Iranica Journal of Energy & Environment
Volume:15 Issue: 4, Autumn 2024

The challenge of particle deposition in microchannels has consistently posed issues in nanofluids, adversely impacting the heat transfer rate. This study investigates the novel approach of employing a magnetic field to prevent deposition and enhance the heat transfer of nanoparticles in microchannels, utilizing Euler-Lagrange method. The analysis involves the coupled solution of momentum and energy equations, incorporating forces such as Brownian motion, thermophoresis, drag, and volumetric force. The findings within the explored parameters indicate that temperature variations affecting particles beyond the thermal boundary layer have a comparatively minor impact compared to those within the boundary layer. This presents an opportunity for optimizing nanoparticle consumption. Additionally, the study reveals that a non-developed flow at the inlet results in lower particle deposition compared to a developed inlet. The results show that an increase in the Reynolds number from 50 to 300 leads to a 1.75% increase in the distance of particles from the wall. The study also delves into the positioning of the current-carrying wire, demonstrating that placing the wire at the microchannel entrance significantly reduces particle deposition. Furthermore, the results indicate that with an increase in electrical current up to 4 amperes, the efficiency of non-deposition reaches 100%.

Herein, a non-boiling two-phase flow containing air and water through a downward flow in a vertical tube with helical corrugations has been investigated. In this simulation, various flow rates for air and water are considered, and three corrugation pitches 1, 1.5, and 2 cm are included. It can be seen in the results that the pressure drop values decrease with an increase in volume fraction. It should be noted that the reduction of pressure drop values with the reduction of volume fraction (VF) is based on the reduction of the water flow rate, which is visible. By comparing the pressure drop values for each corrugation pitch, it can be seen that as the pitch decreases, the pressure drop values increase significantly. The results for Nusselt number show that Nusselt number decreased with an increase in the volume fraction. By reducing the water flow rate, the intensity of the main flow is reduced the intensity of turbulence is also reduced and the heat transfer coefficient is reduced. Ultimately, the cost-benefit ratio has been utilized to show real results for each studied case.

In this article, the concentration of some volatile organic compounds (VOCs) in the hot oil sample of the Pars petrochemical ethylbenzene unit is presented. Pars Petrochemical is one of the largest producers of ethylbenzene in the Middle East. The hot oil impurities that were analyzed were benzene and toluene (BT). The hot oil sample was taken in May 2023 at a special sampling station on the site. The presence of BT is related to its intensity in the hot oil sample. The Multiple Headspace Extraction (MHE) method was used for the extraction and quantitative analysis of BT followed by gas chromatography (GC) analysis. A GC with flame ionization detector (FID) instrument was used for the analysis of BT. This method offers advantages for the analysis of volatile pollutants because it eliminates the use of organic solvents and various sample purification steps that often lead to erroneous results. The MHE method is independent of standard concentration and could be used in a wide range of BT in Hot Oil without calibration for different ranges. Also, linearity, detection limits, and accuracy were looked into as part of the validation process. The limit of detection (LOD) and limit of quantification (LOQ), respectively, were between 0.05 - 0.56, and 0.17 - 1.9 mg/kg. Less than 13.95 percent (n= 15) was the relative standard deviation statistically. A quick and easy method for detecting BT in hot oil samples was used for the first time. This work will be a step forward for the detection of other aromatic and cyclic hydrocarbons in hot oil samples.

Considering that the heat required for the Waste heat recovery (WHR) cycle of the engine is provided from two parts of the exhaust gas and the cooling system, the mutual influence of the WHR cycle on the engine performance is undeniable. Therefore, in this numerical study, an attempt has been made to thermodynamically evaluate the effect of the implementation of the WHR cycle on the engine efficiency. For this purpose, the 16 cylinder MTU 4000 R43L heavy diesel engine was simulated and a comparison was made between numerical and experimental results. Finally, the SRC heat recovery cycle was designed and applied in the simulated model according to the desired limits and the temperature range of the engine operation. At low speed with the application of the WHR cycle, the output net power did not drop much, but at the maximum speed and power, a power loss of about 4% is observed. At 1130 rpm, the power did not increase much. At 1600 rpm, the power increase is reduced to about 2.3%. At 1800 rpm, due to the significant increase in exhaust gas temperature, the total power value increased by about 4%.

Insisting on independently providing energy due to fossil fuel availability and Economic-political purposes has imposed financial-environmental risks on countries. Inefficient obsolete infrastructures and technologies have caused devastating losses causing technical vulnerabilities in the energy sector. Ungainful increasing consumption of water resources has superimposed severe environmental degradation, threatening long-term energy planning. Successively, the energy security debate has turned into a challenging necessity for countries. This study developed a classic approach based on Modern Portfolio Theory (MPT) and Capital Allocation Line (CAL) reinforced with aggregated evaluative measures to deal with the financial-environmental complexities of national energy portfolios. Results prove that countries are not even aware of the risky hidden brittleness of their energy portfolio. Futuristic policymaking should be adapted to gradually change the national energy structure from fossil fuel dependency to portfolio thinking to avoid risks and achieve more security.

The purpose of this research is to analyze the energy of a residential building in the city of Tabriz with a cold and dry climate using energy simulation to provide a model to minimize energy consumption. A comparative model of energy consumption analysis in a three-story building unit with dimensions of 181 square meters is presented using 5 layout modes in the wall, floor, ceiling, window and door. The number of 5 designs with different arrangement of rooms and different number of windows were compared in terms of energy conservation in 51 different diagrams and the optimal energy saving design is selected. In the next step, according to the obtained results, the design of the building in the desired site is discussed. At the end, in order to check the amount of energy absorbed in the building, energy diagrams will be obtained for the thermal region of the coldest day of the year. The results show that the most optimal energy consumption of the residential building is related to the design of plan B with the fabric gains value of 41767 Wh. After that, the designed plan A show the most optimal energy consumption in the building with fabric gains value of 41028 Wh in the month of July. The results of this research are useful for energy ‎efficiency of residential buildings and environmental management in future.

The use of microchannel heat sinks is one of the most popular methods for cooling electronic components. In recent years, fractal microchannels have attracted researchers' attention, leading to increased heat transfer and reduced pressure drop compared to parallel microchannels. In this study, two hybrid nanofluids under laminar flow conditions are used for cooling inside microchannels, and simulations are conducted using COMSOL Multiphysics software. Parameters such as pumping power, maximum temperature, and performance evaluation coefficient are investigated for two hybrid nanofluids, Fe3O4-MoS2 and Fe3O4-Al2O3 (mixed 50%-50% and with a volume fraction of 1% for each nanoparticle). The results indicate that the thermal performance of Fe3O4-MoS2 hybrid nanofluid is superior, leading to a 0.5% improvement in the maximum temperature of the heat sink. On the other hand, the use of this hybrid nanofluid increases pumping power by 9% inside the microchannel. Ultimately, the overall system performance is enhanced with the use of both hybrid nanofluids, and the Fe3O4-MoS2 hybrid nanofluid improves the overall system performance by 3.2%, providing better performance and making it more suitable for cooling microchannel heat sinks.