Diameter Deviation Research Articles

Development of a repeatable single-droplet generator using a step motor and PWM control of a two-way solenoid valve

A device capable of repeatedly generating a single droplet was developed. A piston pushes the liquid into a cylinder, creating droplets that are emitted from the nozzle outlet. A one-dimensional linear stage connected to a stepper motor was used for piston displacement. To repeat the generation of single droplets, a method that consists of generating droplets, supplying liquid into the cylinder, and blocking the inflow of external air through the nozzle outlet during the process of supplying liquid into the cylinder was developed. To prevent the inflow of external air into the cylinder through the nozzle outlet, a two-way solenoid valve was installed in the supply passage between the cylinder and the reservoir holding the liquid supply. The sudden opening of the two-way solenoid valve is prevented by PWM (pulse width modulation) control of the current supplied to the solenoid, and the air inflow into the cylinder through the nozzle outlet can be successfully blocked by this method. PWM control of the driving current in the solenoid enabled the repeated generation of single droplets. A single-droplet-generation experiment was repeatedly conducted while varying the nozzle diameter and the hydraulic head difference h between the nozzle outlet and the liquid reservoir. The ratio of the droplet diameter to the nozzle diameter was 5.45 with a nozzle diameter of 0.23 mm and convergence to 2.1 with an increase in the nozzle diameter to 1.51 mm. When repeated measurements were taken under fixed experimental conditions, the droplet diameter deviation % (=stdev/average*100) showed a distribution of 1 ~ 6%.

Nomogram for predicting diabetes insipidus following endoscopic transsphenoidal surgery in pituitary adenomas.

Postoperative diabetes insipidus (DI) frequently complicates endoscopic transsphenoidal surgery (TSS) in pituitary adenoma (PA) patients, yet reliable predictive methods for DI risk remain lacking. This study aims to identify risk factors associated with DI following endoscopic transsphenoidal resection of PA and to develop a predictive nomogram for assessing postoperative DI risk. This study involved 600 PA patients underwent endoscopic TSS at Shandong Provincial Hospital from 2021 to 2023. Among these patients, 82 developed postoperative DI while 518 did not. The cohort was randomly divided into training (n = 360) and validation (n = 240) groups at 6:4 ratios by R software. Clinical parameters and radiographic features were evaluated using univariable and multivariable logistic regression to construct a predictive nomogram for post-endoscopic TSS DI risk. Model performance was assessed using ROC curves, calibration plots, and decision curve analysis. Subgroup analysis was used to evaluate the model's ability to discriminate between transient and permanent DI. Univariable and multivariable logistic regression analyses on the training group identified several independent risk factors for post-endoscopic TSS DI, including maximum tumor diameter, Knosp grade, Esposito grade, recurrent PA, and pituitary stalk deviation angle. A nomogram was developed based on these factors, demonstrating robust predictive accuracy with ROC areas under curve of 0.840 for the training group and 0.815 for the validation group. Calibration plots indicated excellent agreement between predicted and observed probabilities of postoperative DI. DCA curves highlighted the nomogram's efficacy in guiding clinical decision-making. Subgroup analysis showed that the model was able to discriminate between transient and permanent DI, and the AUC was 0.652 (95% CI 0.525-0.794). This study presents a nomogram designed to predict postoperative DI risk in patients undergoing endoscopic TSS for PA. Internal and external validations underscored the model's high accuracy, calibration, and clinical utility. Simultaneously, the model can also assess the development risk of permanent DI. This predictive tool offers clinicians valuable support in identifying high-risk DI patients, optimizing postoperative care strategies, and tailoring treatment plans to improve patient outcomes.

