Phase change materials for thermal energy storage

A review of experimental/computational studies to enhance the thermal conductivity of phase change materials (PCM) that were conducted over many decades is presented. Thermal management of electronics for aeronautics and space exploration appears to be the original intended application, with later extension to storage of thermal energy for solar thermal applications. The present review will focus on studies that concern with positioning of fixed, stationary high conductivity inserts/structures. Copper, aluminum, nickel, stainless steel and carbon fiber in various forms (fins, honeycomb, wool, brush, etc.) were generally utilized as the materials of the thermal conductivity promoters. The reviewed research studies covered a variety of PCM, operating conditions, heat exchange and thermal energy storage arrangements. The energy storage vessels included isolated thermal storage units (rectangular boxes, cylindrical and annular tubes and spheres) and containers that transferred heat to a moving fluid medium passing through it. A few studies have focused on the marked role of flow regimes that are formed due to the presence of thermally unstable fluid layers that in turn give rise to greater convective mixing and thus expedited melting of PCM. In general, it can be stated that due to utilization of fixed high conductivity inserts/structures, the conducting pathways linking the hot and cold ends must be minimized.

Thermal conductivity enhancement of phase change materials for thermal energy storage: A review ☆

Recent developments in phase change materials for energy storage applications: A review

An overview of thermal energy storage systems

Thermal energy storage (TES) systems using phase change material (PCM) have been recognized as one of the most advanced energy technologies in enhancing the energy efficiency and sustainability of buildings. Now the research is focus on suitable method to incorporate PCMs with building. There are several methods to use phase change materials (PCMs) in thermal energy storage (TES) for different applications. Microencapsulation is one of the well known and advanced technologies for better utilization of PCMs with building parts, such as, wall, roof and floor besides, within the building materials. Phase change materials based microencapsulation for latent heat thermal storage (LHTS) systems for building application offers a challenging option to be employed as effective thermal energy storage and a retrieval device. Since the particular interest in using microencapsulation PCMs for concrete and wall/wallboards, the specific research efforts on both subjects are reviewed separately. This paper presents an overview of the previous research work on microencapsulation technology for thermal energy storage incorporating the phase change materials (PCMs) in the building applications, along with few useful conclusive remarks concluded from the available literature.

Development of phase change materials based microencapsulated technology for buildings: a review

With a characteristic of type I water adsorption isotherms, NaA zeolite has been considered as a very promising candidate for the utilization in adsorptive rotary wheel dehumidification system for deep dehumidification. However, high desorption temperature of the zeolite is not conducive to the system energy saving. In this research, the La-modified, Nd-modified and the binary La/Nd-modified NaA zeolites were synthesized by microwave-assisted ionexchangemethod to reduce the desorption temperature. The structural and the composition of the modified products were characterized using X-ray diffraction (XRD) and X-ray Energy Dispersive Spectrometry (EDS), and their adsorption/desorption performances were evaluated by static adsorption, thermogravimetry (TG) and temperature programmed desorption (TPD). TG results exhibited that, Nd-modified zeolite with the highest ion-exchange degree (α) of 63.35% was more effective in reducing the desorption temperature of NaA zeolite. TPD analysis also demonstrated that the binary modified adsorbent had a lower desorption activation energy (Ed), which indicates that the binary modified zeolite as deep dehumidification adsorbent has an excellent desorption performance.

Improved desorption performance of NaA zeolite by rare earth (Re = La, Nd) ion exchange

The invention discloses a compounding phase-change material and a device used for heat dissipation of a silicon group solar battery. The device mainly comprises a cover plate, a box body and fins, wherein the fins in the box body is filled with an organic/ compounding phase-change material the phase transition temperature of which is at 20-50 DEG C; when sun radiates the surface of the silicon group solar battery, the surface temperature of the battery is heightened, the heat transfers to the phase-change material through the box body, when the temperature is higher than phase-change temperature, and the phase-change material absorbs heat so as to generate phase change and store the heat; and meanwhile, the fins lead the heat to emit into surrounding air, thereby realizing heat-sink cooling of the solar battery. The compounding phase-change material has higher heat-conduction coefficient, and can keep stereotypia characteristics in a phase-change process; and the heat dissipation device provided by the invention has the advantages of high heat storage, heat releasing and cooling rate, no liquid flow and leaking problem, easiness in packaging, convenience in operation and maintenance, and is used for a solar battery photovoltaic generating system, thereby improving the generating efficiency and the reliability of the battery.

Compounding phase-change material and device used for heat dissipation of silicon group solar battery

Method for preparing highly heat-conducting ceramic fiber corrugated paper

The invention discloses a preparation method of a high heat conductive and hight temperature resistant corrugated ceramic-based heat exchanger chip. The method comprises the following steps of: first, impregnating a ceramic fiber paper in a sizing agent; carrying out hot-press forming on the ceramic fiber paper by using a corrugated paper machine so as to obtain a single-face corrugated paper; bonding the single-face corrugated paper with the flat-plate ceramic fiber paper impregnated by the sizing agent so as to obtain a double-face corrugated paper; cutting the double-face corrugated paper into square shapes with same sizes; and then overlapping the squares with each other along the square face according to a corrugated paper passage of 90 degrees; bonding the squares with each other soas to obtain the corrugated ceramic-based heat exchanger chip; curing, bonding and sintering the corrugated ceramic-based heat exchanger chip; naturally cooling the corrugated ceramic-based heat exchanger chip to room temperature; impregnating the chip into a suspension consisting of silica gel and a high heat conductive inorganic filler; impregnating, depositing and taking out the chip; drying the chip after blowing the liquid; and drying the chip so as to obtain the high heat conductive and hight temperature resistant corrugated ceramic-based heat exchanger chip. According to the invention,by using the overlapped honeycomb structure, the heat exchanging area of the heat exchanger unit volume is increased, no inference is caused between the heat exchanging passages so that clean heat exchanging airflow is obtained to get the characteristics of heat exchanging continuity, compact structure and the like.

Preparation method of high heat conductive and hight temperature resistant corrugated ceramic-based heat exchanger chip

Excellent ultra-thin heat pipes (UTHP) require a wick with high capillary force (ΔPc) and a good permeability performance (K). In this work, a copper powder-fiber composite wick was fabricated by sintering of the copper powder and fiber mixture. Effects of the copper powder particle size, copper powder volume ratio, as well as the super-hydrophilic treatment were investigated, and the results indicate that the copper powder volume ratio is the most significant factor by orthogonal experiments. Moreover, sensitivity analysis shows that super-hydrophilic treatment contributes the lower capillary force and higher permeability, except when copper powder particle size is high to 80 mesh and powder ratio is low to 20%. Interestingly, the overall capillary performance (ΔPc·K) of the super-hydrophilic treated wicks is significantly improved. Besides, for the super-hydrophilic treated wicks, both the smaller copper powder particle size and volume ratio contribute the higher permeability and better comprehensive performance, even though a worse capillary force.

Yutang Fang

Papers

Improved desorption performance of NaA zeolite by rare earth (Re = La, Nd) ion exchange

Compounding phase-change material and device used for heat dissipation of silicon group solar battery

Method for preparing highly heat-conducting ceramic fiber corrugated paper

Preparation method of high heat conductive and hight temperature resistant corrugated ceramic-based heat exchanger chip

Capillary performance analysis of copper powder-fiber composite wick for ultra-thin heat pipe