Hi Ash and Andrew,
Here is the data sheet for Bostik Matrix FC
This is a thixotropic polyurethane. A thixotropic gel relates to how the material is applied and essentially reacts like the inverse of a non-newtonian liquid in that it becomes 'thinner' (more liquid) when stirred or agitated. I would hope this is not the case after it is cured as certain conditions in these coils can lead to recursive microphony and that could liquefy your material.
You will note that the maxium service temperature is 80°C while some polyurethanes are actually used as thermal insulation (See http://www.assanpanel.com.tr/en-us/Q...s/Attach.1.pdf) Like Glen's Silicone covering, the real temperature of your resistor wire may not be making it out to the outer surface of the material due to the very low thermal conduction and very high heat capacity of the material. I might add here that the original Ainslie group had temperatures over 50°C above ambient (~20°C) so your material is at its limits if these condition were to surface.
You also have two other factors of importance. You have used a stranded insulated wire. We do not know what the insulation material is around your wire, but if that wire is a type of heater wire then the insulation is probably a silicone material. It could take days of constant heat for your resistor to fully equalize and present the correct temperature to the outside world depending on how far the wire is above ambient. Next we would need to have a look at the stranded wire specifications to determine how current through the wire relates to heat. A chart like this one is helpful in determining the expected temperatures due to current flow in a tightly wound coil of the material.
Rosemary contends the energy observed as increased heat (above that expected by current flow) is partially a result of matter fluctuations which increase with the mass of the wire. So according to her thesis she expects there to be an increase in heating as the wire size is increased. This result is counter intuitive because classically we expect the heat to be caused by resistive means. Where her case could be partially supported by the classical Joule heating in the cross section of a thick wire while current flow on the skin produces the necessary induction, we are still left to determine the source of the surplus heat that seems to be present.
Also, I might draw attention to your ferrite core which also serves as a thermal sink and radiator and can adversely impact the expected temperature.
Here is the data sheet for Bostik Matrix FC
This is a thixotropic polyurethane. A thixotropic gel relates to how the material is applied and essentially reacts like the inverse of a non-newtonian liquid in that it becomes 'thinner' (more liquid) when stirred or agitated. I would hope this is not the case after it is cured as certain conditions in these coils can lead to recursive microphony and that could liquefy your material.
You will note that the maxium service temperature is 80°C while some polyurethanes are actually used as thermal insulation (See http://www.assanpanel.com.tr/en-us/Q...s/Attach.1.pdf) Like Glen's Silicone covering, the real temperature of your resistor wire may not be making it out to the outer surface of the material due to the very low thermal conduction and very high heat capacity of the material. I might add here that the original Ainslie group had temperatures over 50°C above ambient (~20°C) so your material is at its limits if these condition were to surface.
You also have two other factors of importance. You have used a stranded insulated wire. We do not know what the insulation material is around your wire, but if that wire is a type of heater wire then the insulation is probably a silicone material. It could take days of constant heat for your resistor to fully equalize and present the correct temperature to the outside world depending on how far the wire is above ambient. Next we would need to have a look at the stranded wire specifications to determine how current through the wire relates to heat. A chart like this one is helpful in determining the expected temperatures due to current flow in a tightly wound coil of the material.
Rosemary contends the energy observed as increased heat (above that expected by current flow) is partially a result of matter fluctuations which increase with the mass of the wire. So according to her thesis she expects there to be an increase in heating as the wire size is increased. This result is counter intuitive because classically we expect the heat to be caused by resistive means. Where her case could be partially supported by the classical Joule heating in the cross section of a thick wire while current flow on the skin produces the necessary induction, we are still left to determine the source of the surplus heat that seems to be present.
Also, I might draw attention to your ferrite core which also serves as a thermal sink and radiator and can adversely impact the expected temperature.
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