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### Temperature Drop Calculation on Liquid

04/17/2012 3:02 PM

Dear all,

I´ve make a research about pulsed electric field for liquid sterilization based on simulations (Matlab). After calculation of the electrical field distribution and current density in each element of the mesh, I would like to estimate the final temperature (the temperature increased because the joule effect on the liquid conductivity=2microS/cm). I´ve applied pulses (from 20 to 600) with duration of 2μs and frequency 1Hz. I´ve calculated the increase of the temperature during time in which the electrical field is applied (2μs), but I don´t know how we could estimate the temperature drop when the electrical field is not applied (most of the pulse period). The liquid volume is about 18cm^3 in it is in a acrylical cylindrical chamber. Could someone help me?

Regards

Eduardo

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#1

### Re: Temperature Drop Calculation on Liquid

04/17/2012 3:18 PM

According to this(see link), the temperature rise is insignificant in what seems to be a similar process....

http://www.steribeam.com/technology/PEF-in-Brief.pdf

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#2

### Re: Temperature Drop Calculation on Liquid

04/17/2012 3:46 PM

Yes,

You'll need to know the composition of the liquid, its thermal conductivity and the TC of any other membres of the system and then calculate the amount of temperature drop caused by conduction, convection and radiation of the container and contents.

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#4

### Re: Temperature Drop Calculation on Liquid

04/18/2012 1:15 PM

As far as sterilization, I have experience with UTST pasteurization, where it is a temperature/time ratio.

Higher the temperature/shorter the time or lower the temperature/longer the temp.

There was talk of flash pasteurization, High temperature and very short time. The problem with this may also be applied with a problem to the OP

The process stated, how does one know that the heat was absolute and throughout the liquid.

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#3

### Re: Temperature Drop Calculation on Liquid

04/18/2012 12:10 AM

Presumably the liquid is being held in a plastic container, it's sealed so there are no convection losses, it's not very hot so there are low radiative losses, therefore all the heat lost it by conduction through the plastic.

Then you'd use the usual q = -kΔT.

The actual outside temp will sensitively depend on the air flow around the tank, there are various equations that purport to model this but I've never had much success with them when the temp diffs are low. If you want a better result you'll need to construct a model and measure the response.

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#5

### Re: Temperature Drop Calculation on Liquid

10/16/2012 12:42 PM

Continue calculation at the rest of time, using 0W power(set pulse=0.0) at that time.