Gholamhassan Najafi

• Professor
• Professor (Full) at Tarbiat Modares University

The purpose of this study is to enhance the efficacy of a hybrid cooling system by merging two horizontal buried pipe shallow geothermal ventilation systems (HBSGV) with a vertical buried pipe shallow geothermal ventilation system (VBSGV). This integration seeks to deliver efficient cooling for buildings by harnessing renewable energy sources. Thre...

The reactive oxygen and nitrogen species generated by plasma have demonstrated consequential effects on diverse commercial applications. Hence, studying the chemistry and spatial distribution of reactive species in plasma is imperative for understanding the influence of plasma in various applications. This study aims to systematically explore the p...

The efficient conversion and storage of thermal energy are crucial for sustainable energy systems, and phase change materials (PCMs) offer a promising solution for latent heat storage (LHS). However, because these materials present problems such as phase-change leakage and low electrical and thermal conductivities, they cannot be used efficiently f...

The study introduces a framework for optimizing eco-friendly dual-fuel engines, combining CFD and ANN, to reduce carbon emissions and improve sustainable transportation.We achieved optimal performance with a 52–65 % NG substitution ratio. SOI timing had a big effect on NOx emissions; later injection decreased NOx formation because it made the mixtu...

There have been a very limited number of studies conducted on utilization of thermal combination from combined solar-CHP systems for drying agricultural products. Most of researches in this field are focused on studying this combination for electricity and heat generation for houses, industrial process heat and so on. In this study, a solar drying...

Photovoltaic thermal technology (PVT) is gaining increasing attention due to its improved performance and reliability made possible by continuous technological advances. Despite these significant advances, the potential of PVT modules to simultaneously heat, cool and generate electricity passively remains unexplored. In this study, we developed a d...

The quest for enhanced efficiency in solar energy systems has directed significant attention towards optimizing solar dish concentrators. This study investigates the performance enhancement of solar dish concentrators through the use of advanced nanofluid solutions and innovative cavity designs. The experimental setup includes various nanofluid con...

The use of solar dish concentrators for harnessing solar energy is an established technology in the Realm of renewable energy solutions. This study presents a comprehensive Computational Fluid Dynamics (CFD) simulation to analyze the performance of a solar dish concentrator equipped with different cavity receivers. The aim is to optimize the therma...

In the current investigation, a novel methodology was employed to assess iron powder as a recyclable and sustainable energy carrier. Concurrently, an examination of the modeling of iron powder ignition and the ensuing heat output from the burner was undertaken. The flame temperature was determined by examining the light intensity emitted by the par...

The integration of photovoltaic/thermal (PV/T) systems with nanofluids presents a promising avenue for enhancing sustainable energy solution. This study investigates the performance of such systems through experimental analysis and computational fluid dynamics (CFD) simulations. Nanofluids, engineered colloidal suspensions of nanoparticles in base...

Iron powder, classified as a metal, serves as a versatile energy carrier and stands as a compelling alternative to traditional fossil fuels. Its appeal lies in its remarkable abundance and wide availability, attributes that position it favorably as a sustainable energy source. Notably, iron-based fuels are characterized by their environmentally ben...

Industrial Carbon black production is a petrochemical process that has high level of waste heat and emissions. Main points of CB process include furnace and stack lines. Also, the use of different feedstocks can be effective in level of waste heat and amount of emission pollutants. So the main objective of this research use from the pinch technolog...

In this research, the small segments parabolic dish concentrator (SSPDC) with a modified cavity was optically and thermally investigated. The SSPDC consisted of small mirrors that were tracking the sun individually. The SSPDC allows using different concentration ratios and aperture areas. Oil, pure water, and water + perypolen glycol (PG) were eval...

This paper provides an overview of passive cooling technologies used in photovoltaic (PV) and photovoltaic-thermal (PVT) modules that serve as an alternative energy source for countries with high solar irradiation and cooling requirements. Passive cooling is an attractive solution for PV panel applications because, unlike active cooling methods, it...

Industrial Carbon black production is a petrochemical process that has high level of waste heat and emissions. Main points of CB process include furnace and stack lines. Also, the use of different feedstocks can be effective in level of waste heat and amount of emission pollutants. So, the main objective of this research use from the pinch technolo...

