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Heat and Mass Transfer
Journal Prestige (SJR): 0.448  Citation Impact (citeScore): 1 Number of Followers: 28  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1432-1181 - ISSN (Online) 0947-7411 Published by Springer-Verlag  [2468 journals]
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- Assessment of carrier agents in terms of physicochemical, energy analyses
and bioactive constituents of blackberry (Rubus fruticosus L.) powder
processed by convective and hybrid drying methods-
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Abstract: Abstract In this study, the effect of maltodextrin, powdered sugar, and corn starch carrier agents used at different ratios (5% and 10%) in the convective dryer at 65 ºC and hybrid dryer (microwave + convective) at 350 W + 65 ºC to produce blackberry powder was investigated. Drying kinetics, energy analyses, physical, flow properties, and biochemical analyses of blackberry powder production processes were investigated. Drying rates in drying processes varied between 0.0052–0.0477 g moisture/g dry matter minute. Effective moisture diffusion values were determined between 3.36 × 10–8-2.57 × 10–7 m2/s. Specific moisture absorption rate and specific energy consumption values were found to vary between 0.0019–0.0034 kg/kWh and 237.15–530.00 kWh/kg, respectively. Tapped density was determined in the range of 1.666–2.765 g/ml, while bulk density was determined in the range of 1.319–1.937 g/ml. The wettability values of blackberry powders were found to vary between 2.00–27.67 s. Drying processes did not preserve the color values of fresh blackberry puree (p < 0.05). In bioactive findings, total phenol content values were 16.756–25.876 µg GAE/g−1 dw, total monomeric anthocyanin values were 229–1.469 µg cy−3-glu/g−1 dw, total flavonoid values 3.958–5.080 mg KE/kg dw and total antioxidant activity values 406–500 µmol TE/g−1 dw.
PubDate: 2024-08-24
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- Cattaneo-Christov and Darcy-Forchheimer heat flux on Reiner-Philippoff
fluid with Velocity and Thermal Slip Boundary Condition under heat
Sink/Source-
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Abstract: Abstract Reiner–Philippoff (RP) fluid flow above a heated sheet concluded the model of Cattaneo–Christov heat flux for Darcy-Forchheimer is implemented in this work. The influences of thermal radiation, heat source/sink, velocity, and thermal slip boundary conditions are also deliberated. The transformations are used to convert obtained partial differential equations into a set of ordinary differential equations, and they are solved numerically using the shooting method (RK-4) solver with the help of the computational software MATLAB. The dimensionless temperature and velocity numbers are further developed. More engineering curiosity of local Nusselt and Skin frictions are tabulated, depicted, and interpreted. The study presents graphical and tabular illustrations depicting flow parameters, velocity profiles, and temperature profiles. Key conclusions drawn include, When the inertia coefficient \({F}_{r}\) increases, the velocity field \(f^{\prime}(\eta )\) decreases. Analytical calculations are performed for the flow of a Reiner-Philippoff fluid over a shrinking sheet, considering influences such as thermal radiation, velocity slip, and temperature fluctuations. Increased heat absorption correlates with higher Nusselt numbers, whereas temperature generation lowers wall temperatures. The skin friction magnitude gradually increases in the order of dilatant, viscous, and pseudo-plastic fluids, respectively.
PubDate: 2024-08-23
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- Enhanced CeO2 evaporation from refractory crucibles (Mo, Ta, W)
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Abstract: Abstract The study is devoted to enhanced CeO2 evaporation in the temperature range between 2130 and 2650 K from refractory crucibles made of different materials: molybdenum, tantalum, and tungsten. The composition datum of vapor and films deposited on collectors receiving evaporation products were obtained by quadrupole mass spectroscopy and by energy-dispersive X-ray spectroscopy. One of approximation coefficients of the temperature dependence of CeO2 vapor in the range between 2150 and 2220 K was measured. The study is of interest for a variety of technologies utilizing refractory oxide evaporation with high productivity, including the plasma mass separation methods.
