Simulation and Experimental Study on Thermal Conductivity of EMIMDEP+H2O+SWCNTs Nanofluids as a New Working Pairs

C Li and ZC Zhao and XD Zhang and TY Li, INTERNATIONAL JOURNAL OF THERMOPHYSICS, 39, 41 (2018).

DOI: 10.1007/s10765-018-2359-2

In this paper, the single-wall carbon nanotubes (SWCNTs) were dispersed into ionic liquid, 1-ethyl-3-methylimidazolium diethylphosphate (EMIMDEP), and its aqueous solution EMIMDEP(1)+H2O(2) to enhance the thermal conductivity of base liquids, which will be the promising working pairs for absorption heat pumps and refrigerators. The enhancement effects on thermal conductivity were studied by experiment and molecular dynamic simulation (MD) methods. The thermal conductivities of EMIMDEP+SWCNTs (INF) and EMIMDEP(1)+H2O(2)+SWCNT (SNF) both with SWCNT mass fraction of 0.5, 1, and 2 (wt%) were measured by transient hot-wire method. The results indicate that the enhancement ratio of thermal conductivity of INF, and SNF can approach 1.30 when SWCNT is 2 (wt%). Moreover, SWCNTs has a higher enhancement ratio than multi-wall carbon nanotubes (MWCNTs). Density and thermal conductivity of EMIMDEP, EMIMDEP(1)+H2O(2), INF and SNF systems, together with self-diffusion coefficients of EMIM(+), DEP(-), EMIMDEP and water in solution EMIMDEP(1) +H2O(2), were investigated by MD simulations. The results indicate that the maximum relative error between the simulated and experimental densities is about 2%, and the simulated self-diffusion coefficient of EMIMDEP is in the order of magnitude of 10-11 m(2).s(-1). The average relative deviation for the simulated thermal conductivity of EMIMDEP(1)+H2O(2), INF and SNF from experimental ones are 23.57%, 5%, and 5%, respectively. In addition, the contributions of kinetic energy, potential energy, and virial and partial enthalpy terms to thermal conductivity were also calculated. The results indicate that virial term's contribution to thermal conductivity is the maximum, which accounts for 75% to 80% of total thermal conductivity.

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