Influence of Cold-Rolling Processes on the Dimensional Accuracy and Roughness of Small-Diameter Thick-Walled Seamless Tubes

Cold pilgering is widely utilized in high-end applications for the precise shaping of seamless tubes due to its capacity for large deformation, which reduces the number of deformation processes and shortens production cycles. However, there is a gap in the research on the cold pilgering of small-diameter, thick-walled seamless tubes, specifically those with an outer diameter–wall thickness ratio of ≤3. In this study, cold pilgering tests were performed on Cr-Mo-V hot-working die steel small-diameter thick-walled tubes. It was discovered that increasing the feed rate results in greater deviations in both inner diameter and wall thickness, although it has little effect on inner wall roughness. In contrast, increasing wall thickness reduction leads to higher wall thickness deviation but reduces inner surface roughness without significantly affecting inner diameter deviation. The study also found that a decrease in the initial inner wall roughness before pilgering results in improved final roughness. Under optimal conditions, the average inner surface roughness Sa can reach 0.177 μm, and small-diameter thick-walled seamless tubes with deviations in the inner diameter and wall thickness of 0.05 mm and 0.03 mm, respectively, are obtained. After tempering at 600 °C, the tensile strength (Rm) and yield strength (Rp0.2) of the cold-pilgered tube reach 1092 MPa and 947 MPa, respectively, and the elongation (δ5%) and impact energy (AkU) increase to 20.4% and 61.5 J, respectively.

Dry powder inhaler deposition in the larynx and the risk of steroid inhaler laryngitis: A computational fluid dynamics study

Dry Powder Inhalers (DPIs) are a mainstay in the treatment of obstructive respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Deposition of inhaled corticosteroids in the larynx elicits local side effects, potentially leading to steroid inhaler laryngitis. The objective of this study was to estimate the dose of DPIs that are deposited in the larynx relative to other regions of the respiratory tract using computational fluid dynamics (CFD). An anatomically accurate model of the airways (mouth to main bronchi) was constructed based on medical imaging of a healthy adult. Respiratory airflow and particle transport were simulated for constant inhalation rates of 30, 45, and 60 L/min. Two turbulence models were compared, namely the large eddy simulation (LES) and the k−ωSST models. DPIs were assumed to generate an aerosol cloud with a log-normal particle size distribution characterized by the mass median aerodynamic diameter (d50) and geometric standard deviation (σg). We compared two commercial DPIs, namely DPI 1 had a large particle size (d50 = 50 μm, σg=2.55) and DPI 2 had a small particle size (d50 = 2 μm, σg=1.99). The laryngeal dose was 1.6-to-3.8-fold higher than the bronchial dose for DPI 1, while the laryngeal and bronchial doses (units of mass per unit surface area) were similar for DPI 2 for both turbulence models and all inhalation rates. The choice of turbulence model had little impact on the total extrathoracic deposition, but a significant impact on regional doses, with the LES model predicting higher larynx-to-bronchi relative doses than the k−ω model. Our prediction that the larynx is a hotspot for DPI deposition is consistent with the observation of laryngeal side effects in DPI users. Importantly, our simulations suggest that DPIs with larger particles (d50 = 50 μm) may increase the risk of steroid inhaler laryngitis.

Revisiting each fracture size and spatial pattern: Inference from rock mass surface to interior

Estimating fracture size is a fundamental aspect of rock engineering. However, determining the most probable diameter (MPD) from a fracture’s surface trace remains challenging in the scientific community. The prevailing methodologies typically infer statistical distributions of fracture sizes rather than specific values. This research presents a novel approach to inferring the MPD and the true spatial distribution pattern of each fracture. The challenge lies in linking the inference process with the trace length of each fracture and the statistical characteristics of the entire outcrop. Additionally, it is necessary to address the non-unique inverse problem. The methodology comprises several key steps. Firstly, the issue of censoring bias is addressed by considering the lengths of the traces contained. Secondly, the orientation bias is corrected using the vector method, and the true mean trace length and standard deviation are estimated and derived. Thirdly, assuming a lognormal distribution for fracture sizes, the mean and standard deviation of diameters are derived through a high-order moment relationship between trace lengths and diameters, validated by Crofton’s theorem. Finally, the MPDs of all trace samples are determined by relating MPDs to trace lengths and the standard deviation of diameters using stereology techniques. Furthermore, the true fracture spatial patterns are inverted based on spatial geometric relationships. The proposed methodology is validated through rigorous Monte Carlo simulation and applied in a practical engineering case study, demonstrating its potential for use in rock engineering applications.

