مهدی اشجعی
استاد، دانشکده مهندسی مکانیک، پردیس دانشکده‌های فنی، دانشگاه تهران
[ 1 ] - بررسی عملکرد حرارتی و هیدرودینامیکی جریان جت برخوردی نانوسیال آب- Al2O3 در چاه حرارتی صفحه- پینی
در این پژوهش، عملکرد هیدرودینامیکی و مشخصات انتقال‌حرارت نانوسیال آلومینا در چاه‌حرارتی مینیاتوری صفحه- پینی بصورت عددی و آزمایشگاهی مورد بررسی قرار‌گرفت. چاه حرارتی از جنس آلومینیوم با دستگاه CNC ساخته و در محفظه‌ی پلکسی‌گلاس تعبیه شد. شار حرارتی ثابت kW/m2 125 به کف چاه حرارتی وارد گردید. محدوده عدد رینولدز بین 9/156 و 25/589 می‌باشد. چاه حرارتی به صورت سه بعدی مدل شد و با حل ان...
[ 2 ] - Improving the natural convective heat transfer of a rectangular heatsink using superhydrophobic walls: A numerical approach
The effect of utilizing superhydrophobic walls on improving the convective heat transfer in a rectangular heatsink has been studied numerically in this paper. The vertical walls were kept at isothermal hot-and-cold temperatures and horizontal walls were insulated. The boundary condition on the walls was: no-slip for regular, and slip (with slip length of 500 µm) for superhydrophobic walls. By c...
[ 3 ] - Conceptual design of a super-critical CO2 brayton cycle based on stack waste heat recovery for shazand power plant in Iran
Conceptual design of a waste heat recovery cycle is carried out in attempt to enhance the thermal efficiency of a steam power plant. In the recovery system, super-critical an CO2 is employed as the working fluid operating in a Brayton cycle. Low grade heat rejected by the flue gases through the stack is used as the primary heat source, while a secondary heat exchanger utilizes th...
[ 4 ] - Numerical Investigation on Slot air Jet impingement Heat Transfer between Horizontal Concentric Circular Cylinders
A numerical study has been carried out for slot air jet impingement cooling of horizontal concentric circular cylinders. The slot air jet is situated at the symmetry line of a horizontal cylinder along the gravity vector and impinges on the bottom of the outer cylinder which is designated as θ=0°. The outer cylinder is partially opened at the top with a width of W=30mm and is kept at constant t...
[ 5 ] - شبیه‌سازی عددی و بهینه سازی انتقال حرارت نانوساختار مغناطیسی در یک کانال در حضور یک میدان مغناطیسی غیریکنواخت
در مقاله حاضر، تأثیر یک منبع میدان خارجی غیریکنواخت بر انتقال حرارت جابجایی اجباری نانوسیال مگنتیت (فروسیال) داخل کانالی با سطح گرم، به‌صورت عددی مورد مطالعه قرار گرفته است. هدف اصلی تأکید بر اهمیت موقعیت میدان مغناطیسی و بررسی احتمال افزایش انتقال حرارت از طریق یافتن مکان بهینه منبع میدان مغناطیسی است. مشاهده شد که میدان مغناطیسی گردابه‌هایی ایجاد کرده و بر ضخامت لایه مرزی حرارتی و تغییرات عدد...
[ 6 ] - Thermoeconomic analysis of a hybrid PVT solar system integrated with double effect absorption chiller for cooling/hydrogen production
A novel solar-based combined system which is consisting of a concentrated PV, a double effect LiBr-H2O absorption chiller, and a Proton Exchange Membrane (PEM) is proposed for hydrogen production. A portion of the received energy is recovered to run a double effect absorption chiller and the rest is turned into electricity, being consumed in the PEM electrolyzer for hydrogen producti...
[ 7 ] - Enhanced performance and reduced payback period of a low grade geothermal-based ORC through employing two TEGs
In this paper, a novel integrated system is proposed to improve the performance of a conventional low-grade geothermal-based organic Rankine cycle (ORC). The main idea is to utilize two TEG units to recover the waste heat of the condenser and geothermal brine. The proposed model is investigated and compared with simple ORC from the energy, exergy, and exergoeconomic viewpoints through the param...
[ 8 ] - A method for detecting bubbles in two-phase gas-liquid flow
Detecting bubble in two-phase flow has been a basic issue in two-phase flow systems. A new method for measuring the frequency of bubble formation is presented in this paper. For this purpose, an electronic device was designed and constructed which works based on a change in intensity of laser beam. For this purpose, continues light beam is embedded just above the needle, which is received by a ...
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