Constant Temperature Conditions Research Articles

Research on Ozone-Enhanced Oxidation of Industrial Zinc Sulfite from Flue Gas Desulfurization

ABSTRACT This study investigates the air oxidation and ozone-enhanced oxidation of zinc sulfite. Zinc sulfite was prepared by reacting pure or industrial zinc oxide with SO2 in water. The oxidation experiments were conducted under constant temperature conditions, with slurry, oxygen, and ozone concentrations in the ranges of 0.5–4%, 10–60%, and 1100–1920 ppm, respectively. The experiments involved determining the zinc ion concentration, sulfite concentration, dissolved oxygen, ozone concentration in the exhaust gas, and total organic carbon value for analysis of the oxidation process. The findings revealed that the mass transfer rate of O2 and/or O3 determined the reaction rate in the main stage of the oxidation process, while ozone affected the non-mass transfer control stage, resulting in an average enhancement of 15% in the oxidation rate. Furthermore, ozone causes organic matter attached to industrial zinc sulfite particles to fall off into the solution, significantly improving the oxidation ratio of industrial zinc sulfite.

Research on the enhancement material and culture method of soil aggregates composed of feldspathic sandstone and sand

The Mu Us Sandy Land is a region characterized by wind-blown sand and soil erosion in northern China. To enhance the soil quality of this area, various organic materials were incorporated into the mixed soil at a volume ratio of 1:2 for feldspathic sandstone to sand. Culture was conducted in the field and under constant temperature conditions in laboratory culture chambers. Four treatments were established in the experiment, each calculated based on weight ratio and controlled (with no organic material added, CK); single application of straw (5% straw, P1); single application of biochar (5% biochar, P2); combined application of biochar and straw (5% biochar + 5% straw, P3). After 90 days of culture, soil samples were collected for analysis of various indicators such as soil aggregate particle size distribution, water stability of soil aggregates, mean weight diameter, mean geometric diameter, and fractal dimension using dry sieving and wet sieving methods. The objective is to establish a scientific basis and provide technical support for addressing the challenges associated with compound soil and implementing rational fertilization measures. The research results indicate that: (1) The quantity of aggregates > 0.25 mm under different treatments follows the order CK < P1 < P2 < P3, and the differences between treatments are significant (P < 0.05); (2) Soil water stability, mean weight diameter (MWD), mean geometric diameter (GMD), and fractal dimension of soil aggregates in compound soil with different organic material additions are superior to the control, and the effect of biochar on improving soil aggregates is better than that of corn straw. The combined application of both significantly improves the effect compared to single applications. In both culture modes, under wet sieving, the P3 treatment shows the highest MWD and GMD of soil aggregates, with an increase ranging from 3.45% to 85% and 4.55% to 38.46%, respectively, compared to other treatments. (3) The trend of fractal dimension among treatments is consistent: P3 < P2 < P1 < CK, and the differences between treatments are significant (P < 0.05). Moreover, there is a good negative correlation linear equation relationship between the fractal dimension (y) and WR > 0.25 (x) of compound soil, with a correlation coefficient of up to 0.9851. In conclusion, the incorporation of organic materials can effectively enhance the proportion of macroaggregates in compound soil consisting of Feldspathic sandstone and sand, thereby improving soil stability and erosion resistance. The optimal outcome is achieved through the combined application of biochar and straw. Indoor culture proves to be more effective than field culture, while wet sieving accurately reflects the structural characteristics of compound soil under both dry and wet sieving treatments.

Roles of soil minerals in the degradation of chlorpyrifos and its intermediate by microwave activated peroxymonosulfate

