Fuel Cell Cathode Air Cooling for Water Transfer Efficiency
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Solution Overview
Problem
Existing fuel cell systems face inefficiencies in controlling cathode inlet air humidity, leading to decreased water transfer efficiency in water vapor transfer units, which can be costly and packaging-intensive to overcome, especially when relative humidity is below 100%, and temperature management is inadequate for optimal humidity absorption.
Innovation Solution
A fuel cell system employing a gas/liquid heat exchanger and charge air cooler to reduce cathode inlet air temperature, allowing for increased moisture absorption in the water vapor transfer unit, with optional by-pass valves and dual charge air coolers for temperature control during start-ups and varying operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of the water vapor transfer unit is increased to improve water transfer efficiency, then water transfer efficiency is improved, but device complexity and packaging space requirements increase
Solution Approach 1:
The patent changes the temperature parameter of the cathode inlet air by introducing a charge air cooler before the WVT unit. By cooling the inlet air temperature, the air's capacity to absorb water vapor increases, which improves water transfer efficiency without requiring an increase in WVT unit size. This parameter change resolves the contradiction by achieving better performance through temperature optimization rather than size increase.
2Power
If the cathode inlet air temperature is increased, then the fuel cell power output is improved, but the water vapor absorption capacity of the inlet air decreases
Solution Approach 1:
The patent applies preliminary cooling action to the cathode inlet air before it enters the WVT unit. The charge air cooler pre-cools the compressed air, creating optimal conditions for water vapor absorption in the subsequent WVT unit. This preliminary action ensures that the air has maximum capacity to absorb water vapor, resolving the contradiction between power output requirements and vapor absorption capacity.
Solution Approach 2:
The system dynamically adjusts the cooling degree of the charge air cooler based on operating conditions. By making the cooling process dynamic and adaptive, the system can optimize the balance between maintaining sufficient power output and ensuring adequate water vapor absorption capacity under varying temperature and load conditions.
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
Enhances water transfer efficiency without increasing the size of the water vapor transfer unit, maintaining desired humidity levels while optimizing temperature control for improved fuel cell operation, reducing costs and packaging issues.
Implementation Method 1
a gas/liquid heat exchanger and a charge air cooler for reducing the temperature of the cathode inlet air
Implementation Method 2
Water in the cathode exhaust gas at one side of the membrane is absorbed by the membrane and transferred to the cathode air stream at the other side of the membrane
Data Source
AI summary
A fuel cell system that employs a heat exchanger and a charge air cooler for reducing the temperature of the cathode inlet air to a fuel cell stack during certain system operating conditions so that the cathode inlet air is able to absorb more moisture in a water vapor transfer unit. The system can include a valve that selectively by-passes the heat exchanger if the cathode inlet air does not need to be cooled to meet the inlet humidity requirements. Alternately, the charge air cooler can be cooled by an ambient airflow.