巷道火灾过程中燃烧速率和释热速率的预测

根据燃料的元素构成、热化学反应式、反应物和生成物的焓变以及燃烧过程中监测到的烟气中氧气浓度随时间变化规律,提出了计算某一时刻燃料燃烧速率、释热速率和介质吸热率的关系式；通过实际规模的火灾试验,对其数据的计算表明,对木质类巷道火灾,最大比燃烧速率为0．193,最大释热速率约为1～3．5 MW,介质的吸热率为22%．

天然气在土壤中泄漏的稳态温度场分析

埋地高压天然气经小孔泄漏会导致土壤冻结形成冻土,应用一元气体动力学、流体力学和传热学知识建立了天然气小孔泄漏吸热率模型和土壤稳态温度场模型,并进行了实例计算。结果表明:当天然气输送压力小于临界压力,小孔泄漏吸热率随压力的增大而增大;当天然气输送压力大于等于临界压力,小孔泄漏吸热率达到最大值;冻土厚度随土壤热导率或空气对流传热系数的增大而减小,但土壤热导率对其影响较小,空气对流传热系数对其影响较大。

Design and fabrication of sintered wick for miniature cylindrical heat pipe

Miniature cylindrical metal powder sintered wick heat pipe （sintered heat pipe） is an ideal component with super-high thermal efficiency for high heat flux electronics cooling. The sintering process for sintered wick is important for its quality. The sintering process was optimally designed based on the equation of the heat transfer limit of sintered heat pipe. Four-step sintering process was proposed to fabricate sintered wick. The sintering parameters including sintering temperature, sintering time, sintering atmosphere and sintering position were discussed. The experimental results showed that the proper sintering temperature was 950 ℃ for Cu powder of 159μm and 900 ℃ for Cu powders of 81 and 38 μm, respectively, while the wick thickness was 0.45 mm and sintering time was 3 h. The optimized sintering time was 3 h for 0.45 and 0.6 mm wick thickness and 1 h for 0.75 mm wick thickness, respectively, when copper powder diameter was 159μm and sintering temperature was 950 ℃. Redox reduction reaction between H2 and CuO during sintering could produce segmentation cracks in Cu powders as a second structure. Sintering at vertical position can effectively avoid the generation of gap between wick and the inner wall of pipe.

OPTIMUM OF PRESSURE RATIOS OF MULTI-STAGE RECIPROCATING COMPRESSOR WITH PRACTICAL INTER-COOLING

The optimum pressure ratio distribution of a multistage reciprocating compressor is presented based on the assumption, i.e. the inter stage cooling is perfect and there are no pressure losses. The optimization of the two or three stage pressure ratio is analyzed in two cases of constant heat transfer rate for the inter cooler or constant inter stage inlet temperature, based on the minimum of the sum of theoretical compression power at each stage about a multi stage reciprocating compressor. Furthermore, with an example of two stage compressor the influence on the sum of the power of each stage is analyzed when practical pressure ratio deviates from the optimum value. It is obtained that under different cooling conditions the optimum pressure ratio distribution of the multi stage compression is various, and the change of the optimum pressure ratio within a small range has little influence on the sum of the power each stage. For the two stage compression, this range can be represented as ε 1=(0 96～1 06)ε 1j .

幕墙玻璃热自爆的影响因素及预防措施

主要从玻璃的吸热率、板面尺寸及玻璃的加工质量三个方面分析了幕墙玻璃热自爆的原因,并针对性地提出了预防热自爆的相关措施。

矿井排风热回收装置中循环水量优化与数值分析

为探究循环水对矿井排风能量品位提升装置热工性能的影响,基于有限时间工程热力学,引入换热器传热不可逆因子,构建了能量品位提升装置的循环模型,推导出了循环水流量的多因素表达式,然后,函数化了水流量对装置吸热流率和综合性能的影响,最后,完成了综合性能系数的数值计算。结果表明,随循环水流量增大,吸热流率呈非线性增大,且增长率逐渐减小并趋于0,而综合性能系数先增大后减小。在此变化过程中,出现了综合性能系数的极大值,确立了优化的循环水质量流率范围,以指导现场工程设计与运行调节。

Thermodynamic analysis of simplified dual-pressure ammonia-water absorption power cycle

A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The structure of the cycle is simple which comprises evaporator,turbine,regenerator(desorber),absorber,pump and throttle valves for both diluted solution and vapor.And it is of high efficiency,because the working medium has large temperature difference in evaporation and small temperature difference in absorptive condensation,which can match the sensible exothermal heat resource and the cooling water simultaneously.Orthogonal calculation was made to investigate the influence of the working concentration,the basic concentration and the circulation multiple on the cycle performance,with 85-110 ℃ heat resource and 20-32 ℃ cooling water.An optimum scheme was given in the condition of 110 ℃ sensitive heat resource and 20 ℃ cooling water,with the working concentration of 0.6,basic concentration of 0.385,and circulation multiple of 5.The thermal efficiency and the power recovery efficiency are 8.06 % and 6.66%,respectively.The power recovery efficiency of the DPAPC-a is 28.8% higher than that of the steam Rankine cycle(SRC) and 12.7% higher than that of ORC(R134a) under the optimized situation.

