# Homework Help: Steam driven turbine: Heat, Power, evaporation

1. Aug 3, 2011

### hootie

1. The problem statement, all variables and given/known data

A steam driven turbine generates 200 MW of mechanical power at tan eficiency of 32%. The temperature of the steam at the input is 500 C, and at the output it is 200C

a: How much power is input as heat to run this turbine?

b: How much power is lost in hear to the environment?

c: What is the max ifficiency of any system used to do work with these input and output temps?

d: If the waste hear is used to to evaporate water, how many kilograms of water can be evaporated in one hour?

2. Relevant equations

a: Qh = work/efficiency = 625MW

b: Qh - Work = 425MW

c: carnot engine: 1-(Tc/Th) = 1-(473/773) = .338

d: Not sure: Q = mc(delta T)

3. The attempt at a solution

As you can see a, b, and c are figured out. I'm not sure how to approach d. No temp is given for the water, so I can't get delta T.

2. Aug 3, 2011

### rock.freak667

You have the waste heat being used to evaporate the water. So it is changing from a liquid to solid. So that waste heat will provide the latent heat to change the phase.

(you can be more technical and have the latent heat + sensible heat, but as you said, you are not given a temperature so no ΔT - unless you assume an atmospheric temperature)

EDIT:I meant liquid to gas not solid, my bad

Last edited: Aug 3, 2011
3. Aug 3, 2011

### SteamKing

Staff Emeritus
If you are evaporating water, it is changing from a liquid to a gas, not a solid.