Maximum Static Pressure Research Articles

Numerical Simulation of Axial Inflow Characteristics and Aerodynamic Noise in a Large-Scale Adjustable-Blade Fan

Numerical simulation are conducted to explore the characteristics of the axial inflow and related aerodynamic noise for a large-scale adjustable fan with the installation angle changing from −12° to 12°. In such a range the maximum static (gauge) pressure at the inlet changes from −2280 Pa to 382 Pa, and the minimum static pressure decreases from −3389 Pa to −8000 Pa. As for the axial intermediate flow surface, one low pressure zone is located at the junction of the suction surface and the hub, another is located at the suction surface close to the casing position. At the outlet boundary, the low pressure is negative and decreases from −1716 Pa to −4589 Pa. The sound pressure level of the inlet and outlet noise tends to increase monotonously by 11.6 dB and 7.3 dB, respectively. The acoustic energy of discrete noise is always higher than that of broadband noise regardless of whether the inlet or outlet flow surfaces are considered. The acoustic energy ratio of discrete noise at the inlet tends to increase from 0.78 to 0.93, while at the outlet it first decreases from 0.79 to 0.73 and then increases to 0.84.

Numerical Simulation of Flow between Two Parallel Co-Rotating Discs

The study of fluid flow between two rotating discs aims to predict flow characteristics. In this paper numerical simulation is used to investigate axisymmetric swirling flow between two parallel co-rotating discs. Methodology entails, firstly, inputing parameters from CFD software are into previos study developed dimensionless radial velocity model for flow between two discs to obtain dimensional radial velocity of the model. Secondly, previous study parameters are used to perform numerical simulation on laminar and turbulent flows between two parallel co-rotating discs. The numerical simulation results are compared to previous study results. Then comparative numerical simulations was carried out on laminar and turbulent flows using CFD software. Results obtained showed that for the this study dimensional radial velocity and previous study dimensionless radial velocity, radial velocity distribution increase proportionately from the disc surface at 0m/s to 2208.00m/s and 0 to 0.0002396 respectively, at the domain centre. And both results satisfy initial inlet and boundary conditions with resultant parabolic profiles. In the study, it is shown that turbulent flow radial velocity profile is smoother than for laminar flow. The radial velocity increases from 0 at the walls to 0.15m/s before decreasing to - 0.2m/s at the mid-centre for laminar flow while for turbulent flow the radial velocity intitially increases from 0 at the walls to 0.15m/s before decreasing to -0.06m/s at the discs centre; while for laminar flow, swirl velocity decrease from approximately 2.55m/s to 0.55m/s and for turbulent flow the swirl velocity decrease from approximately 2.84m/s to 1.62m/s. The turbulent flow swirl velocity profile seen to be smoother than for laminar flow around the discs centre. The study further showed that for fluid near the discs surfaces radial velocity net momentum is radially towards the outlet with flow laminar in the boundary layer region and the velocity turbulent towards the domain centre. For static pressure, laminar flow maximum and minimum static pressure 2.48pa and -0.033pa respectively, while for turbulent flow maximum and minimum static pressure were 0.00 and -0.0024pa. The developed previous study model can therefore be used to predict radial velocity distribution between steady axisymmetric flow between two parallel co-rotating discs.

대규모 와 모사에 의한 1피치 소형 나선형 축류홴의 운전부하에 따른 난류유동장 구조에 대한 연구

The unsteady-state, incompressible and three-dimensional large eddy simulation (LES) was performed to analyze the structure of turbulent flow fields according to the operating load of one-pitched small-size helical axial fan (SSHAF). The static pressure coefficient distribution according to the flow coefficient of SSHAF does not include stall, and the maximum static pressure efficiency is about 13% higher than that of conventional small-size axial fan. The typical axial flow developed downstream of SSHAF decreases with increasing operating load, and external axial flow outside the fan center develops radially. There is a reverse flow in the internal flow developed downstream from the hub of SSHAF. As the operating load increases, the absolute velocity of the reverse flow increases and its space gradually increases to approach the hub side. Even with increasing operating load, the flow that develops downstream of SSHAF does not include full radial flow, unlike conventional small-size axial fan.

