Chamber Pressure Research Articles

The influence of thermal radiation during microwave-assisted freeze-drying of pharmaceutical unit doses

New drying technologies for biologicals have recently been developed to accelerate the time-consuming batch freeze-drying (BFD) process. Among others, microwave-assisted freeze-drying (MFD) has been suggested as a faster and more effective drying technology. In this study, MFD cycles with the microwave radiation switched on and off were performed to assess the contribution of the microwave radiation to drying acceleration. It was found that thermal radiation emitted by the drying chamber walls was predominantly accelerating the drying of monodose placebos rather than microwave radiation. The combination of ultra-low chamber pressure, high thermal heat transfer and a short primary-to-secondary phase transition reduces drying times by more than 80 % compared to conventional BFD. In a second step, a design of experiment approach was used to assess the effect of thermal radiation versus microwave radiation and their combination, together with dosage properties such as fill volume and excipient concentration upon drying rate. The outcome showed the importance of high fill volume and high excipient concentration for an effective microwave contribution to the drying rate. Nevertheless, the drying acceleration for small pharmaceutical dosages with restricted solutes was mainly driven by thermal radiation rather than 2.45 GHz microwave radiation. The inability of ice to convert microwave energy into heat hampers the potential use of microwave freeze-drying for single-dose vaccines.

Investigation on Thermal Runaway Hazards of Cylindrical and Pouch Lithium-Ion Batteries under Low Pressure of Cruise Altitude for Civil Aircraft

Thermal runaway characteristics and hazards of lithium-ion batteries under low ambient pressure in-flight conditions are studied in a dynamic pressure chamber. The influence of ambient pressures (95 kPa and 20 kPa) and packaging forms (cylindrical and pouch commercial batteries) were especially investigated. The results show that the values of heat release, temperature, and CO2 concentration decrease with the reduction in pressure from 95 kPa to 20 kPa, while the total hydrocarbon and CO increase. Without violent fire, explosion, and huge jet flames, the thermal hazards of TR fire under 20 kPa are lower, but the amount of toxic/flammable gas emissions increases greatly. The amount of CO and hydrocarbons varies inversely with the thermal hazards of fire. Under low-pressure environments of cruise altitude, the thermal hazards of TR fire for pouch cells and the toxic/potentially explosive hazards of gas emissions of cylindrical cells need more attention. The performance of TR hazards for two packaging types of battery is also different. Pouch cells have higher thermal hazards of fire and lower combustible/toxic emitted gases than cylindrical cells. The thermal runaway intensity of individual cells decreases under lower ambient pressure, but the burning intensity increases dramatically when thermal runaway occurs in a battery pack. The open time of a safety valve (rupture of the bag) is shortened, but the trigger time for a thermal runaway varies for different formats of batteries under 20 kPa. Those results may be helpful for the safety warning and hazard protection design of Li batteries under low-pressure conditions.

Vaporization in Liquid-Core Nuclear Thermal Rockets

This work provides an overview of vaporization phenomena in liquid-core nuclear thermal rockets to aid in unifying modeling assumptions by characterizing the impact of vaporization. Historical variations in vapor modeling have led to reported specific impulses ranging from 1000 to 2000s following model refinements in the 1960s and the omission of vaporization consideration post 1990. The only preexisting vapor transport study to not rely on the Reynold’s analogy was performed for the radiator design. This paper performs the first such analysis for the bubbler design, given its renewed interest. Consideration is given to potential centrifugal species separation, proposed fuel mixtures, interplay between chamber pressure and vaporization, impacts on propellant thermoproperties, evaporative cooling, power requirements for vapor separation, and the complexity of hydrocarbon interactions under the proposed chamber conditions. The bubbler design is shown to be well approximated as fully saturated, whereas the radiator and droplet designs may be configured to reduce vaporization to 20% saturation. Characterization of vaporization within liquid cores is essential to early design decisions, such as overall archetype, defining the operating point, and liquid media composition. For a threshold temperature corresponding to around 10% of the propellant being vapor by mass, further increases in temperature begin reducing the specific impulse. Below this threshold temperature, the impact of vaporization on thermal modeling with the chamber is likely negligible. Above this threshold temperature, higher-fidelity thermal modeling will be required, and the work required to separate the vapor begins exceeding 100 kW/(kgH/s). Nozzle kinetics are applied to liquid cores for the first time, showing that specific impulses increase with increasing chamber pressure contrary to historical findings. Historically, modeled uranium-zirconium-carbon mixtures are predicted to reach a specific impulse up to 1260 s. A uranium-tungsten-carbon fuel mixture yielded the best theoretical specific impulse of slightly under 1400 s; however, no nucleonic or thermal analysis has been conducted with this fuel composition.

