US2430047A

US2430047A - Low-pressure absorption refrigerating system including a liquid pump arrangement

Info

Publication number: US2430047A
Application number: US560218A
Authority: US
Inventors: Edberg Per
Original assignee: Servel Inc
Current assignee: Servel Inc
Priority date: 1944-10-25
Filing date: 1944-10-25
Publication date: 1947-11-04
Anticipated expiration: 1964-11-04

Description

Nov. 4, 1-947.

Ilia

LOW PRESSURE ABSORPTION REFRIGERATING SYSTEM P. EDBERG INCLUDING A LIQUID PUMP ARRANGEMENT v Filed Oct. 25, 1944 2 Sheets-Sheet 2 I I; I

INVENTOR ash/ XuATTORNEY be expressly understood,

Patented Nov. 4, 1947 ATIN G SYSTELI INCLUDING ABBAN GEMENT Evansville, Ind, assignor to Send,-

n corporation of Dela- PUMP Per Edberg,

Inc., New York, N. ware a mom Application October 25, 1944, Serial No. 560,210

1 The present invention relates to refrigeration and more particularly. to

or the like and the absorbent occurs in' the system as a dilute or concentrated water solution of the salt. Such systems may include an auxiliary loop circuit for circulating liquid refrigerant to refrigerate or cool at a place remote from the evaporator and/or' an auxiliary loop circuit for continuously circulating absorption solution in the absorber to promote absorption of refrigerant vapor. Because of the low pressures at which such systems operate, the usual types of pumps will not function satisfactorily in the loop circuits.

One of the objects of the present'invention is to provide a. pump of novel construction and so arranged in the loop Another object is to provide a'pump so arranged in the auxiliary loop circuit as to produce impeller of the pump.

Another object is to provide a self-contained pump unit of the type indicated connected to a reservoir to receive liquid by gravity and having an hermetically sealed casing extending above and below the level of the liquid in the reservoir.

Still another object of the present invention is to provide a, pump of the type indicated having an impeller housing at its lower end, a motor housing. at its upper end and an intermediate shaft housing constituting a penstook for delivering liquid to a combined axial and'radial flow impeller.

These and other objects will'beoome more apparent from the following description and drawings in which like reference characters denote like parts throughout the several views. It is to however, that the drawings are for the purpose of illustration only and not a definition of the limits of the invention, reference being had for this purpose to .the appended claims.

circuit as to adapt it to cir- I culate liquids in a state close to their boiling point.

the circulation of liquid in an absorption refrigeration system.

4 Claims. (01. 62-419) 7 In the drawings- Fig. 1 is a diagrammatic view of an absorption refrigeration system incorporating the novel features of thepresent invention and showing the auxiliary loop circuits for circulating refrigerant and absorption solution; and

Fig. 2 is an enlarged longitudinal sectional view taken on line 2-2 of Fig. 1 showin the construction of the pump in the loop circuit for circulating refrigerant and the arrangement of the pump with respect to the evaporator.

In the absorption refrigeration system illustrated in Fig. l of the drawings, the liquid refrigerant such as, for example, water is introduced into the evaporator .80 from. a condenser II through a path of flow including a U-shaped tube -a,hydrostatic head of the liquid delivered to the generator l6 in'a path of with an outlet vent 21 i2. The evaporator I0 is in the form of a horizontally arranged cylindrical drum and the 'U-, shaped tube I! has one end connected to a sump l3 at the bottom of the condenser H with its opposite end extending upwardly through the bottom of theevaporator. The refrigerant vapor formed in the evaporator an absorber ll in which into a liquid absorbent such as, for example, a concentrated water solution of lithium chloride or lithium bromide. The absorber It also is in the form of horizontally arranged cylindrical drum and is positioned directly below the evaporator N. A pipe it extends upwardly from the top of the absorber I4 through the evaporator l0, and for a considerable distance above the bottom, to provide a, standpipe in the evaporaton The standplpe I5 is adapted to exhaust refrigerant vapor from the evaporator In to the absorber I while maintaining a body of liquid refrigerant in-the evaporator.

