Investigation of the Effect of the Regenerative Heat Exchanger on the Performance of Organic Rankine Cycles Using Perturbed Chain–Statistical Associating Fluid Theory Equation of State

Axel Groniewsky,Csaba Wagner

doi:10.1021/acs.iecr.0c03782

Abstract

In the following study, two of the most commonly used and analyzed organic Rankine cycles (ORC), one with a basic set and another one with a regenerative heat exchanger, are investigated at differe...

Highlights

The organic Rankine cycle (ORC) has been in the focus of research activity in energy technology lately as it offers a solution to utilize low-temperature heat sources for electricity generation where the traditional steam Rankine cycle has its shortcomings
Three main working fluid categories are distinguished based on the shape of the liquid−vapor saturation curve in a T−s diagram: 1. Wet working fluids − the vapor saturation curve has a negative slope; the expansion line enters the two-phase region, which makes superheating an essential part of the cycle to avoid droplet erosion in the expander machine
An optimization framework was created on the Matlab platform to implement the continuous-molecular targeting approach to computer-aided molecular design using the PC-SAFT equation of state as the thermodynamic model

Summary

Introduction

The organic Rankine cycle (ORC) has been in the focus of research activity in energy technology lately as it offers a solution to utilize low-temperature heat sources for electricity generation where the traditional steam Rankine cycle has its shortcomings. The principles of the technology itself were established back in the 19th century, the installation of new plants has boomed in the last decade as the transition of the energy industry started shifting toward climate-friendly solutions. The total installed capacity was about 2700 MWel in 2017, as shown by Tartiere et al.,[1] mainly composed of multi-MWel geothermal applications, industrial waste heat, and biomass plants in the 10−150 kWel range and a few solar ORCs with concentrating collectors. Wet working fluids − the vapor saturation curve has a negative slope; the expansion line enters the two-phase region, which makes superheating an essential part of the cycle to avoid droplet erosion in the expander machine White and Velasco propose an approximate analytical method to obtain the liquid−vapor saturation curve in a reduced temperature−entropy diagram.[2,3] Deiters et al investigated adiabatic processes in the liquid−vapor two-phase region with several equations of state.[4,5] Zhang et al suggested a selection and evaluation method based on the turning point on the saturated vapor curves of the working fluids.[6,7] Usually, three main working fluid categories are distinguished based on the shape of the liquid−vapor saturation curve in a T−s diagram: 1. Wet working fluids − the vapor saturation curve has a negative slope; the expansion line enters the two-phase region, which makes superheating an essential part of the cycle to avoid droplet erosion in the expander machine

Methods

Results

Conclusion