Controlled Growth of Single-Walled Carbon Nanotube Films by Iron-assisted Floating Solid Catalyst Chemical Vapor Deposition.

Single-walled carbon nanotube (SWNT) films, with exciting electronic properties are increasingly important for next-generation technologies. Here, an Iron-assisted floating solid catalyst chemical vapor deposition (IA-FSCCVD) method is developed for the controlled growth of high-quality and high-purity SWNT films. Titanium carbide nanoparticles with a high melting point are used as the solid catalysts, which provide a stable template for SWNT growth through the perpendicular growth mode. Trace amounts of iron are introduced to increase the efficiency of SWNT growth. Gas chromatography measurements and density functional theory show that the gas-phase iron acts as a pre-cracking assistance for the carbon source, promoting the growth of SWNTs. Carbon nanotube films with a high quality (average IG/ID = 166) are successfully prepared, a small diameter deviation (mean diameter of 1.6nm), and a high content of SWNTs (97%) using the IA-FSCCVD platform. This work provides a powerful way to prepare the carbon nanotube aggregates with a controlled structure.

Assessment of keyhole stability in laser beam welding with external magnetic field using numerical simulation

The challenge of understanding the physical mechanisms behind porosity reduction by a magnetic field during laser beam welding (LBW) is partly due to the difficulty in quantitatively evaluating keyhole stability. The commonly used index, such as keyhole depth, is typically one-dimensional, which is insufficient to capture the dynamic and three-dimensional fluctuations of the keyhole. In this paper, by utilizing a 3D multiphysical model of LBW with magnetic field, a novel keyhole geometry reconstruction algorithm has been developed to describe the keyhole profile and its fluctuation in a statistical manner to evaluate keyhole stability quantitatively. An equivalent diameter is proposed in this algorithm to reduce the irregularity of the keyhole geometry. The calculation results indicate that the time-averaged keyhole shape over 300 ms in the LBW of steel is conical, regardless of the application of an external magnetic field, which provides a more representative shape. Meanwhile, it is observed from the statistical aspect that the keyhole diameter becomes smaller, except the top part, under the influence of the magnetic field. The standard deviation of the equivalent diameter can be used as a physical variable to assess the keyhole stability quantitatively. The application of an external magnetic field can produce a noticeable reduction of the standard deviation of the equivalent diameter, namely, stabilizing the keyhole during LBW of steel. However, the different contribution from the keyhole stability affected by a magnetic field in suppressing porosity is different with materials.

Rigorous design and economic optimization of reactive distillation column considering real liquid hold-up and hydraulic conditions of industrial device

The liquid hold-up in a reactive distillation (RD) column not only has a significant impact on the extent of reactions, but also affects the pressure drop and hydraulic conditions in the column. Therefore, the liquid hold-up would be a critical design factor for RD columns. However, the existing design methods for RD columns typically neglect the influence of considerable amount of liquid hold-up in downcomers owing to the difficulties of solving a large-scale nonlinear model system by considering downcomer hydraulics, resulting in significant deviations from actual situation and even operation infeasibility of the designed column. In this paper, a pseudo-transient (PT) RD model based on equilibrium model considering tray hydraulics was established for rigorous simulation and optimization of RD plate columns considering the liquid hold-up both in downcomers and column trays, and a steady-state optimization algorithm assisted by the PT model was adopted to robustly solve the optimization problem. The optimization results of either ethylene glycol RD or methyl acetate RD demonstrated that assuming all the liquid hold-up of a stage belonged to the tray will cause significant deviations in the column diameter, weir height, and the number of stages, which leads to not meeting the separation requirements and even operation hydraulic infeasibility. The rigorous model proposed in this study which considers the liquid hold-up both on trays and in downcomers as well as hydraulic constraints can be applied to systematically design industrial RD plate columns to simultaneously obtain optimal operating variables and equipment structure variables.

