I am professor of mechanical engineering, member of Academy of Sciences of I R of Iran. My research area are: solar energy, convection heat transfer and Engineering education.
Subcooling degree (SD) is one of the most important parameters that has considerable effects on b... more Subcooling degree (SD) is one of the most important parameters that has considerable effects on boiling heat transfer. In the present study to find out the effects of this parameter on boiling heat transfer coefficient and surface temperature, experiments are performed for saturated and subcooled water with different subcooling degree in the local atmospheric pressure (863 mbar) over a horizontal stainless steel cylinder with specific surface roughness. Degree of subcooling and heat flux are changed from 5.5°C to 45.5°C and from 0.31 kW/m2 to 125.62 kW/m2, respectively. The experiments are conducted in a pool with dimensions of 120×400×550 mm3 which is made of Plexiglas with 15 mm thickness. The cylinder has 80 mm length, 9 mm diameter and 0.794 μm average surface roughness. Results show that with increasing the degree of subcooling for a specific average surface roughness, boiling heat transfer coefficient and average temperature of the surface are decreased. Also, for lower heat f...
There are many applications for solar energy from which the solar thermal utilization has receive... more There are many applications for solar energy from which the solar thermal utilization has received great consideration in the past decades. Among various solar systems, electricity generation is studied and several commercial plants around the world have been installed. In Iran for the first time an investigation is made to find possible applications of solar energy to construct the first 250 kW solar power plant in Shiraz. The plant is designed to generate electricity continuously to be feed to the national grid. For such plant a hybride-Rankine system which contains two cycles of hot oil and steam is selected. The collectors used are parabolic trough 25 m length, 3.4 m wide with 0.88 m focal length. Previous studies of the oil cycle and steam cycle is carried out for certain design conditions. Based on the limitation of construction, it was found that a new simulation is needed to find out the effect of heat exchangers performances on the overall power plant electricity generation...
ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting: Volume 1, Symposia – Parts A, B, and C, 2010
ABSTRACT Turbulent air flow around a surface mounted hemisphere is investigated numerically. The ... more ABSTRACT Turbulent air flow around a surface mounted hemisphere is investigated numerically. The flow field has been simulated using Large Eddy Simulation (LES) technique. Using LES results, variations of flow velocity at various sections along the midplane are presented and compared with the wind tunnel measurements. Also the results of LES are compared with a RANS model (k-ε RNG). It is concluded that LES with the proper grid resolution is capable to capture the complex features of the flow especially in the separation bubble formed behind the hemisphere. The LES results are in a better agreement with experimental data compared with k-ε RNG model. Also various SGS models for LES technique are tested and the predictions of these models are compared.
Abstract Regarding the global increasing trend of photovoltaic (PV) installations, it is necessar... more Abstract Regarding the global increasing trend of photovoltaic (PV) installations, it is necessary to examine their performance under different climatic conditions. In this study, a three years of experimentation was carried out in order to evaluate soiling loss, yearly degradation and economic viability of PV systems in the south-central Iran. The results showed that dust effect in consecutive years can be significantly different. For instance, soiling loss in summer of 2017 and 2019 was 6.9% and 7.7%, respectively, whereas this value was 26.4% in summer 2018 due to a sand storm. The yearly average degradation of PV module was evaluated 1.17%, which was significantly lower than the degradation rate found by considering only first two years operation of PV module. In the economic analysis part of the research, a typical 1 MW solar plant was modeled in PVsyst software by using the measured data. The economic assessment showed that investment in PV industry without any special government support is economically profitable, as net present value (NPV) and discounted payback time (DPT) were found 1,367,499 US$ and 5.82 years, respectively. Also, levelized cost of electricity (LCOE) was 0.099 US$/kWh, which could be reduced to 0.054 US$/kWh by providing loan for investment costs.
Experimental study is performed to analyze heat transfer characteristics as well as thermal perfo... more Experimental study is performed to analyze heat transfer characteristics as well as thermal performance of a new type of perforated fin with cross openings. For measurements, an array of these fins over a flat surface is made from aluminum and two cross circular holes are drilled in each fin. The tests are conducted in a wind tunnel which produces uniform air motion upstream of the test case. Temperature measurements are carried out by means of calibrated thermocouples system and surface temperature measurement is determined by a thermograph imager. Results of thermal structure and heat transfer are plotted for Reynolds numbers 2×10 4 4.6×10 4 based on the fin length.
