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Posted:
1 decade ago
11.09.2012, 13:36 GMT-4
Hi,
Apparently, COMSOL usually supposes that the fluids are compressible, of that type are the Navier-Stokes equations that COMSOL uses by default, even in the "conjugate heat transfer" physics. The complication seems to be the very high velocities, exactly high (> 0.3) Mach numbers, see "The Mach Number Limit" in the COMSOL's Multiph. User's Guide. For that case, COMSOL has the "High Mach number flow" physics, at least in CFD Module. I think you would have to manually couple that physics with heat transfer.
Bye,
Jesus.
Hi,
Apparently, COMSOL usually supposes that the fluids are compressible, of that type are the Navier-Stokes equations that COMSOL uses by default, even in the "conjugate heat transfer" physics. The complication seems to be the very high velocities, exactly high (> 0.3) Mach numbers, see "The Mach Number Limit" in the COMSOL's Multiph. User's Guide. For that case, COMSOL has the "High Mach number flow" physics, at least in CFD Module. I think you would have to manually couple that physics with heat transfer.
Bye,
Jesus.
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Posted:
1 decade ago
11.09.2012, 15:20 GMT-4
I had thought of modeling the flow seperatly and then feeding it into heat transfer model, (although I had never thought of the high mach number model, thank you) but my problem is that the change in temperature is the major driving force behind the flow speed. When hydrogen goes from 300k to 2000k, its density decreases by a factor of 6ish. This then should increase the velocity by a factor of 6 assuming constant mass flow. How could I model this speed up without heat transfer?
I had thought of modeling the flow seperatly and then feeding it into heat transfer model, (although I had never thought of the high mach number model, thank you) but my problem is that the change in temperature is the major driving force behind the flow speed. When hydrogen goes from 300k to 2000k, its density decreases by a factor of 6ish. This then should increase the velocity by a factor of 6 assuming constant mass flow. How could I model this speed up without heat transfer?
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Posted:
1 decade ago
11.09.2012, 20:19 GMT-4
So per your suggestion, I tried to model the heat exchanger in the high mach number module... but it didn't like it very much. I was returned more simultaneous errors than I have ever seen before. Now this could certainly could be my not setting it up right (the boundary conditions for the inlet had me especially confused), but I am thinking that it just doesn't like it because it goes from a velocity of Ma = .0587 at the inlet to something that should be around Ma = .7 at the end. In other words, it is subsonic the entire time. Does anyone see anything I did wrong in setting this up or can I assume the this scenario just doesn't work in the High Mach model?
So per your suggestion, I tried to model the heat exchanger in the high mach number module... but it didn't like it very much. I was returned more simultaneous errors than I have ever seen before. Now this could certainly could be my not setting it up right (the boundary conditions for the inlet had me especially confused), but I am thinking that it just doesn't like it because it goes from a velocity of Ma = .0587 at the inlet to something that should be around Ma = .7 at the end. In other words, it is subsonic the entire time. Does anyone see anything I did wrong in setting this up or can I assume the this scenario just doesn't work in the High Mach model?
