Pressure Difference Research Articles

Advanced visualization of aortic dissection anatomy and hemodynamics

Aortic dissection is a life-threatening cardiovascular disease constituted by the delamination of the aortic wall. Due to the weakened structure of the false lumen, the aorta often dilates over time, which can – after certain diameter thresholds are reached – increase the risk of fatal aortic rupture. The identification of patients with a high risk of late adverse events is an ongoing clinical challenge, further complicated by the complex dissection anatomy and the wide variety among patients. Moreover, patient-specific risk stratification depends not only on morphological, but also on hemodynamic factors, which can be derived from computer simulations or 4D flow magnetic resonance imaging (MRI). However, comprehensible visualizations that depict the complex anatomical and functional information in a single view are yet to be developed. These visualization tools will assist clinical research and decision-making by facilitating a comprehensive understanding of the aortic state. For that purpose, we identified several visualization tasks and requirements in close collaboration with cardiovascular imaging scientists and radiologists. We displayed true and false lumen hemodynamics using pathlines as well as surface hemodynamics on the dissection flap and the inner vessel wall. Pathlines indicate antegrade and retrograde flow, blood flow through fenestrations, and branch vessel supply. Dissection-specific hemodynamic measures, such as interluminal pressure difference and flap compliance, provide further insight of the blood flow throughout the cardiac cycle. Finally, we evaluated our visualization techniques with cardiothoracic and vascular surgeons in two separate virtual sessions.

Effect of the inclination angles of the capillary tube on the natural evaporation of absolute ethanol

Microchannel heat transfer plays an important role in microelectronics technology for heat dissipation, due to its high efficiency and low heat transfer temperature difference and flow resistance. To underpin the fundamental understanding of this technology, the natural evaporation process of absolute ethanol in a capillary tube at inclination angles ranging from 0° to 90° was investigated experimentally by exploring a spectrum of properties, such as Marangoni flow patterns, evaporation rate, heat flux, and temperature distribution. We found that the morphology of the meniscus is similar under different inclination angles, but the liquid and the tube wall slip to varying degrees due to the pressure difference at the liquid–vapor interface during evaporation. Therefore, the force distribution of the meniscus interface is different, and the resultant force is Fmax(60°) > Fmax(0°) > Fmax(30°) > Fmax(90°). We found that the morphology of the meniscus is independent of the inclination angle when absolute ethanol evaporates naturally. And the evaporation rate, heat flux and temperature distribution of meniscus at the initial stage of evaporation follow the law of resultant force distribution. That is, when the inclination angle is 60°, the evaporation rate and heat flux reach the maximum, i.e. 1.64 μm/s and 10.96 W/cm2, respectively, and the temperature between the center of the meniscus and the wedge region reaches 1.5 ℃. We used μ-PIV to observe the Marangoni vortex morphology of the vertical section of the meniscus, and found that there are different degrees of deformation at different inclination angles. When the inclination angle is 90°, the Marangoni vortex structure is destroyed.

Double envelope vacuum insulation panel to contribute to the long-term thermal insulation performance

Vacuum insulation panels (VIPs) have a potential to be used for retrofitting thermal insulation to existing buildings from the viewpoint of low thermal conductivity, small thickness, and light weight. However, in order to realize vacuum insulation panels applicable to building thermal insulation, it is necessary to overcome the challenge of maintaining the low pressure at which high thermal insulation performance can be achieved for several decades. The authors propose double envelope VIPs to maintain this long-term high thermal insulation performance. The double envelope VIP is fabricated by creating a single envelope VIP, wrapping the VIP with core materials, and then inserting it into the envelope for vacuum sealing. By applying the double envelope VIPs, the pressure difference and the permeation of gas in the inner VIP can be drastically reduced, resulting in a longer VIP lifetime. In this paper, the gas permeabilities of the gas barrier envelopes are experimentally estimated. Then, the pressure ageing in the double envelope VIP is calculated. The inner pressure of double envelope VIP after 50 years is 5.4 Pa for the envelope of aluminium composite film, indicating that low pressure can be maintained long-term. Next, the authors carry out accelerated test, in which the double envelope VIPs are placed in a chamber at 80oC and removed every two weeks to measure the effective thermal conductivity. Even after 141 weeks, one sample with a getter agent on the inside and a desiccant agent on the outside indicates only 10.5 % decrease in the thermal resistance. From this result, the long-term high thermal insulation performance can be obtained by fabricating double envelope VIPs.

