Large Pressure Research Articles

Brief Discussion on Non-destructive Testing Methods for Pressure Pipeline Defects

With the development of China's oil and gas energy industry, the specifications of pressure pipelines for oil and gas transport are also becoming higher and higher, such as large caliber, ultra-thin wall, high pressure and other requirements, and the defects of pressure pipelines are becoming increasingly prominent. Due to the use of the environment, the material of the pipeline and other reasons, the pressure pipeline will produce a variety of defects in use. Non-destructive testing should be carried out on the defects caused by the pipeline in a timely manner, and according to the test results, defects should be graded according to the corresponding testing standards, so as to prevent the in-service pipeline from containing excessive defects and prevent pipeline breakage or explosion accidents.

Computational Modeling of High-Speed Flow of Two-Phase Hydrogen through a Tube with Abrupt Expansion

Hydrogen can become a prevalent renewable fuel in the future green economy, but technical and economic hurdles associated with handling hydrogen must be overcome. To store and transport hydrogen in an energy-dense liquid form, very cold temperatures, around 20 K, are required. Evaporation affects the achievable mass flow rate during the high-speed transfer of hydrogen at large pressure differentials, and accurate prediction of this process is important for the practical design of hydrogen transfer systems. Computational fluid dynamics modeling of two-phase hydrogen flow is carried out in the present study using the volume-of-fluid method and the Lee relaxation model for the phase change. Suitable values of the relaxation time parameter are determined by comparing numerical results with test data for high-speed two-phase hydrogen flows in a configuration involving a tube with sudden expansion, which is common in practical systems. Simulations using a variable outlet pressure are conducted to demonstrate the dependence of flow rates on the driving pressure differential, including the attainment of the critical flow regime. Also shown are computational results for flows with various inlet conditions and a fixed outlet state. Field distributions of the pressure, velocity, and vapor fractions are presented for several flow regimes.

Ultrasmall single-layered NbSe2 nanotubes flattened within a chemical-driven self-pressurized carbon nanotube

Pressure can alter interatomic distances and its electrostatic interactions, exerting a profound modifying effect on electron orbitals and bonding patterns. Conventional pressure engineering relies on compressions from external sources, which raises significant challenge in precisely applying pressure on individual molecules and also consume substantial mechanical energy. Here we report ultrasmall single-layered NbSe2 flat tubes (< 2.31 nm) created by self-pressurization during the deselenization of NbSe3 within carbon nanotubes (CNTs). As the internal force (4–17 GPa) is three orders of magnitude larger than the shear strength between CNTs, the flat tube is locked to prevent slippage. Electrical transport measurements indicate that the large pressure within CNTs induces enhanced intermolecular electron correlations. The strictly one-dimensional NbSe2 flat tubes harboring the Luttinger liquid (LL) state, showing a higher tunneling exponent αNbSe2@CNT≈0.32\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }_{{NbS}{e}_{2}{{{{{\\rm{@}}}}}}{CNT}}\\approx 0.32$$\\end{document} than pure CNTs (αCNT≈0.22\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }_{{CNT}}\\approx 0.22$$\\end{document}). This work suggests a novel chemical approach to self-pressurization for generating new material configurations and modulating electron interactions.

Simulation of Pressure Swing Adsorption for Oxygen Concentrator Using LiX Zeolite

The existence of oxygen is needed in various fields such as health, industry, aerospace, and energy. Pressure swing adsorption method using zeolite A and X is commonly used in the oxygen separation process. Zeolite LiX is widely used especially in oxygen purification systems from air for medical needs until the purity reach &gt;90%. In the present work the simulation studies of oxygen separation from air using zeolite LiX were investigated by pressure swing adsorption method. This simulation uses 2 beds/4 steps Skarstrom cycle which generally consists of bed pressurization, adsorption, depressurization and desorption. Several variables were studied such as the effect of pressure, cycle time, and temperature to determine the level of product purity. The simulation shows that the increase in oxygen concentration is caused by an increase in operating pressure and total cycle time to obtain maximum results. Meanwhile, large pressures can reduce the efficiency of the adsorbent. The maximum oxygen concentration that can be obtained up to 99%. However, the temperature variation has no significant change. In general, pressure plays the most significant role in oxygen purification.

