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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: International Journal of Advanced Design and Manufacturing Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Microchannel,Nano fluid,Forced Convection,Slip Velocity,Vertical Injection
- چکیده:
- چکیده انگلیسی: In this study, forced convection heat transfer of water/alumina Nano fluid in a rectangular microchannel with cross-flow injection is studied. The Nano fluid enters the microchannel with a temperature of 293 K and cools its walls. The upper wall of the microchannel is at constant temperature of 303 K. On the lower wall, there are two holes for injection of Nano fluid flow. Other parts of the microchannel wall are insulated. Slip velocity boundary condition is used for the walls of the microchannel. Simulations are performed for different injection velocities and the results are presented as velocity and temperature fields, and variation of the Nusselt number. The results show that the slip velocity on the channel wall and the Nusselt number increase by increasing the injection velocity. It is revealed that the Nusselt number is maximum at the channel entrance and decreases along the channel. After each injection, local Nusselt number increases due to the increase of the temperature gradient in the microchannel. Moreover, an optimal value for the ratio of the injection velocity to the inlet velocity is achieved using performance evaluation criteria (PEC). It is concluded that is an optimal value of the injection velocity, leading to maximum PEC.
- انتشار مقاله: 15-08-1398
- نویسندگان: Afshin Ahmadi Nadooshan,Afshin Shiriny,Morteza Bayareh
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Advanced Design and Manufacturing Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Implicit method,Building,Composite Wall,Fluid Volume Fraction,Latent heat,PCM
- چکیده:
- چکیده انگلیسی: Phase Change Materials (PCMs) have been the subject of many researches in recent years due to the storage and release of energy at low temperature ranges. PCMs store or releasing a large amount of energy at a constant temperature range leads to saving energy. In this paper, the numerical modelling of a multilayer composite wall including PCM located on the southern side of a building is carried out using an implicit method. The data correspond the fifteenth day of each month in Tehran. The governing equations are discretized by the implicit Crank Nicolson method and solved by iteration method using MATLAB software. Finally, the location and volume fraction of PCM in the wall of the building are studied to achieve maximum efficiency. The results show that the effect of latent and sensible heat results in a reduction in the input heat flux and thermal load to the building. The optimum location for the PCM layer is the middle layer of the composite wall to reduce the heat transfer rate inside the building. In addition, it is found that the PCM volume fraction in gypsum does not have a significant effect on the thermal performance of the multi-layer composite wall. Hence, low volume fraction reduces the costs without affecting the thermal performance of the building.
- انتشار مقاله: 16-01-1398
- نویسندگان: Arezoo Soleimani Dashtaki,Afshin Ahmadi Nadooshan,Afshin Abedi
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Advanced Design and Manufacturing Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: optimization,Reynolds Number,Constructal Theory,Forced Convection,Needle-Shaped Fins
- چکیده:
- چکیده انگلیسی: In the present paper, the constructal theory is employed to determine the optimal configuration of three rows of needle-shaped fins. The heat transfer across the fins is due to laminar forced convection. Second order upwind scheme is used for discretization of the diffusion terms of governing equations. The pressure–velocity coupling is performed using the SIMPLE algorithm. The heat transfer is optimized subject to constant fin volume. The effect of Reynolds number and thermal conductivity on the optimal configuration is investigated. The results obtained from the present simulations are in good agreement with the numerical results. The results show that pin–fins flow structure leads to the best performance when the pin–fin diameters and heights are non-uniform. At Re = 100 and 200, the optimal value of is 1.3. It is revealed that at Re = 50, the optimal value for is approximately 1.1. The results demonstrate that heat transfer rate is an increasing function of the Reynolds number.
