US2857015A

US2857015A - Dehumidifying apparatus

Info

Publication number: US2857015A
Application number: US541743A
Authority: US
Inventors: Gilbert A Kelley; Herbert E Parker
Original assignee: Bethlehem Steel Corp; Surface Combustion Corp
Current assignee: Bethlehem Steel Corp; Surface Combustion Corp
Priority date: 1955-10-20
Filing date: 1955-10-20
Publication date: 1958-10-21
Anticipated expiration: 1975-10-21

Description

Oct. 21, 1958 G. A. KELLEY ETAL DEHUMIDIFYING APPARATUS Filed Oct. 20, 1955 INVENTORS, G. A. KELLEY,

BY H. E. PARKER DEHUMIDIFYING APPARATUS Gilbert A. Kelley, Toledo, Ohio, and Herbert E. Parker,

Application October 20, 1955, Serial No. 541,743

6 Claims. c1. 1832) This invention pertains to controls for absorption-type dehumidifying apparatus and has particular adaptability to such apparatus used in shipboard operation.

Dehumidification in air conditioning has been applied to numerous situations since its inception. A recent example of this has been to dehumidify the holds of ships transporting items that are damageable by moisture. A particular application is in the transportation of steel through sea water of varying temperature such as from the East Coast through the Panama Canal to the -West Coast where sea water temperatures may vary from 40 F. to 90 F. during the voyage. When this sea water is used as a cooling medium in the dehumidification apparatus, the temperature of the cooling coils, air, and hygroscopic solution therein will be correspondingly changed; Such a change results in various operating problems in the dehumidification apparatus as will be amplified later.

It is an object of our invention to provide dehumidifying apparatus and controls therefor that will efficiently operate at all temperatures of sea water that a ship may encounter.

For'further consideration of what we believe novel and our invention refer to the drawing and following specification.

In the drawing:

nits States Patent Figure 1 is a partially schematic view of dehumidifying apparatus embodying our invention,

Figure 2 shows a detail of Figure 1, and

Figure 3 depicts alternate controls that may be used with the apparatus of Figure 1.

The unit comprises a washer casing 11, a regenerator casing 12, and a sump 13. Bulkhead 21 is a portion of the hull of the ship and a deck 22 is provided on which the apparatus rests. Fresh air, or air from the hold to be dehumidified, is drawn through duct 14, and passed by cooling coils 15 and spray 16 by blower 17. This is delivered to the hold through duct 18. In contactor or washer casing 11, the air is dehumidified by means of the spray 16 which is a hygroscopic solution, such as lithium chloride in water, emitting from nozzles in spray bar 20 and draining to sump 13. The air is also cooled by coils 15, which have sea water passing therethrough.

Solution is supplied to spray bar 20 by means of pump 23 which also supplies a relatively small amount to spray bar 24, the amounts being proportioned by orifices 25 and 26. 1 Spray 27 from spray bar 24 flows over heating coils 28 and hence back to'sump 13. Scavenger air from the outside atmosphere, contacted with spray 27, enters duct 30 and exhausts through pipe 32 by means of blower 31. This air is generally ducted from an outside air source and is used to carry oif water which is expelled when the solution 'is heated by the coils 28 through which a heating medium such as steam is passed. The flow of the heating medium is controlled by a pneumatically operated valve 33.

Flowof sea water through coil 15 is maintained at a constant, full rate by pump 19 under all conditions.

This enables maximum cooling and maximum dehumidification since the hygroscopic solution is more efiective at lower temperatures. A large variation in sea water temperature is generally encountered in the voyage of a ship and consequently produces a large temperature variation in cooling coils 15. However, the cooling coils will still be at the lowest temperature possible for any given conditions. I

It is desired to maintain a maximum concentration of the hygroscopic solution for any temperature to create a maximum drying effect. However, an increased concentration raises the freezing temperature of the solutionand vice versa. Also, for a given concentration, a'temperature drop due to cooler sea water being encountered may freeze or crystallize the solution. This may be overcome by maintaining the solution at a diluted concentration such that the freezing point will be below the temperature of the coolest sea Water to be passed through. The drying etfectiveness of the solution will then be greatly decreased for higher temperatures, however.

