Posts by Paradigmnoia

Due to increasing the fan voltage, I calibrated the fan delta T contribution again. Now it is 0.45 C instead of 0.25 C. So the power into the fan seems be heating the air ultimately. Of course this extra bit of delta T is included in all output measurements, calibration and any excess events. It should probably be tested at several different, higher ambient temperatures, to be certain that the fan adds heat to hot air as much as to cold air.

Then I started to mess with heating up the fan... and after a few short experiments I worked out that any heating up of the fan requires ultimately heating the air going through it, and the same input power, minimum, as the delta T would normally require is required to raise the delta T at the downstream TC (if the air is mixed). So short of directly heating the outlet thermocouples there is no free lunch of delta T increasing due to heating the fan by some mysterious way.

I did shine a very bright incandescent flashlight at the outlet thermocouples with a possible 0.1 C increase.

And then I did a full 8-crossing (every 45 degrees) hot wire anemometer traverse, and also the vane anemometer capturing 100% of the airflow. More on that later.

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Quote from CWatters

Rigid foil covered PIR house insulation is quite cheap and readily available. If you used 100mm thick sheets glued and with aluminium tape on internal and external seams you could get away without an aluminium frame to support it. A plug door from two sheets would allow access.

PIR has a thermal conductivity of 0.022W/mK. If we estimate the surface area at 2sqm heat loss could be limited to less than 0.5W/K.

Mizuno in here..

http://lenr-canr.org/acrobat/MizunoTincreasede.pdf

..seems to run his calorimeter with a delta T of perhaps 10-20C?

So losses through the walls could be reduced to perhaps 5-10W.

Perhaps less as I've probably overestimated the surface area.

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That is pretty much my plan. I already have the polyiso R6 foil-faced foam board, and a sheet of R10 pink foam board.

I have the ogre of the hot wire vs vane anemometer tests to deal with first. That should be a barrel of fun...

The inlet thermocouple is currently protected from emissivity effects by a strip of bubble foil bubbles.

The air going around my body is being sucked into the box (when I stand right in front of the inlet), and the room is currently quite cool (circa 10 C), so the air being drawn in is being heated by body. Certainly not very many watts worth, but some. This raises the inlet temperature 0.7 C in my experiment. It took about 3 minutes for the outlet temperature to report a 0.2 C increase. It would probably take a long while for this inlet 0.7 C temperature change to propagate fully to the outlet, but most assuredly it will, as would any constant air temperature change at the inlet.

Also in my case, the bubble foil is on the outside, with a 1 cm gap between the bubble foil and the acrylic box (for the most part), so emissivity effects in general are prevented from the outside of the calorimeter.

Next test I will use willpower to raise the delta T. (There is no try, only do or do not).

However, I am uncertain which way is best to do this. Shall I concentrate on heating the outlet thermocouples, the air inside the box, the reactor, or lowering the inlet thermocouple temperature?

Reflecting outlet air seems to have done nothing to the Delta T.

Body heat barely a blip (It was only 4 minutes).

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Like I said before, the inlet thermocouple knows I am present. Normally the inlet temperature climbs 0.1 to 0.2 C if I am in the vicinity of calorimeter. I normally keep clear while things are running, but take a note when I am adjusting something.

I am looking forward to looking at the last batch of data. After the new fan speed settled, I set up a board to reflect the outlet air back over the calorimeter for several hours.

Stood in front of the calorimeter 20 cm from the inlet. Raised inlet temperature 0.7 C, but only 0.2 at the outlet. Maybe it might catch up at the outlet but I didn’t want to stand there for an hour to find out.

Reset the blower voltage to 10.45 from 8.55 to more closely match the Saito values.
Delta T dropped to 13.5 from 15.

Fired up the box again.
Returned to the 6 x 9.5 cm opening, but now the opening cover is sealed on and the auxiliary 5 cm hole capped with tape. Also impaled the inlet TC into a strip of bubble foil to block IR from the calibration cylinder. Ran for 4 hours without input heat to test fan heat leakage, which is delta 0.25 C .

Now back to 200 W input and see what else bumps the delta T, if anything, once the calibration settles.

Quote from JedRothwell

It is very cheap.

The specific heat is 0.35 to 0.50 Btu/lb/°F, which is 1.5 to 2.0 J/gK. I do not think that is a high thermal mass. Also, the bubble insulation is inside the acrylic, so very little heat reaches the acrylic.

Bubblefoil on the inside? How does it stay in place? If you have any photos with the bubble foil installed I would like to see some.
Anyway, at R 1.1, it won’t make much difference except the heat won’t radiate out.

Quote from JedRothwell

Do you mean because of the thermal mass of the calorimeter components?

Yes, exactly. Mostly due to the acrylic.

The acrylic looks great, and is easy to verify is sealed well where the panels come together.
But probably is a waste of money, and certainly, cumulatively, is a waste of experiment time.

It probably smooths out the outlet heat a bit, so it isn’t all bad.

Quote from RobertBryant

From your photos the thermal mass of the calorimeter box may be significant in increasing the response time of the calorimeter..