Renewable energy is vital for the future of the energy supply because of its properties, which include sustainability, affordability, and environmental friendliness. The low dependability of these sources is a disadvantage due to their nondeterministic and unpredictable production patterns. Utilizing several energy production sources in conjunction...

Archimedes screw turbines have gained popularity in generating power from flowing water. One aspect that hasn't been considered yet is optimizing those parameters that are considered assumptions in the prediction models. In this research, a simple procedure was introduced to design an appropriate Archimedes screw turbine for a given site using a pr...

Extended Abstract Introduction: Renewable energy sources may be unstable and unreliable in geographical areas[1]. It is not possible to provide electric power through photovoltaic systems at night, and the wind energy system may not be active during the day. Therefore, the design and integration of different sources of renewable energy, especially...

Iran's energy sector, which includes power generation, transportation, industry, buildings, and homes, is a significant source of greenhouse gas emissions. Plans for efficient design and development of maximum power control systems aim to increase the share of renewable energy in electricity usage. Floating photovoltaic systems combine existing pho...

Knowledge on operational energy consumption and embodied energy, replacing embodied greenhouse gas (GHG) emissions in building materials, and national energy resources have become a necessity. In this study, the importance of investigating the stochastic nature of weather-dependent renewable energies is well documented. The management of the hybrid...

The high power coefficient of the Darrius vertical axis wind turbine lift regime has prompted researchers to concentrate their efforts on this regime, despite the fact that these turbines suffer from major problems in the drag-lift regime. In the present study, in addition to exploring the performance of the Darrius type wind turbine at blade tip s...

Solar parabolic dish concentrator is one of the high-temperature applications of more than 400 °C for thermal and electrical power generation. In the solar parabolic dish concentrator, the arrangement of reflectors over the surface area is the significant factor for effective concentration of solar radiation. Also, focal image is one of the most in...

In this study, a numerical model was developed for prediction of Nusselt number in solar cavity receivers. Thermal oil and water were used as the working fluid. A dish concentrator with different shapes of the cavity receiver, including hemispherical, cylindrical, and cubical, was investigated. The different shapes of cavity receiver were studied u...

Brand modern technology of leak detection by using pressure transient analysis has been developed and interested to research due to its advantages such as low cost, simplicity and convenient to use. This technology uses the concept of signal reflections which identify pipeline features. The method used in this study was using a pressure transducer...

Producing electricity from waste energies has been introduced as a useful approach in moving towards stability. Therefore, in the current study a new wind channel has been designed and fabricated to convert created airflow resulting from automobiles movement on the highways to electricity. This channel is fabricated to guide airflow from automobile...

Energy management, emission reductions, and sustainable development are directly linked. The use of renewable energy and intelligent control systems serves two goals: sustainable development and energy supply. In this paper, we propose an improved intelligent hybrid renewable energy management system to utilize local renewable energy. The penetrati...

Renewable energy policies emphasize both the utilization of renewable energy sources and the improvement of energy efficiency. Over the past decade, built-in photovoltaic (BIPV) technologies have mostly focused on using photovoltaic ideas and have been shown to aid buildings that partially meet their load as sustainable solar energy generating tech...

Energy democracy policymakers pay attention to planning to the formation of energy markets and exchanges of energy regions, diversification of energy resources, especially renewable resources, and global challenges due to greenhouse gas emissions. Over the introduction of concepts related to sustainable development, energy planning at the internati...

Petroleum fuel plays an important role in industry, transportation, agriculture and other related industries in Iran. Iran has about 9.5% of the world’s total oil reserves in 2020 and is ranked 4th in the world. The presence of sufficient conventional fossil fuels for internal combustion engines has caused environmental problems. If these Iranian f...

Energy democracy policymakers pay attention to planning to the formation of energy markets and exchanges of energy regions, diversification of energy resources, especially renewable resources, and global challenges due to greenhouse gas emissions. Over the introduction of concepts related to sustainable development, energy planning at the internati...

