US2282503A - Refrigeration - Google Patents

Description

y 1942- r A. R. THOMAS ET AL 2,282,503 7 REFRIGERATiON' Filed Nov. 10, 1938 r W INVENTORS,

W -ATIORNEY.

Patented May 12, 1942 Albert R.

Thomas and Philip r. anaemia, in,

vansville, Ind., assignors to Servel', Inc New York, N. Y., a corporation of Delaware Application November 10, 1938, Serial No. 23am e 9 Claims. (01. 62-119) The present invention relates to refrigeration and more particularly to refrigeration systems of the kind operated by heat. Still more particularly the invention relates to systems operating with a refrigerant and an absorbing medium, preferably without the use of air or other pressure equalizing fluid, the system having a high pressure side and a low pressure side.

An object of this invention is to provide a system operable by heat and employing water or like fluid as refrigerant and operable under a variety of conditions and readily'manufactured. Our novel refrigerating system is preferably hermetically sealed, made of metal, operable at low pressure, and utilizes a refrigerant which is nontoxic, non-inflammable and non-irritant. An obiectis to provide a practical air conditioning or cooling system directly applicable to the air to lithium chloride and water as the description or more feet long. The height is governed in part by other factors peculiar to the system, as will be subsequently explained.

The preferred content of the system is only a water solution of a salt such as lithium chloride or a mixture of salts such as lithium bromide,

calcium bromide and. calcium chloride. Other substances may be used such as a water solution of sodium hydroxide or ethylene glycol and water. It will be understood that in referring to proceeds, this is not by way of limitation. Corrosion inhibiting materiaLsuch as sodium chromate, may be added, as -is known in the art.

Separation of the generated water vapor and the residual concentrated solution (absorption The vaporf liquid) takes place in-vessel' l5.

passes through conduit II for condensation and be cooled. We prefer a system having only two active fluid components. Other objects are simplicity of construction, low weight per unit ofre frigeration, quick starting, efllciency in operation .under variable conditions and safety.

A preferred embodiment of the invention is shown-on the accompanying drawing forming a part of this specification.

Referring now ,to the drawing, the system ineludes a combination generator and gas-liquid lift l0 including a shell or'jacket ll. within shell II are riser tubes ll secured in and passing through a tube sheet. 9 at their lower ends and secured toand passing through a corresponding tube sheet at the upper end which may be the bottom of -a gas and liquid separation chamber IS. The space l2 within jacket I I and around tubes I4 is thus separate from the space or header l3 below partition 9 and the interior of the concentrated solution flows downwardly into conduit 18. For reasons presently to be explained liquid stands in conduit ll at an intermediate point, for example, at :0, during operation so that there is an overflow or spill-over at the tops of expeller II and conduit 18, the continuity in flow of liquid to the absorber being broken at-this point. Thus, while the continuity .of-liquid flow can be and is maintained, the continuity of the liquid stream in the sense of what may be termed a solid stream" is broken. That vessel l5. Space [2 is a steam chamber to which steam may be admitted through connection 18. A suitable condensate drain may .be provided, such as the trap II. A vent l8 may be provided at the upper end of chamber l2.

The boiler or generator I! may be made of steel and since the operating pressure is low.

relatively light gagemetal may be used. It will is, the hydraulic pressure. continuity is broken without interrupting liquid flow. Suitable bailing means may be provided in chamber ii to prevent liquid from passing over to the condenser with water vapor. To further assist in the gas and liquid separation, a water separator 20 may be provided in the conduit, I9.

28 connecting chamber II with condenser 22. Separator 2| .may drain back to chamber vll. as through pipe 2i.

The condenser may be of a variety of constructions. In the embodiment shown for illustration,

it'includes a shell 2!, tube sheets 24 and 25, coolbe noted that the rise in the generator is high and that the generator shown has full height heating. Tubes H .are straight and preferably strictly vertical as we prefer to have the liquid lifted by climbing up or hugging the tube walls with a center path of water vapor. The tubes II are accordingly dimensioned to suit this preferred mode of vapor expulsion and lifting. Tubes I4 may be, for example, of from four tenths to one half inch inside diameter and six ing water tubes 26 andcover plates 21 and 20. Condensate flows from condenser 21 into U-tube or trap conduit ll which has a high down-leg and a high up-leg. The lower bend of this conduit is on a level withtiie lower part of thee:-

pelier. The upper end of the uD-leg of conduit ll connects with a flash chamber 33 connected by liquid conduit II with an evaporator 34.

