Local Pressure Research Articles

Local muscle pressure stimulates the principal receptors for proprioception

Proprioception plays a crucial role in motor coordination and self-perception. Muscle spindles are the principal receptors for proprioception. They are believed to encode muscle stretch and signal limb position and velocity. Here, we applied percutaneous pressure to a small area of extensor muscles at the forearm while recording spindle afferent responses, skeletal muscle activity, and hand kinematics. Three levels of sustained pressure were applied on the spindle-bearing muscle when the hand was relaxed and immobile ("isometric" condition) and when the participant's hand moved rhythmically at the wrist. As hypothesized to occur due to compression of the spindle capsule, we show that muscle pressure is an "adequate" stimulus for human spindles in isometric conditions and that pressure enhances spindle responses during stretch. Interestingly, release of sustained pressure in isometric conditions lowered spindle firing below baseline rates. Our findings urge a re-evaluation of muscle proprioception in sensorimotor function and various neuromuscular pathologies.

Preventing postoperative moderate- and high-risk pressure injuries with artificial intelligence-powered smart decompression mattress on in middle-aged and elderly patients: a retrospective cohort analysis.

Aims/Background Artificial intelligence technology has attained rapid development in recent years. The integration of artificial intelligence applications into pressure reduction mattresses, giving rise to artificial intelligence-powered pressure reduction mattresses, is expected to provide personalised intelligent pressure reduction solutions, through automatic user's data-based adjustment of the patient's local pressure condition to prevent pressure injury. The purpose of this study was to investigate the effectiveness of artificial intelligence-powered smart decompression in the prevention of postoperative medium- and high-risk pressure injury in middle-aged and elderly patients. Methods A total of 400 middle-aged and elderly patients admitted to our hospital from June 2021 to December 2023 were selected as study subjects. Patients were categorised into observation and control groups according to the medical record system. General demographic data of the patients were collected. The propensity score matching method was used to balance the baseline data of the two groups of patients. The incidence, severity, complications and sleep quality in the matched study subjects were also compared. Results After matching, there were 96 patients in the two groups, and the differences in baseline data between the two groups were not statistically significant. Pressure injury and the total incidence of complications in the observation group were significantly lower than those in the control group (p < 0.05). Before treatment, there was no difference in the scores of all aspects of the Richards Campbell Sleep Questionnaire between the two groups (p > 0.05). After treatment, the scores of all aspects of Richards Campbell Sleep Questionnaire in the observation group were significantly lower than those in the control group (p < 0.05). Conclusion The artificial intelligence-powered smart decompression mattress can significantly prevent moderate- and high-risk pressure injury, effectively reducing the incidence of pressure injury and complications in postoperative long-term bedridden patients, alleviating the severity of pressure injury, relieving the pressure on various parts, and improving the sleep quality of patients.

Thermal and hydrodynamic analysis inside a channel partially filled with porous material

AbstractIn this work, the transfer of heat and changes in fluid pressure within a rectangular channel fairly packed with porous material have been studied numerically for various Darcy numbers and dimensionless porous layers. The model was run with the following assumptions: laminar flow, forced convection, isotropic porous material, local thermodynamic equilibrium, constant wall temperature boundary condition, and no thermal dissipation. The study covers a broad range for the dimensionless porous layer, 0 ≤ hr &lt; 1, and the Darcy number, 10−4 &lt; Da &lt; 10−2. The fully developed and developing flow over the channel is investigated in numerical study. It was observed that the inertia effect may be disregarded when Da &lt; 10−4. The local dimensionless bulk temperature distribution, pressure drop, and velocity profiles were all shown to be impacted by the Darcy number and dimensionless porous layers, according to the numerical analysis results. The maximum heat transfer rate was attained when the ratio of the porous layer inside the channel was 0.8, and the pressure gradient was the highest. Partial packing of the channel with a porous material has two advantages: it increases the rate heat transmission rate and results in a much smaller pressure drop than a filled porous medium.

