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heat-transfer
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Numerical and experimental investigation of flat-plate pulsating heat pipes with extra branches in the evaporator section
, Article International Journal of Heat and Mass Transfer ; Volume 126 , 2018 , Pages 431-441 ; 00179310 (ISSN) ; Amarloo, A ; Shafii, B ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In addition to some approaches such as changing the working fluid or number of turns in a flat-plate pulsating heat pipe (FP-PHP), geometrical changes are also appealing for enhancing the thermal performance of this type of heat pipes. The main idea of this investigation is to increase heat transfer rate by increasing flow circulation of working fluid. By placing additional branches in the evaporator section, secondary bubble pumps were created which improved the circulation of fluid inside the FP-PHP. In order to investigate the impact of these additional branches, two similar four-turn aluminum FP-PHPs were fabricated. One of them was the conventional FP-PHP and the other had four...
Determination of thermal conductivity ratio of CuO/ethylene glycol nanofluid by connectionist approach
, Article Journal of the Taiwan Institute of Chemical Engineers ; Volume 91 , 2018 , Pages 383-395 ; 18761070 (ISSN) ; Ahmadi, M. H ; Fahim Alavi, M ; Nazemzadegan, M. R ; Ghasempour, R ; Shamshirband, S ; Sharif University of Technology
Abstract
Thermal conductivity of nanofluids plays key rol in heat transfer capacity of fluids. adding nanoparticles to a base fluid can lead to enhancement in thermal conductivty ratio. CuO/Ethyle Glycol (EG) is one of the most applicable nanofluids for heat transfer purposes. In the present study, thermal conductivty ratio of CuO/EG nanofluid is modeled by applying Group Method of Data Hnadling and Least Square Support Vector Machine – Gentic Algorithm approaches. Results indicated that the utilized model are very accurate in predicting thermal conductivty ratio of the nanofluid. The R-squared values for the proposed model are equal to 0.994 and 0.991 by applying Group Method of Data Handling and...
Availability analysis on combustion of n-heptane and isooctane blends in a reactivity controlled compression ignition engine
, Article Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering ; Volume 232, Issue 11 , 2018 , Pages 1501-1515 ; 09544070 (ISSN) ; Reyhanian, M ; Ghofrani, I ; Aziz, A. A ; Hosseini, V ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
Unfortunately, energy demands and destruction of the environment from uncontrolled manipulation of fossil fuels have increased. Climate change concerns have resulted in the rapid use of new, alternative combustion technologies. In this study, reactivity controlled compression ignition (RCCI) combustion, which can simply be exploited in internal combustion (IC) engines, is investigated. To introduce and identify extra insightful information, an exergy-based study was conducted to classify various irreversibility and loss sources. Multidimensional models were combined with the primary kinetics mechanism to investigate RCCI combustion, incorporating the second law of thermodynamics. The...
Non-isothermal simulation of the behavior of unsaturated soils using a novel EFG-based three dimensional model
, Article Computers and Geotechnics ; Volume 99 , 2018 , Pages 93-103 ; 0266352X (ISSN) ; Pak, A ; Samimi, S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this paper, a three-dimensional simulation of fully coupled multiphase fluid flow and heat transfer through deforming porous media is presented in the context of EFG mesh-less method. Spatial discretization of the system of governing equations is performed using EFG and a fully implicit finite difference scheme is employed for temporal discretization. Penalty method is used for imposition of essential boundary conditions. The developed numerical tool is employed to simulate two problems of nuclear waste disposal and CO2 sequestration in deep underground strata. The obtained results demonstrate the capability and robustness of the developed EFG code. © 2018 Elsevier Ltd
Numerical study of turbulent nanofluid heat transfer in a tubular heat exchanger with twin twisted-tape inserts
, Article Journal of Thermal Analysis and Calorimetry ; Volume 132, Issue 1 , April , 2018 , Pages 741-759 ; 13886150 (ISSN) ; Akbari, O. A ; Hassanzadeh Afrouzi, H ; Biglarian, M ; Koveiti, A ; Toghraie, D ; Sharif University of Technology
Springer Netherlands
2018
Abstract
In the present study, the turbulent flow of water/Al2O3 nanofluid in a tubular heat exchanger with two twisted-tape inserts has been numerically investigated in the three-dimensional coordinate. This numerical simulation has been done by using FVM, and all of the equations have been discretized by second-order upwind method. For coupling velocity–pressure equations, SIMPLEC algorithm has been used. The investigated parameters of the present study are Reynolds numbers at the range of 10,000–30,000, the effect of twist ratio of twisted-tape inserts from 2.5 to 4, co-swirl flow and counter-swirl flow of two twisted-tapes inside the tube and volume fractions of nanofluid from 1 to 4%. The...