In operation, a liquid column is formed in conduit ll balancing a higher pressure in the condenser than in the evaporator. The up-ie of conduit 3| contains liquid up to the top. The down-leg of conduit 0| may curtain liquid up to,

one quarter of an inch has been used at this place. Conduit should have a width so as to readily permit liquid column variations. It should not be so small as to be a capillary tube. With the dimensiongiven there is restriction to gas flow but not liquid flow due to the vaporliquid volume ratio being on the order of between 10,000 and 100,000 to l at the conditions prevailing in the system.

Evaporator 34 includes a header 36 and a header 3! connected to the ends of an upper bank of tubes 38 and a lower bank of tubes 39. Within header 36 is a trough 40 at the ends of tubes 38, and a trough 4| at the ends of lower tubes 89. In header 31, there is a trough 42 at the ends of tubes 38, and a trough 43 at the ends of tubes 30.

Liquid line 3| spills over into trough 40 so that there is a break in liquid continuity between the liquid column in conduit 30 and the liquid in the evaporator. The upper end of flash chamber 33 is vented to the absorber by means of conduit 85. The evaporator tubes are preferably horizontal and made to hold liquid up to a. predetermined level. For this purpose, an overflow pipe 44 is provided in trough 42 discharging into trough 43 and an overflow pipe 45 is provided in trough 4| discharging into the bottom of header 35. Thus the tubes of a bank are fed in parallel and the banks in series. The evaporator contains pure or practically pure water and may be made of copper or brass to hinder corrosion due to moisture precipitation from the air onthe outside of the evaporator. Headers 36 and 31 are connected by tubes 46 and 41 with a manifold '18 connected to the upper part of absorber 49.

The top of overflow 44 is below the point of spillover in the connection between the condenser and the evaporator.

While the absorber may be made in a variety of ways, in the form shown it consists of a casing 32 providing a place of absorption 50 in which are one or more cooling coils 5|, 52. In the upper part of chamber 50 is a distributor 53 for evenly dripping liquid onto the coils 5|, 52. The upper part of the absorber is situated below the connection of conduit 18 with separation vessel The lower end 0 coil 55 is' connected'bybonduit 58 and branches 59 and 60 to the lower ends of absorber coils 5| and 52. The upper ends of coils 5| and 52 are connected by converging conduits 6| and 82 and conduit 63 to condenser header 21. A water outlet conduit 64 is connected to condenser header 28.

In vessel 54, sleeve 56 is open at its lower end. The upper end of sleeve 56 is connected by a conduit 65 to-the bottom of vessel 66. A conduit 61 connects vessel 86 with the absorber distributing pan 53. A vent conduit 68 is connected to the top of vessel 66.

I peller.

the liquid difierential in the system.

provide a liquid column between it andthe expeller for balancing the rising column in the ex- The conduit 8| connects vessel 16 with header l3 of theexpeller. The upper part of stabilizing vessel 76 isconnected by vapor connection 80 with chamber -15. Stabilizing vessel IS-is so wide that the level of liquid therein does not vary, appreciably, thus providing a substantially constant reaction head for the liquid lift in the expeller. The evaporator drains to vessel 16 through conduits 82, 83

I5 to provide gravity flow from chamber [5 to the absorber when conduit 18 is filled.

The bottom of the absorber 49 is connected by conduit 11 to the lower end of a liquid heat exchanger 69. This heat exchanger includes a shell or casing and tube sheets providing a long center chamber 10 and end chambers II and I2.

A plurality of tubes 13 are located in center Cooling and precipitation vessel 54 contains a small pipe coil 55 located around a sleeve 56.

Cooling water is supplied to coil 55 by pipe 51.

