Search

Coalfield wildfires are serious catastrophes associated with mining activities. Generally, the coal wildfire areas have tremendous heat accumulation regions. Eliminating the internal heat is an effective method for coal wildfire control. In this study, high thermal conductivity component of a heat pipe (HP) was used for enhancing the heat dissipation efficiency and impeding heat accumulation. An experimental system was set up to analyze the thermal resistance network of the coal-HP system. A coal-HP heat removal model was also established for studying the heat transfer performance of HP on the coal pile. The HP exhibited outstanding cooling performance in the initial period, resulting in the highest temperature difference between the coal pile and ambient temperature. However, the effect of the HP on the distribution temperature of coal piles decreased with increasing distance. The largest decline in the coal temperature occurred in a 20-mm radius of the HP; the temperature decreased from 84.3 to 50.9 °C, a decline of 39.6%. The amount of energy transfer by the HP after 80 h was 1.0865, 2.1680, and 3.3649 MJ under the initial heat source temperatures of 100, 150, and 200 °C, respectively. The coal was governed below 80 °C with the HP under the experimental conditions. It revealed that the HP had a substantial effect on thermal removal and inhibited spontaneous coal combustion. In addition, this paper puts forward the technological path of HP to control typical coalfield wildfire.As powerful heat transfer components, as soon as HPs are inserted into the coal piles with a reasonable distance, they play a vital role in preventing coal self-ignition and substantially lowering the temperatures of high temperature zones. [ABSTRACT FROM AUTHOR]

This paper focuses on a dataset reflecting the potential for the development of enhanced geothermal systems (EGS) in continental China. Depth-temperature profiles, derived from surface heat flow, thermophysical parameters, the thickness of sedimentary layers, and ground surface temperatures, are the basis of EGS resource assessment. According to up-to-date 1230 pieces of heat flow data, we updated the heat flow measurements and depth-temperature distribution maps in continental China. Subsequently, the EGS resources were estimated using volume method with respect to various depth slices, temperature grades, and provinces, respectively. Results indicate that the total heat content within the depth of 3-10 km is 22.9 × 10 EJ (1 EJ = 10 J), of which recoverable part is equivalent to 1.56 × 10 billion tons coal equivalent by the conservative recovery factor (2%). Under the assumption of 30-year-long production life, 10 °C reduction from the original rock temperature, and 2% as the recoverable factor, the production of electric power in continental China is estimated to be 4.56 × 10 MWe. On the basis of the calculation, we delineated four favorable targets for EGS resources exploration, including South and Northeast Tibet, West Yunnan (Tengchong), the southeast coast of China (Zhejiang, Fujian, and Guangdong), and Northeast China (Songliao Basin and Changbai Mountain). [ABSTRACT FROM AUTHOR]

Investigations into the thermal characteristics of glass-water heat pipes from 0 °C to 60 °C were carried out at the National Institute of Metrology (NIM), China. In this paper, studies on a glass-water heat pipe with four thermometer wells are described. The experimental results indicated that the temperature stability and uniformity of the thermometer well of the glass-water heat pipes are within several tenths of a millikelvin when the heat pipes are immersed in a constant-temperature liquid bath, since they have a highly effective thermal conductivity. They are able to maintain a constant temperature by the absorption or liberation of the latent heat of evaporation to attenuate temperature fluctuations of the surroundings. Also, above 0 °C to 30 °C, the temperature stability of the thermometer well of the glass-water heat pipe is better than 0.1 mK for approximately 16 h. The maximum temperature differences among the thermometer wells are less than 5.5 mK when the water heat pipes operate in the range from 0 °C to 60 °C. Therefore, water heat pipes are very promising to improve the performance of liquid baths and to accurately calibrate thermometers by comparison. [ABSTRACT FROM AUTHOR]

