Design of Diffusiometer for Aerogel Monoliths

Design of Diffusiometer for Aerogel Monoliths

Mechanical Engineering

Sylvia, Kamin

Bruno, Bradford

6/1/2018

Aerogels' have great potential to be used as catalytic substrates and filters. To use them as such, we must first understand how gas flows through them. Diffusivity is a property of aerogels that relates the gas flow through a sample with the pressure gradient driving the flow. This project sets out to design an experimental apparatus (diffusiometer) and methodology that can be used to obtain diffusivity values of various kinds of aerogels. Adapting the method outlined in Stumpf et. al 1992[1], a diffusiometer was designed and built for aerogels at sub-atmospheric pressures. This device utilizes a control mass system rather than the control volume system approach which can be affected by small flow rates and significant gas leaks. The diffusiometer utilizes two volumes, each monitored via one Baratron® Type 122A absolute pressure transducer. By allowing a known amount of gas to diffuse into an aerogel monolith, we can obtain a pressure curve which can then be used to solve for the diffusivity. System analysis includes the consistency of the vacuum pump and gas regulator as well as the response time of the pressure transducers. Over a one-minute interval, the vacuum pressure fluctuated over a range of 50 Pa while the gas regulator charging the system fluctuated over a range of 300 Pa. The pressure transducer's time response was found to be 0.857 second. One test was performed on a silica aerogel monolith, confirming the effectiveness of the gas baffle implemented to protect the fragile samples during testing.

thesis

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