Soil mineral is one of the important factors that affecting oxidant decomposition and pollutants degradation in soil remediation. In this study, the effects of iron minerals, manganese minerals and clay minerals on the degradation of chlorpyrifos (CPF) and its intermediate product 3,5,6-trichloro-2-pyridinol (TCP) by microwave (MW) activated peroxymonosulfate (PMS) were investigated. As a result, the addition of minerals had slight inhibitory effect on the degradation efficiency of CPF by MW/PMS, but the degradation efficiency of TCP was improved by the addition of some specific minerals, including ferrihydrite, birnessite, and random symbiotic mineral of pyrolusite and ramsdellite (Pyr-Ram). The stronger MW absorption ability of minerals is beneficial for PMS decomposition, but the MW absorption ability of minerals cannot be fully utilized because of the weaker MW radiation intensity under constant temperature conditions. Through electron spin resonance test, quenching experiment and electrochemical experiment, electron transfer, SO4− and OH, SO4− dominated TCP degradation by MW/PMS with the addition of birnessite, Pyr-Ram and ferrihydrite, respectively. Besides, the adsorption effect of ferrihydrite also enhanced the removal of TCP. The redox of Mn (III)/Mn (IV) or Fe (II)/Fe (III) in manganese/iron minerals participated in the generation of reactive species. In addition, the addition of minerals not only increased the variety of alkyl hydroxylation products of CPF, causing different degradation pathways from CPF to TCP, but also further degraded TCP to dechlorination or hydroxylation products. This study demonstrated the synergistic effect of minerals and MW for PMS activation, provided new insights for the effects of soil properties on soil remediation by MW activated PMS technology.

Performance analysis and optimization of the gyroid-type triply periodic minimal surface heat sink incorporated with fin structures

The Triply Periodic Minimal Surface (TPMS) structures demonstrate substantial value and development potential in applications and research concerning heat sinks and heat exchangers. To further enhance the convective heat transfer performance of TPMS, this study proposes a novel method of incorporating fin structures into TPMS. This method is applicable to various types of TPMS, and the new structure constructed using this method is termed “TPMS with Fin Structures (TFS).” Subsequently, a TFS-Gyroid heat sink based on the Gyroid-type TPMS was constructed. This study presents a calculation method for the fin height in TFS-Gyroid (HTFS-Gyroid). Numerical simulation methods were employed to investigate the influence and mechanism of HTFS-Gyroid on the convective heat transfer performance and flow resistance of the TFS-Gyroid heat sink model, with air as the working fluid and under constant wall temperature (100 °C) conditions. The results indicate that within the flow range of 24–120 L/min, as HTFS-Gyroid increases from 0 to 1.6 mm, the average surface convective heat transfer coefficient (h̅) of the TFS-Gyroid heat sink model increases by 27.4 %-34.6 %, and the inlet–outlet pressure drop (ΔP) increases by 42.5–632.8 Pa. As HTFS-Gyroid increases, the PEC of the TFS-Gyroid heat sink model gradually decreases, whereas j/f gradually increases. The primary mechanisms by which the fin structures enhance the convective heat transfer performance of the TFS-Gyroid heat sink are: 1) increased heat exchange area, 2) the fin structures induce a large number of longitudinal vortices and secondary flows within the flow channels, and 3) the formation of “Fins Occupying the Perforated Structure (FOPS)” within the flow channels.

Flow and Heat Transfer Characteristics in the Entry and Stabilized Flow Regions of a Circular Channel Rotating About a Parallel Axis

Abstract Cooling of heavy-duty electrical machines such as generators and motors is crucial for the smooth operations without thermal runaway. A commonly employed technique for the cooling of rotors in these machines is to place channels at different radial locations for the continuous passage of coolant. These channels are therefore rotating about a parallel axis, and the rotation-induced forces alter the flow and thermal behavior of the coolant compared to stationary channels. The present study reports a detailed numerical investigation on a long circular channel rotating about a parallel axis. The objective is to analyze the flow, heat transfer, and rotation-induced forces (Coriolis and centrifugal forces) in the entry region as well as in the region where flow is stable (the term ‘stable’ is used rather than ‘developed’ due to the presence of secondary flows in this region). The rotating channel was subjected to constant wall heat flux and constant wall temperature conditions at different Rotation numbers of 0, 0.15, 0.4, and 0.6. The Coriolis force is observed to be strong enough in the entry region to influence the flow. In the “stable flow” region, the centrifugal force becomes more dominant and forms counter-rotating secondary vortex pair, which causes circumferential variation in the Nusselt number. The flow and heat transfer characteristics for constant wall heat flux and wall temperature boundaries are the same for rotation conditions with similar values of rotational Grashof number. A correlation is presented for the circumferential variation of the Nusselt number in the stable flow region.

