Transfer Medium Research Articles

Temperature control of sulfonation reaction in a semi-batch reactor

ABSTRACT Due to the basic dynamic nature of a batch or semi-batch reactor, during operation, the control duty may be altogether a set point tracking problem rather than a regulatory task with a fixed set point. In addition to that in a large number of exothermic reactor control, usually the reaction mass has to be raised to a higher temperature for initiation, and after the reaction sets in large amount of heat has to be extracted, so that the control system have the capabilities to heat as well as to cool the reaction mixture (like LAB Sulfonation). This may be done by manipulating the ratio of hot and cold streams of heat transfer fluids to make a mixed stream to be used as the heat transfer medium by using two 2-way control valves, and heating and cooling loads are splitted between them. The choice of this reactor type has been made on the basis of that the target system of our study is Sulfonation of Linear Alkyl Benzene (LAB) to synthesize the product, Linear Alkyl Benzene Sulfonic Acid (LABSA) which is the active species for manufacturing of domestic or industrial detergents. The reaction is essentially carried in semi-batch jacketed reactor.

Enhanced heat transfer and thermal storage performance of molten K2CO3 by ZnO nanoparticles: A molecular dynamics study

Molten salt serves as a popular medium for thermal storage and transfer in concentrated solar power (CSP) systems. The existing experimental studies have found the capacity of enhancing the heat storage property of the molten carbonate by doping ZnO nanoparticles. However, it has been rarely reported to conduct simulations of ZnO/molten carbonate nanofluids, and the underlying mechanism of how ZnO nanoparticles enhance the heat transfer and storage capacity has less been explored. In this study, molecular dynamics (MD) simulation has been used to investigate the heat transfer and storage properties of a molten K2CO3 nanofluid containing ZnO nanoparticles. It was found that as the nanoparticle mass ratio in molten salt based nanofluids rises, their specific heat capacity initially increases but subsequently diminishes. The specific heat capacity peaks when the ZnO mass ratio is at 1 wt%, resulting in an increase of 17.83 % compared with the base salt. The thermal conductivity in nanofluids based on molten salt increases with the increasing of ZnO mass ratio. Multi-perspective analysis of the mechanism how ZnO nanoparticles enhance the thermal energy storage performance of molten salt, including the microstructural analysis, number density, vibrational density of state, and heat flow decomposition, is conducted. In addition, results of the number density illustrates that a compressed layer of K+ is formed surrounding the ZnO nanoparticles, and the change in the potential energy leads to an increasing heat capacity. Analysis of the heat flow decomposition suggests that the enhanced nonbonded interaction is the main reason for the improvement of thermal conductive performance in the nanofluids based on molten salt. The findings in the present study provide a new perspective of how ZnO nanoparticles enhance the thermophysical properties of molten salts.

Advanced strategies for conversing and fixing sulfur during waste resins oxidation through Ca/Zn oxides enhanced Na2CO3-K2CO3 system

The effective reduction of sulfur pollutant emissions during the treatment of waste resins has always posed a challenge. This study put forward a solution to using the metallic oxide enhanced Na2CO3-K2CO3 system for the treatment of waste resins (CERs). Na2CO3-K2CO3 was used as a medium for heat transfer and desulfurization, while CaO or ZnO functioned as catalysts in the sulfur conversion process. The thermodynamic analysis substantiated the reliability of enhanced sulfur fixation by CaO and ZnO. H2S, SO2 and COS primarily generated during the destruction stage of -SO3H (280–500°C) and residues (∼700°C), which were largely absorbed through a vapor-liquid-solid reaction to generate CaCO3, ZnS and K2SO4. CaO improved the conversion of sulfur to sulfate and effectively mitigated the excessive emissions of CO2. SO2 generated by the oxidation of ZnS at about 800 °C could be further absorbed by molten Na2CO3-K2CO3 to form K2SO4. The proposed method exhibited in-situ desulfurization capability and effectively inhibited the sulfur migration to gaseous products. At 800°C, the sulfur retention rate, the formation rate of SO42- and the oxidation efficiency of CERs reached 91.39 %, 80.61 % and 99.99 %, respectively. The existence of CaO and ZnO facilitated the inorganic transformation of organic sulfur, and the efficient conversion of organic sulfur into inorganic compounds was achieved. This approach provides a new opportunity to improve the treatment efficiency of radioactive solid waste containing organic sulfur.