Preventing Air Pollution Connected to the Explosion of Different Types of Flours in Dedicated Storage and Transportation Systems

Air pollution, caused by explosion and/or fire of flammable substances, is typical for the majority of technological processes, e.g., flour storage and transportation systems in the food industry. If explosion venting systems are not properly designed, an explosion might lead to many causalities, substantial losses, and significant release of combustion products into the ambient atmosphere. This article presents a study on four selected types of flours: rice flour, oat flour, cornmeal, and chickpea flour. The chosen ignition and explosion indices were determined (heat of combustion, pmax, (dp/dt)max) and TGAs were conducted. The results were used to calculate the explosion venting area according to EN 14491. Despite similar origins, samples were characterized by slightly different courses of explosion, leading to significant differences in required venting areas. Chickpea dust was found to be the most distinguishing sample with the highest values of pmax, (dp/dt)max, and KSt recorded (7.7 bar, 313.08 bar/s, and 85 mbar/s, respectively). To avoid structure failure resulting in the emission of pollutants into the atmosphere, a change in the stored flour type should be preceded by a revision of safety measures taken, as the required vent area might differ significantly depending on the KSt, L/D ratio, and desired maximum static pressure.

Cough, sniff and maximal static pressure patterns in spinal muscular atrophy

In spinal muscular atrophy (SMA), respiratory muscles are heterogeneously involved with a weakness of the intercostal muscles, possibly of the abdominal wall muscles, and a relatively spared diaphragm, resulting in cough impairment. An abnormal inspiratory cough phase pattern has been reported in SMA II and III. This short communication analyzed the esogastric pressures during voluntary cough in 49 SMA II and III patients. Four different patterns of coughing, reflecting an increasing degree of respiratory muscle weakness, were identified. The “mild weakness” profile was observed mainly in SMA III, while the “severe weakness” profile, which seems to correspond to the absence of abdominal muscle activity, was observed only in a few patients with SMA II. The cough profiles of 6 patients are presented together with their sniff and maximal static pressures measurements. Different esogastric pressure patterns were observed during these forceful maneuvers, suggesting variable involvement of the intercostal and abdominal muscles, and diaphragm during the evolution of SMA II and III.

Effects of multi inlet guide channels on the performance of a cyclone separator

Widely usage of cyclone separator, especially in industries, makes it not only one of the most interesting subject of papers nowadays, but research and development of it should follow necessarily. The unusual design of this cyclone makes it more useful and functional. This design causes to form a strong vortex flow in the cyclone, which increases the centrifugal force acting on each particle separately, increases the collection efficiency as well as decrease the cut-off diameter. So, simulation of the turbulent 3D flow has been done with the finite volume method and RSM turbulence model. The major contribution of the total cyclone pressure drop has occurred in the upper section of cyclone and guide channels, which increase the entered velocity to the main body of the cyclone. The results represent a uniform distribution of static pressure patterns at cyclone heights for each velocity as well as a uniform flow field pattern in the cyclone. In comparison with usual cyclones, because of the special design of inlet guide channels, not only the entrance velocity of flow to the main cyclone body has been increased, but the inappropriate moving of flow after the entrance to the main body toward the cyclone's top section doesn't occur. The cut-off diameter reduced by 0.2 μm in comparison with the usual cyclone separator. With 20% increasing in the inlet velocity, the maximum static pressure in all sections increases by approximately 41%, while the 20% reduction in the inlet velocity, reduces the maximum static pressure in all sections by 55% to 58%. A 20% increase in velocity compared to the initial velocity of 8.809 m/s, reducing the cut-off diameter to approximately 0.6 μm. A 20% decrease in inlet velocity, the separation efficiency is reduced in general and increases the cut-off diameter to 0.9 μm. The Stokes number smaller than 1, should be expressed as an appropriate criterion to select between two main aspects of Eulerian-Lagrangian and Eulerian- Eulerian approach. Reducing the inlet velocity amplifies the assumption of the Eulerian-Lagrangian aspect instead of the Eulerian- Eulerian approach. About the Euler number, the 20% increasing the inlet velocity has increased the pressure drop in the cyclone, but the inlet velocity seems to be more effective on the flow kinetic energy rather than an influence on the pressure drop.

