We don't want to waste money too!

We wanted to see if we could replicate Celani first. But we could only get 350 Layer wire and he used 700 in Korea.

We have seen some interesting stuff.

But it is not categorical proof in our minds because of the open questions and large number of variables.

Transfer through conduction only will be the case for the stainless cell in US in Air Flow Calorimeter and for the Dual (active and control) cells made from Steel and glass in a fluid based calorimeter in the EU.

We want to run the two celani V2 protocols and controls largely identically, just differing locations and teams.

Perhaps - when the other cells start coming on line, we could take one or both of the current US cells and re-purpose them. Run calibrations on them with Celani V2 protocol but with copper or aluminium foil cover and then go active run. The big advantage with V2 protocol in this case is that the active wires and shielding will not have to be moved at all between calibration and active load / 'burn' cycles.

The stainless cell will certainly be IR opaque, but unfortunately the high thermal conductivity of the stainless will lower the temperature difference you observe for a given heat flux. ie. signal to noise will deteriorate. A better cylinder material choice would have been a poor thermal conductor. This would cause a larger temperature difference to be needed to drive a given heat flux through the wall. Larger temperature difference should result in a better signal to noise.

Unfortunately, you still need to take care on the positioning of the inside wall thermocouple in this case. You can still have localized IR thermalization effects skewing that reading. It would be better if the interior thermocouple was actually embedded in the stainless wall.

Immersing your apparatus in a controlled heat sink will help stabilize your readings. Immersing your apparatus in an air flow calorimeter will be uneccessary if you calibrate the heat conduction properly.

In addition stainless is succeptable to penetration by H2. Over extended time steel can actually become brittle from absorbed H2. Don't know what effect this may have on the thermal properties. Again a better material choice would be one that doesn't allow H2/D2 penetration.

bob

All good points.

We may start a calorimeter mini project to gather everyones thoughts in the same document.

It looks like we may well run a foil covered cell with a V2 after the extended run of the currently LIVE US cells.

Right now - those cells are creating a lot of data and are pretty maintenance free - so maybe good to just leave them at the minute.

If they were to top out and then drift back down to closer to zero, some of the challenges to it recently would themselves be in question. So we need to leave it to run.

B

Actually Mr. Google reveals that what I've been on about is actually called

Heat Conduction Calorimetry

More Googling reveals that there are commercial heat conduction transducers available:

www.rdfcorp.com/products/hflux/hfs-a_02.shtml

Perhaps a simple combination of foil radiation shielding and one of these heat conduction transducers might worth trying.

bob

Hi bob,

This looks like a very good find sir!

As I said before, at the end of the current lengthy series of shutdown experiments on the US cells, we plan to do the foil wrap run and this, as you point out - may be a nice addition.

It might also be worth adding to the standard temperature assessment on the V2 protocol.

Let's investigate the potential, can you do some digging around and find out what temperatures these kind of products are rated to? Also a selection of suppliers in EU and US?

B

I did a quick look at the commercial thin film sensors. Most appear to be a little marginal on the temperature spec:

www.captecentreprise.com/prod01.htm

200C

=====

www.rdfcorp.com/products/hflux/hfs-a_01.shtml

260C

=====

en.thermoflux.ch/tfx-technology/sensors/...rer=AZOSENSERSDOTCOM

230C

=====

www.thermalinstrumentcompany.com/product...ardthermalfluxmeters

600F

=====

I'm guessing you guys could build up a very usable version of the same by wrapping your glass tube in 3 layers: foil, suitable dense (silicone?) cloth/film, foil. if you place thermocouples at both foil cloth boundaries you may have a calibratable conductive thin sensor that reflects back IR.

bob

Given that we don't want the glass to go over 300 degrees that is ok.

Now I tried to find a contact to acquire some - but could not - the page goes blank.

Can you investigate where to buy them?

Bob

I have contacted RDF and hopefully we get a response (left both phone message and online form)

Bob

I don't have any special knowledge or access to these suppliers. I'm getting all my info from a series of Google searches.

Earlier in this thread you indicated that your apparatus ran hotter when you wrapped it in foil; presumably because the foil blocked and reflected back the IR.

If you examine the links for these thin film heat flux sensors they are nothing but a thin insulating layer with thermocouples on each side. The heat flux is proportional to the difference in temperature across the insulating film (straight heat conduction physics). The temperature limits are imposed by the material properties of this thin layer.

While you are waiting for info from the commercial vendors why not just queue up the following "quick and dirty" proof of concept:

a) wrap the glass tube in foil.
b) attach one set of thermocouples to that foil
c) wrap the works in glass fibre cloth (thin insulating layer) eg:

www.ecfibreglasssupplies.co.uk/c-429-pla...lassfibre-cloth.aspx

d) place another set of thermocouples on this layer
e) wrap that in final layer of foil to hold everything together

You could then run a set of calibrations where you co-relate the input electrical power to this delta temp across the layer. Without disturbing the thermocouple positions you could run the Celani wire and be much more certain that your calibration actually reflects the real heat flux out of the apparatus.

In my travels around the heat conduction calorimetry literature online it seems that there are several recommendations to measure the integral of this heat flux over time. ie. look at the kWh balance instead of the instantaneous kW balance. This is supposed to smooth over transients and give a more representative reading of the internal heat being generated.

bob

I see from the blog section that you have received info back from one of the heat conduction sensor suppliers. Unfortunately, if I understand the post these things are expensive and they are small.

My suggestion remains as I said in my previous post: build your own conductive sensor. All it would take is 3 thin layers; foil - poor heat conductor layer - foil. If the middle layer is thin and uniform, then the heat flux will be proportional to the difference in temperature across this layer. The inner foil layer will reflect back any IR radiation and the exterior foil layer will help even out longitudinal temperature differences and help hold thermocouples in place.

I would recommend adding thermocouple pairs at 3 locations along the wrapped tube: near end, middle and near opposite end. If during calibration runs you find that the temperature profile is non uniform you may need to add more thermocouple instrumentation. However if the temperature profile is reasonably uniform along the tube you may be able to calibrate the flux against the middle thermocouple pair.