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Abstract
Ammonia/lithium nitrate and ammonia/(lithium nitrate + water) have been proposed as suitable working pairs for absorption refrigeration systems driven by low-temperature heat sources. The use of water in the absorbent of the ternary mixture reduces the viscosity of the binary mixture and increases the affinity between the refrigerant (ammonia) and the absorbent, which should have a positive effect on the absorption process. In this paper, a brief review on the thermodynamic and transport properties available in the open literature for NH3/LiNO3 and NH3/(LiNO3 + H2O) mixtures is presented, and the most significant results of an experimental characterization of absorption and desorption processes taking place in plate heat exchangers are discussed.
NOMENCLATURE
| A | = | projected heat transfer area, m2 |
| Cp | = | isobaric heat capacity, kJ kg−1 K−1 |
| e | = | plate thickness, m |
| F | = | mass absorption flux, kg m−2 s−1 |
| h | = | heat transfer coefficient, kW m−1 K−1 |
| H | = | specific enthalpy, kJ kg−1 |
| LMTD | = | logarithmic mean temperature difference, °C |
| m | = | mass flow rate, kg s−1 |
| ms | = | solution mass flux, kg s−1 m−2 |
| Nu | = | Nusselt number |
| P | = | pressure, kPa |
| Pr | = | Prandtl number |
| Q | = | thermal load, kW |
| Re | = | Reynolds number |
| T | = | temperature, °C |
| U | = | overall heat transfer coefficient, kW m−1 K−1 |
| w | = | liquid mass fraction of ammonia, kgNH3.kg−1NH3/LiNO3 |
| w1 | = | liquid mass fraction of ammonia, kgNH3.kg−1NH3/LiNO3+H2O |
| w3 | = | liquid mass fraction of water in the absorbent, kg H2O.kg−1NH3/LiNO3 |
| x | = | vapor quality |
| xcris | = | crystallization concentration |
| y | = | vapor mass fraction of ammonia, kg kg−1 |
| z | = | global mass fraction of ammonia, kg kg−1 |
Greek Symbols
| λ | = | thermal conductivity, kW m−1 K−1 |
| μ | = | dynamic viscosity, Pa-s |
| ρ | = | density, kg m−3 |
Subscripts
| AB | = | absorber |
| C | = | cold fluid |
| G | = | global (vapor/liquid phases) |
| H | = | hot fluid |
| in | = | absorber inlet |
| L | = | liquid phase |
| NH3 | = | ammonia |
| out | = | absorber outlet |
| sol | = | solution |
| surfaces | = | wall surface |
| V | = | vapor phase |
Additional information
Funding
Notes on contributors
Carlos Amaris
Carlos Amaris is a Ph.D. student in the research group of Applied Thermal Engineering–CREVER, Department of Mechanical Engineering, at Rovira i Virgili University, Tarragona (Spain). He received his master's degree from the same university in 2009 and bachelor's degree in mechanical engineering from the Universidad Autonoma del Caribe, Colombia, in 2008. Currently, he is working on the experimental intensification of the absorption process into ammonia-based working fluids for absorption refrigerationsystems.
Mahmoud Bourouis
Mahmoud Bourouis is a professor at Rovira i Virgili University (URV), Tarragona (Spain). Prior to joining URV, he worked at CNRS France as a postdoctoral researcher. He received his Ph.D. in chemical engineering from the INP Toulouse (France) in 1992. His research interests include thermal cooling systems, heat and mass intensification, advanced cycles and new working fluids for absorption heat pumps and refrigeration systems, and air-conditioning in buildings. He is the co-author of numerous papers published in indexed journals and conference proceedings and has participated in numerous national and international projects.
Manel Vallès
Manel Vallès studied chemistry at the University Rovira i Virgili of Tarragona, where he received his Ph.D. in chemical engineering in 2000. In 2011 he became head of the Mechanical Engineering Department at the University Rovira i Virgili. His research topics are heat and mass transfer, absorption heat pumps, solar cooling, heat exchangers and absorption components design.
Daniel Salavera
Daniel Salavera is an assistant professor at Rovira i Virgili University, Tarragona (Spain). He received his Ph.D. in chemical engineering from the same university in 2005 and bachelor's degree in chemistry from the Universidad de Zaragoza, Spain, in 2001. His research interests include measurement and modeling of thermodynamic and transport properties of working fluids for absorption heat pumps and refrigeration systems. He is the co-author of several papers published in indexed journals and conference proceedings and has participated in national and international projects.
Alberto Coronas
Alberto Coronas is a full professor of thermal engineering in the Department of Mechanical Engineering at Rovira i Virgili University, Tarragona (Spain). He received his Ph.D. in physics from the University of Barcelona (Spain) in 1994. He is the head of the Research Group on Applied Thermal Engineering (CREVER) at Rovira i Virgili University. His research activity covers the field of absorption technology for industrial refrigeration and air-conditioning applications, energy management, heat transfer, and thermophysical properties of new working fluids for absorption heat pumps and refrigeration systems. He has supervised around 20 Ph.D. theses and published more than 150 refereed technical papers in journals and conference proceedings and has participated in many national and international projects.