Shell Side Research Articles

Development and preliminary verification of a 1D–3D coupled flow and heat transfer model of OTSG

Introduction: A simulation model was developed by coupling a one-dimensional (1D) system code and 3D CFD software, to analyze the three-dimensional (3D) flow and heat transfer characteristics of the once-through steam generator (OTSG).Methods: The shell side of the OTSG was simulated by FLUENT, and the tube side was simulated by the system code LOCUST. Through spatial mapping, the 1D and 3D simulations were coupled along the outer wall of the OTSG's helically coiled tubes.Results and Discussion: This coupling method enabled the acquisition of high-resolution flow and heat transfer characteristics of the OTSG, and the error of heat flux calculation result by the coupled model is within 15%. Through coupling simulation analysis of the prototype OTSG, it was found that the inlet and outlet temperature difference reached as high as 150°C. The unevenness of the radial temperature distribution increased along the flow direction, and the wake swing effect caused by the sweeping flow of the tube bundle at the exit position was evident. The results of this study provide reference and a coupled simulation method for the engineering design and thermal-hydraulic characteristics analysis of OTSG.

Modeling of Integrated Hollow-Fiber Solar-Powered VMD Modules for Desalination for a Better Understanding and Management of Heat Flows.

The direct integration of membrane distillation and solar energy collection in a single module is a promising technology for autonomous seawater desalination in remote regions; however, the modeling and design of such modules are challenging because of the coupling of the radial and longitudinal heat and mass transfers. In a previous study, we provided as a first modeling approach a hollow fiber solar collector vacuum membrane distillation (VMD) module, considering a constant temperature at the shell side and a pure water feed. Here, a full model is developed to describe the coupled effects of the solar collector and a hollow fiber VMD module operating in an outside/in mode with saline water. The model considers all the main phenomena (membrane distillation, temperature and concentration polarization, absorption of solar radiation and energy balances over the solar collector, radial and longitudinal heat and mass transfer, seawater properties, and more than 30 variables). Applied to simulate the behavior of a semi-industrial-scale module, it allows the influence of solar radiation on the performance/limits of the integrated module to be discussed based on the radial and longitudinal profiles and heat flows. The model can be used to identify key points in the module design to better utilize solar radiation and manage heat flows.

An Experimental Study of Heating Heavy Fuel Oil by Hot Air using Helical Fins in a Double-Pipe Heat Exchanger

In present work, the effect of helical fins with height 20 mm and pitch 100 mm on the performance of the double pipe heat exchange investigated experimentally. The heat exchanger had been chosen as a heat recovery device in bricks factory to recover heat from exhaust gases to preheat the heavy fuel oil. Air had been chosen as a hot gas instead of furnace exhaust gases because of the similar thermal properties and it flows in the inner pipe with different velocity (20, 27, and 34) m/s and inlet temperature (200, 225) °C while, heavy fuel oil enters shell side with counter flow at mass flow rates (0.06, 0.08, and 0.1) kg/s and constant inlet temperature of 40 °C. Both of pipes and helical fins are made from stainless steel. The experimental results show that increasing Reynolds number from 139139 to 333934 led to increase heat transfer rate, oil outlet temperature, overall heat transfer coefficient and effectiveness of heat exchanger with (8%, 4%, 5% and 5%) respectively while, increasing oil mass flow rate from (0.06 to 0.1) kg/s cause decreasing oil outlet temperature and effectiveness of with (10% ,14%) respectively. The results shown the double pipe heat exchanger with helical fins produce heat transfer rate and oil outlet temperature higher than smooth double pipe heat with average 15% and 8.6%, as well as increasing Nusselt number, Overall heat transfer coefficient and effectiveness of heat exchanger with average 26%,15% and 13% respectively. The results clear that, for 225°C exhaust air and velocity 27 m/s, the application of double pipe with helical fins by preheat heavy fuel oil could reduce the viscosity and reduce electric power required and save 1.69 MW annually for one factory.

