جستجوی مقالات مرتبط با کلیدواژه « T » در نشریات گروه « مکانیک »

Aside from energy production, biogas technology also contributes to mitigating environmental impacts. One of the key advantages of biogas is that it does not compete with human food sources. However, the main limiting factors include the digestibility of hemicellulose and cellulose in biomass, along with challenges related to lignin, cellulose crystallinity, and particle size. Lignin, abundant in softwoods, poses a complex structure, and its isolation remains a challenging issue that researchers are endeavoring to address. In the realm of enhancing productivity and achieving cost savings in biogas production, various measures have been implemented, with pretreatment emerging as a viable approach. Pretreatment involving physical, chemical, or biological methods can be applied to the digestion process. At this juncture, the emphasis should be on utilizing efficient and cost-effective methods and materials. Shredding biomass reduces its crystallinity by increasing the biodegradable surface area. Acidic pretreatment, avoided due to its cost and negative environmental impact, contrasts with the environmentally friendly and low energy consumption associated with biological pretreatments. Among the alkaline pretreatments, NaOH plays a significant role. Strong alkaline pretreatment is recommended for small digesters, while medium acid pretreatment is more suitable for larger digesters. The utilization of zero-valent iron nanoparticles is deemed as the most promising approach for enhancing biogas production. Furthermore, carbon-based nanoparticles have demonstrated a significant capability to enhance biogas production through electron transmission., In order to make biogas production affordable and reduce greenhouse gas emissions, carbon dioxide and hydrogen produced from biogas were used in industrial applications.

In this research, phase change materials (PCMs) have been examined as innovative tools for temperature control in thermal systems. These materials, operating intelligently without the need for mechanical equipment, undergo phase transitions naturally, adapting to environmental fluctuations and thereby enhancing energy efficiency in thermal systems. The study delves into the investigation and classification of the characteristics of these materials, along with their applications in various building components such as walls, windows, bricks, artificial stones, ceilings, and floors. The obtained results from the use of these materials indicate their potential as a novel solution for optimizing energy consumption in buildings. For instance, incorporating PCMs in walls leads to a reduction in thermal energy consumption, and utilizing nano-insulation in windows decreases the need for heating and cooling systems, providing users with greater independence from these facilities. Furthermore, the effect of PCMs in stones contributes to thermal stability, and in bricks, it significantly diminishes greenhouse gas emissions. Overall, the integration of PCMs in building floors enhances thermal storage capacity. These findings underscore the practical utility of PCM as an effective solution for improving the energy efficiency of buildings.

Converting electricity from wind to electric power by Small Wind Turbines (SWTs) a lot helps to produce electricity. They can be utilized to generate different networks, including independent, connected and integrated networks. Due to the size and installation location, SWTs are suitable for use in low Reynolds numbers (Re). With the aim of developing a marine Vertical Axis Wind Turbine (VAWT) with a porous blade in this research, simulations on different airfoils of NACA 4-digit, series 5-digit, and Selig profiles at different Re values of 60,000, 100,000, and 140,000, using the Double Multiple Stream Tube (DMST) with loss correction. In addition to blade specifications, turbine design parameters such as Aspect Ratio (AR) and solidity (σ) were also investigated by changing blade height and pitch. This paper presents an analysis for the design of a three-bladed VAWT to increase its aerodynamic performance in terms of power performance (Cp). The DMST approach, considering tip loss correction, is an effective lower-order accuracy performance prediction method for analyzing a wide range of turbine designs in a comparative manner with significantly lower computational cost. The study illustrated that the Selig S1046 airfoil to be suitable for wind tunnel tests at target chord Re in the specified Re range. The AR in different Re is more appropriate in the AR of 1.0 in lower and higher Re in a good range of TSR. Besides, the σ of 0.17 is suitable for increasing the turbine performance in the tested range.

Nowadays, Refrigeration systems play a very important and essential role in humans life, so that today's world cannot be imagined without refrigeration equipment. The range of these appliances is increasing daily, ranging from oil and gas equipment to air conditioning systems and health and nutrition. In the food industry, in addition to advances in the field of home refrigerators and cold storages for types of foods, we are seeing a growing expansion of stores and supermarkets that use refrigeration systems to keep food cool. With the increasing number of refrigeration equipment and the fact that they are one of the main consumers of electrical energy, in recent years extensive studies have been conducted to optimize this equipment both in terms of energy consumption and pollution of the environment is caused by the release of refrigerant material used in these devices. This article provides a comprehensive look at the history of refrigeration from a long time ago up to now. In this article, a comprehensive study of the history of refrigeration from the distant past to the present is taken. Also, considering the Futurology in this field and the need to use clean and renewable energies, the result was that it was necessary to supply some of the energy consumed by these systems with renewable energy.

