Experimental study of an ammonia–water bubble absorber using a plate heat exchanger for absorption refrigeration machines

• Published in: Applied thermal engineering Vol. 29; no. 5; pp. 1005 - 1011
• Main Authors: Cerezo, Jesús, Bourouis, Mahmoud, Vallès, Manel, Coronas, Alberto, Best, Roberto
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.04.2009; Elsevier
• Subjects: Absorber; Absorption refrigeration; Air pollution caused by fuel industries; Ammonia–water; Applied sciences; Bubble; Devices using thermal energy; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Heat exchangers (included heat transformers, condensers, cooling towers); Heat transfer; Metering. Control; Plate heat exchanger; Theoretical studies. Data and constants. Metering; Absorption refrigeration; Bubble; Plate heat exchanger; Ammonia–water; Absorber; Energy consumption; Compression; Ammonia-water; Modeling; Machine; Heat exchanger; Food; Low temperature; Flow rate; Cooling; Absorption réfrigération; Thermal load; Heat transfer coefficient; Experimental study; Mass transfer; Operating conditions; Ammonia; Renewable energy; Primary energy; Air pollution; Performance; Physical Sciences
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2008.05.012

The development of absorption chillers activated by renewable heat sources has increased due mainly to the increase in primary energy consumption that causes problems such as greenhouse gases and air pollution among others. These machines, which could be a good substitute for compression systems, could be used in the residential and food sectors which require a great variety of refrigeration conditions. Nevertheless, the low efficiency of these machines makes it necessary to enhance heat and mass transfer processes in the critical components, mainly the absorber, in order to reduce their large size. This study used ammonia–water as the working fluid to look at how absorption takes place in a plate heat exchanger operating under typical conditions of absorption chillers, driven by low temperature heat sources. Experiments were carried out using a corrugated plate heat exchanger model NB51, with three channels, where ammonia vapor was injected in bubble mode into the solution in the central channel. The results achieved for the absorption flux were in the range of 0.0025–0.0063 kg m −2 s −1, the solution heat transfer coefficient varied between 2.7 and 5.4 kW m −2 K −1, the absorber thermal load from 0.5 to 1.3 kW. In addition, the effect of the absorber operating conditions on the most significant efficiency parameters was analyzed. The increase in pressure, solution and cooling flow rates positively affect the absorber performance, on the other hand an increase in the concentration, cooling, and solution temperature negatively affects the absorber performance.