PubDate: 2024-08-13
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- Theoretical analysis of hot oil carrying in hydrostatic bearing
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Abstract: Abstract Through the analysis of hot oil carrying theory, the problem of oil film heat accumulation in hydrostatic bearing can be revealed, so as to avoid serious lubrication failure caused by heat accumulation. In this paper, the hot oil carrying factor is defined and the mathematical model of the thermal oil carrying characteristics of the oil film is established by taking the beveled double rectangular oil pad hydrostatic bearing as the object, and the hot oil carrying law under different working conditions is obtained by changing the inclination angle of the beveled oil pad at 0.0230°, 0.0250° and 0.0280°, respectively. Theoretical calculations and simulation studies show that within the range of the circumferential inclination of the oil pad with better dynamic pressure effect of the bearing, the inclination has little effect on the oil film hot oil carrying. When the speed of the workbench is lower than 10r/min, no oil film hot oil carrying phenomenon occurs. When the speed is in the range of 10r/min-100r/min, a part of the load will cause the phenomenon of oil film hot oil carrying. And when the speed exceeds 100r/min, the heat accumulation of the oil film is the most serious at this time. There are many reasons for the lubrication failure of hydrostatic bearings, and hot oil carrying is a new research direction, this paper starts from the oil film heating mechanism of beveled oil pads hydrostatic bearings, and describes the phenomenon of hot oil carrying.
PubDate: 2024-08-13
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- Post-dryout heat transfer in circular tubes using R-134a: experiment and
correlation assessment-
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Abstract: Abstract Post-dryout heat transfer plays an important role in the safety analysis of nuclear reactors or in the design of once through steam generators, and thus attracts great interest in the research community and technical applications. In the present study, experiments on post dryout heat transfer were conducted in a uniformly heated tube test section using Freon R-134a with the following range of parameters; pressure from 1.1 to 2.8 MPa, mass flux from 300 to 2000 kg/m2 s, heat flux from 20 to 140 kW/m2, and local thermal equilibrium vapor quality of more than 100%. Both procedures with increasing and decreasing heat flux were applied, to examine the hysteresis phenomenon. In general, excellent reproducibility of experiments is proven. The behavior of wall temperature and the effect of various parameters on post-dryout heat transfer can be well explained with mechanistic processes. In total, about 9000 data points were obtained and provide a valuable data base for future development of prediction models. Based on the test data gathered, five widely applied correlations of post-dryout heat transfer were selected and assessed. It was found that both correlations using thermal equilibrium approach have a much better prediction capability than the other three correlations based on thermal non-equilibrium conditions. Further analysis reveals that the main deficiency in the thermal non-equilibrium correlations is in the prediction of actual superheating of vapor, which requires obviously further improvement.
PubDate: 2024-08-10
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- Aerodynamic performance and cooling effect of exhaust passage in steam
turbine with new water spray scheme-
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Abstract: Abstract During the actual operation of the power plant, the steam turbine will appear to operate under low load conditions. This paper proposes a novel water spray arrangement for the exhaust channel. Spraying ports are evenly arranged on the cone wall so that the direction of water spraying is opposite to that of the exhaust steam flow (reverse spraying). The feasibility of the nozzle was verified by simulation calculations of existing wind tunnel experiments. The results show that evaporation increases with decreasing load. And the evaporation volume is greater in the reverse spraying than in the down spraying (the direction of water spraying is the same as the direction of steam flow), with a maximum difference of 0.42 kg/s. The deterioration of the aerodynamic performance in the exhaust passage after water spraying can be attributed to the combined effect of the evaporation of water droplets and droplet interference with the flow field. The maximum reduction of 8.17% in the static pressure recovery coefficient in the reverse spray mode increased the total pressure drop by 377.4 Pa. After the water spraying, the temperature dropped significantly compared to before the water spraying. In reverse spraying, the vortex scale in the exhaust passage becomes larger, the return vortex flow increases, the volume absorption ability is stronger, the water droplets and steam contact time is long, good temperature reduction is achieved, and the temperature of the leaf root high-temperature zone is reduced. The maximum difference in temperature drop between the two spraying methods is 56.87 K. The results of this paper provide a reference for the cooling of the exhaust passage when the turbine is operated under low flow conditions for a long time.
