I just watched this video about a low-cost method of performing Schlieren imaging
. For those who haven't heard this term, it's a method used often in R&D to visualize flow-related phenomena that aren't visible to the naked eye. It's found commonly in combustion research as well, and my head went immediately to rocket mass heaters and how this low-cost technology could be applied to their improvement. I am thinking that it could be good as a baseline to do this kind of imaging on several poorly performing heaters/combustion units (obviously, Schlieren imaging would only be relevant to the
combustion portion of a RMH... no relevance I can think of to the other parts) and then compare the flow with that of a good heater. I'm sure that are myriad ways to apply this method of flow visualization given that the linked method is so cheap to get imaging going.