The equation describing the transfer of radiant energy in semitransparent media is radiative transfer equation. In three-dimensional semitransparent media, radiative intensity is a function of 7 dimensions, which can only be solved through the numerical method in most circumstances. Numerical simulation has become an important way in the study and application of the theory of thermal radiative transfer in semitransparent media. This paper reviews the recent progress of Chinese scholars in the field of computational thermal radiative transfer, and proposes some important subjects in this field for future study. [ABSTRACT FROM AUTHOR]

Rice is one of the most important crops as the staple food for more than half of the world's population. Rice improvement has achieved remarkable success in the past half-century, with the yield doubled in most parts of the world and even tripled in certain regions, which has contributed greatly to food security globally. Rapid population growth and economic development pose a constantly increased food requirement. However, rice yield has been hovering in the past decade, which is mainly caused by the absence of novel breeding technologies, reduction of genetic diversity of rice cultivars, and serious yield loss due to increasingly severe occurrences of insects, diseases, and abiotic stresses. To address these challenges, Chinese scientists proposed a novel rice breeding goal of developing Green Super Rice to improve rice varieties and realize the sustainable development of agriculture, by focusing on the following 5 classes of traits: insect and disease resistance, drought-tolerance, nutrient-use efficiency, quality and yield potential. As a modern breeding approach, transgenic strategy will play an important role in realizing the goal of Green Super Rice. Presently, many transgenic studies of rice have been conducted, and most of target traits are consistent with the goal of Green Super Rice. In this paper, we firstly review technical advances of rice transformation, and then outline the main progress in transgenic rice research with respect to the most important traits: insect and disease-resistance, drought-tolerance, nutrient-use efficiency, quality, yield potential and herbicide-tolerance. The prospects of developing transgenic rice are also discussed. [ABSTRACT FROM AUTHOR]

In consumer fireworks, various functions of chemicals create an energetic reaction with a type of colored light, smoke, heat, and the sound to achieve the pyrotechnic effects. Fireworks mixtures may be highly sensitive to external disturbances such as ignition sources, temperature changes, shocks, friction, and static electricity. Approximately 95% of fireworks are imported from China by ocean shipment, taking 4 days to a week to Taiwan. The prediction and assessment for the nth-order reaction, and thermokinetic parameters from thermal safety model for fireworks and pyrotechnic compositions were investigated. This study showed which reaction intensity of the propellant as water was added. It can be seen from the results that water will affect the thermal hazard of propellant. Moreover, the novel findings indicated that the water increased the thermal hazard of the propellant and consequently increased the risk for launching a degradation. Based on the heat transfer theoretical models, the time to maximum rate and time to conversion limit were extrapolated for consideration and discussion. [ABSTRACT FROM AUTHOR]

Because of the relatively low soil moisture in arid or semi-arid regions, water vapour movement often predominates in the vadose zone and affects the partitioning of energy among various land surface fluxes. In an outdoor sand bunker experiment, the soil water content at 10 and 30 cm depth were measured at hourly intervals for 2.5 days during October 2004. It was found that the soil moisture reached the daily maximum value (5.9–6.1% at 10 cm and 11.9–13.1% at 30 cm) and minimum value (4.4–4.5% at 10 cm and 10.4–10.8% at 30 cm) at midday (0–1 p.m. for 10 cm and 2–3 p.m. for 30 cm) and before dawn (2–3 a.m. for 10 cm and 4–5 a.m. for 30 cm), respectively. The modified HYDRUS-1D code, which refers to the coupled water, water vapour and heat transport in soil, was used to simulate the moisture and water vapour flow in the soil. The numerical analyses provided insight into the diurnal movement of liquid water and water vapour driven by the gradients of pressure heads and temperatures in the subsurface zone. The simulated temperature and water content were in good agreement with the measured values. The spatial–temporal distribution of liquid water flux, water vapour flux and soil temperature showed a detailed diurnal pattern of soil water dynamics in relatively coarse sand. [ABSTRACT FROM AUTHOR]