Control and Modelling of Laser Shock Peening without Coating (LSPwC) Texture of AISI 9310 Steel.

LSPwC is an important development of Laser shock peening (LSP) technology, and surface texturing is an effective method to improve tribological properties. The combination of these is expected to innovate a new surface texturing technology with a strengthing effect, but no one has attempted it. In this paper, a new LSPTwC technology combining them is innovatively proposed and validated on AISI 9310 steel, which is commonly used in helicopter transmission components for surface texturing. The LSPTwC surface was studied using an optical microscope, electron microscope, energy dispersive spectrometer, and so on. The results proved that LSPTwC is an effective texturing method of AISI 9310 steel, which modulates the texture and improves the properties, such as the microhardness increased by more than 10%. A model for calculating the texture and process parameters is also constructed on a statistical basis, and a modeling method for textured surfaces is proposed. It is verified that the calculation results and the constructed model are highly consistent with the test, with a diameter deviation <3% and depth deviation <4%. The above results can provide the experimental basis, process design method, and calculation model for single-point LSPwC texturing of AISI 9310 steel parts for helicopters, which have application value.

One‐Step Fabrication of Nanofiber/Nanosphere Composite Membranes by Airflow/Electrostatic Method

A fabrication technology and equipment for nanofiber/nanosphere composite membranes (NNCMs) is proposed and named as the airflow/electrostatic method (AEM). AEM uses both air flow and induced electric field to stretch the jets. The AEM working mechanisms are proposed and verified. The electric field laws of AEM are obtained by finite‐element simulation and theoretical deduction. Compared with the airflow method (AM), the average fiber diameter, standard deviation of fiber diameter, and NNCMs, porosity of AEM can be reduced by 38.8%, 71.1%, and 87.3%, respectively. AEM can also overcome the shortcoming of the AM that cannot receive nanospheres. Compared with the electrostatic method (EM), AEM can not only fabricate NNCMs with randomly distributed nanofibers and nanospheres in one step, but also greatly improve the yield. The injection speeds of solution X and solution Y of AEM can be increased by 24 000% and 1920%, respectively, compared with that of EM. The diameters of AEM nanospheres and nanofibers increase with the increase of injection speed of solution X and solution Y, respectively. The distance between needle and receiver has little effect on the diameters of nanofibers and nanospheres. AEM NNCMs with excellent quality and high yield will be widely used in many fields.

Effect of drill gash rake angle on drillability in plain carbon and low alloy steels

In this study, the effects of the gash rake angle (γa), which is an important component of the drill geometry, on the thrust force and drilling torque occurring in the drilling of ordinary carbon steels (AISI 4140 and Ck 45) were examined through experimental and FEM-supported numerical simulation studies on surface roughness, tool surface roughness, wear and diameter deviation values were investigated experimentally. In the experiments, 6.8 mm diameter solid cementite carbide, coated and internal cooling channel drills with +10°, 0°, −10° gash rake angle were used. Three different feed rates and cutting speed levels were selected as cutting parameters. Determination of material-specific gash rake angle and cutting parameters for different materials was carried out by Taguchi-assisted variance analysis of experimental data. In experimental studies, the gash rake angle was 65.9% effective on the thrust force for AISI 4140 tempered steel, while it was the second effective parameter with 29.22% for Ck 45 manufacturing steel. While the feed rate is the more effective parameter in the drilling moments that occur when drilling different materials, it has been observed that γa also has a significant effect. It has been determined that chisel edge wear, main cutting edge wear and crater wear occur in the drill when drilling AISI 4140 tempered steel and Ck 45 manufacturing steel. The data obtained from the finite element-assisted chip removal analyses support the experimental results and provide guiding results in the selection of material-specific gash rake angle.