Flange Leak Investigation on Kettle Heat Exchanger Operating at Low-Temperature Condition

A kettle-type evaporator heat exchanger (TEMA BKU) is utilized to cool natural gas on the tube side from −34 °C to −55 °C, using Multi-component Refrigerant (MCR) as the cooling medium on the shell side. During operation, the heat exchanger encountered recurrent leakage issues at the channel-tubesheet bolted flange joint, particularly during the cooling down process. The primary objective of this research is to identify the causes of leakage and to propose viable solutions for minimizing the risk of leakage. To achieve this, Finite Element Method (FEM) was employed as an investigative tool to analyze the mechanical factors contributing to leakage. Results from the FEM investigation indicate that the leakage in the bolted joint of the heat exchanger is attributed to reduce of gasket seating stress as an effect of bolts self-loosening, influenced by several factors such as bolts plastic deformation, flange stiffness characteristics, and uneven temperature distribution. The study also reveals that gasket seating stress decreases after each shutdown compared to the previous start-up due to plastic deformation on bolts and flange gasket surfaces after shutdown. The findings of this study provide critical insights into the mechanical behavior of bolted flange joints in heat exchangers and offer guidance for their improved design and maintenance, enhancing operational reliability.

Structural Integrity Assessment and Fatigue Evaluation of Feed Water Nozzle of 700MWe PHWR Steam Generator

Steam Generator (SG) is a prime component in Indian Pressurized Heavy Water Reactors (PHWRs). The Steam Generator consists of an inverted vertical U-tube bundle in shell for primary flow (Heavy water). The shell side is designed for recirculation. Steam Generator is a Safety Class-1 component and designed & fabricated as per the requirements of ASME Section III, Subsection-NB.Secondary side of the steam generator consists of a shell, Feed Water Nozzle (FWN), Steam Outlet Nozzle, moisture separator, drier, tubes and shroud. The principal material of construction for secondary side pressure boundary is of low alloy carbon steel. Secondary side of steam generator is subjected various loadings (Dead weight, pressure, pipe reactions & thermal) during normal plant condition as well as transient conditions including severe transient like crash cool down where in the thermal gradients are much higher. To take care of these thermal transient loadings a special thermal sleeve type of design has been incorporated in the FWN.As mentioned above, FWN is subjected to thermal transients throughout its life and susceptible to high thermal gradient which makes it important to evaluate for structural integrity and fatigue failure. This paper covers the approach & results for structural integrity assessment (stress evaluation) and fatigue evaluation (cumulative fatigue damage factor) of Feed Water Nozzle of 700MWe PHWR SG for various Service levels A, B, D & Design. These service conditions comprise of thermal & pressure transients during operating and accidental conditions. Detailed integrity check performed for all conditions by stress categorization at critical locations and qualify primary & secondary stresses against ASME Section III allowable.

CFD Analysis of the Effect of Mass Flow Rate in a Shell and Tube Heat Exchanger Design

Heat exchangers are often found in the chemical process industry, but of all types of heat exchangers, the Shell and Tube Heat Exchanger (STHE) are the most used. The design of shell and tube heat exchangers are continually evolving because of it reduce production costs. A computational fluid dynamics (CFD) simulation was employed using SOLIDWORKS Flow Simulation version 2022 to model the effect of operating parameter such as the mass flow rate on the pressure drop, heat transfer coefficient and the turbulence intensity. The turbulence model adopted for the simulation was the k–ɛ turbulence model incorporating the boundary conditions. Three conditions were studied increasing both shell and tube side mass flow rate, maintaining either the shell or tube constant and then varying the other. The results obtained showed that an increase in mass flow rate have tremendous effect on the pressure drop, heat transfer and turbulence intensity.

The impact of tube bundle layout on the thermal and fluidic behaviour of liquid lead–bismuth eutectic in a helical-coiled once-through steam generator

