جستجوی مقالات مرتبط با کلیدواژه « مصرف انرژی » در نشریات گروه « مکانیک »

Transportation is known as an important energy consumer, and achieving sustainable transportation implies controlling and improving the amount of energy consumption. So, a system for evaluating the urban transportation system based on the principles of sustainability can help to improve the economic, social and environmental indicators. This study was conducted with the aim of clarifying the place of energy consumption in the transportation evaluation model based on sustainable development indicators. This research is applied-developmental in terms of purpose, and in terms of the method and time period of data collection, it is considered a survey-cross-sectional research. Library studies and questionnaires were considered as data collection tools. In the qualitative section by searching, in the period from 2000 to 2023, 41 articles were selected and analyzed. Meta-composite analysis was used to identify the research categories and present the initial model, and 9 components and 53 indicators were identified. Validation and screening of indicators was done with Delphi technique. The participants of this section are 28 experts who were selected using the snowball pattern. Finally, 9 components and 49 indicators were confirmed. In the end, using the process of network analysis, the priority and weight of dimensions, components and indicators were determined. The findings showed that the environmental dimension has 45% and the economic dimension has 36% of the weight of the model. The social dimension is ranked third with 19%. The energy consumption component has the most weight with 17% and its indicators have 3 positions out of the top 10.

A comfortable indoor environment is essential for the health, performance, and academic efficiency of students in schools. The amount of energy consumption to provide comfortable conditions in educational buildings in Iran has placed these buildings among the biggest consumers of the energy sector with energy consumption of more than 160-kilowatt hours per square meter, and it is necessary to reduce energy consumption in this sector through environmentally friendly solutions. This research aims to reduce energy consumption and provide comfortable conditions in educational buildings by making changes in the layering of building shell elements including walls and light-transmitting walls as a static combination solution. The research method is quantitative and modeled through the use of design-builder software, and to examine the existing situation and optimize the energy of the building with variables Insulation type, wall thermal insulation thickness, insulation layering, glass type, and thickness, gases between walls, wall thickness were discussed. The results showed that in the studied building, the use of polyurethane insulation in the innermost layer (behind the carpentry plaster) of the south and north classrooms with a thickness of 10 cm had the most optimal performance. In the north classroom, a 2-pane light-transmitting wall with low-emissivity glass with a glass thickness of 3 mm and 13 mm argon gas with 28.40% reduction in energy consumption, and also in the south classroom with windows with a 3-pane light-passing wall and 3 mm normal glass and 13 mm of air had the best performance of 23.04% reduction in energy consumption...

Reducing energy consumption is of great importance today, considering that residential buildings have a significant contribution to energy consumption, so strategies to reduce energy consumption in this sector can have a great impact on reducing energy consumption in countries. In this paper, the energy analysis of a building has been done using the effects of using air gaps in the walls on the amount of energy consumption reduction. In order to check the results, the building design stages were first simulated using AutoCAD maps in DesignBuilder software, and EnergyPlus engine was used for energy calculations. To investigate the effect of using air gap in walls on reducing energy consumption, three different thicknesses of air gap (1cm, 2.5cm and 5cm) were analyzed. The results of energy simulation for these three different walls with the base wall show that the use of air gaps has reduced the total energy consumption and heating and cooling loads in different months of the year in the building, so that the monthly cooling load of the building in the hottest month of the year is 10.3, 12.8 and 14%, and in the coldest month of the year, Also, the annual heating load consumption of the building decreases by 25.7, 30.9, and 33.6 percent, respectively, and the annual cooling load decreases by 8.3, 10, and 10.9 percent, respectively, which is a significant percentage considering the high annual cooling energy consumption of the building.

