Application of high temperature heat pipe in hypersonic vehicles thermal protection

In order to develop further the application of high temperature heat pipe in hypersonic vehicles thermal protection, the principles and characteristics of high temperature heat pipe used in hypersonic vehicles thermal protection were introduced. The methods of numerical simulation, theory analysis and experiment research were utilized to analyze the frozen start-up and steady state characteristic of the heat pipe as well as the machining improvement for fabricating irregularly shaped heat pipe which is suitable for leading edge of hypersonic vehicles. The results indicate that the frozen start-up time of heat pipe is long （10 min） and there exists large temperature difference along the heat pipe （47 ℃/cm）, but the heat pipe can reduce the temperature in stagnation area of hypersonic vehicles from 1 926 to 982 ℃ and work normally during 1 000-1 200℃. How to improve the maximum heat transfer capability and reduce the time needed for start-up from frozen state of the heat pipe by optimizing thermostructure such as designing of a novel wick with high performance is the key point in hypersonic vehicles thermal protection of heat pipe.

Experimental Performance of Moderate and High Temperature Heat Pump Charged with Refrigerant Mixture BY-3

Theoretical and experimental analysis of a new refrigerant mixture BY-3 was conducted based on a single-stage vapor compression refrigeration system. The water-water heat pump system used BY-3 to produce hot water when the low temperature was 20 ℃. The following results were obtained: the highest temperature at the condenser outlet reached about 85 ℃; when the difference between the water temperatures at the condenser outlet and the evaporator inlet was less than 40 ℃, the coefficient of performance (COP) was larger than 4; when the difference reached 55 ℃, the COP still kept 3; the discharge temperature of BY-3 was lower than 100 ℃, and the refrigerant vapor pressure kept lower than 1.8 MPa. When the water temperature at the condenser outlet reached over 85 ℃, nearly a 5 ℃ superheating temperature was maintained.

Maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick

A mathematical model was developed to predict the maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick. The effects of the inclination angle and geometry structure were considered in the proposed model.Maximum heat transfer capacity was also investigated experimentally. The model was validated by comparing with the experimental results. The maximum heat transfer capacity increases with the vapor core radius increasing. Compared with the inclination angle of0°, the maximum heat transfer capacity increases at the larger inclination angle, and the change with temperature is larger. The performance of heat pipe with triangular grooved wick is greatly influenced by gravity, so it is not recommended to be applied to the dish solar heat pipe receiver.

INFLUENCE OF HEAT TREATMENT ON OXIDATION PROPERTIES OF C/C COMPOSITES FABRICATED BY HIGH PRESSURE IMPREGNATION CARBONIZATION

Felt base carbon/carbon composites fabricated by super-high pressure impregnation carbonization process (SPIC) were heat treated at high temperature 2773K. The oxidation properties of felt base carbon/carbon composites were investigated at different temperatures (773-1173K), and the microstructures of carbon/carbon composites were studied by SEM and X-ray diffraction. The experimental results showed that the inter-laminar distance of (002) plane (d002) deceased while the microcrystalline stack height (Lc) increased. The oxidation rate of felt base carbon/carbon composites was invari-able at certain temperatures. The oxidation mechanism of carbon/carbon composites changed remarkably at the oxidation temperature 973K. At the initial oxidation stage of carbon/carbon composites, carbon matrix was oxidized much more rapidly than carbon felt.

Low-temperature Rapid Synthesis of Ultrafine Hafnium Carbide Ceramic Powders

Nano hafnium carbide（HfC） powders were synthesized by sol-gel combining hightemperature rapid heat treatment process using citric acid and hafnium tetrachloride as the raw materials. The effects of ball milling treatment on the phase and morphology of pyrolysis products（HfO_2-C） and final HfC product were investigated and the influences of heat treatment temperature and holding time on the structure and properties of the synthesized hafnium carbide powders were also studied. The experimental results showed that the HfO_2-C powders with good uniformity and small particle size were prepared by controlling the milling time. Pure HfC powders with an average particle size of 500 nm were obtained at 1 700 ℃ with a holding time of 3 min, and the oxygen content was about 0.69 wt%, lower than that of the hafnium carbide powders prepared by SPS（0.97%）.