Analysis of refrigerant/lubricant distribution and operating characteristics of a rotary booster for data center free cooling

A booster-driven loop free cooling system plays a crucial role in enhancing data center energy efficiency and reducing emissions due to the special booster with low pressure ratio as a vital driving component. And the impact of lubricant and its fraction on the booster operation are the key points under low pressure ratio, as well as lubricant distribution. In this paper, the refrigerant/lubricant two-phase mixing flow in the working chamber of a booster was investigated under low pressure ratio for data center free cooling. The volume of fluid (VOF) multiphase flow model combining the working chamber of the rotary booster and discharge valve was built up to analyze the dynamic characteristics of the booster under free cooling conditions. The effect of lubricant fraction and its working frequency on the operating indexes (exhaust temperature/pressure, mass flow rate, volumetric efficiency, indicated specific work, energy efficiency ratio) were studied. The lubricant distribution and its changes for different angles and frequencies were presented. The results indicate that it can improve the thermal performance of the booster effectively with appropriate volume fraction of lubricant. The lubricant in the two-phase flow reduces the inner temperature and pressure in the booster working chamber, which changes the exhaust pressure and volumetric efficiency as well as the cooling capacity. The exhaust pressure and the mass flow rate increase notably for the refrigerant/oil mixture with the increasing lubricant volume fraction, while other performance indexes decrease. The exhaust pressure and the mass flow rate increase by 0.51 % and 47.14 %, separately, when the lubricant volume fraction raises from 0 to 5 % at operating frequency of 50 Hz. Whereas, the exhaust temperature, refrigerant mass flow rate, volumetric efficiency, indicated specific power, cooling capacity and EER decrease by 18.11 %, 4.81 %, 47.14 %, 38.94 %, 4.81 % and 26.36 %, respectively. The investigations can support the lubrication and sealing of the booster with low pressure ratio for free cooling to reach efficient and reliable operation.

Optimization Control Strategies and Evaluation Metrics of Cooling Systems in Data Centers: A Review

In the age of digitalization and big data, cooling systems in data centers are vital for maintaining equipment efficiency and environmental sustainability. Although many studies have focused on the classification and optimization of data center cooling systems, systematic reviews using bibliometric methods are relatively scarce. This review uses bibliometric analysis to explore the classifications, control optimizations, and energy metrics of data center cooling systems, aiming to address research gaps. Using CiteSpace and databases like Scopus, Web of Science, and IEEE, this study maps the field’s historical development and current trends. The findings indicate that, firstly, the classification of cooling systems, optimization strategies, and energy efficiency metrics are the current focal points. Secondly, this review assesses the applicability of air-cooled and liquid-cooled systems in different operational environments, providing practical guidance for selection. Then, for air cooling systems, the review demonstrates that optimizing the design of static pressure chamber baffles has significantly improved airflow uniformity. Finally, the article advocates for expanding the use of artificial intelligence and machine learning to automate data collection and energy efficiency analysis, it also calls for the global standardization of energy efficiency metrics. This study offers new perspectives on the design, operational optimization, and performance evaluation of data center cooling systems.

Experimental study of dam-break-like tsunami loads on vertical structures with overhanging horizontal slabs: Slab with air chamber

Tsunamis pose a significant threat to coastal engineering. A comprehensive physical experiment was conducted to examine the effect of air chambers on vertical structures with overhanging horizontal slabs under tsunami bores. This paper, serving as the second part of the series, contrasts with conditions without air chambers (flat slab as Part I) to underscore the chamber's effects. The experiment employed dam-break waves to simulate tsunamis, and the collected pressure data and experimental images were analyzed. Results show that the chambers restrict water flow, thereby enhancing the impact on the slab. This focusing effect greatly increases both maximum uplift and horizontal pressure (by almost 1.3 times). The uplift pressure rises with increasing chamber volume, while horizontal pressure escalates with greater beam volume. However, both pressures diminish as slab height increases. Water flowing into the chambers disperses air, generating numerous bubbles that accumulate above, forming an air layer that reduces pressure signal fluctuations. This phenomenon of entrained and trapped air is compared and analyzed with existing literature. The maximum pressure of the nearshore air chamber is greater than that of the offshore air chamber by 13% (3.68 kPa vs. 3.27 kPa), while the quasi-steady pressures of the two are almost equal. Differences in pressure between chambers result from the sequence of water flow impacts and reflections. New design envelope equations and conversion coefficients are proposed based on experimental data. The focusing coefficient, considering bore height, slab height, and chamber parameters, is summarized. Novel equations for estimating pressure on a flat slab with specific chambers are proposed, with validation results indicating high accuracy.