The major part of energy consumption in buildings is related to air conditioning systems. Since selection of a suitable air conditioning  system in any climatic zone has a major impact on reducing energy consumption as well as preparing thermal comfort conditions, in this study, the performance of the fan coil system with radiant chilled ceiling system with pipes embedded in concrete is compared and evaluated. In the radiant cooling system, the cooling tower is used as the sole source of cold water supply required, and since the effective operation of the cooling tower depends on environmental conditions, the performance of the cooling system in different climatic conditions has been studied. For thermal comfort assessment and performance analysis of two mentioned systems, Energy Plus software has been used. The performance of these systems has been compared in the cities of Ahvaz, Tehran and Tabriz. The cities of Ahvaz, Tehran and Tabriz represent hot and semi-humid, hot and dry, temperate and dry climates, respectively. The results show that the radiant chilled ceiling system integrated to cooling tower is capable to provide thermal comfort conditions in Tehran and Tabriz climatic conditions. Furthermore, the energy consumption of cited cooling system is significantly lower than a Fan coil system. The simulation results confirmed that the radiant cooling consumed 50-65% less energy in comparison to a benchmark fan coil system in Tabriz and Tehran, respectively.

In this research, the role of Phase Change Materials (PCM) in energy saving in lightweight prefabricated buildings is studied. For this purpose, a typical building in Kermanshah, Iran is simulated in DesignBuilder software. A split unit is used as air conditioning system. The annual energy consumption of the building in the reference state is 2577.27 kWh. The implementation of the InfiniteRPCM21C was investigated in all directions including each individual wall, ceiling, four walls simultaneously and the entire building envelope. The southern wall is the best option among the walls with 12.14% energy saving. From an economic point of view, this wall has the best performance as well by saving 2.08 kWh/kgPCM. Implementation on the entire envelope increases savings up to 37.2%. Although this is not an economical case, but it reduces the need for energy to almost zero in four months of the year. By examining the PCM in different layers of the wall, it was found that in all directions, the inner surface of the wall leads to the greatest energy savings. Also, taking account the PCM thickness in the range of 5 to 25 mm showed that the smaller the thickness, the greater the savings per unit mass of the PCM. Therefore, thicknesses more than 20 mm are not recommended. Finally, the effect of the PCM melting point in the range of 18 to 29 degrees Celsius was investigated and it was found that the maximum energy saving is obtained at the melting point of 21 degrees Celsius.

Photovoltaic-integrated Shading systems, are multifunctional components to generate electricity and simultaneously provide the shade needed for building surfaces and walls. Applying integrated photovoltaic systems with building components, including fixed shadings, in addition to regulating the penetration of sunlight and saving energy, seems to be a fully functional approach due to the production of part of the buildings' energy. Therefore, to evaluate the performance of Photovoltaic-integrated Shading systems, in optimizing energy consumption, the need to study the effect of Photovoltaic-integrated Shading systems, on energy in Shiraz was considered. Therefore, 15 Photovoltaic-integrated Shading systems scenarios for the facade of an office space model were calculated using the DesignBuilder simulation program and PVsyst. According to the results, the Photovoltaic-integrated Shading systems, designed with 4 louvers with a slope angle of 45 degrees and zero degrees azimuth (facing south) has the highest efficiency compared to other scenarios and shows an energy efficiency of 35.54%, which indicates an acceptable decrease. The heating energy has been effective as well as its efficiency as a combined photovoltaic system in producing energy and controlling solar radiation simultaneously. The present study provides the required information on the parameters of Photovoltaic-integrated Shading systems and paves the way for the development of photovoltaic technology integrated with building components in the design steps.

The smart facade system is known as one of the main elements of the building envelope with optimal efficiency, which is able to respond to environmental stimuli and seeks to improve the comfort of residents and optimize energy consumption. While building design research has addressed the technical aspects and design of smart facades, very limited historical studies have been conducted on the evolution of such systems. Therefore, the current research examines the factors affecting the design and development of smart facades in cities to optimize energy consumption based on a historical period. This article examines and classifies the effective historical components in the evolution of the design and development of the smart facade system using the historical hierarchy method. The effective components in the form of socio-cultural, technical, political, environmental and economic categories are caused by revolutionary changes in art, technology and building construction from the 19th century onwards. The findings showed that the historical timeline presented in this article is considered as a useful resource for researchers and educators in research and educational activities. Based on this table, the current development pattern can be understood and possible future events (trends) can be predicted. The timeline shows that smart facades can be used in the future on an urban scale for all neighborhoods of cities, which helps to improve the comfort of residents and improve energy consumption in cities.

