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Water plays a significant role in the daily activities of the human population, and its overall consumption is increasing rapidly, due to the enhancement of living standards. Iran is located in the dry belt of the earth, and 70% of its area is arid and semi-arid. The desalination systems, which use fossil fuels in order to overcome the water crisis in Iran, are not ever sustainable due to available energy depletion and greenhouse gas emissions. This study investigated the design of an active solar water desalination system. Evaporation rate and diameter reduction of sprayed saline water droplets in a glass chamber were calculated by a verified mathematical model. The effect of key parameters, including nozzle type (long cone orifice, drilled steel orifice, sapphire orifice), nozzle size (outlet diameters of 0.9–1.1 mm), injection pressure (1–5 bar), temperature, relative humidity (20–60%) and pressure inside the glass chamber (4500–6500 Pa), on evaporation rates, were investigated by the mathematical model. The flow rates of produced vapor and inlet saline water were calculated as 0.003252 L/s and 0.0181 L/s, respectively, by considering favorable condition, such as injection pressure of 5 bar, nozzle size of 0.9 mm, relative humidity of 20% and pressure of 4500 Pa inside the glass chamber. Radiation intensity was calculated using Meteonorm 7 software for Tehran during a year, which was compared with meteorological data of Mehrabad airport station. [ABSTRACT FROM AUTHOR]

Increased reliability in grid-independent photovoltaic systems is an important factor in the prevalence and greater use of solar systems. The present study was conducted in Iran. It is one of the countries with high potential in the field of solar energy with average radiation of 5–5.5 kWh/m2 intensity. On the other hand, due to the wide desert areas, it is important to investigate the effect of dust deposition on photovoltaic panels. An experimental study on the performance of photovoltaic panels over a 90-day period from May 25 to August 22, 2018, in Tehran, and under real conditions, to investigate the effect of dust deposition and climate change on their output power was performed. Because of its large population, political and economic conditions, Tehran has the highest importance amongst other cities in Iran. The results showed that the dirty panels produced 10% less power than the clean panels. Utilization of the data achieved from the experiment, the output power of the clean and dirty panels considering the air temperature and solar radiation is modeled using the MLR method. In order to establish the relationship between the reductions of the output power of the panel, due to the deposition of walnut dust, the soiling ratio (SR) is used. This ratio is gained by dividing the output power of the dirty panel by the output power of the clean panel to obtain a coefficient to determine the reduction of the output power of the desired photovoltaic panel in terms of air temperature and solar radiation. The coefficient earned with the correlation coefficient of 0.9 (R2) and the error of the mean root squares 7.94 (RMSE) can well predict the loss of power output of the panel due to dust sediment on the surface of the panel. The uncertainty range of experimental results is between of 7.83% to 8.08%. [ABSTRACT FROM AUTHOR]

Summary: In the present experimental research, a five‐stage solar still was investigated using phase change material paraffin wax. Owing to Iran's climatic conditions and its location in a dry area and nonexistence of fresh water sources, producing this water from saline water sources is essential. In this research, thus, a multistage solar still was planned and examined as a commonly used freshwater source via (phase change material) paraffin wax. On the back of the collector absorber plate, paraffin wax (phase change material) was used as an additional energy source for the sun. The volume of water produced in different thicknesses of 2.5 cm, 5 cm, and without PCM was investigated. The study results specified that the application of phase change material paraffin wax in the thickness of 2.5 cm agent led to a 15% increase in freshwater production. The quantity of water generated in the flow rates of 0.7, 1.3, and 1.8 L/min was also studied. The highest quantity of water produced was obtained in the 1.3 L/min flow rate. Moreover, the quantity of water generated in the five stages of the desalination process was separately measured that the highest amount of production was associated with the first stage. [ABSTRACT FROM AUTHOR]

