Steam flow across valves and restriction orifices (final year project work)

[ts124]

Hi, I would be grateful for anyone to give some advice on how to solve the following problem.

I am a part-time student working in an energy from waste facility in the UK and have decided to base my BEng project on a steam pipe bleed expansion vessel associated with the steam turbine generator set we have on site.

To set the scene.... I have multiple steam pipelines leading into a header pipe which is attached to an expansion vessel. Within each pipe is a control valve (Kv: 7.9) and then a restrictive orifice plate (11mm). I need to find out the fluid properties after the orifice plates in order to size an expansion vessel to suit the system. The pressure in each pipe before the control valve differs but for this example I will use 70.5 bar(g).

My problem is; I require the fluid properties after the orifice plate but currently have no way of knowing the pressure in the pipeline between the valve and orifice plate. As the current system is operational I am unable to get the required design information from flow meters as there are none installed.

I hope that my question makes sense and appreciate any help you can give me.

 

[GHartmann]

Promoting, selling, recruiting, [highlight #FCE94F]coursework[/highlight] and thesis posting is forbidden

 

[ts124]

This project is also a work based problem. I am not looking for calculated answers. All I require is for someone to point me in the correct direction.

 

[davefitz]

ts124,

You have not defined the pressure in the expansion tank. If that pressure is less than 50% of the initial upstream pressure , it is likely that you have acoustically choked flow. Usually the choke point that defines the flowrate is the location of minimum flow area, which is either the 11 mm orifice plate or the valve's vena contracta.

One brute force way is to iteratively , assume a flowrate, and calculate the pressures and velocities throughout the system. Calculating forward from source thru to the valve outlet is the first half of the calculation with constant enthalpy , and you would determine the velocities and pressures at each point from source to valve outlet . The second half of each calculation is to calculate , backwards, the pressure from the orifice outlet to the valve outlet . If at no time the indicated velocity exceeds soundspeed, then acoustically choked flow has not occurred. If the pressures do not match at the valve outlet, then a different flowrate must be used , and the process is recalculated.

"Whom the gods would destroy, they first make mad "

 

[ts124]

Davefitz,

Thanks for your help, this is a good starting point for me and was what I was looking for. The expansion vessel for this system is open to atmosphere. I also forgot to mention that the RO is only 0.2m away from the valve outlet and the header into the atmospheric expansion vessel is only another 0.2m away from the RO. The valve and RO are located directly next to the vessel.