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Development of a new concept of compact and low-cost absorption chillers: application in solar cooling for hot climates

Author(s) : ALTAMIRANO CUNDAPI A.

Type of monograph: Doctoral thesis

Summary

Energy consumption worldwide is increasing at alarming rates, especially in developing countries. In the building sector alone (most energy demanding sector), the energy consumption for space cooling has more than tripled in 26 years (from 1990 to 2016), and it is expected to triple again by 2050, with around 70% of this increase coming from the residential sector. Nowadays, the need for cooling is almost totally covered by conventional vapor compression systems. This dependence on electricity is already generating problems of electricity distribution grid saturation in hot-climate countries, reaching over 70% of peak residential electrical demand during hot days in some regions of the world. In this context, the Mexican case is especially delicate since it is the second country in the world with the highest share of electricity used for space cooling (14%). Moreover, Mexico depends energetically and economically on fossil fuels.
Absorption chillers represent an alternative to vapor compression systems since they operate with natural refrigerants and can run on clean heat sources such as solar energy and waste heat. However, these systems are, until now, expensive and bulky. In spite of the efforts to address different aspects to reduce the manufacturing costs, size, and improve the efficiency of absorption chillers, they cover until now a very small niche market (1% of the total cooling needs in the building sector). The present PhD thesis shows the development of a new generation of absorption chillers based on a new adiabatic sorption technology. Specifically, the proposed technology was studied for small capacity residential applications with a solar thermal source in countries with high solar irradiation, such as Mexico.
Chapter I provides a deep state of the art on the investigated working fluids and exchanger technologies for absorption chillers in small-capacity applications. Since no standard characterization parameter for the sorption exchangers was found in the literature, Chapter II presents the concepts of thermal and mass effectivenesses generalized for non-adiabatic sorption exchangers (the mass effectiveness of adiabatic sorption exchangers being intrinsically included in this definition). The implementation of these effectivenesses to characterize the sorption exchangers of absorption chillers is shown through examples at the component and at the system scales with the NH3-LiNO3 working fluid. Furthermore, given the importance of the characterization of absorption chillers, other absorption chiller modelling methods with different insight levels are also presented and discussed.
The study of a solar-geothermal absorption air conditioning system in the Monterrey (Mexico) context was addressed in Chapter III. In the first part, the comparison of the two conventional working fluids (NH3-H2O and H2O-LiBr) and an innovative working fluid (NH3-LiNO3) was performed through a steady-state model. Moreover, the dimensioning of the components of the system and a short economic viability study are proposed. In the second part, a single-stage absorption chiller with an innovative bi-adiabatic configuration is presented and studied by means of a dynamic model. The model was first used to define the nominal operating conditions of the absorption chiller and the minimum performance requirements of the components. After this, its use to cool down a house on a typical sunny day in the Monterrey climate conditions is analyzed and discussed. Finally, the last chapter presents a new generation of adiabatic falling film sorption exchanger for absorption chillers. The characterization of this exchanger in desorption mode was performed for a wide range of operating conditions. The experimental results show very high performances and validate the potential of the proposed adiabatic sorption technology. Therefore, based on these results, the construction of an absorption chiller based on this technology seems very promising.

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  • Original title: Development of a new concept of compact and low-cost absorption chillers: application in solar cooling for hot climates
  • Record ID : 30030793
  • Languages: French, English
  • Subject: Technology
  • Publication: Université savoie mont blanc - France
  • Publication date: 2021/01/14

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