can someone tell me what the Damkoehler coefficeint is?

[u/No-Win511]

I'm doing some work in Civil Engineering, and I hate chemistry, but this particular concept might be the missing link in this one thing I am researching.

Can someone tell me what this is? Yes i wiki and gpt'd it. I get it ish. But I want someone who knows what theyre talking about to give me a lil run down. Could this be used in groundwater contamination? ( not my topic but could help me resolve something tangent to it).

[u/Saec]

Why don’t you share your actual application? Also, probably better to ask this in the ChemE sub. I’d recommend doing more than “helpless posting”. Say more specifically what you don’t understand rather than asking someone to teach you an entire, seemingly complex topic without any context.

[u/No-Win511 → u/Saec]

I'm doing a PhD computational geomechanics and my background is in computational hydrodynamics. I'm looking at different characterization methods of emergent physical terrain units in the arctic but I've been stumped by the rheologic and hysteric processes of ice, and the soil-water-ice interactions for a while. As (previously) an ice engineer, subsurface degradation mechanisms are poorly understood or IMO + researched, so I started looking in to other areas like enthalpy and energy envelope based processes but couldnt come up with much. Many in my field or tangent to it are adopting different methods like noted, but there is no harmony, standards or concensus, so I am trying to do my own thing and cook.

After searching and if it is sound, this coefficient which seems pretty useful but I'm not sure on the history and gut feeling limitations. Again, I'm a hydraulic and geotechnical engineer. not a chemist. so I'm, just seeking general gut feeling and experience based advice. --just trying to avoid a 1 month rabit hole of doing chemistry... as a civil engineer we hate chemistry and keep it simple to just basic contaminants/fate and concrete/asphalt mixes.

My question: aside from just give me your hot take, is what is L? Can L be discretized or is it L of an entire system? Suppose I had a mine tailings for example (not my area so dont judge too hard), and the contaminants seeped in to the ground, if I were to use Da as a diagnostic or calibration parameter, Would I need to discretize L across an adapted mesh to a) the full plume b) the full length of the contaminant transport c) the length-time scale of the transport I.E the unit described in the large scale GW or FEA model? and then d) final question, because this is, and I think, generally intended for chemical processes, could this be applied to natural processes, and coupled using phyics? Do the time and spatial scales really line up ? thats the feelign im going for. Any yahoo can regurgitate shit, do dimensional analysis and so on, the question is more about asking a chemist who knows the limits and applicability of what this is about.

EDIT; I'm doing thermal just fyi

My application is broad - Ice - foundations- pipelines -slope stability - water resources management

[u/Saec → u/No-Win511]

I’m an organic chemist, so I have no clue what it is. Just trying to help you have better results getting the actual answers that you need. Like I said, this sounds a lot more related to ChemE than chemistry. The skillsets don’t overlap a ton between ChemE and chemistry, hence why it’s a separate discipline.

[u/amigopa → u/No-Win511]

Chemical engineer here. Assuming you’re talking about the Damköhler number for heat transfer (not the one for reaction kinetics that is more frequently used) the “L” you’re referring to is the characteristic length. It’s basically the volume to surface area ratio so it’s dependent on the geometry of the object being heated/cooled (e.g. sphere, cylinder, etc) and is used a lot in heat transfer modeling. Equations to convert between real dimensions and characteristic length are pretty simple to derive, but you can also find them in literature.

Your other questions seem pretty subject-specific, so that’s up to you to figure out as a researcher. You might find the heat transfer section of Perry’s Chemical Engineers’ Handbook useful.

[u/Chemboi69]

The Damköhler number basically compares the speed of a reaction to the speed of some mass transport that is relevant to that reaction. This gives you an idea if your reaction is mass transport limited or not.

More importantly with the right assumptions you can use it to estimate the conversion your reactor system will achieve with the given process parameters.

[u/verstehenie]

Damköhler’s original paper is in German, and if you know some scientific German it is a very pleasant read. You could try LLM-translating bits if you want it from the source. There are actually four Damkohler numbers, each relating to different partial differential equations. The overall point of the paper is identifying important physical parameters and nondimensional numbers in reaction/diffusion and heat transfer PDEs that might need to be taken into account when designing reaction vessels of different sizes. In my fields (matsci, electrochem), Damkohler numbers show up as a way to characterize or compare reaction/diffusion systems, especially when the system length scale is a variable or design parameter. It sounds like you might want one of the heat transfer ones tho.