Absorption liquid enriched with refrigerant or. in other words, the dilute salt solution is conducted from the absorber It flow including the pump l8, later to be described in detail, conduits l9 and 20, liquid heat exchanger 2| and conduit 22. A plurality of riser tubes 23 are enclosed ina chamber formed by an outer shell '24 of the generator 16 and to which steam is supplied through a conduit 25 from a suitable source of supply. The rate of flow of steam through the conduit 25 is controlled by a modulating'valve 2i. Preferably, the steam chamber in the generator I8 is provided adjacent its upper end and a condensate return line 28 adjacent the base thereof. The heating of the riser tubes 23 by the v to be expelled from the abwrption solution and such expelled the vapor is absorbed bottom of the to the base of a vapor is effective to raise the absorption solution in the tubes by gas or vapor lift action. The expelled vapor passes from the upper ends of the riser tubes 23 into a vapor separator 29 and thence flows through a. conduit 30 to the condenser H, where the vapor is liquefied. Liquid refrigerant formed in the condenser flows through the U-shaped tube I2 to the evaporator I0, as explained above, to complete the refrigeration cycle.

The raised absorption solution from which refrigerant vapor has been expelled is conducted from the upper part of the generator l6 to the absorber l4 in a path of flow including a conduit 3|, chamber 32, conduit 33, liquid heat exchanger 2| and conduit 34. The upper end of the conduit 34 extends into the upper portion of the absorber |4 adjacent the inlet from the standpipe l5 and has a plurality of apertures or nozzles therein to provide a distributing pipe 35 for dividing the absorption solution as it is introduced into the absorber to promote absorption of the refrigerant vapor. The heat liberated by the absorption of refrigerant vapor in absorber I4 is taken up by a cooling medium such as, for example, water which flows upwardly through a bank of vertically disposed pipes or coils 36 in the absorber. The cooling water is introduced into the lower ends of the bank of pipes 36 from a supply main 3'! and is discharged from the upper ends of the bank of pipes through a conduit 38. Conduit 38 is connected to the condenser so that the cooling water also may be utilized to effect cooling of the condenser. The cooling water is discharged from the condenser I through a conduit 39.

The system operates in a partial vacuum with the generator l6 and condenser operating at one pressure and the evaporator I0 and absorber |4 operating at a lower pressure. The pressure differential between the high and low'pressure sides of the system is maintained by a liquid column in the up-leg of the U-shaped tube |2 between the condenser II and evaporator ID. A similar liquid column also is present in the conduit 34 connecting the absorber l4 and liquid heat exchanger 2|. The pressure differential between the absorber I4 and generator l6 also is maintained by the pump |8 connected between the absorber and conduit 20.

To prevent the progressive concentration of the absorption solution under certain conditions of operation and the crystallization and precipitation of salt resulting from such progressive concentration a control means is provided which is responsive to the concentration of the absorption solution and connected to adjust the valve 26 to regulate the amount of steam supplied to through a flexible bellows 42 to permit relative movement and the arm is pivoted at 43. The outer end of the arm 4| constitutes the movable contact 44 of a rheostat 45 connected by means of the electric circuit 46 to a servo-motor 41 & for operating the steam control valve 26. The

the generator [6. The control means may be I located in any part of the refrigeration system where the progressive concentration of the absorption solution is likely to occur. As illustrated in Fig. 1 of the drawings, the control means is located in the chamber 32 in the return line between the generator l6 and heat exchanger 2|. The control comprises a float 40 having a specific gravity such as to adapt it to rise when the concentration of the absorption solution approaches a saturation point where salt will precipitate out of the solution. When the absorption solution is diluted suificiently to prevent precipitation of salt, the float 40 will fall by gravity in the absorption solution to the position illustrated in Fig. 1.

