refrigerating system including a first evaporator, a second evaporator, a horizontal header, a pressure-reducing device mounted in said header for maintaining a pressure differential between said first evaporator and said second evaporator, said second evaporator being of the flooded recirculating type and including a depending continuous conduit having one end connected to said header for receiving liquid refrigerant therefrom and the other end connected to said header for discharging vaporized refrigerant thereto, said pressure-reducing device including a discharge passage aligned with said one end of said conduit for inducing circulation of refrigerant in said evaporator, the exit end of said discharge passage being disposed near the level of liquid refrigerant in said header for facilitating separation of vaporized refrigerant from the body of refrigerant supplied through said passage from'said first evaporator.

4. A refrigerating system including a header, a pressure reducing device mounted in said header for maintaining a pressure differential between two contiguous sections of said system, a flooded recirculating evaporator including a continuous conduit having one end connected to said header for receiving liquid refrigerant therefrom and the other end connected to said header for discharging vaporized refrigerant thereto, said pressure-reducing device including a discharge passage, and a second conduit having one end extending into said header below the level of liquid refrigerant therein and the other end communicating with said discharge passage for transferring said refrigerant from said header to said discharge passage, said discharge passage being aligned with said one end of said evaporator conduit for directing liquid refrigerant from said second conduit into said one end of said evaporator conduit and for inducing circulation of refrigerant in said evaporator, said other end of said second conduit being inclined in a direction toward the exit end of said discharge passage to facilitate transfer of liquid refrigerant through said second conduit into said discharge passage.

5. A two-temperature refrigerating system comprising a first evaporator, a second evaporator, a header, and a pressure-reducing device mounted in said header and dividing said header into two chambers, said first evap orator being connected to said first chamber to discharge refrigerant thereto, said second evaporator being of the flooded recirculating type and including a continuous conduit having both ends thereof connected to said second chamber, said pressure-reducing device including. a passage for refrigerant from said first chamber to said second chamber, said device including a valve for controlling flow of refrigerant through said passage to maintain a pressure differential between said evaporator-s, the discharge end of said passage being aligned with one end of said conduit whereby the velocity of refrigerant discharged from said passage is effective to induce circulation of refrigerant in said second evaporator.

6. A two-temperature refrigerating system comprising a first evaporator, a second evaporator, a header, a pressurereducing device mounted in said header and dividing said header into two chambers, said first evaporator being connected to said first chamber to discharge refrigerant thereto, said second evaporator being of the flooded recirculating type and including a continuous conduit having both ends thereof connected to said second chamber, said pressure-reducing device including a passage for refrigerant from said first chamber to said second chamber, said device further including a valve for controlling flow of refrigerant through said passage, and a pivoted Weight member urging said valve toward its closed position to maintain a pressure differential between said evaporators, the discharge end of said passage being a-iigned with one end of said conduit whereby the velocity of refrigerant discharged from said passage is effective to induce circulation of refrigerant in said second evaporator.

7. A two-temperature refrigerating system comprising a first evaporator, a second evaporator, a header, a pressure-reducing device mounted in said header and dividing said header into two chambers, said first evaporator being connected to said first chamber to discharge refrigerant thereto, said second evaporator being of the flooded recirculating type and including a continuous conduit having both ends thereof connected to said second chamber, said pressure-reducing device including a passage for refrigerant from said first chamber to said second chamber, said device further including a valve for controling flow of refrigerant through said passage, and a pivoted weight member urging said valve toward its closed position to maintain a pressure differential between said evaporators, the discharge end of said passage being aligned with one end of said conduit whereby the velocity of refrigerant discharged from said passage is effective to induce circulation of refrigerant in said second evaporator, said header being rotatable about an axis parallel to said passage for varying the effective force exerted by said pivoted weight member against said valve for urging said valve toward its closed position.

8. A two-temperature refrigerating system comprising a first evaporator, a second evaporator,-a header, a pressurereducing device disposed in said header and dividing said header into two chambers, said first evaporator being connected to said first chamber to discharge refrigerant thereto, said second evaporator being of the flooded recirculating type having both ends connected to said second chamber, said pressure-reducing device including a passage for refrigerant from said first chamber to said second chamber, said device further including a valve pin disposed in said passage for controlling flow of refrigerant through said passage, and a pivoted weight member urging said valve pin toward its closed position to maintain a pressure differential between said chambers, said device being rotatable about an axis parallel to said passage for varying the effective force exerted by said weight member against said valve.

