Simulation method of solar-driven absorption refrigerators for very low temperatures

A new solar-driven, NH3 H2O absorption-refrigeration system is proposed, which may refrigeration temperatures as low as −60°C, i.e. much lower than the temperatures obtained by conventional solar-driven, absorption-refrigeration units. A method for simulating the operation of the proposed system has been developed and correlations have been derived which allow calculation of the characteristic quantities of the system in terms of ambient temperature and available solar radiation only. The correlations derived are valid for ammonia mass fractions 15% (weak solution), 40% (rich solution) and 98% (ammonia vapour), and for ambient temperatures from 5 to 35°C. The hour-by-hour performance of the proposed system has been predicted for operation in the Athens area throughout a typical year, using mean climatological data obtained by statistical processing of hourly measurements corresponding to about 20 years. The prediction showed that during the year: 1.(a) The lowest refrigeration temperature varies from −60 (in January) to −44°C (in July).2.(b) For systems equipped with a triple heat exchanger the theoretical refrigeration power produced at about 1 p.m. varies from 45 W (in January) to 90 W (in July) per 1 m2 of solar collector aperture while the theoretical coefficient of performance varies from 28.7% (in July) to 30.4% (in January).