. and 84. No excess liquid is maintained in any part of the system except in vessel I6- The system charge, for example, a water solution of 40% lithium chloride by weight, maybe charged, after evacuation, into vessel 16 to the level 2. It is not necessary to charge the liquid into other parts of the system. The solution thus placed in the system will stand in expeller tubes l4 to the level 2 and also in pipe "and the tubes and end chambers of heat exchanger To start operation, steam is admitted through connection l6 and cooling water is admitted through pipe 51. The steam, which may be, for example, at atmospheric pressure, heats tubes l4 throughout their lengths. Condensate drains from chamber l2 through trap II. The cooling water circulates through the vessel 54, the absorber 49 and the condenser'22 and out through conduit 64. i

The heat applied to tubes l4 causes generation of water vapor therein =by expulsion from solution. The vapor flows upwardly carrying water with it. In this type of expeller the water is carried up essentially as an annulus with steam in the center, the steam traveling faster than the water. The water follows the inside walls of the tubes. The rising force is produced with 'the aid of the reacting columnin conduit'8land vessel 16. This type of liquid lift is particularly advantageous because it provides "circulation'cf a large quantity of liquid and gives a high-lift. A relatively large quantity solution-must be circulated relative to quantity of liquid evaporated in the evaporator to prevent the salt from precipitating from solution. The absorption liquid circulation ratio is subject to moderate variation due to variation in condenser temperature and heat input. Too large a circulation ratio causes excessive loss in the liquid heat exchanger or requires a larger liquid heat exchanger, and the ratio is determined by the concentration of the solution at the ab-.

sorber outlet and the solubility of the absorbent.

As a matter of example, suppose the liquid from the absorber is 100 F. and the evaporator-absorber pressure is eight millimeters of mercury.

The liquid concentration at equilibrium is 41% -To make the system safeit is required to circulate somewhat faster than the minimum and ten pounds of liquid to the absorber per pound of water to the condenser is a desirable rate.

' Vapor issuing from the top of expeller and elevator passes through conduits l9 and 29 to condenser 22. The unvaporized residueof solution flows into conduit 18. When pipes I8, 19, 65 and 61 and associated spaces ofheat exchanger 69, cooler vessel 54 and vessel BBare filled, the concentrated liquid can flow by gravity into the absorber since the top of pipe 18 is above the absorber liquid inlet. Thus this supply is not dependent on building up a pressure diiference and the absorber is thus quickly ready for its functioning without taking any special steps.

Water vapor is condensed in condenser 22 and passes into conduit 30. This conduit provides below the centers of the tubes and such as to maintain a maximum height of one quarter of an inch of water in the evaporator. It is desirable to limit the quantity of liquid refrigerant in the evaporator and yet provide a maximum exaporating surface. While some variation is necessary,

this has been reduced as much as possible and it is a feature of the system that the condenser, evaporator and absorber contain a minimum of liquid in order that the liquidcondition of the generator-absorber circuit shall be maintained as constant as possible, this being highly desirable on account of the critical limits in concentrations of the salt solution. Another advantage of having a plurality of shallow liquid pans in the evaporator, as distinguished from, for example, a single large pool, is that liquid dissumcient resistance to gas flow to cause pressure to build up and thus condensation quickly starts automatically and without resort to admission of air or other special steps. vAs condensate.

forms, it drops into pipe 30 and as the pressure rises in the condenser a liquid column is formed in conduit 30. Due to the quantity of vapor generated, relative to the small volume of conduit 30, this conduit is quickly filled with condensate and liquid feed to theevaporator takes place within a minute or a few minutes after applying the heat and cooling water. The cooling of the absorber maintains the low pressure in the absorber and the evaporator. Since feed of liquid to the evaporator and absorber takes place immediately, the evaporating and absorbing functions can take place even as the pressure is being built up, and it will also be seen from this that the system is capable of full refrigerative functioning at all variables of pressure differential.

