3 replies to this topic

[SimonTecnoill]

Hi to all....i've a problem. I have to calculate the position and the time of complete evaporation of a continuous water flow wich is injected trough a nozzle into a continuous flow of steam in superheated condition. The position (and than the time) at wich i'm sure that there aren't water droplets is really important, 'cause i've to choose the position of a thermocouple wich detects the effetc in temperature of the desuperheating stage. Clearly, the measurement of the thermocouple is wrong if is reached by water droplets.

I know all the macroscopic thermodynamic conditions of the system.

In your opinion, have i to consider the water flow according to a continuous or discrete approach? And if discrete....how could i manually calculate the diameter of the droplets of water?

I don't want to use CFD!!!!

Could someone suggest a theoretic approach to the problem???

[SSWBoy]

Is this a theoretical excercise, because in Industry all you do (generally) is specify a mixing distance between the injection quill and the downstream temperature element, typically I see ten pipe diameters quoted.

As a side note, you would never set the control loop to bring the superheated stream back to its saturation point typically you would just use Saturation + 10 degrees C.

I don't really see why you would want/need a more accurate measurement of the mixing distance, but if you do perhaps you can describe the situation a little more and we can help.

[SimonTecnoill]

thanks for your answer....but I could show you hundreds of applications in wich the rules of ten pipe diameters creates a lot of problems. As a result, the water droplets not evaporated reached the thermocouple, which, than, indicates the temperature of saturated steam and couldn't detect the actual temperature of the attempered steam. This creates an allarm in the control loop. It's a big problem....and customers are not satisfied with simple rules!!!!

P.S. : sorry for my bad English!

[SSWBoy]

Out of interest what are these applications where it is so necessary?