Cavity Air Research Articles

Detailed Study of Cavity Features and Air Entrainment Due to the Initial Impact of Plunging Jet Flows

Detailed Study of Cavity Features and Air Entrainment Due to the Initial Impact of Plunging Jet Flows

Numerical study using the finite volume method on the thermal and energy performance of a regulated underfloor heating system incorporating PCM in a ventilated room

A physical model is performed to assess the thermal and energetic advantages of using PCM in controlling and regulating the indoor temperature of a ventilated room with an underfloor heating system incorporating a PCM. The heating source is regulated to keep the cavity air temperature in a small interval assuring a certain level of comfort without wasting too much energy. By contrasting our numerical results with numerical data from the literature, the suggested model was validated. Physical processes are solved numerically using computational fluid dynamics by a detailed 2D transient simulation integrating real climatic data of Agadir, Tangier and Casablanca. The simulations carried out justified the suitability of using the PCM with Agadir and Casablanca climate types by a saving of heating power reaching 18.80 % and 17.33 %, respectively.

Development of mathematical correlations to predict performance of forced ventilated Photovoltaic-DSF system in hot composite climate

Performance of Photovoltaic-double skin façade (Photovoltaic-DSF) system in summer has been critical. Owing to high solar ingress, cooling requirement of a building significantly increases. Photovoltaic-DSF system provides a shield and controls the heat gain through fenestration in the interior spaces. In the present article, mathematical correlations are developed to analyse energy behaviour of forced-ventilated Photovoltaic-DSF system in India’s hot summer zone, that is, Jaipur. The Photovoltaic-DSF system has been installed and monitored for Jaipur’s summer months (May to July). L25 Orthogonal array of design parameters (air cavity thickness, air velocity and PV panel’s transparency) and their respective levels have been developed using Taguchi design to perform experiments. Based on experimental results, multiple linear regression has been used to forecast solar heat gain coefficient, PVs electrical power and daylighting illuminance indoors as function of design factors. The statistical significance of mathematical relationships is supported by variance analysis, which is found to be in good accord with field measurements ( R2 > 0.90). The proposed correlations are pragmatic in designing Photovoltaic-DSF systems for hot summer conditions. The Photovoltaic-DSF system with 30% transmittance and air velocity of 5 m/s in 200 mm air cavity thickness achieved maximum energy performance in hot summers.

Effects of decongestion on nasal cavity air conditioning efficiency: a CFD cohort study

Decongestion reduces blood flow in the nasal turbinates, enlarging the airway lumen. Although the enlarged airspace reduces the trans-nasal inspiratory pressure drop, symptoms of nasal obstruction may relate to nasal cavity air-conditioning. Thus, it is necessary to quantify the efficiency of nasal cavity conditioning of the inhaled air. This study quantifies both overall and regional nasal air-conditioning in a cohort of 10 healthy subjects using computational fluid dynamics simulations before and after nasal decongestion. The 3D virtual geometry model was segmented from magnetic resonance images (MRI). Each subject was under two MRI acquisitions before and after the decongestion condition. The effects of decongestion on nasal cavity air conditioning efficiency were modelled at two inspiratory flowrates: 15 and 30 L min−1 to represent restful and light exercise conditions. Results show inhaled air was both heated and humidified up to 90% of alveolar conditions at the posterior septum. The air-conditioning efficiency of the nasal cavity remained nearly constant between nostril and posterior septum but dropped significantly after posterior septum. In summary, nasal cavity decongestion not only reduces inhaled air added heat by 23% and added moisture content by 19%, but also reduces the air-conditioning efficiency by 35% on average.

A Case of Middle Ear Adenomatous Neuroendocrine Tumors: Proposal of a Staging System

A 49-year-old man visited a local otolaryngology clinic with left hearing loss. He was diagnosed as left middle ear tumor and referred to us. The tumor was protruding from the left tympanic membrane. Computed tomography (CT) revealed thickening of the tympanic membrane, space-occupying lesions in the middle ear cavity and mastoid air cells, and no bone destruction in the left middle ear. Magnetic resonance imaging confirmed the CT findings, and the lesions were hyperintense on T1- and T2-weighted imaging. He was diagnosed as middle ear adenomatous neuroendocrine tumor (MEANT) with a pathological result. The patient underwent postauricular approach and canal wall-down mastoidectomy. The tumor occupied the mastoid air cells and extended into the middle ear mucosa. To prevent perilymphatic fistula, the tumor was excised as extensively as possible, while preserving the tumor around and adjacent to the stapes footplate. MEANT is extremely rare and long-term follow-up is necessary due to be potential for tumor regrowth or recurrence. Herein, we propose a new staging system for MEANT.