Computational Modelling of Heat Transfer through Aluminium Metal Foams for LiFePO4 Battery Cooling

Abstract: Temperature is crucial for battery pack durability and power. Folded fin and serpentine channel cooling methods are mostly used to cool the pack. However, fluid absorption during cooling can reduce capacity and cause downstream temperatures to be higher than upstream. Consistent cooling is vital to prevent temperature variation and increase battery pack lifespan. This work is concerned with the computational study of heat dissipation from open-cell aluminium metal foam for cooling LiFePO4 battery packs. The battery module consists of six pieces of pouch cell and three pieces of the aluminium foam heat sink. In the present study, aluminium foams are positioned between the LiFePO4 battery modules that are arranged in a vertical manner. Thermal interaction between the battery module and aluminum foam was studied. The effect of pore density on heat dissipation performance at different mass flow rates was explored. It has been discovered that aluminium foam with suitable porosity and pore density can efficiently cool the LiFePO4 battery pack. This paper provides a theoretical framework for designing a thermal management system for lithium- ion batteries using aluminium foam. Background: Metal foam cooling is an established technique for thermal management of Lithiumion batteries in electric vehicles. Objective:: The present study aims to analyze heat transfer through aluminium metal foams for vertically aligned LiFePO4 battery pack cooling. Methods: The Darcy extended Forchheimer (DEF) model examines fluid flow through metallic foams, using the local thermal non-equilibrium model to determine heat transfer. Results: The impact of the density of pores in the aluminium foam on the average wall temperature and temperature difference along the battery surface is determined. The variation of heat transfer of lithium-ion battery modules for different mass flow rates is also studied. Conclusion: The results indicate that utilizing aluminium foam as a heat transfer medium for battery modules significantly enhances their thermal management performance.

Effect of microchannel cross-section geometry on the flow resistance with stainless steel flat-plate solar collectors

The stainless steel flat plate solar collector is a new type of collector that has a longer lifespan in high-temperature and high-humidity environments. When using stainless steel as the base material of the collector, the microchannel structure is typically employed to increase the heat transfer area and compensate for the lack of heat transfer coefficient of stainless steel. However, the shape of the channel section in microchannel structures affects the flow resistance of the heat transfer medium. This article presented the equation for the optimal feature size of the channel, obtained through fluid theory analysis of the stainless steel flat plate collector. The study analyzed the impact of different section parameters on the flow distribution and pressure drop characteristics of the medium in the channel through numerical simulation. The results showed that for a certain inlet flow rate, the cross-sectional geometry of the microchannel heat-absorbing plate determined the parameters such as the type of core cross-section, the degree of wall urgency, and the geometrical length of the microchannel, which in turn affected the distribution of the fluid in the flow channel and the energy loss. The optimal thermal performance of the stainless steel collector was observed when the width of the micro-channel was 8.7 mm and the corrugation height of the tube group was 3.00 mm.

Elevating Sustainability: The Role of Machining in Modern Eco-Friendly Manufacturing Processes

Sustainable manufacturing has become a critical concern across various industries, including aerospace, automotive, and services. It involves the creation of manufactured products through economically sound processes that minimize negative environmental impacts while conserving energy and natural resources. Additionally, sustainable manufacturing aims to enhance employee, community, and product safety.This paper focuses on the machining process as a key component of sustainable manufacturing. Machining is widely used in manufacturing industries to fabricate components, but it also significantly contributes to environmental pollution. Sustainable machining has been a topic of discussion for over a decade. In sustainable machining processes, every factor acts differently like, the tool life, productivity, and effective utilization of resources must be increased. In contrast, the machining cost, machine cutting power, and adverse effect of cooling and lubrication fluids will be decreased. Important aspects of sustainable machining include dry and near-dry machining, cryogenic machining, and minimum quantity lubricant (MQL) were presented in this article. The effectiveness of these processes is assessed based on cutting tool life and the quality of machined components. In addition, the advancements consideration such as novel process variations, process hybridization, the use of sustainable tools and green transfer mediums, and the optimization of process parameters. Recommendations include increasing efficiency and reducing waste by incorporating recyclable tools in the machine industry implementing either stand alone or hybrid sustainable lubrication machining techniques.

