Cooling System for at Least One Fuel Cell of a Fuel Cell System and Method for Cooling at Least One Fuel Cell

Abstract

A cooling system for a fuel cell of a fuel cell system includes a cooling circuit that includes at least one heat exchanger and the fuel cell. The cooling system also includes at least two pumping devices, arranged in the cooling circuit, whereby the at least two pumping devices at least sometimes jointly deliver coolant into the cooling circuit.

Claims

1. A cooling system for a fuel cell of a fuel cell system, the cooling system comprising: a cooling circuit that includes at least one heat exchanger and the fuel cell; and at least two pumping devices, arranged in the cooling circuit, wherein the at least two pumping devices at least sometimes jointly deliver coolant into the cooling circuit.

2. The cooling system as claimed in claim 1, wherein the at least two pumping devices comprises a first pumping device that is provided upstream of the fuel cell and downstream of the heat exchanger, and a second pumping device that is provided downstream of the least one fuel cell and upstream of the heat exchanger.

3. The cooling system as claimed in claim 1, wherein the at least two pumping devices are identical in design.

4. The cooling system as claimed in claim 1, wherein the cooling circuit further comprises a bypass that branches off of a fuel cell discharge line downstream of the fuel cell and upstream of the heat exchanger, and wherein the bypass opens in a fuel cell feed line upstream of the fuel cell and downstream of the heat exchanger.

5. The cooling system as claimed in claim 2, wherein the cooling circuit further comprises a bypass that branches off of a fuel cell discharge line downstream of the fuel cell and upstream of the heat exchanger, and wherein the bypass opens in a fuel cell feed line upstream of the fuel cell and downstream of the heat exchanger.

6. The cooling system as claimed in claim 4, wherein the first pumping device is arranged upstream of the fuel cell and downstream of the mouth of the bypass, and wherein the second pumping device is arranged downstream of the branch-off of the bypass and upstream of the heat exchanger.

7. The cooling system as claimed in claim 5, wherein the first pumping device is arranged upstream of the fuel cell and downstream of the mouth of the bypass, and wherein the second pumping device is arranged downstream of the branch-off of the bypass and upstream of the heat exchanger.

8. The cooling system as claimed in claim 4, further comprising a feed line valve arranged in the fuel cell feed line upstream of the first pumping device in a mouth of the bypass.

9. The cooling system as claimed in claim 4, wherein a bypass valve is arranged in the bypass.

10. The cooling system as claimed in claim 6, further comprising a feed line valve arranged in the fuel cell feed line upstream of the first pumping device in a mouth of the bypass.

11. The cooling system as claimed in claim 6, wherein a bypass valve is arranged in the bypass.

12. A method for cooling a fuel cell of a fuel cell system with a cooling system having a cooling circuit comprising at least one heat exchanger and the fuel cell, and wherein the cooling system also comprises a first pumping device and a second pumping device arranged in the cooling circuit, wherein the first and second pumping devices at least sometimes jointly deliver coolant into the cooling circuit, the method comprising the acts of: delivering, in a warming-up phase of the fuel cell, cooling liquid by the first pumping device, wherein the second pumping device at the same time delivers substantially no cooling liquid, and wherein at the same time the feed line valve is closed.

13. The method as claimed in claim 12, generating, by the first pumping device during an operating phase of the fuel cell, a greater suction pressure than the second pumping device.

14. The method as claimed in claim 12, wherein the first and second pumping devices are operated at different rotational speeds, and wherein the first pumping device is operated at a higher rotational speed than the second pumping device.

15. The method as claimed in claim 13, wherein the first and second pumping devices are operated at different rotational speeds, and wherein the first pumping device is operated at a higher rotational speed than the second pumping device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows a coolant circuit according to the prior art, and

[0027] FIGS. 2-4 show one or more embodiments of a cooling system according to the technology disclosed herein.

