دانلود مقاله سلولهای خورشیدی باند متوسط : پیشرفتهای اخیر و جهتگیری های آینده Intermediate band solar cells: Recent progress and future directions
Extensive literature and publications on intermediate band solar cells (IBSCs) are reviewed. A
detailed discussion is given on the thermodynamics of solar energy conversion in IBSCs, the device
physics, and the carrier dynamics processes with a particular emphasis on the two-step inter-subband
absorption/recombination processes that are of paramount importance in a successful implementation
high-efficiency IBSC. The experimental solar cell performance is further discussed, which has been
recently demonstrated by using highly mismatched alloys and high-density quantum dot arrays and
superlattice. IBSCs having widely different structures, materials, and spectral responses are also
covered, as is the optimization of device parameters to achieve maximum performance.
دانلود مقاله لایه مرزی لودویگ پرانتل Ludwig Prandtl’s Boundary Layer
این مقاله خلاصه ای دربارۀ اهمیت دستاورد بزرگ قرن یعنی ئظریۀ لایه مرزی پروفسور لودویگ پرانتل و دانشجویانش از زبان دانشمند بزرگ ایرودینامیک پروفسور اندرسون می باشد. اندرسون معتقد است پرانتل می بایست برای این نظریۀ خود در علم فیزیک، جایزۀ نوبل دریافت می نمود.
دانلود مقاله فناوریهای مبدلهای حرارتی فشرده برای کاربردهای کوره های بازیاب گرما (رکوپراتورها )COMPACT HEAT EXCHANGER TECHNOLOGIES FOR THE HTRs RECUPERATOR APPLICATION
Modern HTR nuclear power plants which are now under development (projects GT-MHR, PBMR)
are based on the direct cycle concept. This concept leads to a more important efficiency compared to
the steam cycle but requires the use of high performance components such as an helium/helium heat
exchanger called recuperator to guarantee the cycle efficiency. Using this concept, a net plant
efficiency of around 50% can be achieved in the case of an electricity generating plant. As geometric
constraints are particularly important for such a gas reactor to limit the size of the primary vessels,
compact heat exchangers operating at high pressure and high temperature are attractive potential
solutions for the recuperator application. In this frame, Framatome and CEA have reviewed the
various technologies of compact heat exchangers used in industry. The first part of the paper will give
a short description of the heat exchangers technologies and their rcinges of application. In a second
part, a selection of potential compact heat exchangers technologies are proposed for the recuperator
application. This selection will be based upon their capabilities to cope with the operating conditions
parameters (pressure, temperature, flow rate) and with other parameters such as fouling, corrosion,
compactness, weight, maintenance and reliability.
دانلود مقاله مبدلها (تبادلگرها)/راکتورهای حرارتی:موضوعات، فناوریها و وضعیت کنونی Heat exchanger/reactors (HEX reactors): Concepts, technologies: State-of-the-art
Process intensification is a chemical engineering field which has truly emerged in the past few years and
is currently rapidly growing. It consists in looking for safer operating conditions, lower waste in terms of
costs and energy and higher productivity; and away to reach such objectives is to develop multifunctional
devices such as heat exchanger/reactors for instance.
This review is focused on the latter and makes a point on heat exchanger/reactors.
After a brief presentation of requirements due to transposition from batch to continuous apparatuses,
heat exchangers/reactors at industrial or pilot scales and their applications are described.
Contents
دانلود مقاله مروری بر تحقیقات درباره راههای افزایش انتقال حرارت در یک لوله حاوی نانوسیالات تحت شرط مرزی شار حرارتی ثابت Heat transfer augmentation in a tube using nanofluids under constant heat flux boundary condition: A review
In the last few decades, research on nanofluids has increased rapidly. Traditional heat transfer fluids with
order of nanometer sized particles (1–100 nm) suspended in them are termed as nanofluids. Nanofluids
have been proved as better heat transfer fluids despite of various contradictions in results by different
research groups. The aim of this article is to review and summarize the recent experimental and theoretical
studies on convective heat transfer in heat exchangers using constant heat flux boundary condition.
