Removal of Heat From a Hydrogen Storage Media by a Novel Microscale-Based Heat Exchanger

High volumetric storage density of hydrogen gas is a major challenge in the progress towards hydrogen-fueled automobiles.  Of the various storage methods, pressurized gas tanks, liquid hydrogen storage, liquid chemical systems, and solid-state storage, activated carbon adsorbents show great potential.  A reliable thermal management system within the storage tank is vital to provide quick, safe, and efficient charging and a controlled release of hydrogen gas on demand.

The current work investigates room temperature adsorption of nitrogen gas (model gas for hydrogen) in activated carbon bed and compares the temperature distribution within the storage media without thermal management, and with the addition of a microscale-based heat exchanger.   Experimentally obtained temperature distribution data is used to assess the effect of charging time, and removal of generated heat within the system. A mathematical model is used to numerically simulate the experimental process.

The maximum height of activated carbon bed positioned between two heat exchange devices, while providing adequate thermal management, is investigated by varying the height of the adsorption bed and monitoring nitrogen-charging time and temperature distribution.

A novel microscale-based heat exchanger design takes advantage of 250 μm high features, which facilitate the flow of cooling fluid. The heat exchanger is fabricated by diffusion bonding of patterned stainless steel shims, resulting in an overall 250 μm thick resistance to thermal transport. The heat exchanger design also provides uniform gas distribution into the bed of storage media.  The device’s ability to provide a uniform temperature at the contacting surface is verified using infrared thermal imaging. 

Experimental results indicate a dramatic improvement in charging time due to the fast and efficient removal of generated heat.