The constrained melting of nano-enhanced phase change materials (NePCM) in a horizontal cylindrical capsule was investigated via the utilization of thermochromic liquid crystal (TLC) technique for tracking the invisible phase interfaces. A parametric study was carried out by varying both the loading of NePCM (i.e., 0 wt %, 1 wt %, and 3 wt %) and the wall superheat (at 10 °C and 30 °C), leading to a total of six cases. Numerical simulations, based on the enthalpy-porosity method, were also performed to reveal the evolutions of temperature and convective flow fields during melting. It was first shown that the numerically predicted melting front evolutions are in good agreement with the TLC imaging results. A comparison among the six cases indicated that there is a similar melting pattern that heat conduction dominates the initial stage of melting and natural convection then takes over to play a more important role when melting proceeds. With the TLC-assisted reconstruction of the melting fronts, the instantaneous melting and heat storage rates were estimated, and melting was clearly found to slow down with increasing the loading of NePCM, as a result of the dramatically increased viscosity that deteriorates the contribution of natural convection to melting heat transfer.