Repositori URV

Identifier: imarina:5128534

Handle: https://hdl.handle.net/20.500.11797/imarina5128534

Authors:
Alvarez, Maria E.Esteve, XavierBourouis, Mahmoud

Abstract:
A triple-effect absorption cooling cycle using aqueous (lithium, potassium, sodium) nitrate solution (Alkitrate) as a working fluid in the high temperature stage is simulated in this work. This cycle takes advantage of the thermal potential of high temperature heat sources and has a configuration consisting of a H2O/LiBr double-effect cycle coupled with a single-effect cycle that uses Alkitrate as a working fluid. Heat is exchanged between the two cycles by thermal fluids which flow in the external circuits. The conventional working fluid H2O/LiBr suffers from serious problems of corrosion and thermal decomposition at temperatures of over 180 °C, which restricts its use in the high temperature components of a triple-effect absorption cooling cycle. At the nominal operating conditions selected, namely a heat source temperature TH of 250 °C and a cooling-water temperature TC of 30 °C the coefficient of performance achieved with the Alkitrate topping cycle is 1.73. The correct operation of the cycle is demonstrated by drawing the cycle in the Dühring diagram, where the safety margin for the crystallization of the working fluid is adhered to. Results show that the Alkitrate triple-effect cycle has a slightly higher efficiency as compared to the H2O/LiBr triple-effect cycle at generator temperatures of over 180 °C. Moreover, the practical operation of a H2O/LiBr triple-effect cycle at temperatures higher than 180 °C suffers from the above mentioned problems related to the thermal stability and corrosion of the working pair.