HUMIDIFIER, PLATE, DEVICE, AND MOTOR VEHICLE

Abstract

A humidifier, a device including a fuel cell, and a motor vehicle. The humidifier of the includes at least one humidifying duct and is designed in such a way that a first gas to be humidified can be conducted in the humidifying duct in a direction of flow and, separated by a water-permeable material, past a humidifying second gas so that water is transferred from the second gas to the first gas. The humidifier includes a cross-sectional area of the humidifying duct available to the first gas tapers in the direction of flow. The fact that the cross-sectional area tapers results in a drop in pressure along the humidifying duct, and the drop in pressure reduces, compensates or overcompensates an increase in pressure resulting from the increasing humidification, so the partial difference in pressure between the first gas and the second gas remains large over the distance of the humidifying duct in spite of the transfer of humidity.

Claims

1-9. (canceled)

10. A humidifier comprising: at least one humidification channel, a first gas to be humidified in the humidification channel being leadable in a flow direction and, separated by a water-permeable material, past a humidifying second gas so that water is transferred from the second gas into the first gas, a cross-sectional area of the humidification channel available to the first gas decreasing in the flow direction.

11. The humidifier as recited in claim 11 further comprising a housing, the humidification channel being delimited via the housing, and a plurality of hollow fibers, made of the water-permeable material, for passing the second gas through, the hollow fibers in the housing extending perpendicularly with respect to the flow direction, a packing density of the hollow fibers being constant in the flow direction, and the housing tapering in the flow direction.

12. A plate made of water-permeable material, the plate comprising: webs on a flat side extending in a flow direction and delimiting a humidification channel, a distance between the webs decreasing monotonically in the flow direction.

13. The plate as recited in claim 12 wherein a plurality of the webs delimit the humidification channel and at least one further mutually parallel humidification channel, widths of the webs monotonically increasing in the flow direction, so that cross-sectional areas of the humidification channel and the at least one further humidification channel decrease in the flow direction.

14. The plate as recited in claim 13 wherein the plate includes further webs extending in the flow direction on an other flat side.

15. The plate as recited in claim 14 wherein widths of the further webs on the other flat side increase monotonically in the flow direction.

16. A humidifier comprising: at least one plate as recited in claim 12, a first gas to be humidified in the humidification channel being leadable in a flow direction and, separated by a water-permeable material, past a humidifying second gas so that water is transferred from the second gas into the first gas, a cross-sectional area of the humidification channel available to the first gas decreasing in the flow direction.

17. A device comprising a fuel cell and a humidifier as recited in claim 10 for humidifying supply air for the fuel cell with the aid of exhaust gas of the fuel cell.

18. A motor vehicle comprising the device as recited in claim 17.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is explained below in exemplary embodiments with reference to the appended drawings.

[0021] FIG. 1 shows a first humidifier according to the prior art,

[0022] FIG. 2 shows a second humidifier which represents one exemplary embodiment of the present invention,

[0023] FIG. 3 shows a first plate according to the prior art made of water-permeable material, in a top view,

[0024] FIG. 4 shows the first plate in a sectional view,

[0025] FIG. 5 shows a second plate made of water-permeable material in a top view, the second plate representing one exemplary embodiment of the present invention, and

[0026] FIG. 6 shows the second plate according to the present invention in a sectional view.

DETAILED DESCRIPTION

[0027] First humidifier 10 according to the prior art shown in FIG. 1 includes a housing 20 in which a hollow fiber bundle containing parallel hollow fibers 130 is situated. The density of hollow fibers 130 in the bundle is constant.

[0028] Housing 20 shown is cylindrical with a rectangular base surface, and delimits a humidification channel which extends in a flow direction in parallel to the base surfaces. In humidifier 10 shown, hollow fibers 130 extend perpendicularly with respect to the base walls, and thus perpendicularly with respect to the flow direction and in parallel to the side walls of the housing. Two of the side walls, which do not adjoin one another and which are thus in parallel to one another in the example, include a first gas inlet and a first gas outlet through which a first gas may be led into housing 20 and out of the housing, respectively.

[0029] The second gas may be led from a second gas inlet to a second gas outlet. In the illustrated example, the ends of the hollow fibers form the second gas inlet and the second gas outlet.

[0030] Hollow fibers 130 are arranged in housing 20 with a uniform density. Hollow fibers 130 are made of water-permeable material, and allow the capillary passage of moisture, but not gas, through pores in the material. This allows moist gas, for example, to be led through hollow fibers 130, and gas to be humidified to be led around hollow fibers 130. Alternatively, gas to be humidified is led through hollow fibers 130, and moist gas is led around hollow fibers 130.

