Modeling thermal inertia effects using the thermal resistance network approach on a small-scale high-temperature ORC system

Abstract

Organic Rankine Cycle technology is an effective way to convert low to medium-grade waste heat into electricity. Understanding the dynamic behavior of Organic Rankine Cycle systems is vital because they often operate under fluctuating operating conditions. Consequently, dynamic simulations are essential for system design and optimization; they can also predict real-time operational behavior and ensure system safety. This study used a thermal resistance network modeling method to simulate the dynamic behavior of heat exchangers in a high-temperature micro-organic Rankine cycle. The focus was on the transient effects caused by wall thermal inertia. The study examined three transient simulations in detail and validated their results against experimental data. The thermal resistance network method accurately predicted the cycle’s transient effects, offering a straightforward predictive tool for transient operations in waste heat recovery systems. Moreover, the study emphasized the critical impact of non-condensable gases on condenser performance, especially in systems with low condensing pressures.