Effects of low ambient pressure on the flame characteristics of ethanol−gasoline blended pool fire

The flame characteristics of Ethanol−Gasoline pool fire with different blend ratios were experimentally studied in a large−scale pressure−controlled compartment with ambient pressure of 40 kPa, 61 kPa, 80 kPa, and 101 kPa. The flame height, centerline temperature, and radiant heat flux were measured. The flame height increases notably with decreasing ambient pressure, but the flame temperature (intermittent and plume regions) slightly increases. With increasing ethanol ratio, the flame height and temperature decrease monotonously under large ambient pressure, but show a non−monotonic variation with a peak value at low ambient pressure and ethanol ratio of 10 %∼20 %. Heskestad’s flame height and temperature correlations were not suitable for blends pool fire under low ambient pressure. The new modified model for flame height correlation with ambient pressure and combustion heat of blends, and flame temperature correlation with flame height, fuel property parameter, and ambient pressure were developed with a better prediction. The addition of ethanol and decrease of ambient pressure led to the reduction of radiation loss from flame, and the non−monotonic variation with a peak value also occurs with increasing ethanol ratio at relatively large ambient pressure and ethanol ratio of 20 %. A new modified model based on the classical solid flame model was also developed to predict the radiative fraction, considering the ambient pressure, stoichiometric ratio, and the ratio of the combustion heat to the vaporization heat.

Study on the influence principle and application law of intake wall thickness on uniflow scavenging opposed-piston engine

Energy efficient utilization is an important research direction of energy conversion systems. Uniflow scavenging opposed-piston engine has the potential to achieve higher thermal efficiency than classic engines. The lack of valve mechanism leads to the poor scavenging performance of uniflow scavenging opposed-piston engines. Many studies have been conducted to improve scavenging performance by optimizing intake structure. However, the critical influence of intake wall thickness has not been considered. Therefore, a three-dimensional simulation model of intake wall thickness was established and validated. Then the detailed influence of intake wall thickness was explored. Last, the influence law of intake wall thickness under different application conditions is explored. According to the simulated results, intake wall thickness significantly affects the scavenging process by influencing exhaust gas backflow and changing the scavenging passage; the vital influence of intake wall thickness should be considered in optimizing other intake structures. Thicker intake wall thickness increases the backflow resistance and retains more exhaust gas backflow in the intake port, which is conducive to orderly cleaning backflow exhaust gas. The thinner intake wall thickness should be selected at small intake pressure, and the thicker intake wall thickness should be selected at large intake pressure.

Discovering the Clinical Relevance of Heart-Lung Interactions.

In 1978, Dr. Pinsky's scientific career became firmly directed toward understanding the deeper meaning of heart-lung interactions. This would define his focus for the next 45 yr. At the time, he and colleagues studied the effects of changes in intrathoracic pressure on left ventricular performance in humans, documenting that the primary effect of large negative swings in intrathoracic pressure was to increase left ventricular transmural ejection pressure, and thus left ventricular afterload, selectively. They concluded that large intrathoracic pressure changes directly influence cardiac performance. This fundamental observation was followed by many additional observations in both highly invasive animal studies supported by less invasive clinical studies, which showed that intrathoracic pressure-induced changes in the gradients for venous return to the heart and left ventricular ejection from the heart disproportionately affected both right ventricular and left ventricular function. The direct clinical implications of these results form the rationale for use of continuous positive airway pressure as a primary treatment of acute cardiogenic pulmonary edema and immediate endotracheal intubation for acute upper airway obstruction. These findings subsequently led to the practical use of dynamic changes in left ventricular stroke volume and the associated arterial pulse pressure during positive-pressure ventilation to identify volume responsiveness and, thus, to personalize resuscitation efforts in the treatment of acute cardiovascular insufficiency.

