分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The AP1000 with high safety is a generation III pressurized water reactor (PWR), its significant feature is passive safety system. However, its passive cooling can only maintain for 72 h and requires additional support from inside or outside the plant. To solve this problem, this study utilized the WGOTHIC software to calculate and analyze the water inventory in the passive containment cooling water tank under different conditions. The results show that when the cooling water inventory is 6553.78 m3, the AP1000 nuclear power plants can achieve long-term, completely passive cooling without any inside or outside the plant. The same outcomes occur when 65-mm-thick containment wall increases the design pressure rating to 0.6 MPa at the cooling water inventory of 5673 m3. Also, the AP1000 shield building was accordingly improved. An ANSYS analysis of the structural stability of the shield building with a 6000 m3 cooling water inventory confirmed that the new design can meet the requirements of the seismic design and the safe residual heat removal requirements of a large-scale PWR.
分类: 动力与电气工程 >> 工程热物理学 提交时间: 2017-06-22 合作期刊: 《热科学学报》
摘要: Effects of the uneven circumferential blade space on static characteristics and aerodynamic noise of a small axial flow fan are studied in this work. The blade angle modulation is adopted to design a series of unequally spaced fans, which have different maximum of modulation angular displacement. The steady flow is simulated by the calculations of Navier-Stokes equations coupled with RNG k-epsilon turbulence model, while the unsteady flow is computed with large eddy simulation. According to theoretical analysis, a fan with a maximum of modulation angular displacement of 6 is regarded as the optimal unequally spaced fan. The experiment of static characteristic is carried out in a standard wind tunnel and the aerodynamic noise of both fans is tested in a semi-anechoic room. Then, performances of the optimal unequally spaced fan are compared with those of the prototype fan. The results show that there is reasonable agreement between the simulation results and the experimental data. It is found that the discrete noise of the optimal unequally spaced fan is lower than that of the prototype fan at the near field monitoring point. This can be explained that the total pressure fluctuation of the optimal unequally spaced fan is much more regular than that of the prototype fan.
分类: 动力与电气工程 >> 工程热物理学 提交时间: 2024-03-26
摘要: We conduct an experimental investigation on the integration of film cooling for thermal protection in a 72-mm cylindrical rotating detonation engine (RDE). The cooling scheme employs the injection of cooling air through a series of cat-ear-shaped film cooling holes densely distributed along the outer wall of the cylindrical combustor. Our findings reveal successful initiation of the RDE and sustained propagation of the rotating detonation wave (RDW) when film cooling is activated.
分类: 动力与电气工程 >> 工程热物理学 提交时间: 2018-01-24 合作期刊: 《热科学学报》
摘要: This paper presents the study of the influence of channel geometry on the flow structure and heat transfer, and also their correlations on all the walls of a radial cooling passage model of a gas turbine blade. The investigations focus on the heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations for the heat transfer coefficient and the pressure drop used in the design of internal cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include a corner fillets, ribs with fillet radii and a special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which has very realistic features.
分类: 机械工程 >> 机械制造工艺与设备 提交时间: 2024-05-10
摘要: In this work, the sustainable machining approach is promoted by implementing the dry and minimum quantity lubrication (MQL) cooling conditions in the turning of duplex stainless steel. Initially, the turning experiments were performed under dry as well as MQL conditions and then, the influence of different positions of MQL nozzles on tribological and machining performance of 2205 duplex steel was investigated. The cutting parameters were kept fixed and the performance is evaluated in terms of surface roughness, micro-hardness, energy consumption, tool wear, machined surface microstructure and chips morphology. The results demonstrated that the highest average surface roughness values were obtained under dry conditions, with a value of 2.20 μm while MQL (flank + rake directions) produces the lowest surface roughness value of 1.55 μm with an improvement of 30%. Moreover, dual-jet MQL gives the lowest energy consumption (229 kJ) and tool wear (0.15 mm) with 23.67% and 52.38% enhancement, respectively.