When the system is operating, evaporation may take place in tube 30 due to pressure decrease on rise in the. column. The height of tube 30 should be made sufl'icient to take care of the pressure of some vapor therein formed due to pressurereduction. It may be made twice as high as what would be computed for containing only liquid in the up-leg. To prevent disturbances in the evaporator due to flash of the liquid feed, we provide the flash chamber 33. The liquid and flashed vapor is directed against the wall of this chamber. The liquid falls down and passes through pipe 3| as a quiet stream'of cold water to the evaporator. The flashed vapor passes through connection 85 to manifold 48 and thence to the absorber. Flash chamber 33 also advantageously acts as a precooler for the condensate flowing to the evaporator. The. heatof vaporization necessary to produce the flashed vapor is obtained by reduction of sensible heat of the liquid thus lowering the temperature of-the liquid and improving evaporator efliciency. I Water to be evaporated passing through pipe 3| is fed into trough 40 and flows through'pipes 38 into trough. Overflow 44 determines the turbance are minimized. This is'partly due to the phenomenon of superheated water in a boiler or evaporator not having water agitation. 'Since an object is to avoid all moving parts, this condition is of consequence. Stagnant water approaching a condition of vaporization resists the change of state. A bubble of vapor may sud: denly form under the water surface and cause what amounts to an explosion. .In the present system, the ratio of vapor volume to liquid volume at an evaporator temperature of 50 F. is on the order of 100,000 to l, wherefore a bubble forming below a height of, for example, six inches upward surge of liquid even throwing liquid into the absorber. The boiling temperature at the bottom of a .pool one inch deep, under the operating condition stated, is 46 F. compared to a surface boiling temperaturev of 40F. Heat is absorbed by the evaporator tubes from the outside air current passing v over the exterior of the evaporator. The. better heat conduction is through the liquid. In order to enhance liquid distribution and evaporation, screening is preferably provided on the interior walls of the evaporator. Pieces of wood or irregular shaped metal may be placed in the bottom of each evaporator tube to hinder the divergence of water temperature from the boiling point and also to decrease the liquid content of the evaporator. To the extent that water splashing may take place, a corrective has been provided in the form of the evaporator construction in that the vapor is conducted laterally from the places of evaporation and ebullition before being conducted to the absorber and the relatively large end headers provide separation spaces. Water overflows from trough 42 through pipe 44 to trough 43 which feeds the lower tubes 39, the construction and action of which is the same as above described. Any water overflowing or splashed into headers- 38 and 31 is conducted directly to stabilizing vessel 16 so that the liquid condition of the generator-absorber circuit is maintained substantially constant. The overflow levels of pipes 44 and 45 are preferably not higherv than midway of. the evaporator tubes.

As brought out above, the absorber is fed with concentrated solution through conduit 61. The concentrated solution flows or trickles over th outer surfaces of coils 5| and .52 while absorbing the evaporated water passing from the evaporator through manifold 48. The heat of absorption or dilution is conducted to the cooling water flowmg in coils 5| and 52. It will be appreciated that the absorber is a film absorber, no body of highe'stlevel in tubes 38 which is preferably liquid being contained therein. The diluted solution flows out of the bottom of the absorber into conduit 11 in which the liquid stands to a height dependent on the prevailing pressure difference between the high pressure side and low pressure side of the system. The liquid column is confined to pipe '11 by suitably dimensioning the apparatus as to height so that the column is narrow and of the same lateral dimension throughout. If the upper part of the column were within the absorber it would require a large volume of liquid for a small column height or pressure diiference which would both make the system sluggish and upset the condition of the liquid. Each ofthe columns utilizes a minimum of liquid while permitting continuity of flow. The liquid surface level in conduit 11 may be, for example, at the point p, giving a liquid column height equal to the vertical distance between the level p and the level in vessel 16.

Liquid flows downwardly in conduit 11 into chamber 12, upwardly through tubes 13, where heat is removed fromthe concentrated solution flowing to the absorber, and through pipe 15 into vessel 16 whence it flows downwardly through conduit 8| to chamber l3 of the expeller.

Vessel 16 is pressure equalized with the expeller outlet and the condenser by means of a vapor connection 80. This vessel 16 has a number of important functions. It takes care of variations of volume of liquid in the system as a whole. It maintains a substantially constant head for circulation of liquid. The system works too close to the solidifying point of the solution to permit great variations. in circulation. It prevents pushing back of liquid into the absorber due to. surging. It stabilizes the liquid column in pipe TI.

Our system may be said to include four major liquid columns of which three balance the pressure diflerence between the high pressure side and the lower pressure side of the system. Of the latter, one is between the condenser and the evaporator in tube 30 and completely segregated as to hydraulic continuity from both the condenser and the evaporator. A second is in pipe 11 and completely segregated as to hydraulic conpipe 11 is made independent of the gas lift reaction head and the latter is made independent of the former. The column in pipe 11 can vary throughout its range from zero to maximum while the reaction head on the generator remains substantially constant. Without the segregation ailorded by pipe 80, the reaction head for the gas lift would vary with each difference in' pressure which would be detrimental to the rate of circulation for reasons previously stated.