Application of separate layer water injection in high differential pressure wells

With the development of a heavy fine-RRB-layering system and dynamic adjustment, the number of large differential pressure wells increases gradually. The effect of high-pressure difference wells on water injection development is that it is difficult to separate water injection allocation, low pass rate of layers and short effective period of separate sealing, which affects the development effect of water flooding. For this reason, the research on stratified water injection technology with large pressure differences is carried out using step-by-step throttling. The throttling pressure difference borne by the water nozzle is reduced. The large throttling pressure difference produced by the water nozzle is realized. The qualified rate of the layer section is increased to improve the anti-creep performance of the expansion Packer and the sealing effect of large pressure difference injection wells and to extend the service life of the Packer. The field application results of 216 wells in the Shengli Oil Field show that the technique can effectively improve the pass rate of the layers and the sealing effect of the layers and prolong the life of the string.

Early warnings of tipping in a non-autonomous turbulent reactive flow system: Efficacy, reliability, and warning times.

Real-world complex systems such as the earth's climate, ecosystems, stock markets, and combustion engines are prone to dynamical transitions from one state to another, with catastrophic consequences. State variables of such systems often exhibit aperiodic fluctuations, either chaotic or stochastic in nature. Often, the parameters describing a system vary with time, showing time dependency. Constrained by these effects, it becomes difficult to be warned of an impending critical transition, as such effects contaminate the precursory signals of the transition. Therefore, a need for efficient and reliable early-warning signals (EWSs) in such complex systems is in pressing demand. Motivated by this fact, in the present work, we analyze various EWSs in the context of a non-autonomous turbulent thermoacoustic system. In particular, we investigate the efficacy of different EWS in forecasting the onset of thermoacoustic instability (TAI) and their reliability with respect to the rate of change of the control parameter. This is the first experimental study of tipping points in a non-autonomous turbulent thermoacoustic system. We consider the Reynolds number (Re) as the control parameter, which is varied linearly with time at finite rates. The considered EWSs are derived from critical slowing down, spectral properties, and fractal characteristics of the system variables. The state of TAI is associated with large amplitude acoustic pressure oscillations that could lead thermoacoustic systems to break down. We consider acoustic pressure fluctuations as a potential system variable to perform the analysis. Our analysis shows that irrespective of the rate of variation of the control parameter, the Hurst exponent and variance of autocorrelation coefficients warn of an impending transition well in advance and are more reliable than other EWS measures. Additionally, we show the variation in the warning time to an impending TAI with rates of change of the control parameter. We also investigate the variation in amplitudes of the most significant modes of acoustic pressure oscillations with the Hurst exponent. Such variations lead to scaling laws that could be significant in prediction and devising control actions to mitigate TAI.

An eco-friendly wood sponge-based multifunctional pressure and temperature sensor for electronic skin

This work prepared a reduced graphene oxide coated wood sponge for high-property pressure and temperature multifunctional sensors which can realize high sensitivity, large pressure range, and low detection limit.

Extensive analysis of the applicability range of the linear kinetic approaches in the case of the pressure driven gas mixture flows

The study of gas mixture flows through micro- and macro-channels remains a very attractive area for theorists and experimentalists worldwide, mainly due to their great practical applicability in several aspects of science and industry. The present work includes a comparative study between the linear (McCormack model) and the nonlinear (DSMC method) kinetic theories of binary gas mixture flows through channels over a wide range of the involved parameters. The results show that the McCormack model is a reliable kinetic model for predicting the gas mixture flow behavior. Specific criteria with respect to the applicability range of the linear kinetic theory of short and long capillaries are proposed. The analysis shows that the separation phenomenon remains strong even in the case of small pressure drops. The applicability range of the linear kinetic theory for binary gas mixture flows driven by large pressure drops is obtained to be smaller compared to that of single gases but still wide enough covering a wide range of pressure ratios. Furthermore, the present work shows that the long capillary theory remains a very powerful tool for studying the gas mixture flow behavior under weak and strong nonequilibrium conditions. This work provides a kinetic database of the linear kinetic data (as supplementary material), which until today is still missing from the literature, and as it is shown throughout this work, it can be used far beyond the restrictions defined by the linear kinetic theory.