Dynamic analysis of an adiabatic compressed air energy storage system with temperature-regulated in air tanks

In this study, an innovative temperature regulation method is developed to augment the air storage capacity of adiabatic compressed air energy storage. Hot water, produced by recovering waste heat from the discharging process, is injected into these tanks to control the air temperature as needed. The transient-state calculation models have been established for each component, and validation is performed using experimental data obtained from published work. The utilization of proportion integration differentiation control technology enables precise regulation of the air outlet temperature of heat exchangers, achieving a control accuracy of 1K. The operational status of the components has been investigated, and a comparison is made between the performances of the modified and traditional adiabatic compressed air energy storage systems. The comparative analysis results show that the modified system can achieve a notable round trip efficiency of 71.71 %, which is comparable to that of conventional system (71.41 %). The effective air storage density of the modified system is 47.24 kg/m3, which presents a 15.08 % increase compared to traditional system (41.05 kg/m3). The influence of discharge pressure and pressure difference between threshold pressure and discharge pressure is also investigated. It is found that the modified adiabatic compressed air energy storage shows a consistently greater effective air storage density than traditional system, with a minimum increase exceeding 10.52 %.

Optimizing physician-encounter frequency for type 2 diabetes patients in primary care based on cardiovascular risk assessment: A target trial emulation study.

To investigate whether the physician-encounter interval for patients with type 2 diabetes (T2D) can be optimized from 2-3 to 4-6 months among those with a calculated 10-year cardiovascular disease (CVD) risk score of less than 20% without compromising their long-term outcomes. Using territory-wide public electronic medical records in Hong Kong, we emulated a target trial to compare the effectiveness of the physician-encounter intervals of 4-6 versus 2-3 months for T2D patients without prior CVDs and with a predicted risk for CVDs of less than 20% (i.e. those patients not in the high-risk category). Propensity score matching was used to emulate the randomization of participants at baseline, where 42 154 matched individuals were included for analysis. The marginal structural model was applied to estimate the hazard ratio (HR) for CVD incidence and all-cause mortality, the incidence rate ratio of secondary and tertiary care utilization, as well as the between-group differences in HbA1c, blood pressure and cholesterol levels. During a follow-up period of up to 12 (average: 5.1) years, there was no significantly increased risk of CVD in patients with physician-encounter intervals of 4-6 months compared with those patients with physician-encounter intervals of 2-3 months (HR [95% confidence interval {CI}]: 1.01 [0.90, 1.14]; standardized 10-year risk difference [95% CI]: -0.1% [-0.7%, 0.6%]), nor for all-cause mortality (HR: 1.00 [0.84, 1.20]; standardized 10-year risk difference: -0.1% [-0.5%, 0.3%]). Additionally, there was no observable difference in the utilization of secondary and tertiary care or key clinical parameters between these two follow-up frequencies. For T2D patients with a calculated 10-year CVD risk of less than 20%, the interval of regular physician encounters can be optimized from 2-3 to 4-6 months without compromising patients' long-term outcomes and saving substantial service resources in primary care.

Application of Low-Temperature Temporary Plugging Agents in Coalbed Methane Volume Fracturing

Currently, unconventional oil and gas fields employ volume fracturing technology, and temporary plugging and diversion techniques have become one of the main methods for increasing production. The Mixi coalbed methane block in Yibing has a formation vertical depth of 800-1000 meters and a relatively low average formation temperature of 30 degrees Celsius. The temporary plugging agents currently in use face challenges during reservoir stimulation, including difficulty in withstanding pressure differentials, poor degradability, and significant reservoir damage, resulting in unsatisfactory implementation effects. Therefore, the water-soluble temporary plugging agent RD-1 was selected as the preferred option. Laboratory performance evaluation experiments have demonstrated that this temporary plugging agent exhibits good sealing and degradation properties. Field trials have shown good temporary plugging and diversion effects, with noticeable pressure increase during plugging and significantly improved stimulation volume. It has demonstrated good applicability in coalbed methane volume fracturing, accumulating valuable experience for efficient development of this block.

