Dehumidifier with a plate-type evaporator

Abstract

A dehumidifier has a closed heat-pump circuit with a blower arranged to pass a stream of air through a passage in the dehumidifier in which both the condenser and evaporator exchangers are provided, with the evaporator exchanger upstream of the condenser exchanger. The evaporator exchanger is formed as a plate-type heat exchanger which comprises a stack of like corrugated plates arranged in pairs in a stack. The plates of each pair are mirror symmetrical about a plane passing through the interface between the pairs and therefore define a plurality of parallel and generally horizontal passages through which the humid gas is passed. The corrugations of each plate are parallel to and offset from the corrugations of the immediately adjoining plate of the next pair by a distance equal to half a corrugation width so that there is formed between each pair a vertical generally sinusoidal flat passage through which the coolant is passed. In addition each plate is formed with generally vertical ridges which lie against similar ridges of the plate of the immediately adjoining pair so as to space each pair rigidly from the adjoining pairs. The plates are all made of chromium steel and an aluminum foil is provided at the interface between each pair of plates and is formed with laterally extending V-shaped projections that serve to catch drips and lead them to the bottom of the evaporator whence they are carried away from the dehumidifier.

Description

FIELD OF THE INVENTION

The present invention relates to a dehumidifier. More particularly this invention concerns such a dehumidifier having a closed heat-pump circuit with an upstream evaporator and a downstream condenser arranged in a passage.

BACKGROUND OF THE INVENTION

It is known to dehumidify air or a similar gas by passing a stream of this gas first through a cool heat exchanger which condenses the moisture out of the gas, then by passing it through another heated heat exchanger which returns the gas to its original temperature. This is most simply done by means of a closed-circuit heat pump, wherein the upstream cooled heat exchanger is the evaporator coil and the downstream heated heat exchanger is the condenser coil. An expansion valve is provided on one side between the evaporator and the condenser and a compressor is provided on the other side in the closed circuit.

The evaporator is conventionally a simple tube-type heat exchanger wherein the tubes are provided with ribs or fins for maximum heat-exchange surface. In additon such a evaporator is provided with a separator that catches the liquid condensed from the stream of air and channels it to an outlet drain. Such tube-type exchangers require a relatively large flow cross section in order to obtain sufficient heat exchange so that the dehumidifier must be relatively bulky aand is expensive to manufacture. In addition it is necessary to construct such arrangements out of corrosion-resisting materials, such as expensive chromium-steel alloys, in order to prevent the already expensive evaporator from being rapidly destroyed. Thus the device is quite expensive.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide an improved dehumidifier.

Another object is the provision of such a dehumidifier which is relatively compact and inexpensive.

SUMMARY OF THE INVENTION

These objects are attained in a dehumidifier of the above-described general type wherein the evaporator is a plate-type heat exchanger. Such an arrangement considerably reduces the overall cost of the dehumidifier and at the same time allows it to be built much smaller as the heat-exchange surface area in a plate-type heat exchanger is considerable. In addition the plate construction of such an arrangement eliminates the necessity for providing particular water-separation means as has hitherto been the case.

In accordance with further features of the invention the plates are arranged in pairs with the corrugations of each plate being in line with those of the other plate of the pair, that is with their valleys in line and registering so as to form parallel humid-gas passages. In addition the corrugations of all but the two end plates are offset by half a corrugation width from the adjacent plate of the neighboring pair so that nonstraight transverse passages are formed for the coolant. In addition ridges transverse to the parallel passages are formed on the plates which bear on similar ridges of adjoining plates to keep the plate pairs spaced apart across the nonstraight passages.

Such an arrangement allows relatively large pressure differentials to exist between the coolant passages and the air passages without any possibility of leakage. Similarly, the use of only a single plate shape allows the device to be fabricated relatively inexpensively. Thus a plurality of identical plates are stamped out of stainless steel or the like and are thereafter properly arranged and soldered or welded into a stack that forms a very compact and efficient heat exchanger. The air passages through such an exchanger are relatively large compared to the overall size of the unit so that good cooling and condensing is obtained.

In accordance with another feature of this invention there is provided between each pair and the adjoining pair a thin metallic foil which lies in good heat-conducting contact with both of the pairs so that it forms a secondary heat-exchange surface. In a normal heat-pump arrangement the pressure inside the fluid passages of the condenser will be much greater than that in the air passages so that this thin foil will be clamped tightly in place.

According to another feature of this invention the foil is formed with a plurality of V-shaped projections which extend into the air passages of the plate pairs so as best to make the air flow through the apparatus turbulent and at the same time to catch condensed vapor and conduct it to an outlet at the bottom of the exchanger.

Thus in accordance with this invention the passages for the air being dehumidified are generally straight and the passages for the cooling fluid are nonstraight, here generally sinusoidal.

According to this invention V2A steel is used for the heat-exchanger plates and aluminum is used for the foil and the projections thereon. In accordance with another feature of this invention the transverse passages are inclined relative to the vertical and/or the parallel flow passages are inclined relative to the horizontal so that water separated from the air in the latter passages is collected on the edges of the pairs of plates and can be conducted out of the apparatus. This eliminates the use of a complicated droplet separator as has been known hitherto.

According to yet another feature of this invention the condenser and evaporator are both identically formed, thereby again reducing fabrication costs of the dehumidifier.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a side longitudinal section, partly in diagrammatic form, of a dehumidifier according to the present invention;

FIG. 2 is a side view of the evaporator according to this invention; and

FIGS. 3 and 4 are sections taken along the lines III--III and IV--IV of FIG. 2, respectively.

