Maximum Temperature greater than the boundary temperature

sathwik718 · May 19, 2014, 15:51

Hello Everyone,
The figure below shows a flow pattern with width and height of each channel is 100um. The bottom surface is maintained at a temperature of 70C and the gas enters at 65C. The second figure is a side view of the first channel of the four channels. The maximum temperature reaches 74C. The inlet condition for pressure is 40 psi, but in the pressure scne the pressure reaches 45 psi. I dont understand why this happens. Any kind of help is appreciated.

Thank you
isometric.png

channel1.jpg

pressure_scene.jpg

dvanb · May 19, 2014, 16:44

What is the Mach number of this flow? If it is up above .35 the stagnation temperature could be 75C if you are specifying your inlet value as static temp.

sathwik718 · May 19, 2014, 17:33

Quote:

Originally Posted by dvanb

What is the Mach number of this flow? If it is up above .35 the stagnation temperature could be 75C if you are specifying your inlet value as static temp.

Thanks. The velocity in each channel is around 273 m/s. That give the mach number around 0.8. How do I calculate the stagnation temperature?

dvanb · May 19, 2014, 18:05

Tstag/Tstatic = 1+[(k-1)/2]*M^2

Pstag/pstatic = {[1+(k-1)/2]*M^2}^(k/(k-1))

k is the ratio of specific heats for your gas, 1.4 for air.

You can also find tables of stagnation properties listed by Mach number.

May 19, 2014, 15:51	Maximum Temperature greater than the boundary temperature	#1
sathwik718 New Member Sathwik Singari Join Date: Apr 2013 Posts: 15 Rep Power: 13	Hello Everyone, The figure below shows a flow pattern with width and height of each channel is 100um. The bottom surface is maintained at a temperature of 70C and the gas enters at 65C. The second figure is a side view of the first channel of the four channels. The maximum temperature reaches 74C. The inlet condition for pressure is 40 psi, but in the pressure scne the pressure reaches 45 psi. I dont understand why this happens. Any kind of help is appreciated. Thank you isometric.png channel1.jpg pressure_scene.jpg

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May 19, 2014, 16:44		#2
dvanb New Member David VanBronkhorst Join Date: Sep 2011 Posts: 6 Rep Power: 15	What is the Mach number of this flow? If it is up above .35 the stagnation temperature could be 75C if you are specifying your inlet value as static temp.

May 19, 2014, 18:05		#4
dvanb New Member David VanBronkhorst Join Date: Sep 2011 Posts: 6 Rep Power: 15	Tstag/Tstatic = 1+[(k-1)/2]M^2 Pstag/pstatic = {[1+(k-1)/2]M^2}^(k/(k-1)) k is the ratio of specific heats for your gas, 1.4 for air. You can also find tables of stagnation properties listed by Mach number.