Effect of fiber curvature on gas diffusion layer two-phase dynamics of proton exchange membrane fuel cells

Both straight and curved carbon fibers are widely used in various commercial gas diffusion layer (GDL) fabrications. The effect of the different carbon fiber curvatures on two-phase flow dynamics within the cathode GDLs of proton exchange membrane fuel cells remains unclear. In this study, we investigate liquid transport in three types of GDLs with varying fiber curvatures using the two-phase volume of fluid simulations in OpenFOAM. For the first time, a rod periodic surface model is combined with a layer-by-layer fiber stacking strategy, to stochastically reconstruct GDL structures while incorporating crucial parameters from physical (experimental) GDLs. A grid independence study and model validation are conducted. Following pore network analysis of pore size distribution and connectivity, we study the time-varying GDL total and local water saturation and capillary pressure. Despite maintaining similar layer and bulk porosity, increased fiber curvature enhances pore connectivity but raises water saturation and capillary pressure, increasing the risk of flooding. Additionally, droplets in gas channels with straight-fiber GDLs are larger and have slower movement than those in curved-fiber GDLs. Fiber curvature inversely affects drainage capacity in GDLs and connected channels. With comparable water saturation and capillary pressure, curved-fiber GDLs exhibit lower discrepancies, suggesting improved uniformity in water distribution.

Determination of Local Heat Transfer Coefficients and Friction Factors at Variable Temperature and Velocity Boundary Conditions for Complex Flows

Transient conjugate heat transfer measurements under varying temperature and velocity inlet boundary conditions at incompressible flow conditions were performed for flat plate and ribbed channel geometries. Therefrom, local adiabatic wall temperatures and heat transfer coefficients were determined. The data were analyzed using typical heat transfer correlations, e.g., Nu=CRemPrn, determining the local distributions of C and m. It is shown that they are closely linked. A relationship lnC=A−mB is observed, with A and B as modeling parameters. They could be related to parameters in log-law or power-law representations for turbulent boundary layer flows. The parameter m is shown to have a close link to local pressure gradients and, therewith, near wall streamlines as well as friction factor distributions. A normalization of the C parameter allows one to derive a Reynolds analogy factor and, therefrom, local wall shear stresses.

Model-Based Inference of Flame Transfer Matrices from Acoustic Measurements in an Aero-Engine Test Rig

Abstract Flame dynamics, represented as a flame transfer matrix (FTM), is not directly measurable in test rigs and must be deduced from transfer matrix measurements of the combustion system. The burner-flame transfer matrix (BFTM) approach for FTM estimation is based on local pressure signals from microphones located upstream and downstream of the combustor. It combines acoustic measurements in non-reacting and reacting conditions, with the latter implicitly including flame dynamics. A simple matrix operation yields the FTM. However, this approach assumes loss-free wave propagation at constant speed of sound with no change in cross-sectional area between the microphones and the burner/flame. The present work demonstrates the limitations of these assumptions when applied to a test rig with effusion cooling, bypass annulus, and end contraction. This work proposes a method to infer the FTM for complex combustors by combining reactive transfer matrix measurements of the entire combustor with an accurate low-order model (LOM) of the test rig. This generalized method reduces to the BFTM approach as a special case. The Rolls-Royce SCARLET test rig, operating under realistic engine conditions, is used to analyze the capabilities of the proposed model-based inference method and the limitations of the BFTM approach. First, a LOM based on SCARLET's geometry and operating point is formulated using a generic FTM. This model visualizes the limitations of the BFTM approach concerning various physical and geometrical parameters. Finally, experimental data is used to infer the FTM of SCARLET using the proposed approach.

Stress and flow inhomogeneity in shear-thickening suspensions

HypothesisThe viscosity of dense suspensions surges when the applied stress surpasses a material-specific critical threshold. There is growing evidence that the thickening transition involves non-uniform flow and stress with considerable spatiotemporal complexity. Nevertheless, it is anticipated that dense suspensions of calcium carbonate particles with purely repulsive interactions may not conform to this scenario, as indicated by local pressure measurements with millimeter spatial resolution. ExperimentHere we utilize Boundary Stress Microscopy (BSM), a technique capable of resolving stresses down to the micron scale, to search for evidence of stress heterogeneity. In addition, we measure the flow field at the lower boundary of the suspension where the boundary stress is measured. FindingsWe find localized regions of high-stresses that are extended in the vorticity direction and propagate in the flow direction at a speed approximately half that of the rheometer's top plate. These high-stress regions proliferate with the applied stress accounting for the increased viscosity. Furthermore, the velocity of particles at the lower boundary of the suspension shows a significant and complex nonaffine flow that accompanies regions of high-stresses. Hence, our findings demonstrate that stress and flow inhomogeneity are intrinsic characteristics of shear-thickening suspensions, regardless of the nature of interparticle interactions.

