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SUBJECT-THERMAL ENGINEERING-II.�BRANCH- MECHANICAL ENGINEERING.�SEMESTER- 4^TH.�CHAPTER- FIFTH.�FACULTY- ER. CHANDAN KUMAR NAYAK.�

TOPIC- STEAM POWER CYCLE

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INTRODUCTION

In steam power plants and refrigeration cycles, the working fluid changes from liquid to vapour and back to liquid state. This succession of processes is called vapour cycle. In steam power plants, water is the working fluid in the form of steam and vapour.
In refrigeration cycles gasses such as Freon, CO₂, and ammonia (aqua-ammonia) are used as working substances.

ELEMENTS

The elements of steam power plants are as follows:

Boiler

Steam turbine

Condenser

Feed pump

RANKINE CYCLE�

RANKINE CYCLE

The simplest way of overcoming the inherent practical difficulties of the Carnot cycle without deviating too much from it is to keep the processes 1-2 and 2-3 of the latter unchanged and to continue the process 3-4 in the condenser until all the vapour has been converted into liquid water. Water is then pumped into the boiler upto the pressure corresponding to the state 1 and the cycle is completed. Such a cycle is known as the Rankine cycle. This theoretical cycle is free of all the practical limitations of the Carnot cycle.

CARNOT CYCLE

In a vapour cycle, all the theory remains the same as thermodynamic cycle except the working substance, which is steam. The steam may be in any form, i.e. wet, dry or saturated or superheated. A Carnot cycle steam as a working substance is represented on the p-v and T-s diagram in Figure.