Fill Ratio Research Articles

Numerical Investigations of a Single Loop Pulsating Heat Pipe for Cryogenic Applications

Abstract The thermohydraulics of a single-loop pulsating heat pipe (PHP) for cryogenic applications have been simulated. The 120 mm long PHP tube is made of a 1.5 mm diameter inner tube of thickness 0.83 mm. The CFD analysis performed with the ANSYS Fluent software is a two-dimensional numerical study using pure nitrogen as the working fluid in binary phases. The boundary condition on the evaporator is of constant heat flux, while the same on the condenser is of constant temperature. The phase behaviour of the liquid and vapour and their interactions are accounted for through the volume of fluid (VOF) method and the Lee model. The numerical model is validated using the existing experimental data, with an agreement of less than 8% between them. The thermo-hydraulic variations of temperature, pressure, and velocity are simulated for different heat loads and fractional liquid contents (fill ratios). The temperature and pressure oscillations set in the PHP-fluid increase with the heat added to the evaporator while the fluid velocity remains independent. The heat load and the fill ratio dictate the effective thermal conductivity - attaining nearly 3400 W/mK for a fill ratio of 70% in the chosen PHP geometry. An alteration has been made in the Jacob number to predict the dominance of sensible heat over latent heat in a PHP, postulated by other researchers. The constant fill ratio assumption is not truly valid as it indicates a small yet finite variation with the change in the heat load.

Intensified microalgae production and development of microbial communities on suspended carriers and municipal wastewater

Wastewater represents an alternative source of nutrients in which to grow microalgae, whilst improving the quality of the wastewater, and reducing the downstream treatment required. However, commercialisation of microalgal cultures for such duties faces a number of challenges, predominantly high cost and low productivity. Suspended-solid reactors (ssPBR) can reduce the operational costs, while promoting attached and suspended microalgae growth. In the present study, a novel approach was developed by integrating microalgal wastewater treatment with carrier systems to favour the growth of both attached and suspended cells of T. obliquus. This study found that T. obliquus was able to uptake nutrients from municipal wastewater, achieving removals of 99.3–99.9 % NH3-N, 54.5–88.5 % PO43− and 92.8–94.5 % DTC. The addition of a 12.5 % volumetric fill ratio of carriers in ssPBRs produced higher microalgal cell productivity (1.2·106 ± 2.5·105 cell ml−1 d−1) than the control (4.3·105 ± 2.8·105 cell ml−1 d−1). MinION nanopore sequencing was conducted to assess the impact of microalgal and carrier treatment on wastewater bacterial communities. It was found not only that bacterial communities had changed after the treatment but also the ones attached differed from the ones suspended. Untreated wastewater was characterised by the abundance of sewer bacteria genera such as Aliarcobacter and Arcobacter, whilst, after treatment, microbial communities were characterised by the presence of photosynthetic freshwater (Limnococcus, Stanieria) and bioremediation-like bacteria genera (Pseudomonas, Rheinheimera). In conclusion, the addition of 12.5 % fill carrier ratio increased microalgal productivity, while stimulating changes in the algal microbiome, and creating distinctly different populations in the free and attached environments.

Thermal performance of a novel hybrid heat pipe with composite heat transfer characteristics

Considering the capillary threshold of oscillating heat pipes (OHP), a novel hybrid heat pipe (HHP) was designed with channels with hydraulic diameters that alternately exceed and fall below this threshold, parallelly arrayed within a unified copper substrate. This technology attains a comprehensive heat transfer performance within the HHP, seamlessly transitioning from pure phase change heat transfer to hybrid pulsating flow heat transfer to effectively accommodate the escalating demands of heat load. Performance and visualization are used to analyze the operational characteristics of HHP. The results indicate that the HHP mainly transfers heat through the phase change in the large channels in lower heat input, while the working fluid in the small channels remains calm. Once the heat input is sufficient, the geyser boiling in the large channels and the liquid slug pulsating in the small channels jointly carry out heat transfer. Furthermore, the liquid content in the large and small channels can be adaptively adjusted to each other. The high-speed liquid in the small channels can be squeezed into the large channels to ensure the sufficient pulsating space and achieve efficient heat transfer under high heat input. In addition, the operation of the HHP can be significantly impacted by the filling ratio (FR). In the phase change stage, the FR of 47.6 % can be considered as the turning point. After transitioning to the hybrid pulsating flow stage, the HHP with low FR can get a better performance. This new type of heat pipe with gradually changing operation characteristics may be critical to solve thermal problems in variable heat load domain.

