Experimental Study on Enhanced Falling Film Absorption Process Using H₂O/LiBr Nanofluids

Absorption air conditioning system could be driven by low grade energy, such as solar energy and industrial exhaust heat, for the purposes of energy conservation and emission reduction. Its development is limited by its huge volume and high initial investment. The nanofluids, which possess the superior thermophysical properties, exhibit a great potential in enhancing heat and mass transfer performance. In this paper, nanofluids of H₂O/LiBr with Fe₃O₄ nanoparticles were introduced into absorption air conditioning system. The effects of some parameters, such as the flow rate of H₂O/LiBr nanofluids, nanoparticle size and mass fraction, on the falling film absorption were investigated. The H₂O/LiBr nanofluids with Fe₃O₄ nanoparticle mass fractions of 0.01 wt%, 0.05 wt% and 0.1 wt%, and nanoparticle size of 20 nm, 50 nm and 100 nm were tested by experiment. The results imply that the water vapour absorption rate could be improved by adding nanoparticles to H₂O/LiBr solution. The smaller the nanoparticle size, the greater enhancement of the heat and mass transfer performance. The absorption enhancement ratio increases sharply at first by increasing the nanoparticle mass fraction within a range of relatively low mass fraction, and then exhibits a slow growing even reducing trends with increasing the mass fraction further. For Fe₃O₄ nanoparticle mass fraction of 0.05wt% and nanoparticle size of 20nm, the maximum mass transfer enhancement ratio is achieved about 2.28 at the flow rate of 100 L·h⁻¹.