Low-temperature Flow Research Articles

A low temperature and high-power density lignin flow fuel cell via an efficient CoMn-LDH electrocatalyst with superhydrophilic intercalation

A novel high-power density and low temperature lignin flow fuel cell was developed using efficient CoMn-LDH electrocatalysts with good electrical conductivity and high adsorption capacity for lignin. It achieves 269.3 mW cm−2 and works stably.

Effect of Tube Length on the Performance of Cooling Necklace with Vortex Tube Cold Flow Generator

The vortex tube, a compact and eco-friendly device, can generate both low-temperature cold flow and high-temperature hot flow from a room-temperature compressed gas supply. Despite its potential, there has been limited research on its application as a cooling device, particularly in the context of a cooling necklace. This study aims to fill this gap by examining the performance of the vortex tube under various conditions. The experiment was conducted indoors, with tube lengths ranging from 60 cm to 140 cm and inlet pressures from 0.2 MPa to 0.4 MPa. The results suggest that an inlet pressure of 0.4 MPa and a tube length of 60 cm are optimal for achieving the lowest temperature cold flow and minimizing heat transfer effects between the cold flow and the environment.

Study on the mechanical properties and acoustic emission signal characteristics of freezing pipe

The increase in freezing depth requires thicker, stronger, and colder freezing walls, and various complex factors in deep strata greatly increase the risk of freezing pipe fracture. To address the phenomenon of freezing pipe fracture, this paper designs freezing pipe and joint mechanical performance experiments based on acoustic emission (AE) technology, mainly testing the deformation of freezing steel pipes and composite joints at normal and low temperatures, changes in load bearing capacity, and corresponding AE characteristics of the process. Additionally, the associated AE characteristics throughout the process will be analyzed. The ultimate goal is to establish a discriminative pattern for identifying the critical fracture of freezing pipes based on the analysis of AE signal characteristics in conjunction with mechanical properties. The sensitivity of the AE system under low-temperature conditions and the reliability of the test were tested through pencil lead break experiments, and saltwater noise detection experiments were conducted to prevent noise interference from low-temperature saltwater flow and pipe wall friction in the identification of crucial signals for freezing pipe fracture. This study provides a basis for identifying the deformation mechanics and fracture warning of freezing pipes through dynamic analysis of AE monitoring information.

New insights into the impurity transport and separation behaviours during metal hydride dehydrogenation for ultra-pure hydrogen

The hydrogen separation and purification method based on metal hydride (MH) is viewed as one of the ideal methods for recycling industrial by-product hydrogen. Usually, self-produce hydrogen purging is conducted to remove the impurity. However, the mechanism of impurity transport and separation under the MH dehydrogenation process is still not clear so that the purity of produced hydrogen or the hydrogen recovery ratio is low. In this paper, a novel poisoning dehydrogenation kinetics considering the effect of passivation layer is proposed to accurately describe the dehydrogenation properties under the impurity poisoning conditions. The poisoning factor is introduced to describe the poisoning effect of impurities on MH materials. More active impurity or higher impurity concentration result in the larger poisoning factor. Based on the poisoning dehydrogenation kinetics, the MH dehydrogenation reaction model for self-produce hydrogen purging process is developed to describe the impurity transport and separation behaviours. The effects of operating parameters on the impurity transport and separation are further investigated for ultra-pure hydrogen. It is found that the low temperature and low outlet flow rate results in the low hydrogen loss for ultra-pure hydrogen. After the optimization, an efficient hydrogen separation and purification with both a hydrogen purity of 99.9999% and a hydrogen recovery ratio of more than 80% is achieved, which shows the potential in the hydrogen separation and purification of industrial by-product hydrogen.

A Universal Additive Design Strategy to Modulate Solvation Structure and Hydrogen Bond Network toward Highly Reversible Fe Anode for Low-Temperature All-Iron Flow Batteries.

