Temperature Flow Research Articles

Numerical study of Mg(OH)2/MgO thermochemical heat storage reactor coupled with parabolic dish solar system

Systems coupling Mg(OH)2/MgO thermochemical reactor with parabolic dish solar collector (PDSC) have a potential application prospect in solar seasonal heat storage. However, their working mechanism has not been systematically studied and not well understood either. In this study, Mg(OH)2-based thermochemical reactor, which was coupled with PDSC, was numerically studied for the first time using a three-dimensional model. The various working conditions and influencing factors of PDSC system were investigated, and a comprehensive analysis and optimization for the heat storage performance of the reactor such as the reaction time and energy storage rate were conducted. Effects of the fluid inflow temperature, velocity, and fluid pipe distribution on heat storage performance were also unfolded. For instance, when the heating pipe was arranged at 70 mm from the central axis, the reaction time was 15.9 % less than that of evenly arranged at R/2 from the center. Moreover, fins were added to the reactor and the fin shape was optimized using the density-based topology optimization method. It was found that the reaction time was reduced by 42.4 % and was only 12614 s.

Effects of the inflow total temperature on the non-premixed rotating detonation engine performances

As a promising propulsion system, air-breathing rotating detonation engines (RDEs) are investigated with significant interest recently. However, simulations of air-breathing RDE with real flight condition are limited, and performance of RDEs with high inflow total temperature, as well as the influence of inflow total temperature on RDEs, needs further exploration. In this paper, simulations with four inflow total temperatures (300 K, 500 K, 700 K and 900 K) were conducted to analyze the propagation features of rotating detonation waves (RDWs) and operation modes in the RDE at low and high inflow total temperatures. Additionally, injection and mixing, as well as combustion characteristics and propulsion performance of the RDE were researched. It is found that with low inflow total temperature, single wave propagates in the combustor, which degenerates into shock wave at the outer wall due to insufficient mixing. When inflow total temperature is high, the RDE is in multi-wave operation mode and detonative combustion only occurs around the outer wall. With increase of inflow total temperature, mixability of reactants initially improves but then deteriorates slightly. Moreover, RDW propagation velocity and specific impulse of the RDE decrease. Though fuel utilization rate improves, detonation fraction drops dramatically and parasitic combustion fraction rises significantly, resulting from intensification of pre-combustion. Particularly, the detonation fraction is only 16.7 % and parasitic combustion fraction reaches up to 56.35 % at inflow total temperature of 900 K. Furthermore, regardless of the variation of inflow total temperature, detonative combustion is prominent in the premixed combustion mode, and the peak fraction of detonation appears at the off-stoichiometric ratio.

Experimental testing of additively manufactured embedded fiber optic smart devices for clean energy applications

Abstract An additively manufactured prototype smart device was created to investigate in-flow temperature distributions using embedded high-definition fiber optic sensors within a component for clean energy systems. The devices were created using Ultrasonic Additive Manufacturing to create a unique embedded pathway within a flow conditioner for the high-definition fiber optic sensors to be placed within. The fibers used allowed for temperature measurements to be taken every 0.65 mm along the fiber. The high-resolution fibers were thermally calibrated enable the 2D reconstruction of the temperature profile in the flow path of the structure. This is due to the temperature-related strain response of the material and strain measurements of the fibers. Hot airflow testing of these devices showed the ability to identify localized temperature differences in the flow. The observed strain response within the smart device had higher strain concentrations in the thicker web regions than in the thinner web regions. These higher strain regions resulted in higher uncertainties for the temperature responses. Further calibration is needed to improve the accuracy of the smart devices, specifically within the inner web structures of a flow straightening component. Further investigations of the devices within flow showed the temperature sensing to be independent of the effects of flow velocity. The devices were able to distinguish temperature differences within single and two-phase flow and showed local sensitivity to the temperature changes with the identification of hot and cold spots. The presented results showed the viability of the smart device for obtaining detailed temperature distributions using common industrial components. Eventually, the goal for these smart devices will be to withstand higher temperature and pressure environments such as those experienced in nuclear, fusion, and concentrated solar energy systems.

