I'm looking to enrobe 1/2oz gem donuts at a rate of about 25,000 to 60,000 per hour. I've been told to get a 60-80ft cooling tunnel. Can I get away with a shorter tunnel?

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2 answers


Part of the answer depends on what you are enrobing with, but the simple answer is - probably not. 

You have to get the coating to cool from the temperature it is applied at to the desired temperature at the end of the tunnel. At 1000 pieces/minute the donuts are flying off the coating line. To cool them down requires a balance of time and temperature. You can't get the tunnel too cold or the coating won't set properly.

It's all about the physics of heat transfer. If you try to go with a shorter tunnel you will likely be very unhappy. The company that makes the coating you are working with probably has a technical department that can help you answer this question - not all coatings have the same heat transfer characteristics, and the thickness of the coating will also affect the length of time required for cooling.
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You are most likely coating the donuts with compound coating. We have done many installations where we have used a cooling tunnel with bottom chilled plates inside as well. You must have a residence time of approximately 4 minutes inside the tunnel to insure that the product's coating is properly set. It is a simple mathmatic calculation to determine the length of the tunnel you require. 
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