Анализ результатов витрэктомии с эндотампонадой витреальной полости воздухом, ПФОС и эндолазерной коагуляцией ретинальных разрывов в хирургии отслойки сетчатки

The results of rhegmatogenous retinal detachment (RRD) surgery in 233 patients (233 eyes) without silicone oil application were analyzed. The first group included 76 patients (76 eyes) after vitrectomy with vitreous cavity air endotamponade and retinal tears endolasercoagulation. The second group consisted of 157 patients (157 eyes) after vitrectomy with vitreous cavity perfluorocarbon liquid (PFCL) endotamponade, endolasercoagulation of retinal tears followed by PFCL removal or replacement with air. Results. Similar comparable results were received postoperatively. Conclusion. Vitrectomy with vitreous cavity air endotamponade allows to perform effective surgical treatment of subtotal retinal detachment in case of upper retinal tears localization, and PFCL tamponade – in case of both upper and lower retinal tears localization with subsequent endolaser coagulation, and also to exclude cases with secondary glaucoma development. Keywords: rhegmatogenous retinal detachment, vitrectomy, air tamponade, PFCL.

How far does feedback on oral malodor assessment influence the decision to quit smoking?

A retrospective, uncontrolled, questionnaire-based, pre-post study involving adult male smoker volunteers who were invited to attend a one-day smoking cessation event at their workplace. To assess the effect of feedback on motivation for smoking cessation using oral-malodor measurements. At baseline, the participants attended a brief video presentation regarding various oral health-specific effects of smoking, joined a group introduction to smoking-cessation aids, and were given questionnaires that inquired information about smoking status including type, daily consumption, and duration. Subsequently, respiratory function and oral-malodor assessment were conducted using exhaled and oral cavity air, respectively. To measure oral-malodor, hydrogen sulfide, methyl mercaptan, and dimethyl sulfide concentrations were determined. Participants' intention for smoking cessation was evaluated through questionnaire before and after the event, classifying their intentions as aiming to quit within the next month, within the next 6 months, or having no intention to quit smoking. Immediate feedback on respiratory function and oral malodor measurements was provided by medical and dental blinded examiners, respectively. A total of 241 men, aged 20-54 years, were enrolled and included:169 (70.1%) exclusive cigarette smokers, 39 (16.2%) exclusive heated-tobacco product users, and 33 (13.7%) users of both. Prior to the health event, 8.7%, 17.0%, and 74.3% of smokers expressed intentions to quit within the next month, the next 6 months, or had no intention to quit, respectively. After the event, the corresponding percentages shifted to 17.8%, 26.6%, and 55.6%. In multivariable logistic regression analysis, the association with intention to quit in the next month was significant only for methyl mercaptan concentration in oral cavity air, with an adjusted odds ratio (AOR) of 4.24 (95% CI: 1.52-11.84; p = 0.006). Sensitivity analysis revealed that this association was concentration-dependent. On the other hand, higher daily tobacco consumption (≥ 15 pieces) was significantly associated with less likely intention to quit in the next 6 months (AOR = 0.37; 95% CI: 0.15-0.92, p = 0.032). Feedback on oral malodor measurement may support the motivation of men to quit smoking within the next month, rather than waiting for the next 6 months.

