On the recirculation of ammonia-lithium nitrate in adiabatic absorbers for chillers

• Published in: Applied thermal engineering Vol. 30; no. 17; pp. 2770 - 2777
• Main Authors: Ventas, R., Lecuona, A., Legrand, M., Rodríguez-Hidalgo, M.C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-12-2010; Elsevier
• Subjects: Absorption chiller; Adiabatic absorber; Adiabatic flow; Ammonia-lithium nitrate; Applied sciences; Chillers; Circuits; Devices using thermal energy; Energy; Energy. Thermal use of fuels; Engineering Sciences; Exact sciences and technology; Heat exchangers; Heat exchangers (included heat transformers, condensers, cooling towers); Heat transfer; Mass flow; Mass flow recirculation; Mathematical analysis; Mathematical models; Mechanics; Nitrates; Physics; Theoretical studies. Data and constants. Metering; Thermics; Ammonia-lithium nitrate; Mass flow recirculation; Adiabatic absorber; Absorption chiller; Cooling; Recirculation; Modeling; Ammonia; Subcooling; Mass flow rate; Heat exchanger; Lithium nitrate; Performance; Mass flow; Heat transfer; mass flow recirculation; ammonia-lithium nitrate; adiabatic absorber
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2010.08.001

This paper presents a numerical model of single-effect absorption cycles with ammonia-lithium nitrate solution as the working pair and incorporating an adiabatic absorber. It is based on
UA-Δ
T
lm models for separate regions of plate-type heat exchangers and it assumes an approach factor to adiabatic equilibrium. The results are offered as a function of external temperatures. A loop circuit with a heat exchanger upstream the absorber produces subcooling for facilitating absorption process. The effect of the mass flow rate recirculated through the absorber is studied. Results show a diminishing return effect. The value at which the recirculation mass flow yields a reasonable performance is between 4 and 6 times the solution mass flow. With a heat transfer area 6 times smaller than with a conventional diabatic shell-and-tube type absorber, the adiabatic absorber configured with a plate heat exchanger yields a 2% smaller maximum COP and a 15–20% smaller cooling power.