HIGH temp measurement. 1

[sjewenp]

I'm working on a test rig for a new heat exchanger that will see temps up to around 1700 F. My medium is He, so I'm concerned about leakage. What's the best way to take temperature readings at this temperature?

 

[MintJulep]

You want to measure what? Surface temperatures or gas temperature?

 

[sjewenp]

Whoops. Gas temperature, sorry. I know of no thread sealant which can handle those temps and I'm afraid of leakage if I weld a thermowell into the pipe. (plus, my pipe inner diameter is only around 13 mm so I have some flow restriction issues also)

 

[hacksaw]

13 mm pipe, I guess it depends on the wall thickness

what is the velocity and how well is the tubing insulated? radiation is going to be a big problem

 

[IceStationZebra]

Depending on how dynamic your application is you might be able to use IR to measure the pipe temperature. Just make sure you account for the type of finish used. Just google emissivity for more info. ISZ

 

[NickE]

How about a really small thermocouple on a dryseal compression fitting?

 

[sjewenp]

my wall thickness is 10 mm.
i am using a series of radiation heaters around my piping to achieve my temperatures and my heaters are right next to the location i will need to read. won't this make IR ineffective?

 

[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 probably should take into account the radiation loss of the thermocouple mass. However a simple, single radiation shield should solve this problem.

We use: Thermocouple type C W-5% Re/W-26% Re for temperature measurements in vacuum well above your 1700 F (1200C)

Best regards

Onno

 

[IceStationZebra]

I was envisioning the sensor being at least a couple of feet down stream from the heaters. Some of the IR energy from the radiation heaters will bounce off of the pipe and into your sensor, but you could solve that with a shield to prevent direct line of sight. The bigger issue is that you are trying to measure the temperature as it leaves the heat exchanger, and the pipe surface temperature will most likely be hotter than the He at that point.

One big factor that you left out is accuracy and response time. If high accuracy or fast response is needed you will end up with an exposed thermocouple. The next step down in accuracy/speed would be a thermocouple in a thermo-well. Then lastly you have a thermocouple clamped to the pipe or an IR sensor.

ISZ

 

[unclesyd]

I would give Omega a call. These instruments work very well.

http://www.omega.com/temperature/pdf/os1592.pdf

Anecdotal:
Prior to Vanzetti being absorbed by Omega I was talking to the headman about a possible temperature measurement on the expander wheel tips in our HNO3 plant. I told him the conditions 12500 RPM at 250 psig with a temperature of 1200F. There were 12 blades on this particular. His immediate response was do you want an average of all the tips or individual tip temperatures. We went on to measure individual tip temperatures.

 

[IceStationZebra]

Good catch uncle syd, I checked their site and missed that one! ISZ