Viscosity-prediction models of ammonia water nanofluids based on various dispersion types

This paper intends to apply the techniques that nano-particles enhance the heat and mass transfer to the ammonia water absorption refrigeration. Three types of nanofluids were obtained by adding the mixture of carbon black with emulsifier OP-10, ZnFe2O4 with sodium dodecyl benzene sulfonate (SDBS), and Fe2O3 with SDBS to the ammonia water solution, respectively. A series of experiments was performed to investigate the viscosities of the three kinds of nanofluids. The results show that, the content of surfactant and nano-particles, the interaction between surfactant and nano-particles, and the dispersion type are the key parameters that affect the viscosity of ammonia water nanofluid. Based on Einstein model and considering the solvation effect, two models to estimate the viscosity of ammonia water nanofluids were proposed in this paper. One is to analyze monolayer adsorption without considering the decrease of “free” surfactant content in ammonia water basefluid. The other model is to analyze electric double layer (EDL) adsorption, while taking the change of “free” surfactant content in ammonia water basefluid into account. The presented models and other theoretical models have been compared with experimental data. The comparison results show the presented models, in general, have higher accuracies and precisions.

Graphical abstractSummary: Based on Einstein model and considering the solvation effect, by analyzing the dispersion types and taking the change of surfactant content in basefluid into account, two models to estimate the viscosity of ammonia water nanofluids were proposed. The experimental results show that both viscosity-prediction models provide more accurate estimate compared to some other existing models.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The dispersion types affect the viscosity of ammonia-water nanofluid. ► The adsorption of surfactant affects the viscosity of ammonia-water basefluid. ► The models based on various dispersion types provide good estimates on viscosity.