[0031] FIG. 2 shows a second humidifier 100 with a housing 200, which represents one exemplary embodiment of the present invention, for a fuel cell 1000 in a vehicle 1100, shown schematically. Shown housing 200 of second humidifier 100 includes humidification channel 210, and is cylindrical. A hollow fiber bundle containing parallel hollow fibers 130 is situated in housing 200. A density of hollow fibers 130 in the bundle is constant. In the exemplary embodiment of humidifier 100 according to the present invention, base walls 110, 120 of the housing are trapezoidal. Once again, hollow fibers 130 extend perpendicularly with respect to the base walls, and thus in parallel to the side walls of housing 200, which in addition to mutually parallel base walls 110, 120 includes a pair of parallel side walls 140, 150 and a pair of nonparallel side walls. The pair of parallel side walls 140, 150 includes the first gas inlet and the first gas outlet, through which a first gas may be led into housing 200 and out of housing 200, respectively. The flow direction from the first gas inlet to the first gas outlet is perpendicular to the direction of extension of hollow fibers 130. The area density of hollow fibers 130 in housing 100 is constant in each plane perpendicular to the flow direction, in which the first gas to be humidified is led. A first gas inlet, through which the first gas is led into the humidification channel, is included by larger parallel side wall 140, and a first gas outlet, through which the first gas is led out of the humidification channel, is included by smaller parallel side wall 150. Therefore, a cross-sectional area of the humidification channel decreases in the flow direction.

[0032] Hollow fibers 130 are made of water-permeable material, and allow the capillary passage of moisture, but not gas, through pores in the material.

[0033] When first gas to be humidified in housing 200 now flows around hollow fibers 130 from the first gas inlet to the first gas outlet, and moist second gas flows through hollow fibers 130, the partial pressure difference of the moisture between the first gas and the second gas remains large, since the pressure reduction due to the change in cross-sectional area reduces, compensates for, or overcompensates for the increase in partial pressure of the moisture in the first gas on account of the transfer of moisture during flow around the hollow fibers. The remaining partial pressure difference effectuates uniformly good transfer of moisture from the second gas to the first gas.

[0034] FIG. 3 shows a first plate 40 according to the prior art made of water-permeable material, in a top view, and FIG. 4 shows first plate 40 in a sectional view along the line denoted by reference character A in FIG. 3. Such a plate 40 made of water-permeable material, which allows the capillary passage of moisture through pores in the material, is also referred to as a membrane humidifier plate.

[0035] Webs 41, 42 which protrude at the same height and extend in parallel to one another, forming open channels 51, 61, are formed on the flat sides of plate 40. Each of webs 41, 42 has a constant width and each of channels 51, 61 has a constant width, whereby different webs 41, 42 and/or channels 51, 61 may have different widths. When channels 51, 61 are closed off by situating plate 40 in a housing, the first gas to be humidified may be led through channels 51 on one of the flat sides of plate 40, and the humidifying second gas may be led in counterflow through channels 61 on the other flat side of plate 40. Due to the partial pressure difference of the water between the first gas and the second gas, moisture diffuses through the plate and humidifies the first gas.

[0036] FIG. 5 shows a second plate 400 made of water-permeable material which allows the capillary passage of moisture through pores in the material, in a top view, and FIG. 6 shows second plate 400 in a sectional view along the line denoted by reference character B in FIG. 5. Plate 400 illustrated in FIGS. 5 and 6 represents one exemplary embodiment of the present invention.

[0037] Once again, webs 410, 420 which protrude at the same height, forming open channels 510, 610, are formed on the flat sides of plate 400. Although channels 510, 610 extend essentially in parallel, the side walls of channels 510, 610 do not, since the width of channels 510, 610 changes linearly over the length of plate 500. This is achieved by webs 510, 610 410, 420 which become wider linearly over the length of plate 500.

[0038] Webs 410 taper on the one flat side of plate 100, in the opposite direction from webs 420 on the other flat side. However, it is also possible for webs 410 on the one flat side of plate 100 to taper in the same direction as webs 420 on the other flat side.

[0039] It is also possible for each web 410, 420 between two channels 510, 610 to be replaced by two nonparallel auxiliary webs, between which a free space remains which is not utilized as a channel.

[0040] Plate 400 is made of water-permeable material, and allows the capillary passage of moisture, but not gas, through pores in the material.

[0041] When the channels are closed off due to situating plate 400 in a housing, the first gas to be humidified may be led through channels 510 on one of the flat sides of the plate, and the humidifying second gas may be led in counterflow through channels 610 on the other flat side of the plate. Due to the partial pressure difference of the water between the first gas and the second gas, moisture diffuses through the plate and humidifies the first gas. In the process, the partial pressure difference over the entire distance remains large enough for an effective transfer of moisture, and good humidification of the first gas and/or dehumidification of the second gas.

[0042] In the exemplary embodiments illustrated and described, the width or cross-sectional area of the channel(s) for the passage of the gas to be humidified changes linearly. However, other changes in width are possible within the meaning of the present invention. The effect according to the present invention is based on the reduction in the channel width or the channel cross section in the flow direction. For the effect according to the present invention, it is sufficient if a channel width or a channel cross section on an inlet side, on which the gas to be humidified is supplied to the channel, is larger than on an outlet side, on which the humidified gas is discharged from the channel.

LIST OF REFERENCE NUMERALS

[0043] 10, 100 humidifier

[0044] 20, 200 housing

[0045] 210 humidification channel

[0046] 110, 120 base walls

[0047] 130 water-permeable material, designed as a hollow fiber or as a plate with webs

[0048] 140, 150 parallel side walls of the housing

[0049] 40, 400 plate

[0050] 41, 42 webs of constant width

[0051] 410, 420 webs with variable width

[0052] 51, 61 channels of constant width

[0053] 510, 610 channels with variable width