Pressure Transient Solutions for Unbounded and Bounded Reservoirs Produced and/or Injected via Vertical Well Systems with Constant Bottomhole Pressure

Various analytical solutions for computing production and injection-induced pressure changes in aquifers and oil reservoirs have been derived over the past century. All prior solutions assumed a constant well rate as the boundary condition. However, in many practical situations, the fluid withdrawal from and/or injection into such subsurface reservoirs occurs with the aid of pump devices that maintain a constant bottomhole pressure in the well. Until now, how the well rate will decline over time, based on the pressure difference in the well relative to the initial reservoir pressure, could not be rapidly computed analytically (using the diffusivity as the key governing system parameter), because no concise expression had been derived with the boundary condition of a constant bottomhole pressure. The present study shows how the pressure diffusion equation can be readily solved for wells acting as sinks and sources with a constant bottomhole pressure condition. We consider both fractured and unfractured completions, as well as injection and production modes. The new solutions do not require an elaborate time-stepped pressure-matching procedure as in nodal analysis, the only other physics-based analytical method currently available to compute the well rate decline when a constant bottomhole pressure production system is used, which unlike our new method proposed here is limited to single well systems.

Internal flow stability analysis of vertical mixed-flow pump device based on EGT and FFT

With the purpose of researching the internal flow stability of the vertical mixed-flow pump device (VMFPD), the entire flow field was solved through the very large-eddy simulation (VLES) k- ω model and the internal flow characteristics of the pump device were quantitatively analyzed with the use of the energy gradient theory (EGT) along with the physical parameters of the flow field. The research elucidates the variety rule of the pressure along the VMFPD and the energy gradient function K as well as the time-frequency features of the pressure pulsation (PP) in the impeller and guide vane. The results demonstrate that the solid wall restriction of the guide vane and the impeller rotation cause a significant shift in the velocity and direction of the water flow. This causes a significant pressure difference between the water bodies, which makes it easier to create an unstable flow. The suction surface of the impeller blade possesses the great concentration of the area with energy gradient function K > 107, which is the critical area influencing the internal flow stability of the pump device.

On the impact of operating condition and testing environment on the noise sources in an industrial engine cooling fan

Engine cooling fan noise is a relevant issue for manufacturers. It is well known that both the operating point and testing environment can affect the noise generation mechanisms and, consequently, the measured noise may change. Therefore, these aspects are investigated on a reference industrial fan, for which experimental data exists, using high-fidelity numerical simulations based on the lattice-Boltzmann method. Two operating conditions, namely the free blowing and the maximum efficiency ones, and three testing environments are analyzed: (i) a conventional semi-anechoic room, (ii) an ideal free field environment, and (iii) a testing environment resembling an anechoic aeraulic facility. For cases (i) and (ii) no pressure difference across the fan is imposed, while, for case (iii), a pressure difference across the fan can be imposed. For the latter, the impact of a fully reflective and fully absorbing wall separating the two regions upstream and downstream of the fan is analyzed. At free blowing conditions, the flow over the blades is largely separated. When the blade passes through a blockage region, because of the presence of a honeycomb-like structure needed for structural purposes, it experiences a prominent loading hump. The far-field noise, at a listener located along the axis of rotation, is therefore highly tonal, with a clear peak at the blade passing frequency tone. When the same fan is tested in a free field environment, it is found that there is a difference in the acoustic pressure at higher harmonics of the blade passing frequency due to the presence of flow recirculations in the anechoic room. Placing a thin wall across the fan increases the mass flow rate, for a given rotational speed, which results in a more severe flow separation over the blades and, therefore a higher tone prominence at the blade passing frequency. If the thin wall is modeled as a sound-absorbing wall, there is a drop of the overall sound pressure level of about 2 dBA. When the fan is tested at its maximum efficiency, i.e., nonzero pressure difference across the fan, it is found that the blockage effect is less relevant. The main noise generation mechanism is the back-flow vortex induced by the pressure difference across the fan interacting with the blade tip leading edge.