Lignin dispersion in polybutadiene rubber (BR) with different mixing parameters

There is a strong need to replace carbon black and silica as a reinforcing filler in rubber industry. Lignin is a promising option as a replacement, because of its wide availability, complex chemistry and sustainable source. Typically, the reinforcing effect of lignin is weak and one major cause is the poor dispersion of filler. In this study, typical dispersion parameters in mixing are tested in a systematic way to validate their effect on kraft lignin dispersion in polybutadiene rubber. Tested mixing variables are temperature, rotor speed, mixing time, fill ratio and shear forces. The effect of variables to dispersion are analyzed from electron microscopy images with an image analysis software. With this novel method exact number of particles and their properties could be calculated. Unlike for conventional fillers (carbon black and silica), the results show clearly that only the mixing temperature has an effect on lignin dispersion in rubber. With high mixing temperatures, dispersion and hence mechanical properties improved. The better dispersion is especially seen as decreasing number of large (>Ø 5 μm) particles. Other mixing variables did not have significant effect on dispersion and the number of large particles.

Enhancement of 3D‐printability of zucchini puree by rice flour addition

SummaryThis study explored the feasibility of 3D food printing with zucchini puree‐rice flour mixtures, focussing on factors impacting print quality for home‐based applications. The effects of printing variables, including fill ratio (25%, 50%, 75% and 100%) and printing bed temperature (65 °C, 75 °C and 85 °C), were assessed on the print quality of the samples, along with rice flour ratio and a freeze‐thaw step commonly employed by general consumers. Increasing rice flour content enhanced water retention, leading to improved printability in terms of shape retention and dimensional accuracy. Higher printing surface temperatures promoted starch gelation in the initial layers, resulting in better shape retention and improved print scores at moderate rice flour ratios. The highest print quality, determined by dimensional accuracy and visual observations, was achieved with a rice flour puree ratio of 5:10, printed at a 100% infill ratio and 85°C printing bed temperature. While freeze‐thawing the mixtures preserved printability, it weakened the structure, leading to increased syneresis and spreading. Cooking fresh samples at 170 °C for 20 min after printing caused surface cracks, whereas freeze‐thawed samples retained their smooth surface. Further research is needed to optimise printing parameters, considering typical preparation steps that may be applied to vegetable flour mixtures before and after 3D printing.

Comparison of the effects on heat transfer through oil oscillation in a steel piston cooling gallery: Friction welding versus laser welding

Piston cooling gallery plays a critical role in managing the temperature of the piston and its performance. This paper aims to study the effect of oscillatory heat transfer within the cooling galleries, focusing on two distinct types: flanged (friction-welded) and smooth structures (laser-welded). To do so, the Eulerian multiphase flow model and the k-ω SST turbulence model were used to simulate the oil and air flow through the cooling gallery. Key parameters such as the oil filling rate, wall heat transfer coefficient, oil outlet flow rate, heat removal rate by the oil, and overall wall heat transfer rate were assessed for both gallery designs at an engine speed of 1800 r/min. The results indicate significant disparities between the two cooling gallery structures: the smooth structure exhibits an oil filling rate that is 5.41% higher and an oil outlet flow rate that is 33.48% greater compared to the flanged structure. The flange structure impedes internal oil movement, which leads to boundary layer separation, secondary wall contact, and the emergence of a double vortex phenomena. Collectively, these factors influence the oil fill ratio. This, in turn, affects the distribution of oil within the gallery and, subsequently, the efficiency of heat transfer. Comparative analyses of heat transfer within both galleries, under the same studied conditions, revealed that the smooth structure outperforms the flanged one. However, the presence of a flange significantly alters the heat contribution from different walls, thereby highlighting the substantial impact of flanges on the overall efficiency of heat transfer.

