Today, latent heat storage technology has advanced to allow reuse of waste heat in the middle-temperature range. This paper describes an approach to develop a latent heat storage system using middle-temperature waste ...Today, latent heat storage technology has advanced to allow reuse of waste heat in the middle-temperature range. This paper describes an approach to develop a latent heat storage system using middle-temperature waste heat (~100oC - 200oC) from factories. Direct contact melting and solidification behavior between a heat-transfer fluid (oil) and a latent heat storage material mixture were observed. The mixture consisted of mannitol and erythritol (Cm = 70 mass %, Ce = 30 mass %) as a phase-change material (PCM). The weight of the PCM was 3.0 kg and the flow rate of the oil, foil, was 1.0, 1.5, or 2.0 kg/min. To decrease the solidified height of the PCM mixture during the solidification process, a perforated partition plate was installed in the PCM region in the heat storage vessel. PCM coated oil droplets were broken by the perforated partition plate, preventing the solidified height of the PCM from increasing. The solidification and melting processes were repeated using metal fiber. It was found that installing the metal fiber was more effective than installing the perforated partition plate to prevent the flow out problem of the PCM.展开更多
PCMs (Phase Change Materials) can be integrated into building envelopes to decrease the building energy consumption, refine the indoor thermal comfort, shift and reduce the peak electricity load due to its relatively ...PCMs (Phase Change Materials) can be integrated into building envelopes to decrease the building energy consumption, refine the indoor thermal comfort, shift and reduce the peak electricity load due to its relatively large latent heat. In this study, influence of the PCM layer location on the multilayer wall thermal performance is numerically researched in four walls under the climate conditions of Chengdu, China. The results only shows when the phase change of PCM occurs;its latent thermal storage performance can be played and have the significant influence on wall thermal performance. Due to phase change of PCM occurs, the fluctuation amplitudes of inner surface temperature and heat flow are reduced obviously;the temperature peak value is delayed in the phase-change occurred periods. In addition, the PCM layer can reduce inner surface heat flow, especially in summer and transition season, which is in the phase-change occurred periods. The average annual heat flow can be reduced by 8.5% - 11.8%. And when the PCM layer is closer to the wall internal side, the influence of the PCM layer location on the multilayer wall thermal performance is more significantly.展开更多
Infrared radiation is one of the main exposure symptoms of military targets. Infrared radiation differences between targets and backgrounds should be eliminated to the greatest extent to fight against all kinds of inf...Infrared radiation is one of the main exposure symptoms of military targets. Infrared radiation differences between targets and backgrounds should be eliminated to the greatest extent to fight against all kinds of infrared reconnaissance. In addition to the employment of the camouflage paint with low emissivity, reducing the surface temperature of targets is an urgent and difficult challenge. PCM (phase-change material) can be used to effectively solve this problem. The application of microcapsule in the infrared stealth materials greatly promotes the development of infrared stealth technology.展开更多
In this study, a composite of form-stable phase change materials （FSPCMs） were prepared by the incorporation of a eutectic mixture of capric-palmitic-stearic acid （CA-PA-SA） into expanded vermiculite （EV） via va...In this study, a composite of form-stable phase change materials （FSPCMs） were prepared by the incorporation of a eutectic mixture of capric-palmitic-stearic acid （CA-PA-SA） into expanded vermiculite （EV） via vacuum impregnation. In the composites, CA-PA-SA was utilized as a thermal energy storage material, and EV served as the supporting material. X-ray diffraction and Fourier transform infrared spectroscopy results demonstrated that CA-PA-SA and EV in the composites only undergo physical combination, not a chemical reaction. Scanning electron microscopy images indicated that CA-PA-SA is sufficiently absorbed in the expanded vermiculite porous network. According to differential scanning calorimetry results, the 70 wt% CA-PA-SA/EV sample melts at 19.3 ℃ with a latent heat of 117.6J/g and solidifies at 17.1 ℃ with a latent heat of 118.3J/g. Thermal cycling measurements indicated that FSPCMs exhibit adequate stability even after being subjected to 200 melting-freezing cycles. Furthermore, the thermal conductivity of the composites increased by approximately 49.58% with the addition of 5 wt% of Cu powder. Hence, CA-PA-SA/EV FSPCMs are effective latent heat thermal energy storage building materials.展开更多
The application of phase-change materials (PCM)for thermal-energy storage is hampered by their low thermal conductivity.Copper particles (CP)and copper foam (CF)were used to enhance the thermal conductivity of a micro...The application of phase-change materials (PCM)for thermal-energy storage is hampered by their low thermal conductivity.Copper particles (CP)and copper foam (CF)were used to enhance the thermal conductivity of a microencapsulated phase-change material (MicroPCM).The effects of the CP size and mass fraction and the pore number per inch (PPI)of the CF on the thermal properties of the MicroPCM were investigated.The chemical and microstructures of the MicroPCM and its CP composites were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy,respectively. Their thermal conductivities,phase-change temperatures,and latent heats were measured.Adding CP into the MicroPCM decreased the latent heats with increasing loadings.The thermal conductivities of MicroPCM/CP (Swt%,50nm diameter)and MicroPCM/CF (PPI 30)were 1.12times and 3.46times that of the unmodified MicroPCM at 20℃,respectively.Thermal-energy storage performances of the MicroPCM/CF composites were studied at a power of 2.9±0.1W.The temperature of the contact surfaces of the pure MicroPCM and its composites (PPI 10,PPI 20,PPI 30)was 75.88,51.27,50.52,and 50.23℃,respectively.The composites displayed more uniform temperature distributions.展开更多
文摘Today, latent heat storage technology has advanced to allow reuse of waste heat in the middle-temperature range. This paper describes an approach to develop a latent heat storage system using middle-temperature waste heat (~100oC - 200oC) from factories. Direct contact melting and solidification behavior between a heat-transfer fluid (oil) and a latent heat storage material mixture were observed. The mixture consisted of mannitol and erythritol (Cm = 70 mass %, Ce = 30 mass %) as a phase-change material (PCM). The weight of the PCM was 3.0 kg and the flow rate of the oil, foil, was 1.0, 1.5, or 2.0 kg/min. To decrease the solidified height of the PCM mixture during the solidification process, a perforated partition plate was installed in the PCM region in the heat storage vessel. PCM coated oil droplets were broken by the perforated partition plate, preventing the solidified height of the PCM from increasing. The solidification and melting processes were repeated using metal fiber. It was found that installing the metal fiber was more effective than installing the perforated partition plate to prevent the flow out problem of the PCM.
