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Al_Pa_Cone

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**<<Moved from another forum, thus no template filled out.>>**

I am having some trouble trying to relate a question given in my distance learning lessons to the equivelent question in my assignment.

The assignement question is:

1(a) Superheated steam at a pressure of 40 bar and a temperature of 500°C is supplied to the turbine of a Rankine cycle. If the condenser pressure is 0.03 bar, find the thermal efficiency of the cycle. Neglect feed pump work.

I am instructed to use steam tables from:

"Thermodynamic and Transport Properties of Fluids"

S I Units

arranged by

G F C Rogers and Y R Mayhew

Basil Blackwell

Which I found a free online version of here:

https://www.slideshare.net/SGhallab/steam-tables-fifth-edition-by-rogers-and-mayhew

The Rankine Cycle I understand can be divided into two halfs, High pressure (Steam entering the turbine) and Low Pressure (Steam entering the condenser).

The Symbol notation in the below chart is as follows:

From the question superheated steam at a pressure of 40 bar and a temperature of 500°C would fall into this highlighted catagorie of the steam tables, and I am looking at the Enthalpy (the amount of internal energy required to conver 1kg of water to 1kg of steam) so I get 3445 kJ kg^-1

In my notes I have the the Thermal Efficiency (TE) = (h_1 -h_2)/(h_1-h_3)

h_1 i believe is 3445 kj kg^-1

h_2 is the Specific Enthalpy after the steam leaves the turbine and enters the condenser, so I am looking at the 0.03 bar pressure at 500°C and I understand I should use Interpolation to find the figure at 0.03 as the given figures are 0.01 to 0.05.

but I can see it is unchanged from the highlighted 3489 kJ kg^-1

Now I have a problem! In the lessons the example used gives a totally different answer to obtain h_2 and I cannot figure out how they got it.

Can anyone verify I am on the right course so far?

Thank you!

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