Негативное влияние гистерезисных явлений на процесс разработки месторождений нефти и газа

It is known that irreversibilities of hysteresis nature of global or local scale, lead to the necessity to revise the methods of solving the main problems of hydrodynamic modelling and analysis of dynamic systems, as they can radically affect the traditional conclusions and practical recommendations. It is assumed that in the steady-state mode of motion or filtration, phase displacements make all sorts of oscillations in the vicinity of the unstable position, due primarily to irreversible hysteresis phenomena and jumps arising from the instability of the front of oil displacement by water, the manifestation of capillary effects, hysteresis of phase transitions, irreversibility of deformations under excessive load at large pressure drops, including hydraulic fracturing. With this purpose in the theory of catastrophes the dynamic models of growth are investigated and control parameters are selected with the calculation and the possibility to predict the expected local irreversibilities and instabilities before the onset of bifurcation. Hysteresis behaviour in the filtration process is generated by lithological differences of geofluidodynamic medium and its geological and physical characteristics and properties of saturating fluids. And as a rule, it is provoked by not always adequate, excessive external load on the tested medium. The proposed solutions are part of a new concept of unsteady waterflooding, which provides for early prediction and taking measures in case of instability of the displacement front and, as a consequence, water breakthrough into production wells. It is of great interest to prevent the consequences of these negative effects on the quantitative components of technological and economic indicators, in the case of oil field development we are talking about the final recovery factor of oil, gas and condensate. System optimisation of oil field development is designed for a certain technological and economic effect, including additional oil production, effective mobilisation and saving of injected and withdrawn water and gas.

Evaluating the forces involved in bubble management in DMEK surgery: mathematical and computational model with clinical implications.

To model postoperative forces involved in Descemet membrane endothelial keratoplasty (DMEK) tissue adherence and bubble management, including the impact of surface tension on graft support, with a view towards clinical applications. Tennent Institute of Ophthalmology, Glasgow, and James Watt School of Engineering, University of Glasgow, Glasgow, United Kingdom. Mathematical modelling and computer simulation. Theoretical modelling of biphasic flow and interaction of gas, liquid and tissue within the anterior chamber for static horizontal scenario A (adherent DMEK with mobile bubble) and dynamic vertical scenario B (release of bubble due to pupil block following DMEK). The model assumed incompressibility for both fluids within realistically achievable pressure ranges. Cahn-Hilliard Navier-Stokes equations were discretised through the application of the Finite Element Method. Mathematical modelling and computer simulation showed bubble size, corneal curvature and force intensity influences surface tension support for DMEK tissue in scenario A. Scenario B demonstrated complex, uneven distribution of surface pressure on the DMEK graft during uncontrolled bubble release. Uneven pressure concentration can cause local tissue warping, with air/fluid displacement via capillary waves generated on the fluid-air interface adversely impacting DMEK support. We have quantitatively and qualitatively modelled the forces involved in DMEK adherence in normal circumstances. We have shown releasing air/gas can abruptly reduce DMEK tissue support via generation of large pressure gradients at the liquid/bubble/graft interfaces, creating negative local forces. Surgeons should consider these principles to reduce DMEK graft dislocation rates via optimised bubble size to graft size, longer acting bubble support and avoiding rapid decompression where possible.