Vessel 54 may be provided to cause any salt precipitation to take place at the coldest point, and at a point where it will not restrict liquid flow. Precipitated salt may be redissolved again on change of condition.

It will be understood that the invention is not limited to the structural embodiment specifically disclosed.

We claim:

1. A refrigeration system employing a water solution from which water is expelled to be used as a refrigerant, including: a solution circuit in which there is a generator for expelling water vapor from the solution, an absorber for reintroducing expelled water into solution, a conduit for conducting concentrated solution from the generator to the absorber and a conduit for conducting dilute solution from the absorber to the generator; and members forming a path of flow for water and its vapor including a condenser, a

conduit for conveying water vapor from the genferential between the condenser and evaporator and constructed and connected to convey substantially all condensate to the evaporator as formed. whereby the quantity of water condensed and the quantity of water'evaporated are sub-' stantially equal; means to conduct the heat of absorption directly to a fluid extraneous to the system; said solution circuit containing a quantity of solution greater than required for the concentration difference between equilibrium at capacity conditions and maximum concentration and having a liquid volume variation vessel therein; whereby water is withdrawn from the solution circuit substantially only to the extent necessary for and in proportion to evaporation requirements with substantially proportionate condensation and proportionate flow of water as such in the system.

2. A refrigeration system employing a water solution from which water is expelled to be used as a refrigerant, including: a solution circuit in which there is a generator for expelling water vapor from the solution, an absorber for reintroducing expelled water into the solution, a conduit for conducting concentrated solution from the generator to the absorber and a conduit for conducting dilute solution from the absorber to the generator; and members forming a path of flow for water and its vapor including a condenser, a conduit for conveying water vapor from the generator to the condenser, an evaporator, a conduit for conducting water from the condenser to the evaporator,-and'a connection between the evaporator and the absorber; said evaporator including means to limit the water therein to thin bodies substantially without liquid accumulation and of a gross quantity constituting substantially a minimum for the refrigerative capacity of the system, and the liquid conduit between the condenser and the evaporator being constructed and connected to convey substantially all condensate to'the evaporator as formed, whereby the quantity of water condensed and the quantity of water evaporated are substantially equal; means to conduct the heat of absorption directly to a fluid extraneous to the system; said solution circuit containing a quantity of solution greater than required for the concentration diflerence between equilibrium at capacity conditions and maximum concentration and having a liquid volume variation vessel therein; whereby water is withdrawn from the solution circuit substantially only to [the extent necessary for and in proportion to evaporation requirements with substantially proportionate condensation and proportionate flow of, water as such in the system.

3. A refrigeration system employing a water solution from which water is'expelled to be used an absorber connected to the evaporator,-a generator, an intermediate vessel, a liquid column containing conduit between the absorber and said intermediate vessel, means to connect said intermediate vessel to said generator, said generator including a plurality of straight vertical tubes for gas lift action, the arrangement being such that the liquid surface level of the reaction head for the gas lift is in said intermediate vessel, said vertical tub'es extending substantially below and substantially above the liquid level in said inevaporator and the absorber; said evaporator includingmeans to limit the effective water for evaporation therein to a gross quantity constituting substantially a minimum for the refrigerative capacity of the system, and the liquid conduit between the condenser and the evaporator being constructed and connected to convey substantially all condensate to the evaporator as formed, whereby the quantity of water condensed and the quantity of water evaporated are substantially equal; means to directly cool the condenser and the absorber; said solution circuit containing a quantity of solution greater than required for the concentration difierence between equilibrium at capacity conditions and maximum concentration and having a liquid volume variation vessel. therein; whereby water is withdrawn from the solution circuit substantially only to the extent necessary for and in proportion to evaporation requirements with substantially proportionate condensation and proportionate flow of water as such in the system.

