[mariconeagles96]

Im trying to investigate the thermal cooling inside the mold. The tube is about 8mm in diameter and the mold block is about 100x50x20mm. I dont have the proper heat to be use as my heat source but just got temperature reading from the mold. Temperature there about 250C. Mold is located above the cooling tubes. How do I set this up in cfx? My tube coolant uses oil with about 60C in inlet temperature and about 30LPM flow rate.

Shall I go to the wall of my mold part and set this at Fixed temp = 250C? The problem seems to be like a cold plate but my heat source is constant temperature.

Thanks for the help guys! =)

[ghorrocks]

What are you actually trying to achieve with this simulation? Do you want to know how much heat the coolant removes? Or what temperature the mould is at some time? These are all different simulations.

[mariconeagles96]

thanks ghorrocks! the objective of my simulation is to check the thermal gradient on the mould because we are planning to change the design of our cooling tubes. It can be steady state or at a certain say 20sec...but steady state at first will be ok.

[ghorrocks]

What are you moulding? A molten metal? A plastic? What temeprature? Any chemical reactions or phase changes take place?

[mariconeagles96]

plastic...temperature at 250C. So I intend to make my temperature my source for I dont have any heat source in the moulded part. So by doing that, Im trying to check the gradient across my moulding block. No chemical reactions.

[ghorrocks]

There are many approaches for doing this depending on how accurate you want to be.

My first thought would be to model the plastic as a solid domain with an initial temperature of 250C and a specific heat and other properties such that it approximates the cooling plastic.

But things are a little different if you want to get the quasi-steady state temperature (ie the temperature after lots of cycles). But I am not sure if this is what you want.

[mariconeagles96]

Probably do the 1st one...so how to do it? Hw can i specify fixed temp on the surface of my moulded part? Coz i think in fluent, you can make your temp as a source. In cfx, shall i make use of the non-overlap regions automatically created by the software with walls there to be as fixed temp? Thanks!

[ghorrocks]

In that case there is no temperature boundary conditions to be specified at the plastic mould. You define an initial condition (250C for the plastic, initial mould temperature for the the mould) and it will do the temperature history from there.

There is an interface between the mould and the plastic, not a boundary condition.

[rglithro]

Hello Glenn
In one your posts you mention quasi-steady state temperature setup for the mold this is something I am currently trying to simulate (roughly the same setup as the initial post). My current setup has the following parts

Mold Tool - Aluminium
Plastic Part – Copper
Cooling Channels – Water

A steady state analysis (no heat source, 2 cooling channels with flow rates)
Transient Analysis (starting from steady state results) using the Plastic part as a heat source (total source) [kg m^2 s^-3] which is controlled by an on/off cell expression. E.g. on for one second (injection phase) off for 29sec (cooling phase)

Would you recommend a better way to do this for multiple cycles, or am I heading in the right direction?

The overall goal is to analysis different cooling channel profiles if that helps

[ghorrocks]

What are you trying to achieve with the simulation? Do you want to compare different cooling channel profiles at continuous operation? DOyou care about the thermal transient inside a cycle, or just the cycle averaged temperature?

[rglithro]

Do you want to compare different cooling channel profiles at continuous operation? Yes

I’m interested in the thermal transient inside a cycle, along with;

Coolant temperature variance between inlet and outlet on each cooling circuit

Plot the Avg. temperature at the mold/part interface during each cooling cycle cycle for continuous cycles of operation (until quasi stationary state is reached)

Plot the Min and Max Temperatures at the mold/part interface during each cooling cycle for continuous cycles of operation (until quasi stationary state is reached)

[ghorrocks]

You might be able to start close to the continuous condition by averging heat loads over the cycle and running a steady state run. Then to get the continuous cycle results use that as an initial condition for the transient cycle run, and run over a few cycles to let it establish a repeating pattern.