Heat transfer rate in a mold

[ralphv]

I am currently working on tuning a temperature controller that supplies 330degF. oil (Monsanto therminal 55) to half of a compression mold. The mold half is approximately 36” x 24” x 8” high. The 3/4” oil lines run in a zig zag pattern totaling about 13’. Currently the incoming oil is cycling 10deg. above and 8deg. below the setpoint with a frequency of 35 seconds. The flow is 3-4fps, and my total average temperature loss as about 14degF.

How much tighter (if any) should my incoming temperature swings be before it becomes negligible.

Thanks, Ralph.

 

[JKEngineer]

Ralph -
I don't think you have given us enough information about the system, nor defined what "negligible" means -- it depends on the sensitivity of your product/process.

There are a few approaches I would use to look at the problem:
1- model the system and examine what a step change in all the oil's temperature does to an otherwise steady state system. This is an approximation of what is going on, and would merely serve to give some guidance on the effect of passage spacing, for example.
2- Model the system in more detail in terms of actually using the input variation and monitoring the output variation as the time history of various locations on the mold's face. This would be more complicated and time consuming, but would be a more accurate representation of the system. Approximations could be made to simplify and reduce the model size that might be acceptable.
HTH. Feel free to contact me directly if you wish.
Jack

Jack M. Kleinfeld, P.E. Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

http://www.KleinfeldTechnical.com