PubDate: 2024-08-09
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- Micro-fin tubes for improved flow boiling heat transfer in refrigeration
systems: a performance comparison with R134a and R407c refrigerants-
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Abstract: Abstract This study investigates the flow boiling heat transfer characteristics of refrigerants R134a and R407c in horizontal micro-fin tubes. We conducted experiments across a range of heat flux (15–35 kW·m−2), mass flux (50–250 kg·m−2 s−1), and saturation temperature (15 °C-25°C) conditions. Our findings reveal that R134a consistently exhibits a higher heat transfer coefficient (HTC) compared to R407c, making it advantageous for applications requiring efficient heat transfer. However, R134a also shows a tendency towards premature dry-out flow patterns at higher heat fluxes, which could limit its effectiveness under certain conditions. In contrast, R407c demonstrates more stable flow regimes, maintaining wavy-annular and annular flows without early dry-out, which highlights its robustness at higher heat fluxes. Flow pattern maps indicate that higher heat fluxes promote the formation of wavy and annular flow patterns in both refrigerants, with R134a transitioning to dry-out flows more readily than R407c. The influence of saturation temperature on HTC was also significant, with lower temperatures resulting in higher HTCs for both refrigerants. This can be attributed to the increased thermodynamic driving force for phase change at lower temperatures. Our study aligns with previous research, corroborating the critical role of micro-fin tubes in enhancing HTC. The findings have practical implications for the design and optimization of refrigeration systems, emphasizing the need to carefully select refrigerants and operating conditions to achieve efficient and stable heat transfer performance.
PubDate: 2024-08-08
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- Predicting energy transfer to the workpiece in wire electrical discharge
machining using inverse heat transfer technique-
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Abstract: Abstract In the context of wire electrical discharge machining (WEDM), determining the fraction of thermal energy transferred to the workpiece (fc) is crucial for numerical modelling. This information is necessary to anticipate material removal mechanisms and understand thermal behaviour. In this study, two metaphor-less Rao algorithms are modified to solve the inverse heat conduction problem (IHCP) for the estimation of fc during the WEDM process without knowing any prior information on the transient functional form of fc. These two algorithms are compared in terms of accuracy and convergence speed. The Rao-1 algorithm stands out with high accuracy and rapid convergence. To evaluate the algorithm applicability in estimating fc, the following cases are considered: (1) a numerical investigation with artificial Gaussian error in simulated temperature readings and (2) a real-time experiment on WEDM setup with varying discharge currents. The RMS error between the actual and estimated value of fc with SS-304 material during numerical investigation is found to be 562 W/m which is just 0.008 times of heat source. Real-time experiments reveal that the discharge current is directly proportional to the total energy supplied by the wire as well as fc. The fc values estimated by the proposed inverse algorithm with various discharge currents fall within the range of 15–18%, aligning with the existing literature. This shows the proposed methodology is accurate and can be extended to incorporate other machining processes.
PubDate: 2024-08-06
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- PLC and SCADA based temperature control of heat exchanger system through
fractional order PID controller using metaheuristic optimization
techniques-
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Abstract: Abstract SCADA systems play an important role in tracking the behaviour of critical process variables and connecting geographically dispersed subsystems at the industrial plant level. This article presents a PLC and SCADA-based control framework to automate and supervise the temperature control processes in the heat exchanger plant. The OMRON (NX1P2-9024DT1) PLC is interfaced with the Wonderware InTouch SCADA system to gather data, create a simulated temperature control prototype and carry out the necessary control operations within the heat exchanger plant. The PLC controls the entire process and programming of PLC is done using Sysmac studio automation software using the ladder programming language. The proposed system controls the temperature of the heat exchanger system through PID and Fractional Order PID (P \({\text{I}}^{\uplambda }{\text{D}}^{\upmu }\) ) controllers with Integral Anti-windup technique. Various control strategies like Cascade Control, Feedforward Control and Smith Predictor for time delayed process are discussed for controlling the temperature of the process. The performance of both PID and fractional order PID controllers is optimized using adaptive heuristic optimization techniques like Genetic Algorithm (GA), Ant Colony Optimization (ACO) and Particle Swarm Optimization (PSO). In control system design and analysis, the calculated performance indices are used as quantitative measures for evaluating the performance of a system. The combined form of temperature controller with Cascade control, Feedforward control and dead-time compensator is modelled and examined for simulation using MATLAB. Simulation and real-time experimentation analysis of the developed controllers are executed with metaheuristic optimization techniques based on different performance indices like ISE, IAE and ITAE.