Optimization of process parameters for Trifolium pratense L. seed granulation coating using GA-BP neural network

Regarding the issue of low granulation qualification rates during the granulation coating of red clover seeds, this study theoretically analyzed the force conditions of seeds and powder particles under the action of liquid to obtain the main factors affecting seed coating quality. During the seed granulation coating process, an intermittent powder supply method combined with continuous liquid supply was utilized to control the ratio of powder to liquid. Using the granulation qualification rate as the evaluation index, single-factor experiments were conducted to investigate the effects of coating pan fill ratio, single powder supply amount, powder supply interval, and liquid supply amount on the quality of red clover seed granulation coating. Based on the results of the single-factor experiments, orthogonal experiments were conducted, revealing that the interaction of factors would influence the experimental results. To further optimize the quality of seed granulation coating, the mechanisms of powder and liquid in the adhesion process on granulation coating were explored. Orthogonal experiments were conducted on the process parameters of the granulation coating machine, and the GA-BP model was employed for optimization and solution. The optimal process parameter combination obtained was a coating pan fill ratio of 33.78 %, a single powder supply amount of 5.17 g, a powder supply interval of 7.7 s, and a liquid supply amount of 0.42 mL/s. Under this optimal parameter combination, granulation coating experiments with red clover seeds were performed, and the seed granulation coating quality was relatively high, with a granulation qualification rate of 97.7 %. The research results can provide a reference for optimization experiments on coating irregular seeds.

Experimental investigation on the thermal performance of high temperature two-phase loop thermosyphon

High-temperature two-phase loop thermosyphons (TPLTs) have the potential to be applied in high-temperature thermochemical conversions, concentrated solar energy, and nuclear energy. However, there has been limited investigation on the thermal performance of TPLTs so far. This work experimentally examines the thermal performance of TPLTs using alkali metals (NaK alloy and pure Na) as working fluids, aiming for internal energy recovery of a double-riser reactor. The effects of filling ratios (FRs), heating temperature, and altitude difference between the evaporator and condenser are investigated regarding start-up characteristics and steady-state performance. The experimental results show that the TPLT with NaK as the working fluid can successfully complete the start-up when the heating temperature is set to above 650 °C under the test conditions. However, the TPLT using pure Na as the working fluid can't successfully complete the start-up from a frozen state without a preheating operation. According to the variations in thermal resistance, an FR of 38% in the TPLT allows for the best heat-transfer performance under steady state when compared to the conditions that FRs are equal to 25% and 50%. Additionally, placing the condenser slightly higher than the evaporator is beneficial for improving the steady-state performance. However, if the condenser is lower than the evaporator, its steady-state performance is remarkably degraded.

Comparative predictive analysis using ANN and RCA for experimental investigation on branched and conventional micro heat pipe

The demand for compact, high-performance electronic devices rises, making thermal management in limited space crucial. This study presents a novel branched micro heat pipe (MHP) to solve this pressing problem. This novel method improves thermal performance for small-scale electronic cooling applications, surpassing conventional cooling methods. Innovative design has branched condenser of 12.7 mm evaporator, 24.6 mm adiabatic section and 12.7 mm condenser, each, compared to conventional MHP of identical size. Investigation encompasses a study of various parameters including working fluids, wettability characteristics, fill ratio, heat input, and cross-sectional geometries. The significant improvement in thermal performance by applying a hydrophobic surface treatment to the condenser section, increasing capillary force and condensate transport. Ammonia and de-ionized water excel thermal performance at lower and higher applied heat input (Qh), respectively. At higher Qh (>2 W), ammonia and toluene in the conventional MHP experience faster drying compared to the branched MHP, especially for lower fill ratio (0.6 FR). The branched MHP outperforms the conventional MHP, showing improved fluid circulation and performance, for fill ratios ranging from 0.65 to 0.4 and effectively transporting maximum heat flux in range of 10–14.4 W/cm2 with square mono-grooved MHP exhibits inferior performance compared to the trapezoidal and triangular mono-grooved. To provide a framework for future studies, we establish an artificial neural network (ANN) and statistical prediction model of thermal performance using the non-dimensional Kutateladze number (Ku), showcasing a robust correlation with experimental results and demonstrating only a minor deviation of ± 3 %.

