- #1
gpsimms
- 30
- 1
Hey all,
First post, thanks in advance for any help. I see there is a lot of discussion on this site and others about nichrome heating elements. I apologize if my question is very similar to others, but I have not exactly been able to figure out what I need to learn/lookup to answer my questions from the other posts I have read. I'd appreciate anyone pointing me in the right direction.
OK, so I am a new graduate student working in a combustion lab. We want to preheat some fuel in a length of thin quartz tube, before it mixes with hot air. The tube has ID 1mm and OD 1/8". We want to heat the fuel (dodecane in some cases, but other gas fuels as well in other cases) at various pressures. For now, we are running atmospheric pressure but have plans to go to high pressure later.
With our mdot/cp and desired Temperature change (700K-300K) I have calculated the desired power to be ~13W.
The design is to be as follows: Wrap nichrome wire around a few inches of tubing. This would be best to be as short a length as possible. Use ceramic paper around the nichrome so it binds when it heats and it prevents shorts and provides an insulator.
My question is how do I exactly figure the length/thickness of the wire I need? I have been to http://www.cecs.wright.edu/balloon/images/2/22/Nichrome_Wire_Heating_Element_Design_Basics.pdf and a few websites like it.
Here are a few problems I am having with answering my question:
The link above says I need about 15 amps with 14AWG to get to the desired wire temp. It says to cut that amount in half for coiled wire, so 7.5 amps. Doesn't the length matter in that calculation? It seems like it should. Also, I should note we have thermocouples and temp controls. Does this mean I should just use any wire that can go above the desired temp and if connected to thermocouple/temp control it will be safe?
Sorry if these are really stupid questions. The problem is my background is only in math. I've never taken an engineering course before this year so I get overwhelmed a bit with these "real world" problems.
Thanks so much!
simms
First post, thanks in advance for any help. I see there is a lot of discussion on this site and others about nichrome heating elements. I apologize if my question is very similar to others, but I have not exactly been able to figure out what I need to learn/lookup to answer my questions from the other posts I have read. I'd appreciate anyone pointing me in the right direction.
OK, so I am a new graduate student working in a combustion lab. We want to preheat some fuel in a length of thin quartz tube, before it mixes with hot air. The tube has ID 1mm and OD 1/8". We want to heat the fuel (dodecane in some cases, but other gas fuels as well in other cases) at various pressures. For now, we are running atmospheric pressure but have plans to go to high pressure later.
With our mdot/cp and desired Temperature change (700K-300K) I have calculated the desired power to be ~13W.
The design is to be as follows: Wrap nichrome wire around a few inches of tubing. This would be best to be as short a length as possible. Use ceramic paper around the nichrome so it binds when it heats and it prevents shorts and provides an insulator.
My question is how do I exactly figure the length/thickness of the wire I need? I have been to http://www.cecs.wright.edu/balloon/images/2/22/Nichrome_Wire_Heating_Element_Design_Basics.pdf and a few websites like it.
Here are a few problems I am having with answering my question:
The link above says I need about 15 amps with 14AWG to get to the desired wire temp. It says to cut that amount in half for coiled wire, so 7.5 amps. Doesn't the length matter in that calculation? It seems like it should. Also, I should note we have thermocouples and temp controls. Does this mean I should just use any wire that can go above the desired temp and if connected to thermocouple/temp control it will be safe?
Sorry if these are really stupid questions. The problem is my background is only in math. I've never taken an engineering course before this year so I get overwhelmed a bit with these "real world" problems.
Thanks so much!
simms
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