• A statistical investigation. • Using of molecular dynamic simulation. • Effect of surface roughness with cone geometry on the boiling flow behavior of Argon fluid inside microchannels. • Microchannel surfaces are roughened by cone shape of roughness elements. Present work studies effects of presence of surface roughness elements with cone geometry on the boiling flow behavior of Argon fluid inside microchannels which are affected by different boundary wall temperatures using molecular dynamic simulation method. Firstly, microchannel is simulated with smooth surfaces under boundary wall temperatures of 84 K, 96 K, 108 K, 114 K and 133 K to prepare boiling condition for Argon atoms. Microchannel surfaces are roughened by cone shape of roughness elements and mentioned temperatures are applied on the roughened microchannel walls to be comparable with smooth one. Also, an external driving force of 0.002 eV/Å is applied on the Argon atoms at the entrance of both rough and smooth microchannels for all cases of wall temperatures. Statistical approach is employed to compare results of both microchannels. It is reported that adding roughness elements on the smooth surfaces of microchannel can extend contact surfaces of energy transfer which empowers boiling process of fluid flow. Presence of cone geometry of roughness elements causes fluid flow velocity reduction as much as 0.5–1.5%. Also, it is observed that roughness elements results in enhancement of temperature profiles of fluid. Moreover, it is found that role of roughness element in low time steps is stronger than high time step. Therefore, evolution of boiling process can reduce consequences of roughness on the flow behavior. Finally, due to ignorable consequences of roughness element on the boiling flow behavior, it is concluded that preparing very smooth surfaces is not economical for practical application such as medical micro probes to destroy abnormal or diseased tissues. [ABSTRACT FROM AUTHOR]

Summary: The optimization of the total annual cost in heat exchanger networks has been one of the overarching goals when synthesizing these networks. Several methodologies and techniques have been developed to achieve optimal costs in mixed material heat exchanger networks. This paper demonstrates the application of two decomposition methodologies (total decomposition and partial decomposition) for typical cost rules. The objective function was defined as the optimization and minimization of the total annual cost in mixed materials heat exchanger network. Three optimization algorithms, hybrid genetic‐particle swarm optimization (GA‐PSO), shuffled frog leaping algorithm (SFLA) techniques, and ant colony optimization (ACO), were used to further optimize the total cost in mixed materials heat exchanger network. The results indicate that the total annual cost in partial decomposition method was smaller than that in full integration method and total decomposition method. The reduction of the total annual cost was about 27% for GA‐PSO algorithm, 24% for SFLA and 10% for ACO relative to the results reported in this work. In partial decomposition method, at least one mixed material of heat exchanger was used to reduce the hot and cold utility for decreasing the total annual cost. Partial decomposition method resulted in the highest reduction of the total annual cost compared with other methods. Percentage of difference of the total annual cost were 0.36%, 1.92%, and 5.05% for full integration, total decomposition, and partial decomposition methods, respectively, in comparison with the previous studies. Results have been compared with the results of other studies to demonstrate the accuracy of the applied algorithms. [ABSTRACT FROM AUTHOR]

Impact of dust concentration and weather conditions – wind speed and relative humidity – on power generation of photovoltaic (PV) panels investigated experimentally in Tehran, Iran, for the period of April 10–September 22, 2018. Two Photovoltaic panels together with data-logging equipment were applied in this experiment. One panel was cleaned every day, while the other was remained unclean after 45 days. A performance ratio called "cleanness index" (CI) which is a temperature-corrected performance ratio of a soiled PV panel to that of a clean one was also used to indicate the dust deposition effect on PV panel performance. The uncertainty range of experimental results was between 5.27% and 5.55%. The results show that cleanness index had positive correlation with wind speed and negative correlations with relative humidity and dust concentration. Thus, in comparison to the clean PV panel, the output-power of the soiled panel reduced, approximately 8–12% per month. Furthermore, in order to numerically predict daily change of cleanness index (ΔCIPre), a linear regression model was developed and the outcome revealed that dust concentration had the most impact, with 21.56%. [ABSTRACT FROM AUTHOR]

