Cold thermal energy storage for milk chilling: A numerical and experimental study

One of the main challenges in small holding dairy production systems is the commencement of cold-chain from the point of milk production. Such systems often rely on pooled milk in a supply chain, with the chilling operations being initiated once substantial quantities of milk (> 500 L) are collected. Hence, there is a need to develop an energy efficient and passive thermal storage device for chilling of small volumes of milk. The present study explored a novel approach of developing the phase change materials (PCM) encapsulated inside a spherical module as an immersion cooling device to chill a pool of milk (5 L) held in a vessel. The application of TiO2 nanoparticles at (0.05-1.00% by wt.) for developing nanoparticle enhanced water based PCM with improved energy storage was also explored. Transient energy exchange and phase-transition of the PCMs during the milk chilling process was numerically simulated using enthalpy-porosity and volume of fluid model of computational fluid dynamics (CFD). The CFD simulated results were validated through the experimental observations and the flow visualization of the temperature distribution and melting fronts clearly affirmed the rapidity of energy exchange due to the addition of nanoparticles into the PCM.