Numerical investigation of liquid oxygen filling process in liquid rocket engine by a multi-dimensional co-simulation method

The liquid oxygen filling process in the thermal component downstream of the valve directly affects the starting performance and working reliability of the liquid rocket engine. The filling process is reproduced with a multi-dimensional co-simulation method including one-dimensional system simulation and three-dimensional component simulation, the former provides dynamic flow data for the latter to calculate the filling process. The characteristics of the flow and evaporation and the phenomenon of gaseous oxygen residue are investigated. The results indicate that the simulated pressure value and tendency in the thermal component agree well with the experiment. The flow and evaporation reach a temporary equilibrium due to the flash boiling of the superheated liquid oxygen in the thermal component. The pressure in the combustion chamber downstream of the thermal component plays an important role in breaking the equilibrium and promoting the transition from superheat to supercool state of liquid oxygen. Additionally, the volume proportion of residue gaseous oxygen is 35 % at ignition time, which is far from the ideal state and affects the temperature measurement in the experiment. 26 % of the gaseous oxygen has not been discharged in time, leading to the injection instability in the injection region away from the inlet.

Experimental investigation on cooling characteristic of transpiration-film combined cooling structure using liquid coolant

Transpiration cooling has gained significant attention as a promising strategy for thermal protection in scramjet engines. However, this approach faces limitations due to its susceptible block in fuel gas environment and significant fluctuation when using liquid coolants. To address these challenges, this work proposes a novel transpiration-film combined cooling structure (CCS), where the lower porous layer could ensure sufficient heat transfer and the upper film-hole layer could keep impurities from blocking porous layer and enhance the mechanical strength. Experimental and theoretical investigation on the combined cooling structure with liquid coolant phase change are carried out, and the cooling efficiency, temperature uniformity and cooling chamber pressure of the combined structure are compared with those of the transpiration cooling structure (TCS). Remarkably, the combined structure effectively suppresses temperature fluctuations, reducing the amplitude of temperature variation to just 1/5 of that observed in the transpiration cooling system. Although the combined structure shows a modest 0.026 drop in time-averaged cooling efficiency, it significantly improves temperature uniformity and reduces pressure peaks within the cooling chamber. Furthermore, the flow characteristics of liquid film and vapor film are analyzed and the coolant utilization rate for vapor film is 6.4 times higher than that for liquid film. Consequently, the design of combined structures using liquid coolant holds great promise for achieving highly efficient thermal protection in scramjet engines.

MASS SPECTROMETRIC STUDIES OF HYDROGEN GENERATION UNDER ELECTROLYSIS PROCESS WITH THE USING TUBE CATALITYC ELECTRODES

The work presents some experimental results obtained in the new module construction of an electrolyzer with tube electrodes: mass spectra of the mixtures of gases, generated during electrolysis, volt-ampere characteristics, etc. It has been shown that at electrolytes (H2O + 1 wt.% NaHCO3, H2O + 1 wt.% Na2CO3) temperature of ~ 50 °C and a pressure in the electrolyzer chamber of ~ 2 atm, the generated gas is 92 vol.% consists of hydrogen. Estimations show from two to four times (in dependence on electrolyte composition) higher effectiveness of converting electri-cal energy into the amount of electrolysis gas for new electrolysis setup construction compared to the previous ver-sion.

Measurements of Atmospheric HO2 Radicals Using Br-CIMS with Elimination of Potential Interferences from Ambient Peroxynitric Acid.