On the Chemical Effect of Steam Addition to Premixed Hydrogen Flames with Respect to $$\text {NO}_\text {x}$$ Emissions and Flame Speed

AbstractThe present work analyses the effect of water vapour addition on $${\text {NO}_\text {x}}$$ NO x emissions of premixed hydrogen flames. In doing so, the adiabatic flame temperature is maintained by increasing the equivalence ratio, or alternatively increasing the unburned gas temperature, for increasing levels of water loading. Thus, it is possible to elucidate the changes in $${\text {NO}_\text {x}}$$ NO x production at constant-temperature conditions when the mixture is diluted with water. A consistent reduction of $${\text {NO}_\text {x}}$$ NO x emissions for increasing water dilution can be observed from 1-D premixed freely propagating flame simulations. Regarding the chemical kinetics effect of water vapour, the relative importance of different third-body reactions is examined by modifying the corresponding water collision efficiencies individually. For the chemical mechanism adopted, three reactions directly affect the nitrogen chemistry and the remaining relevant reactions are important for the flame structure and radicals concentration. The analysis stresses the importance of indirect effects like the formation and consumption of $$\text {O}$$ O and $$\text {H}$$ H radicals in the pre-heat zone, which enhance the subsequent formation of $${\text {NO}_\text {x}}$$ NO x within the flame. The presence of steam can lead to a reduction of approximately $$50\%$$ 50 % in $${\text {NO}_\text {x}}$$ NO x emissions under conditions close to stoichiometry and high water loading ($$10\%$$ 10 % by mass), compared to scenarios without water addition. Furthermore, the efficiency of water in third-body reactions significantly contributes to an emission reduction, and half of $$\text {NO}$$ NO emissions under the same water loading conditions at high equivalence ratio are observed when the third-body reaction efficiency is activated with respect to the case with zero efficiency. This reduction is primarily attributed to effects on radical concentrations. Finally, the chemical effect via the third-body efficiency of water is examined with respect to flame speed. It turns out that the adiabatic flame temperature plays a key role for the relative influence of the chemical kinetics effect of water dilution. A cross-over temperature is found, below which the chemical effect of water reduces the flame speed, whereas the flame speed is increased above it.

Evaluating the impact of indoor aerosols on the performance of real-time radon sensors

Radon, a naturally occurring radioactive gas, poses a significant health risk by accumulating in buildings and potentially leading to lung cancer. Depending on building construction and geographical location, radon levels can vary substantially both within individual buildings and between different buildings. While previous studies have primarily focused on the impact of temperature and relative humidity on radon devices, the influence of aerosols remains largely unexplored. This paper presents a comprehensive evaluation of the influence of indoor aerosol sources on the performance of real-time radon sensors, encompassing consumer, medium, and research-grade devices. Measurements were performed at relatively low (300 Bq/m3) and high (2′000–3′000 Bq/m3) radon levels in a controlled environment—a stable atomic shelter with constant temperature and humidity conditions. Six different aerosols sources were introduced to produce aerosols of different sizes and concentrations. The results suggest that the tested indoor aerosols did not significantly influence the performance of radon devices, irrespective of their grade or detection method. Consequently, sensor performance and the radon levels being investigated may exert a more significant influence on the obtained results than aerosol levels alone. This paper provides valuable insights into the influence of indoor environment on the performance of radon measuring devices, underscoring the importance of understanding their utility and application scope for researchers, professionals, and the general public alike.