Today, due to the need for data centers, the issue of energy supply required by these centers is very important. Much of the energy consumed in data centers is related to the need for continuous cooling. Therefore, it is necessary to study air distribution, as one of the most important factors in energy saving, greenhouse gas production and increasing cooling. In this research, the data center has been simulated using Design Builder software (DB), and once the air has been distributed from the floor and once from the ceiling. This study was conducted in Mashhad over a period of one year and the results such as energy consumption, server room temperature, initial costs for each system and carbon dioxide emissions, which is one of the most destructive greenhouse gases, were compared. The simulation results showed that under exactly the same conditions with proper distribution of air in data centers can reduce room air temperature to increase room cooling and equipment, energy consumption, energy costs as well as greenhouse gas emissions and production costs. By using the floor air distribution plan, there is an average temperature reduction of 4.5 celsius degrees, 91.5 kWh of energy reduction, 55.5 kg of carbon dioxide emissions, and as a result, there is a $ 90.78 cost reduction compared to the roof air distribution plan per year.

Variable refrigerant flow systems are one of the most efficient and widely used air conditioning systems to reduce energy consumption while maintaining the desired level of thermal comfort. Variable refrigerant flow systems as an efficient and flexible solution for various heating/cooling applications are gaining more attention and are widely used in commercial and residential buildings. Variable refrigerant flow systems have many advantages over traditional air conditioning systems such as chillers and fan coils or air conditioning units, including satisfactory partial load performance, individual control capability at arbitrary temperature range, and no loss in duct transmission. Easy installation and maintenance. However, variable refrigerant flow systems require a dedicated outdoor air system with an additional ventilation unit.

This section first discusses the design of a variable refrigerant flow system. The next step is to model the building located in Cyprus with the heating system in question. The parts of this modeling include the characteristics of the selected location of the building, modeling of the relevant building, modeling of variable refrigerant air conditioning system and photovoltaic systems in detail.Variable refrigerant flow systemVariable refrigerant flow systems Among the various air conditioning systems is the DX system, based on the standard Rankin reverse steam compression cycle. Therefore, these systems are thermodynamically similar to conventional DX systems and have similar equipment such as compressor, expansion valve, condenser, and evaporator. Figure (1) shows the inside of the exterior of a variable refrigerant flow system that is installed outside the building.A 5-storey residential building with an area of ​​1061 square meters of space has been modeled in Design Builder software (on each floor, there are two residential units with ​​110 square meters). Each floor consists of two units with an equal area; the north-facing unit has two bedrooms, the south-facing unit has three bedrooms, and the ground floor is uninhabited and without air conditioning. In addition, the corridors between adjacent apartments on each floor are also without air conditioning. This research will focus on the power consumption of the variable refrigerant flow system as an electric charge. Figure (2) shows a schematic of an integrated photovoltaic variable refrigerant flow system.

In this section, energy consumption in variable refrigerant air conditioning, power generation of photovoltaic arrays, and carbon dioxide reduction due to photovoltaics are examined according to the results obtained from the design of builder designs.

The intensity of solar radiation in this city equals 1852kWh, and the annual electricity consumption of a refrigerant flow system varies around 18500kWh. The results show that according to the duration of sunlight during the day, the total daily electricity produced by photovoltaics provides only 54% of the daily electricity required for variable refrigerant current, which has a significant impact on reducing electricity consumption from the grid and a significant impact on Reduces carbon dioxide by 14 tons per year.    Figure 1. Internal view of the outer part of the variable refrigerant flow  Figure 2. Schematic of VRF-PV integrated system   Figure 3. DNI radiation status of the sun kW/m2 on July 21 Figure 4. Energy rate status of a building unit on July 21 Figure 5. External and indoor temperature status of a unit (dining room facing south on the 5th floor of the building), on July 21 Figure 6. Status of carbon dioxide emissions on 21 July Figure 7. DNI and DIF solar radiation conditions kW / m2 in summer and autumn Figure 8. Electricity status (Kw) required for cooling and photovoltaic power generation in summer and autumn Figure 9. External temperature and temperature of the dining room facing south on the 5th floor of the building, in summer and autumn

One of the most widely used electrical appliances is compression refrigeration systems or air conditioners, the split type of which is one of the most used air conditioners in hot areas. In such coolers, condenser plays a key role in its efficiency. The aim of this study was to investigate the effect of solar radiation and environmental factors such as temperature, humidity and wind speed on the amount of electrical energy consumption of split air conditioners. The study was conducted experimentally in spring and summer. In order to study the effect of solar radiation, three different angles have been considered for the location of the condenser, which include south latitude, 45 degrees to the left and right, as well as east in the morning and west in the afternoon. The results show that when the condenser is in the 90 degrees position (east-west) due to reduced radiation, the amount of energy consumption is reduced by up to 6% compared to the zero degrees angle and parallel to the south.

