An experimental and numerical investigation of latent heat storage unit using form-stable vinyl silane graft copolymer

An experimental and theoretical investigation is undertaken to examine the use of vinyl silane graft copolymer for high capacity thermal energy storage systems. Crosslinked vinyl silane graft copolymer is a form-stable phase-change material, i.e., does not change from solid to liquid during phase transition, and therefore permits direct contact with working fluid without the need of encapsulation. In addition, this material does not corrode in various commonly used working fluids.; This material has not been considered previously for thermal storage application in packed bed configuration and the effects of thermal cycling in different working fluids on its properties has not been investigated. The objectives of the present study are three-fold. Firstly, the thermophysical properties of the material are evaluated and aging effects are determined. Secondly, the experimental and mathematical modeling of the thermal storage system using this material is conducted to demonstrate proof-of-concept and provide charging and discharging characteristics. Lastly, an optimization of the system size and operating conditions is performed based on maximizing either the thermodynamic efficiency or minimizing the operating cost.; Measurements of variation of specific heat with temperature are conducted for material prepared and crosslinked with water by a variety of techniques. The results indicate that the properties are independent of preparation methods as well as thermal cycling in water, steam, and tri-ethylene-glycol. Similarly, the form-stability characteristics are also not altered. Mathematical models of the storage system are developed for charging and discharging with a single-phase liquid and charging with a two-phase mixture. The prediction of the single-phase models are verified by experimental investigation on a laboratory-scale prototype using tri-ethylene glycol as the working fluid. Parametric studies of the system reveal the dependence of charging and discharging characteristics of the system on size and the operating flow and temperature conditions. In conjunction with optimization methods developed in the study, the single-phase one-dimensional mathematical model of the system is used to determine the optimal size and operating condition of the system for a given set of constraints.