This paper presents molecular dynamics simulations to study on the effects of external driving force and boundary wall temperature on the density, velocity and temperature profiles of Argon fluid atoms, flowed in a platinum microchannel with square section. The Argon atoms are structured in three regions. Two thin liquid film of Argon sandwich central vapor zone. Applying wall temperatures in the range of 84K to 133K prepares boiling condition which causes liquid atoms move from lateral layers to central bins of microchannel. Afterward, density of central layers of microchannel increases which is highlighted by sampling data after equilibrium condition of system energy in 4 time steps. It is concluded that augmentation of external driving forces on the Argon atoms from 0.002 to 0.01 and 0.02 eV/Angstrom can increase flow temperature from 180K to 1920K and 7570K, respectively which is noticeable for practical application such as medical especially in Cryosurgery. Moreover, augmentation of external forces can increase velocity profiles of Argon fluid flow. Generally, density was independent from variation of external force and boundary wall temperature in the studied limits. Also, alteration of boundary wall temperature does not play very important role on the velocity and temperature of Argon fluid inside microchannel. • Using of a statistical method. • Investigation of boiling flow by large number of Argon atoms inside a cubic microchannel. • Implementation of Molecular dynamic simulation. • Augmentation of external driving forces on the Argon atoms can increase flow temperature. [ABSTRACT FROM AUTHOR]

Present paper employs Molecular Dynamic Simulation (MDS) Method to study the effects of suspending 2, 4 and 6 Copper nanoparticles into Argon base fluid, flowing inside microchannel with square cross section under boiling flow condition. Fluid flow is supported by an external driving force of 0.002 eV/Å at the inlet section of microchannel and boiling process is supported by boundary wall temperature of 108 K. Afterward, statistical approach is employed as new insight for data analysis of present MDS method. Finally, it is indicated that increasing number of suspended nanoparticles into Argon base fluid flow, expands density profiles of Argon base fluid as much as 20%, 35% and 55% in order of addition of 2, 4 and 6 Copper nanoparticles, while; they brings velocity enhancement as much as 17.8%, 32.6% and 52.8%. Also, temperature augmentation is reported as much as 30.7%, 50.45 and 69.5% respectively. It is analyzed that suspended nanoparticles empowers boiling condition and thermal driving force which is perpendicular direction with power of external driving force to move atoms. Therefore, it is concluded that due to disproportionation of statistical results, employing high fraction of suspended nanoparticles into base fluid is not always economical for practical application. • A statistical investigation • Using of molecular dynamic simulation • Effects of suspending different number of Copper nanoparticles on the flow behavior • Boiling condition inside a microchannel with square cross section [ABSTRACT FROM AUTHOR]

Water and energy are two inseparable issues that play an important role in human life. The oceans are massive resources of water, but the main problem is their high salinity. Solar desalination systems have been considered as a suitable solution to solve the problem of water deficit and to overcome the environmental problems caused by the conventional water desalination plants. One of the important points in raising the efficiency of solar water desalination systems is increasing the evaporation rate in a system with specified dimensions. The direction of the spraying of seawater in the chamber is one of the effective parameters in elevating the discharged rate of vapor in solar desalination systems. In this study, the effects of other parameters including injection pressure, nozzle outlet diameter, nozzle type, and relative humidity inside the chamber were investigated in both upward and downward injection directions by a mathematical model. The results of the model indicated variations in the rate of vapor generation in upward and downward directions. Also, the effects of other important parameters were studied including injection pressure (in the range of 1 to 5 bar), outlet diameter of the nozzle (in the range of 0.9 to 1.1 mm), type of nozzle (long cone orifice, drilled steel orifice, and sapphire orifice) and relative humidity (within the range of 20% to 60%). Overall, the results indicated increased vapor production at an injection pressure of 5 bar, nozzle outlet diameter of 0.9 mm, long cone orifice nozzle, a relative humidity of 20%, and upward direction. [ABSTRACT FROM AUTHOR]