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...
Hello to all
I am involved in a low temperature application of O-ring seals. A tank of 1 m length and 50 cm diameter has a flange at each side at must be sealed. Tank vacuum: better than 1e-5 mbar. Temperature range : -40 C to + 60 C. Gas permeability from atmosphere to vacuum is an issue.
At...
Dear all
I think I have not been at my best with the last response.
IRstuff is very right in questioning whether natural convection actually occurs in the test set up. I have flushed the tank with 160 mL/min CO2 gas. Considering the volume of the tank, 50 L, it is immediately clear that these...
Dear all
I would like to add the results of some testing in my laboratory as it seems to clarify the question posed in this thread a little bit.
I mounted a aluminium clad resistor (RH-50,50 W maximum power:length app 3 cm, diamter app. 1 cm))in a stainless steel volume of 70 cm length and 30...
Hello
I would like to add out of general interest that CuO is reactive to water at room temperature. I do not know whether this is importance to your plans but I thought I should add it.
Best regards
Onno
Hello
I would like to add that Helium is an inert gas: non reactive chemically to other compounds even at elevated temperatures. If the Helium gas flow is clean enough you should be able to use a thermocouple placed directly in the flow without chemically reacting away the thermocouple. You...