Proteomic profiling of Botryllus schlosseri, an emerging model organism

Botryllus schlosseri is a colonial chordate species that exhibits robust stem cell-mediated regeneration capacities throughout life. It grows through a process of colonial budding known as blastogenesis, in addition to its sexual reproduction mode, embryogenesis. In natural conditions, colony growth peaks in the summer and drastically decreases in the winter due to various seasonal factors. We have established and optimized a method to rear B. schlosseri animals in landlocked laboratories where the controlled conditions allow colonies to grow continuously and exponentially through asexual reproduction under constant temperature, salinity, light, and nutrient conditions. During the weekly blastogenic cycle, all asexually derived parental zooids synchronously regress within one day and are replaced by a new generation. To enable comprehensive molecular phenotyping of this species we established a quantitative proteomics workflow and spectral library for Liquid chromatography/Tandem mass spectrometry (LCMS) data-independent acquisition (DIA). In this study, we quantified the relative abundances of several thousand proteins representing molecular phenotypes of B. schlosseri. This workflow enables us to use proteomics to characterize zooid development during its regenerative cycle, including the short critical period of the takeover stage, during which degenerating zooids undergo massive apoptosis while succeeding buds quickly mature and migrate into place. From this data, protein networks associated with regeneration and degeneration can be created, offering insights into tissue developmental pathways in vivo and future cell immortalization strategies in vitro. Furthermore, the establishment of quantitative proteomics workflows for B. schlosseri coupled with its unique life cycle features promotes the use of this model organism for the study of phenotypic plasticity and evolution of aging, stem cells, and mechanisms of regeneration and cell differentiation. This project is funded by NSF Grant MCB — 2127516. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Heat transfer inside a horizontal circular enclosure with a heated semi-circular cylinder at different orientations

Natural convection inside a cylindrical enclosure is important in many industrial applications. Laminar natural convective heat transfer in the annular space between heated semi-circular cylinder in a horizontal concentric cylindrical enclosure, which has relevance to cooling of electronic components, is studied in this work. Constant wall temperature (CWT) and constant wall heat flux (CWHF) boundary conditions are considered on the inner cylinder, whereas the outer cylindrical enclosure is maintained at a fixed lower temperature. The Finite Volume Method (FVM) is used for the computations. The effect of the Rayleigh number ( Ra = 10 2 to 10 5 ) and the angular orientation of the semi-circular cylinder on the convective heat transfer is investigated. The fluid flow, temperature profile, and heat flow are visualized via streamlines, isotherms, and heatlines. Further, the overall heat transfer is explained based on the local and average Nusselt number on the inner cylinder wall. The effect of the angular orientation of the inner cylinder is noticeable for Ra ≥ 10 3 . The angular orientation ϕ = 90 ° greatly enhances the heat transfer as compared to all other orientations for all Ra ≥ 10 3 for both CWT and CWHF boundary conditions. The correlation between the average Nusselt and Rayleigh numbers for a particular orientation is proposed.

Development of coffee bean porosity and thermophysical properties during roasting

The development of coffee bean porosity during roasting was captured for a Kenyan Arabica coffee roasted under different constant inlet air temperature conditions in a pilot-scale spouted bed roaster. Coffee bean porosity was characterised using X-ray Micro Computed Tomography (Micro-CT). These data demonstrated a significant increase in coffee bean porosity of up to 60% during roasting. The coffee's intrinsic physical properties were also analysed to identify the relationship between porosity, thermophysical properties (density, thermal conductivity, specific heat capacity) and common process indicators (colour, mass, moisture, volume). Implications for heat transfer during roasting are also discussed. As Micro-CT, pycnometry and thermal properties analysers are not readily available tools, correlation of costly analytical methods with rapid discriminative tests are presented, allowing developers to utilise more accessible characterisation techniques to inform modulation of their processes and products. The data-driven approach to map coffee's physicochemical development during roasting provides comprehensive data that could be used to calibrate mechanistic or kinetic models. These physics-driven models could then be used as routine equations nested in heat and mass transfer simulations for developers to predict coffee's thermal evolution and subsequent physical transformation during roasting.

Effect of temperature and salt concentration of pore fluid on the behaviour of an expansive soil during drying and wetting cycles

ABSTRACT A study was conducted on the effects of temperature and salt concentration of pore fluid on the properties of an expansive soil during drying and wetting cycles. The experimental tests were performed on modified and conventional odometers at constant and variable temperatures under 10 kPa surcharge pressure. Distilled water and solutions of sodium chloride and calcium chloride with concentration of 250 g/litre were used for making samples and distilled water was used for inundating samples during the wetting stage. The results showed that the swelling potential is decreased with increasing the number of cycles for both constant and variable temperature conditions. It was revealed that the potential of swelling is a function of salt concentration of pore fluid of the sample and the effect of temperature on the potential of shrinkage and swelling is negligible. The variation of void ratio with water content is dependent on the salt concentration of pore fluid and the position of void ratio-water content curve is a function of temperature. The results of scanning electron microscopy (SEM) tests showed that the structure of soil is changed during drying and wetting cycles which results in the reduction of potential of shrinkage and swelling.