Numerical investigation of the effects of fin shape, antifreeze and nanoparticles on the performance of compact finned-tube heat exchangers for automobile radiator
, Article Applied Thermal Engineering ; Volume 133 , 2018 , Pages 248-260 ; 13594311 (ISSN) ; Mostafazade Abolmaali, A ; Afshin, H ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this paper, heat transfer and pressure drop of air in the radiator of an internal combustion engine automobile were investigated. First, three types of fins including louvered, triangular vortex generator and rectangular vortex generator were modeled and their performance were compared with a plain fin. Effects of adding antifreeze in volume ratios of 40, 50 and 60% on the performance of louvered and rectangular vortex generator fins were investigated. Finally, the effects of adding copper oxide and aluminum oxide nanoparticles on the heat transfer improvement of louvered and rectangular vortex generator fins were simulated. The results demonstrated that louvered fin had the highest heat...
Optical and thermal analysis of a parabolic trough solar collector for production of thermal energy in different climates in Iran with comparison between the conventional nanofluids
, Article Journal of Cleaner Production ; Volume 175 , 2018 , Pages 294-313 ; 09596526 (ISSN) ; Mehrpooya, M ; Shafii, M. B ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Optical and thermal analysis of the most well-known solar concentrator system; parabolic trough collector (PTC) are investigated and analyzed. To evaluate performance of the PTC, four cities of Iran with different weather conditions are chosen as case studies. Effective parameters such as concentration ratio, incident angle correction factor, collector mass flow rate are considered. The main objective of this work is evaluation of the solar energy potential using PTC in under consideration cities with different climates. Numerical modeling of the analysis is done using MATLAB software. Simulation results shows that Shiraz, with an average annual thermal efficiency of 13.91% and annual useful...
A new approach to thermo-fluid behavior through porous layer of heat pipes
, Article Scientia Iranica ; Volume 25, Issue 3B , 2018 , Pages 1236-1242 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
This paper developed a new mathematical model to investigate the heat transfer as well as wick's thickness of a heat pipe. The model was established by conservative equations of continuity, momentum, and energy in the thermal boundary layer. Using a similarity variable, the governing equations were changed to a set of ordinary differential equations and were solved numerically by the forth-order Runge-Kutta method. The flow variables, such as velocity components, wick's thickness, and Nusselt number, were obtained. The results show that the Nusselt number is proportional to the square root of the Darcy-modified Rayleigh number and to the distance from the edge of the condenser surface....
Thermal radiation transfer calculations in combustion fields using the SLW model coupled with a modified reference approach
, Article Journal of Quantitative Spectroscopy and Radiative Transfer ; Volume 205 , 2018 , Pages 105-113 ; 00224073 (ISSN) ; Abrar, B ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The spectral-line weighted-sum-of-gray-gases (SLW) model is considered as a modern global model, which can be used in predicting the thermal radiation heat transfer within the combustion fields. The past SLW model users have mostly employed the reference approach to calculate the local values of gray gases’ absorption coefficient. This classical reference approach assumes that the absorption spectra of gases at different thermodynamic conditions are scalable with the absorption spectrum of gas at a reference thermodynamic state in the domain. However, this assumption cannot be reasonable in combustion fields, where the gas temperature is very different from the reference temperature....
Analysis of nonlinear acoustic wave propagation in HIFU treatment using westervelt equation
, Article Scientia Iranica ; Volume 25, Issue 4 , 2018 , Pages 2087-2097 ; 10263098 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
Currently, the HIFU (High-Intensity Focused Ultrasound) therapy method is known as one of the most advanced surgical techniques of tumor ablation therapy. Simulation of the non-linear acoustic wave and tissue interaction is essential in HIFU planning to improve the usefulness and efficiency of treatment. In this paper, linear, thermoviscous, and nonlinear equations are applied using two different media: liver and water. Transducer power of 8.3-134 Watts with the frequency of 1.1 MHz is considered as the range of study to analyze the interaction of wave and tissue. Results indicate that the maximum focal pressure of about 0.5-4.3 MPa can be achieved for transducer power rates of 8.3 to 134 W....