分类: 工程与技术科学 >> 工业工程学 提交时间: 2024-05-09
摘要: Aluminium alloys are widely used in modern engineering applications such as automobile, aerospace etc because of its characteristics. The machining of aluminium alloys are also considered as difficult because of its sticky and soft nature, low thermal conductivity, strain hardening effect etc. The cooling conditions employed at cutting zone improved the machining performance but the resources, material consumption, skilled labor etc. are also required for performing the machining experiments. Therefore, the simulation of process parameters with the help of Finite Element Modelling (FEM) during machining is highly researched topic these days. In this work, anew practice from measurement science i.e., FEM simulation was performed with AdvantEdge software and the prediction models were developed for evaluating the cutting forces and cutting temperature while machining AA2024-T351 alloy under dry, liquid nitrogen (LN2) and carbon dioxide (CO2) conditions. Initially, the 3D turning model was developed and the results were compared with experimental findings. The results obtained from simulation model are very close with experimental results with minimum standard value of 0.67 (5.7%) for cutting forces and 4.58 (6.16%) for cutting temperature. Thus, it is worthy to mention that the 3D FE model is efficient and effective to predict and measurement results with minimum error.
分类: 动力与电气工程 >> 工程热物理学 提交时间: 2017-06-22 合作期刊: 《热科学学报》
摘要: The contribution deals with the experimental and numerical investigation of compressible flow through the tip-section turbine blade cascade with the blade 54 '' long. Experimental investigations by means of optical (interferometry and schlieren method) and pneumatic measurements provide more information about the behaviour and nature of basic phenomena occurring in the profile cascade flow field. The numerical simulation was carried out by means of the EARSM turbulence model according to Hellsten [5] completed by the bypass transition model with the algebraic equation for the intermittency coefficient proposed by Straka and Prihoda [6] and implemented into the in-house numerical code. The investigation was focused particularly on the effect of shock waves on the shear layer development including the laminar/turbulent transition. Interactions of shock waves with shear layers on both sides of the blade result usually in the transition in attached and/or separated flow and so to the considerable impact to the flow structure and energy losses in the blade cascade.
分类: 机械工程 >> 机械工程其他学科 提交时间: 2024-03-28
摘要: Increasing the transfer (HT) coefficient used in thermal industries is very important. Various methods are used to improve the efficiency of thermal heat HT so that maximum HT takes place in a smaller space. Ethylene glycol (EG) is generally used as an agent for convective HT. EG obtains energy from a hot source and discharges it to the required location. At present, the most consumption of EG is to produce engine cooling fluid. In the upcoming research, the TB of EG fluid in two-dimensional microchannels (MCs) has been investigated using molecular dynamics (MD) simulations, and the effect of variables such as MC dimensions and MC wall temperature (Temp) on the TB of the simulated fluid has been investigated. The results revealed that by increasing the Temp difference of the MC wall from 10 to 50 K, the maximum temperature (Max-Temp) and velocity (Max-Vel) of the target sample increased to 640.94 K and 0.024 Å/ps. It can be concluded that the increase in the cross-sectional area and the wall Temp difference leads to an increase in the HT rate in the MC.
分类: 生物学 >> 植物学 提交时间: 2018-01-22
摘要: Thermal dissipation probes were used to measure xylem sap flux density for a Schima superba plantation growing in the urban area of Guangzhou city, South China. Stand transpiration was calculated by multiplying mean sap flux density by total sapwood area. The peak of sap flux density occurred later in wet season than in dry season. The maximum of daily sap flux density was the highest of 59 g m-2 s-1 in July and August, and the lowest of 28 g m-2 s-1 in December. During November 2007- October 2008 and during November 2008-October 2009, the stand transpiration was 263.2 and 291.6 mm, respectively. In the study periods, stand transpiration in wet season (from April to September) could account for about 58.5% and 53.8% of the annual transpiration, respectively. Heat energy absorbed by tree transpiration averaged 1.4×108 and 1.6×108 kJ per month in the Schima superba plantation with the area of 2885 m2, and temperature could be reduced by 4.3 and 4.7 oC s-1 for 10 m3 air.
分类: 地球科学 >> 空间物理学 提交时间: 2016-05-04
摘要: We demonstrate an atom interferometer that uses a laser-cooled continuous beam of Rb-87 atoms having velocities of 10-20 m/s. With spatially separated Raman beams to coherently manipulate the atomic wave packets, Mach-Zehnder interference fringes are observed at an interference distance of 2L - 19 mm. The apparatus operates within a small enclosed area of 0.07 mm(2) at a bandwidth of 190 Hz with a deduced sensitivity of 7.8 x 10(-5) rad/s/root Hz for rotations. Using a low-velocity continuous atomic source in an atom interferometer enables high sampling rates and bandwidths without sacrificing sensitivity and compactness, which are important for applications in real dynamic environments. (C) 2015 AIP Publishing LLC.
