Helium3 in low Temp -real gas

gardian · August 27, 2010, 05:50

Hello
I m running some simulations with He3 gas. it is a long tube (10 m) A=14.5 cm^2 filled with this gas. the temp of this tube is 2K BUT at the both ends of this tube I apply 70K . The tube is closed . when i run simulations with temp of the ends=20K and pressure inside =0.085 bar i had really good results. but now running the model with new boundary conditions (70K at the ends, 2K in the tube -15mbar ) the results are not so good. I m using the k-e turbulence model.
I used as heat transfer the Thermal energy and things get better. I noticed that at the ends the Reynolds number is very low. ~100. something is wrong.
It looks like there is very little gas at the ends and goes really fast ~100m/s.
any suggestion if I was clear enough? i tried also other turbulence models for low Reynolds number (sst etc ) but with no success.
thank you

ghorrocks · August 27, 2010, 07:38

What is driving the flow?

gardian · August 27, 2010, 07:59

In the 10m tube there is always a heat load of 2K while at the ends a thermal load of 70 K is applied. so I think the answer to your question if i m not wrong is the buoyancy and the convection.

ghorrocks · August 28, 2010, 07:50

This is so far out of my area of expertise that I have no idea what to expect from this flow. What is the Rayliegh number? Is the flow really turbulent?

Do you want steady state or transient results?

August 27, 2010, 05:50	Helium3 in low Temp -real gas	#1
gardian New Member anton.gardi Join Date: Aug 2010 Posts: 21 Rep Power: 16	Hello I m running some simulations with He3 gas. it is a long tube (10 m) A=14.5 cm^2 filled with this gas. the temp of this tube is 2K BUT at the both ends of this tube I apply 70K . The tube is closed . when i run simulations with temp of the ends=20K and pressure inside =0.085 bar i had really good results. but now running the model with new boundary conditions (70K at the ends, 2K in the tube -15mbar ) the results are not so good. I m using the k-e turbulence model. I used as heat transfer the Thermal energy and things get better. I noticed that at the ends the Reynolds number is very low. ~100. something is wrong. It looks like there is very little gas at the ends and goes really fast ~100m/s. any suggestion if I was clear enough? i tried also other turbulence models for low Reynolds number (sst etc ) but with no success. thank you

August 27, 2010, 07:59	He3	#3
gardian New Member anton.gardi Join Date: Aug 2010 Posts: 21 Rep Power: 16	In the 10m tube there is always a heat load of 2K while at the ends a thermal load of 70 K is applied. so I think the answer to your question if i m not wrong is the buoyancy and the convection.

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August 27, 2010, 07:38		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	What is driving the flow?

August 28, 2010, 07:50		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	This is so far out of my area of expertise that I have no idea what to expect from this flow. What is the Rayliegh number? Is the flow really turbulent? Do you want steady state or transient results?