(1)The efficiency of a heat engine operating between two thermal reservoirs @ te

Question

(1)The efficiency of a heat engine operating between two thermal reservoirs @ tempretures of 100 degC and 500deg C maybe as high as but not exceed:
a) 0.200
b) 0.485
c) 0.517
d) 0.809
e) 1.000
...............................................................................

a) mass is conserved

b) mass and energy are conserved

c) energy is conserved

d)exergy is conserved

e) places limits on the efficiency of processes.

........................................................................................... THANK YOU!!!!

Explanation / Answer

1) For the first one, carnot efficiency will be n = 1 - TL/TH

L stands for lower and H stands for higher.

Thus n = 1 - (100+273)/(500+273)

= 0.517

Actual efficiency cannot exceed carnot efficiency, Hence C.

2) The idealised cycle that is used to model steam power plant is Rankine cycle.

Hence D.

3) Rankine cycle with reheat

In this variation, two turbines work in series. The first accepts vapor from the boiler at high pressure. After the vapor has passed through the first turbine, it re-enters the boiler and is reheated before passing through a second, lower pressure turbine. Among other advantages, this prevents the vapor fromcondensing during its expansion which can seriously damage the turbine blades, and improves the efficiency of the cycle, as more of the heat flow into the cycle occurs at higher temperature.

Hence E.

4) The second law of thermodynamics places limits on the efficiency of process

Hence E.

1 => C

2 => D

3 => E

4 => E

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