This study introduces a numerical model to assess the thermal and frictional properties of LBE crossflow over tube bundles on the shell side of a Helical-coiled Once-Through Steam Generator (H-OTSG) considering different arrangements, including inline, obliquely staggered, triangular, and rotated square configurations. The k-ω SST turbulence model combined with Kays turbulent Prandtl number model is utilized to develop the numerical model. The simulation results have been validated against experimental data and empirical correlations. The layouts of the tube bundles significantly influence the generation of transverse flow, vortical structures and rate of heat transfer in the flow domain. The maximum Nusselt number of 8.2 is observed for the triangular layout as significant crossflow is induced, which is a 10% increase compared to the inline arrangement where the Nusselt number is 7.45. Triangle layouts also exhibit a higher friction factor of 0.45, marking a 20% increase compared to the 0.45 friction factor observed in the inline arrangement. Increasing the oblique angle usually reduces the heat transfer rate and friction factor. Yet, at a 45-degree layout, higher turbulence intensity results in a Nu of 7.05, surpassing 6.93 observed at 30° but falling short of 7.15 at 15°. Nu decreases for rotated square arrangements, but a friction factor greater than the inline arrangement is observed at higher diagonal pitches. The Thermal Enhancement Factor (THEF) is employed to assess the thermal effectiveness of the different tube bundle layouts, and the maximum THEF of 1.1 is observed for the layout with an oblique angle of 45°. Favorable THEF values of 1.06 and 1.05 are recorded for the triangular layout and 30-degree oblique angle, respectively. This numerical study will assist the design and development of LBE H-OTSG.

CFD Investigation of Shell and Tube Heat Exchanger: Impact of Various Tube Bundle Combinations on Heat Transfer Coefficient and Pressure Drop

Shell and tube heat exchangers play a crucial role in various industries, including chemical processing, oil and gas, power generation, and HVAC systems. These exchangers are widely used for transferring heat between two fluids while maintaining their separation. The design of a shell and tube heat exchanger consists of a bundle of tubes enclosed within a larger shell. The hot fluid flows through the tubes, while the cold fluid circulates around them in the shell, facilitating efficient heat transfer and pressure drop of the system. The performance of a shell and tube heat exchanger is influenced by various factors, including the configuration of the tube bundle. The choice of different tube bundle combinations can significantly impact the overall performance of the heat exchanger. In this paper, a numerical study is conducted to examine the effects of two combination of circular and square tube bundle with the simple arrangement: i) circular, ii) square, on a shell and tube heat exchanger. COMSOL Multiphysics is employed to model and simulate this heat exchanger under various mass flow rates. The result shown that the combined geometry heat exchanger exhibits the highest overall heat transfer coefficient compared to heat exchangers with single arrangements. The pressure drop on the tube and shell side was also studied for all cases of heat exchangers. The placement of circular tubes in the center and near the shell has a significant effect on heat transfer and pressure losses. It has been demonstrated that the tubes located at the ends of the shell have a much greater impact on heat transfer compared to the tubes positioned in the center.

Experimental investigation on the frictional pressure drop of two-phase fluids in the shell side of LNG spiral-wound heat exchangers

The frictional pressure drop of the two-phase fluids in the shell side of spiral-wound heat exchangers (SWHEs) is essential for the safe and cost-efficient operation of SWHEs. However, the characteristics of frictional pressure drop are not entirely understood yet. To investigate the frictional pressure drop characteristics, we constructed and validated the large-scale experimental platform. This study utilized air and water as working fluids to examine the impact of the total mass flow rate and vapor quality on the frictional pressure drop. The results indicate that the frictional pressure drop increases with the total mass flow rate and vapor quality. As the total mass flow rate continues increasing, the rising mass flow rate will restrain the growth rate of the frictional pressure drop. On the contrary, the rising vapor quality will promote the growth rate of the frictional pressure drop. When vapor quality rises from 0.40 to 0.48, from 0.30 to 0.40, and from 0.19 to 0.27, the frictional pressure drop gradient increases from 40.78 Pa·m−1 to 69.75 Pa·m−1, from 25.62 Pa·m−1 to 57.23 Pa·m−1, and from 21.18 Pa·m−1 to 84.58 Pa·m−1, respectively. In addition, the present study compared the predictive frictional pressure drops of six correlations with the experimental data while also analyzing the predictability of these correlations. Moreover, this study proposed a modified correlation, and the predictive values of the modified correlation met with 95 % of the experimental data with a deviation of ±25 %.

