Experimental and theoretical investigation of solar driven absorption chillers

Within the Vigoni Programme for cooperation between Italian and German universities, the University of Perugia and the Technische Universität Berlin have been carrying out in the last years a joint research programme on two similar solar driven absorption plants, with evacuated tube solar collectors and Water-Lithium Bromide thermosyphon absorption refrigerators of the same manufacturer, but of different cooling capacity. The performance – especially in part-load - of these systems is not as satisfactory as it should be theoretically, so the research focused on the phenomenon of the overflow of the refrigerant, in order to improve this situation and to forward the technology. A detailed analysis of the thermodynamic process was conducted, employing comparable and shared measurement chains; the results suggested a control strategy, which balances the machine in such a way that the evaporator is neither overflowing nor running dry.