**6. Conclusions**

The 3D CFD simulation model was developed for shell-and-tube thermal storage system using FLUENT/ANSYS. For the validation purpose, the results from the numerical model were compared with the experimental results of Lacroix [26]. The results show that a considerable agreement between the numerical and experimental results. Therefore, the results demonstrate that the developed CFD model accurately describes processes taking place in the experimental test rig and therefore can be used with confidence for further transient heat transfer simulations in the shelland-tube latent thermal storage unit. 3D CFD simulations were performed for a range of the HTF inlet temperature values and its mass flow rate. Thereby, the results were used to derive Nusselt number correlations as a function of Stefan, Rayleigh and Fourier numbers to take into account the effect of all design and operational conditions. The Nusselt number for the system with the pure PCM was found to be (*R*<sup>2</sup> <sup>¼</sup> <sup>0</sup>*:*8524)

$$Nu = 2.9883 \ (\text{Ste})^{0.0758} (Fo)^{-0.095} (Ra)^{0.0759}$$

The total melting time of the PCM can be estimated by (R2 = 0.966)

$$t\_m = \frac{\rho D}{1.056 \overline{h}} \left[ \frac{c\_p \left( T\_m - T\_{\text{initial}} \right) + \lambda\_{pcm}}{\left( T\_{\text{inlet}} - T\_m \right)} \right]$$

### **Nomenclature**


*CFD Model of Shell-and-Tube Latent Heat Thermal Storage Unit Using Paraffin as a PCM DOI: http://dx.doi.org/10.5772/intechopen.95847*


The overall dissipation rate
