检索结果-南通市图书馆

In Tube Condensation:Changing the Pressure Drop into a Temperature Difference for a Wire-on-Tube Heat Exchanger

在线全文

学校读者我要写书评

暂无评论

Fluid Dynamics & Materials Processing 2023年第9期19卷 2201-2214页

作者： Louay Abd Al-Azez Mahdi Mohammed A.Fayad Miqdam T.Chaichan Energy and Renewable Energies Technology Center University of Technology-IraqBaghdad65035Iraq

A theoretical study based on the Penalty factor(PF)method by Cavallini et *** conducted to show that the pressure drop occurring in a wire-on-tube heat exchanger can be converted into a temperature difference for two types of refrigerants R-134a and R-600a typically used for charging refrigerators and *** following conditions are considered:stratiﬁed or stratiﬁed-wavyﬂow condensation occurring inside the smooth tube of a wire-on-tube condenser with diameter 3.25,4.83,and 6.299 mm,condensation temperatures 35℃,45℃,and 54.4℃ and cover refrigerant massﬂow rate spanning the interval from 1 to 7 kg/*** results show that the PF variation is not linear with vapor quality and attains a maximum when the vapor quality is 0.2 and 0.18 for the R-134a and R-600a refrigerants,*** PF increases with the refrigerant massﬂow rate if the inner diameter and saturation temperature constant,and it decreases on increasing the inner diameter to 6.299 mm for constant refrigerant massﬂow rate and saturation *** PF for R-600a is higher than that for R-134a due to the lower saturation pressure in theﬁrst ***,a stratiﬁedﬂow produces higher PF in comparison to the annularﬂow due to the effect of the surface tension.

关键词： Condensation penalty factor pressure drop temperature difference two-phase wire condenser

Numerical simulation on centrifugal pump compressible flow field with different gas volume fractions

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

排灌机械工程学报 2019年第2期37卷 106-111,129页

作者： WANG Like LIAO Weili LU Jinling LUO Xingqi RUAN Hui ZHAO Yaping WANG Jing Institute of Water Resource and Hydro-electric Engineering Xi'an University of Technology

In order to study the influence of gas-liquid two-phase flow on the performance and internal flow field of a centrifugal pump,the steady three-dimensional flow with different gas volume fractions was simulated by applying the Reynolds-average N-S equation and mixture gas-liquid two-phase flow model,and the compressibility of gas was taken into consideration in the simulation. Then the centrifugal pump characteristic and the gas distribution law in different gas volume fractions were analyzed. The computational results show that gas volume fraction has a certain influence on the performance of the centrifugal pump,and the efficiency and head of the pump are on the decline with the increase of *** pressure in the impeller increases in the radial direction,but the pressure gradient in the flow direction is different under the different gas volume fractions. The gas volume is distributed mainly in the ipsilateral direction of impeller back shroud in the flow channel of the volute. On the suction side of the blade inlet there is an obvious low-pressure area,which causes bubbles agglutination and higher gas volume fraction. With the gas entering passage flow,gas volume fraction in the suction decreases and the pressure surface rises gradually. Higher gas volume fraction causes air blocking phenomenon in the flow passage and the discharge capacity reduces. The increase of gas volume makes the turbulent motion within the impeller more and more intense,which leads to more and more energy loss.

关键词： centrifugal pump Mixture model gas-liquid two-phase flow gas volume fraction compressibility

Experimental observation of deep crust fluid-NaCl aqueous solution at elevated temperatures and pressures and its significance

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1999年第7期44卷 654-660页

作者： Ronghua Zhang Shumin Hu Chinese Acad Geol Sci Open Res Lab Geochem Kinet Beijing 100037 Peoples R China

In order to reveal the nature of deep crust fluids, the phase relations of NaCI-saturated solution at high temperatures and pressures in a hydrothermal diamond anvil cell (HDAC)are investigated. Salinity of the solutions observed is about 35%—50%. The temperatures for the observation range from 25 to 850℃ and the pressures from 1 atm to about 1 GPa. A supercritical single phase, liquid phase (L), vapor phase (V), solid phase (H), L + H, H + V + L and the near-critical phases L + V can be observed. A two-phase (L + V) immiscibility field for the NaCI solution has been discovered to lie in a wide range of temperatures and pressures:from 250( ± 3) to 721℃. Within this field there are two parts, where the upper high temperature part of the two-phase regions is very unstable in character. It is possible to observe a 'critical phenomenon'. In some of our experiments an 'explosion' almost constantly occurred at the interface between the liquid and vapor phases, making the interface obscure, and a

关键词： two-phase immiscibility critical phenomenon solution structure.

Theoretical analysis of transient heat conduction in sand

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 1996年第8期39卷 855-863页

作者：梁新刚过增元徐云生 Department of Engineering Mechanics Tsinghua University Beijing 100084 China

A simplified two-phase system model, with the heat transfer between phases considered, is presented and applied to the transient heat conduction in sand. The analytical results show that the one-dimensional Fourier’s law is not applicable to the transient heat conduction at very short time and there is no thermal wave described by C-V equation in sand. The two-phase system model correlates with experimental data well. Each ?phase responds to heating at different speeds in composite material, and consequently results in a temperature difference between phases. This difference will cause heat transfer between phases, which can be regarded as a heat source or sink to other phase. It is certain that Fourier’s law cannot describe the transient heat conduction in sand if a one-dimensional problem with equivalent thermal diffusivity is assumed.

关键词： Fourier’s law two-phase system model thermal wave thermal conductivity.

