A colleague of mine and I have written a short paper describing the computer simulation results for a simple conduction calorimeter. We'd like to donate this paper to the MFMP cause. What is the best way to do this?

bob

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Thanks

Bob

I like to use electrical analogies for thermal sytems.. The math for electrical systems is very well known. The flow of current is identical to the flow of heat. Voltages are related to temperature. Currens flow corresponds to heat flow. Capicitance is analogous to mass. In thermal terms, the thermal transport is proportional to the temperature differemce between any two points. In electrical terms, the current flow across a fixed resistor is defined by the voltage difffenrence between the two measurement points and the resistance. The electrical circuit forms an exact analog computer simulation of the physical thermal model. The proposed calorimeter suggests measuring the temperature differemce betweem two points in a fixed physical substance (the ceramic coating). Using both the thermal and electrical models, this strategy will work. Of course you must define thetsystem. \

jdk 3/29/2014

I think what you are proposing is an analog computer simulation: en.wikipedia.org/wiki/Analog_computer

This could certainly work, especially for more difficult transient effects.

bob

I was thinking of a tool to use to help grasp the behaviour of the themal system. I know the electrical analagy is valid. I understand electical circits better than the complex thermal equations. The analog simulation is easily conducted with spice simulation - such as LTSPICEIV from Linear Tech. A current source is used as a heat source. A cpacitance represents the mass of the node. The system schematic is automatically used to formulate the differential equation and this is computed and solved by spice and the result is plotted. It is a simple digital simulation of a simulated analog computer. I would use this digital tool as an aid to increase understanding of the thermal system.
The proposed calorimeter seems to have a semi-insulating shell around the reactor. I think the proposal suggests taking the inside temperature and the outside temperature of this shell. This is analagous to having a heat source (current source) flowing through a thermal condiuctance (resistor). As long as the physical properties of the shell remain stable, the temperatue differnce will be equal to the heat flow. Electrically, this is the same as a current source feeding a resistor.
Since the thermal shell is outside of the reaction chamber, it will be hopefully immune to any changes in its composition and resulting thermal transport changes. I think this is the fllaw of the gas calorimeters. The gas, being internal to the reaction chamber undergoes chemical (ie H2 to H) and physical (Pressure to new presssure) changes which in the electrical analogy is equivalent to having an unknown variable resistor in the calorimeter calibration circuit.
I have a calorimeter design in my head. It is simply a metal or glass tube just as we already use. Around the outside of the tube we would cast about a 1-2 cm thick shell with a castable cerramic. A pair of themocoouples could be embedded in the slurry before it hardens. One thermocouple should be very near the inside of the ceramic. The other thermocouple should be very near the outside of the shell. Modeling clay and cardboard can be used as removable molds for the cement slurry. A precision calorimetric instrumental addition seems within reach jdk 4apr2014

Hi jdk,

Would you be willing to take on such an approach? Maybe we could get a working group together that you could lead and we run as a mini-project. What is your opinion on that?

Bob

@jdk. I like your thoughts on a castable ceramic. Although we didn't run the simulation without the internal Al tube, there were indications in our test matrix that it was important to smooth out longitudinal variations in temperature. Ie. to avoid a sensitivity to position of temperature probes vs heat source.

I still like the thin air gap between two concentric Al tubes as a low cost option as well.

Bob

The simulations of some electric and chemical processes in a mass flow heat conduction calorimeter are shown.