Impact of Thickness of Pd/Cu Membrane on Performance of Biogas Dry Reforming Membrane Reactor Utilizing Ni/Cr Catalyst

The present study pays attention to biogas dry reforming for the purpose of producing H2. It is known that biogas contains approximately 40 vol% CO2, causing a decrease in the efficiency of power generation due to its lower heating value compared to natural gas, i.e., CH4. We suggest a hybrid system composed of a biogas dry reforming membrane reactor and a high-temperature fuel cell, i.e., a solid oxide fuel cell (SOFC). Since biogas dry reforming is an endothermic reaction, we adopt a membrane reactor, controlled by providing a non-equilibrium state via H2 separation from the reaction site. The purpose of the present study is to understand the effect of the thickness of the Pd/Cu membrane on the performance of the biogas dry reforming membrane reactor with a Pd/Cu membrane as well as a Ni/Cr catalyst. The impact of the reaction temperature, the molar ratio of CH4:CO2 and the differential pressure between the reaction chamber and the sweep chamber on the performance of the biogas dry reforming membrane reactor with the Pd/Cu membrane as well as the Ni/Cr catalyst was investigated by changing the thickness of the Pd/Cu membrane. It was revealed that we can obtain the highest concentration of H2, of 122,711 ppmV, for CH4:CO2 = 1:1 at a reaction temperature of 600 °C and a differential pressure of 0 MPa and using a Pd/Cu membrane with a thickness of 40 μm. Under these conditions, it can be concluded that the differential pressure of 0 MPa provides benefits for practical applications, especially since no power for H2 separation is necessary. Therefore, the thermal efficiency is improved, and additional equipment, e.g., a pump, is not necessary for practical applications.

Hypostomus plecostomus-inspired soft sucker to adsorb slippery tissues: a stabilizing post-valvular cavity and stiffness gradient materials provide excellent adsorption performance

The hard suckers commonly used in surgical operations often cause adsorption extrusion damage to the biological tissue. To tackle this problem, from the perspective of bionics, through in-depth observation and research on the special sucker adsorption process and adsorption mechanism of hypostomus plecostomus (HP), this paper proposes a bionic soft hypostomus plecostomus sucker (BSHPS) with a variable stiffness gradient structure with a good adsorption performance on soft moist irregular biological tissues. The BSHPS comprises a lip disc, a pre-valvular cavity, and a post-valvular cavity. Through the volume changes of the pre- and post-valvular cavities, a pressure difference is generated between the inside and outside of the sucker, enabling the lip disc to remain sealed. The experiments were carried out by an automatic tensile force measurement system equipped with a vacuum pump, and the results showed that in slippery environment, the adsorption performance of the BSHPS is improved by a maximum of 61.9% compared to that in dry environment. On a biological tissue surface, the adsorption force is as high as 13.7765 N. The most important advantage of the proposed BSHPS is that it can be firmly adsorbed the surface of soft moist irregular biological tissues, effectively slowing down or avoiding adsorption extrusion damage to the biological tissue. Therefore, the BSHPS is expected to have good application prospects in modern surgical medicine.

Pressure-Relieving Effect of Different Insole Top Covers in People with Diabetes at High Risk of Foot Ulceration.

Pressure-relieving footwear helps prevent foot ulcers in people with diabetes. The footwear design contributes to this effect and includes the insole top cover. We aimed to assess the offloading effect of materials commonly used as insole top cover. We measured 20 participants with diabetes and peripheral neuropathy for in-shoe peak pressures while walking in their prescribed footwear with the insole covered with eight different materials, tested in randomized order. Top covers were a 3 mm or 6 mm thick open or closed-cell foam or a 6 mm thick combination of open- and closed-cell foams. We re-assessed pressures after one month of using the top cover. Peak pressures were assessed per anatomical foot region and a region of interest (i.e., previous ulceration or high barefoot pressure). Walking comfort was assessed using a 10-point Likert scale. Mean peak pressure at the region of interest varied between 167 (SD:56) and 186 (SD:65) kPa across top covers (p < 0.001) and was significantly higher for the 3 mm thick PPT than for four of the seven 6 mm thick top covers. Across 6 mm thick top covers, only two showed a significant peak pressure difference between them. Over time, peak pressures changed non-significantly from -2.7 to +47.8 kPa across top cover conditions. Comfort ratings were 8.0 to 8.4 across top covers (p = 0.863). The 6 mm thick foams provided more pressure relief than the 3 mm thick foam during walking in high-risk people with diabetes. Between the 6 mm thick foams and over time, only small differences exist. The choice of which 6 mm thick insole top cover to use may be determined more by availability, durability, ease of use, costs, or hygienic properties than by superiority in pressure-relief capacity.