In silico investigation of sneezing in a full real human upper airway using computational fluid dynamics method

Background and objectiveSneezing is one of the most critical conditions that can occur in the human upper airway. As some reports confirm the injury to the human upper respiratory airway while sneezing. Therefore, the accurate study of the distribution of pressure and velocity in this case is of great importance. MethodsIn the present study, using a real human upper airway model, the pressure and velocity of the airflow generated in the tract during the sneezing have been investigated. Also, considering the results from a spirometer device as a boundary condition in the simulation process, the calculations have become reliable. ResultsAccording to the results, during sneezing, taking into account that the average outlet flow rate from the mouth is 4.79 L/s, the velocity of outlet airflow from the mouth and nose reaches 5.3 and 8.4 m/s, respectively. These values were 11.5 and 19, respectively, when the desired maximum flow rate was 10.58 L/s. It can be concluded that the increasing of trachea flow rate, leads to higher percentage of the outlet flow rate from the nose . The highest average pressure and velocity have been occurred in the trachea. Among other salient results of this report, increased average static pressure of larynx to approximately 10 kPa can be pointed which indicates that this area is critical so that the thyroid cartilage defect is likely to occur. It is also noteworthy that the increase of speed at nasopharynx is up to 125 m/s so that the cross-section changing in this area leads the fluid acts as a jet flow. Due to the specific geometry of the nasal cavity, some streams similar to poor shocks are formed, these shocks get stronger by increasing of the flow rate. The thyroid cartilage and nasal cavity are exposed to maximum static pressure extremums, respectively. ConclusionsWe introduced a model simulating a normal sneezing for two cases using a healthy 30-year-old male person. We believe that the model should be applied for different persons and an atlas of data could be obtained from different cases. This may help the medical system to have more data about the sneezing process.

Static and dynamic forces in the incudostapedial joint gap

Dynamic pressure at the tympanic membrane is transformed and subsequently transferred through the ossicular chain in the form of forces and moments. The forces are primarily transferred to the inner ear. They are transferred partly to the stapedial annular ligament which exhibits non-linear behavior and stiffens for larger static forces. In unventilated middle ears, static pressure is additionally transferred to the ossicles. The purpose of this study was to measure the force inside the ossicular chain as a physiological parameter. We determined the forces which act for dynamic sound transmission and for static load on the ossicular chain. The study is the first one which introduces these forces. The static forces have direct impact on clinically relevant questions for middle ear reconstructions with passive or active prosthesis. The dynamic forces have an impact on the development of middle ear sensors. Quasi-static forces in the incudostapedial joint (ISJ) gap were measured with two different sensor types in 17 temporal bones. The sensing elements, a single crystal piezo and a strain gauge element for validation, were bonded to a thin flexible titanium plate and encapsulated in a titanium housing to allow the acquisition of the applied force signal inside the ossicular chain. Dynamic forces were measured in 11 temporal bones with the piezo sensor. We measured a static force of 23 mN in the ISJ after sensor insertion. The mean force for dynamic physiological acoustic excitation from 250 Hz to 6 kHz was 26 μN/Pa. If the tympanic membrane is loaded with a static pressure, the static force in the ISJ increases up to 1 N for a maximum static pressure load scenario of 30 kPa.

Contributed Review: Culet diameter and the achievable pressure of a diamond anvil cell: Implications for the upper pressure limit of a diamond anvil cell.

Recently, static pressures of more than 1.0 TPa have been reported, which raises the question: what is the maximum static pressure that can be achieved using diamond anvil cell techniques? Here we compile culet diameters, bevel diameters, bevel angles, and reported pressures from the literature. We fit these data and find an expression that describes the maximum pressure as a function of the culet diameter. An extrapolation of our fit reveals that a culet diameter of 1 μm should achieve a pressure of ∼1.8 TPa. Additionally, for pressure generation of ∼400 GPa with a single beveled diamond anvil, the most commonly reported parameters are a culet diameter of ∼20 μm, a bevel angle of 8.5°, and a bevel diameter to culet diameter ratio between 14 and 18. Our analysis shows that routinely generating pressures more than ∼300 GPa likely requires diamond anvil geometries that are fundamentally different from a beveled or double beveled anvil (e.g., toroidal or double stage anvils) and culet diameters that are ≤20 μm.