PubDate: 2024-08-06
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- Numerical simulation of heat transfer performance and convective vortex
evolution in a phase change thermal storage device with dispersed heat
sources-
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Abstract: Abstract A numerical model based on the enthalpy method for solidification/melting that incorporates liquid-phase convection was established for a shell-and-tube phase-change thermal energy storage device with dispersed heat sources. This model optimized the heat source structure and simulated the phase change process, thermal storage performance, and evolution and effects of convection-induced vortices. To overcome the limitations of melting blind spots in traditional inner-tube heat sources, a dispersed heating approach was introduced to optimize the heat source distribution on the inner and outer tubes without changing the heat exchange area. The optimal heat source model demonstrated superior heat transfer performance, featuring an inner-tube top heat source and three uniformly distributed outer-tube bottom heat sources at a dispersion angle of 60°. It reduced the complete melting time by 70.88% compared to the inner-tube heat source alone and by 51.99% compared to the outer-tube bottom heat source. The dispersed heat sources effectively utilized the natural convection benefits at the upper inner side and enhanced the heat transfer at the lower sections to address the melting blind spots of the central heat source, thereby improving the uniformity of the process. The enhancement in heat transfer within the dispersed heat source model is primarily due to the optimized heat source distribution, which facilitates a more dispersed and uniform vortex evolution during the phase change. This promotes the development of the liquid-solid interface and reduces the mutual interference in convection vortex expansion. Hence, the internal heat transfer rate and thermal storage capacity of the system are improved.
PubDate: 2024-08-06
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- Numerical investigation of the heating efficiency of CO2 heat pump water
heater system in cold environments-
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Abstract: Abstract This paper introduces a novel a CO2 mechanical subcooling heat pump water heater (MSHPWH) to improve the heating performance in low temperatures. By utilizing a mechanical subcooling (MS) cycle, additional heat is supplied to cooling water, improving system efficiency. The study evaluates the heating COP (COPh), power consumption and temperature of hot water under various steady-state operating conditions. Results indicate that the COPh of the MSHPWH increases by 44% to 57% compared to conventional HPWH as ambient temperatures range from -25 ℃ to -5 ℃. The MS cycle proves beneficial, with a subcooling range of 4 ℃ to 20 ℃. Adjusting the refrigerant mass flow rate ratio enhances heating output and hot water temperature. Changes in the mass flow rate ratio impact COPh and the temperature of hot water concurrently. This research highlights the innovative MS cycle’s significant role in enhancing CO2 heat pump water heater performance in cold climates, showcasing its potential as an eco-friendly and efficient heating solution.
