动压条件下的综放开采方案

水峪煤矿 710 3综放工作面上部 9#煤层已采 ,已受采动影响 ,其支护及放顶煤都有其特殊性。在现有条件下 ,对工作面的所需的支架载荷进行了计算 ,对现有支架进行了评价 ,并提出改造方案。设计了工作面的回采工艺 。

Properties of Bentonite Enhanced Loess and Laterite

Loess and laterite distributed widely in the northern and southern China cannot be directly used as the natural barrier to isolate the solid waste because of their high hydraulic conductivity. In this paper, they are enhanced by bentonite to improve their hydraulic performance. The impact of bentonite content and water content on compressive strength of the compacted soil was investigated. The effects of bentonite content, water content, dry density and hydraulic gradient on the hydraulic conductivity were studied in detail. For the laterite and the laterite with 8% of bentonite, the experimental results of hydraulic conductivity can be applied in the engineering design. However, for the loess and the bentonite enhanced loess, those of hydraulic conductivity can not be directly applied in the engineering design because their hydraulic performance does not comply with the Darcy's law. These experimental results have to be carefully modified before application.

Boiling Heat Transfer in Circulating Fluidized Beds

A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. To verify the model, experiments are conducted in a stainless steel column with 39mm ID and 2.0m height, in which the heat transfer coefficient is measured for different superficial velocities, steam pressures, particle concentrations and materials of particle. As the steam pressure and particle concentrations increase, the heat transfer coefficient in the bed increases. The heat transfer coefficient increases with the liquid velocity but it exhibits a local minimum.The heat transfer coefficient is correlated with cluster renewed model and two-mechanism method. The prediction of the model is in good agreement with experimental data.

Experimental Study on Calculation of Hydro-Geological Parameters for Unsteady Flow

After the linear analytical method of unsteady flow theory is further improved,an innovative and faster algorithm is introduced.The water storage in a confined aquifer is derived from the water transmissivity coefficient and the water-pressure conductivity coefficient.The water transmissivity coefficient is approximated by a Taylorseries expansion of drawdown,and the water-pressure conductivity coefficient is obtained by the average drawdown.In this algorithm,the distance of the observation points from the pumping well must be short.When the distance is as short as the radius of the main pumping well,the data of the drawdown difference between the sidewall and the center of pumping well are difficult to measure,but the same results can be achieved based on the assumption that the drawdown difference approximates to the drawdown of the observation wells at a radial distance from the pumping well according to the algorithm.Without the help of charts,this algorithm is more concise and efficient,which has been verified by the test of water pumping project in Tianjin Binhai International Airport.

Turbulent Heat Transfer and Pressure Drop in Tube Fitted with Square-cut Twisted Tape

Heat transfer,friction factor and thermal enhancement factor characteristics of a double pipe heat exchanger fitted with square-cut twisted tapes（STT） and plain twisted tapes（PTT） are investigated experimentally using the water as working fluid.The tapes（STT and PTT） have three twist ratios（y=2.0,4.4 and 6.0） and the Reynolds number ranges from 2000 to 12000.The experimental results reveal that heat transfer rate,friction factor and thermal enhancement factor in the tube equipped with STT are significantly higher than those fitted with PTT. The additional disturbance and secondary flow in the vicinity of the tube wall generated by STT are higher compared to that induced by the PTT is referred as the reason for better performance.Over the range considered,the Nusselt number,friction factor and thermal enhancement factor in a tube with STT are respectively,1.03 to 1.14,1.05 to 1.25 and 1.02 to 1.06 times of those in tube with PTT.An empirical correlation is also formulated to match with experimental data of Nusselt number and friction factor for STT and PTT.

Determination of consolidation behaviour of clay slurries

The main objective of this study was to determine the consolidation behaviour of clay slurries.A finegrained clay with high consistency limits(W_L = 180%,w_P= 120%) was investigated using conventional oedometer and bench-top centrifuge tests.Results indicated that the slurry had an apparent preconsolidation(due to initial conditions,electrochemical interactions,tortuous drainage,and thixotropic strength) from e = 5.7 to e = 5.5 followed by virgin compression.Likewise,the low hydraulic conductivity(10^(-10)-10^(-12) m/s) was due to low porosity(small pore throats) and high tortuosity(long flow paths).Unlike consolidation of soils,the c_v and m_v decreased with increasing σ' but increased with increasing e and k.The data from the two tests correlated well in the range of σ' = 10-65 kPa,e = 5.5-3.86,k= 1.7 × 10^(-10)-5×10^(-11) m/s,F_c = 1-40 MN.New equations were developed to correlate the consolidation parameters(e,σ',k) with F_c.The deviation of k beyond 40 MN(e = 4.65) was due to deviation from the initial straight line portion of the settlement curve in the centrifuge test.