The effect of the length to diameter ratio on capillary discharge plasmas

The capillary geometry of discharge plasma sources determines the performance of capillary plasma generators. In this research, 16 types of generators with different geometric sizes and aspect ratios (the length divided by the diameter of the capillary, ranging from 0.67 to 22) were designed. Plasma parameters, including the temperature, static pressure, and velocity, were calculated and analyzed. The results show that the maximum temperature of the plasma decreased with increasing capillary aspect ratios. However, there was a difference between the temperature distributions above and below an aspect ratio threshold of 8.67. The simulations suggest that the aspect ratio threshold of the static pressure for generating shock waves is 15.33. For aspect ratios lower than this value, the maximum static pressure increased with increases in the aspect ratio. Otherwise, a shock wave would be generated, and the distribution of the static pressure would be consistent with distribution 2 (with a shock wave near the nozzle). The maximum velocity decreased as the capillary aspect ratios increased, with a threshold of 8.67. Since the plasma parameters were exponential functions of the aspect ratios, distribution and variation trends of the plasma parameters for different aspect ratios are proposed. These can be used to adjust the electrothermal plasma parameters and to design plasma generators.

Optimization Study of the Dump Diffuser in Gas Turbine to Reduce Pressure Loss

As a key component-connecting compressor and the entrance of combustion chamber, the diffuser is able to increase the pressure and slow down the airflow in order to promote efficient combustion as well as avoid a large amount of pressure loss. In this paper, experimental investigation and numerical studies have been carried out to understand the effects of air bleeding from dump region and dump gap ratio on the total pressure loss and static pressure recovery of the dump diffusers. The ultimate objective is optimizing the dump diffuser design to get the maximum static pressure recovery and minimum total pressure loss. A simplified test model is used to study the effect of the air bleeding from the outer dump region and the dump gap ratio on the total pressure loss and static pressure recovery in the dump diffuser. The impact of the dump gap ratio in the performance of the dump diffusers has also been discussed. Nearly all the pressure raise occurs in the prediffuser, and most of the total pressure loss occurs in the dump region. For the recirculating area in the dump region, the controllable vortex can be introduced. Bleeding air from the outer dump region can improve the velocity distribution near the flame tube. The results show that when 0.4% of the air is bled from outer dump region, the performance of the dump diffuser is optimal. Hence, the controllable vortex method is effective for improving the performance of the dump diffuser.

Predictive equations for respiratory muscle strength by anthropometric variables.

This study proposes predictive equations of respiratory muscle strength by the variables such as body weight and body mass index (BMI=weight/height2 ). This is a cross-sectional study, and the evaluation was made by the test of maximum static respiratory pressures (MIP and MEP) according to standard protocol of the Brazilian Society of Pneumology and Tisiology. For data analysis, the following three models of linear regression were adjusted: age, age/weight, age/BMI. The software used in the analysis was the R version 3.2.1. Of the 353 subjects evaluated (229 women and 124 men), 109 subjects were normal weight, 101 subjects were overweight and 143 subjects were obese. The BMI average of the individuals was 31.42±10.26kg/m2 and age 46.26±16.47years. The two statistical models that considered the variables weight and BMI had the R2 value of 29.86% for MEP and 21.77% for MIP when the weight was the predictive variable and 21.33% for MIP and 28.38% for MEP when the variable was BMI. It was found with the adjusted models that there was a considerable gain in the predictive quality of the models for MEP and MIP adding weight or BMI, without significant difference between both.

