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jaxie072
29-01-2006, 09:53 AM
I want to know your recomandations about air flow (at the evaporator) for freezing tunnels and frozen product store.
Also the necessary time for freezing the meat ( cow,pork, poultry). Is there any technical literatury for these rules?
Thanks for your help,
:)

jaxie

SteveDixey
29-01-2006, 10:24 AM
I want to know your recomandations about air flow (at the evaporator) for freezing tunnels and frozen product store.
Also the necessary time for freezing the meat ( cow,pork, poultry). Is there any technical literatury for these rules?
Thanks for your help,
:)

jaxie
If you talk to freezer manufacturers, they will have data that they have from their own testing. If you supply them with product temperature, thickness, and weight they will come up with feed rates and refrigeration loads for their freezer.

For example: Fish portions (100 gram) in a spiral freezer might be approx 1200 kg/hr. I would use 80 kcal/kg for a parfried portion based on an equilibrated infeed temperature of +25*C..You need to add a figure for the base load (41.000 kcal/hr for the base load in this example for fans etc).

For 25 gram fish fingers, they may have a slightly higher throughput and the enthalpy may also be higher depending on the equilibrated infeed temperature (they tend to warm up more in the fryer).

Air flow tends to be in the range of 5 to 10 metres/sec but higher fan power / speed generates more heat so reducing refrigeration capacity for the product, so you only use what you need.

For storage, it really depends on your coldstore layout, but you might be looking at 1 or 2 metres/sec air flow velocity.

If you do a Google for the FAO Document Repository, there are files there that cover some rule of thumb info.

Steve

US Iceman
29-01-2006, 03:23 PM
Freezing times for product depends on many factors. Size of the portion, entering temperature, belt loading and belt speed (for spiral or tunnel freezers), air temperature, etc.

The manufacturers will have a very good source of information since they have probably already experienced all of these on other projects.

In some circumstances the product leaving the initial freezer may have frozen the outer crust of the product, and the remaining freezing may occur in the storage.

One important aspect of freezing is the time required to freeze the product. Slow freezing times will allow the water in the product to freeze very slowly. The slow freezing process then allows the ice crystals to freeze in a larger size. With fast freezing, the ice crystals that are formed are much smaller.

The size of the frost crystal can determine if the product is readily accepted by the consumer, or if you end up with a mushy product that is not attractive.

The storage temperatures and the consistency of the storage temperatures can also affect the product shelf life.

If the product can be frozen and stored at proper temperatures, the water in the product can be frozen in a form called a glass. This form has very little product cell disruption and provides a much higher quality product.

The temperature where this occurs is called the glass transition temperature. This varies for all food products and depends on the starch, sugar, and protein content. This is where the food manufacturer should have some food science people to help determine the proper freezing temperatures.

One book you may want to find is...

Heat Transfer in Food Cooling Applications
Author: ibrahim Dincer
Publisher: Taylor and Francis
ISBN: 1-56032-580-1

mohamed khamis
06-03-2006, 10:24 AM
i need software to design ice cream freezer

Andy
06-03-2006, 08:49 PM
i need software to design ice cream freezer
You can have all the software in the world, but you still need to learn the principles to design properly. You need a designer or the time to learn the process yourself, probably a year or two working with someone knowledgeable would help.

Kind Regards. Andy:)

US Iceman
07-03-2006, 04:59 AM
I have to agree with Andy. No one should use software until they understand what the software is trying to calculate.

I would suggest you find some books on food science for freezing. These books usually have some topics related to ice cream.

A storage room can be different from a hardening room for example. It is also necessary to maintain the temperature stability of the room. If the room temperature fluctuates too much you can ruin the ice cream texture.

mohamed khamis
08-03-2006, 02:51 AM
Hi Andy
Thank u so much for great advice, you are right, but I know how to design freezer coils but all I need just a reference to check the feasibility of my design. Once again, I appreciate your advice

best regards
:)