Experimental investigation on an innovative serpentine channel‐based nanofluid cooling technology for modular lithium‐ion battery thermal management

AbstractMany nations have committed to becoming carbon neutral by 2050 as a means of addressing the global warming challenge. To achieve carbon neutrality, transportation is one of the most essential and important tasks. Energy‐efficient pure electric vehicles (EVs) and hybrid electric vehicles (HEVs) with green energy power are being developed in response to the worldwide energy and environmental crises, as the potential replacements for the current generation of combustion‐engine automobiles. EVs require batteries more than ever before. In this perspective, lithium‐ion batteries (LIBs) stand out as remarkable energy storage technologies and have been widely used due to their numerous impressive benefits. Owing to LIBs sensitivity to temperature, EVs typically use the battery thermal management system (BTMS). The working temperature span of a lithium‐ion battery in an electric car is 15°C–35°C, which is achieved by the use of a BTMS. The production of internal heat during charging and discharging also affects how well lithium‐ion batteries work. A battery heat control system is therefore required. The temperature of the LIB pack might be efficiently controlled by liquid‐cooled systems in discharge and charge scenarios. Based on Al2O3 nanofluid (NF), the current experimental study suggests a novel active cooling technology for regulating the heat produced by the 18650‐format lithium‐ion batteries. A thorough analysis is conducted on the impact of charge/discharge C‐rates, Al2O3 nanoparticle (NP) volume fractions, inflow coolant velocity, and intake liquid temperature on the thermal efficiency of the LIB pack. By incorporating aluminum oxide NPs into the water at varying volume fractions of 0.3%, 0.5%, and 1%, the LIB pack's maximum temperature was significantly reduced by 7.9%, 18.09%, and 19.56%, respectively. With increase in mass flow rate of coolant from 0.0290 to 0.5810 kg/s, the maximum temperature has been substantially reduced by 3.7%–8.6%. Results show that using higher fluid inflow temperature significantly increased both the highest experienced temperature and temperature diversity throughout the discharge operation by about, 6°C and 5°C, respectively. The outcomes of the study indicate that NFs exhibit superior cooling performance compared to conventional coolants such as water and ethylene glycol.

Numerical and experimental investigation of the supercooled large droplets icing of rotating spinner

The icing of aero-engine rotating components is more complex than traditional aircraft icing. A three-dimensional numerical method was developed based on the Eulerian method to study the supercooled large droplets icing of a rotating spinner. Typical dynamic behaviours of supercooled large droplets, such as deformation, breakup, rebound, and splashing, were considered. An icing thermodynamic model applicable to a rotating spinner was established by considering the effects of pressure gradient, air shear force, and centrifugal force on the flow of the water film. Meanwhile, an ice wind tunnel experiment on supercooled large droplets icing of a rotating spinner was carried out. The results showed that the maximum relative deviation of the simulated icing thickness at the cone tip is no more than 15% compared with the experimental result, and the icing thickness on the surface of the rotating spinner is basically consistent with the experimental result. Based on the three-dimensional numerical method developed in this study, the effects of the rotational speed, inflow velocity, and inflow temperature on the supercooled large droplets icing of a rotating spinner were investigated. As the rotational speed increases, the rebound and splashing of supercooled large droplets becomes more obvious, leading to an increase in the mass loss coefficient and a decrease in the collected mass of water droplets on the surface of the rotating spinner. Consequently, the icing thickness at the tail of the rotating spinner decreases with an increase in the rotational speed. Since the liquid water content in the environment is relatively low, water droplets freeze immediately after impacting the surface of the rotating spinner and rime ice is usually formed. When the inflow temperature is relatively high, overflow water exists and glaze ice is formed near the tip of the rotating spinner. The findings of this study can provide valuable support for the design and verification of anti-icing systems for aero-engine rotating spinner.