The method of drying pistachios in compliance with international standards is developing significantly. Iran can be considered one of the top five producers of pistachios in the world. To preserve the nutritional value of pistachios for a long time and also to prevent them from spoiling, pistachios should be dried first and then stored. Different methods of pistachio drying often affect its taste and quality. Therefore, in this article, a new method for drying pistachios based on catalytic heaters is proposed. In this research, the numerical modeling of a pistachio dryer using catalytic heaters as the latest combustion technology with high efficiency has been discussed The main goal of this research is to evaluate a mathematical model in order to investigate the effect of various functional parameters of the catalytic heater on the amount of shrinkage of dried pistachios, which indicates the drying quality of the product. The result of this research seeks to answer the question whether it is possible to obtain high-quality dried pistachios by using a catalytic heater compared to other drying methods. The results obtained from the numerical modeling show the very favorable quality of dried pistachios with the catalytic heater method.

In the present research, the thermodynamic and exergoeconomic analysis of using the waste heat of a diesel engine to produce power has been investigated. In the dual cycle used, the high temperature cycle uses the energy of the exhaust gases and the low temperature cycle uses R245fa and R134a as the working fluid, respectively, in order to recover the waste heat of the intake air and engine cooling fluid. Energy analysis shows that the net power values of low temperature cycle, high temperature cycle and net power of the cycle are equal to 11.45 kW, 6.98 kW and 16.65 kW, respectively. Also, the energy and exergy efficiency of the cycle are obtained as 17.36% and 28.29%, respectively. The results of the economic analysis show that the evaporator and turbine of the high-temperature cycle have the highest overall cost compared to other cycle components and it is necessary to pay more attention than other system components. In addition, the overall exergy-economic factor of the cycle is equal to 32.52%. Therefore, 67.48% of the total costs of the cycle are due to exergy destruction, and the high temperature cycle evaporator has a significant contribution to these costs.

Buildings presently use 30% of global energy, set to rise due to climate change. This study assesses climate change's impact on energy consumption(heating/cooling loads) in Tabriz over six decades. It also compares the effect of several energy efficient solutions in buildings. Future weather data for 2050 and 2080 was generated by CCWorldWeatherGen based on existing files. Identifying the prevalent housing type in Eram, energy simulations for the current and next 60 years used Design Builder 7.0.0.096. Applying energy reduction strategies, the study evaluates thermal performance, energy consumption, and environmental impact.In all models, heating peaks in 2020, and cooling surges by 28.69% and 63.34% in 2050 and 2080 versus 2020. Model WI shows the lowest cooling energy variation at 66.66%. COM models rank as the most efficient in 2020, 2050, and 2080, cutting energy consumption by 8.24%, 11.95%, and 12.83%.Climate change raises annual energy consumption by 4% in the current building model. Comparing strategies, two models—COM and thermal insulation WI—enhance building performance in 2020, 2050, and 2080. These findings stress the urgency of implementing strategies to mitigate climate-induced escalation in building energy consumption.

The increasing demand for energy in countries and the use of fossil fuels has increased the global concern for the emission of greenhouse gases in the atmosphere. As one of the solutions to reduce greenhouse gas emissions in the world, the use of Carbon Capture Technology, especially CCUS, has attracted the attention of experts in various fields. However, the use of CCUS facilities did not go well for several reasons. Multiple technical options, use in diverse industries and complex evaluation systems of CCUS are important reasons. The use of this technology is another point of various concerns of the involved stakeholders, which leads to problems in decision making. Therefore, in this research, using the Analytic Hierarchy Process for Iran, six criteria have been defined, compared and evaluated from the point of view of total price, technological attractiveness, technological capability, cultural, passive and environmental defense. The evaluation results and related interpretations are examined from different perspectives. By adopting this evaluation method and creating a comprehensive model, decision makers can determine their needs and carry out multi-dimensional evaluation and get ideas for judgment or relevant decisions for the implementation of CCUS pilot projects.