As a promising direct measurement method of atmospheric hydroperoxyl radicals (HO2), bromide chemical ionization mass spectrometry (Br-CIMS) has been first demonstrated by Sanchez et al. (Atmos. Meas. Tech. 2016, 9, 3851-3861). However, field application of this method is currently still sparse, and there is still a gap between measured HO2 concentrations and calculated ones derived from the atmospheric equilibrium between HO2 and peroxynitric acid (HO2NO2). In this work, we constructed an improved Br-CIMS with optimizations of custom-built front-end devices, chamber pressures, and instrumental voltages to achieve a 3σ detection limit of 0.5 ppt at an integration time of 60 s and a sensitivity of 1-3 cps ppt-1 under a total reagent ion signal of 0.2 MHz for HO2 detection. HO2NO2, a product from atmospheric reactions between HO2 and NO2, can also be detected by Br-CIMS, whose interference on the HO2 measurement was found but nearly eliminated by regulating key CIMS voltages to minimize the decomposition of (BrHO2NO2)- ions in the MS. In addition, a 2 week field campaign was carried out in urban Shanghai, demonstrating that the interference of HO2 from ambient HO2NO2 was less than 10% of the true HO2 signal under our optimized CIMS voltage setting. Our study suggests that Br-CIMS is a reliable technique for atmospheric HO2 measurements.

Dependence of Pressure Characteristics of Pressurized Pulse Water Jet Chamber on Nozzle Diameter

The nozzle is the key element of the water jet generator for energy conversion. In order to explore the influence of the nozzle diameter on the pressure characteristics of the supercharged pulsed water jet plenum chamber, a supercharged pulsed water jet pressure acquisition system was established, and the equations of motion and theoretical pressurization ratio equations of the supercharged pulsed water jet generator were established. The pressurization chamber pressure acquisition experiments under different nozzle diameters were carried out. The research results show that the pressurized pulsed water jet generator has a critical nozzle diameter of 0.6 mm. When the nozzle diameter is less than the critical diameter, the pressure in the boost chamber is equal to the product of the driving pressure and the boost ratio. As the nozzle changes, there is no significant change in the peak pressure and frequency of the boost chamber. When the nozzle diameter is greater than the critical diameter, there is a non-linear relationship between the boost chamber pressure and the driving pressure. As the nozzle diameter gradually increases, the actual boost ratio gradually decreases, and the peak pressure of the boost chamber further decreases. The nozzle diameter can no longer provide a load for the establishment of fluid pressure in the boost chamber. The results of this research provide a research basis for further controlling the pressure characteristics of the boost pulse water jet.

Detecting and Locating Corona Discharges in Low-Pressure Aircraft Environments Using Optical Sensors

Today, there is a clear trend toward electrification of transportation systems, including aircraft. Due to the enormous power requirements, they must operate at high voltages. However, the combined effect of higher voltage levels and low pressure environments is conducive to the occurrence of electrical discharges in electrical systems. Therefore, there is an urgent need to develop cost-effective systems to detect the discharges in the early stages before major failures can occur. This paper compares two optical sensors for early discharge detection in a simulated aircraft environment. The experimental study is performed in a low pressure chamber using a needle plane electrode. The pressure is changed from that corresponding to ground level to that corresponding to flight altitude, i.e., from 100 kPa to 20 kPa. The effect of the supply frequency is also studied, since modern aircraft operate in a wide range of frequencies up to about 800 Hz. Both variables, especially pressure, have shown significant effects on the CIV value. The results have also shown a similar sensitivity of both sensors for all the experimental conditions analysed, allowing a fast and sensitive detection and localization of incipient electrical discharge activity.

High pressure sensor based on intensity-variation using polymer optical fiber

Silica fiber under high pressure increases the risk of fiber breakage or permanent deformation, which may cause sensor failure due to mechanical strength limitations. High pressure can also induce birefringence in optical fiber. In this study, we present a simple design and low-cost high pressure sensor using polymer optical fiber (POF) based on the intensity-variation technique. A side-coupling mechanism in the sensor structure is adopted, which varies the intensity with applied pressure. Two POFs are twisted together to create a sensing region where the light is launched in the first fiber and measurement is taken from the second fiber. In sensing phenomena, cladding mode frustrated total internal reflection occurs when pressure increases. Silicone gel is used in the pressure chamber for sealing and preventing leakage. The sensor structure is able to detect high pressure in the MPa range, where we tested up to 4 MPa. For higher sensitivity, twisted and bend structure is analyzed, and sensitivity is achieved at about 432.21 nW/MPa. However, twisted helical structure is adopted to enhance sensing range which is about 50 cm. The proposed high-pressure sensor structure is easier to fabricate and has high stability because it doesn’t require any destructive method as compared to other conventional methods.

