Gas Thermal Conductivity
Gas Thermal Conductivity
(OP)
Helium has a thermal conductivity 5times that of air (air is .0257 W/(mK) where helium is .1513 W/(mK)). If I have a container filled with 90% air and 10% helium, will the thermal conductivity be dependent on the ratio too?
Reference my heat previous thread, below:
http://www .eng-tips. com/viewth read.cfm?q id=299758& amp;page=1
Reference my heat previous thread, below:
http://www





RE: Gas Thermal Conductivity
Patricia Lougheed
******
Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: Gas Thermal Conductivity
based on the mole fraction of your constituents, but remeber the approximation is only good at low pressures and well above the critcal temperatures
RE: Gas Thermal Conductivity
Thus, multi-pane window systems suddenly went from 2+ inch airspaces to some thing like 3/16".
Similarly, A long time ago rule of thumb for heat sink fins in still air was at least 1/4 inch between fins to encourage useful amounts of convection.
RE: Gas Thermal Conductivity
NASA TECHNICAL NOTE
APPROXIMATE FORMULAS FOR VISCOSITY AND
THERMAL CONDUCTIVITY OF GAS MIXTURES
by Richurd S. Brokaw
Lewis Reseurch Center
CZeveZund, Ohio
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. NOVEMBER 1964
You can also refer to Kent"Power" 12thedition, pg 3-15 on method to appx such value K=(b)x(mu)x(Cv). Determining the specific heat (Cv) of the mixture is well documented and I would think that you can approximate the viscocity =(mu) of the mixture the same way. The values of constant "b" from 1.31 for complex gases, 1.70 for triatomic gases, 1.90 for diatomic gases, 2.44 for monatomic gases.
RE: Gas Thermal Conductivity
RE: Gas Thermal Conductivity
Patricia Lougheed
******
Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: Gas Thermal Conductivity
The project is to be similar to HIP operation, but much faster. I need 10Atm of pressure. I would normally use 10Atm of air, but the heat transfer rate of air is low. I could use 100% helium, but helium is expensive. So, the ideal situation would be to get the heat transfer properties of helium and the low cost and pressure from air. So 90% air and 10% helium would be ideal.
If I could recycle the helium for low cost, then there is no need for air. Any options or suggestions would be nice!