# Law of Cooling for calculating time

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### #1 Kaelthalass

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Posted 16 February 2023 - 12:42 PM

Hello everyone.

For corrective action and related purposes i have been tasked with deciding whether there was a risk or not in the product during transport.

We are carrying frozen chicken meat in refrigerated trucks

Intended procedure is;

-Initial internal temperature of the meat <-18 degree C

-Ambient temperature of the truck <-18 degree C

-Acceptable internal temperature of the meat <-15 degree C

-Transport duration varies.

So, would it be appropriate for us to use Newton's Law of cooling to decide the temperature of the product for a duration of X amount of time makes the internal temperature below -15 ?

Can i use any constant in this situation without carrying out a simulation representing the conditions, such as data from blast freezing of the product?

### #2 Scampi

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Posted 16 February 2023 - 01:12 PM

You should be able to calculate using newton's laws in this situation

Given that raw poultry turns into a solid mass (unless it's IQF), the likelyhood of any increase in the internal temp is slim under the conditions you've prescribed

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### #3 Kaelthalass

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Posted 16 February 2023 - 01:18 PM

The thing is i don't have the cooling constant, i have found some literature concerning heat capacity of the poultry meat but i don't know how to interpret it without adding into heat flux from the air and other heat transfer paths such as conduction via the packaging material.

It seems i have to carry out a simulation to decide the constant?

### #4 Scampi

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Posted 16 February 2023 - 01:53 PM

I think you may be overthinking this

Assuming your refer is set to -18C and your product is also -18, zero heat transfer will/could occur  hence zero risk

Now,  if you want to assume you've had a refer failure(and the trailer has a data logger) you could calculate just how long it would take your product to rise to -15C , but you'd also need to factor in the exterior conditions (temp, humidity, clouds or sun)

I used to import loads of fresh poultry from 3000 miles away.  It was shipped using layers of dry ice. It always arrived at 4C (as it should).  I really think you can make a risk analysis w/o the calculations

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### #5 Kaelthalass

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Posted 16 February 2023 - 03:18 PM

Thank you scampi.

The issue is actually deciding about whether opening a case of corrective action.

Thing is, everything mostly goes according to plan and most of the time the product doesn't even reach close to -15

But i keep receiving Corrective Action pleas such as;

The data logger shows temperature of the truck was -12 for 4 hours.

I want to actually roughly decide whether product is closer to the limit.

I keep thinking instead of placing an environmental data logger, may be a probe inserted into a product would make an alternative?

I tought about heat transfer from truck to outside, but if the ambient temperature is constant i tought i would neglect the capacity of the refrigeration is adequate or not.

Seems like i didn't make myself clear.