TG Vascutrack: A User-Friendly and Open-Source Software for Automated Extraction of Arterial Diameter and Velocity Profile Data From Vascular Ultrasound Videos.

Existing automated software for vascular ultrasound data extraction lacks free, open-source options suitable for professionals without coding experience. These programs typically include signal-cleaning algorithms, resulting in processed output without access to raw data. To address these needs, we developed TG Vascutrack, an open-source and user-friendly software tailored for non-coder professionals. It features a graphical interface, multiple functionalities, and provides access to raw data. Comparative analysis against validated software and manual extraction revealed minimal biases and standard deviations in diameter and velocity measurements. TG Vascutrack offers a free, promising solution for non-coders needing automated vascular ultrasound data extraction.

Evaluation of wear and friction properties of graphite modified Lubri polylactic acid with various infill fabricated by additive manufacturing techniques

AbstractThree‐dimension (3D) printing technology, also known as additive manufacturing, is a manufacturing technology that creates three‐dimensional objects by depositing material layer by layer, as opposed to subtractive manufacturing methods. However, the newness of the technology brings with it many unknowns. In particular, the raw materials used are constantly increasing. For this reason, testing each raw material used in many aspects and to determine the optimum production conditions is important for the wide use of 3D printing technology. These optimal conditions may be the parameters used to produce a material, and sometimes they can appear as a new material. In addition, the production of new materials with varying production parameters is fundamental research topic that requires comprehensive study. For all these purposes, in this study, a new material type known as Lubri PLA (LPLA) was selected and produced in different filling types and subjected to a series of friction and wear tests. Thus, it is aimed to determine the tribological properties of the material. Additionally, samples were produced in ten different infill types (grid, lines, triangels, hexagon, cubic, octal, zigzag, diagonal, diagonal 3D and gyroid) to show the effect of filler type on friction and wear behavior. These filler types were used for both PLA and Lubri PLA materials and a total of twenty samples were produced. Thereby, it is aimed to conduct a comprehensive study showing the effect of both material difference and filling type on friction‐wear behavior. Diameter deviations, hardness deviations, friction coefficient, temperature, specific wear rates (SWr), and vibration were selected as output parameters. According to the analysis of the test results, the best result in terms of material structure was given by Lubri PLA, while the best result in terms of filling type was obtained with Diagonal 3D filling type. In addition, the lowest vibration level was obtained in the LP‐Diagonal 3D sample with 0.041 mm/s2, while the highest vibration level was obtained in the P‐Grid sample with 1.756 mm/s2.Highlights LPLA closed to nominal value in diameter and hardness deviations Addition of graphite nanoparticle increased the dimensional accuracy Diagonal 3D infill type Lubri PLA composites showed the superior performance Graphite modified Lubri PLA composites demonstrated superior performance

Development of Synthetic Lumbar Vertebrae using Custom-made Mould for Orthopaedics Training: Micro-Structural Analysis

Human vertebrae composed of cortical and cancellous bone are crucial to provide the structural support of human framework and protect the organs underneath. Vertebrae from the Lumbar 3 (L3) was selected for fabrication because it is the most commonly used for surgical training. The use of human vertebrae in the orthopaedic studies is necessary to investigate various complications such as vertebral compression fracture and to propose the most suitable medical intervention for the treatment. However, investigations of cortical and cancellous material properties and composition have been limited. Therefore, the main objective of this study was to design a custom-made mould for synthetic lumbar vertebrae using moulding techniques that could exhibit the same anatomical structure as real vertebrae. Then, this study was carried out to establish a process of cortical and cancellous synthetic bone development. Lastly, this study was done to compare the morphological properties of synthetic bone produced with human bone. Utilizing Polyurethane (PU) as the main material was used for the fabrication, where it could inhibit the morphological properties that could mimic the human bone. The methods to fabricate the vertebrae also varied from static mould and rotational mould. The fabricated lumbar produced was tested for the morphological properties, targeting the pore diameter, was performed using Scanning Electron Microscopy (SEM). From this study, it was identified that the analysis of pore diameter from specimen of Ratio 3 from rotational mould depicts the smallest pore diameter and standard deviation, 1.5 ± 0.3 mm. While this specimen has the smallest value, the results were still higher when compared to the pore diameter of human trabecular bone (which ranges from 0.3 mm to 0.6 mm). In conclusion, the use of silicone custom-made moulds could provide synthetic vertebrae with an anatomical structure mimicking real human vertebrae.

