Phase Change Material Particles and Their Application in Heat Transfer Fluids - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 470

Fig. 17 a Pictures of water
in FC-72 nanoemulsion fluids
(Bottle A) and pure FC-72
(Bottle B). Liquids in both
bottles are transparent. The
Tyndall effect can be
observed only in Bottle
A when a laser beam is passed
through Bottles A and
B. b Schematic diagram of a
water nanodroplet dispersed
in 3 M's FC-72 thermal fluid.
A micelle of amphiphiles
surrounds the nanodroplet,
with the polar head
interacting with water [ 15 ]

(a)

(b)

Water

FC-72

with high aspect ratio of length to radius, which leads to a higher thermal con-
ductivity enhancement in nanoemulsion fluids than the spherical droplets.

5.2.3 Phase Change Behavior in Water in FC-72 Nanoemulsion Fluids

The heat capacity of nanoemulsion fluid can be enhanced through two different
mechanisms: one is due to the high specific heat of the dispersed phase; the other is
due to the latent heat of the dispersed PCMs. The latter one, i.e., use of PCMs, is
much more efficient for the heat capacity enhancement. In water in FC-72 nano-
emulsion fluids, the fluid's heat capacity can be increased by the high specific heat
of water (i.e., C water = 4.2 J/g C, C FC 72 = 1.1 J/g C) or the latent heat of water
(DH ¼ 334 J = g Þ , depending on the operating temperature of the fluids [ 94 ].