Nowadays, urban waste is accumulated in nature in large quantities and causes pollution of the environment, air and underground water resources. Various methods have been considered for waste disposal, which can be mentioned as burying and burning as the main methods of waste management, both of which cause a lot of pollution to the environment. Recently, the pyrolysis process is proposed as a new method to convert municipal waste into liquid and gaseous fuel in research. But different wastes take different paths during this process, which leads to the production of fuels with different compositions. For this purpose, in order to produce fuel with certain characteristics, the reaction mechanism that depends on the type of feed should be determined. In this research, the path of pyrolysis reaction of low density polyethylene, cardboard, tire and poplar wood was chosen as the waste that represents a major part of urban waste. Their pyrolysis was done separately and together. The results showed that the type of feed determines the amount and composition of the resulting liquid fuel. Also, in the pyrolysis of mixed waste, a different reaction path was observed compared to the reaction path of individual feed pyrolysis, which indicated the existence of secondary reactions between the components of individual feed pyrolysis products.

The complexity of the design and the abundance of aspects that must be considered simultaneously by designers make it necessary to pay attention to different variables, which leads to the optimization of different functions. Other results of studies in this area are the identification of different variables. This study aims to investigate the effects of the dimensional variables and the ratio of area to volume of the classroom on the visual and thermal comfort of the users. For this purpose, the performance of the model in terms of the variables of and thermal comfort was investigated based on the weather data of Tabriz city using the simulator plugins Honeybee and Ladybug and the optimization plugin Octopus based on the evolutionary algorithm. The results of the survey show that the area-to-volume ratio of desired classrooms ranges from 1.16 to 1.69. The outcomes deemed optimal for the objectives of glare probability and daylight autonomy suggest that the most favorable solutions lie within the lower range of the surface area-to-volume ratio. Conversely, concerning comparative thermal comfort, the optimal solutions are found within the upper portion of the aforementioned range.

The investment capacity in wind power generation is growing significantly. However, the increasing penetration of wind energy in the network may lead to instability of the system and this may have negative impacts on the power quality of the system. In recent years, the effects of wind turbines on the voltage stability of power systems have received much attention. In the past, wind turbines based on squirrel cage induction generator (SCIG) were usually used due to their low cost and simplicity. But in recent years, wind turbines based on doubly-fed induction generator (DFIG) are mostly used because they are more stable. Recent studies have shown that the performance of the grid-connected wind turbines can be improved by employing flexible ac transmission systems (FACTS) devices. In this paper, the performance of a 9 MW wind turbine based on SCIG and DFIG in the presence and absence of static synchronous series compensator (SSSC), at the point of common connection (PCC) is investigated, considering single-phase and two-phase short circuit faults. A voltage stability index (VSI) is used to evaluate the stability of the wind turbines. The simulation results show that in the case of a two-phase fault that the system variables experience some oscillations, SSSC helps to damp out the generated oscillations faster and improve system stability. In particular, in the presence of SSSC, oscillations for the wind turbine voltage, reactive power and active power are damped out about 0.3, 0.5 and 0.6 seconds faster, respectively. All simulations are performed in MATLAB/Simulink software.

Heat exchangers play a very important role in various equipment. The new approach in this field is the use of microchannel heat exchangers, which, by increasing the heat transfer rate per unit of surface area or weight, have become the main candidates for use in different equipment compared to traditional heat exchangers. In refrigeration cycles, these heat exchangers are usually used in air condensers. In this research, an analytical code has been developed for the simulation and design of the microchannel condensers. In this simulation, instead of using the formulas for determining the single-channel heat transfer coefficient such as Dobson and Chato relations, formulas related to multi-channel tubes have been used, which are extracted from reliable and new sources and have high accuracy. This code is written in engineering equation solving software due to having a powerful database for different refrigerants. For the validation of the developed code, four condensers of different dimensions and with different refrigerants were selected to compare the data of the developed code with valid experimental data available for these four condensers as well as the data of past analytical codes. The results show that the accuracy of the developed code is much higher than the previous works and it estimates the heat capacity of the condenser and the temperature of the air and refrigerant side with an error of less than 10%. The developed code provides significant cost savings in the design and optimization process of heat exchangers.