Optimal control for district heating systems based on imbalance analysis of pipe networks

In district heating (DH) systems, the transmission and distribution process occupy large amount of energy consumption. Hydraulic and thermal imbalance in pipe networks often lead to uneven heating, affecting user comfort and resulting in energy losses. To solve this problem, this study investigates the root causes of hydraulic and thermal imbalances in DH systems. Key factors have been identified such as initial flow rates, initial loads, and positions in the network of end-users. And the relationship between hydraulic and thermal imbalances have been analyzed. Building on this analysis, we further propose a novel strategy for differential pressure set-point adjustment. This strategy is developed based on a quantitative understanding of the flow rate changes and positions of end-users. It aims to rectify imbalances efficiently, thus enhancing the overall performance of the network. The effectiveness of the proposed strategy is validated through comparative analysis with the conventional constant differential pressure (CCDP) control strategy and an exist variable differential pressure (VDP) control strategy. Results demonstrate significant improvements in network performance, including enhanced stability and reduced energy losses. The proposed strategy reduces the average pressure difference in the main pipe by up to 10.9 %, improves the supply and return temperature difference by 10.9 %, and maintains valve openings above 70 % during peak periods. Additionally, it achieves 23.5 % energy savings in transmission and distribution, highlighting its potential to enhance system performance and efficiency. In addition, this strategy is more in line with the actual situation of end-user demand change for valve adjustment.

Internal flow and vibration characteristics of axial flow check valves based on fluid-structure interaction analysis

Axial flow check valves are primarily employed to regulate the unidirectional flow of fluids within pipelines, preventing backflow or reverse flow. The design of this type of check valve ensures its opening in the direction of fluid flow and closing in the case of reverse flow, thereby ensuring that fluid within the pipeline system can only move in the predetermined direction. This paper establishes a three-dimensional physical model of the axial flow check valve with the length of 2050 mm, the height of 2200 mm and the inlet/outlet diameter of 1716 mm. Dynamic characteristics of the flow field during the closing process of axial flow check valve under different pressure difference were studied using dynamic mesh technology and User Defined Function. The vibration of the valve stem of the axial flow check valve was predicted and analyzed through fluid-structure coupling. Additionally, a fluid-structure coupled approach is employed to predict and analyze the vibration of the valve stem in axial flow check valves. The results indicate that with an increase in the pressure difference at the inlet and outlet, the time required for the check valve to close decreases, leading to an acceleration in the valve disc’s velocity. Simultaneously, the fluid forces exerted by the flow field on the valve stem the increase, resulting in more significant vibrations. Among these vibrations, the first three natural modes have the most substantial impact on the valve stem. To prevent damage to the valve stem, efforts should be made to minimize the influence of these first three modes on axial flow check valves. This study provides valuable recommendations and support for preventing damage to the valve stem in operational scenarios involving axial flow check valves.

Experimental Investigation on Leakage and Frictional Heat Generation Characteristics of Low Hysteresis Brush Seals

Abstract Low hysteresis brush seals are frequently utilized in high-temperature, high-pressure, and high-speed environments. It is crucial to note that the high-speed rotor will contact the bottom end of the bristles, generating a significant amount of frictional heat. This heat can directly impact the sealing performance and service life, and high temperatures can exacerbate the frictional heat. This paper presents the cyclical testing of the low hysteresis brush seal with increasing and decreasing speed at different pressure differences and temperatures. The study focuses on the leakage characteristics, hysteresis effect and the temperature-rise of the bottom end of the bristles caused by frictional heat. The findings indicate that higher temperatures result in increased leakage, stronger hysteresis effects, and lower temperature-rise. Additionally, as the speed exceeds 6000rpm, the temperature-rise increases more rapidly due to frictional heat. During the speed decrease stage, the temperature-rise decreases sharply at first and then gradually decreases until it is almost unchanged. The hysteresis effect results in a lower temperature-rise during the speed-decrease stage compared to the speed-increase stage. The low hysteresis structure can effectively reduce hysteresis effect compared with the conventional brush seal. However, this structure may result in larger leakage. To minimize leakage, it is necessary to select a more suitable size for the pressure relief chamber. Furthermore, the low hysteresis brush seal exhibits a lower friction temperature-rise compared to the conventional one, which is beneficial to the service life of the brush seal.

