Refrigeration Cycles

International Journal of Refrigeration, 2010

The present study deals with a compression-absorption machine. The proposed hybrid cooling system uses water-ammonia as a working fluid and operates at three pressure levels. The absorber is at an intermediate pressure (Pint) taken between the evaporator pressure (PEV) and the condenser pressure (PCD), unlike the single stage machine, which works between two pressure levels. The proposed new system is studied and compared to the conventional machine. In order to evaluate the performance of the invoked system, a procedure based on the MAPLE software is set up to compute accurately the thermodynamic properties of the working fluid. The analyses of the numerical results highlight that the performance of the novel proposed configuration is better than that relative to the conventional cycle. The study reveals the great impact of the intermediate pressure on the performance improvement and on reducing the generator temperature allowing the system to work at low enthalpy sources. In fact, for an evaporator temperature and a condenser temperature fixed respectively at-10 and 40°C, the proposed hybrid refrigeration cycle operates at a generator temperature TGE = 75°C and the installation's COP is about 0.56. While for the same conditions, the single stage machine COP cannot exceed 0.51 with a generator temperature of about 100°C.

Thermodynamics - Systems in Equilibrium and Non-Equilibrium, 2011

Energies, 2020

The interest in employing absorption refrigeration systems is usually related to electricity’s precariousness since these systems generally use thermal rejects for their activation. The application of these systems is closely linked to the concept of energy polygeneration, in which the energy demand to operate them is reduced, which represents their main advantage over the conventional vapor compression system. Currently, the solution pairs used in commercial absorption chillers are lithium bromide/water and ammonia/water. The latter pair has been used in air conditioning and industrial processes due to the ammonia operation’s low temperature. Few review papers on absorption chillers have been published, discussing the use of solar energy as the input source of the systems, the evolution of the absorption refrigeration cycles over the last decades, and promising alternatives to increase the performance of absorption refrigeration systems. There is a lack of consistent studies about ...

Entretien de 20' sur les compétences interculturelles et les compétences pour une culture de la démocratie.

Frontiers in Psychology, 2018