Performances of the High Strength Low Heat Pump Concrete (HLPC)

The effects of mineral admixtures on fluidity,mechanical and hydrational exothermic behavior were studied.The results show that,double adding ways,i e,fly ash and slag were added at the same time,not only improves the fluidity of fresh concrete with low W/B and compensates the lower early compressive strength of harden concrete caused by high adding amount of fly ash, but also greatly reduces the highest temperature rise, exothermic rate and total heat liberation of 3 day of binder pastes in HLPC, and postponed the arrival time of the highest temperature rise. HLPC was prepared and applied to project practice successfully.

建筑节能设计Low-E玻璃窗的遮阳参数取值分析

节能外窗属于精密工业制品,也是建筑工程外围护结构的重要组成部分。为能降低房间内的夏季太阳得热,工程中通常采用低辐射Low-E玻璃外窗,但由于国家及各地区的技术规范对Low-E玻璃窗的参数取值不尽相同、审图机构的把握尺度不一、门窗厂家的加工技术水平参差不齐,为能解决Low-E玻璃外窗的遮阳参数取值和选型困难的问题,达到概念清晰、数据可靠、便于实施的目的,文中采用公式计算和查表对比的方法,对规范的遮阳参数概念作补充说明,同时结合江苏某住宅项目的工程实践,给出Low-E玻璃窗遮阳参数的取值原则和建议,并认为一般Low-E玻璃的自遮阳系数取值最高不应超过0.60。

Non-equilibrium Plasma Assisted Combustion of Low Heating Value Fuels

This paper describes the effects of non-equilibrium air plasma generated by a dielectric barrier discharge (DBD) on the combustion of low heating value fuels. The experimental results indicate that addition of a very small amount of energy to the air flow in the form of DBD significantly improves the flame stability. Moreover, main combustion characteristics such as flame propagation speed, combustion intensity and lean blow-off limits are also enhanced by the effect of plasma. Some active radicals such as excited O atom and excited N2 molecule are observed by spectrograph in the discharge area. Based on the results of numerical investigation we can conclude that these active radicals generated in discharge area can accelerate the production rate of active OH radical which plays a key role in the oxidation process of low heating value fuel, and thus the whole combustion process is accelerated.

A review of low-temperature heat recovery technologies for industry processes

The amount of low-temperature heat generated in industrial processes is high,but recycling is limited due to low grade and low recycling efficiency,which is one of the reasons for low energy efficiency.It implies that there is a great potential for low-temperature heat recovery and utilization.This article provided a detailed review of recent advances in the development of low-temperature thermal upgrades,power generation,refrigeration,and thermal energy storage.The detailed description will be given from the aspects of system structure improvement,work medium improvement,and thermodynamic and economic performance evaluation.It also pointed out the development bottlenecks and future development trends of various technologies.The low-temperature heat combined utilization technology can recover waste heat in an all-round and effective manner,and has great development prospects.

Anti-Crack Performance of Low-Heat Portland Cement Concrete

The properties of low-heat Portland cement concrete（LHC） were studied in detail. The experimental results show that the LHC concrete has characteristics of a higher physical mechanical behavior, deformation and durability. Compared with moderate-heat Portland cement（MHC）, the average hydration heat of LHC concrete is reduced by about 17.5%. Under same mixing proportion, the adiabatic temperature rise of LHC concrete was reduced by 2 ℃-3 ℃,and the limits tension of LHC concrete was increased by 10× 10^-6-15×10^-6 than that of MHC. Moreover, it is indicated that LHC concrete has a better anti-crack behavior than MHC concrete.

Experiment Study on Self-stress of High-strength, Low-heat and Micro-expansion Concrete-filled Steel Tube

The self-stress trial of the fifteen high-strength, low-heat andmicro-expansion concrete-filled steel tube(CFST)is introduced, andthe generating and distributing features of pre-stress and itsrelation to add- ing quantity of expansive agent, which providespersuasive dependences for optimal design of high-strength, low- heatand micro-expansion CFST were investigated, especially for the designof added quantity of expansive agent.

