So, I get to the point you are at and then it appears that unless we know what the wall temp is, we can't know what the internal air leaving our duct section is. Why is it possible that I can find the answer to this using a CFD package but it appears unsolvable by hand at this point?
I am sure...
Well, the air would be around 700°F so I suppose that for the case where the r-value of the insulation is low, I would assume radiation to be significant. My intention was to formulate a script that would essentially solve for both of these edge cases: The case where we want to radiate heat from...
I have attached a drawing with equations that I would use. I suppose it is actually not a finite difference equation... I am merely breaking the duct into dx lengths in an attempt to account for an ever changing wall temperature traversing down the duct.
Basically, it appears that I have 2...
Hi.
I have been trying to solve this problem that has been keeping me up at night for a coupe weeks at least. If anyone can help me, I would be greatly appreciated.
Hot air enters a cylindrical duct. The duct has some R-value and radiation and convection is being accounted for on the outside...
So continuing along this path leads us to separating and integrating the first equation which leaves us with: $$T_W = (T_{i+1} - T_ie^N)/(1 - e^N)$$ where $$N = -\frac{h_{in}D\pi}{mC}\Delta x$$
So, now at each iteration, I should know my ##T_i## but I will be guessing ##T_{i+1}## Then I have...
The temperature of the air will vary axially (let's say z-coordinate) and radially (r-component). No, I am not considering this. I simply am saying that the air flow is abstracted with an average temperature which is passing energy to the duct wall via convection (again using an abstracted...
Hi. There is a problem that I have been working on and I seem to be getting somewhat unrealistic results. Can anyone critique my modeling method?
Problem: Heated air enters a duct of length L at temp T_h. The outside of the thin walled duct will have convection and radiation both being...
In the derivation of the adiabatic lapse rate, upon using the 1st law of thermodynamics: Why is potential energy neglected? The parcel of air is doing work PdV which is balanced by the internal energy term, cvdT.
I can't think of a reason to neglect gravitational potential energy here.
Thanks.
Hi.
Here is my story: I received my engineering BS and MS from universities that are both highly ranked. After working in industry for 1-2 years I am back in school pursuing my PhD. The program I am currently at is not well known and has only just started a PhD program. The lab is well funded...