In this work, different CFD models to compute flows inside a steam ejector were investigated. The results were compared to the analytical models as well as the experimental results from the literature. All the simulations gave realistic results from the hydrodynamic perspective with a relative error of the entrainment ratio between 25% and 40% compared to reference experimental data. However, an analysis of the temperature profiles showed that only realistic results from the thermodynamic perspective were given by multiphase calculations. The first multiphase model tested was the so-called Wet-Steam model from ANSYS Fluent. This model gave inconsistent results for the steam ejector CFD simulation due to the physical boundaries of this model. The second model tested was the Eulerian mixture model, which gave the most realistic results in terms of the physical conditions of the liquid and vapor phases inside the ejector. It also showed that the phase change could have a significant impact on the value of the critical output pressure as a way to improve the performance of the ejector.

Solar Heat for Industrial Processes (SHIP) is a growing-interest concept in the context of the reduction of both energy consumption and greenhouse gases emissions. As industry often needs cooling power at negative temperatures, solar-fuelled NH3/H2O absorption systems can be employed for this task. In the context of the FriendSHIP European project, different innovative solutions are investigated for cooling production at -20°C and -40°C from 100-250°C solar heat. The first proposition concerns a GAX (Generator-Absorber heat eXchange) cycle based on Plate Heat Exchangers (PHE). This innovative design improves heat and mass transfers, thus performance. In addition, manufacturing costs decrease, as the needed components are standardized and available in the market. Two variants are simulated on EES (Engineer Equation Solver) for -20°C and -40°C cooling production. Other absorption cycles are modified to fit PHEs, in particular the pressure-staged cycle, the vapour-exchange cycle and the Semi-GAX cycle. They all are two-stage cycles and are simulated for -40°C cooling production only. The numerical comparison allows identifying the best solutions for the SHIP integration, giving an overview on the operating temperature ranges for each cycle. In particular, the following results are obtained. At ambient temperature T_AMB = 20°C and below, the GAX cycle is the most performing one. It shows a maximum Coefficient of Performance (COP) of 0.53 for a cold production T_E,OUT = -20°C (+27% compared to the single-stage cycle), and a COP of 0.36 at T_E,OUT = -40°C (+60% than the single-stage cycle). For T_AMB > 30°C, the pressure-staged cycle with GAX is the preferable one, as it can be operated with COP>0.15 at T_AMB up to 50°C. The Semi-GAX cycle seems the most adapted to operation at low heat source temperature, being able to operate down to 80°C with COP>0.20.