Experimental development of packing structures in a gas-particle trickle flow heat exchanger for application in concentrating solar tower systems

Ceramic particles represent a viable alternative as heat transfer and storage medium in concentrating solar tower systems. The particles are heated in solar-receivers close to 1000 °C. To utilize the stored energy in the particles, an air-particle direct-contact trickle-flow heat exchanger has been identified as suitable for this task. To date, no design recommendations exist that identify an optimized packing structure capable of providing a high particle volume fraction and a uniform spatial particle density distribution for a given grain type. Consequently, an experimental selection process is presented in this work to assess various packing structures for a given grain type in a trickle-flow reactor. The experiments were conducted with countercurrent flowing air at ambient conditions and 1 mm bauxite particles. A variety of packing structures were investigated at varying media flow rates. For each flow condition, the particle volume fraction was determined, as well as the particle distribution in a separate analysis. The cold experiments yielded a clear image of a preferred packing geometry, which will be discussed in detail. The results will serve as the basis for further hot experiments and thermal performance analysis in future work, where the packing geometry can be refined iteratively if necessary.

An Improved Method for Detecting Covert Channels in the Transport Layer

Steganography is one of the techniques used both to leak information and to prevent theft and distortion of confidential information. Covert channels in the network are one of the platforms for information steganography in the network. Often, this method is realized using the network's protocols. Network protocols are used as an information transfer medium. Network protocols can contain critical information and carry them into the network without attracting consideration. Covert channels are evaluated with three different criteria including capacity, robustness, and insensitivity. Also, the methods to deal with it include removing, limiting, and diagnosing the channel. By definition, covert channels are used to realize covert communication. Steganography methods are safe if the stego has no detectable signatures. Put differently, the stego statistical properties (audio, image, and video) should be similar to the cover properties. The ability to discover the message in the stego depends on the length of the hidden message. The proposed method in this study is to consider the amount of redundant information in a repository, explore the discoverable signs of the covert channel, and check the packet length in the checksum field in the UDP protocol at the transmission layer.

2D thermo-fluidynamic rotary model of an elastocaloric cooling device: The energy performances

Elastocaloric cooling has been considered a promising solid-state technology for cooling and heat pumping among the alternatives to vapor compression, at room temperature range. The technology is based on elastocaloric effect that is a thermophysical phenomenon occurring in materials like Shape Memory Alloys (SMA). The effect is detectable as a temperature change in the material if adiabatically subjected to a forcing field of mechanical nature. The latter provokes to the materials a stress that can derive from tension, compression, bending, torsion solicitations. As a result, the SMA experiments a structural phase change from austenite to martensite (coupled with heat addition) and temperature rise. Dually when the stress is removed, the SMA releases heat with a temperature decrease. In this paper the SUSSTAIN-EL rotary elastocaloric heat pump has been deeply investigated to test the energy performances while it works on open loop and closed loop, through a 2D numerical model based on the finite element method, for cooling and heating operation modes. The device employs a binary NiTi SMA as elastocaloric refrigerant and air as heat transfer medium. A wide set of working conditions has been considered like variable inlet mass flow rate, rotation frequency and thermal loads. The acquired results demonstrate that, both in open and closed loop, the prototype’s energy performances are promising and highly favourable for the intended macroscale collocation of the device.

Improvement of ablation resistance of C/C–SiC–ZrC composites by synergistic modification strategy with graphene and mullite

Synergistic modification strategy of graphene and mullite was used to introduce mullite and graphene into C/C–SiC–ZrC composites by chemical liquid-vapor deposition to improve ablation resistance. The ablation resistance and behaviors were comparatively studied under a heat flux of 2.38 MW/m2 for 100 s. Results showed that the appropriate content mullite modified C/C–SiC–ZrC composites has better ablation resistance due to the sufficient SiO2, Al2O3, and ZrSiO4 as healing agents and oxygen barrier and the synergistic effect with ZrO2 to form a denser and more stable oxide layer with the mass and linear ablation rates of 0.69 mg/s and −0.93 μm/s, respectively. The introduction of graphene improves the heat-force distribution, and as a high heat transfer medium and reinforcing phase, reduces the thermal concentration, cracking, and spalling of the oxide layer and further improves the ablation resistance, with mass ablation rate and linear ablation rate of −0.34 mg/s and −0.89 μm/s, respectively.