Aqueous all-iron redox flow batteries (RFBs) are promising competitors for next-generation grid-scale energy storage applications. However, the high-performance operation of all-iron RFBs in a wider temperature range is greatly hindered by inferior iron plating/stripping reaction and low solid-liquid transition temperature at Fe anode. Herein, a universal electrolyte additive design strategy for all-iron RFBs is reported, which realizes a highly reversible and dendrite-free Fe anode at low temperatures. Quantum chemistry calculations first screen several organic molecules with oxygen-containing functional groups and identify N,N-Dimethylacetmide (DMAc) as a potential candidate with low cost, high solubility, and strong interactions with Fe2+ and H2 O. Combined experimental characterizations and theoretical calculations subsequently demonstrate that adding DMAc into the FeCl2 solution effectively reshapes the primary solvation shell of Fe2+ via the Fe2+ -O (DMAc) bond and breaks hydrogen-bonding network of water through intensified H-bond interaction between DMAc and H2 O, thereby affording the Fe anode with enhanced Fe/Fe2+ reversibility and lower freezing point. Consequently, the assembled all-iron RFB achieves an excellent combination of high power density (25mWcm-2 ), long charge-discharge cycling stability (95.59% capacity retention in 103h), and preeminent battery efficiency at -20°C (95% coulombic efficiency), which promise a future for wider temperature range operation of all-iron RFBs.

Evidence of a distal axis inactive high-temperature hydrothermal field on the ultraslow spreading Southwest Indian Ridge: Insights from mineralogy and geochemistry studies

The development of hydrothermal activities on mid-ocean ridges is primarily influenced by magmatic and tectonic activities close to the ridge axis. On slow and ultraslow spreading ridges featured by limited magma supply, prolonged hydrothermal activity can also occur in non-transform offsets (NTO), where sustained ultramafic-related hydrothermal circulation happens due to prolonged hydrothermal processes associated with the expose of ultramafic rocks. In contrast, basalt-hosted hydrothermal fields are barely developed in NTOs, especially in off-axis area, due to insufficient magma supply. In this study, we reported the occurrence of a distal axis (∼9.5 km) basalt-hosted hydrothermal field (50.63°E) on the NTO of segment 27 of the ultraslow spreading Southwest Indian ridge. The hydrothermal products are characterized by layered crusts mainly composed of oxides, such as limonite and goethite, rich in Fe and depleted in Si. These crusts contain high contents of trace elements derived from seawater, such as P, As, Mo, U, and Sb and show REE pattens with negative Eu and mostly positive Ce anomalies. However, the high Cu content (1.82 ± 0.89 wt%, N = 27), low absorption ratio of Cu (18.39 ± 12.71%, N = 9), and residual chalcopyrite altered by goethite suggest prior high-temperature hydrothermal activity. Lead isotopic composition with basaltic rocks signatures that distinct from those of low-temperature crusts of seawater origin also support this conclusion. The Fe-rich crusts appears to be the result of high-temperature sulfides altered by late-stage low-temperature diffuse flow. This field is currently the furthest known distal axis basalt-hosted hydrothermal field located in NTOs of ultraslow spreading ridges. The hydrothermal circulation is likely due to a combination of off-axis normal fault and gabbro diking. Our results emphasize the occurrence of distal axis basalt-hosted high-temperature hydrothermal activities on NTOs of ultraslow spreading ridges, and may lead to an increased estimation of hydrothermal heat and chemical influx to the ocean.

Effect of magnetic nanofluid on cooling of hot obstacles in a minichannel: Optimization of obstacle size and spacing

This study conducts a numerical simulation of laminar flow of water/alumina nanofluids (NFs) in a channel with 5 hot obstacles. Obstacles and the wall beneath them have a high temperature, and the top wall is insulated. Also, the beginning and end parts of the bottom wall are insulated. The low-temperature homogenous NFs flow increases in temperature after hitting the obstacles and leaves the channel of length 20. Under the obstacles and the hot wall, a downward magnetic field of constant strength is applied. By altering the height of obstacles (HOB) between 0.1 and 0.7, the width between 0.1 and 1, and spacing between 0.1 and 1, the streamlines, temperature, local Nu, and average Nusselt number (Nu) are examined in the channel. In addition, the response surface methodology is used to conduct an optimization to obtain the maximum Nu and maximum outlet NFs temperature (T-NFs) in the channel by changing the mentioned parameters in associated ranges. The control volume method and Simple algorithm are used for simulations. Results of this study indicated that increasing the obstacle spacing and height causes the local Nu on the bottom wall to increase, the T-NFs in the middle of channel to increase, and the Nu in the channel to decrease. The maximum Nu occurs for the minimum obstacle size and smallest obstacle spacing; in this case, the Nu is higher by 611% than that of the case with maximum obstacle size and largest obstacle spacing.

