Criteria for selection of working fluid in low-temperature ORC

Abstract

The economics of an ORC system is strictly linked to thermodynamic properties of the working fluid. A bad choice of working fluid could lead to a less efficient and expensive plant/generation unit. Some selection criteria have been put forward by various authors, incorporating thermodynamic properties, provided in literature but these do not have a general character. In the paper a simple analysis has been carried out which resulted in development of thermodynamic criteria for selection of an appropriate working fluid for subcritical and supercritical cycles. The postulated criteria are expressed in terms of non-dimensional numbers, which are characteristic for different fluids. The efficiency of the cycle is in a close relation to these numbers. The criteria are suitable for initial fluid selection. Such criteria should be used with other ones related to environmental impact, economy, system size, etc. Examples of such criteria have been also presented which may be helpful in rating of heat exchangers, which takes into account both heat transfer and flow resistance of the working fluid.

Archives of Thermodynamics

“…Those are dry fluids, which means that expansion in turbine takes place only in the superheated region of the temperature-entropy property plot. On the one hand this is beneficial to thermal efficiency of expansion devices and the turbine working conditions (less erosion due to lack of condensation in turbine), on the other hand dry fluids have larger areas of heat transfer compared to wet and isotropic fluids [11].…”

Reverse Engineering of Working Fluid Selection for Industrial Heat Pump Based on Monte Carlo Sampling and Uncertainty Analysis

“…Further, when a set of target properties is identified, the determination of the influence (or importance) of these properties on the process model output often relies on expert knowledge. 18,19 The problem of property uncertainties in the context of chemical product design has already been addressed by several authors, and the work of Ng et al 20 gives an overview of the studies carried out in this domain. In particular, Maranas 21 used multivariate probability density functions for chemical properties incorporated into the problem formulation.…”

“…The noncontinuous search space also makes classical contour mapping of the property search space unsuitable as an analysis tool for the product-process design problem. Further, when a set of target properties is identified, the determination of the influence (or importance) of these properties on the process model output often relies on expert knowledge. , …”