Influence Of Temperature Difference Research Articles

Reasonable Paths of Construction Ventilation for Large-Scale Underground Cavern Groups in Winter and Summer

Forced ventilation or newly built vertical shafts are mainly used to solve ventilation problems in large underground cavern groups. However, it is impossible to increase air supply due to the size restriction of the construction roadway, resulting in ventilation deterioration. Based on construction of the Jinzhou underground oil storage project, we proposed both a summer ventilation scheme and winter ventilation scheme, after upper layer excavation of the cavern is completed and connected with the shaft. A three-dimensional numerical model validated with field test data was performed to investigate air velocity and CO concentration. Fan position optimization and the influence of temperature difference on natural ventilation were discussed. The results show that CO concentration in the working area of the cavern can basically drop to a safe value of 30 mg/m3 in air inlet and exhaust schemes after 10 min of ventilation. Since there is inevitably a back-flow in the winter ventilation scheme, it is necessary to ensure that airflow is always moving towards the shaft. Optimal placement of the axial flow fan at the shaft bottom is on the central axis of the cavern, 5 m away from the shaft. The greater the temperature difference, the better the natural ventilation effect of the shaft. The natural ventilation effect of the shaft as an outlet in winter, is better than that of the shaft as an inlet in summer.

Influence of temperature difference on wetting characteristics of insulators

When polluted insulators get wet, the flashover voltage will decrease dangerously, threatening the stability of the power grid. It is known that moisture is a necessary condition for the pollution flashover accident, for a great deal of research has been carried out concerning the effect of humidity on the moisture of insulators. As the climate in the inland area is dry and the humidity is low, the pollution flashover accident tends to occur early in the morning, when condensation on the surface of the insulator is the most serious due to the temperature difference between the insulator and ambient air. In order to study the effect of temperature difference on pollution layer wetting process, and improve the accuracy of the condition assessment and flashover alarming, this paper analyzes the source, the existence form and the variation tendency of the water absorption of the polluted layers under the temperature difference based on the leakage current of insulators. In addition, for verifying the effects of the temperature difference during the wetting process of the pollution layers quantitatively, a series of laboratory tests have been performed in a multifunction artificial climate chamber. The results indicate that the water absorption of the polluted layer is directly proportional to the temperature difference under the medium humidity, which may provide some valuable reference for the on-line monitoring of insulator contamination in inland arid areas.

Experimental and numerical study of Bondura® 6.6 PIN joints

Pin joints are widely used in heavy-duty machinery such as aircrafts, cranes and offshore drilling equipment to transfer multi-dimensional shear forces. Their strength and service life depend on the clamping force in the contact region that is provided by interference fits. Though the interference fits provide full contact at the pin-hole interface under pretension loads, the contact interface reduces when the pin is subjected to an external load and hence a smaller contact surface leads to dramatic increase of the contact stress. The PIN joint of Bondura® Technology, investigated in this study, is an innovative solution intended to reduce the slack at the contact surface of the pin joint of heavy-duty machinery by using tapered sleeves on each end of the PIN. The study is aimed to better understand the contact pressure build-up and stress distribution in the supporting contact surface under pre-loading of the joint and the influence of temperature difference between part assembly and operation conditions. Numerical simulation using finite element method and diverse experimental tests were conducted. The numerical simulation and the test results, particularly the tests conducted with lubricated joints, show good conformance.

The influence of temperature differences in moist environments on surface discharges on solid insulation

The electric breakdown strength of insulating surfaces in HV systems is known to be greatly affected by moisture deposited on the surface. This has been known for decades in relation to HV outdoor insulation. Another application range, where breakdown voltages as a function of moisture and temperature are relevant is the offshore industry. Subsea applications of high voltages systems can mean harsh temperature conditions in connection with moist environments, such that electrical breakdown conditions in these environments need special focus.For gas insulated systems the moisture level is normally kept at a preferred minimum to avoid accumulation of condensation on the insulating surfaces, in particular on highly stressed areas.In this paper has been investigated the correlation between the electric flashover voltage of an insulating surface in moist environments and the condensation process on the insulating surface, as dependent on the dynamic moisture/temperature conditions.Under extreme environmental conditions, rapid temperature fluctuations can occur and cause accumulation of water droplets on surfaces. A series of tests were conducted on an insulation sample in air, showing the flashover voltage as a function of the temperature difference between gas and insulating surface.The breakdown field was, as expected, dependent on the formation of condensation on the surface. At high moisture content in the gas no relation between temperature gradient and flashover voltage was found, at moderate moisture the dependency did not give a clear picture.

