Heat Transfer problem

Spartscle28 · July 14, 2020, 07:24

Hello, I am more or less new user of Star CCM+. Curently I'm studing the efficiemcy of cooling during drilling using inner cooling channel. So I'm simulating the heat transfer from drill to fluid. My model is steady and I'm using segrageted solid energy.
I created a small area close to the cutting edge, representing one boundary where the heat flux is put. Because the heat flux is not constant along the cutting edge I'm using a Data mapper to create a field function that I can use as a heat flux.
Unfortunaly the heat flux is not creating properly. I don't think the problem is data mapper beacause even if I put the heat flux as a constant value instead of the field function, the problem remain. I doesn't look like there is not heat transfer, but the difference of temeprature is only 1°C. I think there is a problem in setting of interfaces. Beacause the heat flux boundary on drill is also representaing an interface with the drill. But I have 0 contact resistane between drill and fluid. And when the heat flux is set outside the interface (on other part of drill - just to try - it's not possible when I want that it would be close to reality). I'm using an in-place interface. I was also thinking about Energy source option in interface, but I'm not sure if it would give the correct result.

If anybody has an idea where may be the problem. Or if there is any special setting necessary on boundary conditions or on interfaces.

Thank you in advance.

ping · July 31, 2020, 03:59

if you set your initial temperature conditions to say 20C in the regions and inlet fluid then applying the heat should show significant rise in both the metal and liquid and in the drill there should be a gradient up the drill length to the drill chuck contact areas where you might have a constant temperature wall boundary. if there is heating of the drill but not in the fluid then you have an interface problem.
one problem could be your solid energy under relaxation factor in the solver since this is too low by default and needs to be set close to 1 eg 0.99999. then create a report, monitor and plot at a point inside the drill metal a say 10% up its length and ensure this becomes level since solid solutions do take many iterations sometimes.
i hope you are applying the heat to a surface eg the bottom face of the drill bit with some actual area and not an edge which will have no area.

July 14, 2020, 07:24	Heat Transfer problem	#1
Spartscle28 New Member Hana Havlikova Join Date: Jan 2020 Posts: 3 Rep Power: 6	Hello, I am more or less new user of Star CCM+. Curently I'm studing the efficiemcy of cooling during drilling using inner cooling channel. So I'm simulating the heat transfer from drill to fluid. My model is steady and I'm using segrageted solid energy. I created a small area close to the cutting edge, representing one boundary where the heat flux is put. Because the heat flux is not constant along the cutting edge I'm using a Data mapper to create a field function that I can use as a heat flux. Unfortunaly the heat flux is not creating properly. I don't think the problem is data mapper beacause even if I put the heat flux as a constant value instead of the field function, the problem remain. I doesn't look like there is not heat transfer, but the difference of temeprature is only 1°C. I think there is a problem in setting of interfaces. Beacause the heat flux boundary on drill is also representaing an interface with the drill. But I have 0 contact resistane between drill and fluid. And when the heat flux is set outside the interface (on other part of drill - just to try - it's not possible when I want that it would be close to reality). I'm using an in-place interface. I was also thinking about Energy source option in interface, but I'm not sure if it would give the correct result. If anybody has an idea where may be the problem. Or if there is any special setting necessary on boundary conditions or on interfaces. Thank you in advance.

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July 31, 2020, 03:59		#2
ping Senior Member Ping Join Date: Mar 2009 Posts: 556 Rep Power: 20	if you set your initial temperature conditions to say 20C in the regions and inlet fluid then applying the heat should show significant rise in both the metal and liquid and in the drill there should be a gradient up the drill length to the drill chuck contact areas where you might have a constant temperature wall boundary. if there is heating of the drill but not in the fluid then you have an interface problem. one problem could be your solid energy under relaxation factor in the solver since this is too low by default and needs to be set close to 1 eg 0.99999. then create a report, monitor and plot at a point inside the drill metal a say 10% up its length and ensure this becomes level since solid solutions do take many iterations sometimes. i hope you are applying the heat to a surface eg the bottom face of the drill bit with some actual area and not an edge which will have no area.