Base pressure fluctuations on levitated freestream-aligned circular cylinder

Base pressure fluctuations associated with the large-scale wake structures behind a freestream-aligned circular cylinder and aerodynamic force fluctuations related to them are experimentally investigated in the wind tunnel tests. Measurements at ReD=6.97×104 and 1.04×105 were conducted using pressure-sensitive paint (PSP) and a magnetic suspension and balance system (MSBS) for creating a supportless condition. The obtained pressure fields were mainly analyzed by a modal decomposition combining azimuthal Fourier decomposition and proper orthogonal decomposition (POD). The pressure fluctuations caused by large-scale vortex shedding were observed from the results of frequency analysis for mode coefficients. The states of the fluctuations were classified into three patterns, which are anticlockwise/clockwise circular and flapping patterns. These patterns have been observed in the previous studies for velocity fluctuations in the wake of a freestream-aligned circular cylinder. The conditional sampling analysis revealed that the trend in the amplitude of the pressure fluctuations is different by the state, and the flapping pattern causes a large pressure difference across the cylinder axis. Furthermore, the relationship between the antisymmetric pressure fluctuations and lift fluctuations, which act in the lateral direction of the cylinder, is confirmed.

Fiber-Optics Approach Monitors Drainage Profile of Multistage Stimulation

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 212364, “Can You Feel the Pressure? Strain-Based Pressure Estimates,” by Kyle Haustveit, SPE, and Jackson Haffener, SPE, Devon Energy. The paper has not been peer reviewed. _ The combination of horizontal wells and hydraulic stimulation has been key in unlocking vast unconventional resources across North America and elsewhere, but much remains to be understood regarding how the reservoir is drained across the miles of laterals accessing a resource. The density of pressure gauges required to accurately measure the drainage pattern from a horizontal multistage stimulation is currently not realistic economically or technologically. In this case study, the authors describe a method of monitoring the drainage profile of a horizontal multistage stimulation using optical fiber. Introduction An advanced subsurface diagnostic project was deployed as part of the Hydraulic Fracture Test Site I, Phase 3, funded by the Department of Energy. A lateral observation well was positioned approximately 225 ft away from the nearest two stimulated and producing horizontal wells. Using optical fiber and Raleigh frequency-shift distributed strain sensing (RFS-DSS), strain change was measured in the far field as the offset well was stimulated and first produced. RFS-DSS provides a spatial resolution of 20 cm, allowing for the monitoring of strain changes at finer spatial resolution than can be sensed accurately with low-frequency distributed acoustic sensing. The strain change during the interference test correlated with both the strain change during the crosswell refracturing monitoring and the pressure-gauge change along the monitor well during the interference test. The strong correlation between crosswell refracturing and interference strain monitoring suggests that the magnitude of crosswell strain responses is directly proportional to the intensity of strain change when the offsetting wells are put online. The comparison of data recorded from RFS-DSS and six reservoir-sensing pressure gauges displayed a strong correlation between the total strain change and total pressure drawdown. Three gauges positioned in regions of large negative strain change during first production, interpreted as drawdown, showed large pressure declines; the other three gauges, positioned in areas of small strain change, saw small pressure declines. The correlation was applied to the total length of the wellbore based on the strain change to estimate a pressure along the entire lateral, including areas without pressure gauges. Pilot Design Located in DeWitt County, Texas, the project consisted of a combination of production infill wells (12H and 13H), pre-existing primary wells (2H, 4H, 6H, and 8H), liner refracturing wells (3H and 5H) and one unstimulated observation well (14H). The wells are landed in the lower Eagle Ford formation. While drilling the observation lateral, horizontal core was collected and used to investigate the frequency of hydraulic and propped fractures created from the 4H and 5H original stimulations. The 14H lateral was equipped with permanent optical fiber, one internal pressure-sensing gauge used for sealed wellbore pressure monitoring, and nine reservoir-sensing pressure gauges to monitor fracture interactions and pressure drawdown from the offset wells. Three of the gauges failed to show connection to the reservoir and were discarded for this analysis.

