Effects of the Working Fluid Charge in Organic Rankine Cycle Power Systems: Numerical and Experimental Analyses

Abstract

It is well known that organic Rankine cycle (ORC) power systems often operate in conditions differing from the nominal design point due to variations of the heat source and heat sink conditions. Similar to a vapor compression cycle, the system operation (e.g., subcooling level, pump cavitation) and performance (e.g., heat exchanger effectiveness) of an ORC are affected by the working fluid charge. This chapter presents a discussion of the effects of the charge inventory in ORC systems. In particular, both numerical and experimental aspects are presented. The importance of properly predicting the total amount of working fluid charge for optimizing design and off-design conditions is highlighted. Furthermore, an overview on state-of-the-art modeling approaches is also presented.

Organic Rankine Cycle based waste heat recovery modeling and control of the low pressure side using direct condensation and dedicated fans

“…The pressure ratio is widely used, together with the expander speed, to correlate the expander efficiency (Lemort et al, 2009) (Ziviani et al, 2018). In this work, the efficiency map of the expander is created from about 50 operating points, where the condensation pressure is varied from 1 to 3 bar and the evaporation pressure is varied from to 30 bar.…”

Performance modelling and greenhouse impact assessment of a micro-ORC energy system working with HFCs, low GWP fluids and mixtures

“…Six main parameters can be controlled from the outside: the hot source temperature and flow rate at the evaporator inlet, T H2Ohot and ̇H2 Ohot , cold source temperature and flow rate at the condenser inlet, T H2Ocold and ̇H 2Ocold , feed pump frequency, f pp , and number of resistive loads activated, n loads . Plus, the subcooling level at the condenser outlet, ∆ , which depend on the fluid charge, the cold source temperature and the noncondensable gas content [7]. Since the ORC model is formulated as an implicit problem, its solution is determined through an iterative process, whose iterative variables are the condensing pressure ( ) and the expander inlet temperature ( 1 ).…”