Analysis of H_2S Tolerance of Pd-Cu Alloy Hydrogen Separation Membranes

The presence of a limited amount of H2S in H2-rich feed adversely affects the Pd-Cu membrane permeation performance due to the sulphidization of the membrane surface. A theoretical model was proposed to predict the S-tolerant performance of the Pd-Cu membranes in presence of H2S under the industrial water-gas-shift(WGS) reaction conditions. The ideas of surface coverage and competitive adsorption thermodynamics of H2S and H2 on Pd-Cu surface were introduced in the model. The surface sulphidization of the Pd-Cu membranes mainly depended on the pressure ratio of H2S to H2, temperature and S-adsorbed surface coverage, i.e., the occurrence of sulphidization on the surface was not directly related with the bulk compositions and structures [body centered cubic and face centered cubic(bcc or fcc)] of Pd-Cu alloy membranes because of the surface segregation phenomena. The resulting equilibrium equations for the H2S adsorption/sulphidization reactions were solved to calculate the pressure ratio of H2S to H2 over a wide range of temperatures. A validation of the model was performed through a comparison between lots of literature data and the model calculations over a rather broad range of operating conditions. An extremely good agreement was obtained in the different cases, and thus, the model can serve to guide the development of S-resistant Pd alloy membrane materials for hydrogen separation.

Influence of Artificial Light on Laying Hens Production of Heat, Moisture and Carbon Dioxide in a Floor Housing System

Investigations about laying hens reactions on artificial light conditions were carried out in a climate chamber equipped with a floor housing system for laying hens. The release of moisture increased during light periods probably due to increased activity which increased respiration rate but also on increased scratching which increased evaporation of moisture from bedding material. The daily average was 6.29 g henl h＂l at 4 lux and 5.97 g henl hl, at 93 lux which corresponds to a difference of 5%. The level of light intensity seemed to have little influence on the release of moisture. The total release of heat was slightly higher during light periods compared to dark periods. Explanations can be increased activity but also feed intake increasing the metabolic rate during light periods. The daily average of total heat production was 17.0 W per hen at 4 lux and 14.7 at 93 lux which corresponds to a difference of 16%. The release of carbon dioxide increased during light periods probably due to increased activity and respiration.

Soil respiration under three different land use types in a tropical mountain region of China

Soil respiration (SR) Wis one of the largest contributors of terrestrial CO_2 to the atmosphere.Environmental as well as physicochemical parameters influence SR and thus, different land use practices impact the emissions of soil CO_2. In this study, we measured SR, bi-monthly, over a one-year period in a terrace tea plantation, a forest tea plantation and a secondary forest, in a subtropical mountain area in Xishuangbanna, China. Along with the measurement of SR rates, soil characteristics for each of the land use systems were investigated. Soil respiration rates in the different land use systems did not differ significantly during the dry season, ranging from2.7±0.2 μmol m^(-2) s^(-1) to 2.8±0.2 μmol m^(-2) s^(-1). During the wet season, however, SR rates were significantly larger in the terrace tea plantation(5.4±0.5 μmol m^(-2)s^(-1)) and secondary forest(4.9±0.4 μmol m^(-2)s^(-1)) than in the forest tea plantation(3.7±0.2 μmol m^(-2) s^(-1)).This resulted in significantly larger annual soil CO_2 emissions from the terrace tea and secondary forest,than from the forest tea plantation. It is likely that these differences in the SR rates are due to the 0.5times lower soil organic carbon concentrations in thetop mineral soil in the forest tea plantation, compared to the terrace tea plantation and secondary forest.Furthermore, we suggest that the lower sensitivity to temperature variation in the forest tea soil is a result of the lower soil organic carbon concentrations. The higher SR rates in the terrace tea plantation were partly due to weeding events, which caused CO_2 emission peaks that contributed almost 10% to the annual CO_2 flux. Our findings suggest that moving away from heavily managed tea plantations towards low-input forest tea can reduce the soil CO_2 emissions from these systems. However, our study is a casestudy and further investigations and upscaling are necessary to show if these findings hold true at a landscape level.

he Design of Efficient Heat Transfer Based on Flat Plate Solar Water Heater

This is an improved design based on the existing plate type solar water heaters. It aims at making full use of solar energy. To fully absorb radiation, it absorbs coating selectively by adopting the magnetron sputtering technology AL-N/AL. this design conduct heat through aluminum material which can reduce the cost meanwhile conduct heat effectively. To ensure the quality of the water at the same time improve the utilization rate of solar energy, this design use phase change for second heat exchange. Take Shanghai for example, where this design and heat transfer model are applied, the average efficiency of water heaters can achieve 68%, which has proven the feasibility of the design. In a word, this design can achieve the goal of energy conservation and emissions reduction and has broad market prospects.

Reaction heat-driven CO2 desorption during CO oxidation on Au(997) at low temperatures

Adsorption and reaction of CO and CO2 were studied on oxygen-covered Au（997） surfaces by means of temperature- programmed desorption/reaction spectroscopy. Oxygen atoms （O（a）） on Au（997） enhances the CO2 adsorption and stabilizes the adsorbed COe（a）, and the stabilization effect also depends on the CO2（a） coverage and involved Au sites. CO2（a） desorp- tion is the rate-limiting step for the CO＋O（a） reaction to produce CO2 on Au（997） at 105 K and exhibits complex behaviors, including the desorption of CO2（a） upon CO exposures at 105 K and the desorption of O（a）-stabilized CO2（a） at elevated temperatures. The desorption of CO2（a） from the surface upon CO exposures at 105 K to produce gaseous CO2 depends on the surface reaction extent and involves the reaction heat-driven CO2（a） desorption channel. CO＋O（a） reaction proceeds more easily with weakly-bound oxygen adatoms at the （111） terraces than strongly-bound oxygen adatoms at the （111） steps. These re- sults reveal complex rate-limiting COe（a） desorption behaviors during CO＋O（a） reaction on Au surfaces at low temperatures which provide novel information on the fundamental understanding of Au catalysis.