Acrolab was asked by a client to analyze the performance of their cooling chamber for one of their pre-preg manufacturing machines and to provide recommendations on how to improve it.
Based on test results, the new cooling chamber was not operating in an optimized manner and Acrolab was contracted to solve the problem.
Optimizing Cooling Performance in New Pre-Preg Manufacturing Machine
After completing the build on a newly designed pre-preg manufacturing machine and completing performance tests on the machine systems, the initial test run of the machine produced a poor quality pre-preg. The client noticed that the cooling chamber, equipped with a cooling platen which is used to cool the fiber and the resin to a specific temperature (lower than ambient), was not achieving the desired temperatures.
Acrolab began the study by investigating the physical construction of the cooling chamber. We observed that because the cooling process during pre-preg production takes place when the pre-preg material moves between two solid metal plates, there could also be more variables which would affect the heat transfer rate between them, and therefore it was more difficult to determine the thermal resistances present in this interface.
Detailed Review & Analysis
After a detailed review of the design and operation of the machine and more specifically the function of the cooling chamber in the process, Acrolab was able to clearly identify the major contributing factors that led to the less than optimal performance of the cooling chamber. We then recommended several measures that could be taken to improve the performance of the cooling chamber.
During the process of our analysis, a few theories were developed and data was gathered to determine the thermal resistance between the two stationary, contacting surfaces.
- We determined that we needed to find a way to measure the heat transfer rate between the moving pre-preg material and the stationary cooling platens to determine the cooling performance of the cooling chamber.
- We also needed to achieve a balance between the coolant supply temperature and the heat transfer area inside the cooling chamber.
Acrolab Directed Research Required
Communications between Acrolab and the client helped identify potential problems with the existing cooling chamber and how these could be resolved. Analysis of previous data was reviewed in order to see if we could find any correlation between the data and the performance of the cooling chamber. Acrolab was required to conduct additional research and gather external data in the process of working towards a possible solution.
Of these variables the distance between these two surfaces was very important and had to be kept as close as possible, otherwise, the air layer between the two surfaces would create a large interface thermal resistance.
Acrolab identified early on that in order to get the quantitative heat transfer value between the platen and pre-preg that the variables affecting heat transfer between the platen surface and the pre-preg surface would have to be identified.
Acrolab Developed a Solution to the Cooling Problem
Acrolab developed a simplified methodology to calculate this interface thermal resistance between two sliding solid surfaces based on some fundamental assumptions. Based on this calculation, we were able to determine that the existing cooling chamber did not have a sufficient heat transfer area to cool the pre-preg to the required temperature, and the coolant supply temperature was not sufficiently low enough to maintain the temperature difference required to achieve the required heat transfer rate within the given heat transfer area.
A detailed report summarizing the findings and recommended modification measures to the machine build was proposed and sent to the client. This solution solved their cooling problem on the new pre-preg machine.