Experimental investigation on the operation performance of photovoltaic double skin façade in winter

Photovoltaic double skin façade (PV-DSF) offers a versatile solution to address the escalating energy demands of buildings by combining power generation and indoor air temperature adjustment functionalities. Most prior research concentrated on its summer performance, while the winter season receives less attention. This paper concentrates on its operation performance in winter, to provide an experimental framework for its efficient operation. In this regard, the performance of internal circle and thermal buffer mode (both are possible operation modes in winter) were compared via control variable experiments, and the feasibility of mechanical ventilation is also examined regarding the trade-off between the energy consumption of fans and additional energy benefit. These experiments were performed in the full-size experiment rig at Harbin, China, a city with severe cold climate. The experiment results conclusively demonstrate that the internal circle mode can outperform the thermal buffer mode on a cold, sunny day by 10.9%, and the total energy-saving potential can be further increased by 12.6% if fans are activated to enhance cavity airflow. While the experimental data during partly cloudy emphasizes the significance of a suitable operation schedule and shows that PV-DSF can only be switched to internal circle mode when cavity air is fully heated.

Oral-malodor measurement and intention to quit smoking in men: A before-after study.

Few studies have examined the effect of feedback based on oral-malodor measurements on the motivation to quit smoking. Therefore, this study examined whether oral-malodor measurements were associated with the intention to quit smoking. This retrospective, uncontrolled before-after study invited smokers to a workplace health event in 2019 and 2020 to motivate them to quit smoking. They attended seminars on oral health and smoking cessation aids, and then underwent respiratory function and oral-malodor measurements using exhaled and oral cavity air, respectively. Intention to quit smoking was evaluated by answers to questions regarding the intention to quit in the next 1 or 6 months in questionnaires collected before and after the event. This study analyzed 241 men aged 20-54 years (mean: 33.2 ± 10.5) to examine factors associated with the intention to quit in multivariable logistic regression analyses for age, tobacco type (cigarettes and heated-tobacco products), and category of tobacco consumption. Before the event, 8.7%, 17.0%, and 74.3% of smokers had intended to quit in the next month, the next six months, or had no intention to quit, respectively. After the event, the respective percentages were 17.8%, 26.6%, and 55.6%. A higher methyl mercaptan concentration, a volatile sulfide component of oral malodor, was significantly associated with the intention to quit in the next month (adjusted odds ratio, AOR=4.24; 95% CI: 1.52-11.8, p=0.006). The participants with higher daily tobacco consumption were less likely to acquire the intention to quit in the next six months (AOR=0.37; 95% CI: 0.15-0.92, p=0.032). Other variables, such as lung age deficit, exhaled CO concentration, and hydrogen sulfide concentration (another component of oral malodor), were not significantly associated. Oral-malodor measurement feedback may help motivate men to quit smoking in the next 1 month rather than in the next six months.

Otogenic Cerebral Sinus Thrombosis in Children: A Narrative Review.

Cerebral venous thrombosis (CVT) is a rare entity that remains a diagnostic challenge due to various clinical manifestations and a wide variety of causative agents. Local infections, such as acute (AOM) or chronic otitis media, can play a role in the pathogenesis of CVT. The proximity of the tympanic cavity and temporal bone air cells to the dural venous sinuses predisposes them to secondary thrombosis. The release of inflammatory cytokines and activation of the coagulation pathway in the middle ear space in response to infection may trigger the thrombotic mechanism in venous sinuses of the central nervous system. There is no consensus in the literature concerning the treatment of otogenic cerebral venous sinus thrombosis (CVST). Both the extent of the surgery and the use of anticoagulants are disputable. The aim of the study was to provide a thorough analysis of the literature concerning CVST in patients with AOM and acute mastoiditis (AM). The current surgical and conventional treatment strategies are presented. Special attention has been attached to the predisposing factors, the extent of the surgery, and the role of anticoagulants in the treatment of septic otogenic CVST.