The concentration control float 40 has an arm 4| extending outwardly from the chamber 32 flexible bellows 42 acts as a. load spring to cause the contact arm 44 to vary the resistance directly in response to variations in the concentration of the-solution to modulate the valve 26. Preferably, a baflle plate 48 is provided in the chamber 32 adjacent the end'of the conduit 3| to prevent the velocity of the stream of incoming absorption solution from affecting the operation of the control float 40. The end of the conduit 33 extends upwardly in the chamber 32 above the float to insure immersion of the control float 40 by the absorption solution.

Preferably, an overflow by-pass 50 is provided between the separating chamber 29 of the generator I6 and the bottom of the absorber l4. As

illustrated in Fig. 1 of the drawings, the upper In accordance with the present invention, the liquid refrigerant in the evaporator I0 is circulated continuously in a loop circuit to adapt the system to refrigerate at a place remote from the evaporator. The loop circuit comprises a pump 55, conduit 56, cooling element 51 and conduit 58. The pump 55 is connected to receive liquid refrigerant from the evaporator H) in a manner later to be described in detail and delivers the liquid refrigerant to the conduit 56. The conduit 56 is connected between the outlet from the pump 55 and the inlet to the cooling element 5'! and the conduit 58 is connected between the outlet from the cooling element and the upper part ofthe evaporator Hi. The cooling element 51 is illustrated diagrammatically as a cooling coil but it will be understood that this element may have other forms such as a radiator or the like depending upon the particular installation. As illustrated in Fig. 1 of the drawings, the outlet end of the conduit 58 extends into the evaporator l0 and is provided with a series of apertures or nozzles to provide a spray pipe 59 for dividing the liquid refrigerant into a spray as it is returned to the evaporator to promote evaporation.

Preferably a baffle plate 60 is provided in the evaporator I0 between theend of the spray pipe 59 and the standpipe |5 to prevent the liquid refrigerant from being swept into the standpipe with the refrigerant vapor.

As illustrated in Fig. 2, the pump 55 comprises a lower pump housing 64, an upper motor housing 65 and an intermediate shaft housing 66. The

housings

64, 65 and 66 are connected and sealed to each other as by welding or the like to provide a continuous hermetically sealed casing. The pump casing is positioned adjacent the evaporator I0 and extends above and below the level L of the liquid in the evaporator l0. An inclined conduit 61 is connected between the side of the evaporator I0 below the liquid level and the side of the shaft housing 66 so that refrigerant liquid will flow by gravity into the casing and' rise to the level L therein. Preferably, a strainer 68 is provided in the conduit 61 to filter out any foreign matter which may occur in the system. A vent tube 69 is connected between the evaporator l0 and the shaft. housing portion 66 ofpthe pump casingabove the liquid level L to balance the pressure in the casing and evaporator.

A combined axial and radial flow centrifugal impeller 10 is mounted in the pump housing 64 for rotation therein. The impeller I has a relatively large axial intake opening 'II which leads into a plurality of radial channels I2. The pump housing 64- has an annular pressure chamber 14 surrounding the periphery of the impeller I0 with an outlet port I5. The pump-housing 64 also has a radial flange 16 surrounding the port I which is connected to the cooperating flange 'I'I ofa conduit. 56 and preferably the flanges are welded .to each other to hermetically seal the joint.

Whilethe impeller I0 may be rotated by any suitable prime mover such as an hydraulic motor,

an electric motor 80, preferably, is provided forthis purpose. The electric motor 80 comprises a stator having the usual field coils 8| and a rotor 82. The motor housing 65 is made in two parts to adapt the motor 80 to be assembled therein and kept at a minimum for the most efficient operation.

