Effect of nanoparticles on heat capacity of nanofluids based on molten salts as PCM for thermal energy storage

Table 2 Specific heat of NaNO₃-KNO₃ (60:40) mixture and nanofluids obtained with different nanoparticles

Material	Nanoparticle concentration wt.%	Specific heat (solid phase; kJ/kg·K)	Enhancement (solid phase; %)	Specific heat (liquid phase; kJ/kg·K)	Enhancement (liquid phase; %)
Base salt mixture	-	1.604	-	1.648	-
Base salt + SiO₂	0.5	1.341	−16.4	1.329	−19.3
	1.0	1.843	14.9	1.661	0.8
	1.5	1.635	2.0	1.624	−1.4
Base salt + Al₂O₃	0.5	1.526	−4.8	1.522	−7.6
	1.0	1.923	19.9	1.745	5.9
	1.5	1.550	−3.3	1.590	−3.5
Base salt + TiO₂	0.5	1.372	−14.4	1.390	−15.6
	1.0	1.508	−6.0	1.544	−6.3
	1.5	1.432	−10.7	1.454	−11.8
Base salt + SiO₂-Al₂O₃	0.5	1.572	−2.0	1.525	−7.5
	1.0	2.529	57.7	2.018	22.5
	1.5	2.162	34.8	1.673	1.5