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heat generation using Piezo elements

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Buk:
Warning: I barely know what I am asking; and nothing about what I am trying to do!

I want to generate heat -- 200°C -- into a 1mmOD x 0.5mmID brass tube in <1 second.

My starting point is this paper http://gianchandani.engin.umich.edu/wp-content/uploads/sites/360/2018/01/BiomedMicroDev_2011_Cauterization.pdf that uses
4 off 300Ø x 135 µm PZT-5 elements to cauterize injection tracts from a 20 gauge hyperdermic needle.

My application is non-medical.

I *think* that a stack of thin piezoceramic rings surrounding the microbore brass tube, excited using a (guessimate) 100V p-p sinewave whilst being constrained axially, will generate heat internally, and by conduction, into the brass tube they surround.

Does anyone here have experience of using piezo ceramics in this way?

The 'electronics' part of this is that I wish to drive this heating using a single (or serial dual) Li-ion battery and a boost converter.

But first, I need to understand the piezo heat generation part of the equation.

Any suggestions, links, "you're talking outta you're ass", seriously considered.

Thanks, Buk.

T3sl4co1l:
To what end?  Does it have to be a tube -- what goes inside it?  Can it be filled with things, or does it have to be open?  Evidently at least some PZT micro-pucks would be permissible, but what about say a wire heating coil?  And what's being heated, will volatiles boil off?  Phase changes require far more energy than heat capacity alone; this is critical to the power requirement.

It looks to me like they're depending on the mechanical lossiness of tissue to do the job -- it's not just squishy but smooshy as well, and therefore absorbs mechanical energy.  Evidently, as it "cooks", the losses go up, evidenced by the lower impedance.  If you're just heating metal, you may find the losses aren't there, and it will take much more vibration than expected to deliver the heat.

Cool find by the way, that paper!

Tim

evb149:
Admittedly I haven't read the paper yet (it sounds interesting but busy at the moment).

But it is odd that one would use PZT for heat generation unless the circumstances somehow demand it.
Resistors generate heat 100% efficiently and they're usually cheaper and less "exotic" than piezoceramics.
Also it is harder to break resistors and easier to mechanically engineer them / procure them to different shapes, sizes, values
than piezos which are almost always exotic and hard to come by at low cost / procurement difficulty.

For that size of a tube something a little smaller than an 0402 imperial size SMD resistor could fit inside
so 0201s, etc.  Or you could use resistive wire such as nichrome of a suitable wire gauge.  Or since concentric is an option
then wind some turns around the outside of the tube with a bit of electrical insulation enamel to avoid conducting electricity through the tube
unless you are going to use that metal as your heater also / instead.

Or most simply you could use a section of the tube itself as the heating element by passing a suitably large current through it
at a suitably low voltage.

Also inductive heating could in theory heat the tube itself efficiently given the right external mechanics / electronics.

Less than 1 second time is meaningless for heating since the question is how much power is needed to be deposited in what volume of material
with what sort of heat capacity to raise its temperature NNN degrees / second / cubic millimeter or such like.

Unless you merely want the heater itself to rise in temperature in that time isolated to some degree from the tube etc. which would modify the power requirements
accordingly to the amount/type of material being heated.

For an example look at various sizes of electric light bulb filaments for which types of tungsten wire might be around that diameter and look at data relating to how fast they
heat up in their bulbs with a moderate amount of thermal conductivity through the gas and through the connecting wires.  It should be relatively common to see temperature rises of hundreds or
thousands of K / second given ordinary experience with incandescent lighting powered by 1W...200W range supplies.


--- Quote from: Buk on September 25, 2021, 09:53:39 pm ---Warning: I barely know what I am asking; and nothing about what I am trying to do!

I want to generate heat -- 200°C -- into a 1mmOD x 0.5mmID brass tube in <1 second.

My starting point is this paper http://gianchandani.engin.umich.edu/wp-content/uploads/sites/360/2018/01/BiomedMicroDev_2011_Cauterization.pdf that uses
4 off 300Ø x 135 µm PZT-5 elements to cauterize injection tracts from a 20 gauge hyperdermic needle.

My application is non-medical.

I *think* that a stack of thin piezoceramic rings surrounding the microbore brass tube, excited using a (guessimate) 100V p-p sinewave whilst being constrained axially, will generate heat internally, and by conduction, into the brass tube they surround.

Does anyone here have experience of using piezo ceramics in this way?

The 'electronics' part of this is that I wish to drive this heating using a single (or serial dual) Li-ion battery and a boost converter.

But first, I need to understand the piezo heat generation part of the equation.

Any suggestions, links, "you're talking outta you're ass", seriously considered.

Thanks, Buk.

--- End quote ---

Doctorandus_P:
Welding plastics with ultrasonic vibrations is a common process and these also work with Piezo elements.

I do not know how much overlap there is with your application, but searching in that direction may lead to useful results.

These generate heat by introducing physical motion and friction in the plastic. Heat is also just motion of atoms.
The design of these things is not trivial though. There is a simple looking metal part to convey the movement of the piezo element to the plastic but this is a sort of mechanical lens that focuses and thus amplifies the vibrations. Itss also a tuned mass system. At such high frequencies and small movements the metal is not a solid material, but it's more like a river though which the ultrasonic vibrations flow.

Buk:

--- Quote from: T3sl4co1l on September 25, 2021, 10:13:38 pm ---To what end? 

--- End quote ---

To see if it can be done and explore the pros and cons of doing it.

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