Fuel Cell Cooling Medium Flow Control for Warm-Up
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Solution Overview
Problem
In fuel cell systems, uneven temperature distribution across and within cell stacks occurs due to inefficient waste heat management, leading to prolonged warm-up times, especially when starting below the ice point, as waste heat cannot be effectively directed to slower-warming unit cells, causing re-freezing and reduced calorific value.
Innovation Solution
A method to control the flow rate of the cooling medium by adjusting it based on the inlet temperature, increasing the flow rate when above a lower-limit temperature to promote heat conduction and prevent re-freezing, and decreasing it when below the limit to prevent cooling of heat generation sites, thereby reducing warm-up time and maintaining calorific value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cooling water pump is stopped to prevent cooling during cold start, then the risk of re-freezing is reduced, but the warm-up time becomes excessively long
Solution Approach 1:
The patent applies dynamics by making the cooling water pump operation variable rather than static. The pump operates at different flow rates based on temperature conditions: stopped when temperature is below freezing point to prevent re-freezing, and activated at high flow rates when temperature exceeds the freezing point to accelerate warm-up. This dynamic control strategy resolves the contradiction between preventing re-freezing and reducing warm-up time.
2Temperature
If the cooling water pump operates at normal flow rate during cold start, then heat is removed from the cell stack, but the temperature distribution becomes uneven and warm-up is delayed
Solution Approach 1:
The patent applies parameter changes by modifying the flow rate parameter of the cooling water pump based on temperature conditions. During cold start when temperature is below the freezing point, the pump is stopped (flow rate = 0). When temperature exceeds the freezing point, the pump operates at a flow rate higher than normal to maximize heat distribution and accelerate warm-up while maintaining temperature uniformity across the cell stack.
3Reliability
If the cooling water pump is stopped during cold start, then re-freezing is prevented, but waste heat cannot be distributed to slower-warming unit cells
Solution Approach 1:
The patent applies feedback control by continuously monitoring the temperature of the cooling water and adjusting the pump operation accordingly. When the temperature exceeds the freezing point, the system feedbacks to activate the pump at high flow rate, enabling waste heat from warmer unit cells to be distributed to slower-warming unit cells, thus improving temperature distribution while maintaining reliability by preventing re-freezing.
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 approach effectively suppresses temperature distribution and re-freezing within the fuel cell, shortening the warm-up time and maintaining the calorific value by dynamically adjusting the cooling medium flow rate based on inlet temperature, ensuring efficient heat transfer and operation.
Implementation Method 1
the conduction of heat within the fuel cell is promoted
Implementation Method 2
the cooling water is not circulated... the power generation site is heated up rapidly
Data Source
AI summary
The method comprises: determining whether or not an inlet temperature is equal to or above a lower-limit temperature of a temperature range in which generated water does not freeze within the fuel cell; and adjusting the flow rate of the cooling medium in the circulation flow path to become more than the normal flow rate when it is determined that the inlet temperature is equal to or above the lower-limit temperature, and adjusting the flow rate of the cooling medium in the circulation flow path to be equal to or below the normal flow rate when it is determined that the inlet temperature is not equal to or above the lower-limit temperature.