2010 ventas_ammonia lithium nitrate compresion booster.pdf

Applied Thermal Engineering 30 (2010) 1351e1359 Contents lists available at ScienceDirect j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / a p t h e r m e n g Ammonia-lithium nitrate absorption chiller with an integrated low-pressurecompression booster cycle for low driving temperatures R. Ventas a,*, A. Lecuona a, A. Zacarías b, M. Venegas a a Departamento de Ingeniería Térmica y de Fluidos, Universidad Carlos III de Madrid, Avda. Universidad 30, 28911 Leganés, Madrid, Spainb Academia de Térmicas ESIME Azcapotzalco, Instituto Politécnico Nacional, Av. de las Granjas 682, Col. Santa Catarina, 02550 D.F. México, Mexico Single-effect absorption refrigeration hybridized with mechanical vapor compression in a vapor circuit is known as the absorption cycle with an integrated booster compressor. In this study, the compressor is located between the evaporator and the absorber. This paper presents a numerical model of this cycle with ammonia-lithium nitrate solution as the working pair. It is based on UAÀDTlm models for separateregions of plate-type heat exchangers. The results are offered as a function of external circuit flow parameters. Different pressure ratios of the compressor were tested for a wide range of hot water driving e95  C), showing that low values are more beneficial. This cycle allows for working at lower driving temperatures than the single-effect cycle, with low electricity consumption. At the same driving temperature, the capacity is augmented with an increased compressor pressure ratio, thus allowing for demand matching of the cooling. This cycle, operating with hot water at 67 C with a pressure ratio of 2.0, has the capacity of a single-effect absorption cycle at 94 C. The electrical COPwas found to be higher than that in an ammonia vapor compression cycle for comprehensiveworking conditions.
Ó 2010 Elsevier Ltd. All rights reserved.
of NH3eLiNO3 has been studied for a series of concentrations andtemperatures ranging from 50 to 150 C [9]. These materials were The single-effect absorption cycle has been widely studied for found to be suitable for the construction of absorption heat pump a long time [1e3]. H2OeLiBr and NH3eH2O are the best-known process equipment for this working mixture.
working pairs for single-effect absorption cycles [1]. H2OeLiBr The potential of the absorption cycle for low-temperature waste is commonly employed for air-conditioning purposes due to heat recovery has been recognized for a long time. Its application to its overall favorable performance. For industrial refrigeration, solar cooling makes this technology attractive due to the syn- NH3eH2O solution is the most common working fluid.
chronicity between solar thermal energy and air-conditioning NH3eLiNO3 is a promising alternative that has been studied by demand. Single-effect absorption chillers can operate with relatively Refs. [4e6], among others. Single-effect absorption using this low driving temperatures, compatible with flat plate collectors, but solution offers slightly higher coefficients of performance (COP) not lower than around 70 C for air-conditioning; this minimum is and a lower investment cost than NH3eH2O, as it does not higher for hot days and low-temperature chilled water [10]. Solar require a rectification tower [7,8]. Lower temperatures for cooling using flat plate collectors would profit from a lower demand producing cooling were reported in Ref. [8]. Dealing with trans- on the temperature of hot water, resulting in a higher collector port properties, at characteristic temperatures and concentra- efficiency. The economical benefits would include a lower investment tions of ammonia, NH3eLiNO3 shows a value of thermal in the solar collectors and storage tanks and a higher overall efficiency, conductivity on the order of twice that of NH3eH2O, and a higher especially on cloudy days and in the morning and evening, when solar viscosity, roughly three times higher than that of NH3eH2O.
radiation is low. Being able to operate efficiently with a low driving NH3eLiNO3 also presents a mass diffusivity on the order of 1% temperature is of paramount importance for the possibility of higher. The corrosion of carbon and stainless steel with solutions recovering very low-temperature residual heat. The single-effectabsorption cycle with an integrated booster compressor offers thispossibility, taking advantage of simple well-proven technologies. Thishybridization is integrated, as the compressor pumps the same * Corresponding author. Tel.: þ34 916246224; fax: þ34 916249430.
E-mail addresses: rventas@ing.uc3m.es (R. Ventas), azacaria@ipn.mx (A. Zacarías).
refrigerant used in the absorption cycle.
1359-4311/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.applthermaleng.2010.02.022

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