PECULIARITIES OF THE CHANGE IN THE RESPIRATORY MUSCLES STRENGTH IN PATIENTS WITH 2 TYPE OF DIABETES MELLITUS COMPLICATED BY THE DIABETIC FOOT SYNDROME

The relationship between cardiorespiratory disorders and diabetic foot syndrome has not been adequately studied. In particular, there is no information on the strength of the respiratory muscles in this category of patients. The purpose of the study: to determine the presence of respiratory muscles weakness in patients with type 2 diabetes mellitus complicated by diabetic foot syndrome. Materials and methods. 72 patients were examined, 16 of them with type 2 diabetes mellitus complicated by the neuroischemic type of diabetic foot syndrome I-IV st. Wagner made up the first (main) group. The second group (comparisons) included 29 patients with type 2 diabetes mellitus not complicated by diabetic foot syndrome. The third group (comparisons) were 27 patients without diabetes. The groups were randomized by sex and exclusion criteria. Determination of the strength of the respiratory muscles was carried out by measuring the maximum static pressure levels at the mouth level that the patient created during maximum inspiration and maximum expiration in closed airways. Results. The forces of the respiratory muscles with inspiratory effort in patients with type 2 diabetes mellitus complicated by diabetic foot syndrome was reduced by 18.5 cm of water column (p <0.01) compared with diabetic patients without diabetic foot syndrome and by 17.3 cm water column (p <0.01) compared with patients without diabetes. The expiratory effort showed a decrease in the forces of the respiratory muscles in the patients of the first group by 49.4 cm of water column (p <0.01) compared to patients of the second group and by 27.4 cm of water column (p <0.05) compared to patients third group. In women with diabetic foot syndrome, the inspiratory muscular forces was reduced in comparison with patients without diabetic foot and without diabetes syndrome by 27.1 (p <0.01) and by 23.3 (p< 0.05) cm of water column, respectively. In men with diabetic foot syndrome, the same index was lowered by 13.9 (p> 0.05) and 17.7 (p <0.05) cm of water column, respectively, compared to the second and third groups, respectively. The expiratory effort revealed a decrease in the forces of the respiratory muscles in men in all groups in approximately the same range, without a significant difference between the groups. In women with diabetic foot syndrome, there is a marked decrease in the strength of the expiratory muscles: by 48.4 cm of water column (p <0.01), compared to women of the second group and by 20.6 cm of water column (p <0.05) patients of the third group. Conclusions. Patients with diabetes mellitus complicated by diabetic foot syndrome showed a decrease in the strength of inspiratory and expiratory muscle. In women with diabetic foot syndrome, there is a more pronounced decrease in the strength of the respiratory muscles during exhalation compared to men with this pathology.

Pressure characteristic analysis and estimation of effective length of a hybrid diffuser and modified hybrid diffusers

In this paper, performance simulation of a hybrid diffuser, hybrid diffuser with suction and hybrid diffuser with fence have been carried out. The two-dimensional steady differential equations for conservation of mass and momentum have been solved for the Reynolds number ranging from 100 to 600. During the simulation, a fixed aspect ratio of 2 and a fixed value of half divergence angle of 3.5° have been considered for all the diffuser geometries. At the inlet, fully developed velocity profile has been used. The effect of Reynolds number on average static pressure have been studied in detail, and compared between three diffuser geometries. The effective diffuser lengths for achieving maximum average static pressure at the diffuser exit have been computed for the considered Reynolds numbers.

Effects of Resistance Training of Peripheral Muscles Versus Respiratory Muscles in Older Adults With Sarcopenia Who are Institutionalized: A Randomized Controlled Trial.

This study compares the effects of two resistance training programs in peripheral and respiratory musculature on muscle mass and strength and physical performance and identifies the appropriate muscle mass parameter for assessing the intervention effects. Thirty-seven institutionalized older Spanish adults with sarcopenia were analyzed: control group (n = 17), respiratory muscle training group (n = 9), and peripheral muscle training group (n = 11). Measured outcomes were appendicular skeletal muscle mass (ASM/height2, ASM/weight, and ASM/BMI), isometric knee extension, arm flexion and handgrip strength, maximal inspiratory and expiratory pressures, and gait speed pre- and postintervention. Trained groups participated in a 12-week program and improved in maximum static inspiratory pressure, maximum static expiratory pressure, knee extension, and arm flexion (p < .05), whereas nonsignificant changes were found in gait speed and ASM indexes pre- and postintervention in the three groups. In conclusion, resistance training improved skeletal muscle strength in the studied population, and any ASM index was found to be appropriate for detecting changes after physical interventions.

