Papers by Seyed Soheil Mousavi Ajarostaghi
Journal of Central South University
In the present work, a parabolic trough solar collector with inner helical axial fins as a swirl ... more In the present work, a parabolic trough solar collector with inner helical axial fins as a swirl generator is considered and analyzed. All the numerical outcomes are obtained by utilizing the finite volume method's commercial code, ANSYS Fluent 18.2. The discretization of turbulence kinetic energy, turbulence dissipation rate, and energy equations as well as the spatial momentum equation have been done by a second-order upwind scheme. Hybrid nanofluid is utilized as a working fluid. This work consists of two sectors. In the first one, the influence of hybrid nanofluid types and, in the next sector, the impact of the volume concentration of selected hybrid nanofluid on the turbulence thermal efficiency are appraised numerically. The two considered hybrid nanofluids here contain multi-wall carbon nanotubes–iron oxide/water and silver and graphene nanoparticles/water. Obtained results showed that utilizing hybrid nanofluids causes more heat exchange rate than pure water. Also, amon...
This study experimentally and numerically investigates the effects ofthe feed methanol concentrat... more This study experimentally and numerically investigates the effects ofthe feed methanol concentration and temperature on the Direct Methanol Fuel Cell performance. An in house fabricated DMFC with 10×10cm 2 active area was used in experimental sets.A two dimensional lattice Boltzmann model with 9 velocities was used in this study. The computational domain includes all seven parts of DMFC: anode channel, catalyst and diffusion layers, membrane and cathode channel, catalyst and diffusion layers. The model was used to predict the flow pattern and concentration fields of different species in both clear channels and porous layers. Good agreement observed between experimental and numerical results. The cell voltage decreases for higher values of feed methanol concentrations due to higher rates of methanol crossover. Cell voltage increases with cell temperature increase, since both anode and cathode kinetics improve as temperature increases.
In this paper, heat transfer enhancement in a double pipe heat exchanger with a twisted tape as a... more In this paper, heat transfer enhancement in a double pipe heat exchanger with a twisted tape as a swirl generator in both sides is investigated numerically. The three-dimensional numerical simulations have been done by finite volume method using a commercial CFD code. The spatial discretization of mass, momentum, turbulence dissipation rate, and turbulence kinetic energy equations has been achieved by a second-order upwind scheme. A SIMPLE algorithm has been used for velocity–pressure coupling. To calculate gradients, Green–Gauss cell-based method has been utilized. The swirl generator is considered in both channels of the heat exchanger (hot and cold streams). Three types of nanofluids containing Al2O3, CuO, and SiO2 are considered as heat transfer fluid in the inner channel (hot fluid flow). Results showed that the maximum thermal performance belongs to CuO/water nanofluid at Re = 5492 by 7% enhancement in thermal performance in comparison with net water. Also, the SiO2/water nano...
Energies
Variable speed wind turbines are commonly used as wind power generation systems because of their ... more Variable speed wind turbines are commonly used as wind power generation systems because of their lower maintenance cost and flexible speed control. The optimum output power for a wind turbine can be extracted using maximum power point tracking (MPPT) strategies. However, unpredictable parameters, such as wind speed and air density could affect the accuracy of the MPPT methods, especially during the wind speed small oscillations. In this paper, in a permanent magnet synchronous generator (PMSG), the MPPT is implemented by determining the uncertainty of the unpredictable parameters using the extended Kalman filter (EKF). Also, the generator speed is controlled by employing a fuzzy logic control (FLC) system. This study aims at minimizing the effects of unpredictable parameters on the MPPT of the PMSG system. The simulation results represent an improvement in MPPT accuracy and output power efficiency.
Energies
In this numerical study, 4 types of hybrid nanofluid, including Ag-MgO/water, TiO2-Cu/water, Al2O... more In this numerical study, 4 types of hybrid nanofluid, including Ag-MgO/water, TiO2-Cu/water, Al2O3-CuO/water, and Fe3O4-multi-wall carbon nanotube/water, have been considered potential working fluid in a single U-tube borehole heat exchanger. The selected hybrid nanofluid is then analyzed by changing the volume fraction and the Reynolds number. Based on the numerical results, Ag-MgO/water hybrid nanofluid is chosen as the most favorable heat carrier fluid, among others, considering its superior effectiveness, minor pressure drop, and appropriate thermal resistance compared to the pure water. Moreover, it was indicated that all cases of Ag-MgO/water hybrid nanofluid at various volume fractions (from 0.05 to 0.20) and Reynolds numbers (from 3200 to 6200) could achieve better effectiveness and lower thermal resistances, but higher pressure drops compared to the corresponding cases of pure water. Nevertheless, all the evaluated hybrid nanofluids present lower coefficient of performance ...
