## General Mechanical

Topics relate to Mechanical Enterprise, Motion, Additive Print and more

#### mold temperature control

• Jackely
Subscriber

I'm trying to create a simple model of the mold temperature control.

as you can see in the picture are Cooling/heating channels.

i have watched this video until a point in time 1: 2 min

My question (to be sure that I am on the right way).

I should create three different bodies ( tool and 2 channels ) (if yes, how can I do that? )

Thank you

• Jackely
Subscriber

I have now constructed the new version in another ANSYS version.

I created 3 bodies and considered them as part bodies.

I imitate as in the video, but in my case it doesn't show Cell Zone Conditions.

• peteroznewman
Subscriber

Please show what is in your Workbench project schematic. Did you have a Fluent analysis system?  Is that where you created Geometry and then Mesh?

• Jackely
Subscriber

yes I have Fluent analysis system (see picture) and there I created geometry and mesh.

can I simplify this problem as a purely mechanical problem? I have already seen a post from you where you solved a thermodynamic problem in mechanical ANSYS.

• Rob
Ansys Employee

You've not got a mesh: do you have volumes or faces in geometry?

• Jackely
Subscriber

I created the volumes in geometry.

is this the right analysis system for my case? or should I analyze that in thermal-stationary system.

• Rob
Ansys Employee

What are you trying to find out? Please show the tree in Meshing (expand the Geometry section).

• Jackely
Subscriber

I need to calculate the variation of temperature in the mold.

• Rob
Ansys Employee

As it's filling, changing, being cooled? Is the coolant flow important or can you assume it's all solid?

• Jackely
Subscriber

the coolant flow is unimportant for me, I only have to see or simulate the temperature curve in the tool.

I have to enter the inlet temperature of water.

The idea is that the temperature control tool causes a cooling error. (see pictures)

Cooling error is the difference between qmax and qmin.

and this is what I wanted to do with this example

• Rob
Ansys Employee

Is the material that's being cooled liquid or solid at the point you're interested? Does it move?

• Jackely
Subscriber

and water flows into and out of these round canals (and is always considered liquid).

• peteroznewman
Subscriber

You could build a series of models to develop some skills with ANSYS and grow your understanding of this problem, which can become very complex.

Though the real problem is transient, start working with a steady state solution to see what that shows.

Start with a 2D model and ignore the temperature change of the cooling fluid as it travels through the depth of the tool. That means drawing a section of the tool on the XY plane as a surface.

For either 2D or 3D, you have to set boundary conditions on all surfaces of the tool, which in 2D are edges. A simple model could have the temperature on the side of the tool that the molten plastic is flowing past is set as a constant value, while the edges where the coolant is flowing could have the temperature of the coolant. That leaves the other 3 edges, which could have convection with the outside air temperature. Or you could make just one outside edge have convection to outside air while the two sides of the tool have symmetry. This represents a small section of a much longer tool.

Once you have success at a 2D steady state model, you can try more complicated models. The most complex model could have molten plastic advancing into the cavity and freezing onto the walls as it goes.

• Jackely
Subscriber

this is really a useful suggestion.

I also have the experimental results that have already been done by someone else, but so far I have no access to these results.

and I think it makes sense for me to concentrate totally on simulation.

I'll be back when there's anything new.

until soon

• Jackely
Subscriber

Hello all dear members of the Ansys Forum;

I have done the model in Steady State Thermal Analysis.

these were my steps:

1. I considered or simplified the model as 2D and as stationary.
2. considered as symmetry that the model and boundary conditions are symmetry.
3. split as 3 bodies and then created as a whole body.
4. I have the temperature and heat flux density as results

My goal now is that I determine thermal resistance in relation to distance a.

the thermal resistance is defined as follows:

all three factors are known, can i determine a relationship between thermal resistance and distance a? by Design of experoiement in Ansys?
Input : a
Output : R
but how can I define R in Ansys?

These are the temperature distribution and heat flux.

Thank you

• peteroznewman
Subscriber

I'm confused, why is the highest temperature in the cooling line?  I thought that the cooling line was supposed to be the coolest part of the tool, not the hottest.

• Jackely
Subscriber

oh I have mistyped the boundary conditions.
now all looks normal again

• peteroznewman
Subscriber

In the image at the top, the cooling pipes are defined with a dimension B and C.

Please show an image that illustrates the input distance a.

The equation you show is typically used in a 1D analysis. The variable A in that equation is the cross-sectional area of the 1D analysis. q_dot is heat flux so q_dot*A = heat flow along the 1D direction.  How do you want to apply that in 2D?

• Jackely
Subscriber

the cooling pipes are defined only with the dimensions B.
The dimensions C define the symmetry.

I think in 2D, the heat flow will look like this:  q_dot*A*a

• peteroznewman
Subscriber

Does the image below show what you are calling a?  Isn't that kind of covered by C?

If you add some blend radii in the corners of your cooling lines, you can avoid huge heat flux values in the corner.

The units are not correct when you multiply q_dot*A*a

• Jackely
Subscriber

yes is with me a the distance.

The goal is not geometry optimization, but a comparison between round and square channels.

about round channels are already a lot of research done, but square channels not so many.

Therefore I would like to compare a relation between distance a and thermal resistance to compare it later with round channels.

I'm going to read some books on heat flux to understand that.

• peteroznewman
Subscriber

axx?  What happened to a?

• Jackely
Subscriber

Oh, sorry, I just mistyped.

I got confused.

I corrected it.

• peteroznewman
Subscriber

If the diameter of a round channel is d, the surface area is Ar = 3.1416*d per unit depth of tool.

If the side length of a square channel is h, the surface area is As = 4*h per unit depth of tool.

Are you going to compare the heat transfer by making d = h or are you going to adjust h so that Ar = As?

• Jackely
Subscriber

No I will not use the geometric equivalent diameter, but hydraulic diameter ( to make a fair comparison between round and square shape)

but in this case hydraulic diameter for both gemetries is the same, because the dimensions of rectangular channel are 10*10 mm.

https://www.engineeringtoolbox.com/hydraulic-equivalent-diameter-d_458.html

• peteroznewman
Subscriber

The hydraulic diameter of a pipe of diameter d is d.

Equal hydraulic diameter means you are going to make the side of the square equal to the diameter of the circle.

Without any simulation, just based on the larger surface area, the square is going to have a higher heat flow, and result in a lower temperature than the round cooling channel.

• Jackely
Subscriber

that's right

I'll do it without simulation.

Thank you

• peteroznewman
Subscriber

Okay, please mark one of my posts above with Is Solution so the Discussion can be marked as Solved.