Measurement and prediction of void fraction and pressure drop during air drying process of wet particle packed bed

This study aimed at development of a pressure drop prediction method at a drying process by flowing air through a wet particle packed bed saturated with distilled water. At first, the pressure drop measurement during the drying process of the wet particle packed bead of glass sphere was carried out, and a method for predicting the pressure difference of the bed was proposed by investigating the effect of liquid saturation on the bed void fraction. It was clarified that the effect could be predicted by a simple model by considering liquid bridges formed between particles. Next, the liquid saturation when the measured pressure difference suddenly decreased was investigated as the residual saturation. The value was like that of past research. Finally, considering the effect of liquid saturation on the bed void fraction and the influence of the residual saturation on the relative permeability of liquid phase, more than 90 % of all pressure drop data could be predicted with an error of less than ±15 %. Furthermore, in the range where the gas-phase velocity was large, it was important to predict the pressure difference considering the change of the bed void fraction and the residual saturation.

Effect of health extension workers-led home-based multicomponent intervention on blood pressure reduction among hypertensive patients in rural districts of northwest Ethiopia: a cluster-randomised controlled trial.

To evaluate effects of health extension workers-led home-based multicomponent intervention on blood pressure change in hypertensive patients in rural districts of northwest Ethiopia. Two-arm cluster randomised controlled trial was conducted. Hypertensive patients' age ≥25 years were included. 20 clusters or kebeles with 456 participants were randomly assigned to the intervention group (10 clusters with 228 participants) and the control group (10 clusters with 228 participants). Participants in the intervention kebeles received health extension workers-led home-based multicomponent interventions every other month for 40-60 min for 9 months. The primary outcomes were the differences in mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) changes from baseline between patients in the intervention and control groups. Intention-to-treat analysis was used for the primary analyses. Linear mixed effect model was used to evaluate the intervention's effect on change in mean SBP and DBP. Effect sizes of mean difference and relative benefit increase were used. At 9 months, the mean SBP decreased by 15.8 mm Hg (95% CI: 13.5, 18.1) in the intervention and 10.8 mm Hg (95% CI: 8.7, 12.9) in the control groups; with a 5.0 mm Hg (95% CI: 1.9, 8.1) greater reduction in the intervention group. The mean DBP decreased by 12.1 mm Hg (95% CI: 10.6, 13.5) in the intervention and 8.4 mm Hg (95% CI: 7.0, 9.8) in the control group. The proportion of optimal blood pressure control was higher in the intervention group (45.8%) than the control group (28.2%) with percentage difference of 17.6% (95% CI: 8.5, 26.7). Health extension workers-led home-based multicomponent intervention has resulted significant reduction of blood pressure and achieved a higher proportion of optimal blood pressure control. This strategy is effective, but further research is needed to determine its cost effectiveness for scaling up and integrating in primary care settings. The trial is registered with Pan African clinical trial registry (PACTR202102729454417).

Validation of combiomed hipermax-BF model A7101 automatic oscillometric upper-arm sphygmomanometer in general population: AAMI/ESH/ISO universal standard (ISO 81060-2:2018/Amd 1:2020).