分类: 机械工程 >> 机床技术 提交时间: 2024-05-10
摘要: Today, superalloys (also known as hard-to-cut materials) such as nickel, titanium and cobalt based cover a wide range of areas in engineering applications. At the same time, challenging material properties namely high strength and low thermal conductivity cause low quality in terms of cutting tool life and surface integrity of the machined part. It is important to improve the machinability of this type of materials by applying various methods in the perspective of sustainability. Therefore, current study presents surface integrity, tool wear characteristics and initiatives to improve them during the machining of superalloys. In this manner, it is outlined the surface integrity characteristics containing surface defects, surface roughness, microstructure alterations and mechanical properties. Also, tool wear mechanisms for example abrasive, adhesive, oxidation, diffusion and plastic deformation are investigated in the light of literature review. Finally, possible improvement options for tool wear and surface integrity depend on machining parameters, tool modifications, cooling methods and trade-off strategies are highlighted. The paper can be a guide for the researchers and manufacturers in the area of sustainable machining of hard-to-cut materials as explaining the latest trends and requirements.
分类: 地球科学 >> 大气科学 提交时间: 2022-03-02
摘要: The three-dimensional Weather Research and Forecasting (WRF) model is used to conduct sensitivity experiments during the landfall?of Typhoon Fitow (2013) to examine the impacts of cloud radiative processes on thermal balance. The vertical profiles of heat budgets, vertical velocity?and stability were?analyzed?to examine the physical processes responsible?for cloud radiative effects on?surface rainfall?for Typhoon Fitow (2013). The inclusion?of clouds reduced radiative cooling?in ice and liquid cloud layers via reducing outgoing radiation. The suppressed radiative cooling?reduces from ice cloud layers to liquid cloud layers. This was conducive to enhancing instability.?The decreased?instability was associated with the reduced?upward motions. The reduced upward motion led to?the decreased vertical mass convergence.?As a result, heat divergence was weakened to warm the atmosphere, this effects and the suppressed radiative cooling jointly?suppressed?net condensation and rainfall.?Furthermore, the reduced rainfall due to the cloud radiative effects was mainly associated with the reduced convective and stratiform rainfall. The reduced convective rainfall was associated with the reduced net condensation, whilst the reduced?stratiform rainfall was related to the constraint hydrometeor convergence.
分类: 地球科学 >> 地理学 提交时间: 2017-11-07 合作期刊: 《干旱区科学》
摘要: Salt expansion in sulfate saline soils that are wider distributed in northwestern China causes serious infrastructural damages under low-temperature conditions. However, the mechanism of salt expansion under low temperatures is not clear.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-11-02 合作期刊: 《热科学学报》
摘要: Steam pipelines applied in power units operate at high pressures and temperatures. In addition, to stress from the pipeline pressure also arise high thermal stresses in transient states such as start-up, shutdown or a load change of the power unit. Time-varying stresses are often the cause of the occurrence of fatigue cracks since the plastic deformations appear at the stress concentration regions. To determine the transient temperature of the steam along the steam flow path and axisymmetric temperature distribution in the pipeline wall, a numerical model of pipeline heating was proposed. To determine the transient temperature of the steam and pipeline wall the finite volume method (FVM) was used Writing the energy conservation equations for control areas around all the nodes gives a system of ordinary differential equations with respect to time. The system of ordinary differential equations of the first order was solved by the Runge-Kutta method of the fourth order to give the time-temperature changes at the nodes lying in the area of the wall and steam. The steam pressure distribution along pipeline was determined from the solution of the momentum conservation equation. Based on the calculated temperature distribution, thermal stresses were determined. The friction factor was calculated using the correlations of Churchill and Haaland, which were proposed for pipes with a rough inner surface. To assess the accuracy of the proposed model, numerical calculations were also performed for the thin-walled pipe, and the results were compared to the exact analytical solution. Comparison of the results shows that the accuracy of the proposed model of pipeline heating is very satisfactory. The paper presents examples of the determination of the transient temperature of the steam and the wall.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-11-02 合作期刊: 《热科学学报》
摘要: A hot wind tunnel of annular cascade test rig is established for measuring temperature distribution on a real gas turbine blade surface with infrared camera. Besides, conjugate heat transfer numerical simulation is performed to obtain cooling efficiency distribution on both blade substrate surface and coating surface for comparison. The effect of thermal barrier coating on the overall cooling performance for blades is compared under varied mass flow rate of coolant, and spatial difference is also discussed. Results indicate that the cooling efficiency in the leading edge and trailing edge areas of the blade is the lowest. The cooling performance is not only influenced by the internal cooling structures layout inside the blade but also by the flow condition of the mainstream in the external cascade path. Thermal barrier effects of the coating vary at different regions of the blade surface, where higher internal cooling performance exists, more effective the thermal barrier will be, which means the thermal protection effect of coatings is remarkable in these regions. At the designed mass flow ratio condition, the cooling efficiency on the pressure side varies by 0.13 for the coating surface and substrate surface, while this value is 0.09 on the suction side.