Damage analysis of solid propellants with default defects based on macro-microscopic approach

Solid Rocket Motors (SRMs) rely on solid propellants, directly impacting the energy capacity of launch vehicles. High energy density material (HEDM) propellant exhibits superior energy density owing to the incorporation of a substantial quantity of energetic particles. However, the elevated particle fill ratio makes the formation of pores more prevalent during the manufacturing process of propellants. These pores, representing default defects, are indispensable factors in the investigation of mechanical properties of propellants. This study investigated default defects effects on HEDM propellants, analyzing both microscopic and macroscopic perspectives. Utilizing micro-CT imaging, the microstructure and default defects were characterized. Subsequently, using the cohesive zone model (CZM), microscopic damage evolution was depicted with the representative volume element (RVE) model, allowing in-depth analysis. Furthermore, a damage constitutive model, based on microscopic damage, was developed, with its softening function calibrated using microscopic damage evolution characteristics. Implemented into ABAQUS via user-defined material subroutine (UMAT), this model enabled the prediction of the mechanical response of HEDM propellants with different defects. The results demonstrate that the developed model accurately predicts the mechanical responses of HEDM propellants with different defects, showcasing the potential of macro-microscopic approaches in analyzing propellants with default defects.

Et3Al and Et2Zn cooperatively enhanced Ti catalyzed ethylene coordinative chain transfer polymerization

Developing olefin polymerization catalytic systems for both high activity and high chain transfer efficiency by using coordinative chain transfer polymerization (CCTP) is critical for the controlled synthesis of various novel high-value polyolefin materials. While the limited choice of chain transfer agents (CTAs) makes it a challenge to achieve highly efficient CCTP as well as chain propagation due to their competition during the polymerization. Here we report using the combination of R3Al and R2Zn in equal amount for tetradentate amine-bis(phenolate) Ti complex and tridentate ketoiminate Ti complex catalyzed ethylene polymerization and observed significantly enhanced CCTP catalytic performance in terms of activity, chains/cat, fill ratio, and kct/kp vs. using R3Al as CTA. The role of R3Al and R2Zn during ethylene polymerization were probed by preliminary control experiments studies and a possible mechanistic scenario was proposed.

An experimental study on flow behaviour of pharmaceutical powders during suction filling

Die filling is a crucial step in the pharmaceutical tablet manufacturing process. For industrial-scale production using rotary presses, suction filling is typically employed due to its significant efficiency advantages over gravity filling. Despite its widespread use, our understanding of the suction filling process remains limited. Specifically, there is insufficient comprehension of how filling performance is influenced by factors such as suction velocity, filling velocity, and the properties of the powder materials. Building on our previous research, this study aims to further investigate the effects of powder properties and process parameters (e.g., filling velocity, suction velocity, fill depth) on suction filling behaviour. A systematic experimental investigation was conducted using a model suction filling system, considering both cohesive and free-flowing pharmaceutical powders. The effect of fill depth on suction filling of these powders was examined at different filling and suction velocities. The results demonstrate that two distinctive flow regimes for suction filling can be identified: slow filling and fast filling. These regimes are delineated by a critical filling-to-suction velocity ratio. In the slow filling regime, the filling-to-suction velocity ratio is lower than the critical ratio, meaning that the filling phase is slower than the suction phase. Conversely, the fast filling regime occurs when the filling-to-suction velocity ratio exceeds the critical ratio, implying that the filling phase is faster than the suction phase. This study reveals, for the first time, that when the powder flow pattern during suction filling is dominated by plug flow, full die fill (i.e., the fill ratio equals unity) is achieved in the slow filling regime. However, in the fast filling regime, incomplete die fill is obtained. It is also found that when plug flow prevails during fast filling, the fill ratio has an inverse correlation with the filling-to-suction velocity ratio. This study further reveals that when the plug flow assumption is valid, the filling ratio at various fill-to-suction velocity ratios can be well predicted mathematically. Furthermore, it is also found that once the powder flow pattern differs from the ideal plug flow, which could be induced by the filling conditions and powder cohesion, the fill ratio can be overpredicted.