Journal of Thermal Engineering
In this paper, a numerical investigation is presented on heat transfer augmenting by using variou... more In this paper, a numerical investigation is presented on heat transfer augmenting by using various kinds of modified multiple twisted tape inserted in solar parabolic trough collectors. The pressurized water is considered as working fluid and Reynolds number varying from 10000 to 20000. The received heat flux on the solar absorber was assumed non-uniform due to hemispheric insolation of sun. The obtained numerical results for the Nusselt number, friction factor and thermal performance are presented for each cases. Various types of twisted tape including single twisted tape, normal, perforated, center-cleared, square, and V-cut dual twisted tape are considered and analyzed. The numerical simulations are performed by a commercial CFD code, ANSYS FLUENT 18.2. The obtained results revealed that at Re=10000 and 20000, the average Nusselt numbers of case with dual v-cut twisted tapes are more than plaine tube by 19.58 and 17.44%, respectively. Moreover, thermal performance of all cases with various twisted tapes is larger than 1 which means that utilizing twisted tape with various configurations leads to more thermal performance than plain tube. The thermal performances of case with dual square-cut twisted tapes (as the best case) for Re=10000 and 20000 are more than plain tube by about 16 and 12% improvement, respectively. Furthermore, for the case with perforated dual twisted tape (as the case with lowest thermal performance), the thermal performances for Re=10000 and 20000 are more than plain tube by about 9.2 and 7% improvement, respectively.
Sustainable Energy Technologies and Assessments
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science
Solar air heating is a solar thermal technology wherein the sun energy is absorbed by an intermed... more Solar air heating is a solar thermal technology wherein the sun energy is absorbed by an intermediate medium and utilized to heat air. In the present paper, a solar air heater equipped with innovative arc shaped ribs is considered. The heat transfer process in the proposed solar air heater is evaluated numerically for Reynolds numbers between 6000 and 12000. The influences of the rib cross section type, the inter-rib distance, the aspect ratio and the pitch of the ribs on the thermal efficiency of solar air heater are analyzed. Results indicate that firstly, ribs with quadrangular type of cross section exhibit the best coefficient of performance. Moreover, ribs with low pitch (40 mm) and aspect ratio equal to 0.5 show the highest thermal performance. Also, the effect of the distance between the ribs on the thermal efficiency of the considered solar air heater is insignificant. Finally, two correlations are obtained for the average Nusselt number and friction factor based on three di...
International Journal of Ambient Energy
Energies
To investigate the impacts of using nano-enhanced phase change materials on the thermal performan... more To investigate the impacts of using nano-enhanced phase change materials on the thermal performance of a borehole heat exchanger in the summer season, a three-dimensional numerical model of a borehole heat exchanger is created in the present work. Seven nanoparticles including Cu, CuO, Al2O3, TiO2, SiO2, multi-wall carbon nanotube, and graphene are added to the Paraffin. Considering the highest melting rate and lowest outlet temperature, the selected nano-enhanced phase change material is evaluated in terms of volume fraction (0.05, 0.10, 0.15, 0.20) and then the shape (sphere, brick, cylinder, platelet, blade) of its nanoparticles. Based on the results, the Paraffin containing Cu and SiO2 nanoparticles are found to be the best and worst ones in thermal performance improvement, respectively. Moreover, it is indicated that the increase in the volume fraction of Cu nanoparticles could enhance markedly the melting rate, being 0.20 the most favorable value which increased up to 55% the ...
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects
We numerically examine the thermal performance of a round tubular heat exchanger featuring a comb... more We numerically examine the thermal performance of a round tubular heat exchanger featuring a combination of three passive techniques for heat-transfer enhancement: (i) center-cleared twisted-tape i...