Energy characterization of forced ventilated Photovoltaic-DSF system in hot summer of composite climate

Performance of Photovoltaic-double skin façade (Photovoltaic-DSF) system in summer has been critical. Owing to high solar ingress, cooling requirement of a building significantly increases. Photovoltaic-DSF system provides a shield and controls the heat gain through fenestration in the interior spaces. In the present article, mathematical correlations are developed for energy characterization of forced-ventilated Photovoltaic-DSF system in India's hot summer zone i.e. Jaipur. The Photovoltaic-DSF system has been installed and monitored for Jaipur's summer months (May to July). L25 Orthogonal array of design parameters (air cavity thickness, air velocity, and PV panel's transparency) and their respective levels have been developed using Taguchi design to perform experiments. Based on experimental results, multiple linear regression has been used to forecast solar heat gain coefficient, PVs electrical power and daylighting illuminance indoors as function of design factors. The statistical significance of mathematical relationships is sorted by variance analysis, which is found to be in good accord with field measurements (R2 > 0.90). The proposed correlations are pragmatic in designing Photovoltaic-DSF systems for hot summer conditions. The Photovoltaic-DSF system with 30% transmittance and air velocity of 5 metres per second in 200 mm air cavity thickness achieved maximum energy performance in hot summers.

Temperature variations in caves induced by atmospheric pressure variations—Part 1: Transfer functions and their interpretation

According to thermodynamics, atmospheric pressure variations (APV) cause temperature variations in air. However, such variations are difficult to observe, except in thermally stable environments such as underground cavities. We have studied the properties of these temperature variations in four natural caves in France, where continuous time-series have been collected since 1998: Esparros, Aven d'Orgnac, Pech Merle and Chauvet-Pont d'Arc Caves, the last two containing unique prehistoric wall paintings. The pressure to air temperature transfer function (TF), evaluated from 8 × 10-7 to 8 × 10-4 Hz, strongly depends on frequency; its modulus, at the barometric tide S2 (12 h), varies from 2 to 14 × 10-3°C/hPa. While the TFs show pluriannual stability, seasonal variations are observed when sufficiently long data sets are available. Rock surface temperature is also affected by APV and we extract the air to rock surface temperature TF at Esparros, Chauvet and Pech Merle Caves. The observed TFs are accounted for by an improved analytical model including gas adiabatic compressibility, heat exchange with the rock, heat diffusion in the rock, phase changes of water at the rock surface and an advective term due to barometric pumping motion in the air volume. This model has three free parameters: the effective rock surface to air volume ratio, the time constant of heat exchanges and the effective adiabatic coefficient of cavity air. It is sufficient to account for the various situations observed in natural caves. Using this model, the observed TFs can be interpreted; they reflect the type of thermodynamics active at a given location, in particular the presence of barometric winds, but the actual values of parameters remain difficult to predict. Thus, temperature variations induced by APV emerge as a fundamental tool to characterize underground environments, relevant in some cases for cave heritage preservation, illustrating the coupled processes active in the Critical Zone.

Thermal performance assessment of opaque ventilated façades for residential buildings in hot humid climates

In this paper, the thermal performance of opaque ventilated façades (OVFs) in the Mediterranean climate zone, where passive cooling is a priority, was examined using computational fluid dynamics (CFD). Simulations were carried out to analyse the behaviour of OVF components under different geometric configurations, using weather data for three cities in Turkey that reflect the climatic conditions of a first-degree day region. These data include the air cavity thickness, outlet size, and air cavity height. Unlike in previous literature, two-way outlet ventilation is employed in this study in the analysis of different façade systems for the Mediterranean climate region, and its performance in reducing solar gain is determined. According to the samples examined within the scope of the criteria outlined herein, it was determined that the rate of heat transferred indoors through the façade can be reduced within the range of 69 % to 75 %.

Cooling capacity evaluation of thermally activated light shelf (TALS) systems

A light shelf is typically used to improve the lighting environment by preventing glares and increasing illuminance in interior zones. If its surfaces can be utilized as cooling surfaces it can also be used to control the thermal environment, particularly in perimeter zones. In this study, the concept of a thermally activated light shelf (TALS), wherein a chilled water pipe is embedded in a light shelf, was proposed, and its cooling capacity was experimentally evaluated. As the upper and lower surfaces are exposed to indoor air and cooling loads, which are different from those of conventional radiant cooling panels, a mock-up test chamber was developed to represent the cooling load applied to both the upper and lower surfaces of the TALS. Mock-up experiments were conducted to evaluate the cooling capacity of the TALS alternatives: TALS with thermal insulation (INS case), cavity air (AIR case), and DC fans (FAN case). Compared with the baseline (INS case), the cooling capacities of the AIR and FAN cases were enhanced by 9.4–29.4% and 22.7–53.1%, respectively, because both the upper and lower surfaces could be utilized as cooling surfaces. Based on the experimental results, cooling capacity curves were derived to provide generalized cooling capacity data considering various cooling load conditions, operating conditions (e.g., chilled water temperature and room air temperature), and layer configurations of the TALS.