Photosynthetic responses of crustose coralline algae recruit from an upwelling area to light intensity, temperature and current flow rate in a mesocosm

The crustose coralline algae (CCA) play an important role building carbonate habitats and enhancing species diversity in rocky shores, rhodolith beds and coral-algal reefs. Though worldwide distributed some taxonomic groups were proved to show light and temperature boundaries. Nevertheless, little is known about the biological limits of CCA recruits and photosynthetic responses in a climate change environment. In this way, experimental studies are essential to identify their optimal conditions development. The aim of the study was to test ideal environmental conditions for CCA recruits from an upwelling area to verify Fv/Fm response patterns as an indicator of photosynthetic performance. Artificial disks were fixed on a rocky shore to provide substrate for CCA recruitments and then moved to be tested in a flow-through system. The CCA tested were species of the Genus Lithophyllum and experiments were performed with CCA exposed to different levels of light, temperature and current flow rates. The photosystem II function, measured by chlorophyll a fluorescence (Fv/Fm), was used as an indicator of potential photosynthetic electron transport. There was an interaction between light intensity, flow rate and temperature. Low light intensity, high temperature and fast flow rate (20 μmol m−2. s−1; 19 and 24 °C; 0.09 m s−1 respectively) provided optimal conditions for CCA recruits.

A comprehensive assessment for the structural change of waxy crude oils induced by pour point depressant beneficiation

In the petroleum industry, the solid paraffins that precipitate out from a waxy crude oil complicate the low-temperature flow characteristics, causing major difficulties in pipeline transportation. Pour point depressants (PPDs) are often utilized to improve the flow characteristics of crude oils by modifying the morphology and structure of wax crystals, becoming a great technical and economic interest. The improving mechanism of PPDs on the structure of gelled waxy crude oil can be attributed to the nucleation, co-crystallization, and adsorption effect to the precipitated wax crystals, preventing the waxy structure from growing further and forming a volume spanning network. Many previous works about the PPDs’ effect have merely focused on the pour point, apparent viscosity, and yield strength depressing ability, while other structural properties have rarely been comprehensively evaluated. The objective of this study is to comprehensively reveal the change of the wax particle structure in oils benefitted with PPDs. The structure of gelled oils doped with PPDs was found to become less elastic and more susceptible to shear perturbation with a lower linear deformation range of 0.42% and a longer relaxed time scale of 3000 s. Large amplitude oscillatory shear (LAOS) tests show that the nonlinear viscoelastic behaviors can be weakened by PPDs, whereas the third harmonic value obtained by Fourier-transform analysis increases after adding PPDs, indicating that the sensitivity to applied load are strengthened. Meanwhile, the value of yield strain increases to about 8.7%, and the irreversible plastic deformation zone becomes relatively broader (brittleness index I increases to 70.9), which mean a more ductile fracture induced by PPDs would occur when yielding. Although the additive PPDs weaken the structural strength and the non-Newtonian characteristics (kinetic index of n1 increases to 0.8), the characteristic of thixotropy is obviously strengthened, and the doped crude oils exhibit a faster structural breakdown process after yielding. All these novel changes for structural features explored in this paper provide theoretical guidance into understanding the practical engineering problems of accelerated process for the pipeline restart flow benefitted with PPDs.

