Two-phase flow heat transfer coefficient

[dRic2]

So what do you want to do next?

I'd like to know what $h$ I should use in the case that the outlet flow rate has a quality of steam of 0.2 (20%). Thanks again for your time.

For example is 1st case ($v_l = 4.5$ m/s) I get $h_l \approx 20000$ and $h_v \approx 10000$ W/m^2/°C

 

[Chestermiller]

Bird, Stewart, and Lightfoot give typical values for forced convection of 500-10000 for water. For gases, 50-500. Is it possible that you are using too small a diameter?

What fraction of the tube length is covered before the vapor begins forming. Also, the entire tube length after that is not going to be 20% quality.

 

[dRic2]

Ok so my approach has changed. The final goal is to find a suitable value for $h$. The steam generator I am considering is one from a nuclear power plant so I looked for papers about steam generators which met the data I have in mind and I reverse-engineered the problem and I calculated $h$ from $Q = UA \Delta T_{ml}$. I have found a value of $h$ from 9000 to 12000 (slightly changing some parameters to see how much they weight). This looks ok, I think. Only thing I don't like is that I also get a velocity for the liquid of 0.34 m/s... I have really no idea whether this could be a reasonable value or not. I was expecting something around 3 or 4 m/s but I'm not sure

 

[Chestermiller]

Ok so my approach has changed. The final goal is to find a suitable value for $h$. The steam generator I am considering is one from a nuclear power plant so I looked for papers about steam generators which met the data I have in mind and I reverse-engineered the problem and I calculated $h$ from $Q = UA \Delta T_{ml}$. I have found a value of $h$ from 9000 to 12000 (slightly changing some parameters to see how much they weight). This looks ok, I think. Only thing I don't like is that I also get a velocity for the liquid of 0.34 m/s... I have really no idea whether this could be a reasonable value or not. I was expecting something around 3 or 4 m/s but I'm not sure

If you are aware of the design and operating conditions in the actual plant, are you doubting your ability to back out the flow velocity? That value doesn't seem very unreasonable to me.

 

[dRic2]

are you doubting your ability to back out the flow velocity?

Well... I always blunder a lot of stuff when doing calculations... so I never actually trust myself if I don't have an idea of what the result might look like.

Anyway, assuming I didn't make a mistake I found the value which seems to agree with your predictions/considerations. Thanks again for your time.