There have been recent studies that indicate that the effects of tiny soot particles are much more serious for global warming than previously thought. I decided to tackle this new problem with a solution that would be a quick and relatively inexpensive fix to ensure rapid adoption and correction of the environmental impacts.
I started with the initial concepts in parallel with my research. The intent was to slowly improve the feasibility of the concepts with increased knowledge of the field, but still have the first set unbiased by the existing trends in the field. This stage took about 3 months.
These refined concepts were created once the research and initial concepts were completed. They took the information learned from the research and cues from the "blue sky" initial concepts to create a series of practical yet innovative concepts.
Noticing some patterns in the refined concepts, I broke them down into the two required functional elements: collection and cleaning. External collection was selected because a low enough pressure drop in the filtration material was difficult to achieve. The internal collection method would likely cause chimney draft issues. For the cleaning method, it wasn't yet clear if cleaning was needed in normal burning scenarios. The prototype was built with no cleaning mechanism in order to evaluate this need.
In order to better understand current filter designs, I dissected an automotive cabin air filter. This is the documentation I completed.
These equations and calculations were used in combination with an equal friction chart (common in duct design) to determine the chimney velocity at various standard states.
Once it was determined that a fabric filter was the proper course of action, these calculation were performed to determine the exact type of material as well as its size and placement. This is a summary of a much larger excel document in which many more options were evaluated.
The filter was designed to have a pressure drop equivalent to an T-section in the chimney pipe, which in turn is equivalent to approximately three feet of pipe.
The prototype was built from type 304 stainless steel, high temperature RTV silicone sealant and standard fibreglass fabric.
Testing was performed using the ASTM standard test for wood burning fireplace emissions. The prototype was successful in developing a layer of carbon black, while still allowing sufficient draft in the chimney. Areas for improvement are currently being evaluated.