Browse Prior Art Database

Design of Flow Stand To Measure Fuel Cell Coolant Conductivity

IP.com Disclosure Number: IPCOM000028943D
Publication Date: 2004-Jun-08
Document File: 5 page(s) / 137K

Publishing Venue

The IP.com Prior Art Database

Abstract

Fuel Cell Vehicle Cooling System requires coolant of very Low Electrical Conductivity. The unique coolant should not have corrosion inhibitors, which are ionic, and therefore the coolant electrical conductivity will increase from the leaching of ions of cooling system components. It is unknown about how much ions leach out of components used in a Fuel Cell Vehicle cooling system. This information is necessary to design the Fuel Cell Vehicle Cooling System.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 38% of the total text.

Design Of Flow Stand To Measure Fuel Cell Coolant Conductivity

                       

Fuel Cell Vehicle Cooling System requires coolant of very Low Electrical Conductivity. The unique coolant should not have corrosion inhibitors, which are ionic, and therefore the coolant electrical conductivity will increase from the leaching of ions of cooling system components.  It is unknown about how much ions leach out of components used in a Fuel Cell Vehicle cooling system. This information is necessary to design the Fuel Cell Vehicle Cooling System.

A unique Flow Stand outside of the vehicle had to be designed which could allow balanced flow of coolant through the cooling system components at controlled conditions in order to find the electrical conductivity of the unique coolant flowing through the cooling system components.

Description

Traditional internal combustion engine coolant formulations primarily consist of water and ethylene glycol.  Although water and ethylene glycol themselves do not conduct very well, these formulations will not meet the low conductivity requirement because additives, such as corrosion inhibitors, pH adjustors, and dyes, are ionic in nature, thereby increasing the conductivity of the coolant. Therefore, the coolant selected for the Fuel Cell Vehicle is a mixture of deionized water and ethylene glycol with no additives.  However, this only ensures initially low coolant conductivity. Ethylene glycol decomposes in the presence of oxygen to form acidic by-products, such as glycolic, glyoxylic, and formic acids. The presence of these by-products not only increases the conductivity, but also can significantly accelerate corrosion processes in the coolant loop due to the lack of corrosion inhibitors and pH buffers. Further, the rate of ethylene glycol decomposition increases with increasing temperature. 

In addition, plastic, aluminum, and rubber components used in the cooling system add ions (organic and inorganic) into the coolant through leaching, degradation and/or corrosion processes, increasing conductivity. 

The unique coolant in the Fuel Cell Vehicle (FCV) is a mixture of deionized water/ethylene glycol. For functioning of the Fuel cell, it is required that the coolant that flows through it should maintain very low electrical conductivity (<5 mS/cm) to avoid current leakage and short circuiting, presenting a unique water chemistry issue.  The coolant's initially low conductivity increases as: 1) ions are released from system materials through leaching, degradation and/or corrosion, and 2) organic acids are produced by ethylene glycol degradation.  Estimating the electrical conductivity of the coolant as it flows through the components of the cooling system is very important for design and operation of fuel cell vehicles. The unique Flow Stand apparatus was designed and built to replicate the vehicle like conditions of the coolant and study the effect of the coolant flow through various cooling system com...