Preparation And Application-Related Simulation Study Of Novel Polymer-Based Form-Stable Phase Change Materials

Phase change materials (PCM) absorb and release considerable latent heat when they change their phase state over a narrow range of temperature. In recent years, researchers around the world performed comprehensive studies on inorganic, organic and inorganic-organic composite PCM. From the phase transition temperature and latent heat point of view, low-temperature solid-liquid PCM have a better prospect for industrialization. To avoid the leakage of liquid PCM during applications, containers designed specifically or packaging materials are necessary for the encapsulation of solid-liquid PCM. Related studies of various polymer-based form-stable phase change materials (FSPCM), in which different polymer materials and paraffin wax-type solid-liquid PCM are used as bulk materials and operation materials, respectively, are a hot spot.In this paper, a novel polymer-based FSPCM, which comprises micro-encapsulated PCM (MEPCM) as the latent heat storage medium and wood flour/high density polyethylene composite as the matrix, was put forward and prepared by blending and compression molding method for potential latent heat thermal energy storage applications. Different inorganic materials with high heat conductivity were added to improve the thermal conductivity of prepared polymer-based FSPCM. The main research efforts devoted to the preparation and application studies of novel polymer-based FSPCM are summarized as follows.①Preparation and characterization of novel polymer-based FSPCMFifteen novel polymer-based FSPCM plates were prepared, and their microscopic pattern, thermo-physical properties, thermal stability and mechanical properties were characterized by using scanning electronic microscope (SEM), differential scanning calorimeter (DSC), thermogravimetic analysis (TGA), thermal conductivity measuring apparatus, universal material testing machine and hardness tester.SEM images reveal that the prepared FSPCM plates have homogeneous constitution and most of MEPCM particles in them were undamaged. Therefore, it is feasible to prepare novel polymer-based FSPCM by blending and compression molding method.DSC was used to test the phase change temperatures, latent heats and specific heats of MEPCM and FSPCM plates. DSC results show that: 1) novel polymer-based FSPCM have identical phase change temperatures with MEPCM and their latent heats linearly increase with the increase of weight fraction of MEPCM. The FSPCM plates with about 25wt% MEPCM have the latent heat of about 28kJkg^-1. Thermal cycling test indicates the form-stable PCMs have good thermal stability although it was subjected to 100 melt-freeze cycles.TGA results show that prepared FSPCM plates have good thermal stability.The results of heat conductivity test indicate that micro mist graphite, iron wire and their compounds can be used to improve novel FSPCM plates' thermal conduction performance. Different weight fractions of these materials with high heat conductivities lead to different improvement effects.The results of mechanical property test show that the flexural strength, flexural modulus and surface hardness of prepared FSPCM plates are above 10 MPa, 600 MPa and 60HD. It can be said that the novel FSPCM plates have goodish mechanical properties for practical applications such as energy efficient building materials.②A mathematic model, based on building heat balance and features of phase change heat transfer, was developed to describe the hourly temperature field of a typical room. A special simulation program was established in Matlab6.5 according to finite difference method. The program was verified by theoretical, contrastive and experimental methods, respectively. By the simulation program, the application effects of using prepared FSPCM as building envelope materials (e.g. floor, wall and ceiling boards) can be comprehensively studied with parameterization.③The effects of room temperature control, energy-saving and cost-reduction of applying novel FSPCM plates as the thermal storage layer (TSL) of an electric floor heating system (EFHS) were analyzed by the above-mentioned simulation program, taking into various factors (especially the operation mode of the EFHS and the thickness of prepared FSPCM plates). Simulation results show that different operation modes of the EFHS and thicknesses of prepared FSPCM plates lead to different application effects for the same other parameters such as weather conditions, typical room's orientation, thermal characteristics, FSPCM plates' thermophysical properties.④Two optimization methods of FSPCM plates' thermophysical properties were presented. One is the steady-state calculation method and the other the transient-state analogue method. By the two methods, preferable ranges of thermophysical properties (phase change temperature, latent heat, phase change radius and heat conductivity) of FSPCM plates used as the TSL were determined. These two optimization methods can be used to provide guidances for the R&D of MEPCM, the recipe modification of novel FSPCM plates and design-construct of EFHS.⑤Industrialization prospect analysis of novel polymer-based FSPCMs Novel polymer-based FSPCM plates' bulk materials are reproducible and/or inexpensive. The preparation method is feasible. And novel polymer-based FSPCM have widespread potential applications. Therefore, it is possible and worth to come true the industrialization of the novel polymer-based FSPCM. To realize that, some key problems such as developing MEPCM with different phase change temperatures, high phase change enthalpies, good thermal cycling and thermal stabilities, optimizing the recipes and preparation technologies must be settled.