Determining the Optimal Intramedullary Screw Canal Fill Ratio in Length Unstable Metacarpal Fractures: A Biomechanical Investigation

Intramedullary (IM) screw fixation is gaining popularity in the treatment of metacarpal fractures. Despite its rapid adoption, there is a paucity of evidence regarding parameters to optimize effectiveness. This study aimed to quantify the relationship between stability, IM screw size, and canal fill using a cadaveric model. Thirty cadaveric metacarpals (14 index, 13 middle, and three ring fingers; mean age: 58.3 years, range: 48-70) were selected to allow for canal fill ratios of 0.7-1.1 for screws sized 3.0, 3.5, and 4.5 mm. Metacarpals underwent a 45° volar-dorsal osteotomy at the midpoint before fixation with an IM screw. Specimens were subjected to 100 cycles of loading at 10 N, 20 N, and 30 N before load-to-failure testing. Correlation coefficients for angular displacement on the final cycle at each load, peak load to failure, and average stiffness were assessed. Correlation coefficients for the angular displacement on the 100th cycle were as follows: 10 N, R= 0.62, 20 N, R= 0.57, and 30N, R= 0.58. Correlation values for peak load to failure as a function of canal fit were as follows: 3.0 mm, R= 0.5, 3.5 mm, R= 0.17, and 4.5 mm, R= 0.44. The canal fill ratio that intersected the line-of-best fit at an angular deformity of 10° was 0.74. Average peak forces for 3.0-, 3.5-, and 4.5-mm screws were 79.5, 136.5, and 179.6 N, respectively. Average stiffness for each caliber was 14.8, 33.4, and 52.3 N/mm. Increasing screw diameter and IM fill resulted in more stable fixation, but marginal gains were seen in ratios >0.9. A minimum fill ratio of 0.74 was sufficient to withstand forces of early active motion with angular deformity <10°. An understanding of the relationship of IM fill ratio of metacarpal screws to fracture stability may provide a framework for clinicians to optimally size these implants.

Investigation on the thermal performance of a dual driving force heat pipe under different working modes for thermal storage enhancement application

An embedded heat pipe (HP) with dual driving forces for compact and efficient thermal storage application was designed in this paper. To understand the thermal performance of the dual driving force heat pipe (DDFHP) under different heat storage and release conditions, an experiment testing platform was constructed. The influence of heating mode, heating load, and filling ratio (FR) on the working stability, thermal resistance, and effective thermal conductivity of the DDFHP were investigated and analyzed. The results mainly showed that under the bottom heating condition of the DDFHP, the thermal resistance of the DDFHP decreases with increasing heating power when the FR is low, and it first increases and then decreases when the FR is high. Among all the tested heating powers, the thermal resistance can be reduced to as low as 0.039 °C/W. Under the simulated heating conditions of phase change material on the DDFHP, at the same heating power, the thermal resistance of the DDFHP decreases first and then increases with the increase of the FR when the liquid filling height is less than 130 mm. In this case, the optimal FR of the DDFHP is 15 %, and the thermal resistance can be as low as 0.1 °C/W. The present study contributes to future HP applications in thermal storage enhancement.

Detailed visualization experiments on the start-up process and stable operation of double-layered pulsating heat pipes under vertical and horizontal orientations

The thermal characteristics in a double-layered 3D-CLPHP are investigated by visualization experiments. The results are compared with those of a single-layered CLPHP under the vertical and horizontal orientations and a filling ratio (FR) of 35%, 50%, or 65%. The tube's inner diameter (ID) is 6 mm, slightly over the limiting value for water. The orientation is found highly determinative to the flow pattern of liquid slug trains in each tube layer. The flow behavior appears similar for the two layers under the vertical orientation but apparently different under the horizontal orientation. When horizontally placed, the liquid slug trains tend to drain down to the lower layer, thereby not only triggered but sustained continuous pulsation motion. Intense cross-layered flow motion, attributed to the interaction between the downward gravity and upward gaseous expansion or buoyancy effect, is recorded during the operation. Sufficient working fluid distribution inside each layer for the overall FR of 65% is recommended. Instead, the single-layered CLPHP fails to maintain a stable oscillation motion without the assistance of gravity. The double-layered CLPHP outperformed the single-layered CLPHP by 12.8−15.1% in thermal resistance even under the vertical orientation.