9 A two-temperature refrigerating system comprising a first evaporator, a second evaporator, a header, a pressure-reducing device mounted in said header and dividing said header into two chambers, said first evaporator being connected to said first chamber to discharge refrigerant thereto, said second evaporator being of the flooded recirculating type and including a continuous conduit having both ends thereof connected to said second chamber, said pressure-reducing device including a passage for refrigerant from said first chamber to said second chamber, said device including a valve for controlling flow of refrigerant through said passage, a pivoted weight member urging said valve toward its closed position to maintain a pressure differential between said evaporators, and a second conduit extending into said second chamber below the level of liquid refrigerant therein and communicating with the discharge end of said passage for transferring liquid refrigerant from said second chamber to said discharge end of said passage, said discharge end of said passage being aligned with one end'of said conduit whereby the velocity of refrigerant discharged from said passage is effective to direct said liquid refrigerant from said second conduit into said one end of said evaporator conduit and to induce circulation of refrigerant in said second evaporator.

10. A two-temperature refrigerating system comprising a first evaporator, a second evaporator, a header, and a pressure-reducing device mounted in said header and dividing said header into two chambers, said first evaporator being connected to said first chamber to discharge refrigerant thereto, said second evaporator being of the flooded recirculating type and including a continuous conduit depending from said header, one end of said second evaporator being connected to said header below the normal level of liquid refrigerant therein and the other end of said evaporator being connected to said header above the level of liquid refrigerant therein, said pressure-reducing device including a passage for refrigerant from said first chamber to said second chamber, said device including a valve for controlling flow of refrigerant through said passage to maintain a pressure differential between said evaporators, the discharge end of said passage being aligned with said one end of said second evaporator whereby the velocity of refrigerant discharged from said passage is effective to induce circulation of refrigerant in said second evaporator.

11. A two-temperature refrigerating system comprising a first evaporator, a second evaporator, a header, a pressure-reducing device mounted in said header and dividing said header into two chambers, said first evaporator being connected to said first chamber to discharge refrigerant thereto, said second evaporator being of the flooded recirculating type and including a continuous conduit having both ends thereof connected to said second chamber, said pressure-reducing device including a passage for refrigerant from said first chamber to said second chamber, said device including a valve for controlling flow of refrigerant through said passage, a pivoted weight member urging said valve toward its closed position to maintain a pressure differential between said evaporators, the discharge end of said passage being aligned with one end of said second evaporator whereby the velocity of refrigerant discharged from said passage is effective to induce circulation of refrigerant in said second evaporator, said weight including a magnetic element, and a magnet movably positioned outside said header for attracting said magnetic element to vary the opposing force exerted by said weight for adjusting the pressure differential maintained by said pressure-reducing device.

12. A two-temperature refrigerating system comprising a first evaporator, a second evaporator, a header, a pressure-reducing device mounted in said header and dividing said header into two chambers, said first evapora'tor being connected to said first chamber to discharge refrigerant thereto, said second evaporator being of the flooded recirculating type and including a continuous conduit having both ends thereof connected to said sec- 0nd chamber, said pressure-reducing device including a passage for refrigerant from said first chamber to said second chamber, said device including a valve for controlling flow of refrigerant through said passage, a pivoted weight member urging said valve toward its closed position to maintain a pressure differential between said evaporators, the discharge end of said passage being aligned with one end of said second evaporator whereby the velocity of refrigerant discharged from said passage is effective to induce circulation of refrigerant in said second evaporator, said weight including an element com-- posed of Curie metal, and a yoke of magnetizable material mounted outside said header for exerting an attracting force on said Curie metal element under predetermined temperature conditions within said header to vary the opposing force exerted by said pivoted weight on said valve element, said Curie metal element having the characteristic of becoming magnetic at a predetermined temperature whereby said yoke exerts its attractive force on said Curie metal element-at said predetermined temperature.

13. In a refrigerating system, the method of assembling a pressure-reducing device, an evaporator, and a header which comprises providing an elongated header having one closed end and one open end, aluminum brazing an evaporator conduit into engagement with said header, Washing the flux from within said header through said open end, inserting a pressure reducing device into said header, rolling a portion of said header into engagement with a circumferential groove in said device to maintain said device in fixed relationship to said evaporator, closing said open end of said header, and sealing said last-named end by fluxless Welding to complete said assembly.

References Cited in the file of this patent UNITED STATES PATENTS Gay Mar. 12, Philipp Oct. 27, Grothouse Dec. 15, Whitesel Mar. 16, Baker July 25, Philipp Sept. 5, Atchison June 3,