Co-melting mechanisms for municipal solid waste incineration fly ash with fine slag from coal gasification and coal gangue

Vitrification is a promising treatment for municipal solid waste incineration fly ash (MSWI-FA); however, high energy consumption due to the high MSWI-FA fusion temperature limits the development and application of this technique. In this study, fine slag ash (FSA) derived from coal gasification and coal gangue ash (CGA) were mixed with MSWI-FA to reduce the ash fusion temperature. The transformation of minerals in ash during thermal treatment was examined via X-ray diffraction and thermodynamic equilibrium calculations. The ash flow behaviour was observed using a thermal platform microscope, and the silicate structure was quantified using Raman spectra. The co-melting mechanisms for the mixed ash were systematically investigated. Results indicate that the flow temperature (FT) of the mixed ash exhibited an initial decrease and subsequent increase as a function of the addition ratio of FSA or CGA. Lowest ash FT of 1215 °C and 1223 °C were recorded for addition of 50% FSA and 50% CGA, respectively; further, these temperatures were lowered by > 285 °C and >277 °C respectively, relative to FT of the MSWI-FA. The transformation of minerals and silicate structure during mixed ash heating was responsible for the variation in the ash fusion temperature. CaO in MSWI-FA tended to react with mullite, quartz and haematite in FSA and CGA, forming minerals such as anorthite, gehlenite, and andradite with relatively low melting points. The addition of FSA or CGA caused changes in the silicate network structure of the mixed ash. In particular, 50% FSA incorporation caused the transformation of Q4 and Q3 to Q2, whereas 50% CGA introduction resulted in the conversion of Q4 and Q2 into Q3 and Q1 + Q0, respectively. The silicate network depolymerised, causing reduction in the ash fusion temperature and increasing the melting rate.

Expansion wave-reinforced initiation of the oblique detonation wave

Efficient initiation of oblique detonation waves (ODWs) is crucial for optimizing the performance of oblique detonation wave engines. A novel approach is proposed for enhancing ODW initiation through expansion waves in this research. Validation of the expansion wave-reinforced initiation method is conducted via numerical simulations employing multi-species reactive Euler equations and a pressure-dependent reaction mechanism. Results demonstrate a significant reduction in the initiation length of ODWs with the addition of an expansion wave ahead of the wedge, contrasting with the absence of detonation wave initiation on a wedge lacking an expansion wave. A theoretical model, based on expansion wave and shock wave relations, along with constant volume combustion theory, elucidates the underlying mechanism of reinforcement. The model reveals that crossing the expansion wave elevates the fluid's Mach number and locally enlarges the flow deflection angle on the wedge surface, without altering the wedge's structure. Furthermore, post-shock temperature increases and pressure decreases compared to the wedge not encountering an expansion wave. The heightened temperature predominantly triggers ODW initiation, thus reinforcing the process. Theoretical analyses indicate the reinforcement's greater efficacy at lower inflow temperatures and lower inflow Mach numbers, suggesting the expansion wave's suitability for initiation in the early flight stages of an aircraft equipped with oblique detonation wave engines.

Effect of High Calcium and High Iron Coal on Ash Fusion Characteristics of Petroleum Coke during Cogasification.

Entrained flow gasification provides a more efficient utilization method for high-sulfur petroleum coke. The operation temperature of the entrained flow gasifier must be above the ash fusion temperature (AFT) of petroleum coke due to the liquid slag discharge. In this work, petroleum coke was blended with high-calcium coal and high-iron coal, respectively, under a reducing atmosphere, and the variations in AFTs were recorded by an ash fusion temperature analyzer. The influence of mineral transformations on the ash fusion characteristics of blended ash was analyzed by X-ray diffraction and FactSage. The results showed that both high calcium coal and high iron coal could efficiently reduce the AFTs of petroleum coke. When the ratio of high calcium coal and high iron coal reached 60 wt %, the corresponding flow temperature (FT) of mixed ash decreased to 1225 and 1312 °C, respectively. With the content of high calcium coal increasing, coulsonite (FeV2O4), vanadium trioxide (V2O3) and nickel (Ni) with high-melting points tended to decrease, causing the decrease of AFT for mixed ash. As high iron coal was added, Ni and V2O3 continuously kept decreasing. In particular, the percentage of FeV2O4 first increased and thereafter decreased with high iron coal above 40 wt %.

