Fuel Cell Stack Humidifying Water Pressure Control During Shutdown
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The issue of humidifying water freezing and expanding within a fuel cell stack during shutdown, potentially damaging pipes and devices, is not adequately addressed in existing fuel cell systems.
Innovation Solution
A fuel cell system design that includes a humidifying water tank connected to the oxidant gas discharge line, with a pressure regulation valve and a humidifying water supply and discharge system, ensures that humidifying water is maintained at a pressure higher than atmospheric pressure, preventing freezing and expansion by using the oxidant gas to discharge excess water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deionized water is used as humidifying water to prevent electrode deterioration, then electrode performance is maintained, but the water may freeze and expand during shutdown, causing damage to pipes and devices
Solution Approach 1:
The patent extracts and removes the humidifying water from the fuel cell stack before shutdown by controlling a discharge valve to open the water discharge path. This prevents the water from remaining in the system where it could freeze and expand, thereby eliminating the harmful effect while maintaining the benefit of using deionized water during operation
Solution Approach 2:
The patent performs preliminary drainage of humidifying water from the fuel cell stack before the freezing condition occurs. By detecting shutdown conditions and actively draining water in advance, the system prevents the harmful freezing effect before it can occur, while ensuring water is present when needed for electrode performance
2Temperature
If humidifying water flow rate is increased to enhance cooling function, then cooling performance is improved, but more water remains in the system, increasing freezing risk during shutdown
Solution Approach 1:
The patent employs a control unit that monitors system conditions and automatically adjusts the discharge valve based on feedback signals. When shutdown is detected, the control unit activates the discharge path to remove excess water, providing adaptive protection against freezing while allowing high flow rates during operation for optimal cooling
3Productivity
If humidifying water is supplied continuously to maintain moisture management, then fuel cell performance is optimized, but water accumulation increases the risk of freezing damage during shutdown
Solution Approach 1:
The patent dynamically switches the water discharge valve between closed and open states based on operational conditions. During normal operation, the valve remains closed to maintain moisture management and optimize performance. During shutdown, the valve opens to drain water and prevent freezing, thus adapting the system behavior to current operational needs
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
Prevents damage to the fuel cell stack by freezing and expansion of humidifying water, while maintaining efficient power generation and discharge efficiency by regulating water pressure and flow.
Implementation Method 1
a pressure regulation valve, and a humidifying water supply and discharge system, ensures that humidifying water is maintained at a pressure higher than atmospheric pressure
Implementation Method 2
the humidifying water tank is connected to a part of the oxidant gas discharge line
Implementation Method 3
some of the humidifying water evaporates. Thus, evaporative latent heat of the water can cool the fuel cell stack
Implementation Method 4
since sensible heat of the humidifying water can also cool the fuel cell stack
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A fuel cell system according to an embodiment includes a fuel cell stack, an oxidant gas supply and drive unit, an oxidant gas discharge line, a first gas pressure regulation unit, a sealable humidifying water tank, a humidifying water supply line, and a humidifying water discharge line. The humidifying water tank is connected to a part of the oxidant gas discharge line, which is upstream of the first gas pressure regulation unit, and stores humidifying water to be supplied to the fuel cell stack. The humidifying water supply line supplies the humidifying water from the humidifying water tank to the fuel cell stack. The humidifying water discharge line discharges the humidifying water from the fuel cell stack outside the fuel cell system.