In this work, simulating multiphase flows by implementing smoothed particle hydrodynamics (SPH) a... more In this work, simulating multiphase flows by implementing smoothed particle hydrodynamics (SPH) as a mesh-free method is presented. The formulation is validated on test cases including droplet evolution, droplet coalescence and droplet splashing by taking surface tension force into account while a high density ratio exists between fluids. Results are presented for time variation of each object at variation intervals until equilibrium condition is approached.
Basic understanding of the process of coolant heat transfer inside an engine is an indispensable ... more Basic understanding of the process of coolant heat transfer inside an engine is an indispensable prerequisite to devise an infallible cooling strategy. Coolant flow and its heat transfer affect the cooling efficiency, thermal load of heated components, and thermal efficiency of a diesel engine. An efficient approach to studying cooling system for diesel engine is a 3D computational fluid dynamics (CFD) calculation for coolant jacket. Therefore, computer simulation can analyze and consequently optimize cooling system performance, including complex cooling jacket. In this paper a computational model for boiling heat transfer based on two-phase Mixture model flow is established. Furthermore, the phenomenon of nucleate boiling, its mathematical modeling, and its effect on heat transfer is discussed. Besides, the static, total pressure, velocity and stream lines of the flow field, heat flux, heat transfer coefficient and volume fraction of vapor distribution in the coolant jacket of a fo...
Heat generation in an exothermic reaction during the curing process and low thermal conductivity ... more Heat generation in an exothermic reaction during the curing process and low thermal conductivity of the epoxy resin produces high peak temperature and temperature gradients which result in internal and residual stresses, especially in large epoxy samples. In this paper, an optimization algorithm was developed and applied to predict the thermal cure cycle to minimize the temperature peak and thermal gradients within the material of an industrial epoxy model during the curing process. An inverse analysis was used to obtain the new coefficients of Kamal’s equations for the model. To validate and verify the developed model, temperature profiles for several points of the material in the model were obtained by numerical simulation and compared with the previously experimentally measured data. With validated curing simulation, the mentioned inverse analysis and optimization algorithm were utilized to find the thermal curing cycle with several isothermal holds and temperature ramps. The new...
Subcooling degree (SD) is one of the most important parameters that has considerable effects on b... more Subcooling degree (SD) is one of the most important parameters that has considerable effects on boiling heat transfer. In the present study to find out the effects of this parameter on boiling heat transfer coefficient and surface temperature, experiments are performed for saturated and subcooled water with different subcooling degree in the local atmospheric pressure (863 mbar) over a horizontal stainless steel cylinder with specific surface roughness. Degree of subcooling and heat flux are changed from 5.5°C to 45.5°C and from 0.31 kW/m2 to 125.62 kW/m2, respectively. The experiments are conducted in a pool with dimensions of 120×400×550 mm3 which is made of Plexiglas with 15 mm thickness. The cylinder has 80 mm length, 9 mm diameter and 0.794 μm average surface roughness. Results show that with increasing the degree of subcooling for a specific average surface roughness, boiling heat transfer coefficient and average temperature of the surface are decreased. Also, for lower heat f...
There are many applications for solar energy from which the solar thermal utilization has receive... more There are many applications for solar energy from which the solar thermal utilization has received great consideration in the past decades. Among various solar systems, electricity generation is studied and several commercial plants around the world have been installed. In Iran for the first time an investigation is made to find possible applications of solar energy to construct the first 250 kW solar power plant in Shiraz. The plant is designed to generate electricity continuously to be feed to the national grid. For such plant a hybride-Rankine system which contains two cycles of hot oil and steam is selected. The collectors used are parabolic trough 25 m length, 3.4 m wide with 0.88 m focal length. Previous studies of the oil cycle and steam cycle is carried out for certain design conditions. Based on the limitation of construction, it was found that a new simulation is needed to find out the effect of heat exchangers performances on the overall power plant electricity generation...
ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting: Volume 1, Symposia – Parts A, B, and C, 2010
ABSTRACT Turbulent air flow around a surface mounted hemisphere is investigated numerically. The ... more ABSTRACT Turbulent air flow around a surface mounted hemisphere is investigated numerically. The flow field has been simulated using Large Eddy Simulation (LES) technique. Using LES results, variations of flow velocity at various sections along the midplane are presented and compared with the wind tunnel measurements. Also the results of LES are compared with a RANS model (k-ε RNG). It is concluded that LES with the proper grid resolution is capable to capture the complex features of the flow especially in the separation bubble formed behind the hemisphere. The LES results are in a better agreement with experimental data compared with k-ε RNG model. Also various SGS models for LES technique are tested and the predictions of these models are compared.
Abstract Regarding the global increasing trend of photovoltaic (PV) installations, it is necessar... more Abstract Regarding the global increasing trend of photovoltaic (PV) installations, it is necessary to examine their performance under different climatic conditions. In this study, a three years of experimentation was carried out in order to evaluate soiling loss, yearly degradation and economic viability of PV systems in the south-central Iran. The results showed that dust effect in consecutive years can be significantly different. For instance, soiling loss in summer of 2017 and 2019 was 6.9% and 7.7%, respectively, whereas this value was 26.4% in summer 2018 due to a sand storm. The yearly average degradation of PV module was evaluated 1.17%, which was significantly lower than the degradation rate found by considering only first two years operation of PV module. In the economic analysis part of the research, a typical 1 MW solar plant was modeled in PVsyst software by using the measured data. The economic assessment showed that investment in PV industry without any special government support is economically profitable, as net present value (NPV) and discounted payback time (DPT) were found 1,367,499 US$ and 5.82 years, respectively. Also, levelized cost of electricity (LCOE) was 0.099 US$/kWh, which could be reduced to 0.054 US$/kWh by providing loan for investment costs.
Experimental study is performed to analyze heat transfer characteristics as well as thermal perfo... more Experimental study is performed to analyze heat transfer characteristics as well as thermal performance of a new type of perforated fin with cross openings. For measurements, an array of these fins over a flat surface is made from aluminum and two cross circular holes are drilled in each fin. The tests are conducted in a wind tunnel which produces uniform air motion upstream of the test case. Temperature measurements are carried out by means of calibrated thermocouples system and surface temperature measurement is determined by a thermograph imager. Results of thermal structure and heat transfer are plotted for Reynolds numbers 2×10 4 4.6×10 4 based on the fin length.
In this work, simulating multiphase flows by implementing smoothed particle hydrodynamics (SPH) a... more In this work, simulating multiphase flows by implementing smoothed particle hydrodynamics (SPH) as a mesh-free method is presented. The formulation is validated on test cases including droplet evolution, droplet coalescence and droplet splashing by taking surface tension force into account while a high density ratio exists between fluids. Results are presented for time variation of each object at variation intervals until equilibrium condition is approached.
Basic understanding of the process of coolant heat transfer inside an engine is an indispensable ... more Basic understanding of the process of coolant heat transfer inside an engine is an indispensable prerequisite to devise an infallible cooling strategy. Coolant flow and its heat transfer affect the cooling efficiency, thermal load of heated components, and thermal efficiency of a diesel engine. An efficient approach to studying cooling system for diesel engine is a 3D computational fluid dynamics (CFD) calculation for coolant jacket. Therefore, computer simulation can analyze and consequently optimize cooling system performance, including complex cooling jacket. In this paper a computational model for boiling heat transfer based on two-phase Mixture model flow is established. Furthermore, the phenomenon of nucleate boiling, its mathematical modeling, and its effect on heat transfer is discussed. Besides, the static, total pressure, velocity and stream lines of the flow field, heat flux, heat transfer coefficient and volume fraction of vapor distribution in the coolant jacket of a fo...
Heat generation in an exothermic reaction during the curing process and low thermal conductivity ... more Heat generation in an exothermic reaction during the curing process and low thermal conductivity of the epoxy resin produces high peak temperature and temperature gradients which result in internal and residual stresses, especially in large epoxy samples. In this paper, an optimization algorithm was developed and applied to predict the thermal cure cycle to minimize the temperature peak and thermal gradients within the material of an industrial epoxy model during the curing process. An inverse analysis was used to obtain the new coefficients of Kamal’s equations for the model. To validate and verify the developed model, temperature profiles for several points of the material in the model were obtained by numerical simulation and compared with the previously experimentally measured data. With validated curing simulation, the mentioned inverse analysis and optimization algorithm were utilized to find the thermal curing cycle with several isothermal holds and temperature ramps. The new...
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Papers by Mahmood Yaghoubi