Optimizing Low-Temperature Heat Recovery in a Refinery Fluid Catalytic Cracking Unit Based on Pinch Analysis

In this paper, the research was focused on optimizing low-temperature heat recovery to adopt multi-effect distillation (MED) in desalination by pinch technology. And further analysis indicated that phase changes occurred during the heat recovery process. In such case, the feed stream was divided into two streams: the liquid feed stream and the gaseous feed stream. Through calculation, the optimal ΔTmin was established at 26 ℃, and the total cost of heat exchange process was only $1.098×106. By using the Problem Table Algorithm for pinch analysis, the temperature of the hot and the cold steams was 119 ℃ and 93 ℃, respectively. At a temperature higher than 119 ℃, all heat of the hot stream could not be cooled by the condenser, and the minimum heat load of utility (QH,min) was 440457.64 kW; and at a temperature below 93 ℃, all heat of the cold stream could not be provided by the heater, and the minimum cold load of utility (QC,min) was 1965993.85 kW. Finally, the synthesis of heat exchanger network was established through integrating two heat exchanger networks.

Feasibility Demonstrations of Liquid Turbine Power Generator Driven by Low Temperature Heats

Lower temperature waste heats less than 373 K have strong potentials to supply additional energies because of their enormous quantities and ubiquity. Accordingly, reinforcement of power generations harvesting low temperature heats is one of the urgent tasks for the current generation in order to accomplish energy sustainability in the coming decades. In this study, a liquid turbine power generator driven by lower temperature heats below 373 K was proposed in the aim of expanding selectable options for harvesting low temperature waste heats less than 373 K. The proposing system was so simply that it was mainly composed of a liquid turbine, a liquid container with a biphasic medium of water and an underlying water-insoluble low-boiling-point medium in a liquid phase, a heating section for vaporization of the liquid and a cooling section for entropy discharge outside the system. Assumed power generating steps via the proposing liquid turbine power generator were as follows: step 1: the underlying low-boiling-point medium in a liquid phase was vaporized, step 2: the surfacing vapor bubbles of low-boiling-point medium accompanied the biphasic medium in their wakes, step 3: such high momentum flux by step 2 rotated the liquid turbine (i.e. power generation), step 4: the surfacing low-boiling-point medium vapor was gradually condensed into droplets, step 5: the low-boiling-point medium droplets were submerged to the underlying medium in a liquid phase. Experiments with a prototype liquid turbine power generator proved power generations in accordance with the assumed steps at a little higher than ordinary temperature. Increasing output voltage could be obtained with an increase in the cooling temperature among tested ranging from 294 to 296 K in contrast to normal thermal engines. Further improvements of the direct current voltage from the proposing liquid turbine power generator can be expected by means of far more vigorous multiphase flow induced by adding solid powders and theoretical optimizations of heat and mass transfers.

Influence of heating rate on reactivity and surface chemistry of chars derived from pyrolysis of two Chinese low rank coals

A series of char samples were derived from pyrolysis of two typical low-rank coals in China(Shengli lignite and Shenmu bituminous coal) at low, medium and fast heating rates, respectively, to the same pyrolysis temperature 750 °C. Then these chars were characterized by means of thermogravimetric analysis and Fourier transform infrared spectrometer with the aim to investigate the influence of heating rate in pyrolysis process on gasification reactivity and surface chemistry of them. Besides, a homogeneous model was used to quantitatively analyze the activation energy of gasification reaction. The results reveal that Shengli lignite and its derived chars behave higher gasification reactivity and have less content of oxygen functional groups than Shenmu coal and chars. Meanwhile, chars derived from Shengli lignite at 50 °C/min and Shenmu coal at 200 °C/min have the greatest gasification reactivity, respectively. The oxygen functional groups in Shengli lignite are easily thermo-decomposed, and they are less affected by the heating rate, while that in Shenmu coal have a significant change with the variation of heating rate.In addition, there is no good correlation between the change of oxygen functional groups and that of the gasification reactivity of the derived chars from pyrolysis at different heating rates.

Integration of Low-level Waste Heat Recovery and Liquefied Nature Gas Cold Energy Utilization

分别地，二个新奇热周期基于 Brayton 周期和 Rankine 被建议它集成低级废热和液化性质气体(LNG ) 的恢复为发电的冷精力利用。在低级废热，低温度的 exergy 和 LNG 的压力 exergy 通过系统合成高效地被利用的地方，精力的串联利用在二个热周期被认识到。模拟加 10.2 用商业白杨被执行，并且结果被分析。与常规 Brayton 周期和 Rankine 相比，二个新奇周期在 exergy 效率带 60.94% 和 60% ，分别地并且 53.08% 和 52.31% 在热效率分别地。

Low-temperature heat capacities and standard molar enthalpy of formation of pyridine-2,6-dicarboxylic acid

This paper reports that the low-temperature heat capacities of pyridine-2,6-dicarboxylic acid were measured by a precision automatic calorimeter over a temperature range from 78 K to 380 K. A polynomial equation of heat capacities as a function of temperature was fitted by the least-squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K. The constant-volume energy of combustion of the compound was determined by means of a precision rotating-bomb combustion calorimeter. The standard molar enthalpy of combustion of the compound was derived from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound was calculated from a combination of the datum of the standard molar enthalpy of combustion of the compound with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.