Evaluation of BMI-based tube voltage selection in CT colonography: A prospective comparison of low kV versus routine 120kV protocol.

To explore the value of individualized kVp selection based on the patient's body mass index (BMI, kg/m2 ) in CT colonography (CTC). Seventy-eight patients underwent two CTC scans: conventional 120kVp in supine position (Group A) with 30% Adaptive statistical iteration algorithm (ASIR-V) and BMI-based lower kV p in prone position (Group B): tube voltage was suggested by an experienced investigator according to the patient's body mass index (BMI; calculated as weight divided by height squared; kg/m (2)).70kV for BMI<23kg/m2 (Group B1, n=27), 80kV for 23≤BMI≤25kg/m2 (Group B2, n=21) and 100kV for BMI>25kg/m2 (Group B3, n=30). Group A, corresponding to the BMI value in Group B, was divided into A1, A2, and A3 subgroups for analysis. Groups B used ASIR-V of different weights (30%-90% ASIR-V). The Hounsfield Unit (HU) and SD values of the muscles and the intestinal cavity air were measured, and the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) of images were calculated. Imaging quality was evaluated by two reviewers and statistically compared. The 120kV scans were preferred more than 50% of the time. All images had excellent quality with good consistency between reviewers (Kappa>0.75, p<0.05). The radiation dose was reduced in groups B1, B2 and B3 by 63.62%, 44.63%, and 32.14%, respectively, compared with group A (p<0.05). The SNR and CNR values between group A1/A2/A3 and B1/B2/B3+60%ASIR-V were not statistically significant (p<0.05). There was no statistically significant difference between the subjective scores of group B combined with 60%ASIR-V and group A (p>0.05). BMI-based individualized kV CTC imaging significantly reduces overall radiation dose while providing an equal image quality with the conventional 120kV.

Combustion and emission performance of a trapped-vortex gas turbine combustor fueled by RP-3 kerosene

In this study, a trapped-vortex gas-turbine combustor was designed and investigated to simultaneously achieve robust stability, low pollutant emissions, and the desired temperature distribution within a short flame length. In the combustor, a trapped-vortex combustion is established using two separated cavities. A swirler was adopted in the mainstream to improve mixing between the hot products of the cavity and mainstream air. Experimental tests conducted under atmospheric pressure indicate that the combustor can achieve encouraging performance in terms of flame stability, pollutant emissions, outlet temperature profiles, and flame length. Improvements of 19.2% and 23.3% were achieved by the lean ignition and blowout performances, respectively, as the combustor inlet temperature increased from 373 K to 473 K. As the fuel equivalence ratio increased from 0.25 to 0.55, the NOx emissions increased slightly, whereas the CO emissions first decreased and then increased slightly. Furthermore, two separated short flames with uniform outlet temperature profiles were obtained using the combustor. Interestingly, an “M” pattern temperature profile is obtained corresponding to the swirler center plane as compared to the parabola form outlet temperature profile corresponding to the 20-mm left side of the swirler center plane.

Temperature-induced inconsistency in the pressure sensitivity of polymer-diaphragm-based FP pressure sensors

Fiber optic Fabry-Perot Interferometer benefits many requirements in pressure sensing. The variation of pressure sensitivity of the polymer-diaphragm-based Fabry-Perot pressure sensor with temperature is studied by investigating the thermal effect of the cavity air and the diaphragm separately. FP cavity vacuum treatment and multi-curvature diaphragm simulation and experimental studies are conducted. Experimental results show that the sensor pressure sensitivity decreases with increasing temperature by 0.46nm/(kPa·°C). The diaphragm’s thermal effect is the leading cause of temperature-induced inconsistency in pressure sensitivity, accounting for 0.43nm/(kPa·°C).

