CHARACTERISTICS OF AN IDEAL WORKING FLUID

    CHARACTERISTICS OF AN IDEAL WORKING FLUID

We all know any thermodynamic power cycle depends on some working fluid for the transfer of heat from source to the point where it is converted to some useful work. Picking a working fluid for any vapour power cycle is not a random decision, since in case of any malfunction caused by it can lead to danger to human life and can cause huge operation and maintenance cost. While choosing a working fluid for a vapour power cycle one should keep following points in his mind. These points suggests the properties of ideal working fluid.

1.  The working fluid should have high critical point temperature so a working fluid with high critical point temperature can provide the opportunity of using considerably lower pressure to reach the higher temperature.

2.  The saturation pressure at the temperature of heat rejection should be above atmospheric pressure.

3.  The working fluid should have lower pressure at higher temperature.

4.  The specific heat of working fluid should be less so that little heat transfer is required to reach the boiling point.

5.  The freezing point of the liquid should be below room temperature such that they don’t get solidified in the pipelines.

6.  The saturated vapour line of T-S diagram should have steep enough such that the turbine expansion line is almost parallel to it and turbine exhaust point doesn’t become very wet.

7.  The liquid should be chemically stable and should not contaminate the material of construction at any temperature.

8.  The fluid should be non-toxic, non-corrosive, not excessively viscous and it should low in cost.