Renewable energy regulations place a premium on both the use of renewable energy sources and energy efficiency improvements. One of the growing milestones in building construction is the invention of green cottages. Building Integrated Photovoltaic (BIPV) technologies have been proved to aid buildings that partially meet their energy demand as sust...

The use of wind energy can be traced back thousands of years to many ancient times. Among the tools used for converting wind energy was the vertical-axis wind turbine (vawt). Investigating the performance of this type of turbine is an interesting topic for researchers. The appropriate correlation between the Double Multiple Stream Tube (DMST) model...

In this study, a batch flow oil extraction system was used for extraction of oil from walnut (Juglans regia L.) and Sesamum (Indicum sesame). Sample mass (g), applied pressure (MPa), and processing temperature of oil (°C) were selected as independent variables and oil extraction mass percentage and oil analysis as dependent variables. Response surf...

Photovoltaic cells are a significant renewable energy source due to their cheap cost and renewability. In both warm sunny and colder and cloudier conditions, a-Si modules outperform c-Si modules on a normalized energy basis. This study investigated 1 m 2 of amorphous photovoltaic silicon on curved surfaces. The Taguchi and response surface methods...

Nanolubricants are dispersed nano-scales solid particles in a base fluid. Due to high demand for higher efficiency in thermal application systems, nanolubricants is an ideal option to meet the particular demand. As the result a numerous scientist have been investigating to replace the base fluid in the vapor compression refrigeration (VCR) system w...

Response surface methodology has been widely implemented to improve the pollutant emission characteristics and performance of a compression ignition engine. The fusel oil-biodiesel blend and pure diesel under varied engine loads and speeds with the use of Models of RSM were found to be statistically significant. This research study has aimed to sta...

Isolated droplet combustion experiments have been carried out on neat diesel, a 15 vol% 2-methylfuran – 85 vol% diesel mixture (MF15), and nanofuels made from MF15 base fuel with addition of multiwalled carbon nanotubes (MWCNTs) at 25 ppm, 50 ppm, and 100 ppm concentrations (referred to as MF15C25, MF15C50, and MF15C100). Compared to MF15, the nano...

In recent years, leveraging the amount of energy loss occurring in different fields of human activity has captured the attention of researchers. Harvesting and drying processes can be integrated in order to reduce energy losses. The present research work seeks to pinpoint the association between the harvesting and drying processes as well as to mak...

In the address layer of energy systems, the infiltration of phase-change material (PCM) into composite metals can be used. In this study, infiltration technology was developed with simultaneous pressure and vacuum in graphite foam. The vacuum pump was used to create porosity during the melting and infiltration process in the composition of PCM pell...

Contrary to energy, exergy may be destroyed due to irreversibility. Exergy analysis can be used to reveal the location, and amount of energy losses of engines. Despite the importance of the exergy analysis, there is a lack of information in this area, especially when the engine is fueled with biodiesel–diesel fuel blends under various injection ope...

The aim of the present study is to evaluate the thermal behavior of cylindrical modules in a thermal energy storage unit as a combined sensible and latent heat. A thermal energy storage unit is designed, fabricated, and connected to a cold and hot water supply at constant temperatures to monitor the performance of the storage unit. The thermal ener...

In late 2019, the outbreak of a deadly Coronavirus shocked the world. Following the Covid-19 pandemic, governments were forced to enact a series of restrictive laws, including road and urban transportation. As a result of these restrictions, the consumption of fossil fuels in the world decreased and reduced the price and demand of these fuels. Beca...

On 23 January 2020, the world saw the first coronavirus lockdown come into force in Wuhan, China in an effort to stop the spread of the illness. This lockdown set the precedent for similar measures in other cities across the country, putting a halt to daily activities including industry and traffic. Factories and other industries were shut down and...

In this investigation, a hybrid energy conversion system is proposed and evaluated for energy, exergy, and environmental criteria for generating power and freshwater. The system comprises of a Humidifier Dehumidifier Desalination (HDD) system for producing freshwater, an organic Rankine cycle system for generating electric power, and a solar Parabo...

The organic Rankine cycle (ORC) is an effective technology for power generation from temperatures of up to 400 • C and for capacities of up to 10 MW el. The use of solar irradiation for driving an ORC is a promising renewable energy-based technology due to the high compatibility between the operating temperatures of solar thermal collector technolo...