Electrode connection optimization for both temperature difference and purification of lanthanum rod during solid-state electrotransport

In order to solve the problem of large temperature difference between the center and ends of the metallic rod in the purification process of solid-state electrotransport (SSE), three types of electrode connections of tantalum and the corresponding rods of metallic lanthanum were designed, the temperature distributions of three kinds of rod were measured, and the influence of temperature difference on the purification effect of solid-state electrotransport was investigated. The results indicate that the maximum temperature difference of the rod will be significantly reduced through decreasing the cross section of electrode connection to make its unit length resistance close to that of rod, or increasing the unit length resistance of the section at both ends of the rod. When these two measures are adopted at the same time, the effect of decreasing rod temperature difference is the best in the present study, and the maximum temperature difference of the rod can be reduced to 29 °C when the maximum temperature of the rod is 820 °C. The migration velocity of the impurities at rod ends can be obviously improved after the rod temperature difference is reduced, which enables the purification effect and efficiency of solid-state electrotransport to be greatly raised; it is also found that the major impurities iron in metallic lanthanum migrates more easily than oxygen and carbon during the purification of metal lanthanum with solid-state electrotransport.

Acoustic response of Helmholtz dampers in the presence of hot grazing flow

Thermoacoustic instabilities are high amplitude instabilities of premixed gas turbine combustors. Cooled passive dampers are used to attenuate or suppress these instabilities in the combustion chamber. For the first time, the influence of temperature differences between the grazing flow in the combustor and the cross-flow emanating from the Helmholtz damper is comprehensively investigated in the linear and nonlinear amplitude regime. The flow field inside the resonator and in the vicinity of the neck is measured with high-speed particle image velocimetry for various amplitudes and at different momentum-flux ratios of grazing and purging flow. Seeding is used as a tracer to qualitatively assess the mixing of the grazing and purging flow as well as the ingestion into the neck of the resonator. Experimentally, the acoustic response for various temperature differences between grazing and purging flow is investigated. The multi-microphone method, in combination with two microphones flush-mounted in the resonator volume and two microphones in the plane of the resonator entrance, is used to determine the impedance of the Helmholtz resonator in the linear and nonlinear amplitude regime for various temperatures and different momentum-flux ratios. Additionally, a thermocouple was used to measure the temperature in the neck. The acoustic response and the temperature measurements are used to obtain the virtual neck length and the effective area jump from a detailed impedance model. This model is extended to include the observed acoustic energy dissipation caused by the density gradients at the neck vicinity. A clear correlation between temperature differences and changes of the mass end-correction is confirmed. The capabilities of the impedance model are demonstrated.

Study of Diffusion Instability in Ternary Gas Mixtures under Nonisothermal Conditions

The main objective of this article is to investigate the effect of heating (from below or above) on stability of mechanical equilibrium in binary and ternary gas mixtures. Three series of experiments on instabilities in are reported gaseous diffusion. In one series occurrence of convective flows under diffusive mixing are investigated in the systems N2O . The temperature difference when the transition between the diffusion and the convective processes happen is higher at the bottom arrangement of N2O. In the second series the influence of temperature difference are studied in the mixture !!#$$$#!$$$%# !#& '# $#$ !!#$$$#$(##$&$ )*+*), (-# $%$ #$#& %$ -!$$ !$$ %# ) . !#/ ##%% Linear stability theory is applied to determine the boundary of transition from the state of diffusion to the region of convection. The results of numerical study are in good agreement with the experiments.

An Analytical Solution to Temperature Distribution of Single-Row-Piped Freezing with Different Pipe Surface Temperatures

Artificial ground freezing method is now widely used in many kinds of municipal projects. The existing formulas to calculate the temperature field distribution of single-row piped freezing are all based on the conditions that the temperature of all freezing pipes are equivalent. In this paper, analytical solution to steady-state temperature field of single-row piped freezing with different adjacent pipe surface temperatures was derived based on thermal potential superposition method. And discussions are made to analyze the influence of temperature difference between adjacent pipes and freezing time on temperature distribution of frozen soil.

Influence of Temperature Difference on Front End Bending in Hot Slab Rolling

Front end bending often occurs in the heavy plate mills and roughing stands, which reduce productivity efficiency and the quality of the plates considerably. The effect of temperature difference between top and bottom surfaces of slab and reduction ratio on front end bending was investigated by 3D FEM and the mathematical model was induced. The hexahedral mesh was generated by HyperMesh and embed into the DEFORM system. The results show that the temperature difference leads to the asymmetric distribution of equivalent stress, strain and strain rate in the deformation zone. With the increment of temperature difference and reduction ratio the slab head bends more significant. Additionally, the slab front end perhaps bends to higher temperature side in double phase rolling because of resistance of deformation with different phase. Reducing temperature difference, reducing reduction ratio and avoiding double phase rolling is benificial to reduce front end bending in hot slab rolling.