Review of Slow Sand Filtration for Raw Water Treatment with Potential Application in Less-Developed Countries

Providing safe drinking water to people in developing countries is an urgent worldwide water problem and a main issue in the UN Sustainable Development Goals. One of the most efficient and cheapest methods to attain these goals is to promote the use of slow sand filters. This review shows that slow sand filters can efficiently provide safe drinking water to people living in rural communities not served by a central water supply. Probably, the most important aspect of SSF for developing and less-developed countries is its function as a biological filter. WASH problems mainly relate to the spread of viruses, bacteria, and parasites. The surface and shallow groundwater in developing countries around urban areas and settlements are often polluted by domestic wastewater containing these microbes and nutrients. Thus, SSF’s function is to treat raw water in the form of diluted wastewater where high temperature and access to nutrients probably mean a high growth rate of microbes and algae but probably also high predation and high efficiency of the SSF. However, factors that may adversely affect the removal of microbiological constituents are mainly low temperature, high and intermittent flow rates, reduced sand depth, filter immaturity, and various filter amendments. Further research is thus needed in these areas, specifically for developing countries.

Glycerol Monooleate (GMO): A Valuable Biobased Lubricity and Pour Point Enhancer Blend Component for the ULSD Fuel.

Novel value-added usage of glycerol (biodiesel coproduct) derivatives has been indispensable due to the extensive production of biodiesel. The physical properties of ultralow-sulfur diesel (ULSD) improved with the addition of technical-grade glycerol monooleate (TGGMO) with increasing concentration from 0.01 to 5 wt %. The influence of increasing concentration of TGGMO was studied on the acid value, cloud point, pour point, cold filter plugging point, kinematic viscosity, and lubricity of its blend with ULSD. The results showed improved lubricity for the blended ULSD with TGGMO as shown by the reduced wear scar diameter from 493 to 90 μm. The low-temperature flow properties were also improved as shown by lower pour points of -36 °C for the 1% TGGMO/ULSD blend compared to -25 °C for ULSDTGGMO blends in ULSD of up to 1 wt %, which met the ASTM standard D975 specifications. We also investigated the blending effect of the pure-grade monooleate (PGMO, purity level >99.98%) on the physical properties of ULSD at a blend concentration of 0.5 and 1.0%. Compared to PGMO, TGGMO significantly improved the physical properties of ULSD with increasing concentration from 0.01 to 1 wt %. Nevertheless, PGMO/TGGMO did not significantly affect the acid value, cloud point, or cold filter plugging point of ULSD. A comparison between TGGMO and PGMO showed that TGGMO improves the ULSD fuel lubricity and pour point more effectively than PGMO. PDSC data indicated that although addition of TGGMO will lower the oxidation stability slightly, it is still better than the addition of PGMO. Thermogravimetric analysis (TGA) data showed higher thermal stability and lesser volatility for TGGMO blends compared to those for PGMO blends. The cost effectiveness of TGGMO makes it a better ULSD fuel lubricity enhancer than PGMO.

Ignition and combustion of a group of waste-derived fuel slurry droplets: Mutual influence upon low-temperature convective heating

Waste-derived slurries can be burned both in a fluidized bed and when injected into a boiler furnace. This paper is the first to analyze the dynamic characteristics of ignition and combustion of a group of three slurry droplets based on coal slime, water, and waste industrial oil in a low-temperature air flow with a temperature of 500–600 °C and velocity of 0.1–1.2 m/s. The distance between the droplet centers varied from 3 to 15 mm. The results of the study can develop innovative technologies for flare and fluidized bed combustion of fuel slurries at the boiler start-up stage. It was found that a distance of 3–5 mm between droplet centers provides almost simultaneous gas-phase ignition of all droplets. A further increase in the distance critically worsened the ignition and combustion and eliminated the synergy. An increase in the air flow velocity contributed to the appearance of a common flame zone but at the same time increased the ignition delay of droplets by a factor of 1.2–1.6. The negative effects of cooling and entrainment of combustion products by a low-temperature flow can be effectively reduced by adding 5 wt% of industrial oil to the slurry. Also, the use of oil reduced the droplet ignition delay time by 15–20%. At the stages of flame and heterogeneous combustion, the differences for droplets in a group increased (the stage durations differed by 1.5–3 times). For the low-temperature start-up of a boiler, it was found advisable to provide a droplet flow with a sufficient density to stabilize their ignition without significant flow deviations (dimensionless distance 1.5–2.5).