With organic hygroscopic solutions'such as the glycols, a'similar problem appears due to solution thickening at very low temperatures and increased carry-out at higher temperatures for concentrated solutions.

To overcome this dilemma, the concentration of the hygroscopic salt solutionis maintained at maximum con: centration for any sea water temperature, and this concentration decreases for lower temperatures. In accomplishing this, two upright,

parallel columns

34 and 35 are employed. Column 34 is filled with a given amount of reference liquid so that the top of it will be at the bottom of plug 36 for the coolest temperatures to which the liquid may be subjected. Plug 36 is'attached to the top of tube 34 by athreaded shank 37 which provides an adjustment for the height of the plug. Two tubes are necessary in marine applications to overcome the roll'of the ship whichsimilarly affects the pressure in each tube and thus nullifies the effect of the rolling.

A cooling jacket-38 surrounds tube 34 through which the hygroscopic solution is passed which is supplied from spray bar 20 or 24 or some other part ofthe washer-- generator unit through a reservoir. The solution then passes throughtube 35 bymeans of pipe 40 and overflows the top of tube 35, into chamber 41, and back to the unit by means of pipe 42.

To assure aconstant flow through jacket 38 and tube 35, a reservoir maybe employed. This consists of an outer receptacle 53, an inner receptacle 54, a drain pipe 55 which leads back to the sump 13, or some other part of the unit, a supply line 56, and an exit line 57 with hole 58 that connects to the cooling jacket 38. The hygroscopic solution is supplied to the inner receptacle 54 from supply line 56. A portion of the solution enters hole 58 and flows by gravity to jacket 38. The remaining fluid overflows inner receptacle 54 into outer receptacle 53 and, hence, to drain pipe 55. A constant head is thus maintained between hole 58 and the top of height of the reference liquid also varies with the tempera ture.- Plug 36 is employed to amplify the height dilfer ence and accordingly vary the pressure in the tube. The

pressures in the two tubes are measured by -a difierential pressure transmitter 43'which is commercially available.

It senses pressure in corresponding portions 'of

tubes

34 and 35 through pipes 39 and; 49. This instrument is set for a pre-determined pressure difierential between the two tubes. Air is supplied to the instrument through line 44 and pressure is maintained in outlet line 45 according to .the actual temperature difierential' in comparison to the set differential. The pressure in line 45 controls the outlet pressure in line 46 leading from a pressure controller 47 which is likewise comniercially available; Air to this is supplied through a line 48. Line 46 is connected to pneumatic valve 33 whose degree of opening is determined bythe pressure in this line.

In operation, a portion of the hygroscopic solution, which is near the temperature of the sea water in coil 15, is slowly passed through jacket 38 and tube 35. If the sea water becomes warmer, for example, the hygroscopic solution and the contents of the two

tubes

34 and 35 accordingly rise in temperature, thus changing their densities. The reference liquid level also rises and this rise is accelerated by the plug 36. The resulting increased pressure in this tube over an'dabove thatin tube 35 causes differential pressure transmitter 43 to increase the pressure to controller 47 which increases the pressure to pneumatic valve 33. This is further opened allowing a greater quantity of the heating medium to' pass through the coil 28 and concentrate the solution to a greater extent. If the sea water temperature becomes cooler, the opposite occurs.

Tube 34 is provided with expansion chamber 50 to limit the maximum height to which the reference liquid may rise. This limits the maximum concentration of the solution to any pre-determined amount and is a simple, effective way to limit the degree of concentration so that the solution will not salt out when shut down and allowed to cool in a cold environment.