Numerical investigation of fluid flow and heat transfer characteristics of MWCNT-Al 2 O 3/H 2 O hybrid nanofluid flowing through a novel semi-arc ribbed square duct

This study carried CFD analysis to study the fluid flow and heat transfer characteristics of MWCNT- Al 2 O 3 / H 2 O hybrid nanofluid flowing through square duct equipped with novel semi-arc ribs. The turbulent flow simulations are performed at varying Reynolds numbers ( Re ) between 3,000 and 18,000 and nanoparticle volume concentration ( φ ) range of 1–4% for different rib parameters, namely relative stream pitch ratio ( X pr ) range from 2.67 to 3.67, Rib height ratio ( R hr ) range from 0.05 to 0.20, number of ribs ( n ) range from 1 to 4. Different performance indicators, such as Nusselt number ( Nu ), friction factor ( f r ) , and thermal hydraulic performance (THP) was examined to evaluate the system performance. The RNG k ‐ ε model was engaged to simulate turbulent nanofluid flow within the channel under constant temperature condition (T = 300 K). The findings indicated that the development of vortex flow and increased turbulence due to the effects of arcs can improve the heat transfer enhancement. The THP, Nu and f r were found to be highest for R hr = 0.15 , X pr = 3.34 , φ = 4 % , and n = 3 , yields to the best THP at 1.94.

Numerical investigation on the impact of circumferentially varying temperature on the buoyancy and heat transfer characteristics of supercritical CO2 natural circulation loop

The non-uniform heating in the supercritical natural circulation loop (SCNCL) and its associated heat transfer behaviour and buoyancy variation are not well understood. Since buoyancy is the primary force that drives fluid motion in the SCNCL, any factor affecting buoyancy will have an impact on overall performance. The present study investigated the circumferentially varying temperature (CVT) at the source, compared it to constant uniform temperature conditions, and examined the associated variation in buoyancy, and heat transfer characteristics. This study establishes a numerical model for a three-dimensional circular cross-section rectangular SCNCL. The SCNCL was examined at different pressures ranging from 8 MPa to 12 MPa, with 1 MPa pressure increments, to cover a wide range of applications. The results indicated that at 12 MPa pressure, the heat transfer rate and heat transfer coefficient decreased by a maximum of 14 % and 50 %, respectively, compared to that of constant uniform temperature. In contrast, the mass flow rate shows minimal variation between the CVT and a constant temperature condition. The fluid density increases significantly at higher pressure, resulting in decreased buoyancy generation in the loop. Therefore, for all cases, velocity increases up to 10 MPa and then begins to decrease. Thus, the peak velocity was observed at 10 MPa pressure. The CVT negatively impacts both horizontal and vertical heater configurations, leading to a reduction in overall performance. Additionally, non-uniform heating has a greater impact on the horizontal heater configuration compared to the vertical heater configuration.

Experimental re-melting of a continental crust: probing the deep storage zone of Campi Flegrei and Vesuvius magmas

