• solare
• solar
• ORC
• low temperature
• eiettore
• cogenerazione
• cogeneration
• ciclo Rankine
• bassa temperatura
• waste heat recovery

The objective of this work is the study and the modeling of a cogeneration system that features an Organic Rankine Cycle (ORC) coupled with an ejector refrigeration cycle. The ejector refrigeration cycle structure is basically analogue to that of a standard vapor compression cycle, with the difference that the compressor that is normally present in the latter will be substituted with an ejector to operate the compression in its stead.
The specifics of the system that is sized and analyzed in this work come from the idea of a collaboration between the University of Liège, the company Enertime and the school ESPRIT (Ecole Supérieure Privée d’Ingénierie et des Technologies) in Tunis. The goal of the project is to study and build a prototype of a small scale ORC system, which utilizes water heated by concentrating solar collectors, coupled with an ejector refrigeration cycle.
The ORC will recover heat from the source available at low temperature and will have a hydrocarbon or a refrigerant as working fluid. The best fitting fluid will be selected among the conventional options for similar applications, as a balanced solution for the necessities of high efficiency, safety and low environmental impact.
The most relevant features of the ejector refrigeration cycle are its relatively simple structure, low construction costs and the complete lack of moving parts, which make its operating costs negligible once the device has been properly realized. The other refrigeration technologies that could be coupled with a thermal power cycle, from the conventional vapor compression cycle to the absorption or adsorption ones, normally show higher energy and exergy efficiency, but the systems are relatively complicated, resulting in a higher capital investment.
Most theoretical works on ejector cycles are either specifically focused on the isolated ejector device itself, or tend to describe its behavior in a simplified way while focusing on the whole cycle’s characterization instead. Furthermore, while several structural choices and enhancements have been proposed for the ejector cycle, only the simplest architectures are usually investigated in the combined cycle analyses.
The idea behind the present work is to adopt an intermediate approach, exploiting the capabilities of a one-dimensional model as much as possible and adapt it in order to predict the ejector’s behavior when it is not operated under design conditions. Different working fluids and system architectures are presented, and the effect of possible enhancements to the cycle is investigated.