Plug 36 may comprise an unlimited number of configurations, an example of which is illustrated in Figure 2'. Here, the plug is larger in diameter near the bottom 51 than at the top 52. During expansion due to heat, the liquid rises faster at lowerternperatures and slows when the liquid level reaches portion 52. Thus the concentration is likewise increased faster at low temperature changes and slows at higher ones. The shape of the plug can be fitted to any rate of change of concentration desired according to the various conditions encountered in the specific situation.

Another form of the controls is schematically illustrated in Figure 3. In this form, two

similar tubes

34 and 35 are employed with similar supply line 57, cooling jacket 38, line 40, drain pipe 42, and expansion chambers 41 and 50. Air is supplied at constant pressure to lines 61 and 62. This air is initially adjusted by means of flow meters 63 and 64 to obtain constant flow in eachof air pipes 65 and extending to the bottomportions of

tubes

34 and 35. The pressure in that portion of the air pipes above the tubes is received by a difierential pressure instrument 67 which maintains a given pressure difierence between the twopipes by controlling the regenerator valve and thus change solution concentration. A thermostatic instrument 68 measures the temperature of the sea water or hygroscopic solution'by means of a bulb 70. This instrument 68 thenresets the pressure diflerence to be maintained by instrument 67 according to the temperature of the sea Water or hygroscopic solution. Instrument 67'has air supplied to it from a line 71 and controls the outlet in. line 72 according to the pressure diflierential. Line- 72 leads directly, in this case, to pneumatically controlled valve 33;

In operation, the reference liquid: in tube 314' ismaintained atwa substantially constant. level by means of expansion chamber 50' and the solution level: in tube 35 is maintained constant byoverflbw chamber 41. The only change in the heads of these liquids is now eiiected by density change due to temperature change. As density increases the heads increase and

pressure inair pipes

65 and 66 likewise rises. The densitiesin both tubes are not similarly afiected and the pressures of the air pipe consequently do not. similarly change; The resultant new differential between the pressures is responded to by instrument 67 and thus changes air pressure in line 72 which further opens or closes valve 33.

As previously mentioned, the difierential control pressure setting in instrument 67 is changed by thermostatic instrument 68 as the temperature changes. The setting of valve 33 is consequently changed to maintain maximum concentration of the hygroscopic solution for any given temperature. In eliect, temperature change is accounted for in the apparatus of Figure l by the height change of the reference liquid and is accounted for in the apparatus of Figure 3 by the thermostatic instrument that changes the control setting of the differential pressure instrument.

Further modifications will be apparent to the reader, such as using sea water in cooling jacket around both tubes to produce temperature change. Many modifications may be made Without departing from scope of our invention or the teachings contained herein.

We claim:

1. Dehumidifying apparatus comprising, in combination: wall means forming, a contact chamber for contacting air to be dehumidified with hygroscopic solution; duct means for passing air to be dehumidified through said chamber; contactor means comprising solution delivery nozzles for contacting air passing. through said chamber with hygroscopic solution; a source of coolant fluid; means for transferring heat from said solution to said coolant fluid whereby to cool said solution for contact with air to be dehumidified; regenerating means for removing water from solution; first control means for controlling the operation of said regenerating means to maintain the concentration of said solution substantially constant; and second control means aflected by the coolant fluid temperature for adjusting the operation of the first control means in a manner to maintain said concentration relatively higher when said coolant fluid is relatively warmer.

2'. Dehnmidifying apparatus for ships comprising, in combination: wall means forming a contactor chamber for contacting air to be dehumidified with hygroscopic solution; duct means forpassing air to be dehumidified through said chamber; an internally cooled heat exchanger disposed in said chamber in the path of said air; sea water duct means for continuously passing sea Water through said heat exchanged to maintain the same substantially at sea water temperature; circulating means for circulating a streamof hygroscopic solution through said chamber and over said heat exchanger in contact with said air; a regenerator for removing excess water from the hygroscopic solution; means for circulating solution from said stream through said regenerator and back to said stream; control means responsive to concentration of the hygroscopic solution and to changes in sea water temperature; and adjusting means for adjusting the operation of said regenerator responsive to said control means to maintain a substantially constant concentration of solution at substantially constant sea water temperature, and to maintain a less concentrated solution at colder sea I Water temperatures.

