*Subscripts*


*Evolutionary Design of Heat Exchangers in Thermal Energy Storage DOI: http://dx.doi.org/10.5772/intechopen.96300*

PCM Phase-Change Material SHS Sensible Heat Storage TES Thermal Energy Storage TSM Thermal Storage Material

**Nomenclatures and Abbreviations**

*m*\_ Mass flow rate [kg/s]

*T <sup>f</sup>* Final temperature [K] *Ti* Initial temperature [K] *Tm* Melting temperature [K]

*α* Thermal diffusivity [m2

Δ*T* Temperature difference [K]

*θ* Normalized temperature difference []

]

*Qst* Energy stored [J] *r* radial coordinate [m] Ra Rayleigh number [] Sv Svelteness [] *T* Temperature [K]

*d*, *D* Diameter [m] *H*, *h* Height [m]

*L* Length [m] *m* Mass [kg]

*t* time [s]

*Greek Symbols*

*Subscripts*

**260**

*V* Volume [m3]

*δ* Length [m]

*ε* Scale factor [] *ζ* Scale factor []

*ρ* Density [kg/m<sup>3</sup>

*τ* Timescale [s] *ϕ* Void fraction

*i* internal, inner *m* melting *max* maximum *o* outward *s* solid *st* stored *t* tube

*tf* thermal fluid 2D Two-dimensional 3D Three-dimensional HE Heat Exchanger LHS Latent Heat Storage

*avg* average *c* cylinder *e* external *f* fluid, fin *h* helical

*cp* Specific heat [Jkg<sup>1</sup> <sup>K</sup><sup>1</sup>

*Heat Transfer - Design, Experimentation and Applications*

*hsl* Latent heat of fusion [J/kg] *<sup>k</sup>* Thermal conductivity [W<sup>m</sup><sup>1</sup> <sup>K</sup><sup>1</sup>

*n* Number of tubes or Complexity degree []

]

/s]

]
