Passive Antifreeze Air Vent for Freezing PEM Fuel Cell Back Pressure
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Solution Overview
Problem
Existing PEM fuel cell power plants face operational issues during freezing conditions due to mechanical valves and nozzles in the air bleed line freezing, leading to system shutdown, and require additional heating equipment for resolution.
Innovation Solution
A passive air vent system using a hydrophobic porous body and an antifreeze column to separate and vent humid air without mechanical devices, maintaining back pressure control through a column of immiscible antifreeze that prevents water dilution and allows air to bubble through, allowing operation at freezing temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical valves and nozzles are used in the air bleed line to control back pressure, then air flow control is achieved during normal operation, but the valves and nozzles freeze up during freezing conditions, causing system shutdown
Solution Approach 1:
The patent replaces mechanical valves and nozzles with a hydrophobic porous body that uses surface tension and wettability properties to control air flow. The hydrophobic material inherently prevents water condensation and freezing by repelling water molecules, eliminating the freezing problem associated with mechanical components while maintaining air flow control functionality.
Solution Approach 2:
The patent employs a hydrophobic porous body with specific pore size and surface properties to control air flow through capillary pressure. The porous structure allows air molecules to pass through while preventing water condensation and freezing by maintaining positive back pressure and utilizing the hydrophobic surface energy to repel water.
2Object-affected harmful factors
If heating equipment is added to prevent freezing of the air bleed line, then freezing is prevented, but system complexity and cost increase
Solution Approach 1:
The patent eliminates the need for heating equipment by replacing mechanical valves with a hydrophobic porous body that passively prevents freezing through its material properties. The hydrophobic surface energy inherently repels water, preventing condensation and freezing without requiring external heating systems, thereby reducing system complexity and cost.
Solution Approach 2:
The hydrophobic porous body serves itself by using its inherent material properties to prevent freezing. The surface tension and wettability characteristics of the hydrophobic material automatically prevent water condensation and freezing, eliminating the need for additional heating equipment or active control systems.
3Device complexity
If a passive air vent system with hydrophobic porous body is used, then freezing is prevented and system complexity is reduced, but back pressure control must be maintained through antifreeze column design
Solution Approach 1:
The patent uses a hydrophobic porous body with carefully controlled pore size, porosity, and surface energy to achieve both back pressure control and freezing prevention. The porous structure creates capillary pressure that maintains positive back pressure while the hydrophobic surface properties prevent water condensation and freezing, combining multiple functions in a single component.
Solution Approach 2:
The patent controls back pressure by adjusting parameters of the hydrophobic porous body including pore size, porosity, and surface energy. By optimizing these parameters, the system achieves the desired back pressure control and freezing prevention characteristics without requiring complex mechanical systems or additional components.
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
The system effectively vents air at freezing temperatures without mechanical components, ensuring continuous operation and reducing system complexity and cost by using a passive, non-frost-prone antifreeze column to manage back pressure.
Implementation Method 1
The air and water components of the cathode effluent mixture are passed through a condenser where water is condensed out of the mixture. The resultant water/air mixture is then passed through a separator station where the condensed water is removed from the mixture and air is vented out of the fuel cell assembly.
Implementation Method 2
The air stream which is vented from the separator is humid after leaving the condenser. This fact causes operational problems during freezing conditions since the valves and/or nozzles in the air bleed line can freeze up so that air flow can no longer be properly controlled from the system
Implementation Method 3
The water vapor and air components of the cathode effluent mixture are passed through a condenser where water is condensed out of the mixture.
Implementation Method 4
The cell is cooled by water which flows through the porous plate to the air stream and evaporates therein so as to cool the cell.
Data Source
AI summary
A PEM fuel cell (4) power plant includes a passive air vent (24) through which air separated from a cathode effluent stream can be expelled from the power plant. The air vent operates satisfactorily during ambient freezing conditions thus it is eminently suitable for use in mobile applications such as in PEM fuel cell-powered automobiles, buses, or the like. The vent is formed from a liquid antifreeze layer (40) that is disposed in a sparging tank (36) which communicates with ambient surroundings. Any water vapor in the stream can condense out of the gas-stream in the antifreeze. In order to facilitate this result, the antifreeze can be a liquid that is immiscible with water so that the condensed water will form a separate layer (38) in the sparging tank.