Construction of multi-interface magnetic FeMnC modified carbon/graphene aerogels for broadband microwave absorption

Magnetic carbon-based aerogels with low-density and strong attenuation, have attracted significant attention as microwave absorbing materials, but still face huge challenges. Herein, magnetic FeMnC modified carbon/Graphene aerogels (NCMF) were synthesized utilizing freeze casting following a carbothermal reduction process. The conductivity, defects density, material component and electromagnetic properties can be regulated by the temperature. The NCMF aerogels exhibit remarkable microwave absorption properties, with an effective absorption bandwidth of 5.76 GHz at a thickness of 2.1 mm and a minimum reflection loss as low as −50.8 dB at 7.52 GHz with a fill ratio of only 5 wt%. The exceptional microwave absorption capabilities of NCMF aerogels are attributed to the synergistic effects of dielectric loss, magnetic loss, three-dimensional (3D) carbon conductive network, and the optimal impedance matching. Consequently, this research paves a way for the development of microwave absorbing materials with lightweight, broadband and strong microwave absorption at low loading.

Thermal hydraulic behavior of a large dimension hybrid heat pipe/oscillating heat pipe

Similar to the layout of an oscillating heat pipe (OHP), a quartz hybrid heat pipe (HHP) with an inner diameter of 5 mm, exceeding 59.7 % of the capillary threshold of OHP, was designed. The detailed thermal hydraulic behavior of fluid in the HHP has been revealed. It was found that the HHP undergoes a heat transfer mode transition from phase change to pulsating flow. It is also means that the liquid slugs can be dynamically and stably formed if the heat input is sufficient. The single bubble growth and the multi-bubble coalescence are two ways to form the intermittent flow. In addition, as the main flow pattern in low filling ratio (FR), the formation of annular flow is closely concerned in the behaviors of fluid. Moreover, the higher the FR is, the clearer the contour of slug flow is. At the same time, the oscillating motion can be formed easily at a high FR, resulting in a better performance of HHP in lower heat load. However, as the heat input increases, HHP with a 60 % filling ratio exhibits lower thermal resistance, achieving a minimum value of 0.08 °C/W at 100 W.

Investigation of structural parameters influencing vibration characteristics of heavy-duty truck diesel tanks.

The working conditions of heavy-duty trucks are very complicated as the diesel shaking and resonance problems, which causes weld tears, separators to fall off, and other failures occur. Through experiments and finite element simulation, the natural frequency and vibration mode of a given 400 L diesel tank were calculated to study the influences of structural parameters such as the fill ratio (0.1-0.9), the number of baffle plates (0, 1, 2), the spacing of the plates (240 mm, 400 mm, 560 mm) and the aperture (38 mm, 78 mm, 118 mm) on the modal parameters with the wet mode method. The results of the hammering mode test and the simulation modal analysis agree well with the maximum error is 4.8%; the natural frequency of the diesel tank will increase with fill ratio decrease; the increase of the baffle plate number (0, 1, 2) can effectively increase the first-order natural frequency of the diesel tank, but the change of the natural frequency is not obvious on the higher order; the higher plates spacing has a smaller natural frequency; increasing the aperture will highly increase the natural frequency, 188 mm has better vibration safety.

