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View Full Version : Heat from packaging, need ideas







leewd
29-06-2012, 10:27 PM
Here's the situation. I work for an egg product company, making hard boiled eggs.
Background:
Cooked eggs cool down in a chilled bath, reaching internal temps of 37-38F
Prior to packaging, they are ran through an heated acetic acid (vinegar) bath.
Temps at packaging: Internal at 40F and surface temps of 90F
We package them using a vacuum packaging line, using heated sealing heads to melt the plastic together. I do not have temperatures of the plastic at the end of the line, I would guess 90F
They are sealed and sent down a 15' conveyor, through the wall and 5' into a 37F cooler

Problem we are having is after the temperatures equilize we are at 60F. Being boxed and then pallitized, it's taking a full week for the product in the center of the pallet to drop below 40F (where we want it). It's reducing our end products shelf life by a week.

I've suggested a chilled bath for after the acetic bath, however money is an issue. I'm wondering if there are any routes we go about on the cheap.

One idea was to try to install a fan and blast the packaging with the cooler air. The thought was the increased air movement with the air from the cooler would speed up heat exchange. Problem is they are only on this conveyor a whopping 6 seconds. Is this even worth considering ? How much quicker is heat transfer with turbulent air flow vs static air?

Thanks

r.bartlett
30-06-2012, 11:04 AM
6 seconds isn't long enough to remove enough excess heat/ I ran a small sandwich company and we baked the bread during the morning and the baguettes were then made . we would always bottle neck towards the end as the bread was not cool enough to handle. I bolted on several fans onto the side of the cooling racks and they would sit there till the next batch was made. It had a 5 minute air blast cool but it meant the end of the delays as they were plenty cool enough.

Of course we were operating at much higher temps but the air on was around 70 and the rolls were 300 so there was a big TD which helps heat rejection. Yours will be much closer and if you're only going to use untreated air that TD will be far closer and 6 seconds will make pretty much no ifference. .

It will work but I suggest the line is extended to give as much additional exposed time as possible c/w the use of downdraft fans along the route. (If it went in a chilled blast tunnel during that time even better.)

Why not set up a test rig and check the difference?

cadwaladr
01-07-2012, 03:32 AM
a spiral chiller may assist,how many eggs are we talking about and do you have room to put extra kit in the site you must be using a lot of energy the way you are operating at present so an investment to speed up the process must be viable.

shooter
04-09-2012, 10:44 AM
Your calcs look correct
40 in 90 out results in 60 to 70 average.
How long must the eggs be in the vinegar?
what minimum temp is still doing the job of conservation.
are the baskets moving in the vinegar as this will increase heatflow.
Is it possible to put a cooled bath behind the vinegar also filled with vinegar.
mind the internal of the egg, as the shell will come loose, try it with some eggs.

another one is right after boiling put the eggs in the vinegar which will cool down the eggs and preserve them, does not cost any energy
then a cooling bath is not possible anymore, but the eggs can be put in packaging trays in an aircooler.
when cooled down put them in the sealing machine.
are you really vacuming the packages or are you using nitrogas as medium. (do not use CO2)