11 PCM-Metal Foam Composite Systems for Solar Energy Storage
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11.3.5 Overall Size and Aspect Ratio
The overall dimensions of the storage unit has to be designed such that the energy
charging and discharging can be completed during the required time period. However, if the storage unit is too small, a large number of units will be necessary thus
increasing the overall cost. Aspect ratio also is an important parameter as it defines
the farthest distance of PCM from the heat transfer surface. A broad and shallow
design where the wall opposite to the heat transfer surface is relatively near is better
as energy can be transported to the entire PCM in less time.
11.4 Previous Studies on PCM-Metal Foam Hybrid
Systems
11.4.1 Experimental Studies
A number of experimental investigations have been performed to study the effect
of aluminum, copper and nickel foam on the heat transfer characteristics of PCM
based storage systems (Siahpush et al. 2008; Xiao et al. 2013, 2014; Zhao et al. 2010;
Chen et al. 2014; Zhu et al. 2018; Zheng et al. 2018). The main findings from the
experimental studies can be summarized as follows.
• Comparison of pure PCM systems and metal foam-PCM systems show that use
of metal foam drastically improves the heat transfer characteristics of the system
and the effective thermal conductivity of the composite structure is many times
higher than that of the PCM.
• Metal foam structure plays an important role in determining the system characteristics. Lower porosity leads due to higher heat conduction whereas higher porosity
leads to higher convection and energy storage capacity.
• Foam material has a strong influence on the heat transfer.
11.4.2 Numerical Modelling
Numerical modelling of metal foam-PCM composite systems mainly follows two
approaches: (a) Volume averaged modelling and (b) Pore-scale modelling.
Volume averaged models. Volume averaged models (Mesalhy et al. 2005; Tian
and Zhao 2011; Srivatsa et al. 2014; Zhang et al. 2017; Yang et al. 2018; Sundarram
and Li 2014; Kumar and Saha 2018) assume that the entire composite structure is
a porous medium and formulates the governing equations for energy balance for
this porous medium. Two different approaches are taken. Basic models assume that
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11.3.5 Overall Size and Aspect Ratio
The overall dimensions of the storage unit has to be designed such that the energy
charging and discharging can be completed during the required time period. However, if the storage unit is too small, a large number of units will be necessary thus
increasing the overall cost. Aspect ratio also is an important parameter as it defines
the farthest distance of PCM from the heat transfer surface. A broad and shallow
design where the wall opposite to the heat transfer surface is relatively near is better
as energy can be transported to the entire PCM in less time.
11.4 Previous Studies on PCM-Metal Foam Hybrid
Systems
11.4.1 Experimental Studies
A number of experimental investigations have been performed to study the effect
of aluminum, copper and nickel foam on the heat transfer characteristics of PCM
based storage systems (Siahpush et al. 2008; Xiao et al. 2013, 2014; Zhao et al. 2010;
Chen et al. 2014; Zhu et al. 2018; Zheng et al. 2018). The main findings from the
experimental studies can be summarized as follows.
• Comparison of pure PCM systems and metal foam-PCM systems show that use
of metal foam drastically improves the heat transfer characteristics of the system
and the effective thermal conductivity of the composite structure is many times
higher than that of the PCM.
• Metal foam structure plays an important role in determining the system characteristics. Lower porosity leads due to higher heat conduction whereas higher porosity
leads to higher convection and energy storage capacity.
• Foam material has a strong influence on the heat transfer.
11.4.2 Numerical Modelling
Numerical modelling of metal foam-PCM composite systems mainly follows two
approaches: (a) Volume averaged modelling and (b) Pore-scale modelling.
Volume averaged models. Volume averaged models (Mesalhy et al. 2005; Tian
and Zhao 2011; Srivatsa et al. 2014; Zhang et al. 2017; Yang et al. 2018; Sundarram
and Li 2014; Kumar and Saha 2018) assume that the entire composite structure is
a porous medium and formulates the governing equations for energy balance for
this porous medium. Two different approaches are taken. Basic models assume that