This study evaluates the accuracy of the Hipermax-BF model A7101 (Combiomed, Havana, Cuba) automatic oscillometric upper-arm sphygmomanometer for office and home use in general population as part of the HEARTS in the Americas initiative. The research was developed according to the Universal Standard AAMI/ESH/ISO ISO 81060-2:2018/Amd 1:2020. The subjects were recruited according to the requirements of age, gender, blood pressure values and upper-arm circumference. The same upper-arm sequential blood pressure measurement method was used. For measurements with the device under test, the 2-piece cuff from 22-44 cm limb circumference range was used. 92 subjects were recruited and 85 were analyzed. Mean age was 44.8 ± 14.7 years, mean upper-arm circumference was 32.3 ± 6.2, and 56.5% were female. For Validation Criterion 1, the mean value ± standard deviation of the differences in readings between the device under test and the reference device was 1.2 ± 4.9/0.8 ± 4.9 mmHg (systolic/diastolic). For both pressures, in criterion 1 the standard requires a mean value of the differences ≤ ± 5 mmHg and a standard deviation ≤ ± 8 mmHg. For Validation Criterion 2, the standard deviation of the mean blood pressure differences per subject was 4.2/4.2 mmHg (systolic/diastolic). According to Table 1 of criterion 2, for the mean values of 1.2/0.8 mmHg (systolic/diastolic), the maximum allowable standard deviation had to be < 6.84 for systolic and < 6.89 for diastolic pressure. The Combiomed Hipermax-BF A7101 automatic sphygmomanometer meets the requirements of the AAMI/ESH/ISO Universal Standard (ISO 81060-2:2018/Amd 1:2020) in the general population.

Simulation of vacuum membrane desalination within an enhanced design of compact solar water heaters

Vacuum Membrane Distillation stands out as a solar desalination method utilizing membrane pressure differentials to evaporate seawater and collect it as fresh water. On the other hand, the new design of compact (or integrated) solar water heaters can be very suitable for Vacuum Membrane Distillation use. In the new design of solar system, its upper part, which is under buoyancy pressure, can have a very suitable space for installing the Vacuum Membrane Distillation system. The purpose of this research is to simulate the proposed design and a dynamic time-domain model was developed for comprehensive simulation, encompassing absorber plate characteristics, collector dimensions, mass flow rate, vacuum pressure reduction, the influence of increasing membrane rows, and seawater concentration. Simulation results showcase the system’s potential, yielding 57.12kg/m2/day of freshwater daily with an average gain output ratio exceeding 1.1. The estimated water production cost is 0.039USD.L-1, along with the generation of 4.3kg.kg/m2/day of chlorine and 0.037g.kg/m2/day of bromine from Mediterranean seawater. For super saline water, the projections indicate a daily production of 104.46kg.kg/m2/day of freshwater with a production cost of less than 0.01 USD/L, a GOR of 1.7, and a daily production of 37.8kg.kg/m2/day of chlorine for a collector area of 6 m2. These outcomes underscore the efficiency and economic viability of the proposed design, positioning it as a promising solution for seawater desalination challenges.

Optical study on spray mixing, flame propagation and jets evolution within visible methanol active pre-chamber for turbulent jet ignition

Methanol spray impingement, mixing, flame propagation and jet evolution within the narrow-confined active pre-chamber (APC) with complex walls were experimentally observed by optical method for the first time. The effects of injection pressure and duration was investigated on an actual-geometry optical APC assembled in constant volume combustion chamber (CVC). Exploration on APC internal processes within static environments forms the basis for optimization of APC and analysis of jet formation. Mie scattering coupled with flame natural luminosity imaging were used to record spray mixing and combustion. The results show that in the APC with narrow-confined space, methanol spray undergoes three wall impingements, inducing a tumble that promotes mixing. High injection pressure enhances rapid spray tip penetration, while long injection duration slows methanol diffusion. In longer injection duration cases, the spray tip after the third impingement interferes with subsequent sprays. For higher injection pressure, this interference occurs in the APC cone section due to a larger spray cone angle, whereas for lower pressure, it happens in the APC duct section. Higher injection pressure also causes more spray to impact the APC bottom after the first wall impingement, hindering flame acceleration in the duct section. Irregular flame propagation is observed in the APC cone section due to wider space and uneven mixture conditions, while the convergent geometry from the APC throat to the duct section significantly accelerates flame propagation. The APC jet appears due to the pressure difference between the APC and the main chamber, with the brightness and length of the visible flame jet increasing with APC flame luminosity and pressure difference. A Mach ring structure is observed initially, but the jet velocity decreases as the Mach ring disappears during the APC inner flame extinguishing process. Through this study, the actual spraying and combustion process in APC is experimentally captured and revealed, which are an important contribution for APC optimization and development.