Synthesis of Iron-containing Carbon Microparticles from Deoiled Asphalt and Ferrocene

The deoiled asphalt as the carbon source and the ferrocene as the metal source and the catalyst precursor were chosen to synthesize iron-containing carbon microparticles through co-carbonization at the temperature of about 450℃ for 3 h. The resulting products were treated at 2 000 ℃ for 2 h. All samples were examined by high resolution transmission electron microscopy （HRTEM） and X-ray diffraction （XRD）. The results show that the iron particles in the heat-treated material are completely coated by carbon. In addition to the fully filled carbon microparticles as well as hollow carbon ones, also form carbon fibers with hollow centers. The formation mechanism of the as-prepared products was discussed briefly.

Nacre-bionic nanocomposite membrane for efficient in-plane dissipation heat harvest under high temperature

Waste heat management holds great promise to create a sustainable and energy-efficient society as well as contributes to the alleviation of global warming.Harvesting and converting this waste heat in order to improve the efficiency is a major challenge.Here we report biomimetic nacre-like hydroxyl-functionalized boron nitride(BN)-polyimide(PI)nanocomposite membranes as efficient 2D in-plane heat conductor to dissipate and convert waste heat at high temperature.The hierarchically layered nanostructured membrane with oriented BN nanosheets gives rise to a very large anisotropy in heat transport properties,with a high in-plane thermal conductivity(TC)of 51 Wm^(-1) K^(-1) at a temperature of~300 C,7314%higher than that of the pure polymer.The membrane also exhibits superior thermal stability and fire resistance,enabling its workability in a hot environment.In addition to cooling conventional exothermic electronics,the large TC enables the membrane as a thin and 2D anisotropic heat sink to generate a large temperature gradient in a thermoelectric module(△T=23 ℃)through effective heat diffusion on the cold side under 220 C heating.The waste heat under high temperature is therefore efficiently harvested and converted to power electronics,thus saving more thermal energy by largely decreasing consumption.

Spatial-temporal Differentiation of Sauna Days with Different Intensities in China from 1961 to 2017

Sauna weather with high temperature, high humidity and long standby time has become one of the main meteorological hazards faced by urban residents. Based on the daily maximum temperature and relative humidity datasets of 545 meteorological observation stations in China from 1961 to 2017, the spatial-temporal evolution characteristics of sauna days with different intensities in China were studied from three aspects: climatic state, trend and fluctuation characteristics, using the standard of sauna days defined by the Central Meteorological Observatory of China Meteorological Administration. The results showed that: firstly, the spatial pattern of sauna days with different intensities in China was high in southeast China and low in northwest China from 1961 to 2017, and the spatial pattern of sauna days with the same intensity in different research periods had little difference, which was in good agreement with the spatial pattern of sauna days with corresponding intensities in the whole research period. With the increase of intensity, the sauna days in China decreases gradually. Secondly, the trend of sauna days with different intensities in China was bounded by Hu Huanyong Line from 1961 to 2017, showing a pattern of increasing or decreasing mosaic in the southeast China and mainly decreasing trend, while the spatial differentiation pattern in the northwest China changed little. The trend of sauna days with different intensities in China increased significantly in 1991-2017 compared with 1961-1990. Thirdly, the fluctuation of sauna days with different intensities in China was bounded by Hu Huanyong Line, showing a spatial pattern of large fluctuations in the southeast China and small fluctuations in the northwest China. And the fluctuation of sauna days and heavy sauna days showed obvious threeblock distribution characteristics. The fluctuation characteristics of sauna days with different intensities in China from 1961 to 1990 and 1991 to 2017 were in good agreement with the whole research period. The fluctuation difference before and after 1990 mainly concentrated in the vicinity of Hu Huanyong Line and its southeast area, and the fluctuation differences increased mainly, indicating that the variation of sauna days with different intensities in the southeast China increased from 1991 to 2017.

HTGR Process Heat Application Study

The 10MW high temperature gas-cooled reactor test module (HTR-10) is currently under construction.One of its objectives is to develop high temperature process heat applications. To realize this target, various high temperature gas-cooled reactor (HTGR) process heat applications have been analyzed. This paper briefly describes the possibilities and experimental schemes for using the HTR-10 for process heat application studies.