Abstract
The dispersed power source is recognized as one of solutions for energy saving. Since demands of heat are smaller than those of electricity in case of using this kind of power source, the redundant thermal energy is put off for nothing. If we can regenerate the power from waste heat, the thermal efficiency of the dispersed power source system is increase. Though a steam turbine cycle can be used for the regeneration of power, water (H2_O) may not be used as a working fluid of this power cycle because of the low temperature of waste heat. In this paper, we show the evaluation and selection methods of the working fluid for the power cycle operating with the low temperature heat source. In the cases where a pure substance was adopted as the working fluid, the substance was assumed to be in tow-parameter corresponding states so that constants of the substance could be predicted. We selected a similar substance whose constants of substance close to predicted values, and then we evaluate this substance by means of a software package for thermophysical properties of fluids. In the case of a mixture, the performance of the simple Rankine cycle was optimized on the combination of substances and the mixing ratio. A group contribution equation of state was used to calculate the properties of the mixture, because it could calculate large amount combinations by published interaction parameters.
