Research Of Solid-Solid Phase Change Materials Of The Solar Ventilation Device

With the development of social economy, and the increasing demand for energy, energy has become the basis of human survival and development. Energy storage technology is a high and new technology developed in the late 20 th century, which is the effective measure to improve energy efficiency, while energy storage materials in energy storage technology, the basis of the energy storage density of about one order of magnitude higher than the sensible heat and exothermic temperature constant. Recentlyphase change material(PCM) has been a hot research topic in the field, especially solid- solid phase changematerial which have unique advantages out of solid- liquid phase change materials, so it has become the most development potential of heat storage material.This article selects the phase transition characteristics of excellent and good energy storage effect of polyethylene glycol as a phase change unit, combined with diisocyanate solid- solid phase change heat storage material preparation and add carbon nanotubes(CNTs).Five kinds of phase change materials(PCMs) are prepared by adding various mass fractions of carbon nanotubes(CNTs)(viz., 0.5%,1%,2%,3% and 5%) into Polyethylene glycol(PEG) via a two-step method aiming to solar chimney heat storage applications. The thermal physical property and cycle stability of the as-prepared PCMs are tested. Results show that the thermal conductivity and phase change heat transfer rate are significantly improved after adding CNTs into Polyurethane phase change material. As the mass fraction of the CNT is 5%, the thermal conductivity of the PCMs is 0.65 W/m?K which is 103% higher than that of the pure PUPCM. Moreover, the heat storage and release rate are 42.8% and 44.2% higher than those of the pure PUPCM respectively. The phase change latent heat of the PCMs is reduced after the addition of the CNTs. As the mass fraction of the CNTs is 5%, the phase change latent heat of the PCMs is 107J·g-1 which is 71.8% of that of the pure PUPCM. Scince the combination of the CNTs and the PUPCM is in physical power the PCMs have good thermal stability without weight loss in the temperature rising process. After hundreds of timesof circulation, the phase transition temperature, phase change latent heat and thermal conductivity of composite phase change materials approximately keep constant. This indicated that the PCMs will have exellent cycle stability in the heat storage applications.By TG and FT- IR analysis, preparation of the composite phase change material thermal stability is good and no new substance; Many times after the cycle test, the thermal conductivity of composite phase change materials and regenerative capacity did not occur significant attenuation, composite phase change materials has good thermal cycling stability.After several times after the cycle test of composite phase change materials thermal conductivity and heat capacity did not occur significant attenuation, composite material has good cycle stability.Composite phase change materials in the solar ventilation system temperature is 57.1 ?, reached the peak of temperature of composite; In at about 10:00 ~ 21:00, channel and the average temperature and outdoor temperature difference between 5 ~ 13.7 ?, the outlet wind speed is 0.4 ~ 0.74 m/s, ventilation rate is 55.0 ~ 103.9 m3 / h, fully meeting the requirements of the fresh air.