for. Oatley
The cup is topped with a cover that has a small hole. If I assume a perfect black body cavity, a carbon disc inserted in the cup will be as hot as the cup is. Any deviation from perfect black body behaviour will make the carbon disc less hot that it's cup surroundings I presume. We...
We use type K thermocouples in another set up where a convection oven is used at around 950 C. The type K temperature measurement in that "atmosphere" set up works with great stability. The type K is indeed stable in an oxidizing atmosphere. Howvever, a type K used in vacuum is just not stable...
I have a question regarding the so called "black body cavity".
I am working with small Molybdenum cups (height 6 mm; d = 4 mm; bottom thickness 2mm; wall thickness 0.2 mm) A set of stainless steel radiation shields (3) is mounted around the cup in its vertical direction. The cup top opening is...
As you say the heat transfer takes place between a heated or chilled roller and different type of films. The roughness of the roller combined with the (most probably) stretching force in the film would certainly produce some relevant heat transfer capable contact area. The film is pressed...
Dear all
I finished the first series of measurements on the application of EPDM O-rings for use down to -40 C in static vacuum sealing. A report is attached to this post.Thank you all for your interest and suggestions.
Onno
Summarized this the result:
An environmental chamber to be used in...
Dear MaxTemp
IRStuff makes a very good remark. What is the 10000 W/m^2 heat source exactly? How big is the plate where it dumps it heat?
I would consider the following: when you do transient simulations you'll end up with the steady state system situation after some simulation time. (consider...
Dear reader
As a last thing to add to this thread I will show the measured results for the degradation of type K thermocouple as used in a vacuum furnace (P < 1e-6 mbar). It is quite destructive.
The protective sheath, Al2O3, at the tip of thermocouple that faces the thermocouple threads was...
Dear btrueblood
That is interesting waht you have to say about the oxidizing of tungsten with exposure to air. The furnace we are working with is under high vacuum: p<1e-6 mbar. And we try to keep it clean from dust and fingerprints. It is good practice to bring up the furnace chamber back to...
Dear all
We are considering a tungsten rhenium thermocouple:type C. We found out that it is used in 2 other set ups inside our laboratory to measure temperatures in vacuum furnaces between 800 and 2000 C. It appears to be a stable type couple for use in high temperature vacuum furnaces. I am...
Dear reader
We tested a new thermocouple type K connection 3 times. The measured temperature just goes down at each high temperature heating step. 150 C difference between measurement #1 and #3.
About the pyrometer. We installed a Hamamatsu infrared photo diode above the cup with 760 nm pass...
Dear reader
We are measuring temperatures between 750 and 1200 C using a thermouple type K (wire = 0.2 mm). The thermocouple touches the bottom of a small sample cup made of Molybdenum (h= 11 mm and d= 7 mm).
We are discussing the possibility that at these high temperatures the metals from the...
Thank you Tom
That is very valuable information. It primarily shows that I have to look for another supplier i.e. a supplier with a more detailed and knowledgeable character. The one we use now is more a off the shelf (just try it and see if it works) supplier.
I have a deep freezer now (-45...
Dear all
I promised I would be back with some measurement results on this question.
I tried to measure heat transfer between 4 and 1000 mbar in a CO2 atmosphere. As a first idea I used an aluminium clad power resistor of 50 Watt, type Dale 15,2 ohm, L = 50 mm, h=15 mm. I hang this up in a tank...
Dear flexibox
Thank you for this nice overview. I have some comments on it.
-Ethylene Propylene: -54 C to +150 C
This is what I am testing at the moment. As said I have done two tests with EPDM and they seem to loose their seal at -20 - 30 C. However, yesterday I found a small hard spot on the...
