Performance assessment of an NH3/LINO3 bubble plate absorber applying a semi-empirical model and artificial neural networks

In this study, ammonia vapor absorption with NH3/LiNO3 was assessed using correlations derived from a semi-empirical model, and artificial neural networks (ANNs). The absorption process was studied in an H-type corrugated plate absorber working in bubble mode under the conditions of an absorption chiller machine driven by low-temperature heat sources. The semi-empirical model is based on discretized heat and mass balances, and heat and mass transfer correlations, proposed and developed from experimental data. The ANN model consists of five trained artificial neurons, six inputs (inlet flows and temperatures, solution pressure, and concentration), and three outputs (absorption mass flux, and solution heat and mass transfer coefficients). The semi-empirical model allows estimation of temperatures and concentration along the absorber, in addition to overall heat and mass transfer. Furthermore, the ANN design estimates overall heat and mass transfer without the need for internal details of the absorption phenomenon and thermophysical properties. Results show that the semi-empirical model predicts the absorption mass flux and heat flow with maximum errors of 15.8% and 12.5%, respectively. Maximum errors of the ANN model are 10.8% and 11.3% for the mass flux and thermal load, respectively

Approach for the analysis of TES technologies aiming towards a circular economy: Case study of building-like cubicles

The objective of this study is to establish an initial framework to evaluate and improve the sustainability of technologies integrating thermal energy storage to come closer to a circular economy. This is applied to a case study for a building-like cubicle that includes different options of phase change materials. For the construction of a cubicle, materials can come from ores and virgin or recycled feedstock. In order to decrease the impact of materials and approach to a circular economy, the recycled content of materials at the start of life should be as high as possible. This recycled fraction in current supply depends on the available technologies for reintroducing the recycled materials in the production processes, together with virgin materials coming from primary sources. The results of the analysis show that the decrease of the environmental impact of recycling at the end of life is lower than 5%, while using recycled materials replacing virgin raw materials could reduce the overall impact by up to 30%. Most relevant materials are bricks, steel, and aluminum. Thus, reuse and recycling of materials and components must be integrated into the initial design in order to come closer to the concept of circular economy