One of the most important problems of office buildings in hot and humid cities like Ahvaz is the lack of effective ventilation of closed corridor spaces. Due to the low traffic and the reduction of energy costs, the use of air conditioning systems in these corridors is not of much concern to their owners. The main goal of this research is to improve the ventilation quality in the corridor spaces of Ahvaz office buildings, which is possible through modifying the architectural elements and position of blowers and suckers. The current research is a kind of interdisciplinary research method it is a hybrid and innovative method and involves the strategies of experimental research, simulation and case study. In this way, first an experimental study was conducted on the statistical population of the research (corridor spaces of Ahvaz office buildings) and after selecting case study, observations and periodical experimental tests were occured, interventions in architecture and research variables were carried out with the simulation method. In this research, CFD method was used to perform simulations and analysis, and Gambit preprocessor and Fluent software were used (after proving validity and reliability). The results showed that the use of ceiling fans and the change in the dimensions and shape of the corridors, according to the results of this research and the prediction of the back-to-the-wind suction, effectively improved the indoor air flow pattern and by reducing the age of stagnant air and establishing a constant air flow, Provides effective ventilation.

The most basic human need is water. In recent years, we have been facing the problem of water shortage due to climate change, decreased rainfall and improper use of resources, especially in Iran, where a large part of the country consists of dry areas. At Mazandaran University, we have consistently witnessed surface runoff flooding. Therefore, it is appropriate to consider of a water management plan to address these needs through proper planning. rainwater harvesting has been an institutionalized practice in Iran since ancient times in Iran, and in light of the United Nation’s latest warning at the 2023 Water Conference regarding the worsening of the water shortage situation, the objective of this paper is to investigate a rainwater harvesting system for Mazandaran University, in order to reach to green technologies. the current paper focuses on the feasibility to rainwater harvesting, as well as quantitative and qualitative analysis. The findings in this study indicate that during the fall season, a tank volume of 1500 cubic meters is recommended, while during the winter season, a tank volume of 750 cubic meters is enough. For the spring season, a tank volume of 600 cubic meters is recommended, and for the summer season, a tank volume of 360 cubic meters is sufficient, By implementing a 1500 cubic meter tank in the Faculty of Arts and Architecture, it is possible to harness the potential of harvesting water during periods of water shortage.

In recent years, generation of electricity through photovoltaic power plants has developed rapidly. The availability of sunlight and the appropriate return on investment are two important factors in the impressive growth of photovoltaic (PV) power plants. Unfortunately, increase in PV cell temperature is one the main defects of them and it has a significant negative effect on the electrical efficiency of PV panels. In this paper, using paraffin as phase change material (PCM) on the performance of photovoltaic cells has been investigated experimentally. The material has melting point of about 58˚C. Also, the effect of airflow at two different velocities of 2 and 4 km/h in presence of paraffin have been tested, too. To have a better management on performing the tests, a solar simulator was used, so that the solar irradiation and wind stream were supplied by means of a projector and an industrial blower, respectively. Results showed 13-16˚C decrease in PV temperature for the three modified cases, in comparison with the conventional one. Moreover, the effect of mentioned temperature reduction on both electrical efficiency and output power were also studied. Finally, the environmental effects of commissioning a 10-kW PV power plant were checked by using RETScreen software. Accordingly, the annual reduction of carbon dioxide (CO2) emission is estimated for all considered cases.

Following the recent development trend in the struggle to clean the environment, solar energy is considered as a clean energy, one of the most desirable alternatives to non-renewable resources. This paper presents an integrated approach to face the challenge of PV power plant site selection using analytical hierarchy process (AHP) and geographic information systems (GIS). The contribution of this research is in the development of an applicable approach for decision makers, in guiding the selection of the location of PV parks to achieve optimal performance and minimize costs, time and environmental effects. The important advantage of this research is the flexibility of the criteria's weight in the direction of the decision maker's goals. In this way, after determining the weight of the effective criteria, removing restrictions from the area and overlapping the weighted layers, an index called the Land Suitability Index (LSI) is defined. Based on this index, heavier areas are more favorable for building PV plants. Finally, the land suitability was grouped into five categories using the equal distance classification method. For further comparison, we tested two paths under the title of greater non-ecological weight and equal weight. The results showed that, like the basic approach, 22% of the area is ready to receive PV panels. However, the degree of suitability of some points in each approach had slight differences, which shows the flexibility of the chosen method. The decision maker can choose the appropriate path based on his goals.