PubDate: 2024-08-05
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- Investigation of the radial uniform and variable inflow profiles to
improve production in the perforated horizontal wellbore-
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Abstract: Abstract This study delved into the efficacy of enhanced oil production (EOP) within perforated horizontal wellbores across diverse flow profiles. The authors implemented five distinct configurations, encompassing uniform radial air injection (profile 1) and variable radial air injection (profiles 2–5), with a particular emphasis on the concomitant production of liquid and air phases. Additionally, the study examined the frictional behavior along the perforated wellbore. Liquid production was demonstrably amplified throughout the bubble, plug, and slug flow regimes; however, a decline was observed in the stratified, stratified transition, and stratified wave flow regimes. Notably, the liquid product exhibited a direct correlation with both the mixture flow rate and its associated Reynolds number, signifying an increase with holdup and a decrease with void fraction. Conversely, air production displayed a positive association with a higher air flow rate. Overall, profiles 2 and 4 yielded the most favorable production during the bubble, plug, slug, and stratified flow regimes. In contrast, profile 3 emerged as the optimal configuration for the stratified transition and stratified wave flow regimes. The friction factor remained relatively constant with profile 1, experienced a reduction in profile 2, and exhibited an escalation in profile 3. Additionally, it increased in the middle of profile 4 and decreased at the center of the perforated section in profile 5. The friction factor behavior of profile 1 remained stable and smooth due to the invariant air flow rate throughout the perforated section. Conversely, some fluctuation was observed in profile 2 due to the inherent variability of the radial air injection along the perforated section. Importantly, the experimental and numerical results demonstrated satisfactory agreement across all flow patterns, with some minor discrepancies noted in the static pressure drop behavior during the bubble, dispersed bubble, and slug flow regimes.
PubDate: 2024-08-02
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- Dual scale porous medium model of lung congestion caused by tuberculosis
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Abstract: Abstract Pulmonary tuberculosis is a chronic respiratory disease and lung infection that can be fatal if left untreated, as severe cases lead to compromised oxygen exchange at the alveolar level. This study uses a dual-scale porous medium model and computational methods to understand the nature of tuberculosis infection spread within the lungs and its effects on the alveolar oxygen exchange. The entire lung is modelled as a global, equivalent, heterogeneous porous medium comprising three zones with varying permeabilities that correspond to 23 generations of airflow branches. Airflow during each breathing cycle is simulated by solving transient mass and momentum transfer equations across the three zones of the global model. A separate local model is invoked in zone 3, to analyse oxygen exchange between the alveolar airflow and incoming capillary blood via mass transfer equations. The transient mass exchange equations are solved in the local model to yield the percentage of oxygen transferred to the blood. Tuberculosis spread – and hence, the congestion of the lung – is introduced by modifying the permeability and porosity of the global porous medium model. The impact of infection on the overall bloodstream oxygen content is evaluated by concurrent use of the global and local models. For the case with sudden reduction in immunity, severe infection condition is observed at \(\varvec{86\%}\) of the total infection spreading time and at \(\varvec{75\%}\) for the case with gradual reduction in immunity. For \(\varvec{40\%}\) increase in immunity beyond the \(\varvec{50\% \Gamma }\) stage, it is observed from the simulations that the severe infection situation is completely avoided, preventing any further tuberculosis spread.
PubDate: 2024-07-31
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- Effects of magnetic field on CO2 hydrate phase equilibrium
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Abstract: Abstract The conditions and influencing factors of hydrate formation is significant for hydrate technology. Combining with the existing literatures and the experimental data of this work, the phase equilibrium of CO2 hydrate in (NaCl/CaCl2/MgCl2) ionic solutions, pure water-sediment system and (NaCl/CaCl2/MgCl2) ionic solution-sediment systems under the static magnetic field (0.39 T) was studied. Moreover, the effect mechanism of magnetic field on hydrate phase equilibrium in different systems was analyzed in terms of intermolecular interaction. Under the same pressure, the magnetic field increased the phase equilibrium temperature of CO2 hydrate by 2.0–2.8 K in the three ionic solutions, which improved the hydrate formation conditions. This is mainly due to that the magnetic effect increases water activity and weakens the ionic hydration shells, thus promotes hydrate formation. In addition, compared with the ionic solution systems without magnetic field, the magnetic field increased the hydrate phase equilibrium temperature by 0.1–2.5 K in the ionic solution-sediment systems. However, the degree of temperature increase is less than that in the magnetic field-ionic solution systems, which is because the magnetic field enhances the binding between ions and the sediment particle in sediment-bearing systems. Compared with the magnetic field-ionic solution systems, the water activity in the magnetic field-ionic solution-sediment systems is lower, which makes hydrate formation more difficult. Moreover, with the movement of cations and anions in magnetic field, the crystals may be formed due to ion collisions, enhance the capillary action in ionic solution-sediment systems, and then hinder the hydrate formation. Therefore, the sediments can weaken the magnetic field promotion to hydrate formation.
