Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Refrigerant purification in absorption chiller by heat and mass transfer optimization in falling films inside rectifier and generator

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire Systèmes Solaires Haute Température

01-10-2018

SL-DRT-18-0308

francois.boudehenn@cea.fr

From more than fifteen years, the development of air-conditioning offers more and more comfort to people. Major part of commercial air-conditioners uses electricity-powered vapor compression machines to provide the frigorific effect. The use of that technology must face to a paradox: more the number of air-conditioners installed in a city increases, more heat released to urban atmosphere rises, thus increasing the ambient air temperature which implies a decreasing the performance of the chiller and increasing the cooling load of buildings. In fine, peak electricity demand for cooling can be tripled. One of the solution could be the use of thermally driven chillers powered by waste-heat or solar energy. Ammonia-water chillers are particularly interesting because of their low production and maintenance costs. The main failing of this working pair is the small difference of volatility between the absorbent and the refrigerant, which implies the use of a rectifier to remove traces of water in the ammonia vapors at the outlet of the generator. In this context, the thesis will focus on understanding and modeling of coupled heat and mass transfers at the steam generation part (generator/rectifier) made by falling film. An experimental validation will be realized using an existing prototype at laboratory. This experimental and numerical validation will then make possible a global steam generation optimization aimed at improving overall compactness and increasing the performance of the thermodynamic cycle.

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