The main part of the solar heating system is the solar collectors, the most common of which are the flat plate collector and the evacuated tube collector. In domestic use, solar hot water systems based on flat plate collectors are used more because of their low cost and minimal maintenance. Also, the outlet temperature of the collector corresponds to most domestic hot water needs. Solar hot water systems' performance varies with environmental conditions changes (atmospheric temperature, solar radiation, wind speed). This article modeled an indoor solar hot water system using TRANSYS software. This modeling is the development of a solar hot water system model based on an active flat plate collector. The developed model can predict the performance of the solar hot water system for different climatic and seasonal changes in the year. The system's long-term performance for Iranian weather conditions is evaluated and presented in the paper. Performance parameters such as the functional energy efficiency of the collector and hourly and monthly thermal efficiency are presented and discussed. Among the simulation results, it can be mentioned that the solar hot water system with a collector area of 5 square meters can meet more than 70% of the 400 liter needs of a household in Ahvaz, Iran.

Consuming chocolate is very common due to the feeling of pleasure and happiness. However, awareness of its adverse effects on health has led consumers to use low-calorie or no-calorie chocolates with fat and sucrose substitutes. The production of these types of chocolates faces significant challenges in the physicochemical and sensory fields. On the other hand, excessive consumption of chocolate due to its caffeine content can cause complications such as fetal growth disorders, spontaneous abortion, migraines, and behavioral disorders. In contrast, traditional and less harmful candies are considered a suitable alternative to chocolate, especially for children and the elderly. Due to the importance of milk production and consumption of dairy products in Iran, including cheese, large amounts of whey are produced and disposed of as waste in dairy industries. Efforts are being made to make optimal use of these wastes by turning them into food products. In this article, one of the dairy products of the Sangsar nomads of Semnan province, named "Chikoo candy", is introduced, which is produced without using vegetable oils and harmful additives and contains a suitable amount of milk fat.

Food packaging is responsible for protection, transportation, distribution, beauty, presentation, marketing and many other things. One of the packaging parameters that has received little attention is the paradox of packaging. The purpose of this article is to identify and classify different types of packaging paradoxes in the biscuit and chocolate industries. This research aims to provide a new classification in the field of food packaging paradoxes. In this research, qualitative methods, including library study and meta-composition, have been used. The target population was the articles available between 2010 and 2023. In this research, 210 elements of paradox or open code, 16 core codes and three categories were identified. The results are presented as a model. This paper presents a new synthesis of packaging paradoxes in the food industry. Also, this study provides a new approach to understanding the complexity of packaging decisions in the food supply chain. Understanding the complexity of decisions in the field of packaging will lead to better packaging management and increased packaging performance. The findings of this research can help companies better identify packaging paradoxes. Identifying the paradoxes of packaging makes managers make better decisions in the field of packaging. As a result, strategic packaging capacity can be achieved, leading to increased product sales and company performance.

Bioactive compounds and natural food pigments such as astaxanthin (red), lutein (yellow), chlorophyll (green), and phycocyanin (light blue), extracted from cyanobacteria, are rich in fatty acids, proteins, and antioxidant compounds. These bioactive components are used as dietary supplements in the form of paste, powder, tablets, or capsules. Fermented dairy products, beyond their nutritional and sensory properties, serve as a potential source of probiotics. However, in recent years, growing consumer concerns over the negative effects of animal-based dairy products and the instability of probiotics have significantly reduced dairy consumption. This review examines articles published between 2020 and 2023 in databases such as Springer, ScienceDirect, Scopus, and John Wiley to assess the potential of cyanobacteria in enhancing the physicochemical composition, colorimetric and antioxidant properties, texture, rheological behavior, sensory characteristics, and the viability of starter cultures and probiotics in yogurt, cheese, and ice cream by incorporating microalgal biomass and its derivatives. Relevant keywords were selected using the MeSH database, and based on these, thirty new review and research articles were compiled. The findings from the synthesis of various studies suggest that incorporating microalgae into cheese, fermented milk, and other dairy products represents an innovative approach for developing hybrid products enriched with plant-based compounds and animal proteins, providing a valuable source of bioactive ingredients.