分类: 地球科学 >> 地理学 提交时间: 2021-04-30 合作期刊: 《干旱区科学》
摘要: This study aimed to explore the potential of developing a novel cooling system combining a greenhouse and an earth-tube heat exchanger (ETHE). In this system, greenhouse air is circulated through the underneath soil mass to use the deep-soil cooling effect. This was achieved through the following steps. First, soil temperature profile inside and outside the cultivated greenhouse was monitored for almost one year to study the possibility of using deep-soil coldness for cooling the greenhouse air. Second, a prototype ETHE was built to practically investigate the potential reduction in air temperature as the air flows inside the deep earth pipes. Third, a prototype greenhouse was erected to study the ETHE concept. Results from the first experiment revealed that soil temperature at a soil depth of 2.5 m inside the greenhouse offers good conditions to bury the ETHE. The soil temperature at this soil depth was below the maximum temperature (32°C) that most greenhouse crops can withstand. Results from the prototype ETHE showed a slight reduction in air temperature as it passed through the pipes. From the prototype of the integrated greenhouse and ETHE system, reduction in air temperature was observed as the air passed through the ETHE pipes. At night, the air was heated up across the ETHE pipes, indicating that the ETHE was working as a heater. We concluded from this study that greenhouses in arid climates can be cooled using the ETHE concept which would save a large amount of water that would otherwise be consumed in the evaporative coolers. Further investigations are highly encouraged.
分类: 天文学 >> 天文仪器与技术 提交时间: 2024-02-07 合作期刊: 《天文技术与仪器(英文)》
摘要:The Solar Close Observations and Proximity Experiments (SCOPE) mission, which has been proposed by the Yunnan Observatories, Chinese Academy of Sciences, aiming to operate at a distance of 5 to 10 solar radii from the Sun, plans to complete the in situ detection of the solar eruption process and observation of the magnetic field structure response. The solar flux received by the satellite ranges from 103 to 106 Wm−2, which poses challenges for thermal management of the solar arrays. In this work, the solar array cooling system of the Parker Solar Probe is discussed, the developments of the fluid loop technique are reviewed, and a research plan for a next-generation solar array cooling system is proposed. This paper provides a valuable reference for novel thermal control systems in spacecraft for solar observation.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-11-02 合作期刊: 《热科学学报》
摘要: Most evaporative cooling towers are arranged on building roof due to the limitation of space and noise, and acoustic barriers are always installed around cooling towers in practical applications. The existence of acoustic bathers and crosswind may affect the recirculation phenomenon which is directly related to the operating performance of cooling towers. In this study, a physical and mathematical computation model is proposed to research the crosswind and distance between acoustic bathers and inlet of cooling towers. Both sensible and latent heat are considered in this research. The reflux flow rate and performance ratio are obtained to evaluate the recirculation and operating performance, respectively. The results show that the higher the crosswind velocity, the larger the reflux flow rate, and the lower the performance ratio of cooling tower groups. For high crosswind velocity, the presence of acoustic barriers is useful to inhibit reflux and improve operating performance, especially for ICE cooling tower groups. In addition, the optimum values are recommended for LiBr/ICE cooling tower groups in the research cases The variation of reflux flow rate and performance ratio with the acoustic bathers' distance presents a parabolic tendency.
分类: 天文学 >> 天文仪器与技术 提交时间: 2024-02-07 合作期刊: 《天文技术与仪器(英文)》
摘要:In this paper, the mission and the thermal environment of the Solar Close Observations and Proximity Experiments (SCOPE) spacecraft are analyzed, and an advanced thermal management system (ATMS) is designed for it. The relationship and functions of the integrated database, the intelligent thermal control system and the efficient liquid cooling system in the ATMS are elaborated upon. For the complex thermal field regulation system and extreme space thermal environment, a modular simulation and thermal field planning method are proposed, and the feasibility of the planning algorithm is verified by numerical simulation. A solar array liquid cooling system is developed, and the system simulation results indicate that the temperatures of the solar arrays meet the requirements as the spacecraft flies by perihelion and aphelion. The advanced thermal management study supports the development of the SCOPE program and provides a reference for the thermal management in other deep-space exploration programs.