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Heat Transfer of Gaseous Hydrogen to an Orifice Plate

Heat Transfer of Gaseous Hydrogen to an Orifice Plate

Heat Transfer of Gaseous Hydrogen to an Orifice Plate

(OP)
I am a graduate student in mechanical engineering and am doing an independent research class. One of the things I need to do is to calculate the heat transfer of high temperature gaseous hydrogen on an orifice plate in a rocket nozzle simulator. I drafted up a rough sketch and have attached it below. I will also need to calculate pressure difference, to determine the force on the plate.

The issue is that the orifice plate will likely experience the highest heat load in the system, surpassing what the material can withstand. So an active cooling method must be explored. One of the first big steps I need to make is to calculate the heat transfer from the hot gaseous hydrogen to the orifice plate. I'm inclined to classify this as a forced convection problem. But I am unsure how to initially approach the problem since the orifice plate is the object of interest and would be normal to the internal pipe flow. So I doubt I can use parallel, internal pipe/flat plate flow analysis?

The variables in the schematic are either given or assumed. I would have provided some numerical values, but I am not allowed to disclose such information. Any tips or insight from others is appreciated. I am also interested in any software that could simulate this kind of problem. I tried out Energy2d, but it is not uncodnitionally stable, so it blows up when dealing with high temperature, high velocity convection flows such as this.

RE: Heat Transfer of Gaseous Hydrogen to an Orifice Plate

I really think you are going to have to let us know some details, such as what effects you want considered in the fluid flow, whether the problem is axisymmetric, whether you think think turbulence needs to be modelled, etc etc. I realise that this is all top secret but otherwise people are just wasting time suggesting out of context solutions. My guess is the exhaust is moving pretty damn fast, compressibility will be important, turbulence likewise, transit times will be brief.

Cheers

Greg Locock


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RE: Heat Transfer of Gaseous Hydrogen to an Orifice Plate

Just for grins i ran a couple of cases in a 2d windtunnel simulator. it doesn't allow for a completely enclosed orifice plate, but these results are axisymmetric around the lower x axis.

At high m values (I didn't bother running M>1 for obvious reasons) there's a big stagnation zone in front of the plate, and a huge one behind




This leads to a hot spot on the front of the orifice plate and a cooling effect behind



The same effects are present at lower speds but there is less temperature differential



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Heat Transfer of Gaseous Hydrogen to an Orifice Plate

(OP)
GregLocock you are correct. The exhaust is moving at about 5.35m/s (fast relative to the length). So transit time is very brief (~0.19s). Compressibility and turbulence should be considered. And utilizing axisymmetry is a good point and I think is the way to go. Thanks for sharing your simulations. I should point out that the mach number is extremely low (around M = 0.0014). This is due to the extremely high temperature (~2800 K) and gas constant.

What software did you use for those simulations? I have just downloaded OpenFoam. I am unfamiliar with it though.

RE: Heat Transfer of Gaseous Hydrogen to an Orifice Plate

I used microCFD but it is indicative only, an educational tool rather than a full blown simulation package. It won't go down to .0014 M or up to 2800K, and doesn't do heat transfer.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Heat Transfer of Gaseous Hydrogen to an Orifice Plate

Just idly wondering, with a speed of the order of 2 m/s, perhaps you could revise the profile of the orifice to give laminar flow, and then you won't get two dead zones, and so the thermal issue will be a simple steady state calculation.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

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