Study on single-phase and two-phase flow and heat transfer characteristics of HFE-7100 in manifold microchannel heat sink with corrugated bottom

To solve the problem of high heat flux heat dissipation in microelectronic devices, a manifold micro-channel heat sink with corrugated bottom (CB-MMC) is pro-posed on the basis of the manifold microchannel heat sink (MMC). The flow and heat transfer characteristics of HFE-7100 in MMC and CB-MMC are investigated numerically. The results show that CB-MMC reduces the pressure loss and enhances the heat transfer performance in single-phase flow. The orthogonal test method is used to obtain structural design solutions with optimal thermal performance. It is observed that the temperature reduction is always at the expense of the increase of the pressure drop. In addition, the optimization parameters combination obtained through comprehensive evaluation of temperature and pressure drop through weight matrix ? optimized solution 19 (wavelength A = 800 ?m, am-plitude B = 40 ?m, channel depth C = 180 ?m, outlet width D = 300 ?m, channel width E = 25 ?m). Its Tave has decreased by 6.89?C, ?P decreased by 10.27 kPa. Moreover, the subcooled boiling flow and heat transfer performance in MMC and CB-MMC are comparatively studied. The results demonstrate that the dynamic behavior of vapor bubbles causes large pressure fluctuations, which further leads to small temperature fluctuations, and thus reduces the stability of the flow and boiling heat transfer. Compared with MMC, CB-MMC exhibits more stable two-phase flow and better boiling heat transfer.

Consideration on the Applicability of Electron Beam Welding for the Manufacture of Small Modular Reactor

The overall technology required for the application of electron beam welding to ultra-thick plate pressure vessel in small modular reactors was considered. Electron beam welding has the advantage of reducing the manufacturing time compared with traditional arc welding, but it requires the construction of complex equipment and the establishment of related process technology. Based on the thickness of 150~250 mm, the electron beam welding equipment for application to SMR pressure vessel requires large-capacity equipment of 120~170 kV, 150 kW or more, which has never been commercially manufactured so far. A stable beam must be maintained for a constant time. Anti-arcing and seam tracking functions are also required. Electron beam welding of low-alloy steel has superior characteristics in terms of strength and toughness compared with arc welding. The welded area can be made into a base material by solution heat treatment. Cleaning and gap control are important for weld quality. Weld area should not be affected by magnetic fields. As circumferential welding overlaps in span at the welding start and end, it requires precise setting of welding parameters. For welding of large pressure vessel, customized cylindrical vacuum chamber or local vacuum chamber are suitable. It must be shielded from X-rays generated during welding.

Reduced resting beat-to-beat blood pressure variability in females with relapsing-remitting multiple sclerosis

BackgroundRelapsing-remitting multiple sclerosis (RRMS) is a demyelinating disease of the central nervous system and cardiovascular autonomic dysfunction has been well documented in this population. The sympathetic nervous system contributes to beat-to-beat blood pressure regulation primarily by baroreflex control of the peripheral vasculature which may be impaired in females with RRMS. Even at rest, attenuated sympathetic control of vasomotor tone may result in large and frequent blood pressure excursions (i.e., greater blood pressure variability). Therefore, the primary purpose of this investigation was to test the following hypotheses; (1) females with RRMS have augmented beat-to-beat blood pressure variability compared to healthy controls and (2) reduced sympathetic baroreflex sensitivity in females with RRMS is related to augmented blood pressure variability. MethodsElectrocardiogram and beat-to-beat blood pressure were continuously recorded during 8–10 min of supine rest in 26 females with clinically definite RRMS and 24 sex-, age- and BMI- matched healthy controls. Muscle sympathetic nerve activity (MSNA) was recorded in a subset of participants (MS, n = 15; CON, n = 14). Traditional statistical measurements of dispersions were used to index beat-to-beat blood pressure variability. Spontaneous sympathetic baroreflex sensitivity was quantified by sorting diastolic blood pressures into 3 mmHg bins and calculating MSNA burst incidence within each bin. Weighted linear regression was then used to account for the number of cardiac cycles in each bin and calculate slopes. Spontaneous cardiac baroreflex sensitivity was determined using the sequence method. ResultsGroups had similar resting mean arterial pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP), MSNA burst frequency and MSNA burst incidence (All P > 0.05). The standard deviation and interquartile range of MAP, SBP and DBP were less in females with RRMS compared to healthy controls (All P < 0.05). There were no between groups differences in sympathetic baroreflex sensitivity or cardiac baroreflex sensitivity (Both P > 0.05) and baroreflex sensitivity measures were not related to any indices of blood pressure variability (Both P > 0.05). ConclusionThese data suggest that females with RRMS have reduced beat-to-beat blood pressure variability. However, this does not appear to be related to changes in sympathetic or cardiac baroreflex sensitivity.

