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Double pipe heat exchanger with SST k-w turbulence model |
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July 15, 2015, 12:33 |
Double pipe heat exchanger with SST k-w turbulence model
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#1 |
New Member
Join Date: Apr 2015
Posts: 11
Rep Power: 11 |
I've made quite a few threads lately, but it seems I just can't understand what I'm doing wrong... And I'm seriously running out of time
Here is my problem: A counterflow double pipe heat exchanger was chosen for it's simplicity. Through the inner pipe flows a gas starting at 600°C (873K) going to about 50°C (323K), this is a laminar flow according to previous calculations.. Water flow through the annulus starting at a temperature of 6°C (279K), again according to previous calculations this is a turbulent flow with a Reynolds number of approx. 80 000. The diameter of the water inlet and outlet is 19.05 mm From LMTD, etc equations the pipe needs to be 3.5 m long
-the inlets are set to velocity inlets and I've calculated the velocity by means of 'flow through a certain area'. the turbulence factors I've decided to used (because they where easiest to find/know) are turbulent intensity (from the ansys guide I=0.16(Dh)^(-1/8))and hydraulic diameter (for both of which I've simply used the inlet diameter of the fluid 19.05 mm)
What I get from this seems to be a very efficient heat exchanger when looking at the contours of static temperature...The does also seem to be an instability in the x-direction when looking at the scaled residuals... http://s12.photobucket.com/user/MStu...tml?sort=3&o=3 http://s12.photobucket.com/user/MStu...tml?sort=3&o=5 http://s12.photobucket.com/user/MStu...tml?sort=3&o=6 http://s12.photobucket.com/user/MStu...tml?sort=3&o=7 Please help me out with this problem, I can't seem to understand this problem or what I'm doing wrong, my degree hangs in the balance and I'm seriously running out of time... Also, I'm sorry to make this so pic heavy, but as they say 'a picture tells a thousand words'. Thanks for any help you can give me, MStudent |
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May 21, 2016, 03:31 |
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#2 |
Senior Member
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The main issue may be in the flow direction which is specified in the cell zone condition. Here in your image. it is in z direction while the other figures suggest that they should be in x direction. Please put x=1 and z=0
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