Central Heating Control Charts for the Economic Use of Energy in Residential Buildings

Methods and types (qualitative, quantitative or mixed) of control of central heating installations in residential buildings are presented. Measurements were made for a radiator in a central heating system that was powered by a heating node substation. The output temperature of the heat node supplying the residential building, in which the test stand was located, was compared with the measured supply and return temperature. Indoor room temperature, outdoor air temperature, inflow and outflow temperature on the vertical supplying the heater were also recorded and analysed. These data were compared with the control charts of the heat networks allowing for direct readings of the required feed water temperature for a given outdoor temperature according to the Heat Energy Enterprises data. The differences are accordingly presented. The actual measurements, read at the test stand located on the 2nd floor of the 4-storey building with input parameters of 90/70 °C during the entire month of December 2022, are recorded every 6 hours and are tabulated and displayed in comparison charts with the calculated parameters. Inflow and outflow temperatures values on the vertical supplying the heater and the values of outdoor temperature measured by a sensor were analysed. The temperatures supplied to the radiators in the apartments were also compared with the requirements of electronic heating cost allocators contained in the PN EN 834 standard. New design temperatures for the central heating installation were proposed due to the requirements of the electronic heating cost allocator.

Transient experimental study on cooling performance of a radial turbine with impingement cooling in rotating state

Increasing the inflow temperature of a turbine is an effective approach for enhancing the thermal efficiency of devices operating in the Brayton cycle, such as micro-gas-turbines and waste heat recovery systems. However, elevated temperatures also pose a significant risk of thermal fatigue failure. This paper presents an experimental investigation of impingement cooling for radial turbines, aiming to achieve high cooling performance with a simple structure. High-frequency infrared thermal imaging technology was employed to measure temperature distribution in the turbine rotor under various operational conditions. The results indicate that jet-impingement cooling can substantially reduce the solid temperature of the radial turbine, with a maximum temperature reduction of approximately 44 K achieved by consuming the coolant with ṁre= 5%. Increasing the mass flow rate of the coolant consistently lowers the rotor temperature; however, an increase in rotational speed results in higher thermal inertia, thereby diminishing the cooling enhancement effect. The temperature distribution on the turbine surface exhibits significant periodic characteristics over time, leading to temperature fluctuations of 5 K to 30 K at the hub position. Furthermore, the cooling performance is further enhanced near the jet hole on the back-disc side of the inducer region, while the tip side closer to the exducer obtains better cooling effects.

Development of a multi-objective reservoir operation model for water quality-quantity management

This study aims to develop a multi-objective quantitative-qualitative reservoir operation model (MOQQROM) by a simulation-optimization approach. However, the main challenge of these models is their computational complexity. The simulation-optimization method used in this study consists of CE-QUAL-W2 as a hydrodynamic and water quality simulation model and a multi-objective firefly algorithm-k nearest neighbor (MOFA-KNN) as an optimization algorithm which is an efficient algorithm to overcome the computational burden in simulation-optimization approaches by decreasing simulation model calls. MOFA-KNN was expanded for this study, and its performance was evaluated in the MOQQROM. Three objectives were considered in this study, including (1) the sum of the squared mass of total dissolved solids (TDS), (2) the sum of the squared temperature difference between reservoir inflow and outflow as water quality objectives, and (3) the vulnerability index as a water quantity objective. Aidoghmoush reservoir was employed as a case study, and the model was investigated under three scenarios, including the normal, wet, and dry years. Results showed the expanded MOFA-KNN reduced the number of original simulation model calls compared to the total number of simulations in MOQQROM by more than 99%, indicating its efficacy in significantly reducing execution time. The three most desired operating policies for meeting each objective were selected for investigation. Results showed that the operation policy with the best value for the second objective could be chosen as a compromise policy to balance the two conflicting goals of improving quality and supplying the demand in normal and wet scenarios. In terms of contamination mass, this policy was, on average, 16% worse than the first policy and 40% better than the third policy in the normal scenario. In the wet scenario, it was, on average, 55% worse than the first policy and 16% better than the third policy. The outflow temperature of this policy was, on average, only 8.35% different from the inflow temperature in the normal scenario and 0.93% different in the wet scenario. The performance of the developed model is satisfactory.