The absorption solution in the absorber I4 also is circulated continuously through an auxiliary loop circuit to promote absorption of the refri erant 'vapor. The auxiliary loop circuit for the absorption solution comprises the pump I8 and the cover 83 of the housing may be attached v thereto by means of bolts 84 or by welding the cooperating flanges. If the bolts 84 are used, the

motor housing 65 must be hermetically sealed by means of, a suitable packing not herein shown. The cover 83 of the motor housing 65 is formed with a plurality of fins 85 for dissipating',the heat generated in the housing. Conduits 86 for supplying current to the electric motor 80 extend through a bushing 81 in the cover 83 which is so constructed as to hermetically seal the joint. Because of the relatively low pressures which occur in the motor housing 65, 5 to 10 mm.- Hg absolute, the discharge voltage between uninsulate'd conductors is only about one-fifth of that occurring at atmospheric pressure. Th electrical conductors in the motor 80, therefore, are heavily insulated to prevent electric leakage in the housing.

The rotor 82 of the motor 80 is connected to the impeller 10 by a shaft 90. The upper end of the shaft 96 extends through an axial bore ill in the rotor 82 and is keyed thereto for rotation as a unit. Rotor 82 rests on a step or annular shoulder 92 on the shaft 90 and is held in seating engagement with the shoulder by a nut 93. The shaft 90 and rotor 82 are supported for rotation by an anti-friction thrust bearing 94 mounted in an annular sleeve 95 forming part of the housing 65. Above the bearing 94 is a packing 96 surrounding the shaft and held in place by a gland nut 91. The annular sleeve 95 and packing 96 provide a 1 well for maintaining a supply of lubricant which is fed to the bearing by an oil slinger 98. The

' joint between the body portion and cover of the well for lubricant formed by the annular sleeve rator means of a nut I03. The liquid in the shaft housing as acts to steady the shaft 90 as it rotates therein but the shaft is further supported ad-.

jacent its lower end by a bearing I04 supported by a sleeve I05 in the shaft housing 66. The bearing I04 is lubricated by the liquid refrigerant flowing through the shaft housing 66 to the imconduit I9. The pump I8 is of a construction identical with the pump 55 and is arranged at the side of the absorber I4 with a conduit IIO connecting the absorber and shaft housing 66 of the pump. The conduit I9 is connected at one end to the outlet from the pump I8 and its opposite end III extends horizontally into the absorber I4 throughout substantially the entire lengthof the latter. The horizontally extending portion III of the conduit I9 is provided with a plurality of spray headsI I2, each of which comprises a nozzle and a deflecting plate for dividing the absorption solution into a spray and distributing the spray over the bank of cooling coils 36 to promote absorption of the refrigerant, During operation of the refrigeration system, part of the circulating solution is diverted from the conduit I9 through the conduit 20 and heat exchanger 2I to the generator I6 as previously described. One form of the invention having now been described in detail the modeof operation is explained-as follows.

-For purposes of description let it be assumed that the system is not operating and the concentration control fioat- 40 is in the position-illustrated in Fig. 1 of the drawings To initiate operation of the refrigeration system steam is supplied through the conduit 25 to the generator I6 and Water is supplied from the main 31 to the cooling coils 36 in the absorber I4 and through the conduit 38 to the condenser II. Simultaneously, current is supplied to the electric motors of the pumps I8 and 55 to rotate the impellers I0 to circulate refrigerant and absorbent solution in their respective auxiliary loop circuits. With the float 40 in the position illustrated in. Fig. 1,

the rheostat will be adjusted to supply steam to the generator I 6 for full load conditions. The steam in the generator I6 will expel water vapor from the absorption solution standing in the riser tubes 23 and the water vapor will rise in the tubes to the vapor separating chamber. 29 and raise the absorption solution by vapor lift action. In the chamber 29, the refrigerant vapor will be separated from the absorption liquid and will pass through the conduit 30 to the condenser II where the vapor will be liquefied by its contact with the relatively cold tubes therein. The liquefied refrigerant in the condenser then will flow by gravity into the sump I3 and through the U-shaped tube I2 to the evaporator I0.