4. In a refrigerating system utilizing a water solution from which water is expelled to be used as a refrigerant, a condenser, an evaporator, a

liquid column containing conduit for conducting condensate from the condenser to the evaporator,

an absorber connected to the evaporator, a generator, an intermediate vessel, a liquid column containing conduit between the absorber and said intermediate vessel, means to connect said inter- 1 mediate vessel to said generator, said generator including a plurality of upstanding tubes for gas lift action,-the arrangement being such that the liquid surface level of the reaction head for the gas lift is in said intermediate vessel, said upstanding tubes extending substantially below and substantially above the liquid level in said intermediate vessel,'means to heat said upstanding tubes for a substantial distance-below said liquid level to initiate gas lift action and means to heat said upstanding tubes for 'asubstantial distance above said liquid level to vaporize already lifted liquid while in transit, whereby the water vapor produced in the upstanding tubes materially exceeds that necessary for the lifting action, and means to conduct lifted liquid to the absorber and water vapor to the condenser.

5. In a refrigerating system utilizing a'water solution from which water is expelled to be used as a refrigerant, a condenser, an evaporator, a liquid column containing conduit for conducting condensate from the condenser to the evaporator,

termediate vessel, means to heat said vertical tubes for a substantial distance below said liquid level to' initiate gas lift action and means to heat said tubes for a substantial distance above said liquid level to vaporize already lifted liquid while in transit, whereby the water vapor produced in the vertical tubes materially exceeds that necessary for the lifting action, and means to conduct lifted liquid to the absorber and water vapor to the condenser.

6. In'a refrigerating system utilizing water as the refrigerant and a salt solution as absorbent,

a condenser, an evaporator, a liquid column containing conduit for conducting condensate from the condenser to the evaporator, an absorber connected to'the evaporator, a generator, an intermediate vessel below said absorber, a liquid column containing conduit between 'the absorber and said intermediate vessel, means to connect said intermediate vessel to said generator, said generator including a plurality of vertical tubes for gas lift action, the arrangement being such that the liquid surface level of the reaction head for the gas lift is in said intermediate vessel, said vertical tubes extending substantially above the liquid level in said intermediate vessel, a steam heating jacket surrounding said vertical tubes-for a substantial distance below and a substantial distance above said liquid level to initiate gas lift action below said liquid level and to heat.

said tubes for a substantial distance above said hquid level to vaporize already lifted liquid while in transit, whereby the water vapor produced in I the vertical tubes materially exceeds that necessary for the lifting action, and means to conduct lifted'liquid to the absorber and water vapor to the condenser.

'7. In a refrigerating system utilizing a water solution from which water is expelled to be used as a refrigerant, a condenser an evaporator, a liquid column containing conduit for conducting condensate from the condenser to the evaporator,

an absorber connected to the evaporator, a generator, a vapor and liquid separator, an intermediate vessel, a liquid column containing conduit between the absorber and'said intermediatevessel, means to connect said intermediate vessel to said generator, saidgenerator including a plurality of vertical tubes for gas lift action, the arrangement being such that the liquid surface level of the reaction head for the gas lift is in said intermediate vessel, said vertical tubes extending substantially above the liquid level in .said intermediate vessel and being connected to said separator, said separator being positioned for flow of liquid by gravity therefrom to the absorber, steam jacketing for full-length heating of said vertical tubes to initiate gas lift action below said liquid level and to vaporize already lifted liquid while in transit above said liquid level, means to feed steam to the lower part of the jacketing and a vent at the upper, part of the jacketing.

8. In a refrigerating system, a condenser, an

evaporator, an absorber, a flash chamber, means to flow liquid by gravity from the flash chamber to the evaporator, means to conduct steam from the flash chamber to the absorber, and a conduit between the condenser and flash chamber adapted to hold a liquid column for balancing pressure diiference between the condenser and the evaporator.

9. In a refrigerating system in which water vaorator, such liquid column serving to balance pressure difl'erences between the condensing pressure in said condenser and the lower pressure in said evaporator, and said conduit having 7 an internal cross-sectional area so small as to present suflicient resistance to vapor flow through said conduit when no liquid is contained therein to produce a pressure difierence between said condenser and said evaporator so that condensation of vapor will be effected in said condenser to provide liquid to establish said column, the ratio of liquid volume to vapor volume being so small that the small cross-sectional area of said conduit presents substantially no resistance to flow 0! liquid therethrough,

ALBERT R. THOMAS. I PHILIP P. ANDERSON, J R.

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