Interacting impacts of hydrological changes and air temperature warming on lake temperatures highlight the potential for adaptive management.

Globally, climate warming is increasing air temperatures and changing river flows, but few studies have explicitly considered the consequences for lake temperatures of these dual effects, or the potential to manage lake inflows to mitigate climate warming impacts. Using a one-dimensional model, we tested the sensitivity of lake temperatures to the separate and interacting effects of changes in air temperature and inflow on a small, short-residence time (annual average ≈ 20days), temperate lake. Reducing inflow by 70% increased summer lake surface temperatures 1.0-1.2°C and water column stability by 11-19%, equivalent to the effect of 1.2°C air temperature warming. Conversely, similar increases in inflow could result in lake summer cooling, sufficient to mitigate 0.75°C air temperature rise, increasing to more than 1.1°C if inflow temperature does not rise. We discuss how altering lake inflow volume and temperature could be added to the suite of adaptation measures for lakes.

Radiatively cooled magnetic reconnection experiments driven by pulsed power

We present evidence for strong radiative cooling in a pulsed-power-driven magnetic reconnection experiment. Two aluminum exploding wire arrays, driven by a 20 MA peak current, 300 ns rise time pulse from the Z machine (Sandia National Laboratories), generate strongly driven plasma flows (MA≈7) with anti-parallel magnetic fields, which form a reconnection layer (SL≈120) at the mid-plane. The net cooling rate far exceeds the Alfvénic transit rate (τcool−1/τA−1≫1), leading to strong cooling of the reconnection layer. We determine the advected magnetic field and flow velocity using inductive probes positioned in the inflow to the layer, and inflow ion density and temperature from analysis of visible emission spectroscopy. A sharp decrease in x-ray emission from the reconnection layer, measured using filtered diodes and time-gated x-ray imaging, provides evidence for strong cooling of the reconnection layer after its initial formation. X-ray images also show localized hotspots, regions of strong x-ray emission, with velocities comparable to the expected outflow velocity from the reconnection layer. These hotspots are consistent with plasmoids observed in 3D radiative resistive magnetohydrodynamic simulations of the experiment. X-ray spectroscopy further indicates that the hotspots have a temperature (170 eV) much higher than the bulk layer (≤75 eV) and inflow temperatures (about 2 eV) and that these hotspots generate the majority of the high-energy (>1 keV) emission.

Solid biofuel preparation from eucalyptus bark by hydrothermal treatment and pelletization: Fuel properties, combustion behavior and ash slagging tendency

Eucalyptus bark (EB) is a promising biomass to replace fossil fuels, but its ash content is high and the energy density is particularly low. In this paper, it was proposed to upgrade EB to prepare solid biofuel by mild hydrothermal treatment (HTT) and pelletization. It was found that HTT could effectively remove troubling elements like Na, K, Zn, Mn, S, Cl, and P in EB. The remaining ashes tend to form higher melting point compounds, whose softening temperature (ST) and flow temperature (FT) increased from 1326 °C to 1399 °C and from 1348 °C to 1425 °C, respectively. The higher heating value of EB increased from 16.32 to 17.68 MJ/kg after HTT. The density, volume expansion, compressive strength, and durability of the bio-pellet fuel after HTT were all superior to raw EB. HTT and pelletization is a promising method to prepare solid biofuel from EB.