PubDate: 2024-07-30
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- Numerical and experimental analysis of the sinusoidal heat flux source of
heat transfer in laminar flow in a tube for single phase flow-
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Abstract: Abstract This article deals with the application of the temperature oscillation method (TOIRT method) to the laminar flow of water in a pipe. This dynamic and contactless method was derived for the assumption of homogeneous temperature on the fluid side, but this assumption is violated in the case of laminar flow. Numerical simulations were used to discover the fundamental influence of the amount of incident heat flux, which is modulated by the sine function, on the resulting local values of the heat transfer coefficient. The frequency of the transmitted signal, on the other hand, has no effect. The experimental measurement confirmed the numerical results even with a deviation of 25%, which is still a good result due to the sensitivity of the experimental method in this area.
PubDate: 2024-07-26
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- Variation in the electrical properties of gabbro after microwave heating
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Abstract: Abstract Microwave assistance has the potential to reduce the energy input required for mechanical rock breaking. This study systematically investigated the changes in electrical properties (specifically resistivity, capacitance, and impedance) of gabbro after microwave heating during the graded loading process, as well as its internal fracture mechanism. The findings indicate that the variations in resistivity, impedance, and capacitance of gabbro can be divided into three stages during the graded loading process: the compaction stage, elastic-steady cracking stage, and nonlinear crack propagation stage. When the strain level exceeds 70%, the resistivity and impedance start to increase, and the capacitance begins to decrease. The study also identifies a significant positive correlation between microwave power and the rate of temperature increase on the rock surface. A critical power threshold of approximately 2 kW is observed, below which achieving rapid temperature rise becomes challenging, but beyond which the temperature escalates swiftly with the energy input. Once the temperature exceeds 350 °C, rupturing mineral inclusions generate numerous microcracks, causing resistivity and impedance to exponentially increase. Furthermore, microwave heating induces a temperature differential exceeding 200 °C between the internal and external regions of the rock. Under the same radiation energy, high-power short-duration radiation is more likely to generate thermally induced cracks within the rock. The rapid expansion and heating of absorbent minerals, as well as the rupture of inclusions, further intensify the propagation of microcracks, greatly reducing the mechanical properties of the rock. This study will provide theoretical guidance for microwave-assisted mechanical rock excavation.
PubDate: 2024-07-26
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- Thermal enhancement of a constructal PCM cylindrical heat sink used for
prosthetic cooling application-
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Abstract: Abstract Amputees often experience high temperatures between the amputated limb and the prosthetic socket, necessitating the use of cooling devices to mitigate this issue. However, challenges arise with the location and size of conventional heat sinks. This research proposes a novel heat sink utilising a phase change material (PCM) to dissipate heat. The leg was chosen as the site for the heat sink, designed in a cylindrical shape. Coolant flow pipes were arranged in a branched configuration inspired by constructal theory, constrained by the dimensions of the artificial leg. The degrees of freedom for the constructal design are branches akin to arterial and venous branching, aiming to minimise pressure drop. Four heat sinks with varying degrees of branching were compared based on temperature reduction, heat dissipation, pressure drop, phase change material melting capacity, and operational efficiency. The cylindrical heat sink measures 50 mm in diameter and 300 mm in length. Ice was employed as the PCM, with water served as the working fluid. The working fluid's temperature and flow rate were maintained at 40 °C and 0.2 L/min, respectively. The experimental work was prepared to validate the theoretical model. The study revealed that the proposed heat sink design, with increased branching, led to a significant temperature reduction, achieving up to 39.62%. Moreover, heat dissipation increased by 236% compared to a single-tube heat sink. The use of branched pipes resulted in a manageable increase in pressure drop, peaking at 39.9 Pa, well within pump specifications, while markedly enhancing heat dissipation. The melting time of the PCM and the melting area increased as the number of branches of the heat sink increased. Ultimately, applying constructal theory in heat sink design for PCM demonstrated its superior performance within spatial constraints, providing a promising solution for prosthetic cooling.