Based on fluctuational observations of three-component wind velocity ( u′, v′, w′) and temperature, T′, from a meteorological tower of 325 m located in Beijing, China, a number of turbulent linear correlation coefficients are calculated using a local scaling approach for turbulence statistics. The further applicability of this scaling is investigated by the formulation of similarity relationships for correlation coefficients of momentum transfer e.g., | r uw |, | r vw | and | r uv |, heat transfer e.g., | r uT |, | r vT | and | r wT |, and the ratios | r wT / r uw | and | r vT / r vw |. Under various stratifications, empirical similarity relationships for most of these correlation coefficients are derived to be function of a single local stability parameter and found to be in good agreement with experimental results. [ABSTRACT FROM AUTHOR]

In this study, we employed a regional model to simulate the impact of urban expansion on monthly climate in Pearl River Delta (PRD) region. Two experiments were performed by prescribing two different land covers in the PRD region. One land cover represents vegetation in the 1970s which is derived from the United States Geological Survey (USGS) data with 24-category (hereafter referred to as NU). The other land cover represents the current urban condition which is derived from remote sensing data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) in 2004 (hereafter referred to as HU). Using the two land cover datasets, monthly climate of October 2004 was simulated, which was a very dry season in the PRD region. The results obtained from the numerical simulation show a distinct difference in simulated shelter-level temperature, humidity, surface fluxes and the height of planetary boundary layer (PBL) with two different land cover data sets being specified. The maximum difference in simulated monthly mean temperature over urban areas was 0.9 °C. A large temperature difference was found in urbanized area in Guangzhou, Dongguan, Zhongshan and Shenzhen. The monthly mean relative humidity in urban areas decreased by 1.4% as a result of urban expansion (from 59.2% in NU to 57.8% in HU). The maximum decrease in mixing ratio was 0.4 g/kg in Guangzhou and Dongguan, whereas the maximum decrease in relative humidity was 2.4%. There was an increase of sensible heat flux in developed lands and the maximum increase was 90 W m−2. In contrast, latent hear flux in urban area decreased and the maximum decrease was 300 W m−2. In addition, the increase in mean height of PBL ranged from 20 to 80 m (HU compared with NU), and the maximum change of the height was 180 m over urban area in city of Guangzhou. [ABSTRACT FROM AUTHOR]

In this study, we tried to model the processes of moisture and heat transfers in the soil–vegetation–atmosphere system in an integrated comprehensive way. The purpose of the study is to simulate profiles of soil water content and temperature at root active zone (i.e., 0–50 cm), taking the root water uptake, soil evaporation, and canopy transpiration into account. The water and heat transfer equations are solved by an iterative Newton–Raphson technique and a finite difference method is used to solve the governing equations. Soil water content and soil temperature dynamics could be simulated rather accurately in a cropped field on Loess Plateau area. The water and heat transfer flux predicted by the classical theory of Philip and de Vries (Tans Am Geophys Union 38:222–232, ) slightly overestimated near the surface and underestimated at the deeper depths, as a result of the overestimated soil evaporation at the top soil layer (0–10 cm) and underestimated crop canopy transpiration at the deeper depths (10–50 cm). Water content tended to be underestimated for the entire profile at the soil surface (from 0 to 50 cm). Soil temperatures during the simulated period was slightly overestimated in the nighttimes and underestimated in the daytimes, as a result of the underestimated soil water content at the top soil layer (0–10 cm) and overestimated at the deeper depths (10–50 cm). Soil temperatures tended to be underestimated for the entire profile at the soil surface (from 0 to 50 cm). While the sum of the water and heat regimes yielded a much better match with the soil water content and soil temperature obtained from the field observations. The results obtained show that the model coupled water and heat transfer is able to capture the dynamics of soil water content. [ABSTRACT FROM AUTHOR]

Soil heat flux is examined using a new method considering soil thermal conduction and convection processes. Using this method, we determine that soil heat fluxes owing to soil thermal conduction and convection were significant for the Naqu site in the summer of 1998. Experimental analyses of the surface energy balance are given. [ABSTRACT FROM AUTHOR]