Calculating Turbine Efficiency for Chemical Plant with 2 MW Process Heat Output

[HeatInMyPants]

Homework Statement

Steam is bled from a turbine to supply 2 MW of process heat in a chemical plant at 200 deg-C. State 4 is saturated liquid water at 200 deg-C. If the turbine inlet condition (state 1) is 5 MPa, 500 deg-C and the turbine exit pressure is 10 kPa, determine (a) the quality of steam at the turbine exit, (b) the bleed pressure in MPa (assume no frictional forces), (c) the bleed rate (in kg/s), and (d) the mass flow rate into the turbine (kg/s) if the turbine produces an output of 2 MW.

Homework Equations

The Attempt at a Solution

Don't even know were to start... Thanks

 

[Jmf]

Firstly, a disclaimer - I've studied some engineering thermodynamics, but I'm by no means an expert. Take what I say with a pinch of salt.

My first thought is that by looking at the appropriate steam/water tables (saturated or superheat) we can find the (specific) enthalpy of the water/steam at states 1 and 4. We can then write down the Steady Flow Energy Equation (heat in minus work out = enthalpy change) for each of the two processes. We can also assume conservation of mass and assume that the mass flow rate into the turbine is equal to the mass flow rate out - and similarly for the other process that you have on that diagram, if that's relevant.

If the turbine were reversible and adiabatic - then we could also write that the change in entropy across the turbine is zero, which might help us.

Hopefully we can generate enough equations to solve for all our variables. I hope this helps somewhat - if not I'll have a go at the analysis myself (don't have the time right now) and see if I can solve it. It doesn't seem like a very well-posed question though.

:)