The liquid refrigerant delivered to the evapo- I0 will accumulate therein around the standpipe I5 and will flow through the conduit 61 into the shaft housing 66 of the pump casing. Due to the vent tube 69 connecting the evaporator I0 and shaft housing 06 above the liquid level L the liquid refrigerant is free to rise in the shaft housing to the same level as in the evaporator. .Thus the shaft housing 66 is in the nature of a penstock for maintaining a hydrostatic head of the refrigerant liquid above the impeller I0. The refrigerant liquid will flow by gravity into the axial opening II in the hub of the impeller l and then lnto the radial passages 12. Due to the rotation of theimpeller 10 the liquid in the radial passages 12 issubjected to centrifugal force which substantially increases its velocity and delivers it to the pressure: chamber 14 surrounding the impeller. The chamber 14 converts the velocity head of the liquid refrigerant discharged from the impeller 10 to apressure head and discharges the liquid through the outlet port 15 to the conduit 55. It will be noted that the liquid refrigerant supplied to the impeller 10 is at v all times under pressuer due to the hydrostatic head in the shaft housing so that there is no tendency for the liquid to vaporize and cause the pump to become suction bound.

The liquid refrigerant leaving the pump 55 will be conducted through the conduit 56, cooling element and conduit 58back to the evaporator l0 solution through the auxiliary 100p circuit prothrough separate paths in the heat exchanger 2 I,

where it will be sprayed through the nozzles in the spray pipe 59. During the passage of the liquid refrigerant through the cooling element 51, it will pick up heat from the surrounding ambient such as a stream of air or a'liquid to be cooled. Due to the pressure of the liquid refrigerant circulating in the auxiliary loop circuit little if any evaporation will occur but instead the heat will .be received as sensible heat to increase the temperature of the refrigerant. When the refrigerant is delivered to the evaporator l0 through the spray pipe 59 the low pressure prevailing therein will cause evaporation of a part of the refrigerant with a conversion of its sensible heat to latent heat of vaporization thereby reducing its temperature and the temperature of the body of refrigerant in the evaporator. Thus the circulating refrigerant operates to absorb heat from the ambient surrounding the cooling element 51 and a portion of the refrigerant evaporates in the evap-' orator to reduce its temperature.

The refrigerant vapor in the evaporator ID will flow through the standpipe IE to the absorber l4. Simultaneously with the introduction of the refrigerant vapor into the absorber It, the concentrated absorption solution in the separating chamber 29 will flow through the conduit 3|, chamber 32, conduit 33, heat exchanger- 2|, conduit 34 and spray pipe ,35 which delivers it into the top of the absorber adjacent the standpipe l5 as a spray. Thus there will be an intimate mixture of the refrigerant vapor with the finely divided concentrated absorption solution, Due to the afiinity of the concentrated absorption solution for the refrigerant vapor, the latter will be absorbed in the solution.

Absorption solution also will be circulated in the auxiliary loop circuit comprising the pump I8 and conduit l9 which will deliver the solution back to the absorber through the spray heads H2 on the spray pipe Ill. The absorption solution is delivered to the pump H3 in a manner identical with that described with respect to the flow of refrigerant into the pump 55. The shaft housing of the pump 18 acts as a penstock to maintain a hydrostatic head of the absorption solution delivered to the impeller of the pump so that the solution is maintained under pressure as it flows through the pump.

The heat of absorption is transferred to the cooling water circulating through the cooling coils 36 in the absorber M. The rapid absorption of the refrigerant vapor in the absorber M will tend to reduce the pressure therein causing the refrigerant vapor in the evaporator I!) to be drawn through the standpipe 15. It will be observed, therefore, that the circulation of the absorption the dilute solution fiowingto the generator is heated by the concentrated solution flowing to the absorber which gives up its heat and becomes colder.