Synthesis of SAPO-34/graphite composites for low temperature heat adsorption pumps

Low temperature heat adsorption pumps represent the innovative cooling systems, where cold is generated through adsorption/desorption cycle of water by a suitable adsorbent with good adsorption and high thermal conductive properties. In this work, the hydrothermal synthesis of zeolite SAPO-34 on thermal conductive grapbitic supports, aiming at the development of highly pertbrming adsorbent materials, is reported. The synthesis was carried out using as-received and oxidized commercial carbon papers, and graphite plate. Composites were characterized by XRD, SEM and also by a thermogravimetric method, using a Cahn microbalance. The water adsorbing capacity showed typical S-shape trend and the maximum water loading was around 25 wt%, a value close to water adsorption capability of pure SAPO-34. These results are very promising for their application in heat adsorption pumps.

Dual Phase Heat Treatment of Low-Alloy Steel

Dual phase heat treatment is an economical and effective way for improving the properties of low carbon steels and low-alloy steel materials. In this paper, the microstructures and mechanical properties of 20MnSi steel treated by different dual phase heat treatment have been studied. The results show that dual phase heat treatment with pre-quenching technique and then heating from room temperature to the critical zone can achieve finer and more homogeneous microstructure than that with pre-normalizing technique and then cooling from austenite zone to the critical zone. Among all factors affecting dual phase heat treatment, quenching temperature at the critical zone and tempering temperature play an important part in mechanical properties. Using proper dual phase heat treatment technique with computer optimized parameters, the yield strength, the elongation and impact toughness of 20MnSi can reach 860 MPa, 16% and 207 MPa respectively.

Cleanliness of Ti-bearing Al-killed ultra-low-carbon steel during different heating processes

During the production of Ti-bearing Al-killed ultra-low-carbon(ULC) steel, two different heating processes were used when the converter tapping temperature or the molten steel temperature in the Ruhrstahl–Heraeus(RH) process was low: heating by Al addition during the RH decarburization process and final deoxidation at the end of the RH decarburization process(process-Ⅰ), and increasing the oxygen content at the end of RH decarburization, heating and final deoxidation by one-time Al addition(process-Ⅱ). Temperature increases of 10°C by different processes were studied; the results showed that the two heating processes could achieve the same heating effect. The T.[O] content in the slab and the refining process was better controlled by process-Ⅰ than by process-Ⅱ. Statistical analysis of inclusions showed that the numbers of inclusions in the slab obtained by process-Ⅰ were substantially less than those in the slab obtained by process-Ⅱ. For process-Ⅰ, the Al_2O_3 inclusions produced by Al added to induce heating were substantially removed at the end of decarburization. The amounts of inclusions were substantially greater for process-Ⅱ than for process-Ⅰ at different refining stages because of the higher dissolved oxygen concentration in process-Ⅱ. Industrial test results showed that process-Ⅰ was more beneficial for improving the cleanliness of molten steel.

Numerical analyses and experiment investigations of an annular micro gas turbine power system using fuels with low heating values

This study investigates the effects of using fuels with low heating values on the performance of an annular micro gas turbine(MGT)experimentally and numerically.The MGT used in this study is MW-54, whose original fuel is liquid(Jet A1).Its fuel supply system is re-designed to use biogas fuel with low heating value(LHV).The purpose is to reduce the size of a biogas distributed power supply system and to enhance its popularization.This study assesses the practicability of using fuels with LHVs by using various mixing ratios of methane(CH4)and carbon dioxide(CO2).Prior to experiments,the corresponding simulations,aided by the commercial code CFD-ACE+,were carried out to investigate the cooling effect in a perforated combustion chamber and combustion behavior in an annular MGT when LHV gas was used.The main purposes are to confirm that there are no hot spots occurring in the liners and the exhaust temperatures of combustor are lower than 700°C when MGT is operated under different conditions.In experiments,fuel pressure and mass flow rate,turbine rotational speed,generator power output,and temperature distribution were measured to analyze MGT performance.Experimental results indicate that the presented MGT system operates successfully under each tested condition when the minimum heating value of the simulated fuel is approximately 50%of pure methane.The power output is around 170 W at 85000 r/min as 90%CH4 with 10%CO2 is used and 70 W at 60000 r/min as 70%CH4 with 30%CO2 is used.When a critical limit of 60%CH4 is used,the power output is extremely low. Furthermore,the best theoretical Brayton cycle efficiency for such MGT is calculated as 23%according to the experimental data while LHV fuel is used.Finally,the numerical results and experiment results reveal that MGT performance can be improved further and the possible solutions for performance im- provement are suggested for the future studies.