Mantle magmas interact with surrounding rocks during their ascent and storage in the continental crust, leading to open system processes as wall rock partial melting. In this study, we have experimentally investigated the reactions between a leucosome depleted migmatite and a primitive K-basaltic of Campi Flegrei (Italy). Experiments were carried out at pressure of 0.8 GPa temperatures from 1250 °C to 1050 °C and constant temperature and thermal gradient conditions. The experimental products consist of biotite-free migmatite, glass and crystals of clinopyroxene, olivine, plagioclase and Cr-spinel with proportions that vary as a function of temperature. Open system isothermal experiments indicate that the chemistry of melts and phase relationships are controlled by the high Al2O3 content of leucosome depleted migmatite with the glass composition shifting from K-trachybasalt towards shoshonite as the temperature decreases from 1200 °C to 1125 °C. At temperatures \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\le$$\\end{document}1150°C, migmatite assimilation is not exclusively due to the assimilation fractional crystallization process because evidence of mingling and mixing is observed. T-gradient experiment shows melt composition ranging from shoshonite to phono-tephrite moving from the slightly crystalline zone (T = 1250 –1210 °C) at the bottom of the capsule towards the highly crystalline zone (T = 1160 –1140 °C). This SiO2-constant trend indicates that at temperature below the basalt solidus, the assimilation of leucosome depleted crust is represented almost exclusively by the biotite breakdown, leading to the increase in Al, Mg, Fe, Ti, and K activities in the system. The shoshonitic composition obtained in our experiments could represent the parental magma for both Campi Flegrei volcanic district and Vesuvius magmatic systems, indicating modification in a deep storage zone through mixing with the partial melts derived from restitic continental crust.

Effects of vibrational flow on nanofluid flow behavior under different temperature boundary conditions

A comparative study was conducted using a well-validated computational fluid dynamics (CFD) model to investigate the effects on heat transfer. The study focused on forced convection internal flow of both base fluid and nanofluid, subjecting them to different boundary conditions. Vibration was applied in the transverse direction to the flow. The simulations were performed with varying Reynolds numbers, volume fractions, vibration frequencies, and amplitudes. In order to improve the predictive capabilities of the computational fluid dynamics (CFD) model for single-phase flow systems, rheological properties dependent on temperature were incorporated. The introduction of transverse vibrations swiftly disrupted the thermal boundary layer, resulting in an axial temperature increase for low Reynolds number flows. Consequently, under constant wall temperature conditions, this led to heightened heat transfer rates. The observed enhancement in heat transfer rate, achieved through variations in volume fraction and particle diameter, aligned with typical behavior exhibited by nanofluids under steady-state flow. However, under vibrational conditions, the heat transfer enhancement surpassed that of the pure liquid significantly. As frequency levels rose, the impact of vibrations diminished, while changes in amplitude exerted a more pronounced influence. The most substantial increase, approximately 540%, was witnessed under vibrational flow conditions compared to steady-state flow. The ratio of the heat transfer coefficient was about 28% higher when the flow was subjected to uniform heat flux but under unsteady-state conditions. However, there was not much growth in the outlet temperature observed.

Flow-controlled thermal response test and its comparison with the conventional test methods

A novel flow-controlled (FC) thermal response test (TRT) system is introduced to resolve the recently addressed inconsistency between the constant heat flux (CHF) and constant temperature (CT) TRTs. FC-TRT allows us to keep both inlet and outlet temperatures constant and improve the accuracy of CT-TRT. Using the FC-TRT system, four types of TRT experiments are performed, providing CT, CHF, and constant inlet temperature conditions, besides the novel one keeping both temperature and heat flux constant. Thermal conductivities from these TRT measurements are compared, and a good agreement is observed. FC-TRT offers higher accuracy and various TRT applications in one platform.

Hydrothermal performance analyses of an isothermal tube with punched twisted tape turbulator (PTT)

This study represents a pioneering investigation into the impact of a punched twisted tape turbulator on the hydrothermal parameters of a pipe operating under constant surface temperature conditions. The punched turbulator was specifically designed by incorporating cuts with diverse geometries, including semicircular, square, and triangular shapes, into the basic twisted tape turbulator. To evaluate the performance of the punched twisted tape, a comparative analysis was conducted with both a smooth tube and a tube equipped with a basic turbulator. The criterion for selecting the optimal cut geometry was the thermal enhancement factor. Subsequently, the influence of the cut area on the hydrothermal parameters was thoroughly elucidated. The enhancement factor was again utilized to identify the most optimal area. Based on the comprehensive evaluations, it was observed that the turbulator with a semicircular cut geometry and a diameter of 5 mm exhibited superior thermal performance compared to all other geometries. By employing this specific turbulator design, a remarkable enhancement in heat transfer and pressure drop within the heat exchanger was achieved, offering improvements of up to 1.63 and 3.65 times, respectively, when contrasted with the plain tube. The maximum enhancement factor value recorded during the investigation reached 1.09.

