Numerical Model of a Slurry PCM-Based Solar Thermal Collector

Flat-plate solar thermal collector is the most common device to convert solar energy into heat. This technology, which mostly adopts water-based fluids, has been widely investigated and improved since it was introduced, yet the exploitation of solar energy is limited by innate technological constraints. An interesting approach to overcome the limitations of these systems is based on the exploitation of the latent heat of fusion/solidification of the fluid-e.g., using a microencapsulated PCM suspended in a water fluid phase, also called slurry PCM. In this chapter, the numerical model of a PCM-based flat-plate solar thermal collector is presented and discussed. Starting from the well-known Hottel-Whillier equation, the physical-mathematical model of a water-based flat-plate solar is suitably modified to incorporate the phase change equations and to account for the different thermophysical properties of a non-Newtonian fluid, such as the slurry PCM. Examples of applications are also given, developing the simulation of the solar collector for different boundary conditions and showing the improved performance of the PCM-based technology in comparison with a conventional solar thermal collector.