Using CFD simulations to improve the air-cooled steam condenser performance in severe windy conditions via proper tuning of blades pitch angles
, Article ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting, FEDSM 2018, 15 July 2018 through 20 July 2018 ; Volume 2 , 2018 ; 08888116 (ISSN); 9780791851562 (ISBN) ; Farhangmehr, V ; Khorshidi Behzadi, H. R ; Schneider, G. E ; Fluids Engineering Division ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2018
Abstract
The use of air-cooled steam condenser (ACSC) in thermal power plants has become so normal since a few decades ago. It is because there are so many valuable advantages with the ACSC implementation, e.g., little dependency on water consumption and benefiting from the forced convection heat transfer instead of the natural one to condense the steam. However, the thermal performance of an ACSC can be readily defected by the ambient wind; specifically, when the ambient temperature is high. This research work benefits from the computational fluid dynamics tool to study the details of ACSC's thermal performance in such undesirable ambient windy conditions. Furthermore, this work suggests an...
Geometrical optimization of a steam jet-ejector using the computational fluid dynamics
, Article ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting, FEDSM 2018, 15 July 2018 through 20 July 2018 ; Volume 2 , 2018 ; 08888116 (ISSN); 9780791851562 (ISBN) ; Sabzpoushan, S. A ; Schneider, G. E ; Fluids Engineering Division ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2018
Abstract
The vacuum systems play crucial role in various industries including, but not limited to, power generation, refrigeration, desalination, and aerospace engineering. There are different types of vacuum systems. Among them, the ejector or vacuum pump is highly utilized due to its low capital cost and easy maintenance. Generally, the better operation of a vacuum system can dramatically affect the performance of its upper-hand systems, e.g., the general efficiency of a thermal power plant cycle. This can be achieved if such vacuum systems are correctly designed, implemented, and operated. The focus of this work is on an existing steam jet-ejector, whose primary flow is a high pressure superheated...
Design of spherical vessels under steady-state thermal loading using thermo-elasto-plastic concept
, Article International Journal of Pressure Vessels and Piping ; Volume 86, Issue 2-3 , 2009 , Pages 143-152 ; 03080161 (ISSN) ; Kargarnovin, M. H ; Naghdabadi, R ; Sharif University of Technology
2009
Abstract
Governing equilibrium equations of thick-walled spherical vessels made of material following linear strain hardening and subjected to a steady-state radial temperature gradient using elasto-plastic analysis are derived. By considering a maximum plastic radius and using the concept of thermal autofrettage for the strengthening mechanism, the optimum wall thickness of the vessel for a given temperature gradient across the wall thickness is obtained. Finally, in the case of thermal loading on a vessel, the effect of convective heat transfer on the optimum thickness is studied and a general formula for the optimum wall thickness and design graphs for several different cases are presented. © 2008...
Advancement in numerical study of gas flow and heat transfer in microscale
, Article Journal of Thermophysics and Heat Transfer ; Volume 23, Issue 1 , 2009 , Pages 205-208 ; 08878722 (ISSN) ; Darbandi, M ; Sharif University of Technology
2009
Abstract
The gas flow and heat transfer in a long microscopic channel with inlet-to-outlet pressure ratio equal to 8000 is studied. The second-order slip velocity and temperature jump boundary conditions are used, which are derived using a gas-surface interface mechanisms. The inlet is discretized to 19 nodes and they are clustered near the wall, while the longitudinal dimension in discretized to 1500 divisions using a nonuniform grid distribution. The current velocity profiles are found to have a good agreement with high-order analytical solutions, indicating that the current velocity perform second-order accuracy. The pressure distributions are found to perform higher nonlinearity as the...
Numerical computation of compressible laminar flow with heat transfer in the entrance region of a pipe
, Article 2008 ASME Summer Heat Transfer Conference, HT 2008, Jacksonville, FL, 10 August 2008 through 14 August 2008 ; Volume 3 , 2009 , Pages 445-454 ; 9780791848487 (ISBN) ; Nouri Broujerdi, A ; Seume, J ; Sharif University of Technology
2009
Abstract
The authors' research work on pressure drop along gas transmission pipelines raised questions regarding the development length of the corresponding compressible flow and the effect of heat transfer in the entrance region on the pressure drop along the whole length of the pipe. In this paper, laminar, viscous, compressible flow in the entrance region of a pipe is investigated numerically in two dimensions. The numerical procedure is a finite-volume based finite-element method applied on unstructured grids. This combination together with a new method applied for boundary conditions allows accurate computation of the variables in the entrance region. The method is applied to some incompressible...
