so the problem is: a low temp power plant operates with R-410amaintaining a temp

Question

so the problem is: a low temp power plant operates with R-410amaintaining a temp of -20C in the condenser and a high press of 3MPa with superheat. find the temp out of the superheater so thatthe turbine ext temp is 60C and find the overall cycleefficiency.

I've been looking at this question for a while and I noticed thatif the pressure going into the turbine 3 MPa (since the high pressis maintained at this pressure) then isn't it impossible for theexit temperature to be 60C? wouldn't it have to be something lowersince the entropy entering and exiting the turbine is supposed tobe the same.

Explanation / Answer

It seems like you need more information to answer this question. Isthere a mass flow rate of the working fluid given? Technically theentropy at the entry and exit of the turbine should be differentunless you're working with an isentropic turbine. If the turbine isnot isentropic then you should be given an isentropic efficiency ofthe turbine . If you are given that then you can find the actualwork of the turbine since: n(isentropic) = W(actual) / W(isentropic) If you can do that then you can find the efficiency of theexpansion cycle. Normally the work required by the pump is verysmall compared to the work output by the turbine, so the efficiencycan be found using: Ncycle = W(actual) / Qin I can't really answer your question because I don't have h valuesreadily available to me as I don't have a thermodynamics book onme. I hope this helps you, though

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