Elastic foundation effect on nonlinear thermo-vibration of embedded double-layered orthotropic graphene sheets using differential quadrature method

In this article, transverse nonlinear vibration of orthotropic double-layered graphene sheets embedded in an elastic medium (spring and shear constants of the Winkler and Pasternak models) under thermal gradient is studied using nonlocal elasticity orthotropic plate theory. The equations of motion are derived based on application of Hamilton’s principles. These are coupled, two-dimensional and time-dependent equations, which cannot be solved analytically due to their nonlinear terms. Hence, differential quadrature method is employed to solve the governing differential equations for the two boundary conditions of simply and clamped support in all four sides. The plots for the ratio of nonlinear to linear frequencies versus maximum transverse amplitude for armchair and zigzag graphene sheet structures are presented to investigate the effects of nonlocal parameters, Winkler and Pasternak effects, temperature, and various aspect ratios. The study also indicates that the nonlinear effect represented by nonlinear frequency ratio is considerable at lower Winkler and Pasternak constants, length aspect ratio and thickness aspect ratio while it might be neglected for higher values of these parameters. Regarding the influence of temperature difference on support type, with increased temperature difference, nonlinear frequency ratio increases when the graphene sheet is simply supported, but for clamped one, no specific change in nonlinear frequency ratio is observed.

Separation of Fine Particles from Gases in Wet Flue Gas Desulfurization System Using a Cascade of Double Towers

Separation of fine particles from coal-fired flue gas by vapor heterogeneous condensation was investigated experimentally in a wet flue gas desulfurization (WFGD) system using a cascade of double towers. The supersaturated vapor environment can be achieved in two ways. The influences of flue gas relative humidity and the temperature difference between the flue gas and the desulfurization liquid at the inlet of the main tower on the collection efficiency were investigated in this paper. The results show that high collection efficiencies can be obtained by this separation process and the collection efficiency is higher than that of single tower WFGD system. Flue gas relative humidity at the inlet of the main tower can influence the separation of fine particles significantly. The collection efficiency is improved significantly by injecting steam among the rotating-stream-tray shutters and optimizing the temperature difference between the inlet flue gas of the main tower and the desulfurization liquid. The influences of temperature difference on the separation of fine particles include the following: the collection efficiency decreases with increases in the temperature of the desulfurization liquid (TL) in lower temperatures than that of the flue gas at the inlet of the main tower (TG), and the influence trend is contrary while TL is higher than TG. Particle collection efficiency also increases with increasing liquid/gas ratio in the main tower.

Influence of the Hysteretic Behaviour on Silt Loam Soil Thermal Properties

The aim of this research is to explore the influence of hysteresis on heat transport in soils under experimental laboratory conditions. The obtained results shown that, thermal properties as are volumetric specific heat capacity (Cv) and thermal conductivity (θ) showed a positive linear correlation with soil volumetric water content (θ). However, thermal diffusivity values (θ) shown divergences between heat transferred and soil moisture. A spatial-temporal hysteresis pattern was observed on the whole of the thermal properties. This fact was related with factors as: degree of saturation, the influence of temperature difference on the heat transport, and the geometry of the water layer around the particle.

Numerical Simulation of Oscillating Heat Pipe Heat Exchanger

Oscillating heat pipe is a new type high efficiency heat-transfer element. Its development and design attract increasing attention. This paper describes a numerical simulation for investigating on the flow and heat exchange performance of an oscillating heat pipe heat exchanger. The influences of the arrangement of heat pipe, the inlet temperature and the flux of hot air were explored. The results show that the heat exchange of staggered arrangement is more efficient than the aligned one. The influence of temperature difference on the heat exchanger by hot air flux is more than hot air inlet temperature.

Natural air convection and heat transfer at a heated horizontal surface

Results from experimental studies of free (natural) turbulent air convection and heat transfer during the heating of a horizontally placed nonisothermal disk are presented. The influence of temperature difference is analyzed, correlation between the parameters characterizing free convection of air above the disk and intensity of heat transfer is revealed, and it is shown that the heat transfer from the disk facing downward is significantly less intensive.

Influence of individual thermal shock parameters on stress generated in silicon nitride and its prediction

Influence of repeated thermal shock on the stress generated in silicon nitride, was determined by a new testing method. This method allows verification of temperature and stress progress obtained from a computer simulation. Input parameters were temperature, temperature difference, heating and cooling time. Output parameters were the mean stress and stress peaks of specific cycles. Two methods were used to compare the influence—a newly defined parameter of influence (PI) and a least square method. The results show a dominant influence of the temperature values, which is higher than the influence of temperature difference. The least squares method was also used to predict the value of stress, with coefficient of determination higher than 0.95.