In the case of Mizuno's 20 kg reactor the calorimeter box mass (assuming 1/4 inch thickness with rough calc.. ) is ~15kg

The thermal mass of the reactor= massxCp=20,000x0.5 =10000 J/C

The thermal mass of acrylic = 15000x1.5 = 22500 J/C ..

I found that it was necessary to include the thermal mass of the acrylic to get a reasonable calorimeter heat balance at start up.

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I mentioned before that the calorimeter is responsible for a significant part of the delay in steady state operation.

I recommend that the acrylic not be used at all for calorimeter design. I am building a new box with the same interior dimensions, but with 1“ isocyanate foam (R6) with aluminum facing, covered by R10, 2“ pink Corning foam board. With an access panel on one side.

Here is last nights experimenting.

Restricting the inlet definitely has an effect, but still only raised the outlet temperature (Delta T) 0.6 to 1.0 C . It may be a little higher, because the inlet temperature climbed a bit also, even with fairly high velocity air passing over it due to the restriction. However, the overall effect is obvious.

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(The heater is inside the sealed 20 x 50 SS cylinder.)

Quote from LDM

As far as I know they did a verification of the in band emssivity for their dogbone thermal test.

I am not aware that they verified the broad band emissivity.

If so can you provide a link ?

No, they could not verify the broad band emissivity. But they did not calculate radiant power either.

The alumina: https://content.evernote.com/s…peg?resizeSmall&width=404

Photos (old)

Uninsulated with SS calibration cylinder

Insulated box

Quote from Ascoli65

OK, now I better understand your situation. Did you ever published a photo of your experimental setup?

Anyway, the base room temperature is not a problem and not even the cooling or heating of the box. Heating and cooling of a warmer than air component by a fan heater (not an IR one) or an AC unit cause the same response, the component cool down! See what happened during the INFN test in 2012 (*). The only important thing to replicate is the increase of the air speed around the experimental setup, in your case the box, therefore a simple fan is more than sufficient.

As for the inlet temperature to the box, it has no or just a minimal influence on the estimate of the output power. The main variations are on the outlet temperature and, IMO, its value is strongly influenced by the air speed around the box.

(*) The NEDO Initiative - Japan's Cold Fusion Programme

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There are photos of my arrangement in either in this thread or the sealed Mizuno air calorimetry thread.

The inlet temperature should be the room ambient temperature, and therefore affects the exterior temperature of the calorimeter box, and the rate at which the box loses heat to the environment, (or the rate at which the outer environment can affect the box). I can confirm that without the air gap, the exterior bubble foil was quite warm at just 200 W input, especially the top. Since the bubble foil has very low emissivity, convection carries most of the heat away to the room from the outside of the box, so air speed around the box would have an especially strong effect.

Quote from Ascoli65

It's obvious that the overall time constant is dominated by the reactor mass, which is 10x greater than the box mass, but the down spike + recovery transients only involve the box and the air inside it, so no wonder that their time constant is 1/10 of the global one.

Please consider that the air inside the box, whose exit temperature provides an estimation of the heat produced inside the reactor, is heated by the reactor and cooled by the internal walls of the box. The first delta T is 10x the second one, but the surface of the box walls are 10x to 100x greater than the reactor external surface, so that the temperature of the internal air is very sensitive to the temperature of the box walls, which in turn are very sensitive to the velocity of the external air. Therefore during the down spikes, only the box mass is involved in the transients, not the reactor mass. The temperature of the reactor is not affected, because the internal air always flows at the same speed and the delta T between the reactor and the internal air is much greater than the temperature fluctuations of the box walls.

You have the opportunity to easily verify this behavior by testing it. If you wish.

At the moment it is a bit tricky for me to test the effect of cooling the box exterior, even with the air gap removed between the bubble wrap and acrylic, because my shop is currently about 9 C, and the heater (not used for these experiments) is an IR unit.

Conversely, heating the exterior could act similarly but oppositely to cooling the exterior.
However, I don’t see how this escapes notice of the inlet thermocouple. At 10 C, my inlet thermocouple increases by 0.1 to 0.2 C just from me being within 4 m of the calorimeter.

The problem is that the MFMP actually measured the emissivity of their device.

Another 200 W run going now with the inlet restricted to 5 cm diameter hole. Changed the inlet hole size after steady state was again reached with the previous inlet size. I think this should be a bit restrictive and drive the delta T upwards a bit by decreasing the total volume of air through the calorimeter.

Unplugged the fan for 60 seconds and got a nice long heat burst. So fan drawing current all the time is important. Eventually it reverts to the normal steady state after the fan is plugged back in.

Quote from JedRothwell

2. Even if the temperature was different, and it was not a magic violation of thermodynamics (meaning it did not mean more energy was coming out of the hotter cell), this magic would have no effect on the calorimetry. Because the calorimetry is not based on the reactor surface temperature. It is not based on the internal temperature either.

I ran the numbers back when this thread was new. A high emissivity reactor could be cooler than a low emissivity reactor in the calorimeter. The temperature of a low emissivity reactor climbs to where convection and conduction rates improve enough to match the loss in radiant power compared to a high emissivity reactor. In this case total power remains the same, even with a hotter or cooler reactor surface due to emissivity.

And a fan underneath!