The objective of the present research work is to investigate a novel high-efficiency nanofluid in a solar dish concentrator by using the numerical model developed. The working fluids examined consisted of soybean oil-based MXene nanofluid of different concentrations (i.e. 0.025, 0.075 and 0.125 wt%) and pure soybean oil. The studied nanofluids yiel...

Wet washing is the most common method for biodiesel purification, but higher water consumption, longer purification time, and high expenses bring limitations on the use of this process. One of the suitable methods to remove such limitations is to use new techniques for purification. In this study, biodiesel purification was evaluated in a novel con...

The demand for fossil fuels is increasing because of globalization and rising energy demands. As a result, many nations are exploring alternative energy sources, and hydrogen is an efficient and practical alternative fuel. In the transportation industry, the development of hydrogen-powered cars aims to maximize fuel efficiency and significantly red...

In this work, the melting process of phase change material (PCM) in double tube heat exchangers was investigated and evaluated through the use of different combinations (1, 2, 3% Nano-Enhanced PCM and 1, 3, 5% Nano-HTF) of GQD, as well as SWCNT nanoparticles and PCM (RT82). In this study, the effect of three different methods, namely the dispersion...

In this study, the performance of a photovoltaic-thermal-thermoelectric (PVT-TE) hybrid module under laboratory conditions is evaluated. The hybrid system consists of three main components of a PV module, a TE module, and a cooling unit. To reduce the surface temperature of the PV module and to increase the performance of the whole system, four dis...

Organic Rankine Cycle (ORC) is a promising electricity production technology that exploits low and medium heat sources. Usually, renewable and alternative heat sources can be used in order to feed an ORC with heat. The exploitation of geothermal energy is a usual and sustainable way to feed an ORC because it is a sustainable, abundant, economical a...

The current study has been done with the goal of biodiesel synthesis of sour cherry kernel oil (SCKO). SCKO is a potential novel and free source for biodiesel production. SCKs have an oil content of ∼25%, so the SCKs can be considered as a suitable source for producing fuel from wastes. SCKO has a low acid value (0.9 mg KOH/g). Therefore, the trans...

The sonication technique is one of the effective methods to stabilize nanolubricants. This paper aims to elaborate on the sonication duration's impact on the stability of Al2O3-Polyol ester nanolubricants. A two-step method has been performed to prepare nanolubricants. Each sample consisted of a nanoparticle mixed with POE using a magnetic stirrer...

Bitter orange (Citrus aurantium) is a fruit that is grown in different regions of Iran. Moreover, bitter orange has also a lot of seeds that mostly considered as a waste part of the fruit. Bitter orange’s seeds have a lot of oil content (~ 38%), so the bitter orange seeds can be a suitable source for generating energy from wastes. In the current st...

Flat-plate solar collectors are one of the cleanest and most efficient heating systems available. Studies on the presence of covalently functionalized graphene (Gr) suspended in distilled water as operating fluids inside an indoor flat-plate solar collector (FPSC) were experimentally and theoretically performed. These examinations were conducted un...

Compression combustion engines are a source of air pollutants such as HC and Co, but are still widely used throughout the world. The use of renewable fuels such as ethanol, which is a low-carbon fuel, can reduce the emission of these harmful gases from the engine. A fundamental analysis is proposed in this research to experimentally examine the emi...

H-type Darrieus vertical axis wind turbines (VAWT) have omnidirectional movement capability and can get more power compared to other VAWTs at high tip speed ratios (𝜆). However, its disadvantages are self-starting inability and low generated power at 𝜆 less than 1. The performance of H-type Darrieus wind turbine at 𝜆<1 was studied using double mult...

Supplying electrical power for pumps in irrigation systems is a costly and challenging procedure, especially in remote or rural areas. The objective of the current investigation is the suggestion and analysis of a solar-driven Organic Rankine Cycle (ORC) that provides the required power of a pressurized irrigation system. Parabolic trough collector...