Experimental investigation of air flow over domed roofs
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 33, Issue 3 , 2009 , Pages 207-216 ; 10286284 (ISSN) ; Bahador, M.N ; Sharif University of Technology
2009
Abstract
Domed roofs have been used in Iran and many other countries to cover large buildings such as mosques, shrines, churches, schools, etc. However their favorable thermal performance has allowed them to be employed in other buildings like bazaars, or market places in Iran. In this investigation, wind pressure coefficients were determined experimentally for a domed roof model in a boundary layer wind tunnel. The model was a 1/10 scale model of the dome of an old school in the city of Yazd, in the central desert region of Iran. The model included a number of windows at the collar of the dome, and a hole on its apex. A total of 48 pressure tabs were employed to measure the air pressure at various...
Heat transfer optimization of twin turbulent sweeping impinging jets
, Article International Journal of Thermal Sciences ; Volume 146 , 2019 ; 12900729 (ISSN) ; Mahmoudabadbozchelou, M. A ; Afshin, H ; Sharif University of Technology
Elsevier Masson SAS
2019
Abstract
In this study, a numerical investigation is carried out to reveal the potential of obtaining uniform cooling on a planar surface by impinging jets in a turbulent flow regime using the SST k−ω turbulence model. Twin turbulent sweeping impinging jets (TTSIJ), as an idealization of an array of jets, are considered for heat transfer with the planar target surface. Unlike other studies that focused on a few effective parameters or limited the impinging jets to certain conditions, in this study, a more general investigation is performed to clarify the effects of all influential parameters on heat transfer. To this end, the effects of 8 design variables namely Reynolds number, the jet-to-target...
Free convection analysis in a Γ-shaped heat exchanger using lattice Boltzmann method employing second law analysis and heatline visualization
, Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 29, Issue 9 , 2019 , Pages 3056-3074 ; 09615539 (ISSN) ; Mohammaei, M ; Hooshmand, P ; Bagheri, N ; Hasani Malekshah, E ; Sharif University of Technology
Emerald Group Publishing Ltd
2019
Abstract
Purpose: The nanofluid flow and heat transfer within a heat exchanger, with different thermal arrangements of internal active bodies, are investigated. Design/methodology/approach: For the numerical simulations, the lattice Boltzmann method is utilized. The KKL model is used to predict the dynamic viscosity of CuO-water nanofluid. Furthermore, the Brownian method is taken account using this model. The influence of shapes of nanoparticles on the heat transfer performance is considered. Findings: The results show that the platelet nanoparticles render higher average Nusselt number showing better heat transfer performance. In order to perform comprehensive analysis, the heatline visualization,...
A review of recent advances in solar cooking technology
, Article Renewable Energy ; Volume 140 , 2019 , Pages 419-435 ; 09601481 (ISSN) ; Ghalebani, M ; Kasaeian, A ; Zamani, H ; Lorenzini, G ; Mahian, O ; Wongwises, S ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
One of the primary factors affecting the amount of worldwide energy consumption and greenhouse gas emissions is cooking. Solar cooking is an appropriate solution because it is both inexpensive and expandable. To illustrate modern advancements and the current status of solar cooking technology, this paper presents a review of recent experimental and analytical socioeconomic studies on solar cookers. The experimental studies have been divided into three categories based on different solar cooker structures: (i) box types, (ii) concentrating types, and (iii) panel types. Next, different designs are investigated according to their direct or indirect heat transfer modes and optional equipment for...
The effect of pH and ionic strength on the transport of alumina nanofluids in water-saturated porous media: Experimental and modeling study
, Article Journal of Thermal Analysis and Calorimetry ; Volume 137, Issue 4 , 2019 , Pages 1169-1179 ; 13886150 (ISSN) ; Yoozbashizadeh, H ; Madaah Hosseini, H. R ; Sharif University of Technology
Springer Netherlands
2019
Abstract
Alumina nanofluids are one of the most useful nanofluids, especially for increasing the thermal conductivity. Due to importance of porous media in the improvement of heat transfer, this study investigates the transport and retention of gamma alumina/water nanofluid in the water-saturated porous media. For this purpose, alumina nanofluids were introduced to the porous media consisting of water-saturated glass beads possessing various pH values (4, 7 and 10) and different ionic strengths (0.001 M of KCl, CaCl2, AlCl3, K2SO4, CaSO4, Al2(SO4)3, K2CO3 and CaCO3). Then the break through curve of each experiment was drawn and modeled by combining classical filtration theory with...