Efficiency upgrading of solar PVT finned hybrid system in Bangladesh: Flow rate and temperature influences

This research aims to determine the impact of mass flow rate and inflow temperature on the utility and effectiveness of solar thermal systems using fins with air in various applications in Bangladesh. This study examines a three-dimensional (3D) photovoltaic thermal (PVT) system where we analyze the behavior of a hybrid system with six aluminum sheets (1 mm thick fin as a heat exchange material) inside the heat exchanger where the air takes the direction to pass in waveform through the channels (made of aluminum) using fins. The top side of the fins is bent and affixed to the bottom of the floor of the PV panel to allow heat transfer utilizing the conduction-based method. This study selects inlet fluid mass flow rate and inflow temperature between (0.015–0.535 kg/s), and (10–40 °C) respectively, while comparing the result with experimental/numerical published data based on Bangladesh's weather conditions and applies the finite element method (FEM) to solve heat transfer equations. A brief analysis of the association among Reynolds number with pressure drop and fanning friction factor is included in this paper. Our model can be mounted on building rooftops or open fields where air velocity will be controlled mechanically; thus, it has many applications. This model can be implemented within an agricultural photovoltaic (APV) system, domestic functions, dry agricultural products, and provide heat for greenhouses. The result indicates that 302–514 W thermal energy has been produced for 0.015–0.535 kg/s. For growing inflow temperature, despite the reduction in electrical efficiency, the value of adding electrical and thermal efficiency (overall efficiency) comes with elevation. A 5 °C increase in inflow temperature leads to an overall efficiency increase of 0.33%. This study's findings can help researchers better comprehend air's properties as a heat exchanger in a developed design, and they can be applied to government and commercial projects.

Thermal performance of a solar water tank with variable inlet/outlet under various charging strategies

The plummet of the inflow temperature could cause dramatic temperature mixing during the charging process in a solar water storage tank, resulting in severe destruction of thermal stratification. To address this issue, two new charging strategies are proposed in this paper for the water tank with variable inlet and outlet ports. We study the charging process of the tank under various strategies using Computational Fluid Dynamics (CFD) simulation and assess the thermal performance improvement according to the numerical comparisons and theoretical analysis. A laminar numerical model considering gravity effect is built based on the experimental platform and is well validated against the experimental data. Energy and exergy analysis are conducted to evaluate the impact of the strategies on the thermal performance of the solar charging. The findings show that both the proposed charging strategies substantially mitigate the temperature mixing caused by the port switch and achieve a better thermal stratification with the reduction in exergy destruction by over 30%. Strategy A maintains better thermal stratification during the charging process, while strategy B prevails in inhibiting the temperature mixing after port switches. Nevertheless, the improvement in the overall thermal performance is relatively modest with the increment of less than 1% in energy efficiency and 0.02 in exergy efficiency.

Determination of Thermal Conductivity Constant for Spray-Dried Mung Bean Protein Isolate using Series-Parallel “Block” Method and Central Composite Design

The efficient production of mung bean protein isolate (MBPI) is essential for sustainable food processing, yet it is energy-intensive due to drying phase required to convert raw mung beans into a fine powder. This work was carried out to calculate the thermal conductivity constant (k) of protein (A), moisture (B) and residual carbohydrate (C) of spray-dried MBPI. The protein slurry was prepared by dissolving MBPI in water at the ratio of 1:3, 1:4, and 1:5 prior to spray drying. The protein slurry was then spray dried at three different inflow temperatures of 140, 160, and 180 °C. A Series and Parallel Combination "Block" Model in tandem with a Central Composite Design (CCD) were selected to calculate the thermal conductivity constant of A, B and C. Eight arrangement components on A, B, and C component, measurements were derived from the initial three data points by utilizing the CCD method, in the preliminary study. By utilizing the series-parallel approach and statistical combination, there are a total of forty study arrangements. The thermal conductivity of MBPI with arrangements of A, B, and C (pABC); and a series of combinations of A and C in parallel to B (sAC pB) ranged from 0.1964-0.224 Wm-1 ℃ -1, with R2 = 98.73%-99.42%. Therefore, the energy requirement of spray drying process for MBPI could be predicted by the thermal properties of each component selected in the protein isolate.