Analysis of the formation conditions and characteristics of interphase and random vanadium precipitation in a low-carbon steel during isothermal heat treatment

The characteristics of nanosized precipitates in steels depend on the heat-treatment parameters. The effects of characteristics of vanadium precipitates formed during isothermal heat treatment on the hardness of the ferrite matrix in low-carbon vanadium-alloyed steel were investigated through analysis of transmission electron microscopy images and microhardness measurements. The results show that, during isothermal holding in the temperature range from 675 to 750℃, only interphase precipitation occurs, whereas only random precipitation occurs in the ferrite matrix during holding at 600℃. Furthermore, during isothermal heat treatment between 600 and 675℃, both random and interphase precipitates occurred in the ferrite. Nanoscale vanadium carbides with different atomic ratios of vanadium(V) and carbon(C) were the dominant precipitates in the random and interphase precipitates. The sizes of random precipitation carbides were smaller than those of interphase ones. Also, the sample isothermally heat treated at 650℃ for 900s exhibited a higher hardness with a narrower hardness distribution.

A STUDY ON THE CHARACTERISTICS AND EFFECT OF THE LOW-FREQUENCY OSCILLATION OF THE ATMOSPHERIC HEAT SOURCE OVER THE EASTERN TIBETAN PLATEAU

There has been a lot of discussion about the atmospheric heat source over the Tibetan Plateau(TP)and the low-frequency oscillation of atmospheric circulation.However,the research on low-frequency oscillation of heat source over TP and its impact on atmospheric circulation are not fully carried out.By using the vertically integrated apparent heat source which is calculated by the derivation method,main oscillation periods and propagation features of the summer apparent heat source over the eastern TP(Q1ETP)are diagnosed and analyzed from 1981 to 2000.The results are as follows:(1)Summer Q1ETP has two significant oscillation periods:one is 10-20d(BWO,Quasi-Biweekly Oscillation)and the other is 30-60d(LFO,Low-frequency Oscillation).(2)A significant correlation is found between Q1ETP and rainfall over the eastern TP in 1985 and 1992,showing that the low-frequency oscillation of heat source is likely to be stimulated by oscillation of latent heat.(3)The oscillation of heat source on the plateau mainly generates locally but sometimes originates from elsewhere.The BWO of Q1ETP mainly exhibits stationary wave,sometimes moves out(mainly eastward),and has a close relationship with the BWO from the Bay of Bengal.Showing the same characteristics as BWO,the LFO mainly shows local oscillation,occasionally propagates(mainly westward),and connects with the LFO from East China.In summary,more attention should be paid to the study on BWO of Q1ETP.

Heat Transfer Characteristics of Work Fluid Including Phase Change Material That Flow into Heating Surface from Narrow Path

Use of the low temperature (less than 100°C) energy contributes to effective use of heat resources. The cost recovery by power generation is difficult by using an existing system (the binary cycle or the thermoelectric conversion element), because the initial investment is large. The final purpose of this research is development of the low temperature difference drive engine supposing use in a hot-springs resort as a power source for electric power generation. In order that a traveler may look at and delight a motion of an engine, it is made to drive at low-speed number of rotations. An engine cycle of this study is aimed at the development of Stirling cycle engine which can maintain high efficiency in small size. This kind of engine has simple structure;it brings low cost, and it is easy to perform maintenance. However, it is difficult to obtain enough output by this type of engine, because of its low temperature difference. This paper deals with the heat transfer characteristic that the working fluid including a phase change material flows into the heating surface from the narrow path. In order to increase the amount of the heat transmission, Diethylether is added to the working fluid. Diethylether is selected as a phase change material (PCM) that has the boiling point which exists between the heat source of high temperature and low temperature. The parameters of the experiment are additive amount of PCM, rotational speed of the displacer piston and temperature of heat transfer surface. It is shown that it is possible to make exchange of heat amount increase by adding phase change material. The result of this research shows the optimal condition of the difference in temperature in heat processing, number of revolutions, and addition concentration of PCM.