Analysis of the unsaturated hydraulic properties of rocks using multiple laboratory methods

Abstract Proper characterization of the unsaturated hydraulic properties in rocks is significant for predicting fluid flow in soil, hydrogeologic, and petroleum science and engineering problems. In this study, we contributed rigorous analysis of the unsaturated hydraulic properties of three reservoir rock samples (Berea Sandstone, Guelph Dolomite, and Indiana Limestone). An improved version of the standard evaporation method (HYPROP) was developed to cater specifically to rock samples. The improved HYPROP setup enables measurements of local water pressures within rock samples without disturbing the upper portion of the samples. The obtained results were compared with those obtained using the conventional pressure plate method and a state-of-the-art nuclear magnetic resonance (NMR) method. Observed data were analyzed in terms of four different unimodal and bimodal hydraulic functions. The HYPROP data were found to be relatively close to the pressure plate data of two carbonate rocks. The NMR-based data were reasonably consistent with the HYPROP data, with differences likely due in part to the fact that they were obtained using two different 5-cm long plugs taken from the same core. Heterogeneity along the rock cores from which the samples were taken could be a major reason for the observed differences, and hence should be considered in reservoir analyses.

Aspects of Reduced Performance of Proton-Exchange-Membrane Water Electrolysis Via Continuum Modeling

Proton-exchange-membrane water electrolysis (PEMWE) is a technology, where hydrogen is electrochemically produced from water. Efficient industrial-scale production of hydrogen via PEMWE is contingent upon developing systems that are sufficiently resilient to operate under non-ideal operating conditions. Mathematical models can provide insight into the underlying physical mechanisms and inform the development of mitigating strategies. In the current work, a cell-level non-isothermal continuum model that is based on concentrated-solution theory that accounts for multiple ionic mobile species in the membrane and ionomer, energy transport, and fluid flow through porous media, was used to investigate two challenges to PEMWE becoming a viable technology, specifically contamination and hydrogen crossover. In cationic contamination, dissolved salts in the reactant water supplant protons in the membrane and ionomer and significantly increase the applied potentials required for operation. Hydrogen crossover is a concern especially in low-current operational modes, which can arise due to PEMWE powered by variable and cyclical renewable energy sources and can result in the production of combustible gas mixtures.For cation-contaminated cells, simulation results suggest that the uptake of the contaminant cation increased as a function of current density until local conditions in the cathode catalyst layer (cCL) allowed the contaminant desorption to occur. The model suggests that the increased cell potential is primarily due to proton activity losses in the hydrogen evolution reaction within the cCL and that ionic conductivity losses are insufficient to cause the performance losses observed experimentally. Agreement with experimental data lends the model as a possible method or predictive models for PEMWE cell recovery methods. Observations of hydrogen crossover simulations suggest several aspects of hydrogen crossover, which include that localized pressures within the catalyst layers can enhance crossover, bubble-nucleation kinetics limit the exhaust of product gases, and convective fluxes due to electroomostic drag are negligible. An improved understanding of the crossover mechanisms can inform the development of low-crossover designs and mitigation strategies. Figure 1

Numerical Study of Liquid Water Formation and Transport in Porous Media

Fundamental understanding of liquid water formation and transport in fuel cells is of great importance for achieving high durability, reliability, and maximizing cell performance. For low temperature fuel cells, water may exist as vapor or liquid phase and is involved in various electrochemical reactions and transport mechanisms. The condensation process occurs when local water vapor pressure exceeds the saturation pressure. In this work, we first investigate the permeation of liquid water in the gas diffusion layer (GDL). To this aim, a two-dimensional isothermal model considering reconstructed GDL microstructure in conjunction with VOF model is implemented. The effects of mixed wettability of materials, operating temperature, and Polytetrafluoroethylene (PTFE) loadings on liquid water transport in the porous media are investigated numerically. The liquid water breakthrough and the capillary fingering regime are captured and compared. The results show that liquid water saturation in the GDL increases with decreasing PTFE loadings. Moreover, the results demonstrated that the local microstructure in the GDL has a strong effect and can dominate the overall water distribution. To further study water condensation, the isothermal model is expanded to non-isothermal for including physics of phase change heat transfer and species transport. In addition, anisotropic thermal conductivity is incorporated to study its effect on temperature distribution and liquid water distribution. The results show that initially the liquid water is formed as micro droplets and then these micro droplets are combined to form large droplets. Moreover, the impacts of water generation rate, temperature gradient, operating pressure, and contact angle on condensation have been investigated. The findings of this work are expected to provide insights into designing more reliable GDL in fuel cells. Figure 1

Experimental characterization of dynamics of bed‐scale liquid spreading in a trickle bed