Intelligence design method for three-dimensional vaned diffusers in a centrifugal compressor

This paper presents a multi-objective optimization-based intelligence design method for the design of the three-dimensional vaned diffuser for a given centrifugal compressor. This design method consists of three-dimensional vaned diffuser design model and its solving strategy. The three-dimensional vaned diffuser design model consists of the diffuser geometry mathematical model, performance evaluation model, objective equation, and design space. The diffuser geometry is described by the mathematical model of the meridional configurations and vane camber, trailing edge lean, and thickness. The generic design space is determined through literature statistical investigation. An NSGA-II multi-objective optimization algorithm, utilized to solve the three-dimensional vaned diffuser design model, directs the diffuser geometry variables to achieve the maximum stage isentropic efficiency and static pressure ratio at the design point within the design space automatically and intelligently. The presented three-dimensional vaned diffuser design method is demonstrated using a case test for a centrifugal impeller. The convergence of evolutionary solving for this three-dimensional vaned diffuser model is analyzed in detail, which provides the convergence reference for engineering applications. Three representative three-dimensional vaned diffusers on Pareto front are utilized to check the diversity of geometry shape and overall range performance characteristics. The results show that the three-dimensional vaned diffuser design method established here has excellent potential in automated design and maximizing stage performance. The method reported here could provide a valuable reference for the intelligent design of radial turbomachinery diffusers.

Fan and Ventilation Rate Monitoring of Cage-Free Layer Houses in California

Abstract. Ventilation rates were continuously monitored from 1 March 2012 to 13 May 2013 in two cage-free layer houses in California. The average number of brown Lohmann laying hens in each house was 33,300. Temperature, relative humidity, static pressure, and running status of 48 ventilation fans were continuously monitored and recorded every minute. Regression models were developed to relate house temperature and ventilation rate to inlet air temperature and to relate airflow rate to building static pressure (R2 = 0.98). Results showed that the daily mean ventilation rate per hen ranged from 1.91 to 8.72 m3 h-1 hen-1, averaging 4.49 ±1.53 m3 h-1 hen-1. The standard uncertainty of daily mean ventilation rate was determined to be 3.7%. The 91 cm and 130 cm fans were found to perform at 82% and 63% of the manufacturer-rated airflow rates, respectively. Minimum and maximum static pressures were 11.0 and 50.6 Pa, respectively, corresponding to 2 and 16 running tunnel fans. When the house temperature exceeded 30°C, an evaporative cooling system was activated, which could reduce the inlet air temperature by 6.3°C and concurrently increased the indoor air humidity ratio by 3.4 g per kg dry air. Cooling pad efficiency was 66%. The sidewall fans and tunnel fans were operated at 65% and 20%, respectively, of the total time when layers occupied the houses. A new rational formula for calculating dry base ventilation rate was developed based on the ratio of water vapor volume to moist air volume. The developed models and data collected in this research can be used to calculate the ventilation rates in cage-free layer houses to ensure the healthy conditions needed for laying hens. The models and data can also be used in the design of cage-free houses and in calculating emissions of air pollutants from these houses. Keywords: Cage-free laying hen house, Fan curve, Static pressure, Ventilation.

Investigation on a vertical radial flow adsorber designed by a novel parallel connection method

Abstract Due to the increasing global demand for industrial gas, the development of large-scale cryogenic air separation systems has attracted considerable attention in recent years. Increasing the height of the adsorption bed in a vertical radial flow adsorber used in cryogenic air separation systems may efficiently increase the treatment capacity of the air in the adsorber. However, uniformity of the flow distribution of the air inside the adsorber would be deteriorated using the height-increasing method. In order to reduce the non-uniformity of the flow distribution caused by the excessive height of adsorption bed in a vertical radial flow adsorber, a novel parallel connection method is proposed in the present work. The experimental apparatus is designed and constructed; the Computational Fluid Dynamics (CFD) technique is used to develop a CFD-based model, which is used to analyze the flow distribution, the static pressure drop and the radial velocity in the newly designed adsorber. In addition, the geometric parameters of annular flow channels and the adsorption bed thickness of the upper unit in the parallel-connected vertical radial flow adsorber are optimized, so that the upper and lower adsorption units could be penetrated by air simultaneously. Comparisons are made between the height-increasing method and the parallel connection method with the same adsorber height. It is shown that using the parallel connection method could reduce the difference between the maximum and minimum radial static pressure drop by 86.2% and improve the uniformity by 80% compared with those of using the height-increasing method. The optimal thickness ratio of the upper and lower adsorption units is obtained as 0.966, in which case the upper and lower adsorption units could be penetrated by air simultaneously, so that the adsorbents in adsorption space could be used more efficiently.