443 SOFC-AMTECの複合モジュール化に関する性能解析(燃料電池,電力貯蔵,環境保全型エネルギー技術)

The alkali metal thermal to electric converter (AMTEC) is a device for the direct conversion of heat to electrical power. Operating hot-side temperatures of AMTEC cells are well compatible with those of solid oxide fuel cells (SOFC), so that the stacks of the SOFC can be directly coupled to hot-side of the AMTEC cells. The AMTEC cells would produce electrical power from released heat of the SOFC, as well as control the SOFC operating temperatures by modulating current of the AMTEC cell. A new honeycomb type AMTEC cell is discussed in this paper. The cell uses advanced beta"-alumina solid electrolyte (BASE) configurations to improve the device performance over the conventional tube BASE systems. Expected power densities and efficiencies were calculated. The influence of temperature differences between heat source and anode side electrode is also discussed for vaper-fed type and vaper-vaper-fed type cells.

Effects of Temperature on Deep Drawing of Sheet Metals

The influence of temperature on the flow stress and the uniform strain of steel, brass, aluminium and AISI 304 and 316 type stainless steels is determined by using uniaxial tensile tests. Sliding and stretching friction coefficients at several surface temperatures are measured for various sheets and lubricants using a bending under tension type strip drawing test. The validity of the results is verified by deep drawing experiments. The influence of temperature difference between the punch nose region and the flange on the drawing and fracture loads and on the limiting drawing ratio is determined.

Influence of Temperature Difference on Air Shutters for Fire Prevention

Influence of Temperature Difference on Air Shutters for Fire Prevention

Additional Factors Affecting the Transmission of Pea Enation Mosaic Virus by the Pea Aphid1,2

Tests were conducted to determine the influence of temperature differences, preinoculation starvation, inoculation probing times, and inoculation probing sites on the ability of the pea aphid, Acyrthosiphon pisum (Harris), to transmit pea enation mosaic virus (PEMV), a virus which possesses a circulative relationship with the vector. Aphids subjected to temperatures of 10°:10°C (10°C during a 24-hour acquisition access period and 10°C during the subsequent latent and inoculation probing periods) required a mean latent period (LP50) of 98.3 hours whereas those subjected to a 10°:20°C regime needed only a 45-hour LP50. Treatments of 20°:20°; 30° :20°; and 30°:30°C caused LP50 values of much less than 48 hours. Nearly all aphids, regardless of treatment, transmitted virus at least once during a week-long series of daily transfers to healthy plants; however, insects from the 30°:30°C group transmitted virus to significantly fewer plants during either 2-minute or 4-hour inoculation periods 7 days after virus acquisition than did aphids from any of the other treatments. Inoculative aphids that were starved for 4–8 hours prior to a 2-minute inoculation probing period (IPP) transmitted PEMV with significantly higher efficiency (83.7%) than did aphids starved for 16–20 hours (68.9%). Aphids starved 0–2 hours were intermediate in transmission efficiency (75.1%). Transmission efficiency during IPPs of 1, 5, and 10 min at various sites on garden pea, Pisum sativum L., seedlings in the 1-leaf stage and at random on plants in the preleaf stage was tested. Inoculation to the preleaf stage resulted in a mean transmission efficiency of 71.7%, data pooled from all IPPs, and transmission to this stage was significantly higher than to any of the sites tested (the ab- and adaxial surface of leaf and petiole, the stem, and the terminal bud) on the 1-leaf-stage plants, which ranged in pooled transmission efficiency from 17.5 to 42.7%. Significant differences were not detected on transmission in the average effect of IPP, pooled from all probing sites. Transmission to the youngest leaf on a pea seedling in the 2-leaf stage was significantly higher (36%) than to the other leaf (27%). Twenty-four-hour temperature treatments of 10°, 20°, and 30°C to inoculative pea aphids prior to a 1-min IPP had no significant effect on mean transmission efficiency; however, the 20°C treatment resulted in highest efficiency (60.9%). The length of salivary sheath deposited by aphids during 1-, 5-, and 10-minute probes on the ab- and adaxial surface of the petiole on 1-leaf-stage plants and on the stem of preleaf and 1-leaf plants was studied. No significance was detected among length of sheath deposited in any tissue. Thus, differences in transmission efficiency to these sites are not related to length of sheath. As expected, the average length of sheath produced during the 3 IPPs regardless of probing site were significantly different from one another (1 minute = 0.37 mm; 5 minutes = 1.16 mm; 10 minutes = 1.78 mm). Postinoculation temperature was found to influence symptom development. Only 30% of pea seedlings held in a greenhouse at 30–44°C after being probed for 2 minutes by inoculative aphids developed symptoms, whereas 67% of those held at 24–30°C became infected.

Influence of temperature differences in joined components made from dissimilar materials on the magnitude of thermomechanical strains

Influence of temperature differences in joined components made from dissimilar materials on the magnitude of thermomechanical strains