- انتشار مقاله: 07-02-1397
- نویسندگان: Maryam Hoseinzadeh,Afshin Ahmadi Nadooshan,Morteza Bayareh
- مشاهده
- جایگاه : پژوهشی
- مجله: Energy Equipment and Systems
- نوع مقاله: Journal Article
- کلمات کلیدی: heat transfer,Car Engine,Radiator,Water-CuO Nanofluid
- چکیده:
- چکیده انگلیسی: In the present paper, the effect of water-CuO nanofluid on the radiator heat transfer of an automobile, Peugeot 405 XU7 engine type is investigated experimentally. The experiments are carried out for the radiator water (water-ethylene glycol with a volume fraction of 80-20, respectively) as a base fluid and water-CuO nanofluid with the volume fraction of 0.5% and 1%. Sodium Dodecyl Sulfate (SDS) is used to increase the stability of nanofluid. The results demonstrated that a significant increase in the heat transfer of the engine to the environment is obtained by adding CuO nanoparticles to the base fluid. For nanofluid volume fraction of 0.5 and 1% for a mass flow rate of 30 liters per minute, the heat transfer rate enhances 3% and 6.9%, respectively, in comparison with the base fluid. Although convective heat transfer coefficient increased by increasing the nanofluid volume fraction, the experiments showed that this coefficient increases with the mass flow rate up to 20 liters per minute and then decreases with the mass flow rate. Besides, the radiator pressure drop increases by increasing of the pressure of nanofluid. The results revealed that the ratio of heat transfer and pump power (merit parameter) decreases as the nanofluid pressure increases
- انتشار مقاله: 25-07-1397
- نویسندگان: Hasan Kiani,Afshin Ahmadi Nadooshan
- مشاهده
- جایگاه : پژوهشی
- مجله: Energy Equipment and Systems
- نوع مقاله: Journal Article
- کلمات کلیدی: Nanofluid,Experimental Correlation,Al2O3,Liquid Paraffin,Rheological Behavior
- چکیده:
- چکیده انگلیسی: Liquid paraffin can be used as a coolant fluid in electronic and cutting devices due to its suitable capabilities such as electrical insulating, high heat capacity, chemical, and thermal stability, and high boiling point. In this study, the dynamic viscosity of paraffin containing the alumina nanoparticles has been examined experimentally. The nanofluids with different composition of alumina (0, 1, 2, and 3%) with the diameter of 20 nm were prepared by two-step method and tested by professional Brookfield rheometer in the temperature range of 20 oC to 60 oC and the shear rates of 12 s-1 up to 200 s-1. Experimental results indicated that the nano-lubricant behaves as Newtonian fluid in the volume fraction of 0 and 1% only at the temperatures of 50 and 60 oC. While it behaves as non-Newtonian fluid in the volume fraction of 2 and 3% for all measured temperatures. The results showed that the power law model represents the best curve fitting of the experimental data. Therefore, the coefficient values of power-law model including, consistency index and flow index were reported. Finally, an equation of relative viscosity based on the volume fraction and temperature of the combination was proposed by applying the curve fit technique on the experimental data.
- انتشار مقاله: 24-07-1397
- نویسندگان: Rouhollah Yadollahi Farsani,Afrsiab Raisi,Afshin Ahmadi Nadooshan,Amin Shahsavar
- مشاهده
- جایگاه : پژوهشی
- مجله: Energy Equipment and Systems
- نوع مقاله: Journal Article
- کلمات کلیدی: Thermal Performance,Building Roof,City of Tehran,DesignBuilder,Block Joint
- چکیده:
- چکیده انگلیسی: The design of a building can provide the highest thermal comfort in the interior without any mechanical equipment and save energy to a large extent. The roof of a building is an important part for thermal loss. This research studies the thermal performance of 14 conventional roof structures in Tehran city by using designbuilder 4.5. It is found that the polystyrene block performs best compared to other structures. Despite the time and cost required to implement the beam for building roofs, the use of the polystyrene block is recommended. The results indicate that the use of 5 cm of thermal insulation in the structure of the roof results in 5.85% decrease in heat loss during winter and 5.65% decrease during summer. A reverse roof has a more favorable performance on hot days of the year. Also, the performance of roofing with heat insulation is better than that of the reverse roof in cold days.