Solar Energy
Abstract This review presents impact of nanofluids in solar evacuated tube solar collectors (ETSC... more Abstract This review presents impact of nanofluids in solar evacuated tube solar collectors (ETSCs). Recent works on this type of solar collector are summarized. The first part depicts the significance of choosing ETSCs for solar domestic hot water in addition to classification of these collectors and application of each categories. In second part, usage of nanofluids is studied in considered system and through this pervasive review, some issues such as, various kinds of nanofluids, size of nanofluids, volume fraction, and nanofluid application in every kind of ETSCs on the heat transfer augmentation have been analyzed. This state-of-the-art review shows that most of nanofluids in ETSCs are water-based with nanoparticles of TiO2, CuO, and Al2O3. Other types of nanoparticles including CeO2, WO3, Ag, CeO2, GNP, and Cu were less considered up to now. Moreover, 40, 34, and 26% of nanofluids were used with size between 1–25 nm, 25–50 nm, and 50–100 nm, respectively. Furthermore, highest thermal improvement belongs to heat pipe type solar collector with SWCNT-based nanofluids by 93.43% at m = 0.025 kg/s. Besides, nanoparticles concentrations are challenges of using nanofluid in ETSCs. This parameter has marginally affected on performance of ETSCs. So, the optimum amount of this parameter for each type of nanofluids will suggest for future works.
Journal of Thermal Analysis and Calorimetry, 2021
Enhancement in properties of thermal storage materials improves their performance and contributes... more Enhancement in properties of thermal storage materials improves their performance and contributes to reducing the greenhouse gas emissions. The enhancement can be made in a passive way, which is cost-effective and hardly requires management. For decades, phase change materials (PCMs) have been used in many applications for thermal storage, thermal control and thermal insulation purposes. PCM can store a huge amount of energy with low or no temperature swing. However, the major drawback of PCM is the low thermal conductivity. Techniques of different scales (macroscopic, microscopic and nanoscopic) have been adopted in thermal engineering to enhance the thermal conductivity of PCM. This paper presents a comprehensive review of the literature dealing with micro/nano enhancement techniques of PCMs. Enhancement effects as well as limitations of each technique are discussed in detail. Moreover, direction for future research and possible challenges are pointed out along with conclusions dr...
Sustainability
Geothermal energy systems can help in achieving an environmentally friendly and more efficient en... more Geothermal energy systems can help in achieving an environmentally friendly and more efficient energy utilization, as well as enhanced power generation and building heating/cooling, thereby making energy systems more sustainable. The role of the backfill material, which fills the space between a pipe and the surrounding soil, is important in the operation of ground heat exchangers. Among the review articles on parameters affecting ground heat exchanger performance published over the past eight years, only two discuss types of backfill materials, even though the importance of these materials is significant. However, no review has yet been published exclusively on the kinds of backfill materials used in ground heat exchangers. This article addresses this need by providing a comprehensive review of a variety of types of backfill materials and their effects on ground heat exchanger performance. For organizational purposes, the backfill materials are divided into two categories: conventi...
Journal of Thermal Analysis and Calorimetry
SN Applied Sciences
Minimum concrete cover for rebar, rebar diameter, concrete compressive strength, embedded length ... more Minimum concrete cover for rebar, rebar diameter, concrete compressive strength, embedded length of rebar, and lateral reinforcement by stirrups are the crucial factors considered in existing predicting equations and regulations for predicting rebar-concrete interface (RCI) bond strength. However, considerable effects of concrete composition on RCI are ignored in design codes and investigations. This paper intends to comprehensively highlight the critical aspects of this research gap. Additionally, a practical experimental approach is described in the present study to efficiently consider the effect of the new generations of concrete on RCI bond strength. Finally, nano-concrete is considered as a case study to show the importance of nanoparticle types on RCI bond strength. Overall results show that studying the microstructure of the transition zone at RCI is essential to accompany with the RCI bond strength for considering new generations of concrete in reinforced concrete structures. Additionally, the current study emphasizes that more investigations are necessary to be conducted by future works to fill the existing research gaps in RCI.
Journal of Energy Storage
Applied Thermal Engineering
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Papers by Seyed Soheil Mousavi Ajarostaghi