Performance of a solar driven compound NH3/H2OH2O/LiBr absorption refrigeration system in athens

A solar driven, high efficiency, compound refrigeration system is considered, made up of two cooperating absorption parts, which use NH₃/H₂O and H₂O/LiBr solutions, respectively. Solar heat is given to the vapour generator of the NH₃/H₂O unit, and the heat produced by the absorber and the condenser of this unit is supplied to the vapour generator of the H₂O/LiBr unit. A method for simulating the operation of the compound system has been developed and applied for predicting the hour by hour performance of the system operating during the typical year in Athens, for which solar radiation and ambient temperature data are available. An optimization study for the compound and the individual cycles has also been made. Very high performance of the system has been predicted. For example, on 21 May, the calculated theoretical coefficient of performance is 219% while the corresponding theoretical values of single H₂O/LiBr and NH₃/H₂O units are 93% and 65% respectively. The corresponding calculated cooling power produced by the system is 543 W/m²-collector. An annual analysis shows that the cooling produced by a NH₃/H₂O unit in Athens is 0.87 GJ/m²-year, while the present compound system gives an impressive increase to 3 GJ/m²-year.