- انتشار مقاله: 09-11-1396
- نویسندگان: Marzieh Heidari,Afshin Ahmadi Nadooshan,Morteza Bayareh
- مشاهده
- جایگاه : پژوهشی
- مجله: Energy Equipment and Systems
- نوع مقاله: Journal Article
- کلمات کلیدی: Numerical simulation,Wind Tower,Wind Tunnel,Natural Ventilation
- چکیده:
- چکیده انگلیسی: In the past, wind towers were applied as the main architectural part of building construction in the desert areas of Iran. These almost high structures were used as cooling load suppliers at residential buildings. In the present study, the effect of symmetric four-sided wind tower in flow induction to the bottom space has been analysed by using a wind tunnel and numerical simulations. In the numerical simulation, the flow is assumed to be three-dimensional, unsteady, compressible and turbulent. The experimental studies have been performed by placing a model of these structures at a laboratory wind tunnel. At this state, crossing airflow through every channel is measured for analysing the induction performance of wind tower at different angles of wind blowing. Moreover, the turbulence effect is analysed by adding horizontal and vertical blades and crowns at the top and bottom of the internal gate of traps for attaining better performance. Two different geometries are used for simulations. The results showed that inserting the blade and crown at the bottom and topaffect on the flow rate have effect on the flow rate. For instance, inserting horizontal blades and crown at the top of the model leads to 8 and 16% increase in the flow rate, respectively. The results of the numerical simulations have shown acceptable agreement with experimental results.
- انتشار مقاله: 16-08-1396
- نویسندگان: Davoud Jafari,Alireza Shateri,Afshin Ahmadi Nadooshan
- مشاهده
- جایگاه : پژوهشی
- مجله: Energy Equipment and Systems
- نوع مقاله: Journal Article
- کلمات کلیدی: Exergy,Solar Energy,Cogeneration Cycle,Ejector,Cascade Condenser
- چکیده:
- چکیده انگلیسی: The energy crisis in recent years has led to the use of thermodynamic cycles that work based on renewable energies. Low-temperature cycles—such as organic cycles—are suitable strategies for the application of renewable energies. The present study proposes a novel cycle through the integration of a two-stage compression refrigeration cycle with a combined Rankine power and ejector refrigeration cycle by using the cascade condenser method. The fundamental idea of this cycle is to obtain refrigeration production at lower temperatures, and to achieve higher thermal and exergy efficiencies. The results showed that the new cycle recorded an 11.67 percent improvement in thermal efficiency and a 16.89 percent improvement in exergy efficiency compared to the basic cycle. Even though the network output of the cycle is reduced, a significant increase in the refrigeration capacity of the cycle is observed.
- انتشار مقاله: 25-11-1395
- نویسندگان: Hamed Mortazavi Beni,Afshin Ahmadi Nadooshan,Morteza Bayareh
- مشاهده
- جایگاه : پژوهشی
- مجله: Energy Equipment and Systems
- نوع مقاله: Journal Article
- کلمات کلیدی: Laminar flow,Perforated Fin,Nusselt number,Reynolds Number
- چکیده:
- چکیده انگلیسی: The present paper reports the laminar fluid flow and heat transfer of a heated array of circular-perforated and solid fins mounted over a flat surface using the finite-volume method. One to four circular cross-sectional perforations are made along the length of the fins. The SIMPLE algorithm is used for pressure-velocity coupling and the second order upwind technique is employed to discretize the governing equations. The simulations are done for a range of Reynolds number, 100 < Re < 350, corresponds to the flow velocity of 0.37-1.28 m/s. The average Nusselt number, the average friction factor coefficient, and the perforated-fin effectiveness are calculated. The results demonstrated that for any Reynolds number, the heat transfer decreases and the friction factor increases with the number of perforations. It was observed that the fin with circular perforation had a higher effectiveness in comparison with the rectangular-perforated fins.
- انتشار مقاله: 30-09-1395
- نویسندگان: Shekoufeh Mohammadi,Afshin Ahmadi Nadooshan,Morteza Bayareh
- مشاهده