Experimental Study on Heat Transfer and Pressure Drop of Micro-Sized Tube Heat Exchanger

A micro-sized tube heat exchanger(MTHE) was fabricated, and its performance in heat transfer and pressure drop was experimentally studied. The single-phase forced convection heat transfer correlation on the sides of the MTHE tubes was proposed and compared with previous experimental data in the Reynolds number range of 500—1 800. The average deviation of the correlation in calculating the Nusselt number was about 6.59%. The entrance effect in the thermal entrance region was discussed. In the same range of Reynolds number, the pressure drop and friction coefficient were found to be considerably higher than those predicted by the conventional correlations. The product of friction factor and Reynolds number was also a constant, but much higher than the conventional.

Effects of Mechanical Aeration on the Compaction and Hydraulic Conductivity of a Grassy Sward

In a golf course located at El Kantaoui, Sousse, Tunisia, this study was carried out over a sandy soil grassy sward to investigate the effects of mechanical aeration （perforation of the sward with an aerators machine called ＂Vertidrain＂） on its compaction and hydraulic conductivity. For this purpose, many soil cores were extracted using a 1.6 e.g. m effective width Verti-Drain aerator equipped with hollow spades spaced 65 e.g. mm apart. Aeration was performed at a rate of 350 holes/m2. Soil resistance to penetration and permeability were determined at the initial state before aeration as well as 10, 20, and 30 days after aeration. Compared to the initial state, the results showed that mechanical aeration greatly affects the grassy sward ground by reducing its resistance to penetration as 35% and 43% decrease in penetration resistance were noticed at 5 e.g. cm depth 10 and 20 days after aeration, respectively. Also, resistance to penetration decreased by 41% and 48% at 15 e.g. cm depth during the same two periods of time with a relatively constant moisture content. However, soil resistance to penetration at 5 and 15 e.g. cm depths only decreased by 21% and 26%, respectively. Regarding the soil hydraulic conductivity measured after aeration, a significant improvement at the 1% level with the method of variance analysis, was observed compared to that at the initial state （4.9 e.g. cm hl）. Indeed, the hydraulic conductivity was 12.5, 13, and 14.1 e.g. cm h-1 10, 20, and 30 days after aeration, respectively.

Experimental investigation of thermal performance characteristics of sintered copper wicked and grooved heat pipes:A comparative study

Heat pipes are most frequently used for thermal management solutions.Selection of right type of heat pipe for a specific scenario is utmost necessary for best outcomes.The purpose of this research is comparison of thermal performance characteristics of sintered copper wicked and grooved heat pipes,which are mostly used types of heat pipes.Distilled water filled heat pipes were tested through experimentation in gravity assisted position.Experimental outcomes have been compiled in terms of capillary pressure,operating temperature,thermal resistance and heat transfer coefficient.Capillary pressure is high in sintered heat pipes compared to grooved heat pipes irrespective of groove dimensions.Grooved heat pipes have lower operating temperature compared to sintered heat pipes at the same heat load.At 8 W,compared to sintered heat pipes,grooved heat pipes have 8.24% lower condenser surface temperature,4.41% lower evaporator surface temperature and 7.79% lower saturation temperature.Thermal resistance of sintered heat pipe is much lower than grooved heat pipe.The maximum relative difference of 63.8% was observed at 8 W.Heat transfer coefficient of sintered heat pipe was observed double compared to grooved heat pipe at 8 W heat load.Thermal resistance and hence heat transfer coefficient of sintered heat pipe change almost in a linear manner with respect to heat load but unexpectedly turning point is observed in thermal resistance and heat transfer coefficient of grooved heat pipe.Grooved heat pipes attain equilibrium much earlier compared to sintered ones.Varying heat loads from 4 to 20 W causes variation in equilibrium establishment time from 7 to 4 min for grooved and from 10 to 7 min for sintered heat pipes.