This article introduces direct and indirect evaporative cooling systems. Then a special type of indirect evaporative cooling systems working based on the Maisotsenko cycle is introduced. Systems based on the Maisotsenko cycle can ideally reduce the inlet air temperature to the dew point temperature of the inlet air. The wet-bulb efficiency of these systems is higher than other indirect evaporative cooling systems. These systems can reduce energy consumption up to 90% compared to traditional ways. In the following, by classifying the different climates of Iran, the possibility of using this system in different cities of Iran has been investigated. The obtained results show that due to the different climatic conditions of cities of Iran, using these systems is not suitable for cities with high relative humidity and large difference between dry-bulb and dew point temperatures such as Rasht, Sari, Ramsar, and Ardabil.

In this paper, the energy consumption of a household freezer is compared with a constant speed compressor and a variable speed compressor. The highest grade of energy consumption in household freezers is related to household freezers with variable speed compressors. To compare energy consumption in household freezers, a single speed compressor with a cooling capacity of 185 watts and a performance factor of 1.92, and a multi speed compressor with different speeds in terms of revolutions per minute 1300, 1600, 2000, 3000, 4500 and with a cooling capacity of 85, respectively., 108, 130, 200, 260 watts and performance coefficients of 1.80, 1.88, 1.90, 1.80, 1.60 were used respectively. In both compressors, one type of hydrocarbon gas is used and the amount of refrigerant in both types is almost equal. The experimental results showed that variable speed systems, in addition to more stable temperatures and reduced energy consumption, also cause rapid freezing due to their different speeds. A variable speed compressor reduces energy consumption by 24% per day compared to a constant speed compressor.

Optimizing and reducing the fuel consumption and thus preserving national economic resources is one of the important goals in the economy of any country. Using the natural gas instead of liquefied petroleum fuels and reducing energy consumption in industries such as cement can be a practical solution to meet the above-mentioned goals. In this study, numerical simulations are performed to enhance combustion and calcination processes in the Hormozgan cement plant calciner. To such aim, various optimizations are carried out to replace highly pollutive expensive, mazot fuel with natural gas and to improve calcination and combustion processes. Obtained results show that proposed modifications give the calciner the capability to be operated by 100% natural gas, while they reduce the energy consumption and pollutant emissions significantly. Finally, the best proposed case is implemented in the cement calciner to replace mazot by natural gas and reduce energy consumption and pollutant emissions. Site data clearly validate the proposed modifications to be effective enough to achieve all the objectives of the project.

The present study investigates the effect of office building orientation on energy consumption, solar heat gain and carbon production in three climates. Using Designer Builder software, simulations are performed on a sample building in Bushehr, Bandar-Abbas, Shiraz, Yazd and Tabriz in different orientations. Based on the results, building faced exactly to the south has the most favorable conditions. Buildings with 0 and 180 orientation have minimum energy consumption while maximum energy consumption is in other orientations. The most unfavorable orientations in Bushehr, Bandar Abbas, Shiraz, Yazd and Tabriz are 80, 70, 85 and 68 degrees, respectively. Best orientation in terms of energy consumption and reduced carbon is the same, and only in Tabriz maximum carbon is produced at 83 degrees orientation. The difference in energy consumption is 2.9 to 5.4 percent and 1.9 to 5.6 percent for corresponding carbon production. The results are in contrast to the general recommendation for building design to face south-east orientation.