Transformation of Condensed Matter into a Low-Temperature Plasma Flow for Problems of Plasma Mass Separation with a Potential Well

Transformation of Condensed Matter into a Low-Temperature Plasma Flow for Problems of Plasma Mass Separation with a Potential Well

PERFORMANCE OF SMALL SIZE AEROSPIKE. ENGINE

In this paper we are showing how aerospike nozzle can play an important role in rocket INDUSTRY as compare to other nozzles. We are using New rocket designs and increasing the performance of the current rockets But, the aerospike nozzle concept that has been under development since the 1950s is yet to be utilized on a launching. Due to its ability to adjust the environment by altering the outer jet boundary, the aerospike nozzle has better performance compared to present day others nozzle. An aerospike nozzle is designed for 20 bar pressure ratio to improve the performance of the aerospike nozzle for various conditions, some important design parameters and their performances were studied for low temperature flow conditions.

Introducing a Novel Rice Husk Combustion Technology for Maximizing Energy and Amorphous Silica Production Using a Prototype Hybrid Rice Husk Burner to Minimize Environmental Impacts and Health Risk

Rice husk is the main by-product of the postharvest stage in rice production, which causes environmental impacts due to improper management as a solid waste. However, potential economic applications of rice husk combustion have been identified for energy generation and amorphous silica production in several industries. To minimize hazardous gaseous emissions and crystalline silica availability, rice husk combustion conditions should be properly controlled which also effect for efficient heat production. This study was conducted under different conditions of temperature, airflow, combustion time, and bulk density of rice husk in the combustion process using an experimental prototype hybrid rice husk burner with a fluidized bed. The availability of crystalline silica in rice husk charcoal and the CO and O2 compositions in the exhaust gas were analyzed using XRD analysis and gas analysis, respectively. Furthermore, elemental and thermogravimetric analyses were conducted to find the most efficient combustion parameter for the optimum conditions of rice husk combustion using the experimental rice husk burner. Therefore, the most efficient heat generation was achieved with the observation of the lowest CO emission, the nonavailability of crystalline silica in rice husk charcoal, at a low temperature and air flow rate (430 °C; 0.8 ms−1), high bulk density (175 kgm−3 and 225 kgm−3) and short combustion time (30 s).

Numerical Simulations on the Performance of Two-Dimensional Serpentine Nozzle: Effect of Cone Mixer Angle and Aft-Deck

The current study addresses the effect of different designs of the exhaust mixer and aft-deck on the performance of a two-dimensional convergent nozzle represented by the internal and external flows and heat transfer process. The effect of different exhaust mixer cone angles of 10°, 15°, and 20°, and different aft-deck lengths of 140 mm, 280 mm, and 420 mm on the nozzle performance was investigated. To address the effect of an aft-deck, the flow behavior of a nozzle with an aft-deck was compared to that of a nozzle without an aft-deck. Then, the effect of different aft-deck lengths and different aft-decks with rectangular and trapezoid shapes was investigated. The results demonstrated that increasing the mixer cone angle resulted in decreasing the high-temperature core flow and increasing the low-temperature bypass flow. Increasing the mixer cone angle resulted in reducing the velocity inside the nozzle and at the exhausted jet, which can reduce the noise generated by the engine. Furthermore, increasing the mixer cone angle decreased the internal temperature of the nozzle and, along with the exhausted jet, decreased the infrared radiation. The results also illustrated that the presence of the aft-deck resulted in decreasing the pressure, temperature, and velocity inside the nozzle. The aft-deck also decreased the length and size of the potential core. The aft-deck length had no clear effect on the internal flow. However, increasing the aft-deck length resulted in a decrease in the exhaust gas temperature, which can decrease the infrared radiation. On another hand, using trapezoid and triangle aft-deck can enhance the performance of the nozzle by decreasing the velocity and temperature inside the nozzle and at the exhausted jet.