Impacts of barometric pressure on metabolic rate: A plateau experimental study

Metabolic rate is a fundamental parameter influencing thermal comfort, which further affects the well-being and productivity of the occupants. Here, the impacts of barometric pressure on respiratory parameters, metabolic rate, heart rate, and blood oxygen saturation are studied through pressure chamber experiments. The results indicate that the minute ventilation of the subject rises significantly with declining barometric pressures, and usually, this is accomplished by increasing respiratory depth rather than breathing frequency. When the barometric pressure declines from 72.1 kPa to 66.2 kPa, the metabolic rate of subjects at sitting and 1, 2, 3, and 4 km/h walking activities rises by 4.8 %, 7.2 %, 3.5 %, 2.5 %, and 4.3 %, respectively. As the barometric pressure decreases further to 61.9 kPa, the metabolic rate rises again by 3.0 %, 9.8 %, 6.4 %, 5.0 %, and 2.4 %, respectively. In addition, there is often a risk of overestimation when using the heart rate to estimate the metabolic rate at high altitudes, thus this method should be used cautiously. The results are significant in laying the groundwork for elucidating the relationship between metabolic rate and barometric pressure. Further, it is essential for the establishment of thermal comfort standards at high altitudes.

Calculation of foam injection ratio and regulation method of muck compressibility under shield soil chamber pressure conditions

The proper compressibility of shield muck is crucial for ensuring the safety and efficiency of shield tunneling. Foam conditioning is an effective method for improving the compressibility of muck. However, the amount of foam injected in practical construction is mostly based on experience or subjective judgment. A novel foam injection ratio calculation formula was derived based on Boyle’s law and the pore pressure calculation model. This formula comprehensively considers the impact of chamber pressure, pore water, soil gradation, and existing muck conditioning parameters on foam consumption. Starting with the premise that pore foam lifts the soil skeleton, reducing the effective stress in the soil to zero, a method for regulating the compressibility of muck in shield tunnel construction sites was proposed. This method presents the advantage of accurately quantifying the amount of foam injection. Verification results from field applications confirm that optimizing the muck conditioning parameters through this new method leads to improvements in workability, permeability, and muck compressibility, meeting the requirements for efficient shield tunneling. The fluctuation of chamber pressure is reduced, lowering the risk of tool wear. Additionally, there is a reduction of 29.96 % in average total thrust and 29.82 % in cutterhead torque, with a corresponding increase in tunneling speed by 24.42 %. Furthermore, the advantages and limitations of the proposed method were discussed.

Numerical simulations and an experimental study for optimal design of a 1500 [formula omitted] water-tube condensing boiler

The present study is focused on investigating the condensation process and numerical simulation for optimal design of a 1500 kW water-tube condensing boiler. The specific geometry of the heat exchanger of this boiler involves compact arrangement of spiral coils to enhance heat transfer efficiency and achieve high capacity. Experimental validation is conducted on a 580 kW condensing boiler. Numerical simulations of the flow for gas and water sides of the boiler are performed in parallel using the ANSYS-FLUENT software with the k-omega (SST) turbulence model. Twelve models with different combustion chamber dimensions, coil numbers and revolutions are considered. Important design criteria include flue gas temperature, combustion chamber pressure and water pressure drop in the coils. The results indicate that increasing effective heating surface area and reducing coils gap decrease flue gas temperature to the dew point. Increasing coil revolutions has a greater impact on flue gas temperature and boiler weight compared to increasing coil numbers. With the same number of coils, by adding an extra revolution the weight is increased approximately 17 % and the effective heating surface area about 21 %. On the other hand, for the same number of revolutions, each additional spiral coil increases both of the weight and the effective heating surface area approximately 4 %. Moreover, with an increase in the number of the coils and a decrease in the number of revolutions, the pressure within the combustion chamber is decreased. By reducing the gap size, the flue gas temperature is reduced approximately 2 °C and the combustion chamber pressure is increased about 18 %. Base on the design criteria, the model six with 27 spiral coils and 7–8 revolutions, is identified as the optimal design. This progress and capability allows the design and manufacture of high-capacity boilers for residential sector as well as for industrial applications.