Assessment of the Possibility of Excluding Secondary Heating of the Inflow During the Warm Period in Modern Climatic Conditions

The subject of the study is the dependence on the required indoor air temperature and the accepted inflow temperature for a minimum heat and humidity ratio in the room, in which secondary heating of inflow can be excluded. The purpose of the study is to obtain an analytical expression of this dependence, which allows an engineering assessment of the possibility of eliminating secondary heating in the process of designing air conditioning systems without the use of graphical constructions. The objective of the study is to represent an adequate flow processing scheme on the I–d diagram, identify the main factors affecting the minimum heat and humidity ratio in the room and obtain the necessary numerical coefficients in formulas linking the desired and initial parameters. Research results. An analytical dependence is obtained that allows calculating the minimum possible value of the heat and humidity ratio in a room in which secondary heating is not required, and only cooling of the inflow with drying in a surface air cooler is sufficient if it has a bypass channel. The presentation is illustrated with numerical and graphical examples.

Combustion Characteristics and Application Performance of JP-10/Nano-Sized Aluminum Gel-Fueled Scramjet

Using nano-sized energetic materials as fuel additives to hydrocarbon gel fuel has gained in popularity due to the advantages of higher energy density and shorter ignition delay times. Combustion characteristics and application performance of gel fuel containing 16% wt aluminum nanoparticles were investigated on a direct-connect scramjet platform with an inflow Mach number of 2, an inflow total temperature of 1700 K, and a fuel equivalence ratio ranging from 0.6 to 1.0. The gel fuel could be stably injected and atomized efficiently by a nitrogen-assisted injector. The combustion efficiency of JP-10+Al gel fuel was 4.27% higher than that of JP-10 gel fuel, while the addition of aluminum increased the density specific impulse by 6.34%, indicating that the addition of aluminum nanoparticles indeed presented a positive effect on combustion and engine performance. The wall deposition phenomenon of gel fuel was particularly slight as compared to that of slurry fuel cases. Unlike nanoaluminum-blended slurry fuel, nanoaluminum-blended gel fuel controlled the potential risk of increasing thermal load to the least degree within the scope of existing research, with wall heat flux increasing by 7.43% solely as a result of elevated airflow temperature, indicating its advantageous application prospect.

Effect of crowd density, wind direction, and air temperature on the formation of individual human breathing zones in a semi-outdoor environment

This paper presents a comprehensive numerical investigation to predict the human breathing zones (BZs) in crowded semi-outdoor environments. The computational domain consisted of a nine-human block array with integrated nasal cavities subjected to the lower part of the atmospheric boundary layer. Five crowding levels, seven wind directions, and inflow ambient air temperatures (ranging from 10 to 31 °C) were tested to examine the horizontal and vertical formations of the BZs. Validation and verification tests were performed through comparisons with experimental results, a grid independence test, and an evaluation of various randomized distribution scenarios to minimize the uncertainties of the computational fluid dynamics analyses. The horizontal extension of the BZs tripled as the crowding level increased from 0.325 to 4.0 m2/capita. However, the lateral extension was insensitive and remained within 10 cm of the nostrils. Human models can inhale air close to the cheek, neck, and shoulders when an oblique flow is assumed. As the air temperature increased, individuals tended to inhale air from the upper regions, which was influenced by the interrelated thermal properties of the human body. Consequently, under high-temperature conditions, there may be an increased probability of gas-phase contaminant inhalation over greater horizontal distances.