Ascent rainfall mechanism is “one of the most important factors in leading to various rainfall behaviors in different regions, such as various atmospheric precipitation seen in different time scales” (Masoompour, Miri, Zolfaghari, & Yarahmadi, 2013, p.299). In fact, some of them can be called atmospheric phenomena due to their special nature. One of these atmospheric phenomena is thunderstorm. Not only this storm and its accompanying phenomena like lightening, tornado, hail, strong winds, and heavy precipitation (see Changnon, 1925, 2001), but also atmospheric hazard phenomena in aviation, such asturbulence, frost, and wind shear (Tajbakhsh et al., 2009) cause remarkable damage to human and natural environments. Therefore, recognizing the features of these phenomena has been attracting the attention of researchers.

A comprehensive Thermodynamic analysis is used to characterize the exergy destruction rate in any part of the solar air preheating system (SAPHS) and calculate its efficiency. The system consists of a solar evaporator, a heat exchanger to air preheating and an auxiliary pump. A computer simulation program using EES software is developed to model and analyses the SAPHS. The system provides preheated air during the year. The Thermodynamic analyses involves the determination of effects of air preheating (APH) heat exchanger pinch point temperature, solar radiation intensity and overall heat loss coefficient of the solar evaporator on the performance of the SAPHS. The result showed that the main source of the exergy destruction is the solar evaporator. In the solar evaporator, 115. 9 kW of the input exergy was annihilated. Other main source of exergy annihilation is the APHHE, at 7. 45 kW. The overall energetic and exergetic efficiencies of the SAPHS were 70. 11% and 9. 766%, respectively.

In this paper, the cooling system of the air humidifier, which is fully powered by solar energy, is designed and optimized. In this cooling system, the ammonia absorption refrigeration system has been used instead of conventional compression cooling systems. Its design was done in a way that the performance of the system has increased remarkably in the environments with high temperatures. The ammonia absorption refrigeration is completely fed from parabolic solar collectors. The device has been designed in such a way that the fan is positioned at the beginning of the cooling system. Thus, to increase the efficiency of the fan and the system, the optimization of some axial fan characteristics has been performed and verified using simulation and testing. Furthermore, for the improvement of the heat transfer to air, the appropriate location of the heat exchanger inside the air duct channel has been determined by finite element analysis in Ansys CFX software. In the next step, the Thermodynamic analysis of the ammonia absorption refrigeration and the amount of energy required for air cooling have been calculated using numerical analysis in EES software. The results indicate that utilizing three solar collectors can provide the energy needed for the cooling system. Therefore, the proposed system can be applied to reduce production costs in various sectors of food industry.

Thunderstorms are destructive climatic phenomena that recognition of their mechanism, genesis and development could be especially very helpful to reduce their losses. In this study, we have examined thunderstorms with rainfall exceeding 10 mm in a 14-year period (2000- 2013) in the Ahwaz region. We have also made early identification of the code for this event to extract 10 mm of rain and daily data of sea level pressure from NCEP/NCAR reanalysis data in 32 days. Finally, using Principal Component analysis (PCA) and cluster analysis, we have classified circulation patterns of sea level as an effective factor in rain thunderstorms. The study showed that the Ahwaz region thunderstorm is following general pattern. In the first pattern, in the SLP, Sudan low pressure systems with trough at 1012 millibar with the passage over the Red Sea and the Persian Gulf made hot and humid air by advection on the study area at 850 and 500 millibar level. Ahwaz region is located in front of the trough at 1500 geopotential heights and 5760 geopotential meter respectively. In the precipitation of this pattern, instabilities have continued to 500 millibar level. In the second pattern, the anticyclone tongue (flank) at 1016 millibar is spread from the East with the passage over Oman Sea and the Persian Gulf. This situation is led to moisture advection on study area at 850 millibar level in front of the trough with geopotential height of 1500 to 1510 meter. Both the precipitation pattern, main source of moisture is provided by the warm seas in the South and the major factor of uplifting is also provided by the western trough.

Using clean energy resources is considered as a major solution to global warming. Hydrogen is one of the most popular clean and renewable fuels, which has widely been addressed by researchers in different contexts from additive fuel of internal combustion engines to pure feed of fuel cells. Hydrogen production is also one of the most interesting  fields of study and extensive effort has been devoted to  finding high-performance, fast, and economical approaches in this  field. In this study, a novel high-temperature steam electrolyser system with an integrated solar Brayton cycle core is proposed and numerically simulated for hydrogen production. Energy and exergy analyses were carried out to gain better perception of the performance of the system and Rankine and Organic Rankine Cycle (ORC) were integrated with the main core to improve its effciency. The influences of different parameters such as turbine inlet temperature, inlet heat flux from the sun, and compression ratio as well as the used organic fluid were investigated based on the  first and second laws. Results showed the high performance of the proposed system with more than 98% energy effciency in hydrogen production besides its simplicity of use. The highest exergy destruction occurred when the power generation system absorbed sun heat flux (more than 54%) and the performance of the system could be enhanced by improving the heat absorbing technology.

Exergy analysis is a method that can discuss the quality and quantity of energy in a chemical process. In this article, the exergy loss in a ammonia production plant is calculated. This process uses natural gas as the feedstock and consists of three main parts: syn gas production, CO2 absorption, and ammonia synthesis. For simulation of the process, Design II and Aspen plus software’s were implemented. The exergy efficiency of various units of the process was analyzed. Two methods for increasing the overall exergy efficiency are suggested. The first one is the reduction of co and CO2 concentrations to the mechanize unit. The second suggestion for increasing the overall exergy efficiency is to install a reboiler on the feed tray of the stripping column of the CO2 absorption unit.Based on the obtained results, the first suggestion can increase the exergy efficiency of the process by 0.83%, which is equivalent to 1.8 MW exergy loss reduction. The second proposed method can decrease the exergy loss of the CO2 absorption unit by 7.2%, equivalent to 0.865 MW.

In recent years, water stress has become a global crisis due to climate and demographic changes and lifestyle changes. Freshwater production from the sea using various processes is known as the most important solution to deal with this crisis. Among these processes, the humidification-dehumidification process has been considered by the scientific community as a flexible and low-cost method. The present work has investigated the performance of vortex-humidification-dehumidification water desalination cycle. The existing system is a dehumidifier-dehumidifier type, in which a vortex tube has been added. According to the structure of the vortex tube, its hot air outlet has been used to increase the possibility of moisture absorption in the humidifier and its cold air outlet has been used to increase the amount of condensed water in the humidifier. According to the second law of Thermodynamics, the performance of the cycle has been studied. In the analysis of multi-flow cycles with heat and mass transfer, the commercial software EES has been used to solve the equations. The fresh water output for specific conditions (sea level, air temperature 35 degrees Celsius and relative humidity 30 percent) is equal to 7.85 kg/h and the research results show that the Gained-Output-Ratio is equal to 1.189. It is shown that the use of the vortex tube and the consequent increase in air temperature at the inlet of the humidifier and the use of the second dehumidifier in the cycle increase the production of fresh water.