SPECIFIC DESCRIPTION

As shown in FIG. 1 a dehumidifier comprises a housing 1 formed with a passage 9 having an upstream inlet 6 and a downstream oulet 7 and provided with a plate-type evaporator 2 and a plate-type condenser 4. A fluid is pumped by a compressor 3 in the direction indicated by arrows 26 into the condenser 4 whence it flows through an expansion valve 5, and expands in the evaporator 2. Thereafter the fluid again flows in the closed circuit back to the compressor 3 and the cycle is completed. A fan 10 driven by a motor 16 serves to draw air as shown by arrows 8 in the inlet 6 and expel it from the outlet 7. Water condensed from the air stream is drawn out of the apparatus at 11.

Thus the air stream is cooled in the evaporator 2 and the moisture therein is stripped therefrom. Thereafter the same air stream is heated in the condenser 4 and expelled from the apparatus at substantially the same temperature it entered.

The evaporator 2, shown in side view in FIG. 2, comprises a stack of like corrugated plates, four of which are shown at 12-15 in FIGS. 2-4. These plates are arranged in pairs 12, 13 and 14, 15 with each plate being mirror symmetrical to the other plate of the pair across a plane P lying at the interface between the two plates. Thus the valleys of the corrugations of each plate lie against the valleys of the other plate of the respective pair. Each of the plates 12 and 14 is offset by a distance d equal to one-half of the corrugation width D from the other plate 13 and 15 respectively, so that the crests of each plate are aligned with the valleys or troughs of the plate of the neighboring pair.

The edges of the plates 12-15 are here alternately connected with the edge of one or the other of the respective neighboring plates by means of welded seams 27. The corrugations of one plate pair 12, 13 and 14, 15 are so arranged relative to each other that flow passages 18 are formed between the plates through which humid air flows according to arrows 8.

Transverse to these parallel passages 18 there are transverse ridges or crests 19 stamped in the plates 12-15 which connect the parallel passages 18 with one another and allow the plates 13 and 14 of the pairs 12, 13 and 14, 15 to abut one another firmly. Thus additional support devices between neighboring plate pairs such as spacer bars or the like are not needed.

Between the plates 12-15 of the plate pairs 12, 13 and 14, 15 thin foils 20 are inserted which are made of aluminum and 0.2 mm thick. The foils 20 are formed in the passages 19 with V-shaped projections 21 which create turbulence and catch drops. The water caught on the projections 21 flows by gravity downwardly and collects in the lowermost passage 22 parallel to the passages 18 and is there caused to run out of the machine as shown by arrow 23. A wall 28 perpendicular to the flow direction 8 and downstream of the passage 22 serves to catch this water and connect it to the water outlet 11 as shown in FIG. 1.

In this case the transverse passages 19 and the parallel passages 18 are inclined relative to the vertical and horizontal, indicated by dot dash lines V and H respectively, so that the water flows off them.

In order to improve the separation of the water from the air stream the parallel passages 18 of the plates 12-15 are somewhat deeper in the region of the transverse passages 19 so that here a narrowed flow cross section 24 exists such that the flow is directed against the V-shaped projections 21. Between neighboring plate pairs 12, 13 and 14, 15 sinusoidal passages 25 are formed through which the cooling fluid flows from the expansion valve 5 according to arrows 26. The cooling fluid draws heat out of the plates 12-15 and the foil 20 with the projections 21 and thereby condenses liquid out of the humid gas passing through the evaporator 2. This produces cold and dry air. Thereafter the cooling fluid is compressed and heated up so that it serves to heat the condenser 4 and thereby warms up the cold and dry air so as to produce warm dry air approximately the same temperature as the input air.

Claims

I claim:

1. A dehumidifier comprising:

a housing forming a passage having an inlet and an outlet;

means for passing a current of humid gas through said passage from said inlet to said outlet;

a plate-type evaporator in said passage traversed by said current;

a plate-type condenser in said passage traversed by said current after it has passed through said evaporator, said evaporator and said condenser being connected in a closed coolant circuit;

pump and valve means in said circuit for compressing a coolant fluid and feeding same to said condenser and thereafter feeding same to said evaporator, said evaporator being formed of a stack of generally similar and generally planar plates each formed with a plurality of regular corrugations having crests spaced from the plane of the respective plate and valleys at the respective plane, said plates being disposed in pairs with the valleys of one plate of each pair turned inwardly toward and registering with the valleys of the other plate of the pair, whereby a plurality of parallel passages are formed between the plates of each pair between the corrugations thereof, the crests of each plate turned toward plate being in line with the valleys thereof, whereby a plurality of nonstraight passages transverse to said parallel passages are formed between confronting plates of adjoining pairs, each of said plates being formed with a plurality of ridges projecting from the respective plate plane and abutting a respective ridge of the adjoining plate of the neighboring pair.

2. The dehumidifier defined in claim 1, wherein said evaporator further comprises a thin metallic foil sandwiched between the plates of each pair.

3. The dehumidifier defined in claim 2 wherein said foil is formed with a V-shaped projection at each of said ridges.

4. The dehumidifier defined in claim 1 wherein said passages are each formed with a narrow waist between said ridges, said waists constituting restrictions in said passages.

5. The dehumidifier defined in claim 1 wherein said pump and valve means are connected through said nonstraight passages for forcing said fluid therethrough, said humid gas being passed through said parallel passages.

6. The dehumidifier defined in claim 1 wherein said passages are inclined to the horizontal, said dehumidifier further comprising means for collecting condensate from the lower edges of said plates.

7. The dehumidifier defined in claim 1 wherein said condenser is substantially identical to said evaporator.

8. The dehumidifier defined in claim 1 wherein said pump and valve means are provided in said housing.

9. The dehumidifier defined in claim 8 wherein said means for passing a current of gas is a fan in said passage.