Direct solar regenerated desiccant dehumidification system for sustainable ventilation in hot and humid climate

Conventional vapor-compression cooling for outdoor air dehumidification is energy intensive, especially in hot and humid regions. To reduce energy consumption, desiccant dehumidification wheels and packed beds are integrated with the air conditioning systems. However, these systems have large pressure drops and require external heating sources for regeneration. In this study, a two-stage direct solar-regenerated desiccant dehumidification rotating belt (SR-DDRB) system is proposed. The aim is to sustainably dehumidify the outdoor air while meeting the indoor humidity levels at enhanced indoor air quality and minimal energy. The system was sized, and its operation was optimized using artificial neural network for a case study of a typical office space located in hot and humid climate. The supplied outdoor air flowrate varied between 0.055 kg/s and 0.085 kg/s, which is much higher than the minimum required of 0.0392 kg/s. During months of high humidity, the operating conditions were affected by outdoor air humidity conditions such that higher outdoor air flowrate and bypass factor were achieved at low outdoor humidity, and vice versa. During months of low humidity, the operating conditions were primarily influenced by the outdoor air temperature rather than outdoor air humidity to minimize energy consumption. Over the cooling season and while operating at optimal conditions, the SR-DDRB system was able to meet an indoor relative humidity (RH) of 58 ± 1.5 %. Additionally, it maintained the CO2 concentration of 780 ± 41 ppm, well below the allowable 1,000 ppm, whereas electrical energy consumption was 78.8 kWh over the entire cooling season.

Expedition 5300: limits of human adaptations in the highest city in the world.

Exposure to chronic hypobaric hypoxia imposes a significant physiological burden to more than 80 million humans living above 2500m throughout the world. Among them, 50000 live in the world's highest city, La Rinconada, located at 5000-5300m in southern Peru. Expedition 5300 is the first scientific and medical programme led in La Rinconada to investigate the physiological adaptations and altitude-related health issues in this unique population. Dwellers from La Rinconada have very high haemoglobin concentration (20.3±2.4g/dL; n=57) and those with chronic mountain sickness (CMS) exhibit even higher concentrations (23.1±1.7g/dL; n=150). These values are associated with large total haemoglobin mass and blood volume, without an associated iron deficit. These changes in intravascular volumes lead to a substantial increase in blood viscosity, which is even larger in CMS patients. Despite these large haematological changes, 24h blood pressure monitoring is essentially normal in La Rinconada, but some results suggest impaired vascular reactivity. Echocardiography revealed large right heart dilatation and high pulmonary arterial pressure as well as left ventricle concentric remodelling and grade I diastolic dysfunction. These changes in heart dimension and function tend to be more severe in highlanders with CMS. Polygraphy evaluations revealed a large reduction in nocturnal pulse oxygen saturation (median SpO2 =79%), which is even more severe in CMS patients who also tended to show a higher oxygen desaturation index. The population of La Rinconada offers a unique opportunity to investigate the human responses to chronic severe hypoxia, at an altitude that is probably close to the maximum altitude human beings can permanently tolerate without presenting major health issues.