Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

 Mar 29th 2019, 12:53 AM #1 Junior Member   Join Date: Mar 2019 Posts: 1 N2 Heater Hello everyone, this is my first post. I hope I am in the correct spot. I am 13 years old and trying to design a N2 heater for my dad, so he can use it on his race car. I'll explain My dad uses Nitrogen to inflate his tires before a race. The perfect pressure is about 25-28 psi for optimal grip. However, The tires are cold at the start, so to allow for expansion he sets them at 15psi. They normally take about 25 laps to heat up and get to max temp of about 230f. I suggested using hot nitrogen at the start of the race to give him an advantage because it will take less laps to heat up and give him a better grip advantage over the other racers. (tire warmers are now allowed like they use in nascar, but no rules about using hot n2) I am designing a cylindrical case with a electric heating element that will allow me to preheat the n2. I am trying to decide how many watts of power I will need to preheat the flow. I know the volume of the tire, (and flow) but I am having a hard time figuring out the temp change of the n2 once it goes through the heater. in the supply cylinder, its about 2000psi. It will drop to 30psi, and I know this will lose alot of heat. can someone point me in the right direction how to figure this out. Thanks
 Mar 30th 2019, 07:10 AM #3 Senior Member   Join Date: Apr 2017 Posts: 513 Here's another idea .... Fill the tire with air and a small amount of hydrogen . At the start of the race a small electrical spark inside each tire ignites the mixture instantly raising the temp and pressure . By experiment it should be possible to determine the right % of hydrogen , and the correct start pressure , to get the final temp and pressure require .... Whichever way you do it there is still the problem of the cool tire reducing the temp of trapped gas by conduction. topsquark likes this.
Mar 30th 2019, 07:24 AM   #4
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Join Date: Apr 2017
Posts: 513
 Originally Posted by Jaek I am designing a cylindrical case with a electric heating element that will allow me to preheat the n2. I am trying to decide how many watts of power I will need to preheat the flow. I know the volume of the tire, (and flow) but I am having a hard time figuring out the temp change of the n2 once it goes through the heater. in the supply cylinder, its about 2000psi. It will drop to 30psi, and I know this will lose alot of heat. can someone point me in the right direction how to figure this out. Thanks
You really don't need to know the exact amount of watts , it can only be done by experiment ...

I would take the heating coil out of a hot air gun or similar and vary the amount of power you feed it with a high power mains dimmer ...

 Mar 30th 2019, 08:57 AM #5 Senior Member   Join Date: Apr 2017 Posts: 513 Burning hydrogen has many disadvantages .... awkward and difficult to measure ... it burns to water vapor which will condense and cool the gas... Here is the ultimate solution .... bore a hole through the wheel into the tire airspace , thread the hole . The bolt which will be screwed into this hole has a tip containing a mixture of charcoal and potassium nitrate with an ignition hot wire.. At race start the pellet is ignited electrically raising the tire pressure and temperature by the release of hot carbon dioxide .. The threaded bolt with pellet and igniter would be cheap to make , always the same size . The idea could catch on . Start your own company , you could be a millionaire before you leave school ! topsquark likes this.
 Mar 31st 2019, 05:50 AM #6 Senior Member     Join Date: Jun 2016 Location: England Posts: 1,069 Safety First Some of Oz's ideas seem a little dangerous for a 13 year old... The hot air gun idea could work, but be careful. Ideally if your Dad is good at engineering and electrical work get him to help. If not, I am sure that among his racing buddies he will know someone with the appropriate expertise to advise you on how to do this without hurting yourself. __________________ ~\o/~

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