در هنگام جستجو کلمه در قسمت عنوان میتوانید کلمات مورد جستجو را با کاراکتر (-) جدا کنید.
کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Challenges in Nano and Micro Scale Science and Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Microchannel,Analytical solution,Non-ideal gaseous slip
- چکیده:
- چکیده انگلیسی: In this paper, the fully developed non-ideal gaseous slip flow in circular,parallel plates and rectangular microchannels is analyzed analytically by using Navier-Stokes equations to obtain the analytical exact solution.Van der Waals equation is used as the state equation of non-ideal gas. It is assumed that the flow is isothermal, incompressible, steady state, two-dimensional and fully developed,slip flow regime with consideration the first and second orders boundary conditions. It is developed the models for predicting the local and mean velocity, normalized Poiseuille number,and the ratio of density for the first and second orders boundary conditions.The results show that the rarefication process and Poiseuille number are a function of the Knudsen number and the cross-section geometry and Poiseuille number is independent of fluid material properties, velocity, temperature.Also, for circular microchannel,the rarefication process occurs faster than the others.
Keywords: Analytical solution, Non-ideal gaseous slip, Microchannel
In this paper, the fully developed non-ideal gaseous slip flow in circular,parallel plates and rectangular microchannels is analyzed analytically by using Navier-Stokes equations.The Van der Waals equation is used as the state equation of non-ideal gas. Also, it is assumed that the flow is isothermal, incompressible, steady state, two-dimensional and fully developed,slip flow regime with consideration the first and second orders boundary conditions.It is found that, density to inlet density ratio in non-ideal gas is different than ideal gas in length of microchannel under the same flow conditions and the type of microchannel geometry affect on gas behaviors.
Keywords: Analytical solution, Non-ideal gaseous slip, Microchannel- انتشار مقاله: 12-10-1397
- نویسندگان: Mahdi Motamedian,Ahmad Reza Rahmati
- مشاهده
- جایگاه : پژوهشی
- مجله: Challenges in Nano and Micro Scale Science and Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Lattice Boltzmann Method,Shan-Chen Method,Two-Phase Flow-Particle Interaction
- چکیده:
- چکیده انگلیسی: A huge number of deaths in the world are the direct or indirect consequence of a disease which is called atherosclerosis. The disease could be due to an artery blockage by the interaction of an externally second phase with a particle which is entered to the bloodstream. The effect of some most important physical and geometrical affecting parameters on the blockage time of a microchannel due to the impact of a particle and a second moving second phase is investigated. Shan-Chen Lattice Boltzmann multi-phase model is used in present study. It is investigated that the small change in the Capillary number does not affect the dynamics of the mechanism and the procedure steps significantly. But, smaller Capillary numbers cause breaking up the second phase in to more parts and with these smaller parts, the risk of small capillaries blockage in the arterial section of bloodstream decreases significantly. The blockage time will increase by an increase in the ratio of particle size to the channel width and the initial size of the second phase to channel width ratio has the highest effect on the blockage time.
- انتشار مقاله: 19-12-1397
- نویسندگان: Ramin Ehsani,Ahmad Reza Rahmati
- مشاهده
- جایگاه : پژوهشی
- مجله: Challenges in Nano and Micro Scale Science and Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Electroosmotic flow,KEYWORDS lattice Boltzmann,slip velocity boundary conditions
- چکیده:
- چکیده انگلیسی: The aim of the present work is to analyze the accuracy and to extend the capability of lattice Boltzmann method in slip EOF; a phenomenon which was previously studied by molecular dynamics and less considered by LBM. At the present work, a numerical experiment on boundary conditions of slip velocity is performed and the proportionality of slip with shear stress in electroosmotic pump is proved. Results show that LBM can capture the slip length in EOF with liquid operating fluid. Implementing slip velocity at the walls of a microchannel, the electroosmotic flow with adverse pressure gradient over a hydrophobic surface is investigated in view of mixing reduction. The fluid flow is assumed to be laminar, steady and viscous. Slip at the channel boundaries will decelerate the development process of the flow. Unlike no-slip condition, transverse change in velocity magnitude near the walls decreases and also more resistant pressure is required to create reverse centerline velocity; so mixing probability and performance of EOF pump can alter considerably.
- انتشار مقاله: 21-03-1397
- نویسندگان: Ahmad REza Rahmati,Hossien Khorasanizadeh,Mohammad Reza Arabyarmohammadi
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Advanced Design and Manufacturing Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: refrigeration,Ejector-expansion,Internal heat exchanger,Two-stage,Transcritical
- چکیده:
- چکیده انگلیسی: Performance of a two-stage multi-inter-cooling trans-critical CO2 refrigeration cycle containing internal heat exchanger, two intercoolers, ejector, and separator, has been analyzed after modification. In the present study, an internal heat exchanger has been included within this cycle for possible improvement in its cooling performance. The impacts of operational parameters such as gas cooler and evaporator temperatures and gas-cooler pressure, on cycle performance have been investigated. Results are validated against those available in the literature. Comparisons of the results show that there is excellent agreement between them. Obtained results showed that modified cycle improved the maximum coefficient of performance (COP max), by 20.58% compared to the internal heat exchanger two-stage TRCC cycle and 23.2% compared to multi-inter-cooling two-stage TRCC cycle with ejector expansion device. Also, the total exergy destruction rate of the improved cycle is between its rates of two original cycles.
- انتشار مقاله: 02-03-1396
- نویسندگان: Ahmad Reza Rahmati,Ali Gheibi
- مشاهده