In Rankine cycle there is a concept of Tm(mean temp of heat
addition)For calculating the efficiency of the cycle we
generally use
n=1-T2/T1

again Tm taking into consideration we get
n=1-T2/Tm

as T1>Tm so he efficiency will be different for same cycle.


Can anybody explain how is it possible?
advance appriciation for your effort




Answers were Sorted based on User's Feedback



In Rankine cycle there is a concept of Tm(mean temp of heat addition)For calculating the efficienc..

Answer / balajee

in the rankine cycle
t1 is greater and t2 will be lesser in temperature.
therefore the mean temp tm will be less then t1 and greater
than t2.

hence the efficiency will be differ

Is This Answer Correct ?    5 Yes 1 No

In Rankine cycle there is a concept of Tm(mean temp of heat addition)For calculating the efficienc..

Answer / ab_ina7

sorry i didn't get your question...i think (1-t2/t1) is used for reversible cycle like carnot cycle...for rankine cycle
(h1-h2)/(h1-hf4) is used....

Is This Answer Correct ?    2 Yes 1 No

In Rankine cycle there is a concept of Tm(mean temp of heat addition)For calculating the efficienc..

Answer / palash

thanks for the reply Balajee.Yes the efficiency will differ in he two calculations.
But my question was how can there be different efficiency for a same cycle?

Can you help?

Is This Answer Correct ?    0 Yes 0 No




In Rankine cycle there is a concept of Tm(mean temp of heat addition)For calculating the efficienc..

Answer / shubham

n(carnot)=1-t2/t1 which is an ideal cycle.and n(carnot)is grater than n(rankine)both being in ideal condition.so in question u have used a wrong formula for n(rankine)-1 equat.u cannot use this for rankine cycle.

Is This Answer Correct ?    0 Yes 0 No

In Rankine cycle there is a concept of Tm(mean temp of heat addition)For calculating the efficienc..

Answer / hisham tariq

eff=1-(T2/T1)---------CARNOT EFFICIENCY (IDEAL CYCLE)
eff=1-(T2/TM)-------------RANKINE CYCLE EFFICIENCY

CARNOT EFF > RANKINE EFF

If you know the rankine cycle and molliers diagram there you will find turbine entry temperature (T1) and economizer entry temperaure (T4). TM is the mean of both values.

PS: eff of rankine cysle can also be calculated by
(h1-h4)/(h2-h3)
Since, h=U+PV and U=TS -PV .So h=TS ,if you plug this guy in above formula with T replaced by Tm yoy gonna get same eff

Is This Answer Correct ?    0 Yes 0 No

In Rankine cycle there is a concept of Tm(mean temp of heat addition)For calculating the efficienc..

Answer / palash dolai

I understand the difference now.All have explained in nicely.
I thought both formula can be used for same cycle.

Is This Answer Correct ?    0 Yes 0 No

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