AbstractWe report measurements performed to understand the effects of gas (QG) and liquid (QL) flow rates, surface tension (σGL), liquid viscosity (μL), and particle diameter (dp) on dynamics of local liquid spreading, pressure drop, and overall liquid holdup in a pseudo‐2D trickle bed. We show that an increase in the gas‐phase inertia leads to a decrease in the lateral liquid spreading, whereas an increase in the liquid‐phase inertia leads to an increase in the lateral liquid spreading. We also show that an increase in dp causes a reduction in the lateral liquid spreading. Using dimensionless numbers (AB and We), we propose a regime map showing contributions of different forces to the local liquid spreading. We show that the interplay between the inertia and capillary forces governs the liquid distribution near the inlet, whereas the relative contribution of gravitational force increases toward the outlet. Finally, we propose a relation between AB and We for “bed‐scale” liquid spreading.

Comfortable Seatbelts for Pregnant Women with Twins in Japan: A Cross-Sectional Observational Study on Seatbelt Usage.

Optimal seatbelt practices for pregnant women with twins at different gestational ages remain uncertain. To offer recommendations for a comfortable seatbelt system, this cross-sectional observational study explored seatbelt usage and driving habits among women with twins across various pregnancy stages through an online survey that explored driving conditions and comfortable seatbelts at different stages of pregnancy. Women who drove daily before their pregnancy with twins decreased their driving frequency as the pregnancy progressed. Correct seatbelt usage was lower and no seatbelt usage was higher among pregnant women with twins than those with singleton pregnancies. They adapted their seatbelt-wearing techniques to minimise pressure on the chest in the first and third trimesters and the abdomen from the second trimester onwards. The comfortable seatbelts were those that could alleviate belt pressure, featuring waist belts to reduce pressure, wider belts to avoid localised pressure, and shoulder belts resembling a backpack type. When wearing a seatbelt, avoiding pressure on the thorax and abdomen is key for pregnant women with twins. This study suggests that the suitability of driving for pregnant women with twins in their last trimester and the reliability of seatbelts designed for such women should be further examined and validated.

Numerical study of laser-induced cavitation bubble with consideration of chemical reactions

Cavitation generated during injector jetting can significantly affect fuel atomization. Laser-induced cavitation bubble is an important phenomenon in laser induced plasma ignition technology. Limited by the difficulties in experimental measurements, numerical simulations have become an important tool in the study of laser-induced cavitation bubble, but most previous numerical models used to study the dynamics of laser-induced cavitation bubble usually ignore the effect of chemical reactions. In this study, the finite volume method is used to solve the compressible two-dimensional reynolds averaged Navier–Stokes equation by considering the heat and mass transfer as well as the chemical reactions within the cavitation bubble. The effects of overall reaction and elementary reactions on the cavitation bubble are evaluated, respectively. It is found that by additionally considering chemical reactions within the numerical model, lower maximum temperatures and higher maximum pressures are predicted within the bubble. And the generated non-condensable gases produced by the chemical reactions enhance the subsequent expansion process of the cavitation bubble. Besides, the effect of the one-sided wall boundary condition on cavitation bubble is compared with the infinite boundary condition. Influenced by the wall boundary, the cavitation bubble forms a localized high pressure on the side of the bubble away from the wall during the collapse process, which causes the bubble to be compressed into a ”crescent” shape. The maximum pressure and temperature inside the bubble are lower due to localized losses caused by the wall.

Wind tunnel and numerical study of wind pressure coefficients on a medieval Swedish church

Air infiltration has great importance regarding energy, comfort, moisture and dust deposition in naturally ventilated historical buildings like churches. In these buildings, air infiltration is driven by stack effect and wind. When assessing the wind effect, reasonable estimation of wind pressure coefficients is crucial. Local wind pressure coefficients are significantly affected by the shape of the building and turbulence generated by its geometrical features, which – for moderately large churches – typically consist of main building body and window recesses, gable roof, tower, apse, and sacristy. To yield practically useful pressure coefficients, this study conducted wind tunnel and numerical investigations at a church, with gradual addition of these features. Wind pressure was measured on a small-scale model in a wind tunnel, while computational fluid dynamics (CFD) simulations were carried out for both small-scale and full-scale models. By comparing the experimental and numerical results, the SST k–ω turbulence model showed the best accuracy, yielding CFD results in good agreement with wind tunnel measurements. Most challenging was predicting the strong negative wind pressures occurring on a flat roof. Building structures like tower, apse, and sacristy had significant impact on the wind pressures on the central, main building body. This study adds knowledge on wind pressure effects by commonly occurring building components, with particular reference to churches and similar buildings. It was an important basis for developing further models for calculating the wind pressure coefficient.