Numerical investigations on optimised shell designs of a U-tube heat exchanger

Previous researchers focused on enhancing the heat transfer rates of heat exchangers using developments on the tube-side components. Nevertheless, the performance of the shell side has been overlooked in all previous studies. Therefore, this study aims to investigate the heat transfer performance, pressure drop, friction factor, exergy, and performance enhancement criteria (PEC) of a heat exchanger due to the geometrical modification on a cylindrical shell. Three modified shell designs were proposed using SolidWorks software: Twisted-square shell model (TSSM), Mirrored-square shell model (MTSSM), and Corrugated-square shell model (CSSM). Their thermofluid performance is simulated using ANSYS-Fluent software at different Reynold's numbers (46941 ≤ Re ≤ 89616). Results have revealed that TSSM attained the highest heat transfer coefficient, with a 24.4% enhancement at Re = 55,476, followed by the MTSSM with 23.1% and TSSM with a 22.1% increment at Re = 81,081. Moreover, the MTSSM showed the most significant improvement in effectiveness, with a 24.64% advancement, followed by the TSSM with a 22.35% at Re = 81,081. Furthermore, the pressure drop experienced by the MTSSM and CSSM was found to be lower than the cylindrical shell and the TSSM at all Re, with the highest reduction of 16.25% and 15.89% by the CSSM at Re = 55,476 and 46,941, followed by the same model at Re = 72,546 and 64,011 with a 15.15% and 15.13% decrement, leading to potential cost savings in terms of lower pumping and operating expenses compared to the TSSM and cylindrical model. On the other hand, the TSSM showed an increment in the pressure drop with the highest increment of 9.94% and 8.82% at Re = 64,011 and 46,941 compared to the cylindrical model. Besides, the friction factor of both the CSSM and MTSSM was found to be much lower compared to the cylindrical shell model with the highest decrement of 16.25% and 15.98% in the CSSM at Re = 55,476 and 46,941 and 13.17% and 12.85% at Re = 81,081 & 46,941 in the MTSSM, and nonetheless increment in the TSSM with the highest increment of 9.94% and 8.82% at Re = 64,011 and 46,941 respectively. However, the TSSM still provides superior heat transfer performance even at its lowest Re = 46,941 with a lower pressure drop compared to the highest Re = 81,081 in the cylindrical shell, indicating that the TSSM can be used at Re ≤ 46,941 and still provides better heat transfer performance than the highest Re applied in the cylindrical shell, resulting in a lower operating and pumping cost to circulate the fluid through the shell. These outcomes demonstrate the positive impact of the optimised shell modifications on the overall efficiency and cost-effectivenessofthesystem.

Numerical simulation of heat transfer performance of spiral wound heat exchanger under sloshing condition

LNG floating production storage and offloading (FPSO) unit is a new type of floating production unit developed for offshore natural gas fields. It performs the functions of natural gas extraction, pretreatment, liquefaction, and storage. In this study, the heat transfer characteristics of a spiral-wound heat exchanger were studied using numerical simulations, which provides a basis for equipment selection and structural optimization of spiral-wound heat exchangers. The main research contents and conclusions are as follows. Under land-based simulation conditions, the heat transfer coefficient of the shell side of the spiral-wound heat exchanger decreases with an increase in the winding angle of the heat exchange tube, decreases with an increase in the spacing of the heat exchange tube, and increases with an increase in the outer diameter of the heat exchange tube. When the winding angle increased from 5° to 8°, the heat transfer coefficient decreased by 6.70%. The heat transfer coefficient of the shell side decreased by 13.21% when the heat exchange tube spacing increased from 14 to 17 mm. The heat transfer coefficient of the shell side increased by 22.89% when the outer diameter of the heat exchange tube increased from 9 to 12 mm. When the sloshing angle is constant, the heat transfer coefficient of the spiral-wound heat exchanger decreases with an increase in the winding angle and spacing of the heat exchange tubes, and increases with an increase in the outer diameter of the heat exchange tubes. When the structural parameters of the heat exchanger are constant, the heat transfer coefficient decreases as the sloshing angle increases. When the sloshing angle was less than 3°, the sloshing promoted heat transfer on the shell side. When the sloshing angle was higher than 7°, the heat transfer effect of the shell side deteriorated considerably, which weakened the heat transfer performance of the heat exchanger. When the sloshing period is constant, the heat transfer coefficient of the wound heat exchanger decreases with an increase in the winding angle and spacing of the heat exchange tubes, and increases with an increase in the outer diameter of the heat exchange tubes. When the structural parameters of the heat exchanger are constant, the heat transfer coefficient increases with sloshing period. When the sloshing period was greater than 15 s, the influence of sloshing on the heat transfer on the shell side of the heat exchanger was relatively weak.