PubDate: 2024-07-20
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- Impact of heat flow from the cylinder sidewalls on thermocapillary droplet
flow in a vibrating fluid: 3D study-
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Abstract: Abstract The thermocapillary motion of droplet in a vibrating fluid in a cylinder heated from the top and sides and cooled from the bottom is studied, using a three-dimensional computational fluid dynamics (CFD) model based on volume of fluid (VOF) created with Ansys-Fluent software. The outcomes support the accuracy of the Marangoni phenomenon and are in line with data published in literature. The behavior of the drop is not only impacted by the temperature difference between the top and bottom, but also by heated side surfaces and mostly by vibration. Different flow patterns are observed which directly impact the droplet’s arrival time. The results proof that the neglected frequency and amplitudes of vibration in the presence of gravity have a significant and evident impact on the behavior of fluids in a zero-gravity environment. The change of vessel height also has a significant influence especially on the host fluid properties.
PubDate: 2024-07-19
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- CFD and ANN analyses for the evaluation of the heat transfer
characteristics of a rectangular microchannel heat sink with various
cylindrical pin-fins-
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Abstract: Abstract Electrical equipment extensively uses Microchannels (MCs) for cooling. Due to their complexity, it is challenging to evaluate the features of the fluid flow and heat transfer processes in MC pin-fin heat sinks. Numerical approaches have been frequently employed in MC design to enhance efficiency. Machine learning methods have recently enabled the assessment of flow and heat transfer research in these devices. In this study, numerical calculations have been made to obtain outlet fluid temperature, the average Nusselt number, and pressure drop, using the computational fluid dynamics (CFD) software, ANSYS Fluent. Previous experimental work validates the numerical model by examining the average Nusselt number and the apparent friction factor. Three distinct ratios of fin spacing to fin diameter (l/d = 2, 4, and 6) and five different values of Reynolds number (Re = 50, 75, 100, 125, and 150) are considered. A constant ratio of fin height to channel height (h/H = 0.25) is maintained, and the inlet fluid temperature is set to 291.15, 294.15, 297.15, and 300.15 K. Numerical calculations have been conducted for cases of uniform and non-uniform heating, where bottom wall temperatures of 323.15 K and 317.15 K were considered, respectively, for a fixed fin surface temperature of 323.15 K. Using the results of the numerical simulations, a multi-layer perceptron (MLP)-structured artificial neural network (ANN) is trained. The Levenberg-Marquardt (LM) training method is employed in the hidden layer, using 17 neurons for the training procedure. The results of the numerical simulations show that the average Nusselt number increases linearly with the Reynolds number, except for the non-uniform heating case of Re = 50. The average Nusselt number and pressure drop are inversely proportional to fin spacing for all cases. There is also a linear increase in pressure drop with the Reynolds number, since the flow regime considered in this study is laminar. The ANN model predicts the outlet fluid temperature, the average Nusselt number, and the pressure drop, with variation rates of -0.0027%, -0.075%, and − 0.0004%, respectively.
PubDate: 2024-07-12
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- Heat transfer characteristics of cascade phase change energy storage
composite pipeline-
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Abstract: Abstract In the context of dual-carbon strategy, the insulation performance of the gathering and transportation pipeline affects the safety gathering and energy saving management in the oilfield production process. PCM has the characteristics of phase change energy storage and heat release, combining it with the gathering and transmission pipeline not only improves the insulation performance of collecting and transporting pipes, but also extends the safe shut time during the shutdown. Proposed a thermal model of a PCM-based composite energy storage pipeline combining the character of phase transformation between PCM and crude oil has been established. The heat preservation performance of the combined energy storage pipeline was evaluated by numerical simulation.This paper analyses the heat transfer performance of complex energy storage pipes, and considers the influence of natural convection and variable temperature zone on insulation performance.On this basis, the structure design of cascade phase transition was proposed, the optimized cascading composite pipe was presented, and the performance of different insulation structures was compared.
PubDate: 2024-07-11
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