Thermal energy generated during ultrasonication dominates pinto bean hydration

Ultrasound-assisted hydration (UAH) stands out as a potent strategy, offering multiple advantages over conventional thermal hydration methods. It is an energy efficient, cost and time effective, easily scalable and relatively greener approach. Acoustic cavitation is the major working mechanism in aqueous phase sonication. Cavitation creates immense localised heat and pressure, which ultimately ends up heating the liquid media. To the best of our knowledge, no study dealing with the synergistic relationship between the physical effects of ultrasound and the consequent temperature rise during UAH is available in open literature. This work investigates this complex interplay with aim to identify the dominant working mechanism leading to the hydration of the pinto beans (Phaseolus vulgaris), a variety of common beans. Three different hydration protocols were devised to discern these effects, normal hydration (N) at 25 °C, temperature-controlled UAH (TC) between 18 and 20 °C using an ice bath, and temperature-uncontrolled UAH (TuC). Additionally, the post sonication residual effects of ultrasound treatment were examined. Our findings reveal that sonication induces changes in both TC and TuC treated beans, but more pronounced effects were observed in the absence of temperature control. During TC, acoustic streaming emerged as the predominant sonic action mechanism. Conversely, during TuC, temperature itself emerged as the dominant force, leading to irreversible alterations in the bean's physical and chemical structures.

Battery-Free, Wireless Multi-Modal Sensor, and Actuator Array System for Pressure Injury Prevention.

Simultaneous monitoring of critical parameters (e.g., pressure, shear, and temperature) at bony prominences is essential for the prevention of pressure injuries in a systematic manner. However, the development of wireless sensor array for accurate mapping of risk factors has been limited due to the challenges in the convergence of wireless technologies and wearable sensor arrays with a thin and small form factor. Herein, a battery-free, wireless, miniaturized multi-modal sensor array is introduced for continuous mapping of pressure, shear, and temperature at skin interfaces. The sensor array includes an integrated pressure and shear sensor consisting of 3D strain gauges and micromachined components. The mechanically decoupled design of the integrated sensor enables reliable data acquisition of pressure and shear at skin interfaces without the need for additional data processing. The sensor platform enables the analysis of interplay among localized pressure, shear, and temperature in response to changes in the patient's movement, posture, and bed inclination. The validation trials using a novel combination of wireless sensor arrays and customized pneumatic actuator demonstrate the efficacy of the platform in continuous monitoring and efficient redistribution of pressure and shear without repositioning, thereby improving the patient's quality of life.

Study on the water transport characteristics during spontaneous imbibition and its impact on gas desorption

During the exploitation of deep coal resources, the gas hazard becomes increasingly significant, severely threatening the high-quality development of the coal industry and the occupational safety and health of miners. Coal seam water injection is underground coal mines' most commonly used dust control measure. Additionally, it is an effective method for preventing localized coal and gas outburst hazards. After injecting water into the coal seam, spontaneous imbibition causes the retained water in the fractures to migrate under capillary action and widely distribute the water within the coal seam, which enhances the wetting degree of the coal by water and the effectiveness of gas prevention. To reveal the migration characteristics of water in the coal during spontaneous imbibition and its impact on gas control, a self-developed gas-bearing coal spontaneous imbibition system was used to conduct isobaric water injection imbibition and gas desorption experiments on gas-bearing coal samples. The results showed that after the water was injected into the coal sample, it migrated from bottom to top under capillary action, resulting in three stages of abrupt, rapid, and gradual changes in the electrical resistivity of different layers of the coal sample over time. The migration distance of water increased with the imbibition time, but the rate of increase gradually decreased. The compaction load increase reduced the coal sample's average pore size, resulting in faster water migration speed. After imbibition, the water content decreased gradually from bottom to top along the axial direction and showed a non-uniform distribution in the radial direction. During imbibition, the water displaced gas within the coal sample, and the amount of gas displaced increased with the imbibition time. Increasing the amount of water injected and the coal sample compacted load can promote water migration within the coal, expanding the wetted area and displacing more gas. After imbibition, due to the displaced gas being released and the water-lock effect, the atmospheric gas desorption amount of the coal sample decreased with an increase in the amount of water injected, following a modified power function relationship. When the amount of water injected into the coal sample was low, increasing the water-injected amount could significantly reduce the gas desorption expansion energy of the coal sample. However, this trend became less apparent as the amount of water injected continued to increase. To improve the effectiveness of coal seam water injection in preventing gas outburst hazards, it is recommended to carry out water injection operations as early as possible to expand the wetted area of the coal seam and to add gas drainage holes to prevent increased coal body outburst tendencies due to local gas pressure rise in the coal seam.