Experimental Assessment of the Thermal Influence of a Continuous Living Wall in a Subtropical Climate in Brazil

A continuous living wall is a vertical garden that allows the cultivation of a wide variety of species on vertical surfaces, consisting of a sequence of layers that shade and add thermal resistance to the external façades of buildings. Thus, the living wall can be an alternative to increase the thermal efficiency of the building and reduce the use of air conditioning for cooling the indoor environment. This work experimentally investigated the thermal influence of a continuous living wall on the surface temperatures of an east façade in a subtropical climate with hot summers (Cfa), during the summer period. The experiment included the implementation of a real living wall in a seasonally used building and the delimitation of two sample plots (i.e., protected and bare wall). Campaigns were carried out to measure the external and internal surface temperatures of the protected plot, the living wall, and the bare wall, as well as the cavity air temperature, from 08:00 to 17:45, at 15-min intervals. The results show the efficiency of the living wall in reducing the external (up to 10.6 °C) and internal (up to 2.9 °C) surface temperatures of the protected plot compared to the bare wall, along with a reduction in thermal variation (average reduction of 6.5 °C externally and 3.6 °C internally) and an increase in thermal delay (up to 6 h for external and 1 h for internal), in addition to a reduction in temperature and greater thermal stability of the cavity between the garden and the protected land in comparison to the external space.

Could tympanometric volume be a useful tool to predict the success of type I tympanoplasty in simple chronic otitis media

Background: Middle ear aeration level is an important precursor of chronic otitis media (COM) and one predictive factor for tympanoplasty success. Tympanometry measures the volume of the external ear canal, middle ear cavity, aditus, and mastoid air cells in patients with tympanic membrane (TM) perforation. The aim of the study was to determine whether the pre-operative tympanometric volume and the interaural tympanometric volume differences in unilateral simple COM can predict the success of type I tympanoplasty. Methods: Retrospective analysis of type I tympanoplasties performed in adults between January 2017 and December 2020 in a tertiary hospital. Bilateral COM, revision surgery and tympanoplasty using cartilage grafts or associated with other procedures were excluded. Success was defined as no evidence of TM perforation on otoscopic examination and tympanogram, at least six months after surgery. Results: Sixty-one patients were evaluated. The mean age was 43 years old, and there was a female predominance (55.7%). The overall success rate was 77%. Location or size of perforation weren’t different among patients with and without surgical success. We found a statistically significant result (p=0.009) regarding interaural tympanometric volume differences, with a median of 2.7 ml (IQR 3.6) in the surgical success group and a median of 1.3 ml (IQR 1.26) in the recurrence group. 90.6% of patients with interaural tympanometric volume difference greater than 2 ml had successful surgery. Conclusions: A good aeration of middle ear, demonstrated by higher interaural tympanometric volume differences, can predict success of type I tympanoplasty.

Modelling double skin façades (DSFs) in whole-building energy simulation tools: Validation and inter-software comparison of naturally ventilated single-story DSFs

Building energy simulation (BES) tools offer the possibility to integrate double skin façade (DSF) technologies into whole building simulation through dedicated modules or possible workarounds. However, the reliability of such tools in predicting the dynamic heat and mass transfer processes within the DSFs is still to be determined. Therefore, this paper aims to assess the performance of four popular BES tools (i.e. EnergyPlus, TRNSYS, IDA-ICE and IES-VE) in predicting the thermal behaviour of one-storey naturally ventilated DSF in three different ventilation modes. To evaluate their capability to predict thermophysical quantities, we compared the simulation results with experimental data. The results show that it is not possible to identify a tool that outperforms the others for all the analysed quantities, especially for the cavity air temperature, which is the least accurate parameter in all software due to underestimation of the daytime peak. IES-VE seems to be most accurate for Supply Air and Thermal Buffer modes when shading is deployed, while EnergyPlus appears most accurate for Outdoor Air Curtain mode. When it comes to surface temperatures and transmitted solar radiation, TRNSYS appears to be the best-performing software. In addition, this study investigated the challenges that designers may face when modelling a naturally ventilated DSF using whole-building simulation tools. Moreover, the investigation elucidates the challenges that have a more significant effect on the performance of the BES tools in order to reinforce their reliability.