During the operation of the refrigeration system any abnormal condition causing a, change in the concentration of the absorption solution flowing through the chamber 32 will actuate the float 40 to adjust the rheostat 45 and thereby adjust the servo-motor 41 and valve 26 for controllin the flow of steam to the generator 16. If the concentration of the absorption solution increases the float 40 rises which, in turn, partially closes the valve 26 to decrease the flow of steam to the generator l6. Upon a decrease in the concentration of the absorption solution, the float 40 will fall by gravity which operating through the rheostat 45 and servo-motor 41 will open the valve 26 to supply more steam to the generator Hi.

It will now be observed from the foregoing specification that the present invention provides a novel construction and arrangement of pump for use in the auxiliary loop circuits of an absorption refrigeration system for circulating refrigerant and absorption solution. It also will be observed that the present invention provides a.

to receive liquid from an element of the refrigeration system by gravity.

While a, preferred form of the invention is 4 herein illustrated and described it will be understood by those skilled in the art that various changes may be made in the construction and arrangement of the parts without departing from the spirit or scope of the invention. Reference, therefore, is to be had to the claims appended hereto for a definition of the scope of the invention.

What is claimed is:

1. In an absorption refrigeration system having a plurality of interconnected elements, a pump housing below the liquid level in one of the elements and having an impeller therein, a motor housing above the liquid level in said element and having an electric motor therein, a shaft housing extending between the pump and motor housings, said housings being connected to provide an hermetically sealed casing, a shaft in the shaft housing connecting the electric motor and impeller, a conduit connecting the element and shaft housing intermediate the ends of the latter for supplying liquid from the element to the casing by gravity, a vent between the shaft and motor housings, and a check valve in the vent to permit equalizing of the pressure therebetween while preventing the' splashing of liquid into the motor housing.

2. In an absorption refrigeration system of the type which operates in a partial vacuum, a genthe evaporator and easing intermediate the ends of the latter for supplying liquid from the element to the casing by gravity, a housing formed by the casing for enclosing the prime mover; and a check valve in the housing for equalizing pressure while preventing the splashing of liquid into the motor housing.

3. In an absorption refrigeration system of the type which operates in a partial vacuum, a generator, a condenser, an evaporator, an absorber, means interconnecting the elements to provide circuits for refrigerant and absorbent, an auxiliary loop circuit connected to circulate absorption solution in the absorber, and a pump in said auxiliary loop circuit having an hermetically sealed casing extending above and below the level of the absorption solution in the absorber, a shaft extending throughout the length of the casing, an impeller at the lower end of the shaft, a prime mover at the upper end of the shaft, a conduit the prime mover, and a check valve in the hou sing for equalizing pressure while preventing the splashing of liquid into the motor housing.

4. In an absorption refrigeration system of the type which operates in a partial vacuum, a generator, a condenser, an evaporator, an absorber,

Number connecting the element and casing intermediate the ends of the latter for supplying absorption solution from the element to the casing by gravity, a housing formed by the casing for enclosing means interconnecting the elements to provide circuits for refrigerant and absorbent, an auxiliary loop circuit connected to circulate refrigerant in the evaporator, an auxiliary loop circuit connected to circulate absorption solution in the absorber, each of the auxiliary loop circuits having a pump comprising a pump housing below the liquid level with an impeller therein, a motor housing above the liquid level with an electric motor therein, a shaft housing extending between the pump and motor housings, said housings being connected to provide an hermetically sealed casing, a shaft in the shaft housing connecting the electric motor and impeller, a conduit connected to the shaft housing for supplying liquid by gravity to the pump housing and applying a hydrostatic head on the impeller, a vent between the shaft and motor housings, and a check valve in the vent to permit equalizing of the pressure therebetween while preventing the splashingoi' liquid into the motor housing.

' PER EDBERG. I

file of this 1 patent:

UNITED STATES PATENTS Name Date 2,019,290 Brace Oct. 29, 1935 2,225,491 Voorhees et a1 Dec. 1'7, 1940 2,298,924 Bichowsky Oct. 13, 1942