Archimedes Screw Turbines (ASTs) can become a popular device to generate electricity from hydraulic power at very low-head or nearly zero-head places. In this article, the performance of ASTs is numerically investigated using Computational Fluid Dynamics (CFD) to assess different screw rotation speeds, volume flow rates, and inclination angles. The...

In the present study, a micro combined heat and power (micro-CHP) system using compressed natural gas (CNG) and biogas fuels, was developed. The objective of this research study was to investigate the utilization of nanofluids as a working fluid to improve thermal performance of the micro-CHP system. Three different nanofluids based on the the CNT,...

This study presents the assessments of the acoustic performance of a Herschel-Quincke (HQ) tube, which includes sensitivity analysis and multi-objective optimization of its design variables. A proper model introduced using the flow characteristics of the HQ tube. Input variables were frequency (f), temperature (T), the ratio of areas (R), and tube...

COVID-19 has heightened human suffering, undermined the economy, turned the lives of billions of people around the globe upside down, and significantly affected the health, economic, environmental and social domains. This study aims to provide a comprehensive analysis of the impact of the COVID-19 outbreak on the ecological domain, the energy secto...

Among different sources of renewable energy, solar energy is widely used almost exclusively because of its ease of availability and its lowest environmental effects. The most commonly used solar collectors are the flat plate solar collectors (FPSCs). However, they are less powerful (low capacity to convert solar energy to thermal energy). It is pos...

In recent years, biodiesel has been demonstrated to offer a suitable level of reliability and attracted the attention of many researchers. Accordingly, various studies have been carried out to account for the biodiesel production and application, producing valuable reports and findings. In this research study, the effects of biodiesel on engine noi...

Renewable power plants contribute almost insignificantly in the country's electricity supply. Due to the environmental uncertainty and the rapid development of modern technology in the recent century, it is usually necessary to predict future situations using insufficient data over a short period. Renewable fuels and biofuels as a significant repla...

The greenhouse industry is an energy-intensive sector with a heavy reliance on fossil fuels, contributing to substantial greenhouse gas (GHG) emissions. Addressing this issue, the employment of energy-saving strategies along with the replacement of conventional energy sources with renewable energies are among the most feasible solutions. Over the l...

A flat plate solar collector (FPSC) was analytically studied, with functionalized graphene nanoplatelets (f-GNPs) as its working fluid. Four samples (wt % nanofluids) were prepared in different base fluids such as ethylene glycol (EG), distilled water (DW):EG (70:30), and DW:EG (50:50). Experimental results (via DW) were used to verify the effectiv...

The goal of the present paper is the investigation of a solar desalination system with an organic Rankine cycle system for power and freshwater production. This system is an environmentally friendly technology that is able to utilize solar energy properly in a novel cogeneration application. A parabolic trough concentrator with a smooth and corruga...

Reliability is the possibility that a product can perform its expected performance properly within a specified period of time without failure and under certain operating conditions. Reliability is one of the most important factors for evaluation of diesel engines, but there is no standard method for predicting reliability during engine development...

In agricultural greenhouses, employment of energy-saving strategies along with alternative energy sources has been identified as a potential solution to address the intensive energy consumption of these cultivation facilities. This study investigates the integration of renewable energy technologies, including solar thermal, solar photo-voltaic (PV)...

Due to the damaging environmental impacts resulting from direct entry of mineral lubricants into the environment, the use of bio-lubricants as a sustainable and renewable alternative to mineral lubricants is necessary; therefore, bio-based lubricants play an important role in overcoming existing challenges and reducing energy consumption. The prese...

Energy crises and environment impact forced governments and countries to develop utilizing renewable energy in different forms. One of the first forms of alternative energy which was in use is bioethanol which is using in SI (spark ignition) engines as pure fuel or after blending with gasoline. The selection of proper blending of bioethanol plays a...

In this study, heat transfer characteristic and fouling of Novel EGR cooler (Semi-spiral) system were investigated. In this study, waste vegetable oil (Waste Cooking Oil) was used as feedstock for biodiesel production. The experiment was conducted in different loads (25%, 50% and 75%) and different speeds (2100rpm and 2400rpm). Four fuel blends wer...

