Modeling and experimental verification of the enhancement of TiO2 nanofluid on ammonia falling film absorption process

The energy efficiency of absorption refrigeration system is restricted by the absorption rate of absorber. Nano -fluid is widespread applied to enhance the absorber performance, because the boundary thickness is reduced by the random Brownie motion of the contained nanoparticles. To describe the enhancement of nanoparticles simply and accurately, a mathematical model is built based on the ammonia solution falling film absorber. The momentum exchange and properties modifications caused by nanoparticles are considered in the governing equation. Meanwhile, an experimental facility of ammonia absorption refrigeration system is established, and the nanofluid is served as a circulating solution. The nanofluid is comprised of TiO2 nanoparticles and ammonia solution. Compared with the measurement of experiment, the ammonia absorbed rate of absorber predicted by the mathematical model has a maximum relative error of 8.9%. Furthermore, the absorption effects of the falling film absorber in different inlet conditions are analyzed. The result indicates the enhancement of nanoparticles is more significant with lower mass flow rate or poorer ammonia mass fraction.

Automated summary

In this study, a mathematical model was established based on the ammonia solution falling film absorber to describe the enhancement of nanoparticles in an absorption refrigeration system. The model considered the momentum exchange and properties modifications caused by nanoparticles. Experimental results showed that the predicted absorption rate of the absorber had a maximum relative error of 8.9% compared to the measurement. It was also found that the enhancement of nanoparticles was more significant with lower mass flow rate or poorer ammonia mass fraction.