Treatment of Stainless Steel Rinse Waters Using Non-Dispersive Extraction and Strip Dispersion Membrane Technology.

The extraction of Fe(III), Cr(III), and Ni(II) from stainless steel rinse water using non-dispersive extraction and strip dispersion membrane technology was carried out in a microporous hydrophobic hollow-fibre module contactor. The fibres were of polypropylene, whereas the organic extractant DP8R (bis(2-ethylhexyl) phosphoric acid) diluted in ExxsolD100 was used as the carrier phase. The rinse water containing the three elements was passed through the tube side, and the pseudo-emulsion formed by the organic phase of DP8R in Exxol D100 and an acidic strip solution were passed through the shell side in a counter-current operation; thus, a unique hollow fibre module was used for extraction and stripping. In non-dispersive extraction and strip dispersion technology, the stripping solution was dispersed into the organic membrane solution in a vessel with an adequate mixing device (impeller) designed to form strip dispersion. This pseudo-emulsion was circulated from the vessel to the membrane module to provide a constant supply of the organic phase to the membrane pores. Different hydrodynamic and chemical variables, such as variation in feed and pseudo-emulsion flow rates, strip phase composition, feed phase pH, and extractant concentration in the organic phase, were investigated. Mass transfer coefficients were estimated from the experimental data. It was possible to separate and concentrate the metals present in the rinse water using the non-dispersive extraction and strip dispersion technique.

Parameter analysis and rapid design of porosity gradient distribution for open-cell metal foam in the latent thermal energy storage unit

The positive gradient porosity design of metal foam is used to improve the thermal performance of the vertical shell-and-tube latent thermal energy storage (LTES) unit. To optimize the gradient design, quantitative analysis is of vital importance. Therefore, the relative offset number EX is proposed in this study, which indicates the porosity difference between upper/down porosity and the mean porosity. Based on the numerical model of a shell-and-tube LTES unit filled with composite phase change material (CPCM) on the shell side, the effects of parameters, including the inlet HTF temperature and velocity, LTES dimensions, porosity, and thermal conductivity of the metal foam on the optimal gradient design are discussed. The optimal EX exhibits little relation with the inlet temperature but increases with the LTES height and thermal conductivity, while decreases with inlet velocity, porosity, and LTES outer radius. With the correlation between the optimal EX and the relative dimensionless number, the effects of these parameters on the optimal EX are integrated and quantified as experience equations so that the optimal porosity gradient of metal foam and the relative reduction melting time can be rapidly obtained under a wide variety of practical applications.

Effect of Water-Based Nanofluids on the Generation of Entropy in a Shell and Helical Coil Heat Exchanger

A forced convection finding proves that entropy was generated as a result of the heat transfer between the fluids on the coil and the fluids on the shell side. It was found that entropy generation was affected by nanofluid concentration, coil-side fluid flow rate, shell-side fluid temperature, and agitator speed (500 rpm, 1000 rpm, and 1500 rpm) in this paper. The nanoparticle (Al2O3, CuO, and TiO2) weight fractions ranged from 0.3 to 2%. This paper investigates the friction entropy generation rate, the entropy generation ratio, and the thermal entropy generation rate of various nanofluids in laminar and turbulent flow conditions, using existing correlations to guide the investigation. The results revealed that the generation of entropy increased as the Dean number, SS, and fluid temperature on the shell side of the reactor were increased in the laboratory. And, found that the maximum entropy generation rate of Al2O3/water, CuO/water, and TiO2/water nanofluids occurred at 56.4 percent by weight of the nanofluid, 62.1 percent by weight of the nanofluid, and 48.1 percent by weight of the nanofluid.