The use of different types of nanoparticles with different base fluids by different research groups has been
presented and compared. Further an overview of experimental results about heat transfer abilities of
hybrid nanofluids from available literature sources is also presented. Finally, the challenges and future
directions in which research can be further progress are discussed
دانلود مقاله مرور دقیقی بر پیشرفتهای اخیر در کاربرد نانوسیالات در دستگاههای انتقال حرارت Recent advances in application of nanofluids in heat transfer devices: A critical review
در این مقاله دربارۀ کاربردهای نانوسیالات در دستگاههای انتقال حرارت صحبت شده است.
This paper presents a critical review of heat transfer applications of nanofluids. The effects of nanoparticle
concentration, size, shape, and nanofluid flow rate on Nusselt number, heat transfer coefficient, thermal conductivity,
thermal resistance, friction factor and pressure drop from numerous studies reported recently are
presented. Effects of various geometric parameters on heat transfer enhancement of system using nanofluids
have also been reviewed. Heat transfer devices covered in this paper include radiators, circular tube heat exchangers,
plate heat exchangers, shell and tube heat exchangers and heat sinks. Various correlations used for
experimental validation or developed in reviewed studies are also compiled, compared and analyzed. The pros
and cons associated to the applications of nanofluids in heat transfer devices are presented in details to determine
the future direction of research in this arena.
دانلود مقاله مروری بر انتقال حرارت و جرم افزایش یافته در استخرهای خورشیدی با استفاده از نانوسیالاتEnhanced heat and mass transfer in solar stills using nanofluids: A review
در این مقاله دربارۀ افزایش انتقال جرم و حرارت در استخرهای خورشیدی (solar stills)با استفاده از نانوسیال صحبت شده است. مرور تحقیقات قبلی به خوبی در این مقاله انجام گرفته است.
دانلود مقاله مروری بر فناوریهای پایدار فعلی و آینده توربینهای گازی An overview of current and future sustainable gas turbine technologies
در این مقاله 36 صفحه ای، مروری بر فناوریهای وربینهای گازی در شرایط فعلی و در آینده ارائه شده است. انواع سیکلهای توربینهای گازی و مزایای هریک نیز بیان شده است.
دانلود مقاله مروری بر لوله های گرمایی حلقوی A Review of Concentric Annular Heat Pipes
در این مقاله مروری بر تحقیقات قبلی دربارۀ لوله های گرمایی معمولی و حلقوی وجود دارد. مطالعۀ آن برای دانشجویان علاقمند به فناوری Heat Pipe اکیداً توصیه می شود.
A detailed description of a concentric annular heat pipe (CAHP) operation is presented in low to moderate temperature
ranges (50–200◦C). The steady-state response of a CAHP to various heat fluxes in the evaporator and condenser sections
are discussed. Two-dimensional mathematical modeling of the fluid flow and heat transfer in the annular vapor space and
the wicks are described. The fundamental aspects and limitations of the operation of a CAHP are also discussed. Previously
used numerical and experimental approaches for the analysis of the CAHPs and some related concepts are reviewed. The
Navier-Stokes and similar equations are recommended for the simulation of fluid flow and heat transfer in the annular vapor
space and the wicks. A number of important concepts, such as two-phase flow, heat transfer in the heat pipe wicks, the
vapor–liquid interface conditions, design considerations, testing, and manufacture of a CAHP, are also briefly discussed.
The results of this research have shown that the available numerical and experimental data in the literature are sufficiently
accurate in many applications. However, new mathematical models and experimental works are needed for the better design
and manufacture of various types of CAHPs.
دانلود مقاله مروری بر هیدرودینامیک و کارایی شناگری دلفین Review of Dolphin Hydrodynamics and Swimming Performance
everything about dolphins hydrodynamics