Blast Freezer-Conservation Freezer Same Room

[georgedvf]

Hello everybody!!
There's a project I'm working on and I have the requirement to use the same area (room) as Blast Freezer and as Conservation Freezer. Let me explain, it is a room where you can fit 40Tons of shrimp, every day they will load the half of it hot, about 4ºC, and they want to freeze it to -18ºC right there in the room, while the other half is already at the conservation temperature (-18ºC) just beside.

The question is, is it possible without affecting the already freeze product??? Have you ever do or seen this?

Thanks in advance!

[AUScooler:-)]

How about internal paneling?

[georgedvf]

Thanks AUScooler:-), could you explain me more??? I really don't understand what you mean with internal paneling.

[Romanicus]

Hi, I had requirements like this and I tried to convince my client not to do that. I propose them the following: Make 2 freezing tunnels and when the product is frozen the freezing tunnel will switch automatically into frozen storage. I am not controlling the air temperature inside the room. I put a temperature probe into the product. When it will hit -20C the freezing process is stopped. The plant will start again when the product temperature rises at -18C. It's good for example if they load the tunnel at the end of the day and the freezing process ends in the middle of the night.

[georgedvf]

Thanks Romanicus, I see you convince your client not to do that, but how do you convince them???
What are the problems or disadvantages if doing it as I described it in the first post???

[mad fridgie]

This is a common requirement especially for those small clients who do not have the big budgets, for seperate systems.
So the first queston is how much man handling of the of the product deos the client want do! (if he is happy to move product with in a single room, then you can install a simple curtain to seperate, frozen from fresh product, with each zone effectivily having its own airflow (which could be controlled). you need to ensure that the refrigeration capacity and evap selection is large enough to ensure that under high load that your air off temp never climbs above your stored product temperature.
Second how quick does he want the product frozen, if he wants it quick then as above, if he will except a longer time, then a reduce flow off air through the fresh product, reducing the amount of energy that can effect the existing frozen product. (no specific loading pattern required)
What you do not want is massive temp swings in the already frozen product (i am not talking about defrosting and re-freezing) Continiual swings from say -20C to -40C (all swings), will dry the product out "freezer burn"

[Romanicus]

I am not convincing them too often :(, but i explain them the following:
The main problem during operation in a freezer like this is that you can't make FIFO. You have to make a lot of handling of the goods. Ussualy the last product frozen is the first product taken out of the room. If they will not deliver all the 40 T, you can consider the tunnel as a frozen tunnel for 20 tons and a "ballast" of another 20 tons of frozen shrimp.
The second one is the energy efficiency. Why to go with -40 evap for the already frozen product when you can increase it to -30 for storing.
The third one is that is always better to have two tunnels instead of one.
Of course it all depends of the budget.
Other thing you can propose is to make them an acoustic and visual alarm when the freezing process is ended (a siren and a light bulb). They will move the goods into a frozen storage, meanwhile you are defrosting the evaporator, and they will load the goods for another freezing proces). I guess the shrimp has a lot of water in/ on it. Oh, and as refrigeration equipment i prefer to use screw compressors and electronic expansion valves.

[georgedvf]

And what do you think about having a "Pre-cooling" type system, making the Plenum box and forcing the air through the product using canvas to form a tunel, usign a separated refrigeration system to use it when freezing is required and the normal refrigeration system to use it when freezing is done??? This would be in the same room.

[Romanicus]

I'm sorry, can you make a small drawing?

[georgedvf]

I imagine something like this:

6551

Hope it helps!

[Romanicus]

From my point of view looks very interesting. I think that you can try to make a middle wall just to be sure you allow a proper air flow over the product. Must be checked if the external pressure of the fans is enough for such a long tunnel.

[georgedvf]

Thanks for your comments Romanicus.
About the external pressure of the fan, I'm pretty sure it must be a centrifugal one, I've seen this long tunnels using centrifugal fan.
About the middle wall, I guess it's true that you get better air flow but I've also seen rooms without middle wall working fine, just those I've seen are cooling at 0ºC not freezing at -20ºC.

[Romanicus]

My supplier of air coolers said that he doesn't reccomend centrifugal fans for freezing, because water can freeze over the fan and lose balance. I wanted to make a "cold air preparing room" like you did for an existing quick chilling room for hogs (-25 C inside) and then to go with air duct over the pigs (the line was too high and i couldn't insert the evaporators).
I am wishing you good luck with the project.
All the best.

[smpsmp45]

www.randallmfg.com.

Try this product.

[georgedvf]

I'm sorry smpsmp45, I don't understand wich product you mean...

[smpsmp45]

This can be used to make the partitions at will!!!

[Tradewinds]

I used to work on the prawn trawlers (schrimp boats) in the north of Aus and they would have a snap (plate type heat exchanger) freezer at -45'C and a seperate storage area at -25'C.

We would first put the prawns into the snap freezer until they were frozen and then move them into the storage area.