Page 101 - Polymer-based Nanocomposites for Energy and Environmental Applications

Nanoclay and polymer-based nanocomposites: Materials for energy efficiency 77

Table 3.1 Required properties for a material to be used as PCM [7,8]
Thermodynamic l Melting temperature in the desired operating temperature range
properties l High phase-change latent heat per unit volume
l High latent heat capacity value
l High thermal conductivity
l Small volume change on phase transformation and small vapor
pressure at operating temperature to reduce the containment
problem
l Congruent melting of the phase-change material
l High density
Kinetic properties l No supercooling
l No subcooling
l No phase segregation
l Good nucleating properties
Chemical properties l Chemically stable after a large number of freeze/melt cycles
Noncorrosive
l
Nontoxic, nonflammable, and no explosive material
l
Compatible with container material
l
Economic l Commercially available
properties
l Cost-effective

Phase change materials

Organics compounds Inorganic compounds Eutectics

Paraffin Nonparaffin Salt hydrates Organic-organic

Fatty acids Metallic Inorganic-organic

Esters Inorganic-inorganic

Alcohols

Fig. 3.1 Classification of PCMs.

little or no supercooling properties with melt-freeze cycles and had a high latent heat
capacity and a good nucleation rate [6], making them well suited. The mean problems
of the organic PCMs are the low thermal conductivity, flammability, and large volu-
metric change during the phase transition process [10]. The second class named inor-
ganic PCMs generally includes salt hydrate and metallic [11]. They have attracted