Unraveling the Mechanisms Behind the Short-Term Effects of Dry Needling: New Insights From a Mediation Analysis With Repeatedly Measured Mediators and Outcomes

ObjectiveTo explore the causal pathways underlying the short-term effects of deep dry needling (DDN) in people with chronic neck pain. DesignExplanatory longitudinal mediation analysis with repeatedly measured mediators and outcomes. SettingPrimary care setting. ParticipantsPatients (N=128) with chronic neck pain. InterventionsParticipants were randomized into 2 groups; DDN of the neck muscles combined with stretching (n=64) and stretching alone (n=64). Main Outcome MeasuresTwo outcomes (pain intensity and neck pain–related disability) and 3 candidate mediators (local pressure pain thresholds [PPTs], cervical range of motion [ROM], and neck muscle strength) were included. Pain intensity was also included as a competing mediator in the mediation analysis for disability. Mediators and outcomes were measured at 3 time points: after intervention and at 2- and 4-week follow-up. Age, sex, and the baseline values of the outcome and mediators were included as pretreatment mediator-outcome confounders. ResultsReductions in pain intensity strongly mediated the short-term effects of DDN on disability, from after intervention to 4-week follow-up. In addition, the attenuation of local hypersensitivity (via increasing PPTs) moderately mediated reductions in pain intensity at each time point. On the other hand, gains in cervical ROM contributed to reducing neck pain–related disability. Changes in muscle strength did not lead to better outcomes. ConclusionsThis novel study demonstrated that DDN effect on neck pain–related disability is strongly driven by the analgesic effects of this physical therapy modality. Increasing PPTs and cervical ROM seem to be also part of the mechanisms behind DDN's effect.

Negotiating between the accountability and the innovation mandates: evidence from Italian schools

ABSTRACT In Italy, the National Evaluation System (SNV), encompassing both internal and external accountability components, is designed not only to hold school actors accountable but also to stimulate innovation and change in pedagogical practices. Nevertheless, existing literature presents inconclusive and contradictory findings regarding the effects and the relationship between school performance-based accountability (PBA) and educational innovation. Utilizing sensemaking and filtering theories, this paper analyses the negotiation of PBA and innovation mandates in Italian schools, emphasizing how school actors interpret, filter, and adapt the policy expectations to their organizational and educational practices. Special attention is given to the influence of local school contexts and performative pressures on this process. The primary data collection method involves interviews with school leadership teams and teachers analysed through an ideal type case analysis. Findings reveal diverse school responses to the double mandates of PBA and innovation. Varied logics of school enactment within the contemporary policy context are identified, influenced by teacher attitudes towards PBA and schools’ socio-economic conditions. Innovation is evident in both advantaged and disadvantaged school contexts, albeit with distinct applications and interpretations. Overall, the adaptation of PBA prerogatives in schools to foster innovation and change is neither uniform nor direct, although external pressures impact educational practices across contexts. Beyond socio-economic factors and administrative and marketing accountability pressures, additional intervening elements include school leadership and staff cohesion as well as school infrastructure and material resources.

Modeling of cryogenic heated-tube flow boiling experiments of hydrogen and helium with the Generalized Fluid System Simulation Program

Accurate modeling of cryogenic boiling heat transfer is vital for the development of extended-duration space missions. Such missions may require the transfer of cryogenic propellants from in-space storage depots or the cooling of nuclear reactors. Purdue University in collaboration with NASA has assembled a database of cryogenic flow boiling data points from steady-state heated-tube experiments dating back to 1959, which has been used to develop new flow boiling correlations specifically for cryogens. Computational models of several of these experiments have been constructed in the Generalized Fluid System Simulation Program (GFSSP), a network flow code developed at NASA’s Marshall Space Flight Center. The new Purdue-developed universal correlations cover the full boiling curve: onset of nucleate boiling, nucleate boiling, critical heat flux, and film boiling. These correlations have been coded into GFSSP user subroutines. The fluids modeled in this study are liquid hydrogen and liquid helium. Predictions of local wall temperature and pressure drop are presented and compared to the test data.