2.13 Phase Change Materials
35
Advantages
1. High volumetric latent heat storage capacity;
2. Low cost and easy availability;
3. Sharp melting point;
4. High thermal conductivity;
5. High heat of fusion;
6. Low volume change and
7. Non-flammability.
Disadvantages
1. Super cooling is a major problem in solid–liquid transition and
2. Requirement to use nucleating agents which become ineffective after repeated
cycling.
2.13.1.3 Eutectics
Eutectic PCM are mixtures of two or more chemicals which, when mixed in a particular ratio, have a freezing/melting point below or above the freezing temperature of
water (0 °C or 32 °F) and offer a thermal energy storage facility between –114 °C
(–173 °F) and +164 °C (327 °F). These are mixtures of organic–organic, organic–
inorganic and inorganic–inorganic compounds. The applications of eutectics date
back to the late eighteenth century. As the separation and the life expectancy of these
mixtures were unpredictable, their widespread usage was limited. The advantages
and disadvantages of using eutectic PCM are described below.
Advantages
1. Sharp melting point similar to a pure substance and
2. Higher volumetric storage density as compared to organic compounds.
Disadvantages
1. Limited availability of data on thermo-physical properties and
2. These materials are very new to thermal storage applications.
Out of the above classes of PCM discussed, the most commonly used PCM are salt
hydrates, fatty acids and paraffins. Recently, ionic liquids were investigated as novel
PCM. Bugaje [163] conducted experiments on methods for enhancing the thermal
response of paraffin wax heat storage tubes by the incorporation of aluminium fins
and star structures. The conclusion was that internal fins performed much better than
star matrices, reducing the loading time on the order of 2.2 and the unloading time
on the order of 4.2. Zalba et al. [164] used paraffin PCM and developed an empirical
model that measured the performance of PCM.
35
Advantages
1. High volumetric latent heat storage capacity;
2. Low cost and easy availability;
3. Sharp melting point;
4. High thermal conductivity;
5. High heat of fusion;
6. Low volume change and
7. Non-flammability.
Disadvantages
1. Super cooling is a major problem in solid–liquid transition and
2. Requirement to use nucleating agents which become ineffective after repeated
cycling.
2.13.1.3 Eutectics
Eutectic PCM are mixtures of two or more chemicals which, when mixed in a particular ratio, have a freezing/melting point below or above the freezing temperature of
water (0 °C or 32 °F) and offer a thermal energy storage facility between –114 °C
(–173 °F) and +164 °C (327 °F). These are mixtures of organic–organic, organic–
inorganic and inorganic–inorganic compounds. The applications of eutectics date
back to the late eighteenth century. As the separation and the life expectancy of these
mixtures were unpredictable, their widespread usage was limited. The advantages
and disadvantages of using eutectic PCM are described below.
Advantages
1. Sharp melting point similar to a pure substance and
2. Higher volumetric storage density as compared to organic compounds.
Disadvantages
1. Limited availability of data on thermo-physical properties and
2. These materials are very new to thermal storage applications.
Out of the above classes of PCM discussed, the most commonly used PCM are salt
hydrates, fatty acids and paraffins. Recently, ionic liquids were investigated as novel
PCM. Bugaje [163] conducted experiments on methods for enhancing the thermal
response of paraffin wax heat storage tubes by the incorporation of aluminium fins
and star structures. The conclusion was that internal fins performed much better than
star matrices, reducing the loading time on the order of 2.2 and the unloading time
on the order of 4.2. Zalba et al. [164] used paraffin PCM and developed an empirical
model that measured the performance of PCM.