The objective of this study was to measure and evaluate the performance of a New Pneumatic Harvester (NPH) for harvesting the olives fruit and compare the results with those of similar cases. The study involves two sections, namely, the NPH and the collector system. Two oily types of olive (‘Mari’ and ‘Yellow’) were selected to evaluate the NPH and...

Graphene has attracted much attention from various researchers because of its enhanced mechanical, thermal, and physio-chemical properties. Graphene exhibits high thermal conductivity and stability, less erosion and corrosion than other available nanoparticles. Various existing literature signifies a large portion of the research focuses on stabili...

Lubricants are among the largest drivers of global oil demand in the world. The negative environmental impacts resulting from the entry of direct mineral lubricants necessitates the application of bio-lubricants as an excellent alternative to mineral lubricants. The main resources of bio-lubricants are edible/non-edible oils. The use of edible oils...

Today renewable energies such as biodiesel have considerable role in the bio-based economy. Long production time and low efficiency are a number of problems in biodiesel production that is essential to be considered when designing and operating the biodiesel production systems. In this study, using safflower oil in a hydrodynamic cavity reactor, bi...

Today, due to the reduction of energy resources in the world and its pollutants, energy storage methods and increase the thermal efficiency of various systems are very important. In this research, the thermal efficiency and energy storage of two heat exchangers have been investigated in series using phase change materials (RT82) and single wall car...

ARTICLE INFO In this article, an intelligent system is introduced to the detection and classification of some common mechanical faults of an engine alternator based on the frequency analysis of vibration signals. For this purpose, firstly the vibration signal of an alternator under four conditions, including healthy, bearing corrosion, cracked roto...

In recent decades, rising greenhouse gas emissions have become a major challenge and concern. Environmental pollution is one of the greatest human challenges of the 21st century. Improving the performance of internal combustion engines and reducing the amount of pollutant emissions has always been a concern for researchers. The use of alternative f...

ARTICLE INFO Under the crisis of global warming and drastic climate changing, carbon-neutral renewable energy is considerably proposed as a feasible clean alternative energy to fractionally replace fossilized fuel. To cop up with ever stringent emission regulations, researchers have investigated different types of renewable fuels like biodiesel and...

The purpose of this research is to investigate the combined effects of biodiesel-ethanol fuel blends on the performance and emission parameters of a diesel engine by the response surface methodology (RSM). The genetic algorithm was also applied for optimizations of the parameters. According to the results, the brake power and torque were decreased...

In this research, for the first time a mixture of diesel-biodiesel-water-bionanoparticles was prepared to simultaneously optimize the fuel consumption, reduce pollutant emission, and enhance the performance of diesel engines. To this end, graphene quantum dots as biodegradable nanoparticles were synthesized through the hydrothermal method. In this...

In this research, the thermal attributes of shell and finned tube heat exchanger such as thermal efficiency, pressure drop, heat transfer rate and average temperature in the tube side of heat exchanger with using the different volume concentration of nanoparticles (SWCNT and Graphene quantum dot) at the various Reynolds number by applying either fi...

Wind power is one of the most popular sources of renewable energies with an ideal extractable value that is limited to 0.593 known as the Betz-Joukowsky limit. As the generated power of wind machines is proportional to cubic wind speed, therefore it is logical that a small increment in wind speed will result in significant growth in generated power...

Waste heat recovery is an effective way to reuse waste energy in order to produce useful energy products. This technique aids in the reduction of CO2 emissions and to create sustainable and efficient systems. The objective of the present review paper is to summarize and to discuss the studies about waste heat recovery with the organic Rankine cycle...

In the current study, a solar-driven organic Rankine cycle (ORC) system was thermodynamically, economically and environmentally investigated. A focal point concentrator with two different cavity-shape receivers was investigated as the ORC heat source. More specifically, the cylindrical and the hemispherical cavity receivers were examined and compar...

In this experimental study, the effects on engine performance and fuel-induced emission characteristics were studied using various fuel blends such as F10B10 (10% fusel + 10% biodiesel + 80% diesel vol%), F20B10 (20% fusel + 10% biodiesel + 70% diesel vol%), F20B20 (20% fusel + 20% biodiesel + 60% diesel vol%), F30B10 (30% fusel + 10% biodiesel + 6...