Seawater greenhouse using humidification-dehumidification method can desalinate saline water and utilize fresh water for the greenhouse and drinking. Many parameters affect the performance of the seawater greenhouse. In this study, the effect of the width and length of the greenhouse, the height of the first evaporator and the roof transparency parameters on the energy consumption in the seawater greenhouse were investigated with the artificial neural network method. Artificial neural networks of the multi-layer perceptron (MLP) have been used for modeling. An appropriate structure for this method was obtained and the mathematical statistics of %AARE, RMSE and R2 were used to evaluate the network performance. The existing method is in good agreement with experimental data. Using this optimized network, the effect of each parameter on the energy consumption was evaluated. Finally, a greenhouse with a width of 125 meters, a length of 200 meters, an evaporator height of 4 meters, and a roof transparency of 0.6, which produces 161.6 m3/day of fresh water and 1.558 kWh /m3 of energy consumption, was introduced as an optimal seawater greenhouse.

Thermal properties of materials are one of the important factors determining cooling and heating load of the building. Buildings environmental sustainability is affected by energy consumption and harmful emissions of materials. Therefore, in addition to thermal properties, material life cycle and embodied energy and carbon should also be considered. The purpose of this study is to investigate the effect of different materials on thermal performance and energy efficiency in office buildings. For this purpose, materials with different thermal properties in 18 states are considered in a typical building for ceilings, floors, exterior and interior walls. Thermal simulations have been done using Designbuilder Software for Bushehr, Shiraz and Tabriz for a typical year. Based on the results, the best and worst modes in terms of energy consumption and produced carbon are the same in three cities but not similar to discomfort hours. This is due to the difference in amount of cooling and heating loads in various climates. The difference between the best and worst modes is 24 to 46 percent in energy consumption, 25 to 43 percent in carbon dioxide and depending on the climate 6 to 134 percent in discomfort hours.

In this paper, a control system with two layers is analytically designed using prediction-based optimal control method for nonlinear vehicle dynamics. In the first layer, an optimal external yaw moment for stabilizing the vehicle lateral dynamics is designed. After transforming this external yaw moment to differential forces between the four wheels and by using the inverse tire model for extraction of desired longitudinal slips, the desired values are sent to the second layer. In the second layer, each wheel motor regulates the control torque to track the desired slip. Since the energy consumption of battery is important in electric vehicles, considering the optimal control idea for designing the torque vectoring system reduces the battery consumption.Therefore, by examining suitable weighting factors, the electric motors are forced to operate within the admissible range and also the minimum usage of batteries are provided. The simulation results demonstrate that the designed control system has a suitable performance to cope with nonlinearities and consequently stabilizes the vehicle.

The combustion system used by the Hoffman furnaces for brick factories has a very low efficiency. In the current paper, the performance of the combustion system of Hoffman furnaces of Kolet Pottery Brick Co has improved, using computational fluid dynamics (CFD) by making changes to the Hoffman furnace torch, including the converging the torch head, inserting the spring in the pipe to create the swirl flow, shortening the nozzle length for the better mixing of the fuel and air, and more. The changes were simulated in each step with the FLUENT simulation software. Based on the theoretical results and simulation, optimized torch was made and a field test was carried out on it in a brick factory and the gases from their combustion were analyzed. As a result of these reforms, the combustion efficiency of the Hoffman furnaces has increased from 27% to 47 %, and consumption of fuel oil has decreased by a third. Also, the CO value of 16854 ppm in the old torch was reduced to 298 ppm in the optimized torch and the NO value ranged from 49 to 18 ppm as a result of optimizations.

In dense occupancy spaces, providing the proper conditions especially as indoor air quality is very important. On the other hand, in most air distribution systems, the ventilation performance and energy saving parameters are greatly influenced by the arrangements of supply diffuser positions. Therefore, in this study, the effects of supply diffuser positions on thermal comfort, indoor air quality and energy consumption in an amphitheater have been investigated. For this issue, a small amphitheater with 50 occupants has been modeled under the conditions that the linear air inlet diffusers located in four situations. The results indicate that the displacement ventilation can provide the proper conditions. However, by changing the location of supply diffuser positions, IAQ and occupants comfort can be improved. For example, for the inlet diffusers are located vertically on the floor, relative ventilation effectiveness is improved about 20% and CO2concentration is decreased about10% in comparison with the other cases.