DETAILED DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 shows a cooling system as shown in DE 11 2006 001 348 B4. The cooling system comprises a cooling circuit 210, 220 with a cooler 300, which can be supported by a fan 310, and fuel cells of a fuel cell system which are combined into a fuel cell stack. In the feed line 220, the pumping device P1 is arranged between the three-way valve 234 and the fuel cell stack. The pumping device P1 is designed in such a manner that it can provide adequate coolant both during the warming-up phase and also during the normal cooling or operating phase. Because of the low operating temperature of the fuel cell 100, a comparatively powerful pumping device is necessary, which is operated with a voltage above the vehicle electrical system voltage. During the warming-up phase, the three-way valve closes the flow path 224 and makes possible a bypass flow via the flow paths 212, 230 and 222.

[0029] FIG. 2 shows a cooling system according to the technology disclosed here and two same pumps P1, P2 are provided here in the cooling circuit 210, 220. The first pumping device P1 is located in the flow path 222 between the fuel cell stack comprising at least one fuel cell 100 and the mouth 234 of the bypass 230. The second pumping device P2 of identical design is arranged in the flow path 214, which connects the branch-off 232 of the bypass 230 with the heat exchanger 300. In the bypass 230, the non-return valve or bypass valve V2 is arranged. The non-return valve V2 is configured so that it allows a coolant flow from the branch-off 232 to pass through to the mouth 234, whereas it blocks this in the opposite direction.

[0030] Furthermore, a feed line valve V1 is provided in the flow path 224 in the configuration shown here. The flow path 224 connects the heat exchanger 300 with the mouth 234 of the bypass 230. The shut-off valve V1 prevents, in the closed state, a coolant flow through the heat exchanger 300. The coolant then flows out of the fuel cell stack 100 via the flow path 212 into the bypass 230 and the pumping device P1 sucks the coolant out of the bypass 230 and delivers it to the fuel cell 100 via the flow path 222.

[0031] Not shown in the FIGS. 1 to 3 is the heat exchanger or the heating device, which during the warming-up phase warms up the coolant and ultimately the fuel cell 100. During the cooling or operating phase, the pumping device P2 delivers the coolant to the cooler 300. In the cooler 300, the coolant cools down before it is again delivered into the fuel cell via the feed line 220. The two pumping devices P1, P2 are connected in series here and together provide the necessary pumping performance in order to deliver the necessary pressure stroke and the necessary volumetric flow. Each pumping device P1, P2 on its own has to provide less performance than the pumping device according to the prior art, (see FIG. 1).

[0032] As shown in FIG. 3, the bypass valve V2 can also be omitted when for example the pumping devices P1, P2 are activated in such a manner that in the cooling or operating phase of the at least one fuel cell 100, no or only insignificant quantities of coolant flow from the feed line 220 into the discharge line 210 via the bypass 230. This can be achieved for example in that during a cooling or operating phase of the at least one fuel cell 100 the first pumping device P1 generates a greater suction pressure Δp1 than the second pumping device P2.

[0033] As shown in FIG. 4, different suction pressures Δp1, Δp2 can be generated for two pumps P1, P2 of identical design, in that the pumps P1, P2 of identical design are operated at different rotational speeds n1, n2. When for example the pump P1 is operated at the rotational speed n1, a greater suction pressure Δp1 is obtained for a constant volumetric flow than for the second pumping device P2 which is operated at a lower rotational speed n2 with the same volumetric flow. The two pumping devices P1, P2 are connected in series. Because of the greater suction pressure Δp1 of the first pumping device P1, no coolant flows through the bypass 230. Consequently, the volumetric flows, which flow through the two pumping devices P1, P2 are approximately identical. The feed line valve V1 shown here can be embodied for example as shut-off valve V1 (see FIG. 2).

[0034] With the technology disclosed here, comparatively expensive three-way valves can be omitted. In its place, comparatively simple and cost-effective valves are employed. Altogether, the manufacturing and service costs can be further lowered by way of the technology disclosed here.

[0035] Provided the technology disclosed here was disclosed in the singular, the plurality shall also be encompassed at the same time. If for example a fuel cell or a heat exchanger is discussed, their plurality shall also be included at the same time. The preceding description of the present invention only serves for illustration purposes and not for the purpose of restricting the invention. Within the scope of the invention, various changes and modifications are possible without leaving the scope of the invention and their equivalents.

[0036] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.