Fast permeability measurement for tight reservoir cores using only initial data of the one chamber pressure pulse decay test

In this study, a mathematical model for fast determination of the permeabilities of tight rocks using measurements taken from the initial period of the One Chamber Pressure Pulse Decay (OC-PPD) test is presented. The model applies to measurements taken both before and after the pressure pulse front has reached the downstream end of the specimen. The analytical solutions for the pressure decay in the upstream chamber are derived based on a parabolic arc approximation of pore pressure distribution along the test specimen. This approximation allows converting the initial–boundary value problem of fluid diffusion in the specimen, governed by partial differential equations, to a system of ordinary differential equations that can be easily solved by explicit formulae. Thus, an explicit formula for the pressure decay rate is obtained, which enables inverse analysis of the initial experimental data to estimate the rock permeability. The proposed method expedites the pulse decay test as it does not require the system to reach equilibrium. The method is validated with three sets of experimental data of the OC-PPD test using helium as the diffusing fluid, for which the relative error of the permeability is found to be less than 6%. This method is particularly useful if the equilibrium time of the pulse decay test for rock specimens with permeabilities in the range of nano-Darcy takes hours or days.

Load history dependency of stiffness properties of PTFE-coated glass fibre membranes

The aim of this contribution is to investigate whether the order of load ratios applied to a textile structure impacts the biaxial stiffness behaviour of the structural textile itself. These investigations are performed based on biaxial tests on an architectural woven glass fibre fabric, a representative of such membranes. The first part of the paper investigates the existence and extent of load history dependency in the material response. Biaxial test results show that effects of a previous load history on the weave geometry cannot be eliminated by further load cycling in all biaxial stress ratios. Moderate to strong effects are recognized in two stress ratios, although not in both weave directions.The second part of the paper examines how these effects influence material stiffness parameters and structural calculations. Two boundary value problems are investigated: a pressure chamber test and a roof structure. Parameters obtained by fitting biaxial tests with or without history are considered. By incorporating an adaptive load-ratio dependent scheme, highly predictive numerical results are obtained, showing that while the effect of load history may appear small in the biaxial tests and pressure chamber test, it can be significant in complex structural problems like roof structures.

A comparative study of the effect of cavity and obstacle on premixed methane–air flame evolution

To compare the effect of the cavity and obstacle on the flame evolution, a series of experimental studies are carried out to investigate the premixed methane-air flame propagation in the combustion chamber featured by cavity or obstacle. The flame behavior is obtained by analyzing the flame-front dynamics and pressure variation. The flame stretches into an inclined shape due to the flow contraction with the presence of an obstacle. In contrast, the flame forms a vortex by following the unburned gas vortex owing to the flow expansion in a cavity. Furthermore, the flame downstream of the obstacle is more turbulent than in cavity cases. Moreover, the flow contraction caused by obstacles also contributes to a higher flame-tip velocity than cavity cases. When the change in cross-section caused by obstacle and cavity is equivalent, the maximum pressure in the combustion chamber with an obstacle is generally larger than that in cavity cases ascribed to the combined effect of the changes in fuel amount and heat loss. In addition, the maximum rate of pressure rise in the combustion chamber featured by the obstacle is larger than that in the combustion chamber featured by a cavity, corresponding to the highly turbulent flame downstream of the obstacle.

Blocking Air in the Filtering Bleb: Effects on Graft Adhesion After Descemet's Stripping Automated Endothelial Keratoplasty.

To evaluate the outcome of Descemet's stripping automated endothelial keratoplasty (DSAEK) with "blocking air" in the filtering bleb in patients with previous trabeculectomy. In total, 299 eyes in 283 patients who underwent DSAEK were retrospectively reviewed. Endothelial graft adhesion, intraocular pressure (IOP), and air volume in the anterior chamber with (group A) or without (group B) a filtering bleb were compared between the groups. Group A was divided into two subgroups according to the presence (group A1) or absence (group A2) of air in the filtering bleb; the same three factors were compared between the subgroups. The graft detachment rate was significantly higher in group A (14.3%) than in group B (6.5%) (p = 0.04). IOP was significantly lower in group A than in group B before surgery (p = 0.01), at the end of surgery (p = 0.04), at three hours (p < 0.001), and one week postoperatively (p = 0.02). The graft detachment rate did not significantly differ between groups A1 and A2. There were no differences in IOP at each follow-up time, whereas there was a statistically significant increase in IOP from the preoperative measurement to the end of surgery in group A1 (21.0±7.0 mmHg) compared with group A2 (14.2±8.6 mmHg) (p = 0.02). The presence of blocking air in the filtering bleb helps ensure increased IOP during the early postoperative period but had no significant effect on graft detachment rates.