文摘PCMs (Phase Change Materials) can be integrated into building envelopes to decrease the building energy consumption, refine the indoor thermal comfort, shift and reduce the peak electricity load due to its relatively large latent heat. In this study, influence of the PCM layer location on the multilayer wall thermal performance is numerically researched in four walls under the climate conditions of Chengdu, China. The results only shows when the phase change of PCM occurs;its latent thermal storage performance can be played and have the significant influence on wall thermal performance. Due to phase change of PCM occurs, the fluctuation amplitudes of inner surface temperature and heat flow are reduced obviously;the temperature peak value is delayed in the phase-change occurred periods. In addition, the PCM layer can reduce inner surface heat flow, especially in summer and transition season, which is in the phase-change occurred periods. The average annual heat flow can be reduced by 8.5% - 11.8%. And when the PCM layer is closer to the wall internal side, the influence of the PCM layer location on the multilayer wall thermal performance is more significantly.
文摘Infrared radiation is one of the main exposure symptoms of military targets. Infrared radiation differences between targets and backgrounds should be eliminated to the greatest extent to fight against all kinds of infrared reconnaissance. In addition to the employment of the camouflage paint with low emissivity, reducing the surface temperature of targets is an urgent and difficult challenge. PCM (phase-change material) can be used to effectively solve this problem. The application of microcapsule in the infrared stealth materials greatly promotes the development of infrared stealth technology.
基金financially supported by the National Natural Science Foundations of China (Grant Nos. 51472222 and 51372232)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20130022110006)the Fundamental Research Funds for the Central Universities for financial support (Grant No. 2652016046)
文摘In this study, a composite of form-stable phase change materials （FSPCMs） were prepared by the incorporation of a eutectic mixture of capric-palmitic-stearic acid （CA-PA-SA） into expanded vermiculite （EV） via vacuum impregnation. In the composites, CA-PA-SA was utilized as a thermal energy storage material, and EV served as the supporting material. X-ray diffraction and Fourier transform infrared spectroscopy results demonstrated that CA-PA-SA and EV in the composites only undergo physical combination, not a chemical reaction. Scanning electron microscopy images indicated that CA-PA-SA is sufficiently absorbed in the expanded vermiculite porous network. According to differential scanning calorimetry results, the 70 wt% CA-PA-SA/EV sample melts at 19.3 ℃ with a latent heat of 117.6J/g and solidifies at 17.1 ℃ with a latent heat of 118.3J/g. Thermal cycling measurements indicated that FSPCMs exhibit adequate stability even after being subjected to 200 melting-freezing cycles. Furthermore, the thermal conductivity of the composites increased by approximately 49.58% with the addition of 5 wt% of Cu powder. Hence, CA-PA-SA/EV FSPCMs are effective latent heat thermal energy storage building materials.
基金National Natural Science Foundation of China (Grant No.U1407125),the Qing Lan Project of Jiangsu Province,the 333High Level Talents Training Project of Jiangsu Province,and the Six Talent Peak High-level Talent Project of Jiangsu Province,China.
文摘The application of phase-change materials (PCM)for thermal-energy storage is hampered by their low thermal conductivity.Copper particles (CP)and copper foam (CF)were used to enhance the thermal conductivity of a microencapsulated phase-change material (MicroPCM).The effects of the CP size and mass fraction and the pore number per inch (PPI)of the CF on the thermal properties of the MicroPCM were investigated.The chemical and microstructures of the MicroPCM and its CP composites were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy,respectively. Their thermal conductivities,phase-change temperatures,and latent heats were measured.Adding CP into the MicroPCM decreased the latent heats with increasing loadings.The thermal conductivities of MicroPCM/CP (Swt%,50nm diameter)and MicroPCM/CF (PPI 30)were 1.12times and 3.46times that of the unmodified MicroPCM at 20℃,respectively.Thermal-energy storage performances of the MicroPCM/CF composites were studied at a power of 2.9±0.1W.The temperature of the contact surfaces of the pure MicroPCM and its composites (PPI 10,PPI 20,PPI 30)was 75.88,51.27,50.52,and 50.23℃,respectively.The composites displayed more uniform temperature distributions.