Creation of Fibrous Polymer Materials with Low-Temperature Flow Upon Pressure-Induced Phase Transition

Creation of Fibrous Polymer Materials with Low-Temperature Flow Upon Pressure-Induced Phase Transition

Operating Thermal Power Plants Efficiency Improvement under Current Conditions

In the present-day conditions, the issue of energy saving is becoming increasingly acute and permanently relevant. This situation is caused by rapid growth in prices for primary energy resources and by the need to reduce the share of natural gas in the incoming part of the energy balance of Belarus. According to available statistics, with the commissioning of the Belarusian NPP, the share of natural gas in the incoming part of the energy balance decreases from 97 to 59 %. In the economic complex, the share of this primary energy resource is projected at 70 %. The problem of energy saving is solved most rationally and with the least investment only by increasing the efficiency of natural gas use, especially due to the commissioning of the Belarusian NPP, the issue of preserving the possibility of using centralized heating facilities is acute. It is necessary to increase the thermodynamic efficiency of the cycles of steam turbine plants, both heating and condensing, which form the basis of the generation of the Belarusian power system, in order to restore the energy characteristics of the power system, which have somewhat decreased with the commissioning of the NPP. In the limit, the share of natural gas in the incoming part of the energy balance should be reduced to values not exceeding 50 %, in accordance with the requirements of energy security. The article considers examples of utilization of low-temperature secondary energy flows occurring at thermal power plants: the heat of the cooling processes of the generator, lubrication systems, as well as the heat of condensation of turbine exhaust steam and deeper cooling of flue gases. On the basis of this review, it is expected to identify promising areas of relevant research in relation to the energy system of Belarus.

Influencing Factors of a Cooling System Based on Low-Temperature Mine Water as a Direct Cooling Source

With the depletion of shallow metal mineral resources, deep mining has become more common. In the process of deep mining, heat hazards in mines seriously threaten the health of personnel and the safety of mining operations. According to the flow and low-temperature characteristics of abundant water in Maoping Lead Zinc Mine, this paper proposes the direct use of the low-temperature water inflow of the mine as the cold source by which to conduct the heat exchange with a single spiral-tube heat exchanger for mine cooling. An experimental platform was built for the cooling system to allow us to explore the mechanism of the influence of the inlet air volume and air temperature and the inlet water temperature and flow on the cooling effect of the single spiral-tube heat exchanger. It was found that with the increase in the inlet air volume and inlet water temperature, the cooling efficiency of the heat exchanger decreased, while with the increase in the inlet air temperature, the cooling efficiency of the heat exchanger increased. Within the experimental range, 127.2 m3/h was found to be the optimum inlet air volume, and 33.0 °C was the most appropriate inlet air temperature; the water temperature of Maoping Coal Mine is about 20 °C throughout the year, and the industrial test site can reduce the wind temperature of 31.5 °C to 23.9 °C. The inlet water flow is positively related to the cooling effect. With the increase in the water flow, the outlet temperature of the air flow at each working point was continuously reduced, and the cooling effect of the heat exchanger was improved. The moisture content of the inlet air flow can be reduced by increasing the low-temperature inlet water flow. Through experiments, the feasibility of the cooling system that directly uses the mine’s low-temperature water as the cold source was verified. A multiple linear regression analysis equation for the cooling system model is proposed, which provides a reference for formulating effective measures to prevent and control heat hazards in mines.

Effect of thermo-mechanical distribution on the evolution of IMCs layer and mechanical properties of 2219 aluminum alloy/304 stainless steel joints by inertia friction welding

The hybrid structure of 2219 aluminum alloy (Al alloy) and 304 stainless steel is effectively joined by inertia friction welding. There are the Cu-rich layer and the Fe4Al13 layer in the friction interface. The Cu-rich layer is discontinuous and its thickness is not uneven. While the Fe–Al layer is continuous and its thickness is closely related to the thermo-mechanical distribution at the interface. The thickness of the Fe–Al IMCs layer in the 1/2 radius zone is 6 fold of that in the center, while the center zone has unbonding defects due to low temperature and poor plastic flow of Al alloy. However, after changing the shape of the Al alloy end face, especially for the tapering surface joint, the homogeneous layer of Fe–Al IMCs forms in the center and 1/2 radius zones, which makes the tensile strength of different zones of the joint more balanced and improves the integral tensile strength. Meanwhile, the evolution of the two IMCs layers was investigated. It is found that the Cu-rich layer is formed through the precipitation of Al2Cu in the Al alloy. While the Fe–Al layer is formed through atomic interdiffusion and its growth is influenced not only by the thermo-mechanical coupling but also the precipitation of the Al2Cu phase.