Measurement of outer diameter parameters of manual grinding cable joints based on 3D point cloud processing

For the problems associated with low measurement accuracy caused by surface shrinkage, uneven grinding, and irregular shapes in manual grinding cable joints, as well as the limitations of existing machine vision measurement techniques for the outer diameter parameters, this paper proposes a non-contact outer diameter parameters measurement method of manual grinding cable joints based on three-dimensional (3D) point cloud processing. Firstly, statistical filtering is used to remove discrete noise, and coordinate transformation preprocessing is conducted to ordered the point cloud. Secondly, a bidirectional point cloud slicing method is proposed based on the cable joint structure and point cloud distribution to preserve the original features for effective measurement. Subsequently, the normalized mean curvature is utilized as the weight of point cloud coordinate averaging to construct key points for surface slices, which reduces the amount of data in the sliced point cloud and improves the matching efficiency. Finally, the key points are matched according to the position of the surface slices, and the distance of point pairs is calculated to complete the measurement of the outer diameter parameters. Experiments and error analysis are conducted on multiple manual grinding 110 kV and 500 kV real cable joints. The absolute error in the measurement of the outer diameter is less than 0.2 mm, with a relative error within 1 %. The absolute error of the XY-axis outer diameter deviation is less than 0.1 mm. The experiments demonstrate that the proposed method exhibits superior performance in cable joint outer diameter measurement.

Three-Dimensional-Scanning of Pipe Inner Walls Based on Line Laser.

In this study, an innovative laser 3D-scanning technology is proposed to scan pipe inner walls in order to solve the problems of the exorbitant expenses and operational complexities of the current equipment for the 3D data acquisition of the pipe inner wall, and the difficulty of both the efficiency and accuracy of traditional light stripe-center extraction methods. The core of this technology is the monocular-structured light 3D scanner, the image processing strategy based on tracking speckles, and the improved gray barycenter method. The experimental results demonstrate a 52% reduction in the average standard error of the improved gray barycenter method when compared to the traditional gray barycenter method, along with an 83% decrease in the operation time when compared to the Steger method. In addition, the size data of the inner wall of the pipe obtained using this technology is accurate, and the average deviation of the inner diameter and length of the pipe is less than 0.13 mm and 0.41 mm, respectively. In general, it not only reduces the cost, but also ensures high efficiency and high precision, providing a new and efficient method for the 3D data acquisition of the inner wall of the pipe.

A Novel image processing technique for weighted particle size distribution assessment

The objective of the study was to create a reliable method that could be used to evaluate the particle size distribution of samples and pre-mixes in real-world situations, particularly those consisting of typical formulation blends. The goal was to use this method to assess the uniformity of the samples and ensure that they met the required quality standards. The researchers aimed to create a method that could be easily incorporated into the manufacturing process, providing a practical and efficient solution. This study demonstrates the use of ImageJ software to analyze the particle size distribution (PSD) of powders. The technique produces qualitative data from microscopy images and quantitative data from analysis of parameters including average diameter, D 10, D 50 , D 90, and standard deviation. The method was tested with various treatments, showing differentiating outcomes in all cases. The alternate technique provides a rapid and cost-effective method for PSD analysis, surpassing the limitations of sieve analysis. Extensive testing of the method, using a variety of sample types, including typical formulation blends, was performed. The results suggest that the method can effectively assess the morphology of changing materials during batch manufacturing and characterize uniformity in blends. The methodology has the capability to identify attributes related to PSD that are typically required to be monitored during manufacturing. The technique allows for accurate and reliable quantification of the attributes through image capture technology. The technique has future potential and has important implications for material science, powder rheology, pharmaceutical formulation development, and continual process monitoring.