Optimized Design of Shell and Tube Heat Exchanger with Segmental Baffles

Heat exchangers are the apparatus which is widely used in various industries. They transmit heat among two or more fluid streams. Theoretical analysis done by Kern’s method has been done on Shell and tube heat exchanger with segmental baffle and then experimented in CFD to check Heat Transfer rate and pressure drop with varying number of baffles which is 6, 8 and 10, and by keeping all the rest of parameters constant. It is found that as the number of baffles increase heat transfer rate increases also pressure drop is increases significantly. To optimize model in next step, CFD analysis is has been done by varying baffle cut to 25%, 35% and 45% by keeping same number of baffles which found best in heat transfer rate in earlier Kern’s method. Other parameters like velocity, temperature, pressure and baffle numbers are kept constant. Results obtained from numerical solution are analysed extensively to get the effect of baffle cut on heat transfer rate and pressure drop on shell side. The pressing need of the heat exchanger industry, the tradeoff optimization between the pressure drop and the heat transfer coefficient has been studied to provide an idea to get effects of the change in two parameters, namely, baffle spacing and baffle cut simultaneously and observe how these two will affect the performance of an STHX. An attempt to find the optimum geometric configuration has been carried out with number of baffles. Increasing baffles for same length of shell and baffle cut increases from 25% to 35%, heat transfer rate increases. It is beneficial in elucidating that a higher heat transfer coefficient can be obtained for fewer baffles when coupled with the appropriate baffle cut. So selection of correct optimized shell and tube heat exchanger. The work is carried out for copper tube bundles and steel shell. So optimization of baffle cut with correct number of baffles and reduction in pressure drop studied with CFD tool.

Experimental study of thermal energy storage system for solid particles/ heat transfer oil in shell and tube heat exchangers with H-shaped fins

The solid-state sensible heat storage method is cost-effective, technically simple, and works well across wide temperatures. Using return fines (RFs) as the heat storage medium (HSM) can ease problems like RFs in excess and high energy consumption in the sintering process. This article first characterizes the thermal properties of RFs. Results show a specific heat capacity of 0.67–0.97 kJ/(kg·°C) within 20–380 °C, with stable thermal properties from 100 to 1000 °C. Then, the heat transfer performance of RFs and heat transfer oil (HTO) in a shell and tube heat exchanger is experimentally investigated. H-shaped fins are added to enhance the heat transfer. Stacking solid particles on the shell side can avoid direct contact between the HSM and HTO, the tiny size limitations of HSM particles, and cracking problems caused by thermal expansion. The thermal energy storage (TES) unit operates within 170–270 °C. Effects of different flow rates (30, 20, 10 L/min) and charging/discharging temperatures (300/160, 290/150, 280/140 °C) on system performance are explored. Increasing the HTO flow rate and charging temperature and lowering the discharging temperature can reduce charging/discharging time and enhance average power. Cycle efficiencies for flow rates of 30, 20, and 10 L/min are 86.9%, 85.2%, and 79.5% respectively. The 30 L/min working condition shows the best performance. Remarkably, system performance improvements are relatively limited compared to the 20 L/min setting. Regarding charging/discharging temperatures of 300/160, 290/150, and 280/140 °C, cycle efficiencies stand at 73.3%, 85.2%, and 70.6%, respectively, with the 290/150 °C setting displaying the most favorable characteristics, including the shortest total charge and discharge time of 59.3 min and the highest cycle efficiency. Efforts to enhance the system's insulation and maintain a substantial temperature differential between HTO and HSM are pivotal in accelerating the charge/discharge process and minimizing heat loss.

Effect of chevron angle on the thermofluids performance of shell-and-plate heat exchangers – A numerical approach

This study conducts a detailed numerical study upon the effect of chevron angle on the thermofluids characteristics of shell-and-plate heat exchangers. The plate diameter is 215 mm and the chevron angles (β) are 30°, 45°, 60°, and 75°. Simulations are performed with Reynolds number ranging from 200 to 1000. The heat transfer and frictional performance are termed as Nusselt number (Nu) and friction factor (f), and results for both shell and plate side are reported. The Nusselt number and friction factor in the shell side are increased with the rise of chevron angle. For the same inlet flowrate, the pressure profile in the shell side changes significantly with the chevron angle, from uniform (β = 30°) to concave (β = 45°∼60°) and finally to slightly convex (β = 75°) while the pressure profile in the plate side is always convex. In the plate side, the Nusselt number increases with the rise of chevron angle. But the lowest friction factor occurs when β = 45° due to a better flow distribution. The heat transfer performance in the shell side is superior to the plate side due to the presence of the inlet/outlet manifold in association with the chevron angles. Based on the performance evaluation criteria, it is found that the best overall performance occurs at a chevron angle of 45°. This angle is applicable in both shell side and plate side. For the shell side, the index is about 25 %, 60 %, and 340 % higher than those of β = 75°, 60°, and 30°, respectively at a Reynolds number of 300 at the shell side. For the plate side, the index amid β = 75°, 60°, and 45° is roughly the same when the Reynolds number is lower than 500, and the index is about 220 % for β = 45° when compared to β = 30° at a Reynolds number of 300.