Field test and CFD modeling for flow characteristics in central cooking exhaust shaft of a high-rise residential building

With the increasement of worldwide population, high-rise buildings of multi-dwelling units have been widely used as a residential building, especially in China, United States and India etc. At present, most of cooking exhaust shafts in high-rise residential building takes the form of central exhaust system. However, the mal-distribution of exhaust flow in central exhaust system often leads to oil fumes reflux and odor migration, which decreasing the performance of kitchen hoods. This study is conducted in a 32-storey residential building which employed central exhaust system. Static pressure and velocity distribution were investigated in central exhaust shaft with uniform cross section. In addition, Computational Fluid Dynamics was adopted to analyze flow characteristics and validated by comparing the simulation results with experimental data. The emphasis of this study lies in the effects of temperature differences and equally spaced operating rates of kitchen hoods on flow characteristics in central exhaust shaft. The results showed that when the temperature difference varies from −12°C to 30°C, the locations of maximum static pressure gradually moved downwards and presented a low-high-low distribution. The maximum occurred in the middle-low storeys under different operating rates. This paper is valuable for HVAC engineers to improve the design of central cooking exhaust shafts in high-rise residential buildings, and solve the mal-distribution problems of exhaust flow in central exhaust systems.

Characterization of pulmonary function in 10–18 year old patients with Duchenne muscular dystrophy

Pulmonary function loss in patients with Duchenne muscular dystrophy (DMD) is progressive and leads to pulmonary insufficiency. The purpose of this study in 10–18 year old patients with DMD is the assessment of the inter-correlation between pulmonary function tests (PFTs), their reliability and the association with the general disease stage measured by the Brooke score. Dynamic PFTs (peak expiratory flow [PEF], forced vital capacity [FVC], forced expiratory volume in one second [FEV1]) and maximum static airway pressures (MIP, MEP) were prospectively collected from 64 DMD patients enrolled in the DELOS trial (ClinicalTrials.gov, number NCT01027884). Baseline PEF percent predicted (PEF%p) was <80% and patients had stopped taking glucocorticoids at least 12 months prior to study start. At baseline PEF%p, FVC%p and FEV1%p correlated well with each other (Spearman's rho: PEF%p–FVC%p: 0.54; PEF%p–FEV1%p: 0.72; FVC%p–FEV1%p: 0.91). MIP%p and MEP%p correlated well with one another (MIP%p–MEP%p: 0.71) but less well with PEF%p (MIP%p–PEF%p: 0.40; MEP%p–PEF%p: 0.41) and slightly better with FVC%p (MIP%p–FVC%p: 0.59; MEP%p–FVC%p: 0.74). The within-subject coefficients of variation (CV) for successive measures were 6.97% for PEF%p, 6.69% for FVC%p and 11.11% for FEV1%p, indicating that these parameters could be more reliably assessed compared to maximum static airway pressures (CV for MIP%p: 18.00%; MEP%p: 15.73%). Yearly rates of PFT decline (placebo group) were larger in dynamic parameters (PEF%p: −8.9% [SD 2.0]; FVC%p: −8.7% [SD 1.1]; FEV1%p: −10.2% [SD 2.0]) than static airway pressures (MIP%p: −4.5 [SD 1.3]; MEP%p: −2.8 [SD 1.1]). A considerable drop in dynamic pulmonary function parameters was associated with loss of upper limb function (transition from Brooke score category 4 to category 5). In conclusion, these findings expand the understanding of the reliability, correlation and evolution of different pulmonary function measures in DMD patients who are in the pulmonary function decline phase.