Fuel Cell Membrane Humidifier With Bidirectional Off-Gas Flow
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Solution Overview
Problem
The existing fuel cell membrane humidifiers experience a decrease in humidification efficiency due to the off-gas taking a considerable amount of time to flow in and out, leading to a gradual decrease in the concentration of materials transmitted through the hollow fiber membranes, which reduces the overall fuel cell performance.
Innovation Solution
A fuel cell membrane humidifier design that includes a mid-case with off-gas inlets and outlets on both sides, partitioned into separate spaces with discharge guide members to prevent direct discharge and facilitate off-gas flow in both directions, ensuring effective moisture exchange with the hollow fiber membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If off-gas flows through the humidifier in a single direction from one inlet to one outlet, then the structure is simple, but the concentration of materials transmitted through the hollow fiber membranes decreases gradually along the flow path, reducing humidification efficiency
Solution Approach 1:
The humidifier is divided into multiple flow path segments by providing both first and second off-gas inlets and outlets. The off-gas flow path is segmented into a first flow path (first inlet to first outlet) and a second flow path (second inlet to second outlet), allowing independent concentration gradients in each segment and preventing the gradual concentration decrease that occurs in single-path designs.
Solution Approach 2:
The invention transitions from a one-dimensional linear flow path to a two-dimensional multi-path flow configuration. By adding parallel flow paths with separate inlets and outlets, the system creates multiple dimensional flow routes that maintain high material concentration throughout the entire humidifier volume, rather than allowing concentration to deplete along a single linear path.
2Quantity of substance
If off-gas flow path is extended to improve moisture exchange, then humidification performance improves, but the concentration of materials transmitted through the membranes decreases over time, reducing overall efficiency
Solution Approach 1:
The extended flow path is segmented into multiple independent sections (first and second flow paths), each maintaining its own concentration gradient. This segmentation allows the system to extend the total moisture exchange capacity without suffering from the cumulative concentration depletion that would occur in a single extended path, as each segment operates with fresh high-concentration off-gas.
3Ease of manufacture
If the humidifier uses a compact design with fewer inlets and outlets, then manufacturing cost is reduced, but off-gas residence time is insufficient, leading to poor moisture exchange
Solution Approach 1:
The invention merges multiple flow paths into a single integrated humidifier structure with shared hollow fiber membrane bundles. While the internal flow path is extended through multiple inlets and outlets, the overall device remains compact by combining the membrane bundles and flow channels into one unified structure, maintaining reasonable manufacturing complexity while achieving extended residence time.
4Speed
If off-gas flows through the humidifier quickly, then the system responds rapidly, but moisture exchange is insufficient, reducing humidification efficiency
Solution Approach 1:
The off-gas flow is segmented into multiple parallel paths, allowing different flow velocities in different sections. The system can maintain higher overall flow speed for rapid response while ensuring sufficient residence time in each segmented path for effective moisture exchange, as the parallel structure prevents the trade-off between speed and exchange efficiency that plagues single-path designs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design minimizes the decrease in concentration of materials transmitted through the hollow fiber membranes, thereby improving the overall efficiency of the fuel cell by allowing off-gas to flow in both directions and maintaining consistent moisture exchange.
Implementation Method 1
a selective permeable membrane used in the membrane humidification scheme is preferably a hollow fiber membrane having a large permeable area per unit volume
Implementation Method 2
moisture exchange with the hollow fiber membranes
Data Source
AI summary
The present invention relates to a fuel cell membrane humidifier, into which an exhaust gas discharged from a fuel cell stack is bidirectionally introduced to improve the humidification efficiency, and a fuel cell system comprising same. The fuel cell system according to an embodiment of the present invention comprises: a blower for supplying dry gas; a fuel cell stack; and a fuel cell membrane humidifier including a mid-case, a first exhaust gas inlet formed at one side of one surface of the mid-case, a second exhaust gas inlet formed at the other side of the one surface of the mid-case, a first exhaust gas outlet formed at one side of the other surface of the mid-case, and a second exhaust gas outlet formed at the other side of the other surface of the mid-case.