Numerical study of functional parameters of compact heat exchanger with the corrugated wall in steady state

Compact heat exchangers have several benefits over other types of heat exchangers, including compactness, a high surface area to volume ratio, and a low-temperature differential. They are frequently employed in the heat integrating process. Herein, a compact heat exchanger is simulated in a steady state using the AnsysFluent 17.2 software pack. The flow regime is laminar and water enters the exchanger at a temperature of 298.15 K, assuming a constant wall temperature condition. This study examines the effects of wall wave formation on fluid flow and heat transfer characteristics. The two parameters, wave altitude, and wave angle, are verified and the resultant corrugation is fitted as a sinusoidal function. As the wave height factor increases, the results show that the temperature and velocity values in the solution field climb. More than 4.5% more has been added to the highest temperature value. It is also shown that the velocity values rise with the wave angle coefficient. The greatest rise is 50%. The Performance Ratio is also examined in this study. The findings show that the angle coefficient of 0.5π and π and the altitude coefficient of 0.2 provide values for the Performance Ratio that are higher than the unit.

Temporal numerical analysis of beeswax PCM melting in a cube geometry subjected to a constant wall temperature condition

The ability of phase change materials (PCM) to store thermal energy has gained wide application area, like battery thermal management, solar water desalination and many other. The melting process of beeswax phase change material within the cube geometry with constant wall temperature (65 °C) boundary condition has been investigated using solidification and melting model. The fluid flow and heat transfer governing equations are solved using second order finite volume scheme. A PRESTO algorithm is applied for pressure-velocity coupling. The convergence criteria of 10−10 have been selected for energy equation, while 10−8 is selected for both momentum and continuity equations. The results like percentage variation along length-height and height-width plane for transient liquid fraction and temperature has been plotted, along with velocity streamlines within the cube geometry. From the obtained results it is concluded that the melting fraction and temperature of beeswax PCM is different in different planes and the major factors which affect the complete melting process is wall temperature, and the geometry. A difference of more than 0.1 °C in temperature has been recorded between mid-length-height and height-width plane while a difference of more than 2% in liquid fraction of PCM is observed. Even the uniformity of temperature and liquid fraction is notably influenced and vary along length, height, and width of cube geometry. Thus, it is concluded that melting process of PCM may affect the ability to store and release the heat energy which further affect the performance parameters of applied physical system.

Numerical study on flow and heat transfer characteristics of rectangular mini-channel of interpolated double S turbulators.

In this study, we propose a new type of small-channel plug-in, the double S turbulators, for passive heat transfer enhancement to improve the flow and heat transfer performance of the fluid in the channel. In the range of Reynolds number 254.51~2545.09, under constant wall temperature heating conditions, the effects of interpolated double S turbulators with different long axial radii (1mm, 1.5mm, 2mm) on the average Nusselt number, pressure drop, total thermal resistance and field synergy number in the rectangular mini-channel were studied. The simulation results show that compared with the smooth rectangular mini-channel, after interpolating double S turbulators with different long axial radii (1mm, 1.5mm, 2mm), the average Nusselt number increased by 81.74%~101.74%, 71.29%~94.06%, 67.16%~88.48%, the total thermal resistance decreased by 45.1%~50.72%, 41.72%~48.74%, 40.28%~47.2%, and the number of field synergies increased by 85.58%~111.65%, 74.1%~102.6%, 69.64%~96.12%. At present, there are few studies on the boundary condition of constant wall temperature, and this paper supplements the research on this aspect. At the same time, the heat transfer performance of the rectangular mini-channel of the interpolated double S turbulators is stronger than that of the ordinary smooth rectangular mini-channel, which not only provides a new idea for the manufacture of micro heat dissipation equipment, but also improves the heat transfer performance of micro heat dissipation equipment and improves its work efficiency. According to the simulation data, the prediction formula of average Nusselt number and pressure drop was established by nonlinear regression method, which can be used to predict the flow and heat transfer characteristics of the rectangular mini-channel of the interpolated double S turbulators.