Radiographic evaluation of robot-assisted versus manual total hip arthroplasty: a multicenter randomized controlled trial

BackgroundThe effectiveness of robot-assisted surgery remains contentious due to the lack of high-quality randomized controlled trials (RCTs) to elevate the level of evidence. We aimed to evaluate the postoperative radiographic outcomes of robot-assisted (RAS-THA) versus manual (M-THA) total hip arthroplasty.MethodsThis multicenter RCT was performed from March 1, 2021 to December 1, 2021. Patients were randomly assigned to routine M-THA or to RAS-THA that used the TRex-RS orthopedic joint surgical navigation system. The primary outcome was to compare the acetabular component orientation, femoral stem alignment, femoral canal fill ratio, and leg length discrepancy between RAS-THA and M-THA using postoperative radiography. Subgroup analyses of the two groups stratified by surgical approach, gender, and BMI were also conducted.ResultsSeventy-three participants were randomly allocated to the RAS-THA group, while seventy-two participants were assigned to the M-THA group. Compared to the M-THA group, the RAS-THA group exhibited less variability in the preoperative planning of the vertical center of rotation (VCOR; P < 0.001), demonstrated a significant advantage in femoral stem alignment (P = 0.004), and showed pronounced decreases in inequality and in the variability in leg length discrepancy (P < 0.001). There was no significant difference in the Lewinnek safe-zone ratio (P = 0.081) and the femoral canal fill ratio (P > 0.05) between the two groups. Further subgroup analysis also showed that the RAS-THA group had fewer horizontal center of rotation (HCOR) and leg length differences when stratified by surgical approach, gender, and overweight status.ConclusionThis RCT found that, regardless of the surgical approach, gender, or body mass index, RAS-THA can effectively improve the postoperative VCOR and significantly reduce the variability of leg length difference. RAS-THA should be considered an effective method to enhance surgical precision by achieving less variability in challenging patients with leg length discrepancies.Trial registration: ChiCTR2100044124.

Low-grade heat to electricity conversion using the self-circulation of a magnet inside a single-turn pulsating heat pipe

Low-temperature (≤100°C) heat sources are abundantly and ubiquitously available in nature, such as solar energy, and in the form of untapped waste heat. This work aims to harness low-grade heat sources by introducing a portable harvesting system capable of effectively converting small spatial temperature gradients to mechanical and then electrical energy while maintaining a relatively high heat transfer capability. The designed and studied pair of harvesters are based on single-turn pulsating heat pipes with different condenser locations. Asymmetrical heating and cooling of the looped capillary glass tube gives rise to the bulk circulation of the internal fluid with occasional oscillation. The thermally-driven two-phase flow carries a spherical neodymium magnet fitted inside the tube. Two external solenoids generate a small amount of electricity every time the magnet passes through them. The proper functioning of energy-harvesting pulsating heat pipes (EH-PHPs) was investigated for pure water, acetone, and ethanol as the working fluids. Only water demonstrated satisfactory results and was thus selected as the main working fluid. Subsequently, high-frame-rate imaging of the internal flow along with time-domain temperature and open-circuit voltage data were employed and discussed to study the working principles of the harvester. In the next step, the mechanical, thermal, and electrical performance of the two EH-PHPs were quantitatively investigated for five different filling ratios (FRs) between 20% to 80% and five levels of heat input from 20.0W to 40.0W for each FR. Among the studied conditions, the EH-PHP with horizontal condenser (HC) configuration and 50% FR demonstrated the best performance in all three aspects. Accordingly, when 40.0W of heat was supplied to this ideal case, the magnet mean circulation frequency around the loop, effective thermal conductivity, and average induced open-circuit voltage (peak-to-peak) reached their maximum values of 0.46Hz, 11.5kW/(mK), and 0.53V, respectively. Although the integration of electromagnetic generators had reduced the heat transfer performance, the thermal conductivity of the EH-PHPs was comparable to that of conventional heat pipes and at least 25 times better than copper. Finally, the EH-PHP with HC configuration and 50% FR, the superior case, produced up to 5μW of electrical power while its solenoids were connected to load resistances with an optimum impedance. Therefore, even in its early stage of development, the portable EH-PHP can be used to supply low-power electronics such as a quartz watch. The generated electricity corresponds to about 0.01% relative Carnot efficiency. The remarkable thermal conductivity and capability of electricity production with less than 5°C temperature difference across the tube distinguish the EH-PHPs from mature energy harvesting technologies with higher energy conversion efficiencies.