Theoretical analysis of effect of solid phase on cavitation performance of deep-sea mining pump

在线全文

学校读者我要写书评

暂无评论

Journal of Chongqing University 2018年第2期17卷 49-54页

作者： XU Hai-Liang XU Cong WU Bo School of Mechanical and Electrical Engineering Central South UniversityChangsha 410083P.R.China State Key Laboratory of High Performance Complex Manufacturing Changsha 410083P.R.China

In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationship between gas and liquid phases are established by cavitation nucleon theory and mass energy equation as well as solid phase and liquid phase, and then we explored the relationship between gas phase and solid phase. The results show that the critical bubble radius and solid-phase concentration flow rate during the cavitation can be related to the liquid pressure. Eq.(19) show that the larger the solid particle concentration and the solid phase flow, the earlier the cavitation will occur, and pump anti-cavitation performance will decline.

关键词： deep-sea mining pump solid-liquid two-phase flow cavitation theoretical analysis

Reflection of Shock Wave in PUR Foam From Rigid Wall

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1994年第6期39卷 459-462页

作者：国相杰李仲发俞鸿儒 Institute of Mechanics Academia Sinica Beijing 100080 PRC

Keller proposed that a building, a mechanical installation or a body wrapped bya layer of foam plastics may be an efficient means for protection from damage ofblast wave. However, the practical effect was beyond expectation. For example, agunner wearing the foam plastics-padded waistcoat was injured more seriously by theblast wave from a muzzle. Monti took the foam plastics as homogeneous two-phasemedium and analyzed it with the theory of dusty flow. The obtained results showthat the peak pressure behind the reflected shock wave from rigid wall with foamcoat exceeds obviously that without foam coat under the same condition. Gel’fand,Patz and Weaver made experimental observations by means of shock tubes and veri-

关键词： shock wave foam two-phase flow shock tube.

THE EFFECT OF LIQUID PHYSICAL PROPERTIES ON DRIFT VELOCITY

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 1992年第1期 8-18页

作者：陈远明 Bell K. Kottowski H.M. Dept of Chem. Eng. Trianjin University 300072 Tianjin Joint Research Centre Commission of The European Communities Italy

Drift velocity is a very important paramcter for predictirg the pool volumetric void fraction. two-phase system of gas and high viscous liquids pool is encountered in various engineering applications. A review of the literature shows no data for explaining the effect of highly viscous liquids on the drift velocity. This paper’s analysis shows that there is a considerable influence. It is shown that the foaming behaviour of liquids is dependent on the surface properties. For some highly viscous liquids at a given superficial gas velocity, the viscosity changes with time. The effect of "foam" and "time" on drift velocity is clearly elucidated.

关键词： gas liquid two-phase flow pool void fraction drift velocity

Energy-Aware *** Routing in Delay Tolerant Mobile Sensor Network

在线全文

学校读者我要写书评

暂无评论

China Communications 2011年第8期8卷 87-97页

作者：张琳娟部帅 National Engineering Laboratory for Next Generation Internet Interconnection Devices Beijing Jiaotong University

The two-phase replication-based routing has great prospects for Delay Tolerant Mobile Sensor Network (DTMSN) with its advantage of high message delivery ratio, but the blind spraying and the low efficiency forwarding algorithm directly influences the overall network performance. Considering the characteristic of the constrained energy and storage resources of sensors, we propose a novel two-phase multi-replica routing for DTMSN, called Energy-Aware Sociality-Based Spray and Search Routing (ESR), which implements the quota-style message replication mechanism by utilizing the energy and speed information of sensors. In addition, based on the difference of history encounters, a sociality metric is defined to improve the forwarding efficiency in search phase. Simulation experiments show that ESR can reduce the message delay and improve the resource utilization while maximizing the message delivery ratio compared with the exiting popular two-phase routing protocols.

关键词： DTMSN multi-replica routing energy-aware sociality two-phase

Numerical Investigation on Flow Pattern of Air-Oil with Different Viscosities Lubrication

在线全文

学校读者我要写书评

暂无评论

Engineering（科研） 2017年第1期9卷 1-13页

作者： Qunfeng Zeng Jinhua Zhang Jun Hong Wenjun Su Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System and Fuli School of Food Equipment Engineering and Science Xi’an Jiaotong University Xi’an China State Key Laboratory for Manufacturing Systems Engineering Xi’an Jiaotong University Xi’an China

In the present work, the performance of oil-air two-phase flow under different lubricant oils was investigated. The simulation method was applied to study the influence of the oil viscosity on the flow pattern, velocity distribution and Re number in oil-air lubrication by FLUENT software with VOF model to acquire the working performance of oil-air lubrication for high-speed ball bearing. This method was used to obtain the optimum lubrication conditions of high-speed ball bearing. The optimum operating conditions that produce the optimum flow pattern were provided. The optimum annular flow was obtained by PAO6 oil with the low viscosity. Reynolds number influences the fluid shape and distribution of oil and air in pipe. The annular flow can be formed when Reynolds number is an appropriate value. The velocity distribution of oil-air two-phase flow at outlet was also discussed by different oil viscosities. The simulating results show that due to the effect of the oil viscosity and flow pattern the velocity decreased and expanded gradually close to the pipe wall, and the velocity increased close to the central pipe. The simulation results provide the proposal for the design and operation of oil-air two-phase flow lubrication experiments in the present work. This work provides a useful method in designing oil-air lubrication with the optimum flow pattern and the optimum operating conditions.

关键词： Oil-Air Lubrication Flow Pattern two-phase Flow Annular Flow