Mechanistic insights of efficient aromatic organic compounds oxidation using biochar derived from coking wastewater sludge

Coking wastewater sludge possessed potential environmental hazards and pyrolysis was a desirable approach which could converted it into one functional carbonous material. The sludge-based biochar (SC-N3) originated from the feedstock of sludge from the regenerated water treatment had various iron-containing species and exhibited the effective catalytic ability. Compared with the degradation of the four pollutants (i.e., phenol, pyridine, quinoline and indole) alone, the mixed of the four pollutants in simulated coking wastewater exhibited a prominent different degradation trend, where the removal rates of indole and quinoline were enhanced from 45% and 30% to 98.9% and 82.3%, respectively. The quinone intermediates from phenol degradation, played a critical role in enhancing the removal rates of indole and quinoline as the electron transfer medium. Both the free radical pathway dominated by •OH and non-radical pathway with 1O2 play the main role in indole degradation, while •OH was the main factor in the catalytic degradation of phenol, quinoline and pyridine. By analysis the intermediates elucidated by Fourier transform ion cyclotron resonance mass spectrometry and three-dimensional excitation-emission matrix fluorescence spectra, the degradation molecular characteristics and pathways of the four pollutants in simulated coking wastewater were deciphered. The findings indicated that the catalyst SC-N3 prepared from the coking wastewater sludge presented unique catalytic properties and possessed a promising application in the degradation of refractory wastewater.

Hydrodynamic characteristics of the microlayer under vapour bubbles on solid surfaces

This study investigates the hydrodynamic behaviour of the microlayer, a thin liquid film of a few micrometres thickness that forms beneath vapour bubbles during boiling under specific conditions. This microlayer serves as a rapid heat transfer medium through evaporation due to its low thermal resistance, making it a compelling subject for enhanced heat transfer research. We employ the geometric Volume-Of-Fluid (VOF) method for numerical simulations, allowing us to accurately replicate the growth of a vapour bubble on solid surfaces. The computational approach offers a level of detail and resolution that can compensate for certain aspects of microlayer behaviour absent in experimental methods. Our simulations reveal the complete spatial distribution of the microlayer and the profiles of the bubble interface near the meniscus front (the part of the interface near the solid). We compare the results with experimental data and conduct simulations with various bubble growth laws to explore how the microlayer responds to different growth scenarios. These findings lay the foundation for incorporating the microlayer’s contribution to overall boiling heat transfer in future models, potentially unlocking new avenues for enhanced heat transfer applications.

Stability, Thermophysical, Optical and Photothermal Properties of ZnO Nanofluids with Added Anionic/Cationic Mixed Surfactants

Metal oxide nanofluid is a new type of heat transfer medium with good thermal performance, which can be used to improve the heat collection and photothermal conversion performance of the collector. The development of new nanofluids with excellent stability, thermophysical and photothermal properties is very important for solar thermal utilization. In this paper, the ZnO nanofluids with SDS/CTAB mixed surfactants were prepared by two-step method. Their stability, thermophysical, optical and photothermal properties were studied based on experimental data. Then, the optimum concentration and preparation conditions of the proposed ZnO nanofluids adding SDS/CTAB with good photothermal performance were obtained. The results showed that the ZnO nanofluids with the addition of SDS/CTAB hybrid surfactant has good dispersion stability and its thermal conductivity can reach 0.772 W/(m·K). The transmittance was as low as 19.0.10% and the extinction coefficient was as high as 7.25 cm−1. In addition, the addition of the SDS/CTAB hybrid surfactant caused the ZnO nanofluids to exhibit better photothermal conversion efficiency up to 87%, which was superior to that of the control group with the addition of other surfactants. Therefore, ZnO nanofluids with the addition of SDS/CTAB have great potential as DASC working fluids.