3. Dehumidifying apparatus comprising in combination: a contactor unit having a first casing, a cooling coil within said first casing through which a cooling medium of varying temperature is passed at a constant rate of flow, first spray means for spraying hygroscopic solution over said coil, first duct means for carrying air to be dehumidified to one portion of said first casing; second duct means for carrying air from another portion of said first casing to the conditioned space and arranged to allow air from said first duct means topass by said coil before entering said second duct means, first blower means for maintaining air flow from said conditioned space through the first and second duct means, and a first drain pipe connecting the bottom of said first casing to a sump; a regenerator unit having a second casing, a heating coil within said second casing through which a heating me dium is passed, valve means for controlling the rate of flow of said heating medium through said heating coil, second spray means for spraying hygroscopic solution over said heating coil, third duct means for carrying air from an outside space to one portion of said second casing, fourth duct means for carrying air from another portion of said second casing to the outside space and arranged to allow air from said third duct means to pass by said heating coil before entering said fourth duct means, second blower means for maintaining a flow of air from said outside space through the third and fourth duct means, and a second drain pipe connecting the bottom of said second casing to a sump; hygroscopic solution; and control means for controlling said valve means, including: a first upright tube containing reference liquid; a second upright tube; a cooling jacket around said first upright tube; an overflow chamber at the top of said second tube; pipe means for carrying hygroscopic solution through said cooling jacket, second tube, and overflow chamber; a plug in said first tube located adjacent the level of said reference liquid contained therein; a differential pressure transmitter operatively connected to corresponding portions of the first and second tubes; and means for controlling said valve means in response to said difierential pressure transmitter.

4. Apparatus according to claim 3 in which said plug is connected to the top of said first tube by means of a threaded shank whereby said plug may be vertically adjusted.

5. Apparatus according to claim 3 in which said plug may be of non-cylindrical contour to vary the amount of change in height of said reference liquid in response to a given change in temperature of said cooling medium.

6. Dehumidifying apparatus comprising in combination: a contactor unit having a first casing, a cooling coil within said first casing through which a cooling medium of varying temperature is passed at a constant rate of flow, first spray means for spraying hygroscopic solution over said coil, first duct means for carrying air to be dehumidified to one portion of said first casing; second duct means for carrying air from another portion of said first casing to the conditioned space and arranged to allow air from said first duct means to pass by said coil before entering said second duct means; first blower means for maintaining air flow from said conditioned space through the first and second duct means, and a first drain pipe connecting the bottom of said first casing to a sump; a regenerator unit having a second casing, a heating coil within said second casing through which a heating medium is passed, valve means for controlling the rate of flow of said heating medium through said heating coil, second spray means for spraying hygroscopic solution over said heating coil, third duct means for carrying air from an outside space to one portion of said second casing, fourth duct means for carrying air from another portion of said second casing to the outside space and arranged to allow air from said third duct means to pass by said heating coil before entering said fourth duct means, second blower means for maintaining a flow of air from said outside space through the third and fourth duct means, and a second drain pipe connecting the bottom of said second casing to a sump; hygroscopic solution in said apparatus; and control means for controlling said valve means, including: first upright tube containing reference liquid; a second upright tube; a cooling jacket around said first upright tube; an overflow chamber at the top of said second tube; pipe means for carrying hygroscopic solution through said cooling jacket, second tube, and overflow chamber; a pressure responsive device for measuring the pressure differential between corresponding points of said tubes; and means for controlling said valve means in response to the measured pressure differential whereby said valve means tends to be more fully opened when said differential increases and tends to be more fully closed when said differential decreases.

References Cited in the file of this patent UNITED STATES PATENTS