Pool Boiling Heat Transfer in Dilute Water/Triethyleneglycol Solutions

Boiling of water/triethyleneglycol(TEG)binary solution has a wide-ranging application in the gas processing engineering.Design,operation and optimization of the involved boilers require accurate prediction of boiling heat transfer coefficient between surface and solution.In this investigation,nucleate pool boiling heat transfer coefficient has been experimentally measured on a horizontal rod heater in water/TEG binary solutions in a wide range of concentrations and heat fluxes under ambient condition.The present experimental data are correlated using major existing correlations.In addition a correlation is presented for prediction of pool boiling heat transfer for the system in which the vapour pressure of one component is negligible.This model is based on the mass transfer rate equation for prediction of the concentration at the bubble vapor/liquid interface.Based on this prediction,the temperature of the interface and accordingly,the boiling heat transfer coefficient could be straightforwardly calculated from the known concentration at the interface.It is shown that this simple model has sufficient accuracy and is acceptable below the medium concentrations of TEG when the vapor equilibrium concentration of TEG is almost zero.The presented model excludes any tuning parameter and requires very few physical properties to apply.

Thermal performance of tubular heat exchanger with multiple twisted-tape inserts

The paper presents an experimental investigation on enhanced heat transfer and pressure loss characteristics by using single, double, triple, and quadruple twisted-tape inserts in a round tube having a uniform heat-fluxed wall. The investigation has been conducted in the heat exchanger tube inserted with various twisted-tape numbers for co- and counter-twist arrangements for the turbulent air flow, Reynolds number （Re） from 5300 to 24000. The typical single twisted-tape inserts at two twist ratios, y/w = 4 and 5, are used as the base case, while the other multiple twisted-tape inserts are aty/w = 4 only. The experimental results of heat transfer and pressure drop in terms of Nusselt number （Nu） and friction factor 00, respectively, reveal that Nu increases with the increment of Re and of twisted-tape number. The values of Nu for the inserted tube are in a range of 1.15-2.12 times that for the plain tube while f is 1.9-4.1 times. The thermal enhancement factor of the inserted tube under similar pumping power is evaluated and found to be above unity except for the single and the double co-twisted tapes. The quadruple counter-twisted tape insert provides the maximum thermal performance.

Radial heat transport in packed beds-I： Experimental investigation of heat transfer coefficients of pellets and monolith catalysts at atmospheric and high pressures

The effect of operating pressure on the radial heat transfer coefficients, in a non-adiabatic fixed packed bed was studied at atmospheric and higher pressures, The study was concerned with investigating the effect of the pressure on the radial thermal conductivity （K^r） and wall heat transfer coefficient （h~） for both pellets and monolith catalysts. The study included beds that were packed with pellets and monoliths, separately. The radial temperature distribution was measured at different beds heights and feed flow rates for both types of packing. Steady-state temperatures were measured using nine chromel-alumel thermocouples arranged on a stainless steel-cross. After temperatures were collected, the radial thermal conductivity and wall heat transfer coefficient were calculated using a two-dimensional pseudo-homogeneous model. The results showed that, the radial temperature profile at the entrance of the heating section was nearly even, and a constant temperature along the radius （0F/0r=0） taken as a boundary condition to solve the partial differential equation controlling the heat transfer. Temperature profiles obtained at elevated pressures were smoother at the center of the reactor and increased sharply near the wall, than profiles at atmospheric pressure. It could also be observed, that the radial temperature profiles in the center of the reactor using a monolith catalyst at elevated pressure were more even and smoother than those of pellets. Temperature profiles in fixed beds were found to be very sensitive to Ker and hw. In pressures between atmospheric and 10 bars, there was no change in the effective heat transport parameters （i.e. they are independent of pressure in this range）. Both parameters were strongly affected by the pressure changes, above 10 bars. For the same Reynolds number （Ker） increased by 27% and 53% at 11 and 20 bars, respectively, in pellets catalyst. And they increased by factors of 2.3 and 4, when the pressure increased to the same pressures, in monolith catalyst. On the other hand, the effect of pressure on （hw） was completely the opposite, h,~ for pellets and monolith catalysts were found to be decreasing with increasing the pressure. Moreover, both coefficients increased with the Reynolds number at all applied pressures. This increase was higher for pellets than it for monoliths.

Temperature in High Temperature SHPB Experiments

As an experimental technique, it’s desired that the temperature in specimen is uniform in high temperature split Hopkinson pressure bar (SHPB) experiments. However, the temperature in specimen decreases and the temperature of bars increases when specimen starts to contact with bars, which induces the nonuniform temperature distribution in specimen, and may result in inac-curacy of experimental results. In this paper, the temperature distributions of specimen and bars in high temperature SHPB experiments were investigated while the specimen was heated alone. Firstly, the temperature history of specimen was measured at different initial temperatures by ex-periments, then simulation was carried out. Simulation results were consistent with experimental results by adjusting the thermal contact coefficient between specimen and bars. By this way, the thermal contact coefficient and simulation results were validated, and the proper cold contact times of specimen and bars in high temperature SHPB experiments were discussed. Finally, the results were compared with those in references.