Numerical simulation of a thermal energy storage system using sunrise and sunset transient temperature models

The temperature of the sun was modeled in this study using two transient solar temperature equations for sunrise and sunset that were developed for designing a latent heat thermal energy storage (LHTES) system for a concentrated solar power (CSP) plant. The derivation of the equations was based on the existing solar hour angle and the fundamental periodic function equations. Ansys' computational fluid dynamics code was used to investigate numerically the transient response of the conjugate melting and solidification of a phase change material (PCM) in a cylindrical shell and helical heat pipe (HHP) thermal system. The models for both equations were applied as user-defined functions (UDFs). The heat transfer medium was air. The predicted liquid and solid fractions provide quantitative data on the temperature and the stored solar energy. The effectiveness of both models in enhancing heat transfer and their suitability as real-time transient solar temperature models in heat transfer engineering is demonstrated by comparisons between their outputs. With high agreement, experimental data from the open literature was used to validate the numerical model's predictions. The solar temperature models aim to contribute to heat transfer enhancement for a reduced PCM energy storage time in designing a high-temperature solar thermal storage that is adequate to maintain a steady supply of electricity and energy for domestic and commercial applications and to accelerate the global transition to low-carbon energy.

A Survey of the Mechanisms Impairing Optical fiber communications performance

The growth of information technology and Internet networks, combined with nearly daily use and many subscribers, has caused the volume of data stored in communication systems to balloon to enormous proportions. Optical fiber cable is the medium for data transfer because it has a bandwidth far more significant than other transmission methods and can span significantly greater distances. The transmission of information from one location to another can be accomplished via a technique known as fiber-optic communication. This involves passing pulses of light over an optical fiber. Optical fiber performance is affected by many effects, including attenuation, dispersion, scattering, and bending. It is feasible to enhance the performance of optical fibers for communications by utilizing carbon nanotubes and multiple coding technologies. This can be accomplished via integrated optical circuits or by making the cable more advanced and developing it further. Photosynthesis is accomplished by utilizing carbon tubes and the optical property inside them.

Geothermal In-Situ Heat Transfer Control Factor Simulation and Numerical Analysis

Geothermal energy, as a renewable and clean energy source, holds immense potential in meeting energy demands and reducing carbon emissions. Its unique sustainability and environmental friendliness make it an important complement to addressing today's energy challenges. Coaxial tubing in-situ heat exchange technology for geothermal wells, as a key extraction method for geothermal energy, is subject to control by multiple critical factors that directly relate to its efficiency and feasibility. This paper aims to delve into the technology of coaxial tubing in-situ heat exchange for geothermal wells through numerical simulation analysis, with a focus on studying the impacts of three key factors on its performance: heat transfer medium flow rate, inlet water temperature, and cement thermal conductivity. Through numerical analysis, this study aims to reveal the variations of these factors to provide more refined control methods and optimize the coaxial tubing in-situ heat exchange technology for geothermal wells. By conducting experimental simulations and numerical analysis on these key factors, this paper aims to provide strong support for optimizing the coaxial tubing in-situ heat exchange technology for geothermal wells, which will contribute to advancing geothermal energy technology and promoting the sustainable utilization of clean energy.

Optimizing Plate Heat Exchanger Design for Steam Condensate Recovery Systems

Condensate water is typically generated as a by-product during the use of steam as a medium for heat transfer. In order to optimize the transfer area, the chemical industry often employs heat exchangers, such as the plate heat exchanger (PHE), which provides flexibility in adjusting the space area for heat transfer. This case study examines the optimization of plate geometry dimensions to enhance the heat transfer process of PHE equipment design. The optimization process involves mathematical equations and a literature review of the design of this type of heat exchanger. Improving the dimensional aspect of the plate geometry results in an increase in the overall heat transfer coefficient (U) and a reduction in the number of design requirements used. The study's estimation results suggest that the PHE design has a limitation on plate dimensions, which should be less than 0.3×0.6 m. Additionally, it is important to consider the pressure drop value, which should not exceed 29.07 kPa. A review of the chemical industry field provided estimated options for plate size and quantity, both of which support the optimization of heat transfer rate and design constraint thresholds. The implementation of the design has been found to enhance the performance of the planning process for recovering steam condensate water.