STAR-CCM+ simulation of debris bed formation in the unheated DEFCON-S experiment

In a severe accident of light-water reactor, molten corium can be formed and discharged into the reactor cavity. If the resulting debris bed is not adequately cooled, it could threaten the containment integrity by causing a molten core-concrete interaction. This study analyzes a non-heating debris bed formation experiment of DEFCON-S using the STAR-CCM+ code. Relevant CFD models are established to reflect the interaction between particles and fluids to describe the particle behavior and flow of fluids. The shape and size of debris bed are predicted through the CFD calculation. The rolling resistance becomes an important parameter in this simulation. The prediction with the default values of STAR-CCM+ forms a spread shape of particle bed compared to the experimental result. The shape of debris bed obtained with modified rolling resistance coefficients gives consistency with the DEFCON-S experiment, having a deviation in diameter of 4.6 % and a deviation in height of 3.8 %.

Experimental investigation on fiber laser micro drilling of Titanium grade 5: fabrication, nature-inspired optimization and analysis through image processing

This investigation showed that micro holes were created on Titanium grade 5 substrate surface using a 30 W fiber laser. The impact of the control factors such as scan speed, frequency, number of passes and power were studied on the responses namely heat affected zone (HAZ), hole circularity (HC) and deviation in diameter (DIV). The control factors were optimized using firefly algorithm. Mathematical models were developed for each response having significant R-square value. 3D surface plots were used to examine how the control parameters affected the response. The firefly algorithm identifies the optimal conditions for micro drilling as scan speed of 210 mm s−1, frequency of 40 kHz, power of 8 W and total of 40 passes which improved experimental findings i.e. HC-0.974, DIV-37.02 μm and HAZ-19.53. After comparing the predicted values with the experimental findings, it was observed that the prediction error is lowest for HC (1.23%) followed by DIV (13.9%) and HAZ (16.9%). Image processing technique was used to convert regular images into a digital format to extract useful information.

A novel type of additively manufactured high pressure mini-channel heat exchanger for precooling in hydrogen refueling stations

During refueling supercritical hydrogen into high pressure storage tanks, the fluid has to be cooled down to temperatures between -33°C and -40°C before entering the vehicle fuel tank. This cooling takes place while the hydrogen is at a pressure of up to 87.5 MPa. The requirements for the heat exchanger performing this task are very high. It has to be pressure resistant, compact enough to fit in the dispenser column and provide a high thermal performance to ensure a fast refueling with high mass flow rates. Only few conventional manufactured heat exchangers are able to fulfil these requirements. With the rise of additive manufacturing technology, especially laser powder bed fusion, new heat exchangers produced without use of conventional joining technologies can be realized. This manuscript presents a new type additively manufactured of mini-channel heat exchanger. It is developed in a joint research project involving the Leibniz University Hanover and an industrial heat exchanger manufacturer. The apparatus has a design pressure of 105 MPa and will be suited to be used in hydrogen refueling stations. The thermal requirements and the design of the apparatus are described. Thermal power and pressure drop for the full-size heat exchanger are calculated via a cell model. Scaled smaller heat exchangers made of 1.4404 stainless steel are additively manufactured via laser powder bed fusion (LPBF). The thermofluiddynamical performance of the scaled apparatus is measured in a testbench to verify the applicability of the used correlations. Deviations in hydraulic diameter and surface roughness are taken into account. Existing correlations are fitted to the new geometry.