Gender identification of the horsehair crab, Erimacrus isenbeckii (Brandt, 1848), by image recognition with a deep neural network

Appearance-based gender identification of the horsehair crab [Erimacrus isenbeckii (Brandt, 1848)] is important for preventing indiscriminate fishing of female crabs. Although their gender is easily identified by visual observation of their abdomen because of a difference in the forms of their sex organs, most of the crabs settle with their shell side upward when placed on a floor, making visual gender identification difficult. Our objective is to use deep learning to identify the gender of the horsehair crab on the basis of images of their shell and abdomen sides. Deep learning was applied to a photograph of 60 males and 60 females captured in Funka Bay, Southern Hokkaido, Japan. The deep learning algorithms used the AlexNet, VGG-16, and ResNet-50 convolutional neural networks. The VGG-16 network achieved high accuracy. Heatmaps were enhanced near the forms of the sex organs in the abdomen side (F-1 measure: 98%). The bottom of the shell was enhanced in the heatmap of a male; by contrast, the upper part of the shell was enhanced in the heatmap of a female (F-1 measure: 95%). The image recognition of the shell side based on a deep learning algorithm enabled more precise gender identification than could be achieved by human-eye inspection.

Comparison of the use of different nanofluids for heat transfer from the outer surface of spiral tubes: Energy, exergy, and exergoeconomic (3E) analysis

Heat exchangers play a crucial role in industrial processes by facilitating the efficient transfer of thermal energy. The thermophysical properties of nanofluids, which consist of nanoparticles dispersed in conventional heat transfer fluids, are enhanced. Their remarkable thermal conductivity and convective heat transfer characteristics have the potential to significantly improve heat transfer processes. In the present investigation, a numerical study has been carried out to investigate the effect of different nanofluids on heat transfer from outer surface of a spiral coil based on the first and second laws of thermodynamics. The numerical solutions are checked against previous experimental and numerical research in the field. Nusselt number, Euler number, exergy efficiency, irreversibility, and equipment cost are studied with respect to concentration, mass flow ratio (Rm), and shell and tube inlet temperature for a variety of nanofluids, including Al2O3/H2O, CuO/H2O, Fe2O3/H2O, and TiO2/H2O. Compared to water, the exergy efficiency is lower while using nanofluids, as shown by the results, especially in higher nanofluid concentrations, and among the different nanofluids, Al2O3–H2O nanofluid was found to have the highest thermodynamics second law efficiency. The exergy destruction rate experiences linear growth by increasing the nanofluid concentration. A higher pressure drop based on the Euler number is expected for nanofluids. In addition, the consumption of nanofluids on the shell side results in a considerable reduction of the purchased equipment cost (PEC) value compared to water. As opposed to the tube-side input temperature, variations in the shell-side inlet temperature found to have a greater impact on the heat exchanger's exergetic performance.

Nelinearno ponašanje spremnika za ukapljeni prirodni plin s različitim sustavima potresne izolacije

This study determines the effects of different types of base isolator systems on the seismic performance of liquefied natural gas (LNG) storage tanks. Nonlinear time-history analyses of the non-isolated and three different isolated models were performed for the average acceleration of seven ground motions scaled to achieve a specified safe shutdown earthquake. The ANSYS Workbench program was used in the modelling studies of the LNG liquid, inner steel tank, outer shell, ring beam, roof and concrete foundation and side wall insulation. The LS-DYNA program was used for the nonlinear analyses of the LNG liquid, inner steel tank and concrete foundation. The results of the total base shear force, sloshing height, steel tank stresses and lateral deflection were compared. The results indicated that there was no difference between the convective and impulsive modes for the LNG tanks with isolators. It was concluded that the wave motion of the liquid was different from the oscillation of the structure and the earthquake isolation times did not affect the sloshing motion. In the non-isolated system, the stress reached 400 MPa, whereas it was 350 MPa on average in the LNG tanks with isolators.