Ag nanofilm enhanced S-type Ag@AgCl/tubular g-C3N4/Ti photoanode visible light response photocatalytic fuel cell

In this study, based on Ag@AgCl/tubular g-C3N4 (Ag@AgCl/TCN) composite, Ag nanoparticles were deposited on its surface to form Ag nanofilm enhanced composite through photoreduction of excessive silver nitrate solution to obtain Ag nanofilm Ag@AgCl/TCN photocatalyst. Finally, Ag nanofilm Ag@AgCl/TCN/Ti photoanode was successfully prepared by silica-sol drop-coating method, and assembled with Cu2O/Cu cathode to construct a photocatalytic fuel cell (PFC). Ag nanofilm can not only enhance the light absorption and utilization of Ag@AgCl/TCN/Ti, but also extend its light response wavelength to visible light, and be used as an electron transfer medium to reduce internal resistance. The photocurrent density and the photoconversion efficiency of the Ag nanofilm/Ag@AgCl/TCN/Ti are 8.01 mA·cm−2 and 1.24%, respectively, which are 2.49 and 2.54 times those of the Ag@AgCl/TCN/Ti photoanode, respectively. The first-order kinetic constant and the maximum power density of the Ag nanofilm-coated Ag@AgCl/TCN/Ti-Cu2O/Cu PFC system are 0.064 min−1 and 46.37 μW·cm−2, respectively, which are 1.39 and 1.94 times those of the Ag@AgCl/TCN-Cu2O/Cu PFC system, respectively. In addition, it degraded more than 95% of rhodamine B, 72.68% of tetracycline and 54.25% of bisphenol A within 60 min. The excellent performance of Ag nanofilm/Ag@AgCl/TCN/Ti-Cu2O/Cu is due to the strengthening of Ag nanofilm and the formation of S-type heterojunctions between AgCl and TCN. Free radicals (•Cl, h+, •OH, •O2-) and non-radicals (1O2) are involved in the degradation reaction of RhB degradation. It is worth noting that 6% Ag nanofilm/Ag@AgCl/TCN/Ti-Cu2O/Cu has a positive effect on the production of •O2-, and its output is approximately 1.89 times that of the Ag@AgCl/TCN/Ti-Cu2O/Cu. A series of material characterization experiments have been completed and possible mechanisms of operation have been proposed. This study provides a new scheme for the design and preparation of high-efficiency photoanode of PFC.

FEEDWATER TREATMENT AT THERMAL POWER PLANT

As a rule, water is used as the working fluid of thermal power equipment, which undergoes a series of phase transformations in steam cycles. Water is useful for its properties and as a result gained such wide popularity. It is important to consider that water is the most accessible, widespread and environmentally friendly substance on Earth. Water has low viscosity, high density, good heat transfer coefficient, low cost, and water does not require disposal. In addition to these properties, water also has a high heat capacity, which makes it an efficient heat transfer medium. This means that it is able to absorb and transfer large amounts of heat without a significant change in temperature. This is especially important in heat transfer systems where heat transfer efficiency plays a key role. It worth noting that water is responsive to temperature regulating. Natural water also has disadvantages, such as the possibility of corrosion processes with the formation of metal oxides (rust) and thus destruction of equipment surfaces, limescale formation on heating surfaces when heated to temperatures above 80 degrees Celsius. Therefore, it is necessary to carry out appropriate physical and chemical treatment of water to ensure all the requirements that applied to the water coolant. Certain quality indicators, processing methods and schemes, as well as equipment protection methods have been established for water. The article presents data on determining the dependence of a number of indicators of water quality taken from the water of the Irtysh River for use at Semey CHPP-1.

Demonstration by laboratory experiments of thermosiphon effect in the closed loop carbon dioxide circulation system

The thermosiphon effect has been shown theoretically to exist in the closed loop CO2 circulation geothermal power generation systems. We verified this effect based on previous numerical studies that determined the conditions under which the thermosiphon effect can be established and we developed laboratory experimental apparatus with conditions analogous to those in the previous studies. The results of laboratory closed loop CO2 circulation experiments using this apparatus demonstrated the thermosiphon effect at initial injection pressures from 8.5 to 18 MPa and heater temperatures from 80 to 200 °C. With this experimental apparatus, higher heater temperatures produced higher heat output at the same injection pressures, and that the peak heat output was observed at injection pressures of 12–14 MPa. Furthermore, comparing CO2 with water as the thermal transfer medium indicated that the feasibility of the thermosiphon effect was increased by changing the medium from water to CO2.